The Role of Nitric Oxide in Type 2 Diabetes 9789815079814, 9789815079821, 9789815079838, 9815079816

Table of contents :
Title
Copyright
License
Contents
Foreword
Preface
REFERENCES
List of Contributors
Pathophysiology of Type 2 Diabetes: A General Overview of Glucose and Insulin Homeostasis
Asghar Ghasemi1,* and Khosrow Kashfi2
INTRODUCTION
EPIDEMIOLOGY OF DIABETES
Diagnosis of Diabetes
Glucose Homeostasis
Post-Absorptive State: The Fasting State
Glucose Production
Glucose Utilization
Post-Prandial State
Mechanisms Underlying Glucose Homeostasis
Central Mechanisms of Glucose Homeostasis
Glucose Sensing by Neurons
Peripheral Mechanisms of Glucose Homeostasis
INSULIN
Insulin Secretion
Mechanism of Insulin Secretion
Box 1 Circulating Insulin Concentrations
Box 2 Technical Considerations on Circulating Insulin Measurement
Insulin Signaling Pathways
Pathophysiology of Type 2 Diabetes
Insulin Resistance
β-cell Dysfunction
CONCLUDING REMARKS
CONSENT FOR PUBLICATION
CONFLICT OF INTEREST
ACKNOWLEDGEMENT
REFERENCES
Nitric oxide: A Brief History of Discovery and Timeline of its Research
Asghar Ghasemi1,* and Khosrow Kashfi2
INTRODUCTION
HISTORY OF NO FIELD
Diabetes-Related No Research
CONCLUDING REMARKS
CONSENT FOR PUBLICATION
CONFLICT OF INTEREST
ACKNOWLEDGEMENT
REFERENCES
Impaired Nitric Oxide Metabolism in Type 2 Diabetes: At a Glance
Zahra Bahadoran1, Mattias Carlström2, Parvin Mirmiran3 and Asghar Ghasemi4,*
INTRODUCTION
ROLE OF NO IN GLUCOSE AND INSULIN HOMEOSTASIS
T2D AND WHOLE-BODY NO METABOLISM
NO DEFICIENCY IN T2D
T2D and Circulating NO: an Epidemiologic Point of View
Underlying Mechanisms of Impaired NO Metabolism/Action in T2D
Impaired L-Arginine NOS-NO Pathway
Impaired NO3-NO2-NO Pathway
Impaired NO Transport
Impaired NO Signaling
CONCLUDING REMARKS
CONFLICT OF INTEREST
ACKNOWLEDGEMENT
CONSENT OF PUBLICATION
REFERENCES
Asymmetrical Dimethyl Arginine, Nitric Oxide, and Type 2 Diabetes
Zahra Bahadoran1, Mattias Carlström2, Parvin Mirmiran3 and Asghar Ghasemi4,*
INTRODUCTION
ADMA BIOSYNTHESIS AND METABOLISM
Adma and Regulation of No Synthesis
Cellular Uptake of ADMA
Inhibitory Effects of ADMA on NOS Expression and Activity
Adma and T2d
DDAH and T2D: Lessons from Genetic Studies
Plasma and Tissue Concentrations of ADMA in T2D
Plasma ADMA Levels and Risk of Diabetic Complications
Other Methylarginines and T2d
Pharmaceutical Interventions for Elevated Adma
CONCLUDING REMARKS
CONFLICT OF INTEREST
ACKNOWLEDGEMENT
CONSENT OF PUBLICATION
REFERENCES
Nitric Oxide-Related Oral Microbiota Dysbiosis in Type 2 Diabetes
Zahra Bahadoran1, Pedro González-Muniesa2,3,4,5, Parvin Mirmiran1,6 and Asghar Ghasemi7
INTRODUCTION
AN OVERVIEW OF ORAL MICROBIOTA
Oral Nitrate-Reducing Bacteria
Oral Nitrate Reduction and Nitric Oxide Homeostasis
Changes in Oral Microbiota in T2d
Mechanisms Linking Oral Dysbiosis with Impaired Glucose and Insulin Homeostasis
Oral Nitrate-Reducing Bacteria and Nitric Oxide Metabolism in T2d
CONCLUDING REMARKS
CONSENT FOR PUBLICATION
CONFLICT OF INTEREST
ACKNOWLEDGEMENTS
REFERENCES
Nitric Oxide and Type 2 Diabetes: Lessons from Genetic Studies
Zahra Bahadoran1, Parvin Mirmiran2, Mattias Carlström3 and Asghar Ghasemi4,*
INTRODUCTION
A BRIEF OVERVIEW OF NOS ENZYMES: GENE STRUCTURE AND CHROMOSOMAL LOCALIZATION
Genetically-Modified Nos Enzymes and Impaired Glucose and Insulin Homeostasis
Common Polymorphisms of Nos Enzymes
Common Polymorphisms of nNOS and iNOS
Common Polymorphisms of eNOS
The eNOS Polymorphisms and Serum NO Metabolites
The Enos Polymorphisms and Development of Insulin Resistance
The Enos Polymorphisms and Development of T2d
The Enos Polymorphisms and T2d Complications
CONCLUDING REMARKS
CONSENT FOR PUBLICATION
CONFLICT OF INTEREST
ACKNOWLEDGEMENTS
REFERENCES
Role of Nitric Oxide in Diabetic Wound Healing
Hamideh Afzali1, Tara Ranjbar2, Khosrow Kashfi2 and Asghar Ghasemi1,*
INTRODUCTION
Types of Wound
Pathophysiology of Diabetic Foot Ulcer
Peripheral Neuropathy
Peripheral Arterial Disease (PAD)
PHASES OF WOUND HEALING
Hemostasis (Coagulation)
Inflammation
Proliferation
Tissue Remodeling
CHANGES IN HEALING PHASES IN DIABETIC WOUNDS
Nitric Oxide Synthesis in the Skin
Expression of NOS Isoforms in the Skin
NOS-Independent NO Synthesis in the Skin
The Role of Surface Bacteria in Skin Production of NO
UVA Radiation and NO Production
NO AND WOUND HEALING
NO Metabolites as an Index of Wound NO
Role of NO different Phases of Wound Healing
Inflammation
Vasculogenesis and Angiogenesis
Re-epithelialization
NO AND DIABETIC WOUND HEALING
Role of NO Different Phases of Diabetic Wound Healing
NO AND THERAPEUTIC STRATEGIES FOR DIABETIC WOUND
L-arginine
Regulation of NOS Expression
Acidified Nitrite
NO Donor Systems
CONCLUDING REMARKS
CONSENT FOR PUBLICATION
CONFLICT OF INTEREST
ACKNOWLEDGEMENT
REFERENCES
Role of Nitric Oxide in Type 2 Diabetes-Induced Osteoporosis
Nasibeh Yousefzadeh1, Sajad Jeddi1, Khosrow Kashfi2 and Asghar Ghasemi1,*
INTRODUCTION
NITRIC OXIDE AND BONE: A BRIEF OVERVIEW
NOS Expression in the Bone Cells
TYPE 2 DIABETES AND BONE INDICES
Type 2 Diabetes and BMD
Type 2 Diabetes and Trabecular and Cortical Bone Microarchitectures
Type 2 Diabetes and Bone Cells
Bone No Bioavailability in Type 2 Diabetes
BONE REMODELING
Bone Remodeling in Type 2 Diabetes: Role of NO
NITRIC OXIDE-BASED TREATMENT OF DIABETOPOROSIS
Possible Strategies for Nitric Oxide-based Treatment of Diabetoporosis
CONCLUDING REMARKS
CONSENT OF PUBLICATION
CONFLICT OF INTEREST
ACKNOWLEDGEMENT
REFERENCES
Hyperuricemia, Type 2 Diabetes and Insulin Resistance: Role of Nitric Oxide
Zahra Bahadoran1, Parvin Mirmiran1,2, Khosrow Kashfi3,4 and Asghar Ghasemi5,*
INTRODUCTION
A BRIEF OVERVIEW OF URIC ACID METABOLISM AND FUNCTION
Uric Acid Synthesis In Human: Role Of Xor
Regulation of Circulating Uric Acid Levels
Physiologic Roles of Normal Uric Acid Levels
Pathological Effects of Hyperuricemia
HYPERURICEMIA, T2D AND INSULIN RESISTANCE
Epidemiological Evidence
Experimental and Clinical Evidence
Underlying Mechanisms Connecting UA to Insulin Resistance and T2D
Role of No in Hyperuricemia-Induced Dysglycemia and Insulin Resistance
CONCLUDING REMARKS
CONSENT OF PUBLICATION
CONFLICT OF INTEREST
ACKNOWLEDGEMENT
REFERENCES
Therapeutic Management of Type 2 Diabetes: The Nitric Oxide Axis
Tara Ranjbar1, Jennifer L. O’Connor1,2 and Khosrow Kashfi1,3,*
INTRODUCTION
BIGUANIDES
General Mechanism of Action
Metformin and Its Nitric Oxide Connection
THIAZOLIDINEDIONES
General Mechanism of Action
Thiazolidinediones and Their Nitric Oxide Connection
SULFONYLUREAS
General Mechanism of Action
Sulfonylurea and Their Nitric Oxide Connection
MEGLITINIDES
General Mechanism of Action
Meglitinides and Their Nitric Oxide Connection
DIPEPTIDYL PEPTIDASE-4 (DPP-4) INHIBITORS
General Mechanism of Action
DPP-4 Inhibitors and Their Nitric Oxide Connection
GLUCAGON-LIKE PEPTIDE 1 RECEPTOR (GLP-1) AGONISTS
General Mechanism of Action
GLP-1 Receptor Agonists and Their Nitric Oxide Connection
ALPHA-GLUCOSIDASE INHIBITORS
General Mechanism of Action
Alpha-Glucosidase Inhibitors and Their Nitric Oxide Connection
SODIUM-GLUCOSE CO-TRANSPORTER 2 INHIBITORS (SGLT2) INHIBITORS
General Mechanism of Action
SGLT2 Inhibitors and Their Nitric Oxide Connection
NITRATE-NITRITE-NO PATHWAY: A POTENTIAL THERAPEUTIC TARGET FOR T2D?
CONCLUDING REMARKS
CONSENT FOR PUBLICATION
CONFLICT OF INTEREST
ACKNOWLEDGMENTS
REFERENCES
Brain Insulin Resistance, Nitric Oxide and Alzheimer’s Disease Pathology
Zhe Pei1, Kuo-Chieh Lee1, Amber Khan1,2 and Hoau-Yan Wang1,2,*
INTRODUCTION
INSULIN RECEPTOR SIGNALING AND ITS INTERACTION WITH NO SYSTEM
The Inter-Relationship between Brain Insulin Signaling and Memory/Cognitive Performance
The Role of No in Brain Insulin Resistance and Cognitive Performance
CONCLUDING REMARKS
CONSENT FOR PUBLICATION
CONFLICT OF INTEREST
ACKNOWLEDGEMENT
REFERENCES
Arginine, Nitric Oxide, and Type 2 Diabetes
Parvin Mirmiran1,2, Zahra Bahadoran1, Khosrow Kashfi3 and Asghar Ghasemi4,*
INTRODUCTION
PLASMA ARG FLUX
Arginine Biosynthesis Pathways
Arginine Catabolic Pathways
Arginase and Urea Production
Arg and NO Production
Intracellular Arg Pools and NO Production
Pharmacokinetics of Arg
ARG, INSULIN RESISTANCE, AND T2D
Changes in Arg Metabolism and Pathophysiology of T2D
Arg Supplementation in T2D
Arg Supplementation in Metabolic Syndrome and its Components
Doses of Arg Supplementation
CONCLUDING REMARKS
CONSENT OF PUBLICATION
CONFLICT OF INTEREST
ACKNOWLEDGEMENT
REFERENCES
Citrulline, Nitric Oxide, and Type 2 Diabetes
Parvin Mirmiran1,2, Zahra Bahadoran1, Khosrow Kashfi3 and Asghar Ghasemi4,*
INTRODUCTION
CIT BIOSYNTHESIS PATHWAYS
Intestinal Biosynthesis of Cit
Extra-Intestinal Biosynthesis of Cit
Gut-Liver Metabolism of Cit
INTERORGAN EXCHANGE OF CIT AND ARG PRODUCTION
Cit and No Production
Pharmacokinetics of Cit
CIT AND T2D
Change of Cit Metabolism in T2d
Cit Supplementation, T2D, and its Complications
CONCLUDING REMARKS
CONSENT FOR PUBLICATION
CONFLICT OF INTEREST
ACKNOWLEDGEMENT
REFERENCES
Nitrate, Nitrite and Type 2 Diabetes
Zahra Bahadoran1, Parvin Mirmiran1,2, Khosrow Kashfi3 and Asghar Ghasemi4
INTRODUCTION
INORGANIC NITRATE AND NITRITE: A NUTRITIONAL PERSPECTIVE
Food and Dietary Sources of Inorganic NO3 and NO2
Dietary Intake of NO3 and NO2 and Risk of Diseases
EFFECTS OF INORGANIC NO3 AND NO2 ON TYPE 2 DIABETES AND INSULIN RESISTANCE
Animal Studies
Human Clinical Trials
WHY BENEFICIAL EFFECTS OF INORGANIC NO3-NO2 IN ANIMALS DO NOT TRANSLATE INTO HUMAN CLINICAL TRIALS?
CONCLUDING REMARKS
CONFLICT OF INTEREST
ACKNOWLEDGEMENT
CONSENT OF PUBLICATION
REFERENCES
Potential Applications of Nitric Oxide Donors in Type 2 Diabetes
Zahra Bahadoran1, Parvin Mirmiran1,2, Mehrnoosh Bahmani3 and Asghar Ghasemi4,*
INTRODUCTION
A BRIEF OVERVIEW OF NITRIC OXIDE DONORS
Box. 1 Angeli’s Salt
NO DONORS AND INSULIN-GLUCOSE HOMEOSTASIS
Sodium Nitroprusside
S-nitrosothiols
NONOates
CONCLUDING REMARKS
CONSENT FOR PUBLICATION
CONFLICT OF INTEREST
ACKNOWLEDGEMENT
REFERENCES
Subject Index

Citation preview

The Role of Nitric Oxide in Type 2 Diabetes Edited by Asghar Ghasemi Endocrine Physiology Research Center, Research Institute for Endocrine Sciences, Shahid Beheshti University of Medical Sciences, Tehran, Iran

Khosrow Kashfi Department of Molecular, Cellular, and Biomedical Sciences, Sophie Davis School of Biomedical Education, City University of New York School of Medicine, New York, USA Graduate Program in Biology, City University of New York Graduate Center, New York, USA

Zahra Bahadoran Nutrition and Endocrine Research Center, Research Institute for Endocrine Sciences, Shahid Beheshti University of Medical Sciences, Tehran, Iran

The Role of Nitric Oxide in Type 2 Diabetes Editors: Asghar Ghasemi, Khosrow Kashfi, Zahra Bahadoran ISBN (Online): 978-981-5079-81-4 ISBN (Print): 978-981-5079-82-1 ISBN (Paperback): 978-981-5079-83-8 © 2022, Bentham Books imprint. Published by Bentham Science Publishers Pte. Ltd. Singapore. All Rights Reserved.

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CONTENTS FOREWORD ........................................................................................................................................... i PREFACE ................................................................................................................................................ iii REFERENCES ............................................................................................................................... v LIST OF CONTRIBUTORS .................................................................................................................. vii CHAPTER 1 PATHOPHYSIOLOGY OF TYPE 2 DIABETES: A GENERAL OVERVIEW OF GLUCOSE AND INSULIN HOMEOSTASIS ...................................................................................... Asghar Ghasemi and Khosrow Kashfi INTRODUCTION .......................................................................................................................... EPIDEMIOLOGY OF DIABETES .............................................................................................. DIAGNOSIS OF DIABETES ........................................................................................................ GLUCOSE HOMEOSTASIS ........................................................................................................ POST-ABSORPTIVE STATE: THE FASTING STATE ........................................................... Glucose Production ................................................................................................................. Glucose Utilization ................................................................................................................. POST-PRANDIAL STATE ........................................................................................................... MECHANISMS UNDERLYING GLUCOSE HOMEOSTASIS ............................................... Central Mechanisms of Glucose Homeostasis ........................................................................ Glucose Sensing by Neurons .................................................................................................. Peripheral Mechanisms of Glucose Homeostasis ................................................................... INSULIN .......................................................................................................................................... Insulin Secretion ..................................................................................................................... Mechanism of Insulin Secretion ............................................................................................. Box 1 Circulating Insulin Concentrations ............................................................................... Box 2 Technical Considerations on Circulating Insulin Measurement .................................. Insulin Signaling Pathways ..................................................................................................... Pathophysiology of Type 2 Diabetes ...................................................................................... Insulin Resistance ................................................................................................................... β-cell Dysfunction ................................................................................................................... CONCLUDING REMARKS ......................................................................................................... CONSENT FOR PUBLICATION ................................................................................................ CONFLICT OF INTEREST ......................................................................................................... ACKNOWLEDGEMENT ............................................................................................................. REFERENCES ............................................................................................................................... CHAPTER 2 NITRIC OXIDE: A BRIEF HISTORY OF DISCOVERY AND TIMELINE OF ITS RESEARCH ..................................................................................................................................... Asghar Ghasemi and Khosrow Kashfi INTRODUCTION .......................................................................................................................... HISTORY OF NO FIELD ............................................................................................................. Diabetes-Related NO Research ............................................................................................... CONCLUDING REMARKS ........................................................................................................ CONSENT FOR PUBLICATION ................................................................................................ CONFLICT OF INTEREST ......................................................................................................... ACKNOWLEDGEMENT ............................................................................................................. REFERENCES ...............................................................................................................................

1 1 2 3 3 4 5 6 6 7 7 9 9 10 10 10 12 13 14 15 16 18 19 20 20 20 20 27 27 28 32 32 33 33 33 33

CHAPTER 3 IMPAIRED NITRIC OXIDE METABOLISM IN TYPE 2 DIABETES: AT A GLANCE .................................................................................................................................................. 39 Zahra Bahadoran, Mattias Carlström, Parvin Mirmiran and Asghar Ghasemi

INTRODUCTION .......................................................................................................................... ROLE OF NO IN GLUCOSE AND INSULIN HOMEOSTASIS .............................................. T2D AND WHOLE-BODY NO METABOLISM ........................................................................ NO DEFICIENCY IN T2D ............................................................................................................ T2D and Circulating NO: an Epidemiologic Point of View ................................................... Underlying Mechanisms of Impaired NO Metabolism/Action in T2D .................................. Impaired L-Arginine NOS-NO Pathway ................................................................................ Impaired NO3 -NO2 -NO Pathway ........................................................................................... Impaired NO Transport ........................................................................................................... Impaired NO Signaling ........................................................................................................... CONCLUDING REMARKS ......................................................................................................... CONFLICT OF INTEREST ......................................................................................................... ACKNOWLEDGEMENT ............................................................................................................. CONSENT OF PUBLICATION ................................................................................................... REFERENCES ............................................................................................................................... CHAPTER 4 ASYMMETRICAL DIMETHYL ARGININE, NITRIC OXIDE, AND TYPE 2 DIABETES ............................................................................................................................................... Zahra Bahadoran, Mattias Carlström, Parvin Mirmiran and Asghar Ghasemi INTRODUCTION .......................................................................................................................... ADMA BIOSYNTHESIS AND METABOLISM ........................................................................ Adma and Regulation of No Synthesis ................................................................................... Cellular Uptake of ADMA ...................................................................................................... Inhibitory Effects of ADMA on NOS Expression and Activity ............................................. ADMA and T2D ..................................................................................................................... DDAH and T2D: Lessons from Genetic Studies .................................................................... Plasma and Tissue Concentrations of ADMA in T2D ............................................................ Plasma ADMA Levels and Risk of Diabetic Complications .................................................. Other Methylarginines and T2D ............................................................................................. Pharmaceutical Interventions for Elevated Adma .................................................................. CONCLUDING REMARKS ......................................................................................................... CONFLICT OF INTEREST ......................................................................................................... ACKNOWLEDGEMENT ............................................................................................................. CONSENT OF PUBLICATION ................................................................................................... REFERENCES ............................................................................................................................... CHAPTER 5 NITRIC OXIDE-RELATED ORAL MICROBIOTA DYSBIOSIS IN TYPE 2 DIABETES ............................................................................................................................................... Zahra Bahadoran, Pedro González-Muniesa, Parvin Mirmiran and Asghar Ghasemi INTRODUCTION .......................................................................................................................... AN OVERVIEW OF ORAL MICROBIOTA .............................................................................. Oral Nitrate-Reducing Bacteria .............................................................................................. Oral Nitrate Reduction and Nitric Oxide Homeostasis ........................................................... Changes in Oral Microbiota in T2D ....................................................................................... Mechanisms Linking Oral Dysbiosis with Impaired Glucose and Insulin Homeostasis ........ Oral Nitrate-Reducing Bacteria and Nitric Oxide Metabolism in T2D .................................. CONCLUDING REMARKS ......................................................................................................... CONSENT FOR PUBLICATION ................................................................................................ CONFLICT OF INTEREST ......................................................................................................... ACKNOWLEDGEMENTS ........................................................................................................... REFERENCES ...............................................................................................................................

40 42 44 44 47 48 49 52 53 54 54 55 55 55 55 67 68 68 71 71 72 73 73 74 75 77 78 79 80 80 80 80 87 88 88 90 93 95 97 99 99 100 100 100 100

CHAPTER 6 NITRIC OXIDE AND TYPE 2 DIABETES: LESSONS FROM GENETIC STUDIES .................................................................................................................................................. Zahra Bahadoran, Parvin Mirmiran, Mattias Carlström and Asghar Ghasemi INTRODUCTION .......................................................................................................................... A BRIEF OVERVIEW OF NOS ENZYMES: GENE STRUCTURE AND CHROMOSOMAL LOCALIZATION ........................................................................................ Genetically-Modified Nos Enzymes and Impaired Glucose and Insulin Homeostasis .......... Common Polymorphisms of NOS Enzymes ........................................................................... Common Polymorphisms of nNOS and iNOS ....................................................................... Common Polymorphisms of eNOS ........................................................................................ The eNOS Polymorphisms and Serum NO Metabolites ......................................................... The eNOS Polymorphisms and Development of Insulin Resistance ...................................... The eNOS Polymorphisms and Development of T2D ............................................................ The eNOS Polymorphisms and T2D Complications ............................................................... CONCLUDING REMARKS ......................................................................................................... CONSENT FOR PUBLICATION ................................................................................................ CONFLICT OF INTEREST ......................................................................................................... ACKNOWLEDGEMENTS ........................................................................................................... REFERENCES ............................................................................................................................... CHAPTER 7 ROLE OF NITRIC OXIDE IN DIABETIC WOUND HEALING ........................... Hamideh Afzali, Tara Ranjbar, Khosrow Kashfi and Asghar Ghasemi INTRODUCTION .......................................................................................................................... Types of Wound ...................................................................................................................... Pathophysiology of Diabetic Foot Ulcer ................................................................................. Peripheral Neuropathy ............................................................................................................ Peripheral Arterial Disease (PAD) .......................................................................................... PHASES OF WOUND HEALING ................................................................................................ Hemostasis (Coagulation) ....................................................................................................... Inflammation ........................................................................................................................... Proliferation ............................................................................................................................ Tissue Remodeling .................................................................................................................. CHANGES IN HEALING PHASES IN DIABETIC WOUNDS ............................................... Nitric Oxide Synthesis in the Skin .......................................................................................... Expression of NOS Isoforms in the Skin ................................................................................ NOS-Independent NO Synthesis in the Skin .......................................................................... The Role of Surface Bacteria in Skin Production of NO ........................................................ UVA Radiation and NO Production ....................................................................................... NO AND WOUND HEALING ...................................................................................................... NO Metabolites as an Index of Wound NO ............................................................................ Role of NO different Phases of Wound Healing .................................................................... Inflammation ........................................................................................................................... Vasculogenesis and Angiogenesis .......................................................................................... Re-epithelialization ................................................................................................................. NO AND DIABETIC WOUND HEALING ................................................................................. Role of NO Different Phases of Diabetic Wound Healing ..................................................... NO AND THERAPEUTIC STRATEGIES FOR DIABETIC WOUND ................................... L-arginine ................................................................................................................................ Regulation of NOS Expression ............................................................................................... Acidified Nitrite ...................................................................................................................... NO Donor Systems .................................................................................................................

107 107 108 111 113 113 114 116 116 117 118 119 119 119 119 120 128 128 129 130 130 130 131 131 132 133 134 134 135 136 136 136 137 138 138 139 139 140 141 141 143 143 147 147 148 148

CONCLUDING REMARKS ......................................................................................................... CONSENT FOR PUBLICATION ................................................................................................ CONFLICT OF INTEREST ......................................................................................................... ACKNOWLEDGEMENT ............................................................................................................. REFERENCES ...............................................................................................................................

150 150 150 150 150

CHAPTER 8 ROLE OF NITRIC OXIDE IN TYPE 2 DIABETES-INDUCED OSTEOPOROSIS Nasibeh Yousefzadeh, Sajad Jeddi, Khosrow Kashfi and Asghar Ghasemi INTRODUCTION .......................................................................................................................... NITRIC OXIDE AND BONE: A BRIEF OVERVIEW .............................................................. NOS Expression in the Bone Cells ......................................................................................... TYPE 2 DIABETES AND BONE INDICES ................................................................................ Type 2 Diabetes and BMD ..................................................................................................... Type 2 Diabetes and Trabecular and Cortical Bone Microarchitectures ................................ Type 2 Diabetes and Bone Cells ............................................................................................. Bone NO Bioavailability in Type 2 Diabetes ......................................................................... BONE REMODELING .................................................................................................................. Bone Remodeling in Type 2 Diabetes: Role of NO ............................................................... NITRIC OXIDE-BASED TREATMENT OF DIABETOPOROSIS ......................................... Possible Strategies for Nitric Oxide-based Treatment of Diabetoporosis .............................. CONCLUDING REMARKS ......................................................................................................... CONSENT OF PUBLICATION ................................................................................................... CONFLICT OF INTEREST ......................................................................................................... ACKNOWLEDGEMENT ............................................................................................................. REFERENCES ...............................................................................................................................

161

CHAPTER 9 HYPERURICEMIA, TYPE 2 DIABETES AND INSULIN RESISTANCE: ROLE OF NITRIC OXIDE ................................................................................................................................ Zahra Bahadoran, Parvin Mirmiran, Khosrow Kashfi and Asghar Ghasemi INTRODUCTION .......................................................................................................................... A BRIEF OVERVIEW OF URIC ACID METABOLISM AND FUNCTION ......................... Uric Acid Synthesis In Human: Role of XOR ........................................................................ Regulation of Circulating Uric Acid Levels ........................................................................... Physiologic Roles of Normal Uric Acid Levels ..................................................................... Pathological Effects of Hyperuricemia ................................................................................... HYPERURICEMIA, T2D AND INSULIN RESISTANCE ........................................................ Epidemiological Evidence ...................................................................................................... Experimental and Clinical Evidence ....................................................................................... Underlying Mechanisms Connecting UA to Insulin Resistance and T2D ............................. Role of No in Hyperuricemia-Induced Dysglycemia and Insulin Resistance ........................ CONCLUDING REMARKS ......................................................................................................... CONSENT OF PUBLICATION ................................................................................................... CONFLICT OF INTEREST ......................................................................................................... ACKNOWLEDGEMENT ............................................................................................................. REFERENCES ............................................................................................................................... CHAPTER 10 THERAPEUTIC MANAGEMENT OF TYPE 2 DIABETES: THE NITRIC OXIDE AXIS ........................................................................................................................................... Tara Ranjbar, Jennifer L. O’Connor and Khosrow Kashfi INTRODUCTION .......................................................................................................................... BIGUANIDES ................................................................................................................................. General Mechanism of Action ................................................................................................

161 163 163 164 164 164 165 167 167 168 170 171 173 173 174 174 174 190 191 192 192 192 194 194 195 195 196 197 198 201 202 202 202 203 210 211 212 212

Metformin and Its Nitric Oxide Connection ........................................................................... THIAZOLIDINEDIONES ............................................................................................................. General Mechanism of Action ................................................................................................ Thiazolidinediones and Their Nitric Oxide Connection ......................................................... SULFONYLUREAS ....................................................................................................................... General Mechanism of Action ................................................................................................ Sulfonylurea and Their Nitric Oxide Connection ................................................................... MEGLITINIDES ............................................................................................................................ General Mechanism of Action ................................................................................................ Meglitinides and Their Nitric Oxide Connection ................................................................... DIPEPTIDYL PEPTIDASE-4 (DPP-4) INHIBITORS ............................................................... General Mechanism of Action ................................................................................................ DPP-4 Inhibitors and Their Nitric Oxide Connection ............................................................ GLUCAGON-LIKE PEPTIDE 1 RECEPTOR (GLP-1) AGONISTS ...................................... General Mechanism of Action ................................................................................................ GLP-1 Receptor Agonists and Their Nitric Oxide Connection .............................................. ALPHA-GLUCOSIDASE INHIBITORS ..................................................................................... General Mechanism of Action ................................................................................................ Alpha-Glucosidase Inhibitors and Their Nitric Oxide Connection ........................................ SODIUM-GLUCOSE CO-TRANSPORTER 2 INHIBITORS (SGLT2) INHIBITORS ......... General Mechanism of Action ................................................................................................ SGLT2 Inhibitors and Their Nitric Oxide Connection ........................................................... NITRATE-NITRITE-NO PATHWAY: A POTENTIAL THERAPEUTIC TARGET FOR T2D? ................................................................................................................................................. CONCLUDING REMARKS ......................................................................................................... CONSENT FOR PUBLICATION ................................................................................................ CONFLICT OF INTEREST ......................................................................................................... ACKNOWLEDGMENTS .............................................................................................................. REFERENCES ............................................................................................................................... CHAPTER 11 BRAIN INSULIN RESISTANCE, NITRIC OXIDE AND ALZHEIMER’S DISEASE PATHOLOGY ....................................................................................................................... Zhe Pei, Kuo-Chieh Lee, Amber Khan and Hoau-Yan Wang INTRODUCTION .......................................................................................................................... INSULIN RECEPTOR SIGNALING AND ITS INTERACTION WITH NO SYSTEM ....... The Inter-Relationship between Brain Insulin Signaling and Memory/Cognitive Performance ............................................................................................................................ The Role of No in Brain Insulin Resistance and Cognitive Performance .............................. CONCLUDING REMARKS ......................................................................................................... CONSENT FOR PUBLICATION ................................................................................................ CONFLICT OF INTEREST ......................................................................................................... ACKNOWLEDGEMENT ............................................................................................................. REFERENCES ............................................................................................................................... CHAPTER 12 ARGININE, NITRIC OXIDE, AND TYPE 2 DIABETES ...................................... Parvin Mirmiran, Zahra Bahadoran, Khosrow Kashfi and Asghar Ghasemi INTRODUCTION .......................................................................................................................... PLASMA ARG FLUX .................................................................................................................... Arginine Biosynthesis Pathways ............................................................................................. Arginine Catabolic Pathways .................................................................................................. Arginase and Urea Production ................................................................................................ Arg and NO Production ..........................................................................................................

213 214 214 215 215 215 216 217 217 217 218 218 219 219 219 220 221 221 221 221 221 222 223 224 224 225 225 225 238 239 239 241 244 249 249 249 250 250 260 260 261 262 263 264 265

Intracellular Arg Pools and NO Production ............................................................................ Pharmacokinetics of Arg ......................................................................................................... ARG, INSULIN RESISTANCE, AND T2D ................................................................................. Changes in Arg Metabolism and Pathophysiology of T2D .................................................... Arg Supplementation in T2D .................................................................................................. Arg Supplementation in Metabolic Syndrome and its Components ....................................... Doses of Arg Supplementation ............................................................................................... CONCLUDING REMARKS ......................................................................................................... CONSENT OF PUBLICATION ................................................................................................... CONFLICT OF INTEREST ......................................................................................................... ACKNOWLEDGEMENT ............................................................................................................. REFERENCES ...............................................................................................................................

266 267 269 269 271 273 274 275 275 275 275 275

CHAPTER 13 CITRULLINE, NITRIC OXIDE, AND TYPE 2 DIABETES ................................. Parvin Mirmiran, Zahra Bahadoran, Khosrow Kashfi and Asghar Ghasemi INTRODUCTION .......................................................................................................................... CIT BIOSYNTHESIS PATHWAYS ............................................................................................ Intestinal Biosynthesis of Cit .................................................................................................. Extra-Intestinal Biosynthesis of Cit ........................................................................................ Gut-Liver Metabolism of Cit .................................................................................................. INTERORGAN EXCHANGE OF CIT AND ARG PRODUCTION ........................................ Cit and No Production ............................................................................................................ Pharmacokinetics of Cit .......................................................................................................... CIT AND T2D ................................................................................................................................. Change of Cit Metabolism in T2D ......................................................................................... Cit Supplementation, T2D, and its Complications ................................................................. CONCLUDING REMARKS ......................................................................................................... CONSENT FOR PUBLICATION ................................................................................................ CONFLICT OF INTEREST ......................................................................................................... ACKNOWLEDGEMENT ............................................................................................................. REFERENCES ...............................................................................................................................

284

CHAPTER 14 NITRATE, NITRITE AND TYPE 2 DIABETES ..................................................... Zahra Bahadoran, Parvin Mirmiran, Khosrow Kashfi and Asghar Ghasemi INTRODUCTION .......................................................................................................................... INORGANIC NITRATE AND NITRITE: A NUTRITIONAL PERSPECTIVE .................... Food and Dietary Sources of Inorganic NO3 and NO2 .......................................................... Dietary Intake of NO3 and NO 2 and Risk of Diseases .......................................................... EFFECTS OF INORGANIC NO 3 AND NO 2 ON TYPE 2 DIABETES AND INSULIN RESISTANCE ................................................................................................................................. Animal Studies ........................................................................................................................ Human Clinical Trials ............................................................................................................. WHY BENEFICIAL EFFECTS OF INORGANIC NO3 -NO2 IN ANIMALS DO NOT TRANSLATE INTO HUMAN CLINICAL TRIALS? ............................................................... CONCLUDING REMARKS ......................................................................................................... CONFLICT OF INTEREST ......................................................................................................... ACKNOWLEDGEMENT ............................................................................................................. CONSENT OF PUBLICATION ................................................................................................... REFERENCES ...............................................................................................................................

285 286 286 289 289 290 291 292 293 293 294 296 296 296 296 296 303 304 305 305 306 308 308 312 316 317 318 318 318 318

CHAPTER 15 POTENTIAL APPLICATIONS OF NITRIC OXIDE DONORS IN TYPE 2 DIABETES ............................................................................................................................................... Zahra Bahadoran, Parvin Mirmiran, Mehrnoosh Bahmani and Asghar Ghasemi INTRODUCTION .......................................................................................................................... A BRIEF OVERVIEW OF NITRIC OXIDE DONORS ............................................................ Box. 1 Angeli’s Salt ................................................................................................................ NO DONORS AND INSULIN-GLUCOSE HOMEOSTASIS ................................................... Sodium Nitroprusside ............................................................................................................. S-nitrosothiols ......................................................................................................................... NONOates ............................................................................................................................... CONCLUDING REMARKS ......................................................................................................... CONSENT FOR PUBLICATION ................................................................................................ CONFLICT OF INTEREST ......................................................................................................... ACKNOWLEDGEMENT ............................................................................................................. REFERENCES ...............................................................................................................................

324 325 326 331 331 331 336 339 339 340 340 341 341

SUBJECT INDEX .................................................................................................................................... 

i

FOREWORD The global obesity and overweight pandemic that causes the increasing number of patients with type 2 diabetes (T2D) is a major challenge for healthcare systems worldwide. With its cardiovascular complications, this metabolic disorder is one of the major causes of morbidity and mortality worldwide. On top of lifestyle and dietary recommendations to prevent or control T2D, a tremendous amount of research has been invested in understanding disease mechanisms better and developing novel drugs. Even if new pharmaceuticals have entered the clinical arena in recent years, metformin is still the first-line option, even after more than 60 years. This points to the necessity to develop therapeutic strategies based on biological pathways that have not previously been the center focus of diabetes research. Such an area is nitric oxide research. Nitric oxide (NO) is one of the universal signaling molecules in mammalian species. When discovered in the 1980s, it portrayed a completely novel principle, where a small, unstable, and reactive free radical gas was involved in cell signaling. Its chemical nature makes it react with other radicals and transition metals; one example of the latter is how NO activates soluble guanylyl cyclase to generate cGMP, a classical form of NO signaling that, e.g., induces vasodilation. Binding to heme in cytochrome c oxidase, leading to inhibition of mitochondrial respiration, is another example. In addition, post-translational nitrosation of many proteins, which regulates their function, is another signaling modality of NO. This pluripotency of NO explains why it is involved in regulating such diverse processes as cardiovascular function, metabolism, inflammation, and nerve signaling. The canonical pathway for NO generation involves the substrates L-arginine and molecular oxygen and specific NO synthases (N.O.S.s), of which there are three isoforms. Two of them are more constitutively expressed (endothelial N.O.S. and neuronal N.O.S.), while an inducible isoform (inducible N.O.S.) is involved during inflammatory conditions. The half-life of NO is within seconds due to binding to heme or to rapid oxidation, which forms the inorganic anions nitrite and nitrate that are widely used both in vitro and in vivo as more stable surrogate measures of NO. Interestingly, discoveries in the mid-1990s revealed that these supposedly inert anions could be recycled back to bioactive NO and other reactive nitrogen species. The first step in this nitrate-nitrate-NO pathway involves active uptake of circulating nitrate in the salivary glands, after which nitrate in the saliva is reduced to nitrite by oral commensal bacteria, a function that mammalian cells are poor in performing. Swallowed salivary nitrite is rapidly absorbed in the gut, and then there are several pathways for further reduction to NO. Of interest is that the nitrate-nitrite-NO pathway can be fueled by a diet where certain vegetables contain high levels of nitrate. This pathway can be viewed as a parallel backup system to the L-arginin-NOS-NO pathway, perhaps with more importance during hypoxic and ischemic conditions. This book, to my knowledge, is the first of its kind, Asghar Ghasemi and collaborators present a comprehensive and detailed overview of our current knowledge on the role of NO in T2D. The rationale for this book is the growing evidence of the involvement of the NO system in diabetes. An impressive amount of research has clarified that NO is deeply involved on many levels to uphold metabolic homeostasis and that NO signaling is negatively affected in T2D. Of interest is that several of the pharmaceuticals used in T2D affect the NO system and perhaps even more so by the drugs we use to treat diabetic cardiovascular complications. Experimental works in animal models of obesity or T2D show promising results with interventions aimed to increase NO signaling. However, translation into human studies has so far been less successful, but larger and more prolonged studies are clearly needed. There is an

ii

intriguing dietary aspect here since NO bioavailability can be boosted by nitrate in our diet, which is supported by epidemiological studies showing that green leafy vegetables, which are high in nitrate, stand out as particularly protective against the development of T2D and cardiovascular disease. Clearly, more research on the role of NO in metabolic regulation and T2D is needed, and in this context, the present book is of great value to anyone interested in this field of research.

Eddie Weitzberg, M.D., Ph.D. Professor, Senior Consultant Department of Physiology and Pharmacology, Karolinska Institutet Department of Perioperative Medicine and Intensive Care, Karolinska University Hospital Stockholm Sweden

iii

PREFACE Nitric oxide (NO) is a colorless, odorless, primordial flammable gas that has been present in the earth's atmosphere from the beginning of time. Historically, NO was regarded as an industrial toxin or pollutant generated in many industries; however, it is now well recognized that NO is endogenously produced and has an important biological role in most mammalian tissues. The vital role of NO in human biology was recognized in 1992 when the journal Science introduced NO as the “Molecule of the Year” [1] and in 1998 when the Nobel Prize in Physiology and Medicine was awarded to Robert F. Furchgott, Louis J. Ignarro, and Ferid Murad for the major discoveries surrounding it and establishing its role as a messenger molecule. According to the World Health Organization (WHO), the prevalence of obesity across the globe has approximately doubled since 1980. In the U.S., about one-third of the adult population is obese, and an additional one-third is overweight [2]. Obesity is the fastestgrowing lethal disease in Western and developing countries. People do not die due to obesity itself but from its complications, which shorten the life span [3, 4]. In addition, obesity leads to many other diseases, including type-2 diabetes (T2D) and its complication. T2D, which used to be referred to as adult-onset or non-insulin-dependent diabetes, accounts for over 90–95% of all diabetes; T2D is a complex metabolic disorder essentially characterized by alterations in lipid metabolism, insulin resistance, and pancreatic β-cell dysfunction [5]. Unfortunately, there are no effective treatments available for T2D, although there have been many developments in the therapeutic arena [6]. Hence there is an urgent need to develop new preventative and/or therapeutic strategies to combat T2D. Over the past three decades, NO has emerged as a central regulator of energy metabolism and body composition. NO bioavailability is decreased in animal models of diet-induced obesity and in obese and insulin-resistant patients, and increasing NO output has remarkable effects on obesity and insulin resistance [7]. This volume is a collection of reviews dealing with The Role of Nitric Oxide in Type 2 Diabetes”. These reviews provide a unique overview of NO signaling, pointing out key areas for more detailed research. We hope that the breadth of the topics covered in this volume will provide new perspectives and help to stimulate research towards unanswered questions. Chapter 1 is an overview of the pathophysiology of T2D by Drs. Ghasemi and Kashfi entitled, “Pathophysiology of Type 2 Diabetes: A General Overview of Glucose and Insulin Homeostasis”. A better understanding of the pathophysiology of T2D provides an opportunity for revising the current therapeutic modalities, from a primary glycemic control to a pathophysiological-based approach. This chapter provides essential information on glucose homeostasis and the pathophysiology of T2D. Chapter 2 by Drs. Ghasemi and Kashfi is entitled “Nitric oxide: A Brief History of Discovery and Timeline of its Research.” This chapter highlights the discovery of NO in mammals and its role as a signaling molecule. The overview describes the chronological development of NO, emphasizing the events in the last two decades of the 20th century. Chapter 3 is a review by Drs. Bahadoran, Carlström, Mirmiran, and Ghasemi entitled, “Impaired Nitric Oxide Metabolism in Type 2 Diabetes: At a Glance”. Abnormal NO metabolism is associated with the development of insulin resistance and T2D, which in turn can lead to impaired NO homeostasis. The concept of NO deficiency is supported by results from human studies on polymorphisms of endothelial NO synthase (eNOS) gene, animal knockout models for NO synthase isoforms (N.O.S.s), and pharmacological inhibitors of N.O.S. This chapter focuses on the role of impaired NO metabolism in T2D.

iv

Chapter 4 by Drs. Bahadoran, Carlström, Mirmiran, and Ghasemi is entitled “Asymmetrical Dimethyl Arginine, Nitric Oxide, and Type 2 Diabetes”. Asymmetric dimethylarginine (ADMA) is an endogenous competitive inhibitor of nitric oxide synthases. Over-production leads to decreased NO bioavailability and diabetes complications, including cardiovascular diseases, nephropathy, and retinopathy, with increased mortality risk. This chapter discusses how disrupted ADMA metabolism contributes to the development of T2D and its complications. Chapter 5 is a contribution by Drs. Bahadoran, González-Muniesa, Mirmiran, and Ghasemi is entitled, “Nitric Oxide-Related Oral Microbiota Dysbiosis in Type 2 Diabetes”. This chapter gives an overview of oral microbiota dysbiosis in T2D, focusing on nitrate-reducing bacteria and their metabolic activity. Chapter 6, entitled “Nitric oxide and Type 2 Diabetes: Lessons from Genetic Studies”, is a contribution by Drs. Bahadoran, Mirmiran, Carlström, and Ghasemi. They discuss current genetic data linking NO metabolism to metabolic disorders, especially insulin resistance and T2D. Chapter 7 is a contribution by Dr. Afzali, Miss Ranjbar, and Drs. Kashfi and Ghasemi entitled, “Role of Nitric Oxide in Diabetic Wound Healing.” NO deficiency is an important mechanism responsible for poor healing in diabetic wounds. The beneficial effects of NO in wound healing are related to its antibacterial properties, regulation of inflammatory response, stimulation of proliferation, differentiation of keratinocytes and fibroblasts, and promotion of angiogenesis and collagen deposition. In this chapter, the function of NO in diabetic wound healing and the possible therapeutic significance of NO in the treatment of diabetic wounds are discussed. Chapter 8 is entitled “Role of Nitric Oxide in Type 2 Diabetes-Induced Osteoporosis” by Drs. Yousefzadeh, Jeddi, Kashfi, and Ghasemi. Diabetoporosis, which is osteoporosis in type 2 diabetic patients, contributes to and aggravates osteoporotic fractures. Decreased eNOSderived NO and higher iNOS-derived NO are some of the critical mechanisms in diabetoporosis. This chapter closely examines the role of NO in diabetoporosis. Chapter 9 by Drs. Bahadoran, Mirmiran, Kashfi, and Ghasemi is entitled, “Hyperuricemia, Type 2 Diabetes and Insulin Resistance: Role of Nitric Oxide”. Hyperuricemia is a risk factor for developing hypertension, cardiovascular diseases, chronic kidney disease, and T2D. It leads to the development of systemic insulin resistance, impaired NO and glucose metabolism, with induction of inflammation and oxidative stress. This chapter highlights the mediatory role of NO metabolism on hyperuricemia-induced dysglycemia and insulin resistance. Chapter 10 is entitled “Therapeutic management of type 2 diabetes: The nitric oxide axis,” by Ms. Ranjbar, O’Connor, and Dr. Kashfi. Current drugs approved for the management of T2D include biguanides, thiazolidinediones, sulfonylureas, meglitinides, dipeptidyl peptidase-4 (DPP-4) inhibitors, glucagon-like peptide-1 (GLP-1) receptor agonists, alpha-glucosidase inhibitors, and sodium-glucose co-transporter 2 (SGLT2) inhibitors. In this chapter, the authors discuss these drugs, examine their mechanism of action, and present evidence that these drugs directly or indirectly modulate NO metabolism. In Chapter 11, “Brain Insulin Resistance, Nitric Oxide and Alzheimer’s Disease Pathology,” Drs. Pei, Lee, Khan, and Wang discuss the role of NO availability in brain insulin resistance in dementia associated with Alzheimer’s disease. Chapter 12 by Drs. Mirmiran, Bahadoran, Kashfi, and Ghasemi, and is entitled “Arginine, Nitric Oxide and Type 2 Diabetes”. In this chapter, the authors provide an overview of the potential efficacy of L-arginine (Arg) as an NO precursor and its effects on glucose and insulin homeostasis and diabetes-induced cardiovascular complications. Chapter 13 is also by Drs. Mirmiran, Bahadoran, Kashfi, and Ghasemi and is entitled “Citrulline, Nitric Oxide and Type 2 Diabetes”. L-Citrulline (Cit) is a precursor of Arg and is involved in NO synthesis. Oral ingestion of Cit effectively elevates

v

total Arg flux and promotes NO production. In this chapter, the authors discuss the potential use of Cit as an effective anti-diabetic agent. Recent data suggest the utility of the nitrate-nitrite-nitric oxide (NO3-NO2-NO) pathway in treating T2D. Supplementation with inorganic NO3-NO2 in animal models of T2D resulted in improved hyperglycemia, insulin sensitivity, and glucose tolerance [8 - 10]. However, the efficacy of NO3-NO2 supplementation on glucose and insulin homeostasis in humans is unproven. In chapter 14, entitled “Nitrate, Nitrite, and Type 2 Diabetes’, Drs. Bahadoran, Mirmiran, Kashfi, and Ghasemi review the animal experiments and human clinical trials, addressing the potential effects of inorganic NO3/NO2 on glucose and insulin homeostasis in T2D. They also provide several plausible scenarios to address the challenge of lost-intranslation of beneficial effects of inorganic NO3 and NO2 from bench to bedside. The final chapter of this book, chapter 15, is a review by Drs. Bahadoran, Mirmiran, Bahmani, and Ghasemi entitled, “Potential Applications of Nitric Oxide Donors in Type 2 Diabetes”. NO-donors have increasingly been studied as promising therapeutic agents for insulin resistance and T2D. This chapter reviews the effects of sodium nitroprusside, Snitrosothiols, and N-diazeniumdiolates on glucose and insulin homeostasis. We hope that the breadth of topics covered in this volume will provide the readers with new perspectives, give some food for thought, and stimulate more research into major unanswered questions.

REFERENCES [1] Culotta E, Koshland DE, Jr. NO news is good news. Science 1992; 258(5090): 1862-5. [http://dx.doi.org/10.1126/science.1361684] [PMID: 1361684] [2] Hales CM, Fryar CD, Carroll MD, Freedman DS, Ogden CL. Trends in Obesity and Severe Obesity Prevalence in US Youth and Adults by Sex and Age, 2007-2008 to 2015-2016. JAMA 2018; 319(16): 1723-5. [http://dx.doi.org/10.1001/jama.2018.3060] [PMID: 29570750] [3] Alemán JO, Eusebi LH, Ricciardiello L, Patidar K, Sanyal AJ, Holt PR. Mechanisms of obesityinduced gastrointestinal neoplasia. Gastroenterology 2014; 146(2): 357-73. [http://dx.doi.org/10.1053/j.gastro.2013.11.051] [PMID: 24315827] [4] Fontaine KR, Redden DT, Wang C, Westfall AO, Allison DB. Years of life lost due to obesity. JAMA 2003; 289(2): 187-93. [http://dx.doi.org/10.1001/jama.289.2.187] [PMID: 12517229] [5] Podell BK, Ackart DF, Richardson MA, DiLisio JE, Pulford B, Basaraba RJ. A model of type 2 diabetes in the guinea pig using sequential diet-induced glucose intolerance and streptozotocin treatment. Dis Model Mech 2017; 10(2)dmm.025593 [http://dx.doi.org/10.1242/dmm.025593] [PMID: 28093504] [6] Srinivasan K, Ramarao P. Animal models in type 2 diabetes research: an overview. Indian J Med Res 2007; 125(3): 451-72. [PMID: 17496368] [7] Sansbury BE, Hill BG. Regulation of obesity and insulin resistance by nitric oxide. Free Radic Biol Med 2014; 73: 383-99. [http://dx.doi.org/10.1016/j.freeradbiomed.2014.05.016] [PMID: 24878261]

vi [8] Gheibi S, Bakhtiarzadeh F, Jeddi S, Farrokhfall K, Zardooz H, Ghasemi A. Nitrite increases glucosestimulated insulin secretion and islet insulin content in obese type 2 diabetic male rats. Nitric Oxide 2017; 64: 39-51. [http://dx.doi.org/10.1016/j.niox.2017.01.003] [PMID: 28089828] [9] Ghasemi A, Jeddi S. Anti-obesity and anti-diabetic effects of nitrate and nitrite. Nitric Oxide 2017; 70: 9-24. [http://dx.doi.org/10.1016/j.niox.2017.08.003] [PMID: 28804022] [10] Bahadoran Z, Mirmiran P, Ghasemi A. Role of Nitric Oxide in Insulin Secretion and Glucose Metabolism. Trends Endocrinol Metab 2020; 31(2): 118-30. [http://dx.doi.org/10.1016/j.tem.2019.10.001] [PMID: 31690508]

Khosrow Kashfi Department of Molecular, Cellular and Biomedical Sciences, Sophie Davis School of Biomedical Education, Graduate Program in Biology, City University of New York School of Medicine, New York, NY 10031, U.S.A Asghar Ghasemi Endocrine Physiology Research Center, Research Institute for Endocrine Sciences, Shahid Beheshti University of Medical Sciences, Tehran, Iran Zahra Bahadoran Nutrition and Endocrine Research Center, Research Institute for Endocrine Sciences, Shahid Beheshti University of Medical Sciences, Tehran, Iran

vii

List of Contributors Asghar Ghasemi

Endocrine Physiology Research Center, Research Institute for Endocrine Sciences, Shahid Beheshti University of Medical Sciences, Tehran, Iran

Amber Khan

Department of Molecular, Cellular and Biomedical Sciences, City University of New York School of Medicine, 160 Convent Avenue, New York, New York 10031, USA Department of Biology, Neuroscience Program, Graduate School of The City University of New York, 365 Fifth Avenue, New York, New York 10061, USA

Hamideh Afzali

Endocrine Physiology Research Center, Research Institute for Endocrine Sciences, Shahid Beheshti University of Medical Sciences, Tehran, Iran

Hoau-Yan Wang

Department of Molecular, Cellular and Biomedical Sciences, City University of New York School of Medicine, 160 Convent Avenue, New York, New York 10031, USA Department of Biology, Neuroscience Program, Graduate School of The City University of New York, 365 Fifth Avenue, New York, New York 10061, USA

Jennifer L. O’Connor

Department of Molecular, Cellular, and Biomedical Sciences, Sophie Davis School of Biomedical Education, City University of New York School of Medicine, New York, NY, USA Department of Chemistry and Physics, State University of New York at Old Westbury, Old Westbury, NY, USA

Khosrow Kashfi

Department of Molecular, Cellular and Biomedical Sciences, City University of New York School of Medicine, Sophie Davis School of Biomedical Education, New York, USA

Mattias Carlström

Department of Physiology and Pharmacology, Karolinska Institute, Stockholm, Sweden

Mehrnoosh Bahmani

Ontario College of Pharmacist, University of Waterloo School of Pharmacy Alumni, Waterloo, Ontario, Canada

Nasibeh Yousefzadeh

Endocrine Physiology Research Center, Research Institute for Endocrine Sciences, Shahid Beheshti University of Medical Sciences, Tehran, Iran

Parvin Mirmiran

Department of Clinical Nutrition and Human Dietetics, Faculty of Nutrition Sciences and Food Technology, National Nutrition and Food Technology Research Institute,Shahid Beheshti University of Medical Sciences, Tehran, Iran

Pedro González-Muniesa Department of Nutrition, Food Science and Physiology,School of Pharmacy and Nutrition, University of Navarra, Pamplona, Spain Center for Nutrition Research; School of Pharmacy and Nutrition, University of Navarra, Pamplona, Spain CIBER Physiopathology of Obesity and Nutrition (CIBERobn, Carlos III Health Institute (ISCIII), Spain, IDISNA, Navarra Institute for Health Research, Pamplona, Spain Sajad Jeddi

Endocrine Physiology Research Center, Research Institute for Endocrine Sciences, Shahid Beheshti University of Medical Sciences, Tehran, Iran

viii Tara Ranjbar

Department of Molecular, Cellular, and Biomedical Sciences, Sophie Davis School of Biomedical Education, City University of New York School of Medicine, New York, NY 10031, USA

Zahra Bahadoran

Nutrition and Endocrine Research Center, Research Institute for Endocrine Sciences, Shahid Beheshti University of Medical Sciences, Tehran, Iran Department of Molecular, Cellular and Biomedical Sciences, City University of New York School of Medicine, 160 Convent Avenue, New York, New York 10031, USA

Zhe Pei

The Role of Nitric Oxide in Type 2 Diabetes, 2022, 1-26

1

CHAPTER 1

Pathophysiology of Type 2 Diabetes: A General Overview of Glucose and Insulin Homeostasis Asghar Ghasemi1,* and Khosrow Kashfi2 Endocrine Physiology Research Center, Research Institute for Endocrine Sciences,Shahid Beheshti University of Medical Sciences, Tehran, Iran 2 Department of Molecular, Cellular and Biomedical Sciences, Sophie Davis School of Biomedical Education,City University of New York School of Medicine, New York, NY 10031, USA 1

Abstract: The prevalence of diabetes is increasing worldwide, and this disease has a tremendous financial burden on most countries. Major types of diabetes are type 1 diabetes and type 2 diabetes (T2D); T2D accounts for 90-95% of all diabetic cases. For better management of diabetes, we need to have a better understanding of its pathophysiology. This chapter provides an overview of glucose homeostasis and the underlying pathophysiology of T2D.

Keywords: β-Cell Dysfunction, Glucose Homeostasis, Insulin, Impaired Glucose Tolerance, Insulin Resistance, Insulin Signaling Pathways, Impaired Fasting Glycemia, Type 2 Diabetes. INTRODUCTION Diabetes is the largest epidemic in human history [1], and there is currently a rapid-growing diabetes pandemic [2]. From 1980 to 2014, the total number of subjects with diabetes has quadrupled [3, 4]. More than 70% of global mortality is attributed to non-communicable diseases, including diabetes [5, 6]. Diabetes is the ninth leading cause of death [7], and in 2017, it caused one death every eight seconds (2.1 and 1.8 million in women and men aged 20–79 years, respectively) [2]. On average, healthcare expenditures for diabetic subjects are two-fold higher than those without diabetes [2]; in addition, approximately 79.4% of people with diabetes live in low- and middle-income countries [8]. Hyperglycemia is the third leading modifiable cause of death after high blood pressure and tobacco use [3]. A better understanding of the pathophysiology of type 2 diabetes (T2D) provides Corresponding author Asghar Ghasemi: Endocrine Physiology Research Center, Research Institute for Endocrine Sciences, Shahid Beheshti University of Medical Sciences, Tehran, Iran; [email protected]., No. 24, Erabi Street, Velenjak, Tehran, Iran; Phone: +98 21 22409309; Fax: +98 21 22416264.

*

Asghar Ghasemi, Khosrow Kashfi, Zahra Bahadoran (Eds.) All rights reserved-© 2022 Bentham Science Publishers

2 The Role of Nitric Oxide in Type 2 Diabetes

Ghasemi and Kashfi

an opportunity for revising the current therapeutic modalities in the management of T2D, from a primary glycemic control to a pathophysiological-based approach. This chapter provides essential information on glucose homeostasis and the pathophysiology of T2D. EPIDEMIOLOGY OF DIABETES Amongst adults aged 20–79 years, the worldwide prevalence of diabetes in 2019, was 9.3% (9.0% in women and 9.6% in men), and unfortunately, this is expected to rise to 10.2% (578.4 million) and 10.9% (700.2 million) in 2030 and 2045, respectively [8]. There is considerable geographical/cultural heterogeneity relating to the incidence of diabetes. For example, the crude incidence of diabetes ranges from 2.9 per 1000 population in France to 23.5 per 1000 population in the Pima Indians of the United States [9]. Also, the incidence of diabetes increases with age because of decreased ability of the β-cells to compensate for insulin resistance [10]. Major types of diabetes are type 1 and type 2. Type 1 diabetes accounts for 5-10% of all diabetes [2], and patients require insulin therapy. Type 2 diabetes, which used to be referred to as adult-onset or non-insulin-dependent diabetes, accounts for over 90–95% of all diabetes [11]; T2D is a complex metabolic disorder essentially characterized by alterations in lipid metabolism, insulin resistance, and pancreatic β-cell dysfunction [12, 13]. Worldwide, the prevalence of prediabetes is also increasing [14]. Prediabetes is defined as a state of higher than normal glycemia that does not meet the established criteria for diabetes diagnosis and includes subjects with impaired fasting glycemia (IFG), impaired glucose tolerance (IGT), or both [11]. Prediabetes can predict the risk of developing diabetes [11, 15], and in some subjects, it can be alleviated by lifestyle modifications or pharmacological interventions, such as metformin administration [16]. Table 1 summarizes some statistical data about diabetes according to the International Diabetes Federation (IDF) report. Table 1. Diabetes: Global statistics overview*. Year 2019

2030

2045†

Prevalence of diabetes % (million)

9.3% (463.0)

10.2% (578.4)

10.9% (700.2)

Prevalence of impaired glucose tolerance % (million)

7.5% (373.9)

8.0% (453.8)

8.6% (548.4)

Attributable all-cause mortality to diabetes (million)

4.2

-

-

Pathophysiology of T2D

The Role of Nitric Oxide in Type 2 Diabetes 3

(Table 1) cont.....

Year Healthcare expenditure for diabetes (USD billion)

760.3

824.7

845.0

* According to the International Diabetes Federation (IDF) [8] † Estimated values; total world population was 7.7 billion in 2019 and is estimated to be 8.6 and 9.5 billion in 2030 and 2045, of whom 5.0, 5.7, and 6.4 billion are aged 20-79 years.

DIAGNOSIS OF DIABETES Diabetes is diagnosed using glucose-based criteria, i.e., fasting plasma glucose (FPG) levels or 2-h plasma glucose (2-hPG) levels during a 75-g oral glucose tolerance test; hemoglobin A1c (HbA1C) levels are also used as an indicator [11, 17]. Table 2 provides diagnostic criteria for T2D according to the World Health Organization (WHO) and the American Diabetes Association (ADA). Table 2. Diagnostic criteria of diabetes*. ADA

WHO

FPG ≥ 126 mg/dL or 2-hPG ≥ 200 mg/dL or HbA1C ≥ 6.5%

FPG ≥ 126 mg/dL or 2-hPG ≥ 200 mg/dL or HbA1C ≥ 6.5%

IFG

FPG: 100–125 mg/dL

FPG: 110–125 mg/dL

IGT

2-hPG: 140–199 mg/dL

2-hPG: 140–199 mg/dL

HbA1C

5.6–6.5%

–

Diabetes

Prediabetes

* According to World Health Organization (WHO) and American Diabetes Association (ADA) criteria [11, 17]. 2-hPG, 2-h plasma glucose; FPG, fasting plasma glucose; HbA1C, glycated hemoglobin; IFG, impaired fasting glucose; IGT, impaired glucose tolerance. To convert glucose concentration from mg/dL multiplied by 0.05551.

GLUCOSE HOMEOSTASIS Maintaining blood glucose concentrations within a physiologic range, either in a fasted state or excess nutrient availability, is essential for keeping normal bodily functions [18]. This critical homeostasis is achieved through a complex network involving hormones and neuropeptides released mainly from the brain, pancreas, liver, intestine, adipose tissue, and skeletal muscle [19]. Nutrient sensing and hormonal signaling regulate glucose homeostasis, controlling tissue-specific glucose utilization and production [18]. With the use of homeostatic mechanisms, the body protects itself against either hyperglycemia (and its complications, i.e., retinopathy, neuropathy, nephropathy, premature atherosclerosis, diabetic ketoacidosis, and hyperosmolar hyperglycemic state) or

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hypoglycemia, which can cause cardiac arrhythmias, neurological dysfunction, coma, and death [20]. Fig. (1) shows how circulating glucose concentrations are determined by the balance changes of plasma glucose concentrations in normal subjects.

Fig. (1). Variations of plasma glucose concentrations in normal subjects. Normal range of circulating fasting glucose concentration is 70-100 mg/dL [21]. Plasma glucose concentrations range from a minimum of 55 mg/dL during fasting to a maximum of 160 mg/dL after a meal [20, 22, 23], and its daily average is ~85-90 mg/dL [22, 24] as shown by blue point. The glucose concentration at which glucose first appears in the urine (the renal threshold for glucose) occurs at a venous plasma glucose concentration of ~180 mg/dL [25]. To convert glucose concentration from mg/dL multiplied by 0.05551. Created with BioRender.com.

POST-ABSORPTIVE STATE: THE FASTING STATE As shown in Fig. (2) in the post-absorptive state (i.e., 12-16 h after the last meal), the rate of endogenous glucose production (EGP) is about 1.8–2 mg/kg/min (1011 μmol/kg/min) in humans and is equal to the rate of basal glucose utilization

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[20, 26, 27]; this compares with maximal insulin-stimulated glucose utilization that is ~10-11 mg/kg/min [28]. Rate of EGP in post-absorptive state is about 10% lower in elderly (75±4 y) than young (24±3 y) subjects (2.18 vs. 2.41 mg/kg/min) [29].

Fig. (2). Glucose homeostasis in the fasted state. Endogenous glucose production (EGP), mainly by the liver and to a lesser extent by the kidney, is precisely matched with glucose utilization. Hepatic glucose production (HGP), the primary determinant of fasting blood glucose concentration, is equally derived from glycogenolysis and gluconeogenesis. Lactate is the most important gluconeogenic substrate. After overnight fasting, ~80% of glucose is used via insulin-independent pathways, and the brain uses about half of the total glucose. Reproduced with permission and modifications from [35], Ghasemi, A and Norouzirad, R, Critical Reviews in Oncogenesis, 2019; 24(2): p. 1-10.

Glucose Production During fasting, about 75-85% of EGP (or even up to 100% in short fasting) that is about 1.8-2 mg/min, occurs in the liver and about 15% (5-20%) in the kidneys [22, 26, 30]. Hepatic glucose production (HGP) is the main determinant of fasting

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glycemia [31, 32]. The rate of liver glycogen depletion during fasting is about 100 mg/min or 9% per hour [33]; after a 48-h fasting period, all released glucose is provided through gluconeogenesis by the liver and the kidneys [20]. However, after >8 hours of fasting, gluconeogenesis progressively replaces glycogenolysis to preserve glycogen stores; and following 10-hour of fasting, gluconeogenesis and glycogenolysis account for 70% and 30% of total HGP, respectively [33]. Renal gluconeogenesis takes place in the proximal tubular cells and contributes 0, 5, and 10% to the overall glucose production after overnight fasting (10-16 h), moderate fasting (30-60 h), and prolonged fasting (>1 week), respectively [22]. In post-absorptive state, substrate for hepatic gluconeogenesis are lactate (40%), alanine (27%), glycerol (13%), glutamine (10%), and other amino acids (10%) [27]. In the case of renal gluconeogenesis, substrates include lactate (50%), glutamine (20%), alanine (15%), glycerol (10%), and other amino acids (5%) [27]. Overall, the rate of glucose release into the circulation in the fasting state is about 1.8–2.0 mg/kg/min, supported by hepatic glycogenolysis (45-50% by rate of 0.80.9 mg/kg/min), hepatic gluconeogenesis (25-30%, 0.45-0.55 mg/kg/min), and renal gluconeogenesis (20-25%, 0.35-0.45 mg/kg/min) [20]. Glucose Utilization In the fasted state, glucose utilization (~1.8-2.0 mg/kg/min), which is mainly insulin-independent, mostly occurs in the brain (40-45%), muscle (15-20%), liver (10-15%), gastrointestinal tract (5-10%), and kidney (5-10%) Fig. (2). In the basal state, the central nervous system accounts for a large percentage of glucose utilization [29]. In both absorptive and post-absorptive states, the brain utilizes glucose at a rate of 1-1.2 mg/kg/min, mostly insulin-independent [26] and, therefore, is not affected by diabetes [26]. Because of low plasma insulin concentration in the fasted state (5-10 μU/mL), skeletal muscle glucose uptake during fasting is low and insulin-independent [34]. In the post-absorptive state, glucose taken up by tissues is completely oxidized to CO2 or released back into the circulation as lactate, alanine, and glutamine to participate in gluconeogenesis, and there is no net storage of glucose [27]. POST-PRANDIAL STATE For 4-6 h on three occasions in a day, most people are in the post-prandial state [20]. During the post-prandial period, digested nutrients are the major source of circulating glucose [36]. Following glucose ingestion, circulating glucose levels peak in 60-90 minutes and return to basal levels within 3-4 h [20]. During the post-prandial period, HGP decreases by about 67-80%, but renal glucose release increases [27, 37]. After a meal, EGP is decreased by ~61%, with hepatic

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glycogenolysis ceasing for 4-6 h to replenish hepatic glucose stores and limit post-prandial hyperglycemia [20]. Hepatic gluconeogenesis decreases by ~82%, and glucose generated by gluconeogenesis is largely converted to glycogen [20]. Renal gluconeogenesis increases by about 2-fold and is responsible for approximately 60% of EGP, probably to facilitate efficient repletion of hepatic glycogen stores [20]. In summary, EGP decreases to ~0.8 mg/kg/min after a meal, of which 60% is produced by renal gluconeogenesis and 40% by liver gluconeogenesis. Post-prandial glucose utilization rate is ~10 mg/kg/min and mostly insulindependent [20]. In post-prandial state, glucose uptake are 30-35% in skeletal muscle, 25-30% in liver, 10-15% in gastrointestinal tract, 10-15% in kidney, 10% in brain, 5% in adipose tissue, and 5-10% in the other tissues (e.g., skin, blood cells) [20, 26]. After a meal, the skeletal muscles take up 80-90% of the available glucose, thus representing a major site of uptake [26, 34]. Of the glucose taken up by the skeletal muscle, about 70% is converted to glycogen, and approximately 30% enters glycolysis, of which 90% represents glucose oxidation, and 10% goes towards lactate release [34]. Of ingested glucose, ~45% is converted to glycogen in the splanchnic tissues, 27% is taken up by skeletal muscle and converted to glycogen, 15% is taken up by the brain, 5% by the adipose tissue, and 8% by the kidneys [20, 27]. However, splanchnic glucose uptake after oral glucose has been estimated to be from < 25% to 60% [37]. In fact, about 30% of ingested glucose is extracted by splanchnic tissues. Of 70% of which enter the systemic circulation, about 21% is extracted by the liver, 40% is taken up by the skeletal muscle, 21% by the brain, 11% by the kidneys, and 7% by the adipose tissue [27]. MECHANISMS UNDERLYING GLUCOSE HOMEOSTASIS Glucose homeostasis is regulated by peripheral and central mechanisms [38], balancing glucose production and utilization. As shown in Table 3., glucosesensing cells are found in the taste buds of the tongue, intestinal and pancreatic endocrine cells, and the CNS [39]. Integrated information received from these cells is used to control glucose homeostasis and maintain normoglycemia [39]. Central Mechanisms of Glucose Homeostasis In the mid-19th century, Claude Bernard showed that brain stimulation of the fourth ventricle increases plasma glucose levels [41]. Glucose-sensing neurons are mostly found in the hypothalamus and the brain stem [39]; the hypothalamus is the brain region that contributes the most to glucose homeostasis [41].

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Table 3. Distribution of glucose-sensing cells [39, 40]. Arcuate nucleus (ARC) Ventromedial nucleus (VMN) Hypothalamus

Lateral hypothalamus (LH) Dorsomedial hypothalamus (DMH) Paraventricular nucleus (PVN) Dorsal motor nucleus of the vagus (DMNX)

Central locations (CNS)

Dorsal vagal complex

The nucleus tractus salitarius (NTS) Area postrema (AP)

Brainstem

A1/C1 catecholaminergic neurons Basolateral medulla (BLM)

Rostral ventrolateral medulla (RVLM) raphe pallidus (RP)

Locus coeruleus (LC) Parabrachial nucleus (PBN) Other Peripheral locations

Tanycytes Pancreatic β-cells Hepatoportal vein area

Amongst the nuclei of the hypothalamus, the arcuate nucleus (ARC), ventromedial nucleus (VMN), and lateral hypothalamic (LH) nucleus have the most important roles in glucose regulation [39, 41]. In the brainstem, dorsal vagal complex [area postrema (AP), the nucleus tractus salitarius (NTS), and the dorsal motor nucleus of the vagus (DMNX)], and ventral part of medulla or basolateral medulla (BLM) express glucose-sensing neurons [39]. Glucose sensing by the brain occurs through glucose-excited (GE) and glucoseinhibited (GI) neurons [39, 41]. GI neurons are mostly found in the medial ARC, whereas GE neurons are mostly found in lateral ARC [41]. An increase in extracellular glucose concentration leads to an increase in the firing of GE neurons and a decrease in the firing of GI neurons [39, 41]. Brain glucose levels usually are 20-30% lower than that in the plasma, and compared to the other regions of the brain, GE neurons in ARC are exposed to higher glucose levels [41]. Glucose-sensing neurons in the hypothalamus and brainstem control the activity of peripheral organs involved in glucose homeostasis, including the liver, adipose tissue, muscles, and pancreatic islets through the activity of the autonomic nervous system (ANS) [39, 40, 42].

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Pancreatic islets are richly innervated by sympathetic and parasympathetic nervous systems [19, 39, 40]. Nerve fibers from hypothalamic nuclei, PBN, LC, and BLM, reach the intermediolateral cell column of the spinal cord, from which sympathetic efferents project to the peripheral organs [39]. Increased sympathetic activity stimulates glucagon secretion, inhibits insulin secretion, enhances lipolysis in white adipose tissue (WAT), increases thermogenesis in brown adipose tissue (BAT), stimulates epinephrine secretion by the adrenals, and regulates hepatic glucose output [39]. Norepinephrine/epinephrine inhibits insulin secretion by activating α2-adrenergic receptors in the β-cells and stimulates glucagon secretion by activating β2-adrenergic receptors in the α-cells [40]. Parasympathetic efferents originate from DMNX and are controlled by NTS and some hypothalamic nuclei [39]. Parasympathetic stimulation increases insulin secretion from the β-cells in hyperglycemic conditions and increases glucagon secretion during hypoglycemia [40]. The effect of parasympathetic activation in increasing insulin secretion from the β-cells is achieved via type 3 muscarinic acetylcholine receptor activation by acetylcholine (ACh); neuropeptides released from parasympathetic endings, including vasoactive intestinal peptide (VIP), pituitary adenylate-cyclase activating peptide (PACAP), and gastrin-releasing peptide (GRP) potentiate the ACh effects [40]. Increased parasympathetic activation also stimulates β-cell proliferation [40]. Glucose Sensing by Neurons High glucose levels depolarize GE neurons [42]. In GE neurons, glucose sensing is similar to that in the pancreatic β-cells in which glucose enters the cell via glucose transporter (GLUT)-2 (GLUT-2) and is phosphorylated by glucokinase (hexokinase IV) [39]. A high ATP/ADP ratio closes KATP channels and causes membrane depolarization, facilitating Ca2+ entry through voltage-dependent calcium channels [39]. Low glucose levels depolarize GI neurons [42]. In GI neurons, hypoglycemia decreases ATP production, which in turn decreases the activity of Na+/K+–ATPase and causes membrane depolarization through increased intracellular Na+ and closure of the cystic fibrosis transmembrane regulator (CFTR) chloride channels [39]. Hypoglycemia also activates AMPactivated protein kinase (AMPK), which suppresses CFTR activity; AMPK activates the NO-cGMP pathway, further activating the AMPK [39]. Peripheral Mechanisms of Glucose Homeostasis The pancreas contributes to glucose homeostasis mainly through the secretion of insulin and glucagon [19]. Between meals, when blood glucose levels are low, increased glucagon secretion promotes glycogenolysis and stimulates hepatic and renal gluconeogenesis during prolonged fasting [19]. In the fed state, increased

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circulating insulin alongside a decrease in circulating glucagon decreases EGP and promotes glucose utilization [22, 26]. About half of HGP suppression following a meal is due to stimulation of insulin secretion, and the other half is due to inhibition of glucagon secretion, indicating the importance of the insulinto-glucagon ratio [24]. Following glucose ingestion, plasma insulin increases by 4-fold, and plasma glucagon decreases by 50% [20]. Only 30% of glucose disposal is insulin-dependent in the post-absorptive state, increasing to 85% in the post-prandial state [43]. Insulin increases muscle and adipose tissue clearance rate by 10-fold [33]. The principal fuel source of skeletal muscle is free fatty acids (FFA) and glucose in fasted and fed states, respectively; the ability of the skeletal muscle to change oxidation pattern is termed metabolic flexibility [34, 43]. Insulin also promotes glycogenesis, lipogenesis, and protein synthesis [19]. INSULIN Insulin Secretion The human pancreas weighs around 90 g and contains about one million islets, each of which has ~1000 β-cells, and its insulin content is about 200-250 units [44, 45]. Each β-cell has 5-10,000 dense-core granules containing insulin, and each granule has ≥300,000 molecules of insulin [45]. Even in normoglycemic subjects, the β-cell number varies from 0.3-2.0% of the pancreatic mass [45]. Under physiological conditions, with maximal glucose concentrations, only a fraction of the granules release their insulin, estimated to be around 2%/hour [45]. Basal insulin secretion accounts for approximately 50% of insulin secretion [31], and the remainder is secreted in response to increased portal plasma glucose levels following a meal [31]. Insulin secretion in response to hyperglycemia is biphasic [2, 45]; a nadir follows the first phase, which lasts for 3-10 min and then the second phase gradually increases, lasting 60 min or more [45]. The first phase of glucose-induced insulin secretion (GSIS) is a measure of the β-cell function [46] and is preferentially impaired in T2D [45, 47] or is almost abolished [2, 48]. The second phase of insulin secretion also decreases in T2D [2]. Mechanism of Insulin Secretion As shown in Fig. (3), glucose enters the β-cells via GLUT2 and is phosphorylated to glucose-6-phosphate by GK. Following glycolytic and oxidative glucose metabolism, the ATP/ADP ratio increases and closes the KATP channels; this results in depolarization and opening of the voltage-dependent calcium channels, and calcium entry is followed by insulin secretion [45].

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Fig. (3). A schematic illustration representing the mechanism for insulin secretion in pancreatic β-cells. Glucose enters the cell primarily by glucose transporter-2 (GLUT-2) and to a lesser extent by GLUT-1 and GLUT-3 (step 1) and is converted to glucose-6-phosphate by glucokinase (step 2). Glucose metabolism increases ATP/ADP ratio in the cytoplasm (step 3), which closes the ATP-dependent potassium channels (KATP) and depolarizes the cell membrane (step 4). Depolarization opens voltage-dependent calcium channels (VDCC) and causes Ca2+ entry (step 5) that facilitates insulin secretion by exocytosis (step 6). Created with BioRender.com.

GLUT2, located within the pancreatic β-cell membrane, has a high Km for glucose (15-20 mM) [49], allowing for rapid equilibration between extra- and intracellular glucose levels [45, 50]. GLUT2 has a low affinity for glucose and is not saturated even at high glucose levels [33]; therefore, hepatocytes and pancreatic β-cells that express GLUT2 experience a rise in intracellular glucose levels following increased plasma glucose and can sense glucose [33]. Under physiological conditions, the rate of glucose transport has little effect on insulin secretion [45]. In human β-cells, GLUT1 and GLUT3 are also involved in glucose entry [40, 45, 51]. Glucokinase (hexokinase IV, Km≈ 8-10 mM, 144-180 mg/dL) in the β-cells acts within the normal range of plasma glucose concentrations and phosphorylates glucose [45, 50]. Glucose phosphorylation is a critical step in controlling

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glycolytic flux, as it traps the glucose molecule within the cell by placing a charge on it; the capacity of glucose transport is higher than glucose phosphorylation [51]. KATP channels couple cell metabolism to electrical activity [52]. A KATP channel in the pancreatic β-cells has four Kir6.2 subunits and four SUR1 subunits [52, 53]. Antidiabetic drugs such as sulfonylureas (e.g., glipalamide) and glinides (e.g., repaglinide) inhibit KATP channels and increase insulin secretion [53]. Voltagedependent calcium channels that are found in the pancreatic β-cells are L-type calcium channels (CaV1.2 and CaV1.3), P/Q-type channels (CaV2.1), and T-type channels (CaV3.2) [53]. In addition to triggering the insulin secretion pathway described above, glucose can activate a metabolic amplifying pathway whereby it modulates insulin secretion independently from its action on KATP channels by generating signals (NADPH, hormones, neurotransmitters) that amplify the action of Ca2+ on insulin granule exocytosis, provided that Ca2+ influx is already stimulated and [Ca2+]i is high [54]. Box 1 Circulating Insulin Concentrations Basal (fasting) insulin levels is about 11 µU/mL [24] or 2-12 µU/mL [55]. The insulin concentration in portal blood is approximately two-fold higher than peripheral circulation because of hepatic clearance of insulin [31]. The half-life of insulin is about 5 min in the blood, and insulin is degraded by insulin-degrading enzymes mostly in the liver (~80%) and kidney (~20%) as well as also in other tissues [44, 56]. In the insulin breakdown in the liver, insulin enters hepatocytes by receptor-mediated endocytosis and is degraded in the lysosomes [44]. The maximal effect of insulin on total body glucose metabolism, which includes suppression of glucose production and stimulation of glucose utilization (assessed by exogenous glucose infusion rate during euglycemic hyperinsulinemic clamp), is seen at plasma insulin concentrations between 200 and 700 μU/mL and is ~1011 mg/kg/min [28]; the half-maximal effect is observed at ~60 μU/mL [28]. In subjects with T2D, the percentage of basal insulin secretion rate relative to total insulin secretion rate increases and GSIS decreases; the ratio of GSIS to basal insulin secretion rate are 3.7 and 0.78 in lean healthy and diabetic subjects, respectively [57]. Glucose production is more sensitive than glucose utilization to plasma insulin levels [28, 33]; plasma insulin levels for half-maximal suppression of glucose production (30 μU/mL) is approximately half of those for halfmaximal stimulation of glucose utilization (60 μU/mL) [28]. Insulin completely blocks glucose production at a plasma concentration of 50-60 μU/mL [28]. A 1020 μU/mL increment of plasma insulin concentrations (from basal insulin levels

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11±1 μU/mL) can cause half-maximal suppression of glucose production, whereas a 40-50 μU/mL increment is needed for half-maximal stimulation of glucose utilization [28]. 10-15 µU/mL (60-90 pM) of serum insulin could prevent hydrolysis of triglycerides [31]. EC50 of plasma insulin concentrations for decreasing plasma non-esterified fatty acids is ~20 μU/mL [58]. Hepatic insulin resistance and hepatic glucose resistance cause fasting plasma insulin concentration to be higher in type 2 diabetic subjects [26]. EC50 of plasma insulin concentrations for glucose uptake in skeletal muscle is ~60 μU/mL in healthy subjects and much higher (~120-140 μU/mL) in type 2 diabetic subjects [34]. ED50 of portal insulin concentration to inhibit HGP in the basal state is higher in type 2 diabetic subjects than normal subjects, indicating hepatic insulin resistance in type 2 diabetic subjects with mild fasting hyperglycemia [59]. It has been reported that when plasma insulin concentration is < 50 μU/mL, impaired suppression of HGP compared to decreased glucose uptake, contributes more quantitatively to disturbed glucose homeostasis [59]. Box 2 Technical Considerations on Circulating Insulin Measurement For interpreting circulating insulin levels, two technical points need to be considered: (1) assay-dependent variability and (2) converting insulin values from the bioefficacy-based traditional unit (µU/mL) to mass-based SI (Système International) unit (pM) [60]. Currently, there is no standard method for insulin measurement; in addition, circulating insulin assay using different methods shows ~2-fold difference [61]; this point should be considered in the interpretation and comparison of circulating insulin levels [61]. Converting insulin values from conventional (µU/mL) to SI (pM) units is a challenging issue, and conversion factors range from 5.99-7.174 [62 - 65]. Based on the molecular weight of human insulin (5808) and potency of insulin standard (24 U/mg, 4th International Standard of Insulin, 1959), it was concluded that 1 unit of insulin equals 7.174 nmol (yielding a conversion factor of 7.174) [63]. Since insulin standard contains some water and salts, using quantitative amino acid analysis and the potency of an insulin standard of 26 U/mg (WHO, 1987), it was concluded that 1 unit of insulin equals 6 nmol (yielding a conversion factor of 6.00) [63], which translates to 28.696 U/mg pure insulin [66]. Compared to the new conversion factor of 6.00, recommended by the ADA [62, 67], using other conversion factors including 7.174 and 6.945, which is recommended by the American Medical Association [62], ~20% and ~15% higher insulin values are obtained, respectively [63, 67], a factor that itself contributes to inter-assay variation [68] and potential clinical implications [60]. A commentary by Knopp et al. states that the correct conventional factor for human insulin is 1 μU/mL=6.00 pM [60].

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Insulin Signaling Pathways Insulin receptors are found in the membranes of almost all mammalian cells [31]. The number of insulin receptors varies between < 50 per erythrocyte to > 20,000 on hepatocytes [31]. Maximal effects of insulin on glucose production and glucose utilization occur at 11% and 49% of insulin receptor occupancy, suggesting the presence of spare insulin receptors in humans [28].

Fig. (4). Insulin signaling pathways. IRS, insulin receptor substrate; PI3K, Phosphatidyl inositol-3 kinase; Akt, thymoma in AK (aphakia) mice; PKB, protein kinase B; Grb2, growth factor receptor binding protein-2; SOS, son of sevenless; Ras, Rat sarcoma; Raf, Raf fibrosarcoma; MEK, mitogen-activated ERK (extracellular-regulated kinases) kinase; MAPK, mitogen-activated protein kinase. Created with BioRender.com.

Insulin receptor, a receptor tyrosine kinase (RTK), is a tetrameric protein that has two extracellular α-subunits and two intracellular β-subunits [69]. In the absence of insulin, the α-subunit inhibits the intrinsic tyrosine kinase activity of the βsubunit [69]. Following the binding of insulin to α-subunits of the insulin receptor, the intracellular tyrosine kinase domains on the β-subunits of insulin receptor are activated, causing intramolecular autophosphorylation or transphosphorylation in which each β-subunit phosphorylates tyrosine residues on other β-subunit [24, 70 - 72]. Then, insulin receptor substrate (IRS) proteins bind to phosphotyrosine residues on the receptor and themselves are phosphorylated

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[24]. Phosphorylated IRS proteins activate two main insulin signaling pathways: (1) phosphatidylinositol 3-kinase (PI3K)-Akt pathway and (2) Ras (rat sarcoma) mitogen-protein kinase (MAPK) pathway Fig. (4) [24]. PI3K is a heterodimer consisting of a catalytic subunit (p110) and an SH2containing regulatory subunit (p85) [69, 72]. PI3K binds to the phosphorylated IRS proteins via its regulatory subunit; then, the catalytic subunit of PI3K converts plasma membrane phosphatidylinositol 4,5 bisphosphate (PIP2) to phosphatidylinositol 3,4,5 triphosphate (PIP3), which is a lipid second messenger [69]. PIP3activates 3-phosphoinositide-dependent protein kinase 1 (PDK1), which in turn activates PKB (Akt) [69]. The insulin's metabolic actions are mainly achieved through the PI3K/Akt pathway [70, 72, 73]. These actions include promotion of glucose uptake in myocytes and adipocytes, suppression of gluconeogenesis in hepatocytes, increase in glycogen synthesis, and inhibition of lipolysis [70]. In T2D, the ability of insulin to phosphorylate IRS-1 is impaired [24]. The other pathway for insulin action, the MAPK pathway, is mainly involved in nonmetabolic processes such as growth and cellular proliferation [24, 70, 72]; this pathway retains its sensitivity and its excessive stimulation during insulin resistance involved in inflammation and atherogenesis [24]. Insulin signaling is complex, and the number of signaling combinations of signaling molecules probably exceeds 1000; in most cases of insulin resistance, there is partial resistance in some but not all insulin signaling pathways [72, 74]. To review the pertinent timeline for key events in insulin signaling, see Ref [71], and for a more comprehensive review on insulin signaling pathways, see Ref [72]. Pathophysiology of Type 2 Diabetes As shown in Fig. (5), lifestyle and genetic predisposition play important roles in the development of T2D [75]. In addition, microbiota, the assemblage of living microorganisms in a defined environment, is associated with T2D and dysbiosis; change in healthy microbiota can influence the development of T2D [76]. Risk factors of T2D can be categorized as genetic, metabolic, and environmental risk factors [77]. Obesity, aging, economic development, sedentary lifestyle, urbanization, unhealthy and energy-dense diets, family history of diabetes in firstdegree relatives, history of cardiovascular diseases, hypertension, polycystic ovary syndrome in women, pregnancy, smoking, stress, and dyslipidemia are among the risk factor for T2D [2, 7, 11, 78]. Some of these (e.g., genetic predisposition, ethnicity, and family history of diabetes) are non-modifiable risk factors. In contrast, most of them (e.g., obesity, low physical activity, and unhealthy diet) are modifiable risk factors [77].

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Fig. (5). Developing type 2 diabetes, which presents the core pathophysiology of type 2 diabetes, i.e., β-cell dysfunction and insulin resistance. The pathogenesis of T2D previously was focused on the liver, muscle, and β-cell functional impairment, the so-called triumvirate impairment [58]. After that, the other contributors to hyperglycemia were introduced, and the “ominous triumvirate” was extended to “ominous octet” [26, 32]. According to “ominous octet,” the hyperglycemia in T2D is due to decreased insulin secretion, increased glucagon secretion, increased HGP, decreased skeletal muscle glucose uptake, increased renal glucose reabsorption, increased lipolysis (mostly in adipose tissue), decreased incretin effect, and neurotransmitter dysfunction in the brain [26]. Increased inflammation, hypoxia, increased oxidative stress, and endothelial dysfunction is also involved in the pathogenesis of T2D [26, 51, 83] See Fig. (6). Created with BioRender.com.

Hallmarks characterizing the pathophysiology of T2D include insulin resistance, β-cell defects, and hyperglycemia [48, 79 - 81]. Most treatments for T2D currently target decreasing insulin resistance or increasing β-cell function [48]. In response to insulin resistance, β-cells show adaptive responses and stave off progression to T2D [48]. Following the failure of adaptive responses of β-cells, T2D develops [48, 82]. In adults, compensation is primarily due to increases in the secretory capacity, and there is little expansion in the number of β-cells [45]. Decompensation is due to decreased β-cell mass and function [45, 48]; see Fig. (6). Insulin Resistance Insulin responsiveness is defined as the maximal effect of insulin (Vmax), and insulin sensitivity is defined as the insulin concentration that is required for a half-maximal response (EC50/ED50) [84]. Defects within the insulin receptor reduce insulin sensitivity, while defects associated with post-receptor pathways decrease responsiveness [31]. Decreased sensitivity to insulin shifts the insulin dose-response curve to the right, and decreased responsiveness to insulin can cause decreases in the biological effects of insulin at a given insulin concentration [28], which is well-known as insulin resistance [84]. The previous definition of insulin resistance (greater than normal amounts of insulin are required for normal response to inulin) had changed to: in insulin resistance, normal insulin levels produce a less than normal

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biological response [31]. In insulin resistance, biological effects of endogenous or exogenous insulin, including effects on glucose, lipid, and protein metabolism, are reduced [31, 43]. Endothelial dysfunction Oxidative stress Hypoxia Inflammation

?

Pncreatic β-cell (↓Insulin secretion) Adipose tissue (↑Lipolysis)

Hyperglycemia Brain (Neurotransmitter dysfunction) Liver Skeletal muscle (↓Glucose uptake) (↑Glucose production)

Kidney (↑Glucose reabsorption)

Gastrointestinal system (↓Incretin effect)

Pancreatic α-cell (↑Glucagon secretion)

Fig. (6). Pathogenesis of type 2 diabetes from ominous triumvirate to ominous octet and beyond. The Figure indicates that in addition to β-cell dysfunction and (hepatic and skeletal muscle) insulin resistance that represent core pathophysiological defects in type 2 diabetes, defects in other organs are also involved in the pathophysiology of the disease. Reproduced with permission from [35], Ghasemi, A and Norouzirad, R, Critical Reviews in Oncogenesis, 2019; 24(2): p. 1-10.

Despite the traditional view that insulin-resistant organs in diabetes are the liver, muscle, and adipose tissue [74], the main insulin-sensitive tissues [30], insulin resistance in T2D is not limited to insulin-sensitive tissues. It includes the brain [32, 85], the endothelium [86, 87], and the pancreatic β-cells [82]. Besides, all insulin effects and tissues are not equally affected by insulin resistance [72]. Emerging evidence suggests that insulin resistance should be tissue-specific rather

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than a uniform systemic alteration [88]. Accordingly, some mathematical models have also been provided to clarify tissue-specific contributions in general insulin resistance [89]. A brief overview of insulin resistance in different organs is presented in Fig. (7).

Fig. (7). Insulin resistance in different tissues and its related disorders in type 2 diabetes [24, 26, 30, 34, 43, 72, 73, 85, 90 - 92]. eNOS, endothelial nitric oxide synthase; FFA, free fatty acid; HPG, hepatic glucose production; TG, triglycerides. Created with BioRender.com.

β-cell Dysfunction There is currently no consensus as to what the definition of a β-cell should be. Traditionally, it has been defined as a cell synthesizing, processing, packaging, and secreting insulin in response to elevated blood glucose [10]. The identity of a mature β-cell is determined according to the expression of a set of genes and the repression of another set of genes (called disallowed genes) [10]. The β-cell function is regulated by metabolic, neural, and hormonal factors, but glucose is the most important [54]. Insulin secretion from β-cells is dependent on an absolute number of the β-cells (β-cell mass) and the output from each (β-cell function)

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[48]. Decreased β-cell function is the key problem in T2D; decreased β-cell mass may also contribute to the pathogenesis of T2D [2, 10]; up to 24-65% decrease in β-cell mass has been reported in T2D, mostly due to β-cell apoptosis [2, 48]. However, according to some calculations, it has been estimated that only 40% of the β-cell mass is sufficient to maintain normal glycemia in nondiabetic subjects [2]. In addition, restoring GSIS and circulating glucose following bariatric surgery, calorie restriction, and GLP-1 administration [2, 81] indicates that β-cell mass and insulin content is not severely reduced, and β-cell dysfunction seems to be the prime cause of the T2D [2]. It seems that β-cell dysfunction is, at least in some cases, a reversible phenomenon [10]. Although physiological glucose concentrations are needed for preserving optimal β-cell function, prolonged or repeated exposure of the β-cells to high glucose concentrations (called glucotoxicity) causes β-cell dysfunction [54]. Chronic hyperglycemia, that is, plasma glucose levels of 126 mg/dL, exposes the β-cells to a chronically stimulated state [57]. In addition, glucose has permissive effects on harmful actions of FFA, and hyperglycemia can unveil the harmful effects of fatty acids that are called glucolipotoxicity [54], which contributes to the development of T2D [10]. Prolonged hyperglycemia causes loss of β-cell-defining transcription factors such as Pdx1 (pancreatic and duodenal homeobox 1) and MafA (musculoaponeurotic fibrosarcoma oncogene family, A), a process called dedifferentiation or loss of β-cell identity [10, 48]. In dedifferentiation, mature βcells attain a mesenchymal cell phenotype with potential redifferentiation to β-cell [82]. Dedifferentiation is defined as an altered phenotype that leads to decreased optimal performance, including insulin secretion [10], and is an underlying mechanism for β-cell dysfunction in T2D [48]. About 30% of β-cells in type 2 diabetic subjects are dedifferentiated β-cells [82]. It has been proposed that hypersecretion is the main driver of β-cell dysfunction [57]. Despite the common belief that IR is the evil force that causes β-cell dysfunction [93], it has been proposed that hyperinsulinemia causes insulin resistance by insulin-induced receptor downregulation and increased lipogenesis [57], which contributes to the expansion of visceral fat mass [93]. CONCLUDING REMARKS Diabetes is a leading cause of morbidity and mortality worldwide. Available treatments of T2D mainly aim to decrease insulin resistance or increase β-cell function. Despite recent advances that have been made in treating T2D, its control has been relatively poor. This issue warrants the development of new therapeutic strategies, which in turn is dependent on a better understanding of the pathogenesis of this complex disorder. Treatment approaches need to be

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reconsidered to change from a glycemic control approach to a pathophysiologicalbased one. Even the insulin-centric view of metabolic homeostasis is incomplete. CONSENT FOR PUBLICATION Permission from Begell House Inc. for Figures 2 and 6. CONFLICT OF INTEREST The author declares no conflict of interest, financial or otherwise. ACKNOWLEDGEMENT Declared none. REFERENCES [1]

Zimmet PZ. Diabetes and its drivers: the largest epidemic in human history? Clin Diabetes Endocrinol 2017; 3(1): 1. [http://dx.doi.org/10.1186/s40842-016-0039-3] [PMID: 28702255]

[2]

Ashcroft FM, Rorsman P. Diabetes mellitus and the β cell: the last ten years. Cell 2012; 148(6): 116071. [http://dx.doi.org/10.1016/j.cell.2012.02.010] [PMID: 22424227]

[3]

Yates T, Khunti K. The diabetes mellitus tsunami: worse than the ‘Spanish flu’ pandemic? Nat Rev Endocrinol 2016; 12(7): 377-8. [http://dx.doi.org/10.1038/nrendo.2016.74] [PMID: 27199294]

[4]

Zhou B, Lu Y, Hajifathalian K, et al. Worldwide trends in diabetes since 1980: a pooled analysis of 751 population-based studies with 4·4 million participants. Lancet 2016; 387(10027): 1513-30. [http://dx.doi.org/10.1016/S0140-6736(16)00618-8] [PMID: 27061677]

[5]

Blüher M. Obesity: global epidemiology and pathogenesis. Nat Rev Endocrinol 2019; 15(5): 288-98. [http://dx.doi.org/10.1038/s41574-019-0176-8] [PMID: 30814686]

[6]

Allen L. Are we facing a noncommunicable disease pandemic? J Epidemiol Glob Health 2016; 7(1): 5-9. [http://dx.doi.org/10.1016/j.jegh.2016.11.001] [PMID: 27886846]

[7]

Zheng Y, Ley SH, Hu FB. Global aetiology and epidemiology of type 2 diabetes mellitus and its complications. Nat Rev Endocrinol 2018; 14(2): 88-98. [http://dx.doi.org/10.1038/nrendo.2017.151] [PMID: 29219149]

[8]

International Diabetes Federation. https://www.diabetesatlas.org

[9]

Jaacks LM, Siegel KR, Gujral UP, Narayan KMV. Type 2 diabetes: A 21st century epidemic. Best Pract Res Clin Endocrinol Metab 2016; 30(3): 331-43. [http://dx.doi.org/10.1016/j.beem.2016.05.003] [PMID: 27432069]

[10]

Christensen AA, Gannon M. The Beta Cell in Type 2 Diabetes. Curr Diab Rep 2019; 19(9): 81. [http://dx.doi.org/10.1007/s11892-019-1196-4] [PMID: 31399863]

[11]

American Diabetes Association. Classification and Diagnosis of Diabetes: Standards of Medical Care in Diabetes—2019. Diabetes Care 2019; 42 (Suppl. 1): S13-28. [http://dx.doi.org/10.2337/dc19-S002] [PMID: 30559228]

IDF

Diabetes

Atlas

2019.

Available

at:

Pathophysiology of T2D

The Role of Nitric Oxide in Type 2 Diabetes 21

[12]

Gheibi S, Kashfi K, Ghasemi A. A practical guide for induction of type-2 diabetes in rat: Incorporating a high-fat diet and streptozotocin. Biomed Pharmacother 2017; 95: 605-13. [http://dx.doi.org/10.1016/j.biopha.2017.08.098] [PMID: 28881291]

[13]

Podell BK, Ackart DF, Richardson MA, DiLisio JE, Pulford B, Basaraba RJ. A model of type 2 diabetes in the guinea pig using sequential diet-induced glucose intolerance and streptozotocin treatment. Dis Model Mech 2017; 10(2): dmm.025593. [http://dx.doi.org/10.1242/dmm.025593] [PMID: 28093504]

[14]

Weisman A, Fazli GS, Johns A, Booth GL. Evolving Trends in the Epidemiology, Risk Factors, and Prevention of Type 2 Diabetes: A Review. Can J Cardiol 2018; 34(5): 552-64. [http://dx.doi.org/10.1016/j.cjca.2018.03.002] [PMID: 29731019]

[15]

Tabák AG, Jokela M, Akbaraly TN, Brunner EJ, Kivimäki M, Witte DR. Trajectories of glycaemia, insulin sensitivity, and insulin secretion before diagnosis of type 2 diabetes: an analysis from the Whitehall II study. Lancet 2009; 373(9682): 2215-21. [http://dx.doi.org/10.1016/S0140-6736(09)60619-X] [PMID: 19515410]

[16]

Neumiller JJ, Kalyani RR, Herman WH, et al. Evidence supports prediabetes treatment. Science 2019; 364(6438): 341-2. [http://dx.doi.org/10.1126/science.aax3548] [PMID: 31023917]

[17]

Zimmet P, Alberti KG, Magliano DJ, Bennett PH. Diabetes mellitus statistics on prevalence and mortality: facts and fallacies. Nat Rev Endocrinol 2016; 12(10): 616-22. [http://dx.doi.org/10.1038/nrendo.2016.105] [PMID: 27388988]

[18]

Sharabi K, Tavares CDJ, Rines AK, Puigserver P. Molecular pathophysiology of hepatic glucose production. Mol Aspects Med 2015; 46: 21-33. [http://dx.doi.org/10.1016/j.mam.2015.09.003] [PMID: 26549348]

[19]

Röder PV, Wu B, Liu Y, Han W. Pancreatic regulation of glucose homeostasis. Exp Mol Med 2016; 48(3): e219. [http://dx.doi.org/10.1038/emm.2016.6] [PMID: 26964835]

[20]

Gerich JE. Role of the kidney in normal glucose homeostasis and in the hyperglycaemia of diabetes mellitus: therapeutic implications. Diabet Med 2010; 27(2): 136-42. [http://dx.doi.org/10.1111/j.1464-5491.2009.02894.x] [PMID: 20546255]

[21]

Ghasemi A, Zahediasl S, Azizi F. Reference values for fasting serum glucose levels in healthy Iranian adult subjects. Clin Lab 2011; 57(5-6): 343-9. [PMID: 21755824]

[22]

Gerich JE. Control of glycaemia. Baillieres Clin Endocrinol Metab 1993; 7(3): 551-86. [http://dx.doi.org/10.1016/S0950-351X(05)80207-1] [PMID: 8379904]

[23]

Rizza RA, Gerich JE, Haymond MW, et al. Control of blood sugar in insulin-dependent diabetes: comparison of an artificial endocrine pancreas, continuous subcutaneous insulin infusion, and intensified conventional insulin therapy. N Engl J Med 1980; 303(23): 1313-8. [http://dx.doi.org/10.1056/NEJM198012043032301] [PMID: 7001229]

[24]

DeFronzo RA. Banting Lecture. From the triumvirate to the ominous octet: a new paradigm for the treatment of type 2 diabetes mellitus. Diabetes 2009; 58(4): 773-95. [http://dx.doi.org/10.2337/db09-9028] [PMID: 19336687]

[25]

Cersosimo E, Solis-Herrera C, Triplitt C. Inhibition of renal glucose reabsorption as a novel treatment for diabetes patients. J Bras Nefrol 2014; 36(1): 80-92. [http://dx.doi.org/10.5935/0101-2800.20140014] [PMID: 24676619]

[26]

Cersosimo E, Triplitt C, Solis-Herrera C, Mandarino LJ, DeFronzo RA. Pathogenesis of Type 2 Diabetes Mellitus. In: Anawalt B, Boyce A, Chrousos G, Dungan K, Grossman A, Eds. Endotext South Dartmouth (MA): MDTextcom, Inc. Feingold, KR 2000.

22 The Role of Nitric Oxide in Type 2 Diabetes

Ghasemi and Kashfi

[27]

Gerich JE. Physiology of glucose homeostasis. Diabetes Obes Metab 2000; 2(6): 345-50. [http://dx.doi.org/10.1046/j.1463-1326.2000.00085.x] [PMID: 11225963]

[28]

Rizza RA, Mandarino LJ, Gerich JE. Dose-response characteristics for effects of insulin on production and utilization of glucose in man. Am J Physiol 1981; 240(6): E630-9. [PMID: 7018254]

[29]

Robert JJ, Cummins JC, Wolfe RR, et al. Quantitative aspects of glucose production and metabolism in healthy elderly subjects. Diabetes 1982; 31(3): 203-11. [http://dx.doi.org/10.2337/diab.31.3.203] [PMID: 6759237]

[30]

Choukem SP, Gautier JF. How to measure hepatic insulin resistance? Diabetes Metab 2008; 34(6): 664-73. [http://dx.doi.org/10.1016/S1262-3636(08)74602-0] [PMID: 19195628]

[31]

Krentz A. Insulin resistance: a clinical handbook. John Wiley & Sons 2002. [http://dx.doi.org/10.1002/9780470698921]

[32]

DeFronzo RA. Current issues in the treatment of type 2 diabetes. Overview of newer agents: where treatment is going. Am J Med 2010; 123(3) (Suppl.): S38-48. [http://dx.doi.org/10.1016/j.amjmed.2009.12.008] [PMID: 20206731]

[33]

Tirone TA, Brunicardi FC. Overview of glucose regulation. World J Surg 2001; 25(4): 461-7. [http://dx.doi.org/10.1007/s002680020338] [PMID: 11344399]

[34]

Abdul-Ghani MA, DeFronzo RA. Pathogenesis of insulin resistance in skeletal muscle. J Biomed Biotechnol 2010; 2010: 1-19. [http://dx.doi.org/10.1155/2010/476279] [PMID: 20445742]

[35]

Ghasemi A, Norouzirad R. Type 2 diabetes: An updated overview. Critical ReviewsTM in Oncogenesis. 2019; 24(2): 1-10.

[36]

Kruger DF, Martin CL, Sadler CE. New insights into glucose regulation. Diabetes Educ 2006; 32(2): 221-8. [http://dx.doi.org/10.1177/0145721706286568] [PMID: 16554425]

[37]

Taylor R, Magnusson I, Rothman DL, et al. Direct assessment of liver glycogen storage by 13C nuclear magnetic resonance spectroscopy and regulation of glucose homeostasis after a mixed meal in normal subjects. J Clin Invest 1996; 97(1): 126-32. [http://dx.doi.org/10.1172/JCI118379] [PMID: 8550823]

[38]

Thorens B. Targeting the Brain to Cure Type 2 Diabetes. Diabetes 2019; 68(3): 476-8. [http://dx.doi.org/10.2337/dbi18-0051] [PMID: 30787069]

[39]

Steinbusch L, Labouèbe G, Thorens B. Brain glucose sensing in homeostatic and hedonic regulation. Trends Endocrinol Metab 2015; 26(9): 455-66. [http://dx.doi.org/10.1016/j.tem.2015.06.005] [PMID: 26163755]

[40]

Thorens B. Neural regulation of pancreatic islet cell mass and function. Diabetes Obes Metab 2014; 16(S1) (Suppl. 1): 87-95. [http://dx.doi.org/10.1111/dom.12346] [PMID: 25200301]

[41]

Güemes A, Georgiou P. Review of the role of the nervous system in glucose homoeostasis and future perspectives towards the management of diabetes. Bioelectron Med 2018; 4(1): 9. [http://dx.doi.org/10.1186/s42234-018-0009-4] [PMID: 32232085]

[42]

Pozo M, Claret M. Hypothalamic Control of Systemic Glucose Homeostasis: The Pancreas Connection. Trends Endocrinol Metab 2018; 29(8): 581-94. [http://dx.doi.org/10.1016/j.tem.2018.05.001] [PMID: 29866501]

[43]

Rachek LI. Free fatty acids and skeletal muscle insulin resistance. Prog Mol Biol Transl Sci 2014; 121: 267-92. [http://dx.doi.org/10.1016/B978-0-12-800101-1.00008-9] [PMID: 24373240]

Pathophysiology of T2D

The Role of Nitric Oxide in Type 2 Diabetes 23

[44]

Ferrannini E, Mari A. β-Cell function in type 2 diabetes. Metabolism 2014; 63(10): 1217-27. [http://dx.doi.org/10.1016/j.metabol.2014.05.012] [PMID: 25070616]

[45]

Rutter GA, Pullen TJ, Hodson DJ, Martinez-Sanchez A. Pancreatic β-cell identity, glucose sensing and the control of insulin secretion. Biochem J 2015; 466(2): 203-18. [http://dx.doi.org/10.1042/BJ20141384] [PMID: 25697093]

[46]

Burhans MS, Hagman DK, Kuzma JN, Schmidt KA, Kratz M. Contribution of Adipose Tissue Inflammation to the Development of Type 2 Diabetes Mellitus. Compr Physiol 2018; 9(1): 1-58. [http://dx.doi.org/10.1002/cphy.c170040] [PMID: 30549014]

[47]

Taylor R, Holman RR. Normal weight individuals who develop Type 2 diabetes: the personal fat threshold. Clin Sci (Lond) 2015; 128(7): 405-10. [http://dx.doi.org/10.1042/CS20140553] [PMID: 25515001]

[48]

Chen C, Cohrs CM, Stertmann J, Bozsak R, Speier S. Human beta cell mass and function in diabetes: Recent advances in knowledge and technologies to understand disease pathogenesis. Mol Metab 2017; 6(9): 943-57. [http://dx.doi.org/10.1016/j.molmet.2017.06.019] [PMID: 28951820]

[49]

Ferrannini E, Seghieri M. Overview of glucose homeostasis. In: Bonora E, DeFronzo RA, Eds. Diabetes Epidemiology, Genetics, Pathogenesis, Diagnosis, Prevention, and Treatment Endocrinology. Switzerland: Springer 2018; pp. 1-22.

[50]

Weir GC, Bonner-Weir S. Five stages of evolving beta-cell dysfunction during progression to diabetes. Diabetes 2004; 53 (Suppl. 3): S16-21. [http://dx.doi.org/10.2337/diabetes.53.suppl_3.S16] [PMID: 15561905]

[51]

Gerber PA, Rutter GA. The Role of Oxidative Stress and Hypoxia in Pancreatic Beta-Cell Dysfunction in Diabetes Mellitus. Antioxid Redox Signal 2017; 26(10): 501-18. [http://dx.doi.org/10.1089/ars.2016.6755] [PMID: 27225690]

[52]

Miki T, Nagashima K, Seino S. The structure and function of the ATP-sensitive K+ channel in insulinsecreting pancreatic beta-cells. J Mol Endocrinol 1999; 22(2): 113-23. [http://dx.doi.org/10.1677/jme.0.0220113] [PMID: 10194514]

[53]

Jacobson D, Shyng SL. Ion Channels of the Islets in Type 2 Diabetes. J Mol Biol 2019. [PMID: 31473158]

[54]

Bensellam M, Laybutt DR, Jonas JC. The molecular mechanisms of pancreatic β-cell glucotoxicity: Recent findings and future research directions. Mol Cell Endocrinol 2012; 364(1-2): 1-27. [http://dx.doi.org/10.1016/j.mce.2012.08.003] [PMID: 22885162]

[55]

Tohidi M, Ghasemi A, Hadaegh F, Derakhshan A, Chary A, Azizi F. Age- and sex-specific reference values for fasting serum insulin levels and insulin resistance/sensitivity indices in healthy Iranian adults: Tehran Lipid and Glucose Study. Clin Biochem 2014; 47(6): 432-8. [http://dx.doi.org/10.1016/j.clinbiochem.2014.02.007] [PMID: 24530467]

[56]

Binder C, Lauritzen T, Faber O, Pramming S. Insulin Pharmacokinetics. Diabetes Care 1984; 7(2): 188-99. [http://dx.doi.org/10.2337/diacare.7.2.188] [PMID: 6376015]

[57]

Erion K, Corkey BE. β-Cell Failure or β-Cell Abuse? Front Endocrinol (Lausanne) 2018; 9: 532. [http://dx.doi.org/10.3389/fendo.2018.00532] [PMID: 30271382]

[58]

Reaven GM. The fourth Musketeer — from Alexandre Dumas to Claude Bernard. Diabetologia 1995; 38(1): 3-13. [http://dx.doi.org/10.1007/BF02369347] [PMID: 7744226]

[59]

Groop LC, Bonadonna RC, DelPrato S, et al. Glucose and free fatty acid metabolism in non-insulindependent diabetes mellitus. Evidence for multiple sites of insulin resistance. J Clin Invest 1989; 84(1): 205-13.

24 The Role of Nitric Oxide in Type 2 Diabetes

Ghasemi and Kashfi

[http://dx.doi.org/10.1172/JCI114142] [PMID: 2661589] [60]

Knopp JL, Holder-Pearson L, Chase JG. Insulin Units and Conversion Factors: A Story of Truth, Boots, and Faster Half-Truths. J Diabetes Sci Technol 2018; 1932296818805074. [PMID: 30318910]

[61]

Tohidi M, Arbab P, Ghasemi A. Assay-dependent variability of serum insulin concentrations: a comparison of eight assays. Scand J Clin Lab Invest 2017; 77(2): 122-9. [http://dx.doi.org/10.1080/00365513.2016.1278260] [PMID: 28150502]

[62]

Takayama M, Yamauchi K, Aizawa T. Quantification of insulin. Diabet Med 2014; 31(3): 375-6. [http://dx.doi.org/10.1111/dme.12337] [PMID: 24147803]

[63]

Vølund A. Conversion of insulin units to SI units. Am J Clin Nutr 1993; 58(5): 714-5. [http://dx.doi.org/10.1093/ajcn/58.5.714] [PMID: 8237884]

[64]

Vølund A, Brange J, Drejer K, et al. In vitro and in vivo potency of insulin analogues designed for clinical use. Diabet Med 1991; 8(9): 839-47. [http://dx.doi.org/10.1111/j.1464-5491.1991.tb02122.x] [PMID: 1663018]

[65]

Young DS. Implementation of SI units for clinical laboratory data. Style specifications and conversion tables. Ann Intern Med 1987; 106(1): 114-29. [http://dx.doi.org/10.7326/0003-4819-106-1-114] [PMID: 3789557]

[66]

Robbins DC, Andersen L, Bowsher R, et al. Report of the American Diabetes Association’s Task Force on standardization of the insulin assay. Diabetes 1996; 45(2): 242-56. [http://dx.doi.org/10.2337/diab.45.2.242] [PMID: 8549870]

[67]

Heinemann L. Insulin assay standardization: leading to measures of insulin sensitivity and secretion for practical clinical care: response to Staten et al. Diabetes Care 2010; 33(6): e83. [http://dx.doi.org/10.2337/dc10-0034] [PMID: 20508228]

[68]

Manley SE, Stratton IM, Clark PM, Luzio SD. Comparison of 11 human insulin assays: implications for clinical investigation and research. Clin Chem 2007; 53(5): 922-32. [http://dx.doi.org/10.1373/clinchem.2006.077784] [PMID: 17363420]

[69]

Taniguchi CM, Emanuelli B, Kahn CR. Critical nodes in signalling pathways: insights into insulin action. Nat Rev Mol Cell Biol 2006; 7(2): 85-96. [http://dx.doi.org/10.1038/nrm1837] [PMID: 16493415]

[70]

Kadowaki T, Ueki K, Yamauchi T, Kubota N. SnapShot: Insulin signaling pathways. Cell. 2012; 148(3): 624.

[71]

Cohen P. The twentieth century struggle to decipher insulin signalling. Nat Rev Mol Cell Biol 2006; 7(11): 867-73. [http://dx.doi.org/10.1038/nrm2043] [PMID: 17057754]

[72]

Biddinger SB, Kahn CR. From mice to men: insights into the insulin resistance syndromes. Annu Rev Physiol 2006; 68(1): 123-58. [http://dx.doi.org/10.1146/annurev.physiol.68.040104.124723] [PMID: 16460269]

[73]

Santoleri D, Titchenell PM. Resolving the Paradox of Hepatic Insulin Resistance. Cell Mol Gastroenterol Hepatol 2019; 7(2): 447-56. [http://dx.doi.org/10.1016/j.jcmgh.2018.10.016] [PMID: 30739869]

[74]

Brown MS, Goldstein JL. Selective versus total insulin resistance: a pathogenic paradox. Cell Metab 2008; 7(2): 95-6. [http://dx.doi.org/10.1016/j.cmet.2007.12.009] [PMID: 18249166]

[75]

Vaiserman A, Lushchak O. Developmental origins of type 2 diabetes: Focus on epigenetics. Ageing Res Rev 2019; 55: 100957. [http://dx.doi.org/10.1016/j.arr.2019.100957] [PMID: 31473332]

[76]

Huda MN, Kim M, Bennett BJ. Modulating the Microbiota as a Therapeutic Intervention for Type 2

Pathophysiology of T2D

The Role of Nitric Oxide in Type 2 Diabetes 25

Diabetes. Front Endocrinol (Lausanne) 2021; 12: 632335. [http://dx.doi.org/10.3389/fendo.2021.632335] [PMID: 33897618] [77]

Galicia-Garcia U, Benito-Vicente A, Jebari S, et al. Pathophysiology of Type 2 Diabetes Mellitus. Int J Mol Sci 2020; 21(17): 6275. [http://dx.doi.org/10.3390/ijms21176275] [PMID: 32872570]

[78]

Prevention or Delay of Type 2 Diabetes: Standards of Medical Care in Diabetes—2019. Diabetes Care 2019; 42 (Suppl. 1): S29-33. [http://dx.doi.org/10.2337/dc19-S003] [PMID: 30559229]

[79]

Zaccardi F, Webb DR, Yates T, Davies MJ. Pathophysiology of type 1 and type 2 diabetes mellitus: a 90-year perspective. Postgrad Med J 2016; 92(1084): 63-9. [http://dx.doi.org/10.1136/postgradmedj-2015-133281] [PMID: 26621825]

[80]

Schwartz MW, Seeley RJ, Tschöp MH, et al. Cooperation between brain and islet in glucose homeostasis and diabetes. Nature 2013; 503(7474): 59-66. [http://dx.doi.org/10.1038/nature12709] [PMID: 24201279]

[81]

Taylor R, Al-Mrabeh A, Sattar N. Understanding the mechanisms of reversal of type 2 diabetes. Lancet Diabetes Endocrinol 2019; 7(9): 726-36. [http://dx.doi.org/10.1016/S2213-8587(19)30076-2] [PMID: 31097391]

[82]

Mezza T, Cinti F, Cefalo CMA, Pontecorvi A, Kulkarni RN. beta-Cell Fate in Human Insulin Resistance and Type 2 Diabetes: A Perspective on Islet Plasticity. 2019; 68(6): 1121-9.

[83]

Asmat U, Abad K, Ismail K. Diabetes mellitus and oxidative stress—A concise review. Saudi Pharm J 2016; 24(5): 547-53. [http://dx.doi.org/10.1016/j.jsps.2015.03.013] [PMID: 27752226]

[84]

Muniyappa R, Lee S, Chen H, Quon MJ. Current approaches for assessing insulin sensitivity and resistance in vivo: advantages, limitations, and appropriate usage. Am J Physiol Endocrinol Metab 2008; 294(1): E15-26. [http://dx.doi.org/10.1152/ajpendo.00645.2007] [PMID: 17957034]

[85]

Blaslov K, Naranđa FS, Kruljac I, Renar IP. Treatment approach to type 2 diabetes: Past, present and future. World J Diabetes 2018; 9(12): 209-19. [http://dx.doi.org/10.4239/wjd.v9.i12.209] [PMID: 30588282]

[86]

Paneni F, Costantino S, Cosentino F. Role of oxidative stress in endothelial insulin resistance. World J Diabetes 2015; 6(2): 326-32. [http://dx.doi.org/10.4239/wjd.v6.i2.326] [PMID: 25789114]

[87]

Masaki N, Ido Y, Yamada T, et al. Endothelial Insulin Resistance of Freshly Isolated Arterial Endothelial Cells From Radial Sheaths in Patients With Suspected Coronary Artery Disease. J Am Heart Assoc 2019; 8(6): e010816. [http://dx.doi.org/10.1161/JAHA.118.010816] [PMID: 30885039]

[88]

Unnikrishnan AG. Tissue-specific insulin resistance. Postgrad Med J 2004; 80(946): 435. [http://dx.doi.org/10.1136/pgmj.2004.023176] [PMID: 15299149]

[89]

Pearson T, Wattis JAD, King JR, MacDonald IA, Mazzatti DJ. The Effects of Insulin Resistance on Individual Tissues: An Application of a Mathematical Model of Metabolism in Humans. Bull Math Biol 2016; 78(6): 1189-217. [http://dx.doi.org/10.1007/s11538-016-0181-1] [PMID: 27306890]

[90]

Tessari P, Cecchet D, Cosma A, et al. Nitric oxide synthesis is reduced in subjects with type 2 diabetes and nephropathy. Diabetes 2010; 59(9): 2152-9. [http://dx.doi.org/10.2337/db09-1772] [PMID: 20484137]

[91]

Karki S, Farb MG, Ngo DTM, et al. Forkhead box O-1 modulation improves endothelial insulin resistance in human obesity. Arterioscler Thromb Vasc Biol 2015; 35(6): 1498-506. [http://dx.doi.org/10.1161/ATVBAHA.114.305139] [PMID: 25908760]

26 The Role of Nitric Oxide in Type 2 Diabetes

Ghasemi and Kashfi

[92]

Gastaldelli A, Gaggini M, DeFronzo RA. Role of Adipose Tissue Insulin Resistance in the Natural History of Type 2 Diabetes: Results From the San Antonio Metabolism Study. Diabetes 2017; 66(4): 815-22. [http://dx.doi.org/10.2337/db16-1167] [PMID: 28052966]

[93]

Khardori R. Changing paradigms in type 2 diabetes mellitus. Indian J Endocrinol Metab 2013; 17(7) (Suppl. 1): 68. [http://dx.doi.org/10.4103/2230-8210.119509] [PMID: 24251224]

The Role of Nitric Oxide in Type 2 Diabetes, 2022, 27-38

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CHAPTER 2

Nitric oxide: A Brief History of Discovery and Timeline of its Research Asghar Ghasemi1,* and Khosrow Kashfi2 Endocrine Physiology Research Center, Research Institute for Endocrine Sciences, Shahid Beheshti University of Medical Sciences, Tehran, Iran 2 Department of Molecular, Cellular and Biomedical Sciences, Sophie Davis School of Biomedical Education, City University of New York School of Medicine, New York, NY10031, USA 1

Abstract: Nitric oxide (NO) plays a critical role in many physiological and pathological functions in the human body. Following the discovery in 1986-1987 that endothelium-derived relaxing factor (EDRF) is NO, the number of NO-based publications within all fields of medicine has increased exponentially. This report provides a brief historical view of NO-based research, emphasizing the events in the last two decades of the 20th century.

Keywords: Cyclic Guanosine Monophosphate, Endothelial Nitric Oxide Synthase, Endothelium-Derived Relaxing Factor, History, Inducible Nitric Oxide Synthase, Nitric Oxide, Neural Nitric Oxide Synthase, Nitric Oxide Deficiency, Nitric Oxide Donating Agents, Wall Saltpeter. INTRODUCTION Humans have a long history of using nitrogen-containing substances. About 5000 years ago, “wall saltpeter” [Ca(NO3)2] or “niter” (KNO3) were used to preserve foods [1, 2]; in addition, sublingual KNO3 was used for treating angina about 1000 years ago [3]. Research on nitric oxide (NO) functions began in the late 1970s to the early 1980s. It bloomed in 1998 when the Nobel Prize in Physiology or Medicine was awarded to Robert F. Furchgott, Louis J. Ignarro, and Ferid Murad “for their discoveries concerning NO as a signaling molecule in the cardiovascular system” [4]. Nitric oxide is a free radical gas [5]. It has been called an ephemeral substance [6], a pharmacologic smart bomb [5], a powerful queen of communication and Corresponding author Asghar Ghasemi: Endocrine Physiology Research Center, Research Institute for Endocrine Sciences, Shahid Beheshti University of Medical Sciences, Tehran, Iran; No. 24, Erabi Street, Velenjak, Tehran, Iran; Phone: +98 21 22409309; Fax: +98 21 22416264, Email: [email protected]

*

Asghar Ghasemi, Khosrow Kashfi, Zahra Bahadoran (Eds.) All rights reserved-© 2022 Bentham Science Publishers

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defense [7], and the most ubiquitous intercellular signaling molecule [8]. Nowadays, we accept that NO is involved in the homeostasis of almost every physiological system in the human body [9]. In addition, active research is ongoing in which NO is a target molecule for disease treatment. Thus, historicizing science acknowledges the pioneers and helps us better conceptualize the issues. This chapter provides a brief historical view of NO-based research. HISTORY OF NO FIELD Table 1 presents chronological progress in NO research, and (Fig. 1) highlights the main events. According to a paper by Ignarro, the NO field study was launched by the Murad group in the 1970s [10]. However, as Furchgott had discussed, the story of NO began in 1953 when it was found that acetylcholine (ACh), which was known to be a vasodilator in the whole animal, caused contraction of aortic strips of the rabbit aorta [11]. However, in an experiment conducted in 1978, it was accidentally realized that ACh partially relaxes norepinephrine-induced precontracted rabbit aorta [11]. In 1980, Furchgott and Zawadzki reported that ACh, via its muscarinic receptors, stimulates endothelial cells to release a substance or substances, which cause(s) relaxation of vascular smooth muscle cells [12]. The substance was initially named the Furchgott Factor to distinguish it from other endothelium-dependent relaxing factors [13]. ACh-induced endothelium-dependent relaxation of vascular smooth muscle was also observed in other vessels [12] and considered a principal mechanism of the vasodilatory effect of muscarinic agonists [14]. Cyclooxygenase inhibitors did not affect ACh-induced endothelium-dependent relaxation of the vascular smooth muscles, leading to this hypothesis that activating muscarinic receptors by ACh releases a non-prostanoid substance from the endothelial cells that diffuses to and relaxes vascular smooth muscle cells [11]. Besides, the sandwich procedure, in which endothelium-denuded transverse strips of the aorta and endothelium-intact longitudinal strips mounted together in clips with intimal surface apposed, provides direct evidence for the hypothesis as at this condition, ACh-induced relaxation of the muscle was restored [11, 12]. In 1981, it was found that hydroquinone, a free radical quencher, inhibits AChinduced relaxation suggesting that the relaxing factor may be a free radical [14]. In the same year (1981), it was found that there are other endothelium-dependent relaxing agents, including a Ca2+ ionophore (A23187) [14], which suggested a central role for calcium in the release or synthesis of the relaxing factor [11]. For the details of the first reports of substances that elicited endothelium-dependent relaxation, interested readers are referred to Furchgott and Vanhoutte [15]. Regarding the positive association between increased cyclic guanosine

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monophosphate (cGMP) and smooth muscle relaxation, in 1981, Furchgott speculated that the relaxing factor relaxes vascular smooth muscle via increasing cGMP; this hypothesis was true [11]. In 1982, the non-prostanoid substance involved in vascular smooth muscle relaxation was referred to as endothelium-derived relaxing factor (EDRF) by the Furchgott group [11, 16, 17]. In 1987, Ignarro and colleagues reported that based on direct chemical and indirect pharmacological evidence, EDRF closely resembles NO [18]. According to Furchgott, based on several works, the concept that EDRF is NO was independently proposed by him and Ignarro in 1986 in a symposium; papers of this symposium were published in 1988 [11]. One year after the 1986 symposium, in 1987, three groups, including Ignarro et al. [19], Moncada et al. [20], and Furchgott et al. [11], reported that EDRF is NO. According to a recent review by Lancaster, investigations in parallel lines of cancer/immune, cardiovascular, and the nervous system converged in 1986-1988, which led to NO's discovery [21]. In 1988, L-arginine was identified as the endogenous substrate for NO synthesis by the Moncada group [22] and others [23]. This discovery was based on previous reports highlighting that activated macrophages generate nitrite and nitrate from L-arginine [6]. In 1990, Bredt and Snyder isolated and purified NO synthase (they named it NO synthetase) from rat cerebellum as a calmodulin-requiring enzyme [24]; following neuronal NOS (nNOS) isolation, inducible NOS (iNOS), and endothelial NOS (eNOS) were also isolated in 1991 [25, 26]. NOS isoforms originally were named after the tissues in which they were first identified [6, 27]. However, because both eNOS and nNOS have inducible forms and iNOS is also constitutively expressed in some tissues, nNOS, iNOS and eNOS are currently referred to as NOS-I, NOS-II, and NOS-III, respectively, according to the order in which they were first cloned [28]. NO production via the L-arginine-NO pathway occurs in almost every cell in the human body [29]. In 1992, Science magazine selected NO as the molecule of the year [30], and it was discovered that S-nitrosylation is a cellular regulatory mechanism of NO action [31]. In 1994, NOS-independent NO generation was reported in the stomach [32, 33]; this suggested an alternative or backup system besides the classical L-arginine pathway for sufficient NO generation, particularly during hypoxia [34]. In 1998, Pfizer company introduced sildenafil (Viagra®) for managing erectile dysfunction in men [10, 35]; sildenafil inhibits phosphodiesterase 5A (PDE5A) and increases intracellular cGMP [28]. In 1999, inhaled NO was approved by the U.S. Food and Drug Administration (FDA) for treating infants with persistent pulmonary hypertension [36, 37]. In 2001, the first report of enzymatic denitrosation and nitrosothiols’ regulation by NO was

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reported [38, 39]. In 2005, it was shown that nitrite has NO-independent signaling properties [40]. In 2011, nitrite was proposed as Vitamin N, which can correct conditions related to NO deficiency [38]. In 2017, Latanoprostene, a NO-donating prostaglandin analog, was approved by the FDA as an ophthalmic solution for the reduction of intraocular pressure in patients with open-angle glaucoma or ocular hypertension [41].

Fig. (1). Main events related to nitric oxide (NO) research in the late 20th and early 21st centuries. ACh, acetylcholine; EDRF, endothelium-derived relaxing factor; FDA, U.S. Food and Drug Administration; eNOS endothelial NO synthase; iNOS, inducible NOS; nNOS, neural NOS. Created with Biorender.com. Table 1. History of research related to nitric oxide (NO). Year

Event/discovery

3000 BC

“Wall saltpeter” or “nitre” [Ca(NO3)2] was used to preserve foods [1, 2]

~1000

Treatment of angina using sublingual potassium nitrate [3]

1610

Synthesis of NO by Jan Baptista Van Helmont [21, 42]

1772

Joseph Priestly recognized NO as a distinct chemical entity and gave NO the name nitrous air [42, 43]

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(Table 1) cont.....

Year

Event/discovery

1865

NO reacts with hemoglobin by Hermann [1, 21]

1879

Using nitroglycerine for treating angina pectoris by Murrell [44]

1880

Nitrites are vasodilators [45]

1897

Hemoglobin reduces nitrite to NO [43]

1916

The human body produces nitrate [46]

1927

Nitric oxide inhibits mitochondrial respiration [43]

1953

ACh, a vasodilator in the whole animal, causes contraction of the rabbit aortic strips [11]

1960

cGMP was synthesized for the first time [47]

1963

First evidence that cGMP exists in biological systems [48]

1966

Isolation and purification of cyclic nucleotide phosphodiesterase [49]

1975

Nitrite activates guanylate cyclase [50]

1977

NO, and NO-releasing agents (e.g., sodium nitroprusside and nitroglycerin) activate guanylate cyclase and increase cGMP [51]; activators of guanylate cyclase relax the tracheal smooth muscle [52]

1978

Inhibition of guanylate cyclase by hemoglobin and myoglobin [43]; ACh partially relaxes norepinephrine-induced precontracted rabbit aorta [11]

1979

NO is a cGMP-mediated vasorelaxant [53]

1980

ACh-induced relaxation of isolated arteries is endothelium-dependent [12]; endothelium produces a non-prostanoid relaxing factor in response to ACh [12]; anoxia, inhibition of arachidonic acid release, and inhibition of lipoxygenase inhibit endothelium-dependent relaxation [12]

1981

Free radical quenching inhibits ACh-induced relaxation [14]; NO inhibits platelet aggregation [54]; Cellular thiols are involved in the NO activity [55]

1982

ACh-induced relaxation is associated with increased cGMP [11]; the relaxing factor was referred to as EDRF (endothelium-derived relaxing factor) [11, 16]; L-arginine is an endogenous activator of soluble guanylate cyclase [56]

1983

Agonist-induced endothelium-dependent relaxation in vessels is mediated by cGMP [57]; the term endothelial dysfunction was coined [58]

1986

EDRF reacts with superoxide anion [59]; EDRF inhibits platelet aggregation [60]

1987

EDRF is NO [19, 20, 61]; activated macrophages produce citrulline, nitrite, and nitrate from Larginine [61]

1988

NO is synthesized from L-arginine [22]; The first report of NO production by immune cells [62]

1989

First report of L-arginine converting enzyme (later named NOS) [63]

1990

Isolation of neural NOS from rat cerebellum and its calmodulin-dependency [24]

1991 Isolation of iNOS from macrophage [25] and eNOS from the bovine aortic endothelial cells [26]; NO is present in exhaled air [64] 1992 NO is the molecule of the year, by the Science magazine [30]; S-nitrosylation is a cellular regulatory mechanism of NO [31]

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(Table 1) cont.....

Year

Event/discovery

1994

NO inhibits cytochrome c oxidase [6]; NOS-independent NO generation in the stomach [32, 33]; insulin stimulates NO release from endothelium [65, 66]; first evidence that NO acts as an endocrine signaling molecule in cats [67]

1997

Publication of the journal “Nitric Oxide: Biology and Chemistry” [68]

1998 Awarding Nobel Prize in Physiology or Medicine to Robert F. Furchgott, Louis J. Ignarro, and Ferid Murad [69]; Pfizer company introduced Viagra® for managing erectile dysfunction in men [10, 35] 1999

FDA-approved inhaled NO for treating infants with persistent pulmonary hypertension [36]

2001

The first report of enzymatic denitrosation and nitrosothiols’ regulation [39]; eNOS−/− mice are insulin-resistant, and eNOS plays a major role in the regulation of insulin sensitivity [70]

2003

NO increases mitochondrial biogenesis [71]

2005

Nitrite has NO-independent signaling properties [40]

2009

May 19, 2009, Robert Francis Furchgott died [72]; he was born on June 4, 1916 [69]

2010

Inorganic nitrate reverses features of metabolic syndrome in eNOS-/- mice [73]

2017

November 2, 2017, Latanoprostene, a NO-donating prostaglandin analog, was approved by FDA as an ophthalmic solution to reduce intraocular pressure in patients with open-angle glaucoma or ocular hypertension [41]

ACh, acetylcholine; cGMP, cyclic guanosine monophosphate; EDRF, endothelium-derived relaxing factor; eNOS, endothelial nitric oxide (NO) synthase; FDA, Food and Drug Administration; nNOS, neural NOS; iNOS, inducible NOS.

Diabetes-Related NO Research In 1927, it was reported that NO inhibits mitochondrial respiration [43]. In 1939, insulin’s vasodilatory effect was first reported [66, 74]. In 1994, it was shown that NO inhibits cytochrome c oxidase [6] and that the vasodilatory effect of insulin is due to stimulation of NO release from endothelium [65, 66]. In 2001, it was shown that eNOS−/− mice are insulin-resistant and that eNOS plays a major role in regulating insulin sensitivity [70]. In 2003, it was shown that NO increases mitochondrial biogenesis [71]. In 2010, it was shown that inorganic nitrate reverses features of metabolic syndrome in eNOS-/- mice [73]. Animal studies indicate that NO boosting, for example, using nitrite and nitrite, has beneficial metabolic effects in type 2 diabetes; however, these data need confirmation in human studies [75]. CONCLUDING REMARKS Scientific discoveries are categorized as Charge, Challenge, and Chance (ChaCha-Cha theory of Scientific Discovery) [76]. Charge discoveries solve known problems, Challenge discoveries, present new theories/concepts in response to unexplained facts, and finally, Chance discoveries are serendipitous [76]. It seems

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The Role of Nitric Oxide in Type 2 Diabetes 33

that the discovery of the NO’s biological roles is mainly of the Challenge type; however, Chance was also involved [4, 21, 77], or one can say it was a chance observation by a prepared mind [13]. Most discoveries involve the contribution of many people [30], which contribute pieces to the puzzle [17]. As Louis Pasteur said, “Science knows no country.” Many investigators have contributed to the field that we cannot name all here. The brief history of the NO field presented here is not a complete one, and interested readers are referred to more comprehensive documents [21, 78], particularly a recent paper by Lancaster Jr [21]. In addition, there are some controversies about the dates and events related to the field. (Fig. 2) presents some past and present concepts and future challenges in the NO field.

Fig. (2). Past and present concepts and future challenges in the nitric oxide (NO) field [3, 24-26, 28, 32-34, 38, 44, 79, 80]. NOS, NO synthase; sGC, soluble guanylyl cyclase; cGMP, cyclic guanosine monophosphate; PDE, phosphodiesterase; Created with Biorender.com.

CONSENT FOR PUBLICATION Not applicable. CONFLICT OF INTEREST The author declares no conflict of interest, financial or otherwise. ACKNOWLEDGEMENT Declared none. REFERENCES [1]

Gladwin MT, Schechter AN, Kim-Shapiro DB, et al. The emerging biology of the nitrite anion. Nat Chem Biol 2005; 1(6): 308-14. [http://dx.doi.org/10.1038/nchembio1105-308] [PMID: 16408064]

[2]

Binkerd EF, Kolari OE. The history and use of nitrate and nitrite in the curing of meat. Food Cosmet Toxicol 1975; 13(6): 655-61.

34 The Role of Nitric Oxide in Type 2 Diabetes

Ghasemi and Kashfi

[http://dx.doi.org/10.1016/0015-6264(75)90157-1] [PMID: 1107192] [3]

Butler AR, Nicholson R. Life, death and nitric oxide. 2003.

[4]

Zetterstrom R. The 1998 Nobel Prize--discovery of the role of nitric oxide as a signalling molecule. Acta paediatrica (Oslo, Norway : 1992). 2009; 98(3): 593-9.

[5]

Konstadt S. Nitric oxide: Has it progressed from molecule of the year to wonder drug of the decade? J Cardiothorac Vasc Anesth 1995; 9(6): 625-6. [http://dx.doi.org/10.1016/S1053-0770(05)80220-4] [PMID: 8664450]

[6]

Moncada S, Higgs EA. The discovery of nitric oxide and its role in vascular biology. Br J Pharmacol 2006; 147(S1) (Suppl. 1): S193-201. [http://dx.doi.org/10.1038/sj.bjp.0706458] [PMID: 16402104]

[7]

Culotta E, Koshland DE Jr. NO news is good news. Science 1992; 258(5090): 1862-5. [http://dx.doi.org/10.1126/science.1361684] [PMID: 1361684]

[8]

Marsh N, Marsh A. A short history of nitroglycerine and nitric oxide in pharmacology and physiology. Clin Exp Pharmacol Physiol 2000; 27(4): 313-9. [http://dx.doi.org/10.1046/j.1440-1681.2000.03240.x] [PMID: 10779131]

[9]

Kapil V, Khambata RS, Jones DA, et al. The Noncanonical Pathway for In Vivo Nitric Oxide Generation: The Nitrate-Nitrite-Nitric Oxide Pathway. Pharmacol Rev 2020; 72(3): 692-766. [http://dx.doi.org/10.1124/pr.120.019240] [PMID: 32576603]

[10]

Ignarro LJ. Nitric oxide is not just blowing in the wind. Br J Pharmacol 2019; 176(2): 131-4. [http://dx.doi.org/10.1111/bph.14540] [PMID: 30556130]

[11]

Furchgott RF. Endothelium-derived relaxing factor: discovery, early studies, and identification as nitric oxide. Biosci Rep 1999; 19(4): 235-51. [http://dx.doi.org/10.1023/A:1020537506008] [PMID: 10589989]

[12]

Furchgott RF, Zawadzki JV. The obligatory role of endothelial cells in the relaxation of arterial smooth muscle by acetylcholine. Nature 1980; 288(5789): 373-6. [http://dx.doi.org/10.1038/288373a0] [PMID: 6253831]

[13]

Henderson A. It all used to be so simple in the old days. A personal view. Eur Heart J 2001; 22(8): 648-53. [http://dx.doi.org/10.1053/euhj.2000.2278] [PMID: 11286521]

[14]

Furchgott RF. The requirement for endothelial cells in the relaxation of arteries by acetylcholine and some other vasodilators. Trends Pharmacol Sci 1981; 2: 173-6. [http://dx.doi.org/10.1016/0165-6147(81)90303-5]

[15]

Furchgott RF, Vanhoutte PM. Endothelium-derived relaxing and contracting factors. FASEB J 1989; 3(9): 2007-18. [http://dx.doi.org/10.1096/fasebj.3.9.2545495] [PMID: 2545495]

[16]

Cherry PD, Furchgott RF, Zawadzki JV, Jothianandan D. Role of endothelial cells in relaxation of isolated arteries by bradykinin. Proc Natl Acad Sci USA 1982; 79(6): 2106-10. [http://dx.doi.org/10.1073/pnas.79.6.2106] [PMID: 6952258]

[17]

Atta-Ur-Rahman , Waldman SA. Editorial (Thematic Issue: Ferid Murad, at 80: A Legacy of Science, Medicine, and Mentorship). Curr Med Chem 2016; 23(24): 2556-8. [http://dx.doi.org/10.2174/092986732324160830173604] [PMID: 27776470]

[18]

Ignarro LJ, Byrns RE, Buga GM, Wood KS. Endothelium-derived relaxing factor from pulmonary artery and vein possesses pharmacologic and chemical properties identical to those of nitric oxide radical. Circ Res 1987; 61(6): 866-79. [http://dx.doi.org/10.1161/01.RES.61.6.866] [PMID: 2890446]

[19]

Ignarro LJ, Buga GM, Wood KS, Byrns RE, Chaudhuri G. Endothelium-derived relaxing factor produced and released from artery and vein is nitric oxide. Proc Natl Acad Sci USA 1987; 84(24):

A Brief History of NO

The Role of Nitric Oxide in Type 2 Diabetes 35

9265-9. [http://dx.doi.org/10.1073/pnas.84.24.9265] [PMID: 2827174] [20]

Palmer RMJ, Ferrige AG, Moncada S. Nitric oxide release accounts for the biological activity of endothelium-derived relaxing factor. Nature 1987; 327(6122): 524-6. [http://dx.doi.org/10.1038/327524a0] [PMID: 3495737]

[21]

Lancaster JR Jr. Historical origins of the discovery of mammalian nitric oxide (nitrogen monoxide) production/physiology/pathophysiology. Biochem Pharmacol 2020; 176: 113793. [http://dx.doi.org/10.1016/j.bcp.2020.113793] [PMID: 31923387]

[22]

Palmer RMJ, Ashton DS, Moncada S. Vascular endothelial cells synthesize nitric oxide from Larginine. Nature 1988; 333(6174): 664-6. [http://dx.doi.org/10.1038/333664a0] [PMID: 3131684]

[23]

Schmidt HHHW, Nau H, Wittfoht W, et al. Arginine is a physiological precursor of endotheliumderived nitric oxide. Eur J Pharmacol 1988; 154(2): 213-6. [http://dx.doi.org/10.1016/0014-2999(88)90101-X] [PMID: 3265919]

[24]

Bredt DS, Snyder SH. Isolation of nitric oxide synthetase, a calmodulin-requiring enzyme. Proc Natl Acad Sci USA 1990; 87(2): 682-5. [http://dx.doi.org/10.1073/pnas.87.2.682] [PMID: 1689048]

[25]

Hevel JM, White KA, Marletta MA. Purification of the inducible murine macrophage nitric oxide synthase. Identification as a flavoprotein. J Biol Chem 1991; 266(34): 22789-91. [http://dx.doi.org/10.1016/S0021-9258(18)54421-5] [PMID: 1720773]

[26]

Pollock JS, Förstermann U, Mitchell JA, et al. Purification and characterization of particulate endothelium-derived relaxing factor synthase from cultured and native bovine aortic endothelial cells. Proc Natl Acad Sci USA 1991; 88(23): 10480-4. [http://dx.doi.org/10.1073/pnas.88.23.10480] [PMID: 1720542]

[27]

Moncada S, Erusalimsky JD. Does nitric oxide modulate mitochondrial energy generation and apoptosis? Nat Rev Mol Cell Biol 2002; 3(3): 214-20. [http://dx.doi.org/10.1038/nrm762] [PMID: 11994742]

[28]

Bryan NS, Bian K, Murad F. Discovery of the nitric oxide signaling pathway and targets for drug development. Front Biosci 2009; 14(1): 1-18. [PMID: 19273051]

[29]

Lundberg JO, Carlström M, Weitzberg E. Metabolic Effects of Dietary Nitrate in Health and Disease. Cell Metab 2018; 28(1): 9-22. [http://dx.doi.org/10.1016/j.cmet.2018.06.007] [PMID: 29972800]

[30]

Koshland DE Jr. The molecule of the year. Science 1992; 258(5090): 1861. [http://dx.doi.org/10.1126/science.1470903] [PMID: 1470903]

[31]

Stamler JS, Simon DI, Osborne JA, et al. S-nitrosylation of proteins with nitric oxide: synthesis and characterization of biologically active compounds. Proc Natl Acad Sci USA 1992; 89(1): 444-8. [http://dx.doi.org/10.1073/pnas.89.1.444] [PMID: 1346070]

[32]

Benjamin N, O’Driscoll F, Dougall H, et al. Stomach NO synthesis. Nature 1994; 368(6471): 502. [http://dx.doi.org/10.1038/368502a0] [PMID: 8139683]

[33]

Lundberg JO, Weitzberg E, Lundberg JM, Alving K. Intragastric nitric oxide production in humans: measurements in expelled air. Gut 1994; 35(11): 1543-6. [http://dx.doi.org/10.1136/gut.35.11.1543] [PMID: 7828969]

[34]

Lundberg JO, Weitzberg E. NO-synthase independent NO generation in mammals. Biochem Biophys Res Commun 2010; 396(1): 39-45. [http://dx.doi.org/10.1016/j.bbrc.2010.02.136] [PMID: 20494108]

[35]

Yetik-Anacak G, Catravas JD. Nitric oxide and the endothelium: History and impact on cardiovascular

36 The Role of Nitric Oxide in Type 2 Diabetes

Ghasemi and Kashfi

disease. Vascul Pharmacol 2006; 45(5): 268-76. [http://dx.doi.org/10.1016/j.vph.2006.08.002] [PMID: 17052961] [36]

Steinhorn RH. Therapeutic approaches using nitric oxide in infants and children. Free Radic Biol Med 2011; 51(5): 1027-34. [http://dx.doi.org/10.1016/j.freeradbiomed.2011.01.006] [PMID: 21237265]

[37]

Schechter AN, Gladwin MT, Cannon RO III. NO solutions? J Clin Invest 2002; 109(9): 1149-51. [http://dx.doi.org/10.1172/JCI0215637] [PMID: 11994403]

[38]

Bryan NS. Application of nitric oxide in drug discovery and development. Expert Opin Drug Discov 2011; 6(11): 1139-54. [http://dx.doi.org/10.1517/17460441.2011.613933] [PMID: 22646983]

[39]

Liu L, Hausladen A, Zeng M, Que L, Heitman J, Stamler JS. A metabolic enzyme for S-nitrosothiol conserved from bacteria to humans. Nature 2001; 410(6827): 490-4. [http://dx.doi.org/10.1038/35068596] [PMID: 11260719]

[40]

Bryan NS, Fernandez BO, Bauer SM, et al. Nitrite is a signaling molecule and regulator of gene expression in mammalian tissues. Nat Chem Biol 2005; 1(5): 290-7. [http://dx.doi.org/10.1038/nchembio734] [PMID: 16408059]

[41]

Kaufman MB. Pharmaceutical Approval Update. P & T : a peer-reviewed journal for formulary management 2018; 43(1): 22-60.

[42]

Brennan PA, Thomas GJ, Langdon JD. The role of nitric oxide in oral diseases. Arch Oral Biol 2003; 48(2): 93-100. [http://dx.doi.org/10.1016/S0003-9969(02)00183-8] [PMID: 12642227]

[43]

Lancaster JR Jr. A Concise History of the Discovery of Mammalian Nitric Oxide (Nitrogen Monoxide) Biogenesis. Nitric Oxide, biology and pathobiology. 2017; 1-7.

[44]

Murrell W. Nitro-glycerine as a remedy for angina pectoris. Lancet 1879; 113(2890): 80-1. [http://dx.doi.org/10.1016/S0140-6736(02)46032-1]

[45]

Reichert ET, Mitchell SW. On the physiological action of potassium nitrite. Am J Med Sci 1880; 159(1): 158-80. [http://dx.doi.org/10.1097/00000441-188007000-00011]

[46]

Mitchell HH, Shonle HA, Grindley HS. The origin of the nitrates in the urine. J Biol Chem 1916; 24(4): 461-90. [http://dx.doi.org/10.1016/S0021-9258(18)87531-7]

[47]

Kots AY, Martin E, Sharina IG, Murad F. A short history of cGMP, guanylyl cyclases, and cGMPdependent protein kinases. Handb Exp Pharmacol 2009; 191(191): 1-14. [http://dx.doi.org/10.1007/978-3-540-68964-5_1] [PMID: 19089322]

[48]

Ashman DF, Lipton R, Melicow MM, Price TD. Isolation of adenosine 3′,5′-monophosphate and guanosine 3′,5′-monophosphate from rat urine. Biochem Biophys Res Commun 1963; 11(4): 330-4. [http://dx.doi.org/10.1016/0006-291X(63)90566-7] [PMID: 13965190]

[49]

Nair KG. Purification and properties of 3′,5′-cyclic nucleotide phosphodiesterase from dog heart. Biochemistry 1966; 5(1): 150-7. [http://dx.doi.org/10.1021/bi00865a020] [PMID: 4287216]

[50]

Kimura H, Mittal CK, Murad F. Activation of guanylate cyclase from rat liver and other tissues by sodium azide. J Biol Chem 1975; 250(20): 8016-22. [http://dx.doi.org/10.1016/S0021-9258(19)40809-0] [PMID: 240848]

[51]

Katsuki S, Arnold W, Mittal C, Murad F. Stimulation of guanylate cyclase by sodium nitroprusside, nitroglycerin and nitric oxide in various tissue preparations and comparison to the effects of sodium azide and hydroxylamine. J Cyclic Nucleotide Res 1977; 3(1): 23-35. [PMID: 14978]

A Brief History of NO

The Role of Nitric Oxide in Type 2 Diabetes 37

[52]

Arnold WP, Mittal CK, Katsuki S, Murad F. Nitric oxide activates guanylate cyclase and increases guanosine 3′:5′-cyclic monophosphate levels in various tissue preparations. Proc Natl Acad Sci USA 1977; 74(8): 3203-7. [http://dx.doi.org/10.1073/pnas.74.8.3203] [PMID: 20623]

[53]

Gruetter CA, Barry BK, McNamara DB, Gruetter DY, Kadowitz PJ, Ignarro L. Relaxation of bovine coronary artery and activation of coronary arterial guanylate cyclase by nitric oxide, nitroprusside and a carcinogenic nitrosoamine. J Cyclic Nucleotide Res 1979; 5(3): 211-24. [PMID: 39089]

[54]

Mellion BT, Ignarro LJ, Ohlstein EH, Pontecorvo EG, Hyman AL, Kadowitz PJ. Evidence for the inhibitory role of guanosine 3′, 5′-monophosphate in ADP-induced human platelet aggregation in the presence of nitric oxide and related vasodilators. Blood 1981; 57(5): 946-55. [http://dx.doi.org/10.1182/blood.V57.5.946.946] [PMID: 6111365]

[55]

Ignarro LJ, Lippton H, Edwards JC, et al. Mechanism of vascular smooth muscle relaxation by organic nitrates, nitrites, nitroprusside and nitric oxide: evidence for the involvement of S-nitrosothiols as active intermediates. J Pharmacol Exp Ther 1981; 218(3): 739-49. [PMID: 6115052]

[56]

Deguchi T, Yoshioka M. L-Arginine identified as an endogenous activator for soluble guanylate cyclase from neuroblastoma cells. J Biol Chem 1982; 257(17): 10147-51. [http://dx.doi.org/10.1016/S0021-9258(18)33996-6] [PMID: 6125510]

[57]

Rapoport RM, Murad F. Agonist-induced endothelium-dependent relaxation in rat thoracic aorta may be mediated through cGMP. Circ Res 1983; 52(3): 352-7. [http://dx.doi.org/10.1161/01.RES.52.3.352] [PMID: 6297832]

[58]

Catravas JD, Lazo JS, Dobuler KJ, Mills LR, Gillis CN. Pulmonary endothelial dysfunction in the presence or absence of interstitial injury induced by intratracheally injected bleomycin in rabbits. Am Rev Respir Dis 1983; 128(4): 740-6. [PMID: 6194726]

[59]

Gryglewski RJ, Palmer RMJ, Moncada S. Superoxide anion is involved in the breakdown of endothelium-derived vascular relaxing factor. Nature 1986; 320(6061): 454-6. [http://dx.doi.org/10.1038/320454a0] [PMID: 3007998]

[60]

Azuma H, Ishikawa M, Sekizaki S. Endothelium-dependent inhibition of platelet aggregation. Br J Pharmacol 1986; 88(2): 411-5. [http://dx.doi.org/10.1111/j.1476-5381.1986.tb10218.x] [PMID: 3089351]

[61]

Hibbs JB Jr, Taintor RR, Vavrin Z. Macrophage cytotoxicity: role for L-arginine deiminase and imino nitrogen oxidation to nitrite. Science 1987; 235(4787): 473-6. [http://dx.doi.org/10.1126/science.2432665] [PMID: 2432665]

[62]

Marletta MA, Yoon PS, Iyengar R, Leaf CD, Wishnok JS. Macrophage oxidation of L-arginine to nitrite and nitrate: nitric oxide is an intermediate. Biochemistry 1988; 27(24): 8706-11. [http://dx.doi.org/10.1021/bi00424a003] [PMID: 3242600]

[63]

Mayer B, Schmidt K, Humbert P, Böhme E. Biosynthesis of endothelium-derived relaxing factor: A cytosolic enzyme in porcine aortic endothelial cells Ca2+-dependently converts L-arginine into an activator of soluble guanylyl cyclase. Biochem Biophys Res Commun 1989; 164(2): 678-85. [http://dx.doi.org/10.1016/0006-291X(89)91513-1] [PMID: 2573351]

[64]

Gustafsson LE, Leone AM, Persson MG, Wiklund NP, Moncada S. Endogenous nitric oxide is present in the exhaled air of rabbits, guinea pigs and humans. Biochem Biophys Res Commun 1991; 181(2): 852-7. [http://dx.doi.org/10.1016/0006-291X(91)91268-H] [PMID: 1721811]

[65]

Baron AD. Hemodynamic actions of insulin. Am J Physiol 1994; 267(2 Pt 1): E187-202. [PMID: 8074198]

38 The Role of Nitric Oxide in Type 2 Diabetes

Ghasemi and Kashfi

[66]

Scherrer U, Randin D, Vollenweider P, Vollenweider L, Nicod P. Nitric oxide release accounts for insulin’s vascular effects in humans. J Clin Invest 1994; 94(6): 2511-5. [http://dx.doi.org/10.1172/JCI117621] [PMID: 7989610]

[67]

Fox-Robichaud A, Payne D, Hasan SU, et al. Inhaled NO as a viable antiadhesive therapy for ischemia/reperfusion injury of distal microvascular beds. J Clin Invest 1998; 101(11): 2497-505. [http://dx.doi.org/10.1172/JCI2736] [PMID: 9616221]

[68]

EDITORIAL. Nitric Oxide 1997; 1(1): 1. [http://dx.doi.org/10.1006/niox.1996.0100]

[69]

Nicholls M. Nitric oxide discovery Nobel Prize winners. Eur Heart J 2019; 40(22): 1747-9. [http://dx.doi.org/10.1093/eurheartj/ehz361] [PMID: 31173095]

[70]

Duplain H, Burcelin R, Sartori C, et al. Insulin resistance, hyperlipidemia, and hypertension in mice lacking endothelial nitric oxide synthase. Circulation 2001; 104(3): 342-5. [http://dx.doi.org/10.1161/01.CIR.104.3.342] [PMID: 11457755]

[71]

Nisoli E, Clementi E, Paolucci C, et al. Mitochondrial biogenesis in mammals: the role of endogenous nitric oxide. Science 2003; 299(5608): 896-9. [http://dx.doi.org/10.1126/science.1079368] [PMID: 12574632]

[72]

Snyder SH. Robert Furchgott (1916–2009). Nature 2009; 460(7251): 47. [http://dx.doi.org/10.1038/460047a] [PMID: 19571876]

[73]

Carlström M, Larsen FJ, Nyström T, et al. Dietary inorganic nitrate reverses features of metabolic syndrome in endothelial nitric oxide synthase-deficient mice. Proc Natl Acad Sci USA 2010; 107(41): 17716-20. [http://dx.doi.org/10.1073/pnas.1008872107] [PMID: 20876122]

[74]

Abramson DI, Schkloven N, Margolis MN, Mirsky IA. Influence of massive doses of insulin on peripheral blood flow in man. Am J Physiol 1939; 128(1): 124-32. [http://dx.doi.org/10.1152/ajplegacy.1939.128.1.124]

[75]

Bahadoran Z, Mirmiran P, Kashfi K, Ghasemi A. Lost-in-Translation of Metabolic Effects of Inorganic Nitrate in Type 2 Diabetes: Is Ascorbic Acid the Answer? Int J Mol Sci 2021; 22(9): 4735. [http://dx.doi.org/10.3390/ijms22094735] [PMID: 33947005]

[76]

Koshland DE Jr. The Cha-Cha-Cha Theory of Scientific Discovery. Science 2007; 317(5839): 761-2. [http://dx.doi.org/10.1126/science.1147166] [PMID: 17690282]

[77]

Stuart-Smith K. Demystified. Nitric oxide. Molecular pathology : MP. 2002; 55(6): 360-6.

[78]

Marletta MA. Revisiting Nitric Oxide Signaling: Where Was It, and Where Is It Going? Biochemistry 2021; 60(46): 3491-6. [http://dx.doi.org/10.1021/acs.biochem.1c00276] [PMID: 34096266]

[79]

Lauder Brunton T. On the use of nitrite of amyl in angina pectoris. Lancet 1867; 90(2291): 97-8. [http://dx.doi.org/10.1016/S0140-6736(02)51392-1]

[80]

Bahadoran Z, Mirmiran P, Ghasemi A. Role of Nitric Oxide in Insulin Secretion and Glucose Metabolism. Trends Endocrinol Metab 2020; 31(2): 118-30. [http://dx.doi.org/10.1016/j.tem.2019.10.001] [PMID: 31690508]

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CHAPTER 3

Impaired Nitric Oxide Metabolism in Type 2 Diabetes: At a Glance Zahra Bahadoran1, Mattias Carlström2, Parvin Mirmiran3 and Asghar Ghasemi4,* Nutrition and Endocrine Research Center, Research Institute for Endocrine Sciences, Shahid Beheshti University of Medical Sciences, Tehran, Iran 2 Department of Physiology and Pharmacology, Karolinska Institute, Stockholm, Sweden 3 Department of Clinical Nutrition and Human Dietetics, Faculty of Nutrition Sciences and Food Technology, National Nutrition and Food Technology Research Institute, Shahid Beheshti University of Medical Sciences, Tehran, Iran 4 Endocrine Physiology Research Center, Research Institute for Endocrine Sciences, Shahid Beheshti University of Medical Sciences, Tehran, Iran 1

Abstract: Abnormal nitric oxide (NO) metabolism has been associated with the development of insulin resistance and type 2 diabetes (T2D). The concept of NO deficiency is supported by human studies on polymorphisms of endothelial NO synthase (eNOS) gene, animal knockout models for NO synthase isoforms (NOSs), and pharmacological evidence, showing detrimental effects of NOS inhibitors and salutary effects of NO donors on carbohydrate metabolism. On the other hand, T2D and insulin resistance may impair NO homeostasis due to hyperglycemia, oxidative stress, and inflammation. Reduced production of NO [i.e., impaired L-arginine-NOS pathway and function of the nitrate (NO3)-nitrite (NO2)-NO pathway], impaired NO transport within the circulation and delivery to target cells, as well as disrupted NO signaling (e.g., via oxidative-induced NO quenching, and impaired NO-cGMP signaling pathway) can all lead to a reduced NO bioactivity in T2D. This chapter focuses on the role of impaired NO metabolism in T2D.

Keywords: Dysglycemia, Endothelial Nitric Oxide Synthase, Glucose Metabolism, Insulin Resistance, Inducible Nitric Oxide Synthase, Neural Nitric Oxide Synthase, Nitric Oxide, Nitric Oxide Deficiency, Type 2 Diabetes.

Corresponding author Asghar Ghasemi: Endocrine Physiology Research Center, Research Institute for Endocrine Sciences, Shahid Beheshti University of Medical Sciences, Tehran, Iran; No. 24, Erabi Street, Velenjak, Tehran, Iran; Phone: +98 21 22409309; Fax: +98 21 22416264, Email: [email protected]

*

Asghar Ghasemi, Khosrow Kashfi, Zahra Bahadoran (Eds.) All rights reserved-© 2022 Bentham Science Publishers

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INTRODUCTION Nitric oxide (NO), commonly known as a unique biological free radical and signaling molecule with multiple functions [1, 2], is now considered an endocrine hormone [3] critically involved in whole-body glucose and insulin metabolism [4]. Fig. (1) illustrates two main pathways of NO production [the L-arginine-NO synthase (NOS) pathway and the nitrate (NO3)-nitrite (NO2)-NO pathway] and its metabolism.

Fig. (1). Pathways of nitric oxide (NO) production and metabolism. Two main pathways of NO production are the L-arginine-NO synthase (NOS) pathway and the nitrate (NO3)-nitrite (NO2)-NO pathway. L-arginine is provided by either exogenous (dietary intake, about 4000-6000 mg/day) or endogenous (de novo synthesis from citrulline and turnover of proteins) sources. This pathway is responsible for producing about 1000 µmol/day NO. Inorganic NO3 and NO2, provided either from dietary sources or endogenous NO metabolism, are used as substrates for non-enzymatic endogenous NO generation. This pathway is estimated to produce about 100 µmol/day NO. The source of the Fig. is (5), Quantitative aspects of nitric oxide production from nitrate and nitrite, EXCLI Journal, 2022, 21: 470-486.

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The Role of Nitric Oxide in Type 2 Diabetes 41

Impaired NO bioavailability is a common state in metabolic disorders, including type 2 diabetes (T2D), that is mainly attributed to decreased endothelial NO synthase (eNOS) expression or activity or by NO scavenging in conditions with excessive production of reactive oxygen species (ROS) [6, 7]. A bilateral causeand-consequence relation exists between impaired NO metabolism and the development and progression of T2D (Fig. 2).

Fig. (2). A proposed cause-and-effect and bilateral relationship between impaired nitric oxide (NO) metabolism and development of insulin resistance and type 2 diabetes (T2D). AGE, advanced glycation end product; cNOS, constitutive nitric oxide synthase; NO3, nitrate; NO2, nitrite; RAGE, receptor for AGE. Created with Biorender.com.

The critical role of NO in regulating glucose and insulin homeostasis is supported by experimental studies using genetically modified mice, either eNOS knockouts or eNOS over-expressed mice. Impaired glucose and insulin metabolism, as evident from hyperglycemia, hyperinsulinemia, insulin resistance, and glucose intolerance, occurs in homozygous [8 - 11] and heterozygous eNOS knockout animals [12], whereas overexpression of eNOS prevents diet-induced hyperinsulinemia [13, 14]. In contrast, overexpression of inducible NOS (iNOS) and hence the production of very high levels of NO is associated with the development of skeletal muscle insulin resistance [15], hepatic insulin resistance, hyperglycemia, and hyperinsulinemia [16]. iNOS-deficient mice compared to wild type, did not show metabolic dysfunctions induced by the high-fat diet (HFD) and displayed normal glucose tolerance, insulin sensitivity, and insulinstimulated glucose uptake in the skeletal muscle [17]. HFD increased iNOS mRNA expression by 2 to 4-fold in skeletal muscle [type I (soleus), type II-a (extensor digitorum longus, EDL), and type II-b (tibialis) fibers] and adipose tissue of wild-type mice. In contrast, obese Nos2–/– mice had normal insulin levels, glucose tolerance, and normal skeletal muscle glucose uptake than lean Nos2–/– or wild-type mice under a standard diet [17]. This evidence indicates that targeted

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disruption of iNOS prevents the development of whole-body and skeletal muscle insulin resistance against HFD, which is an inducer of obesity-linked T2D [17]. The second category of evidence supporting a bilateral relationship between NO and T2D is human genetic studies that introduced eNOS-gene polymorphisms [e.g., including 27bp-VNTR [18], G894T [19], E298D, and IE.G 18+ 27A→C alleles [20] as new genetic susceptibility factors for hyperinsulinemia, insulin resistance, and T2D. The predominant eNOS gene polymorphisms, e.g., the 4b4a VNTR (variable number of tandem repeats) polymorphism, are related to a decreased systemic NO [21]. The pooled data of 34 studies involving 16,609 subjects, assessing the association between eNOS gene polymorphisms and risk of T2D, reported that carrying polymorphisms of 4b4a VNTR and G894T, respectively, increased the risk of T2D by 34% [odds ratio (OR)=1.34, 95% confidence interval (CI)=1.15-1.57] and 25% (OR=1.25, 95% CI=1.06-1.48) [22]. This chapter provides an overview of NO's role in carbohydrate metabolism and the potential involvement of reduced NO bioactivity in developing and progressing metabolic disorders, including insulin resistance and T2D. ROLE OF NO IN GLUCOSE AND INSULIN HOMEOSTASIS The physiologic roles of NO in insulin secretion and glucose metabolism have been reviewed [4, 23 - 27]. In our recent review [4], the effects of low physiologic levels of NO produced by constitutive NOS [cNOS, i.e., eNOS and neural NOS (nNOS) isoforms] compared to very high and toxic levels of NO originating from iNOS, were discussed in main organs involved in carbohydrate metabolism (i.e., pancreatic β-cells, adipocytes, hepatocytes, and skeletal muscle cells). Furthermore, the NOS system(s) role in the central regulation of glucose homeostasis was addressed [4]. Table 1 shows how NO (either cNOS-derived or iNOS-derived) regulates carbohydrate metabolism. The different NOS isoforms produce variable amounts of NO and influence pancreatic insulin secretion differently. Depending on its local concentration, NO may inhibit or stimulate insulin secretion [28]. Different NO donors, like hydroxylamine, sodium nitroprusside, and 3-morpholinosydnonimine, exerted a significant insulinotropic effect [29]. NO seems to be essential for the early phase of glucose-stimulated insulin secretion (GSIS) since NOS inhibition decreases insulin secretion by 46-65% [30]. NO is likely to have dual stimulatory and inhibitory effects on insulin secretion depending on its concentrations; at concentrations lower than 50 nM, NO acts as a physiological insulinotropic substance, whereas it takes part in the negative feedback system in insulin secretion at higher concentrations (> 60 nM) [31]. It has been suggested that low levels of cNOS-derived NO act as a stimulator of insulin secretion, whereas

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higher concentrations may act as a negative feedback regulator of GSIS in response to high-glucose concentrations; both of them have physiological relevance to the normal pattern of insulin secretion [4]. The iNOS-derived NO seems to be involved in pathological functions [4]. Toxic levels of iNOS-derived NO lead to β-cell dysfunction, impaired insulin secretion, hyperglycemia, and the development of T2D [32 - 35]. The iNOS expression is higher in pancreatic islets of patients with T2D, and iNOS inhibition can restore disrupted GSIS [32]. iNOS-derived NO inhibits insulin secretion via 3′,5′-cyclic monophosphate (cGMP)-independent mechanisms [36], i.e., inhibition of mitochondrial electron transport chain (complexes I and II) and mitochondrial aconitase activity [37], S-nitrosylation of critical thiol groups involved in the secretory process [38], and tyrosine nitration and subsequent down-regulation of glucokinase [34]. At physiological concentrations, NO produced by both eNOS and nNOS improves skeletal muscle insulin sensitivity and potentiates skeletal muscle glucose uptake by several mechanisms, including increasing blood flow-dependent glucose delivery to skeletal muscle, increasing expression and translocation of glucose transporter 4 (GLUT4), and increasing insulin transendothelial transport (ITT) [3]. NO increases GLUT4 translocation via both soluble guanylyl cyclase (sGC)cGMP-protein kinase (PKG) pathway and cGMP-PKG-independent mechanisms, i.e., S-nitrosylation, S-glutathionylation, and tyrosine nitration of proteins involved in GLUT4 translocation [39]. The cGMP-PKG-independent mechanisms are critical because the NO-sGC-cGMP pathway accounts for up to 50% of NO actions in the skeletal muscle [40], and NO-induced sGC activity is lower in the skeletal muscle than in most other tissues. NO also increases ITT (a rate-limiting step in the peripheral action of insulin [41]), which in turn increases insulin delivery to the interstitial fluid of the muscle; this effect is sGC-cGM-independent and occurs viaS-nitrosylation and decreased activity of proteintyrosine phosphatase 1B (PTP1B), and subsequent elimination of its inhibitory effect on insulin signaling and insulin transport [41]. NO at high toxic levels, occurs following iNOS activation, impairs skeletal muscle insulin sensitivity and glucose uptake because it decreases GLUT4 gene expression, inactivates proteins involved in the early steps of insulin signaling (i.e., insulin receptor-β), insulin receptor substrate-1, and protein kinase B [15]) and impairs mitochondrial capacity in the skeletal muscle [42, 43]. In the adipose tissue, eNOS is the dominant NOS isoform involving NO production, which plays a crucial role in potentiating insulin sensitivity and glucose disposal. NO facilitates insulin-stimulated glucose uptake in brown and white adipose tissues (BAT and WAT) [44]. NO increases glucose uptake in 3T3-

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L1 adipocytes via an insulin-independent translocation of GLUT-4; this capacity of NO may potentiate the effect of insulin in adipose tissue [45]. The eNOSderived NO is crucial for normal glucose and insulin homeostasis in WAT [46] since decreased eNOS phosphorylation, eNOS uncoupling, and decreased eNOSderived NO in WAT lead to the development of insulin resistance [47]. The beneficial effects of NO on glucose metabolism in WAT are achieved by mediating insulin-dependent and insulin-independent glucose uptake, and sGC and PKG (PKG1 and PKG2) are involved in these actions [46]. Conversely, iNOS-derived NO, mainly induced by obesity and inflammation, induces adipose tissue insulin resistance [4] by impairing mitochondrial function, inhibiting preadipocyte differentiation, inducing P53-dependent adipose tissue fibrosis, and increasing protein levels of the hypoxia-inducible factor 1α (HIF-1α) [48]. In the liver, NO modulates hepatic glucose output by changing the expression and activity of enzymes involved in gluconeogenesis, glycogenolysis, and glycogenesis. Low concentrations of NO decrease the expression of phosphoenolpyruvate carboxykinase (PEPCK) and subsequently suppress hepatic gluconeogenesis [49] and also increase insulin sensitivity by releasing hepatic insulin sensitizing substance (HISS) [50]. A 200-800 nM of NO concentration is required to inhibit hepatic gluconeogenesis by half [51]. In contrast, NO produced by cytokines-activated iNOS disturbs hepatic glucose metabolism by decreasing cAMP- and glucagon-stimulated glycogenolysis; iNOS-derived NO also inhibits the activity of glyceraldehyde-3-phosphate dehydrogenase (GAPDH) by Snitrosylation [52]. iNOS-derived NO results in developing hepatic insulin resistance via increasing S-nitrosylation and inactivation of Akt [16], along with tyrosine nitration of key insulin signaling proteins in the liver, including insulin receptor-beta (IRβ) and insulin receptor substrates-1 and 2 (IRS-1and IRS-2) [53]. Nitric oxide also has a critical role in the central regulation of glucose homeostasis; the NOS-NO system in the hypothalamus regulates glucose metabolism via nNOS, as the predominant NOS isoform [54, 55] see Table 1. T2D AND WHOLE-BODY NO METABOLISM NO DEFICIENCY IN T2D The first investigation that addressed whole-body NO synthesis from L-arginine to NO in patients with T2D and diabetic nephropathy was conducted by Tessari et al. [6]. In brief, they showed that NO synthesis and conversion of L-arginine to NO are lower in patients with T2D and not appropriately stimulated in response to insulin. Moreover, hyperinsulinemia did not affect plasma L-arginine in diabetic patients, while it decreased it in control subjects by ~45%. They also reported that the fraction of infused L-arginine converted to NO was lower in diabetic patients

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The Role of Nitric Oxide in Type 2 Diabetes 45

in both basal conditions (0.22% e.g. 0.65%) and during euglycemic hyperinsulinemic clamp (0.32% e.g. 1.03%). Table 1. Potential roles of NO (cNOS-derived e.g. iNOS-derived) on main organs and pathways involving carbohydrate metabolism. cNOS-derived NO

iNOS-derived NO

Pancreatic β-cell [33, 35, 56 - 58]

Mediates normal pattern of insulin secretion Induces β-cell dysfunction Potentiates GSIS (in response to normal Impairs insulin secretion levels of glucose) by increasing intracellular Disturbs GSIS by impairing the [Ca+2] and S-nitrosylation of glucokinase glycolytic pathway and mitochondrial Acts as a physiologic negative feedback respiration regulator of GSIS (in response to highglucose concentrations) via activation of KATP channels, decreased phosphofructokinase, and decreased glucose metabolism

Skeletal Muscle [15, 39, 41, 59 - 61]

↑ Insulin sensitivity and glucose uptake ↓ Insulin sensitivity and glucose uptake ↑ Blood flow-dependent glucose delivery ↑ ↓ GLUT4 gene expression Expression and translocation of GLUT4 (via Impairs insulin signaling (deactivates phosphorylation of α-AMPK, acetyl-CoA IRβ, IRS-1, PI3K, and PKB/Akt) carboxylase, and translocation of Impairs mitochondrial capacity phosphorylated α-AMPK to the nucleus, Snitrosylation, S-glutathionylation, and tyrosine nitration of proteins involved in GLUT4 translocation) ↑ ITT (as a rate-limiting step in the peripheral action of the insulin) cNOS-derived NO

Adipose Tissues Mediates insulin-stimulated glucose uptake in (BAT and WAT) BAT and WAT [44 - 48, 62 - 64] ↑ Insulin-dependent and -independent (via mTORC2) glucose uptake ↑ GLUT4 expression and translocation into plasma membrane) ↑ Differentiation ↑ Microcirculation ↑ PPARγ and UCP-1 ↓ Lipolysis Regulates mitochondrial respiration

iNOS-derived NO • Macrophage-induced iNOS: ↓ Insulin sensitivity and glucose disposal Impairs mitochondrial function Inhibits preadipocyte differentiation Induces P53-dependent fibrosis ↑ HIF-1α • NEP-induced iNOS or sympathetic stimulated-iNOS: Contributes to normal glucose metabolism in BAT

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(Table 1) cont.....

cNOS-derived NO

iNOS-derived NO

Liver [16, 49, 50, 52, 65, 66]

Potentiates glucose-induced GLUT4 • Cytokine-activated iNOS: expression and translocation Disturbs hepatic glucose metabolism ↑ Expression of pro-insulin genes I and II and by decreasing cAMP- and glucagoninsulin biosynthesis stimulated glycogenolysis ↑ Vasodilation of hepatic arterial circulation ↓ Activity of GAPDH by S↑ Vasodilation of portal venous vascular bed nitrosylation ↑ Circulation of hepatic vasculature and ↑ ↓ Hepatic insulin sensitivity surface area for glucose uptake ↓ Insulin-stimulated phosphorylation Regulates hepatic glucose output (regulates of IRS-1, IRS-2, Akt, glycogen expression and activity of enzymes involved synthase kinase-3β, forkhead box O1, in gluconeogenesis, glycogenolysis, and mTORC (viaS-nitrosylation and glycogenesis) tyrosine nitration) ↓ Expression of PEPCK, ↓ hepatic ↑ Activity of glycogen phosphorylase gluconeogenesis ↓ Activity of glycogen synthase ↑ Insulin sensitivity, ↑ HISS

Central Nervous System [67 - 70]

Regulates insulin secretion from pancreatic β-cell Regulates insulin actions in peripheral tissues Mediates central actions of apelin, ghrelin, and leptin on glucose homeostasis

↑ NO concentrations in VMH→ ↑ hepatic insulin resistance

AMPK, 5' AMP-activated protein kinase; BAT, brown adipose tissue; cNOS, constitutive nitric oxide (NO) synthase; GAPDH, glyceraldehyde-3-phosphate dehydrogenase; GLUT4, glucose transporter 4; GSIS, glucose-stimulated insulin secretion; HIF-1α, hypoxia-inducible factor 1α; HISS, hepatic insulin sensitizing substance; iNOS, inducible NOS; IRS, insulin receptor substrate; IRβ, insulin receptor-β; ITT, insulin transendothelial transport; mTORC2, mammalian target of rapamycin complex 2; NEP, norepinephrine; PEPCK, phosphoenolpyruvate carboxykinase; PI3K, phosphoinositide 3-kinases; PKB/Akt protein kinase B; PPARγ, peroxisome proliferator-activated receptor γ; UCP-1, uncoupling protein 1; VMH, ventromedial nucleus of the hypothalamus; WAT, white adipose tissue.

Furthermore, the fractional synthesis rate (FSR) of NO (i.e., calculated as percent of circulating pool newly synthesized) was lower in patients with T2D (19.3±3.9% per day e.g. 22.9±4.5% per day, in T2D compared to healthy state), and it did not significantly increase following hyperinsulinemia (24.0±5.6% per day e.g. 37.9±6.4% per day, in T2D compared to healthy state). The absolute synthesis rate (ASR) of NOx (NO2+NO3) in patients with T2D was about onethird of that in control subjects (0.32 mmol per day e.g. 0.89 mmol per day) and did not increase in response to hyperinsulinemia as observed in control subjects (~30% increase) [6]. In healthy subjects, calculated body NOx pool, L-arginine flux, percent of NO synthesis from L-arginine flux, FSR, and ASR were reported to be ~3.2 mmol, 1.2 μmol/kg/min, 0.69%, 27.4%, and 0.97 mmol/day, respectively [71]. Following acute hyperinsulinemia, NOx pool and L-arginine flux were decreased by 20%

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The Role of Nitric Oxide in Type 2 Diabetes 47

and 30%, respectively, while the fraction of L-arginine flux converted to NOx, FSR, and ASR were increased by 100%, 25%, and 55%, respectively [71]. T2D and Circulating NO: an Epidemiologic Point of View Epidemiological studies have tried to address whether circulating NO metabolites are related to metabolic disorders or maybe a biomarker or surrogate of insulin resistance and T2D [72]. Elevated fasting circulating NO metabolites above the upper limit of reference values (65.6 µM) are related to chances of having T2D in women (OR=1.67, 95% CI=1.10–2.55) [73]. Likewise, circulating serum NO metabolites higher than 53.6 µM were related to the risk of having T2D (OR=1.7, 95% CI=1.2-2.5) [74]. Changes in the NO-cGMP pathway (i.e., elevated levels of NO metabolites alongside decreased cGMP levels) have been suggested as an early event in subjects at risk of T2D. These changes have been correlated with the degree of insulin resistance, e.g., a negative correlation between insulinmediated glucose disposal with circulating NO metabolites and a positive correlation between cGMP levels and insulin sensitivity index [75]. Both increased and decreased circulating concentrations, and renal excretion of NO metabolites have been reported in patients with T2D [76, 77]. Table 2 summarizes current evidence reported serum NO metabolites in patients with T2D and metabolic disorders. An elevated mean fasting serum concentration of NO metabolites (34.6 µM, 95% CI=31.3-38.2 e.g. 30.2 µM, 95% CI=27.9-32.6) was reported in T2D compared to healthy subjects [78]. Table 2. Serum concentrations of NO metabolites (i.e., nitrate+nitrite) in patients with metabolic dysfunction. Author

Sample Size

Age (Year)

Serum Concentrations of NO Metabolites (µM)

Pereira et al. [83]

39

53.3±9.0

8.34 (6.3-15.2) †

Ghasemi et al. [84]

65M+85F

20-87

34.1 (29.5-39.6) ‡ in M and 32.0 ‡ in F

Manju et al. [81]

32

51.7±16.8

18.8±1.8

Manju et al. [81]

28

51.6±18.2

14.34± 2.9

Ghasemi et al. [84]

153M+165F

20-87

30.9 ‡ in M and 29.0 ‡ in F

Shahid et al. [85]

210

54.8±9.7

10.9±2.1

Gosh et al. [86]

50

49.0±7.9

58.8±12.8

Vanizor et al. [87]

30

50.0±10.0

16.8±11.0

Caimi et al. [88]

63

58.9±6.0

78.1±20.8

Values are reported as mean ± SD, median and inter-quartile range (†), or geometric mean (‡). F, female; HTN, hypertension; M, male; NO, nitric oxide; T2D, type 2 diabetes; MetS, metabolic syndrome

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Serum NOx level was higher in patients with T2D and prediabetes than in subjects with normal glycemic control (53.4 and 51.6 μM e.g. 45.6 μM) [79]. In patients with T2D, circulating NO metabolites were also positively correlated with fasting blood glucose and hemoglobin A1C levels [80, 81]. Compared to healthy subjects, those with T2D had also higher circulating NO metabolites and lower urinary NO (31.3±11.8 e.g. 25.6±4.9 μM; 541±302 e.g. 842±451 μM); fasting urinary NO metabolites to creatinine ratio, proposed as an index of endogenous NO synthesis, did not differ in patients with T2D and healthy subjects (0.55±0.15 e.g. 0.53±0.22) [82]. A pooled analysis of 22 studies [77] estimated the weighted mean difference (WMD) of circulating levels of NO metabolites in patients with T2D and nondiabetic subjects, confirmed an elevated value of ~18 µM among European and Asian populations with T2D (WMD=18.7 µM, 95% CI=1.67-35.8, and WMD=18.4 µM, 95% CI=8.01-28.8). Taken together, although most studies reported elevated serum concentrations of NO metabolites in patients with T2D, it should be noted that circulating NOx is not an accurate indicator of endogenous NO synthesis and its bioavailability, especially eNOS-derived NO. Higher plasma NOx levels may not truly be translated to higher functional NO in the circulation; this idea is supported by evidence indicating higher basal NO levels concurrent with lower cGMP (second messenger of NO) levels in subjects with a higher risk of T2D [75]. One should also remember that our diet significantly contributes to the body pool of circulating nitrate and nitrite. Therefore, one must consider if the data was collected during fasting or non-fasting conditions (this contributes to the variable absolute values among studies). Another factor likely contributing to the increased NOx levels during T2D is iNOS activation, which possibly occurred in response to elevated levels of insulin, pro-inflammatory cytokines, and oxidative stress [89, 90]. Underlying Mechanisms of Impaired NO Metabolism/Action in T2D The underlying mechanisms resulting in impaired NO metabolism in T2D are summarized as three main categories: (1) impaired NO production [by impairing either L-arginine-NOS-NO pathway (i.e., decreased cNOS-derived NO and increased iNOS-derived NO) and NO3-NO2-NO pathway], (2) impaired NO transport system, and (3) impaired NO signaling (e.g.,via ROS-induced NO quenching and impaired NO-cGMP cascade) Table 3.

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Table 3. The proposed mechanisms resulting in impaired nitric oxide (NO) metabolism or action in type 2 diabetes (T2D). Mechanisms

Explanation

Suppressed L-arginine-cNOS pathway

Impaired NO synthesis

Overactivity of the L-arginin-iNOS pathway

Suppressed NO3-NO2-NO pathway

↓eNOS expression (hyperglycemia→ ↑AGEs, activation of COX→↑ TXA2→PKC) ↓eNOS activity (due to ↑FFA→ activation of TLR4/TLR2 and NF-kB→ ↓PI3K-Akt) Substrate deficiency for eNOS (due to ↑arginase activity and ↓ L-arginine bioavailability) Competitive inhibition of the NOS-NO synthesis due to ↑ADMA levels The dysfunctionality of eNOS, i.e., eNOS uncoupling (due to ↑BH4 oxidation and depletion, ↓ L-arginine availability, ↑ ROS) Changes in expression of cofactors of eNOS-complex ↑iNOS expression and activity ↓Oral conversion of NO3 to NO2 (due to dysbiosis of oral microbiota, ↓salivary flow rate, ↑oral pH) ↓Gastric conversion of NO2 to NO (due to ↓gastric ascorbic acid release and concentration, gastric atrophy, ↑gastric pH)

Impaired NO transport system

The dysfunctionality of RBCs in transporting NO within the circulation and its delivery into target cells (↓Hb-SNO and ↑Hb-NO) ↓ SNOs synthesis

Impaired NO signaling

NO quenching (e.g., by superoxide anions) ↓Endogenous S-nitrosylated proteins

ADMA, Asymmetric dimethylarginine; AGEs, advanced glycation end products; BH4, tetrahydrobiopterin; cNOS, constitutive nitric oxide synthase; COX, cyclooxygenase; eNOS, endothelial NO synthase; Hb-NO, heme iron-nitrosyl-Hb; Hb-SNO, S-nitrosohemoglobin; iNOS, inducible NOS; NF-kB, nuclear factor-kB; NO2, nitrite; NO3, nitrate; PI3K, phosphoinositide 3-kinases; PKB/Akt, protein kinase B; PKC, protein kinase C; RBC, red blood cell; SNOs, S-nitroso species; TLR4/TLR2, Toll-Like receptor 4/2; TXA2, prostanoid thromboxane A2.

Impaired L-Arginine NOS-NO Pathway The known mechanisms leading to NO deficiency in insulin resistance and T2D have been discussed by our group [91] and others [92, 93]. Decreased NO synthesis is mainly attributed to decreased eNOS expression or activity [6], substrate deficiency for NOSs [due to increased arginase activity and decreased L-arginine availability [94, 95], eNOS uncoupling [due to elevated ROS,

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oxidation of tetrahydrobiopterin (BH4), depletion of L-arginine, and accumulation of methylarginines] resulting in superoxide anion instead of NO production [96]. Hyperglycemia and elevated levels of advanced glycosylation end products (AGEs) may inhibit eNOS expression/activity [97] by enhancing the expression/activity of the cyclooxygenase (COX) and increasing the production of prostanoid thromboxane A2 (TXA2) [98], and activating protein kinase C (PKC) pathway [99]. Increased cytokines levels (e.g., TNF-α) commonly occurred in T2D [100], downregulates the expression eNOS by destabilizing eNOS transcripts [101], decreasing in eNOS promoter activity [102], and decreasing the stability of eNOS mRNA (via translation elongation factor 1-α1; eEF1A1) [103]. Increased circulating free fatty acids (FFA) in T2D may also activate Toll-Like receptor 4/2 (TLR4)/(TLR2) and nuclear factor-kB (NF-κB), leading to decreased PI3K-Akt-mediated phosphorylation of eNOS at Serine1177 and thereby decreased eNOS activity [104]. Increased ROS and oxidative pathways in T2D and insulin resistance can also inhibit the PI3K-Akt-eNOS pathway resulting in decreased eNOS phosphorylation and NO synthesis [27]. Since promoter regions of eNOS gene contain putative binding sites for redoxsensitive transcription factors, [i.e., activator protein-1 (AP-1), serine/proline motif-1 (Sp1), and antioxidant-responsive elements] [105], increased hyperglycemia-induced ROS production and oxidative stress modulate eNOS [106]. Hyperglycemia-induced superoxide anion production decreases eNOS expression via AP-1 DNA-binding activity [106]. Hyperglycemia-induced activation of the hexosamine pathway increases O-linked N-acetylglucosamine (GlcNAc) via activation of the NF-κB pathway and decreases O-linked phosphorylation of the Sp1, leading to decreased eNOS gene expression [107]. Hyperglycemia-induced activation of the hexosamine pathway (via increased mitochondrial superoxide anion production) also decreases eNOS phosphorylation at Serine1177 [108]. In patients with T2D, a markedly reduced basal NOS activity was reported in the skeletal muscle compared to normal-glycemic subjects (101±33 e.g. 457±164 pmol/min*mg protein). Moreover, in response to insulin, NOS activity remained unchanged in diabetic subjects (86±28 pmol/min/mg protein) while it was increased by 2.5-fold in controls (934±282 pmol/min/mg protein) [109]. Moreover, insulin-stimulated NOS activity was inversely related to fasting plasma insulin levels and positively associated with insulin-stimulated glucose disposal [109]. T2D-induced changes in the expression of regulatory components of eNOS activity have also been suggested to decrease eNOS-derived NO production. Maintaining normal eNOS activity depends on the membrane-associated

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scaffolding protein caveolin-1 (Cav-1) and phosphatase and tensin homolog (PTEN) [110]. Expressions of Cav-1 [111] and PTEN [112] are higher in T2D, and both negatively regulate eNOS activity [111, 113]. PTEN upregulation in T2D is probably due to hypomethylation of gene promoter [113] and is associated with T2D and insulin resistance [112]. Oxidative stress diminishes the regulatory functions of PTEN and Cav-1, leading to impaired eNOS activity [110]. The diabetes-induced dysfunctionality of eNOS (eNOS uncoupling, in part due to increased BH4 oxidation and depletion, decreased L-arginine availability, and elevated ROS levels) is another mechanism that contributes to NO deficiency. Increased oxidation of BH4 (a critical cofactor of NOS enzymes), rather than BH4 depletion per se, potentiates NO insufficiency in hyperglycemia and T2D [114]. The NO deficiency in T2D is partly attributable to the substrate deficiency, i.e., decreased bioavailability of L-arginine for the NOS-NO pathway. Several mechanisms are responsible for decreased L-arginine bioavailability. Evidence indicates that arginase, a critical enzyme in the urea cycle competing directly with eNOS for the substrate L-arginine to produce urea and L-ornithine, is overexpressed [115] and over-activated [116, 117]. Over-expression/activity of the arginase is related to diabetes-induced ROS production and initiates a feedforward cycle of decreased NO availability and oxidative stress [118]. In patients with T2D, plasma arginase activity was increased by 50% compared to normalglycemic subjects (0.48±0.11 e.g. 0.32±0.12 µmol/ml/h) [116]. In vitro, highglucose concentrations caused a 66.7% increased arginase activity leading to a 27% decreased NO production in bovine aortic endothelial cells [117]. An elevated level of asymmetric dimethylarginine (NG, NG-dimethyl-L-arginine, ADMA), an endogenous competitive inhibitor of NOSs, in T2D and insulin resistance [116], is also involved in substrate deficiency for NOS enzymes. In patients with T2D, plasma ADMA but no other methylated arginines (symmetric dimethylarginine, SDMA, and monomethyl-L-arginine, MMA) was increased (0.48±0.04 e.g. 0.34±0.04 uM) [116]. About 2-fold elevated circulatory ADMA was reported in untreated patients with T2D than in normal-glycemic subjects (1.59±0.22 e.g. 0.69±0.04 µM) [119]. The L-arginine-to-ADMA ratio, indicating L-arginine bioavailability, was significantly lower in T2D compared to healthy adults (196±67 e.g. 225±86 [120]; 57±6 e.g. 78±5 [116]). In addition to inhibiting NOS activity, ADMA reduces NOS expression, leading to NOS uncoupling, increased superoxide generation, and subsequent oxidative stress [121, 122]. As discussed in Chapter 4, elevated circulatory and intracellular ADMA levels in T2D may be due to overexpression/activity of the protein arginine methyltransferases (PRMT-1) and decreased catabolism of ADMA (because of

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decreased expression/activity of dimethylarginine dimethylaminohydrolase, DDAH). On the other hand, increased circulating free-heme occurs in diabetes, impairs Larginine transport across RBC membranes, and increases L-arginine consumption by arginase, leading to dysregulation of L-arginine metabolism and reduced Larginine availability for NO production [123]. In patients with T2D, RBCs tend to catabolize L-arginine to ornithine, citrulline, and urea [124]. Elevated RBCarginase activity in patients with T2D has been associated with decreased NO bioavailability and endothelial dysfunction [125]. Mitochondrial dysfunctions (e.g., increased activity in complex I and II and decreased activity of complex II and IV [126]) may lead to increased ROS production and impaired NO bioavailability in T2D [127]. Mitochondrial NOS (mtNOS), the alpha isoform of nNOS [nNOSα] acylated at threonine (Thr) or serine (Ser) residues and phosphorylated at the C-terminus, is responsible for mitochondrial NO production [128]. Hyperglycemia switches mtNOS to its uncoupled form (i.e., changing from a NO-generating enzyme to a superoxideproducing enzyme), decreasing NO bioavailability in endothelial cells [129]. On the other hand, an excessive amount of mitochondrial NO, leading to detrimental events including inhibition of the respiratory chain, ROS overproduction, cytochrome c release, and nitration of mitochondrial proteins [130], may occur in T2D because of increased mtNOS activity/expression. An increased mtNOS activity in hepatocytes during insulin resistance has been reported to promote peroxynitrite production and cytochrome c release, peroxidation of mitochondrial lipids, and apoptosis [131]. In skeletal muscle, mtNOS activity is regulated by insulin through the insulin-p-Akt2 pathway, enhancing skeletal muscle glucose uptake; a long-lasting insulin-induced mtNOS overactivity under hyperinsulinemia leads to excessive NO production, mitochondrial dysfunction, and progression of insulin resistance to metabolic disorders [132]. Current evidence indicates that iNOS protein is overexpressed in pancreatic islets of patients with T2D and its inhibition restores disturbed GSIS [32]. iNOSderived high levels of NO can be toxic for pancreatic β-cell, contributing to β-cell dysfunction, impaired insulin secretion, hyperglycemia, and the development of T2D [4]. Impaired NO3-NO2-NO Pathway Several factors involved in the NO3-NO2-NO pathway [i.e., composition and diversity of commensal oral-gut microbiota [133 - 135], redox environment affecting the reducing capacity of NO3 to NO2 and from NO2 to NO, e.g., oral and stomach pH, reducing agents like ascorbic acid [136 - 138], and NO3-NO2

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reductase enzymes ] seem to be changed in T2D [82]. Since NO production from the NO3-NO2-NO pathway is critically dependent upon oral commensal NO3reducing bacteria [139, 140], oral dysbiosis of these communities and decreased oral NO3 reductase capacity commonly occur in dysglycemia [141, 142] seems partially to be responsible for decreased NO availability in T2D and insulin resistance (for more details, see chapter 5). Furthermore, as we discussed elsewhere [143], abnormal metabolism of ascorbic acid in patients with T2D, i.e., decreased circulatory pool of ascorbic acid, increased oxidation of ascorbic acid to dehydroascorbic acid (DHA) by the mitochondria, impaired recycling of DHA to ascorbic acid in the tissues and erythrocytes, decreased gastric ascorbic acid secretion (due to gastric atrophy and chronic gastritis) may be an underlying mechanism that diminishes the efficacy of the NO3-NO2-NO pathway to produce NO in T2D. Increasing NO bioavailability using NO3 and NO2 may have therapeutic applications in T2D [23, 24, 91]. However, this has not yet been confirmed in humans [143]; see chapter 14 for more details. Impaired NO Transport NO is transported within the circulation in both free and bound forms; the most bound forms are red blood cell (RBC)-bound [heme iron-nitrosyl-Hb (Hb-NO) and S-nitrosohemoglobin (Hb-SNO) and plasma S-nitroso species (SNOs), SNOalbumin, S-nitrosoglutathione (GSNO) and S-nitrosocysteine (CySNO) [3]. NO bioavailability has been suggested to be governed partly by its reformation from these circulating metabolites [144 - 146]. As we reviewed elsewhere [3], a dynamic cycle (heme/thiol-NO redox coupling) between circulatory Hb-NO and Hb-SNO [147] enables RBCs to act as SNOs reactors, regulating plasma SNOs levels [148] and delivery of NO into target cells [147, 149]. Although the effect of RBC glycation on NO binding, its transport within the circulation, and its delivery into target tissues is not fully established, glycosylated RBCs are likely to be dysfunctional compared to normal-glycated RBCs [150]. The rate of NO release from Hb-NO, the main NO-bound form in the glycosylated hemoglobin in diabetes [151], is extremely low [152]; furthermore, RBC Hb-SNO content, not Hb-NO content, is related to the physiologic function of NO [150, 153]. Highly-glycated RBCs (indicated as HbA1c more than 10.7%) showed increased NO binding in the form of Hb-NO [150]; both total contents of RBC-NO (0.069 e.g. 0.045 percent NO per Hb mol/L) and Hb-NO (0.044 e.g. 0.013 percent NO per Hb mol/L) was significantly higher in highly-glycated compared to normal-glycated Hb, whereas Hb-SNO (0.025 e.g. 0.032 percent NO per Hb mol/L) was significantly lower [150]. Indeed, NO seems to be trapped

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within the glycosylated hemoglobin in hyperglycemic conditions and cannot be transferred into cells, which may represent an important contribution to reduced NO bioavailability in T2D. NO can cross the plasma membranes of cells by specific connexins (e.g., Cx37, Cx40, Cx43, Cx46 in endothelial cells) [154]. Considering evidence indicating changes in expression pattern and connexins' activity in T2D [155, 156], one can speculate that some part of decreased intracellular NO availability occurs due to impaired delivery of systemic NO into cells. Impaired NO Signaling NO acts through its receptor, soluble guanylyl cyclase (sGC), via the sGC-cGMPprotein kinase G (PKG) pathway or by post-translational modification of target proteins (i.e., S-nitrosylation and tyrosine nitration) [3]. Impairment of these pathways during T2D may lead to reduced NO bioactivity. The NO-cGMP signaling pathway stimulates skeletal muscle glucose uptake independent of both the insulin- and contraction-stimulated mechanisms [60]. Prolongation of NOcGMP-PKG signaling [using phosphodiesterase-5 (PDE-5) inhibitors] has been suggested to increase blood flow, improve skeletal muscle GSIS and thereby decrease plasma glucose level [157]. Impaired NO-cGMP-PKG signaling has been reported in hyperglycemia [157], and altered sensitivity of the NO-cGMP signaling pathway is suggested to be involved in skeletal muscle insulin resistance [158]. CONCLUDING REMARKS Available evidence strongly supports the existence of a cause-and-effect and bilateral relationship between impaired NO metabolism and T2D. Physiologic roles of NO in regulating whole-body glucose and insulin homeostasis are mainly attributed to low-to-moderate levels of eNOS- and nNOS-derived NO, whereas vast overproduction of NO, mainly due to obesity- and cytokine-induced iNOS activity, is primarily responsible for impaired carbohydrate metabolism and development of insulin resistance. Impaired function of the classical L-arginin-dependent constitutive NOS systems and abnormal regulation of the alternative NO3-NO2-NO pathway have been associated with the development of T2D and its complications. The underlying mechanisms are complex, but further understanding of the pathological mechanisms and the value of restoring NO balance will hopefully aid in the development of new therapeutic strategies to battle insulin resistance and T2D.

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CONFLICT OF INTEREST None Declare ACKNOWLEDGEMENT None CONSENT OF PUBLICATION Permission from EXCLI Journal for Fig. (1) REFERENCES [1]

Murad F. Discovery of some of the biological effects of nitric oxide and its role in cell signaling. Biosci Rep 2004; 24(4-5): 452-74. [http://dx.doi.org/10.1007/s10540-005-2741-8] [PMID: 16134022]

[2]

Ghasemi A, Zahediasl S. Is nitric oxide a hormone? Iran Biomed J 2011; 15(3): 59-65. [PMID: 21987110]

[3]

Bahadoran Z CM, Mirmiran P, Ghasemi A. 2020.

[4]

Bahadoran Z, Mirmiran P, Ghasemi A. Role of Nitric Oxide in Insulin Secretion and Glucose Metabolism. Trends Endocrinol Metab 2020; 31(2): 118-30. [http://dx.doi.org/10.1016/j.tem.2019.10.001] [PMID: 31690508]

[5]

Ghasemi A. Quantitative aspects of nitric oxide production from nitrate and nitrite. EXCLI J 2022; 21: 470-86. [PMID: 35391922]

[6]

Tessari P, Cecchet D, Cosma A, et al. Nitric oxide synthesis is reduced in subjects with type 2 diabetes and nephropathy. Diabetes 2010; 59(9): 2152-9. [http://dx.doi.org/10.2337/db09-1772] [PMID: 20484137]

[7]

Lin KY, Ito A, Asagami T, et al. Impaired nitric oxide synthase pathway in diabetes mellitus: role of asymmetric dimethylarginine and dimethylarginine dimethylaminohydrolase. Circulation 2002; 106(8): 987-92. [http://dx.doi.org/10.1161/01.CIR.0000027109.14149.67] [PMID: 12186805]

[8]

Shankar RR, Wu Y, Shen HQ, Zhu JS, Baron AD. Mice with gene disruption of both endothelial and neuronal nitric oxide synthase exhibit insulin resistance. Diabetes 2000; 49(5): 684-7. [http://dx.doi.org/10.2337/diabetes.49.5.684] [PMID: 10905473]

[9]

Duplain H, Burcelin R, Sartori C, et al. Insulin resistance, hyperlipidemia, and hypertension in mice lacking endothelial nitric oxide synthase. Circulation 2001; 104(3): 342-5. [http://dx.doi.org/10.1161/01.CIR.104.3.342] [PMID: 11457755]

[10]

Cook S, Hugli O, Egli M, et al. Clustering of cardiovascular risk factors mimicking the human metabolic syndrome X in eNOS null mice. Swiss Med Wkly 2003; 133(25-26): 360-3. [PMID: 12947532]

[11]

Carlström M, Larsen FJ, Nyström T, et al. Dietary inorganic nitrate reverses features of metabolic syndrome in endothelial nitric oxide synthase-deficient mice. Proc Natl Acad Sci USA 2010; 107(41): 17716-20. [http://dx.doi.org/10.1073/pnas.1008872107] [PMID: 20876122]

[12]

Cook S, Hugli O, Egli M, et al. Partial gene deletion of endothelial nitric oxide synthase predisposes to exaggerated high-fat diet-induced insulin resistance and arterial hypertension. Diabetes 2004; 53(8):

56 The Role of Nitric Oxide in Type 2 Diabetes

Bahadoran et al.

2067-72. [http://dx.doi.org/10.2337/diabetes.53.8.2067] [PMID: 15277387] [13]

Sansbury BE, Cummins TD, Tang Y, et al. Overexpression of endothelial nitric oxide synthase prevents diet-induced obesity and regulates adipocyte phenotype. Circ Res 2012; 111(9): 1176-89. [http://dx.doi.org/10.1161/CIRCRESAHA.112.266395] [PMID: 22896587]

[14]

Ohashi Y, Kawashima S, Hirata K, et al. Hypotension and reduced nitric oxide-elicited vasorelaxation in transgenic mice overexpressing endothelial nitric oxide synthase. J Clin Invest 1998; 102(12): 2061-71. [http://dx.doi.org/10.1172/JCI4394] [PMID: 9854041]

[15]

Carvalho-Filho MA, Ueno M, Hirabara SM, et al. S-nitrosation of the insulin receptor, insulin receptor substrate 1, and protein kinase B/Akt: a novel mechanism of insulin resistance. Diabetes 2005; 54(4): 959-67. [http://dx.doi.org/10.2337/diabetes.54.4.959] [PMID: 15793233]

[16]

Shinozaki S, Choi CS, Shimizu N, et al. Liver-specific inducible nitric-oxide synthase expression is sufficient to cause hepatic insulin resistance and mild hyperglycemia in mice. J Biol Chem 2011; 286(40): 34959-75. [http://dx.doi.org/10.1074/jbc.M110.187666] [PMID: 21846719]

[17]

Perreault M, Marette A. Targeted disruption of inducible nitric oxide synthase protects against obesity-linked insulin resistance in muscle. Nat Med 2001; 7(10): 1138-43. [http://dx.doi.org/10.1038/nm1001-1138] [PMID: 11590438]

[18]

Thameem F, Puppala S, Arar NH, et al. Endothelial nitric oxide synthase (eNOS) gene polymorphisms and their association with type 2 diabetes-related traits in Mexican Americans. Diab Vasc Dis Res 2008; 5(2): 109-13. [http://dx.doi.org/10.3132/dvdr.2008.018] [PMID: 18537098]

[19]

Moguib O, Raslan HM, Abdel Rasheed I, et al. Endothelial nitric oxide synthase gene (T786C and G894T) polymorphisms in Egyptian patients with type 2 diabetes. J Genet Eng Biotechnol 2017; 15(2): 431-6. [http://dx.doi.org/10.1016/j.jgeb.2017.05.001] [PMID: 30647683]

[20]

Monti LD, Barlassina C, Citterio L, et al. Endothelial nitric oxide synthase polymorphisms are associated with type 2 diabetes and the insulin resistance syndrome. Diabetes 2003; 52(5): 1270-5. [http://dx.doi.org/10.2337/diabetes.52.5.1270] [PMID: 12716763]

[21]

Tsukada T, Yokoyama K, Arai T, et al. Evidence of association of the ecNOS gene polymorphism with plasma NO metabolite levels in humans. Biochem Biophys Res Commun 1998; 245(1): 190-3. [http://dx.doi.org/10.1006/bbrc.1998.8267] [PMID: 9535806]

[22]

Jia Z, Zhang X, Kang S, Wu Y. Association of endothelial nitric oxide synthase gene polymorphisms with type 2 diabetes mellitus: A meta-analysis. Endocr J 2013; 60(7): 893-901. [http://dx.doi.org/10.1507/endocrj.EJ12-0463] [PMID: 23563728]

[23]

Carlström M. Nitric oxide signalling in kidney regulation and cardiometabolic health. Nat Rev Nephrol 2021; 17(9): 575-90. [http://dx.doi.org/10.1038/s41581-021-00429-z] [PMID: 34075241]

[24]

Lundberg JO, Carlström M, Weitzberg E. Metabolic Effects of Dietary Nitrate in Health and Disease. Cell Metab 2018; 28(1): 9-22. [http://dx.doi.org/10.1016/j.cmet.2018.06.007] [PMID: 29972800]

[25]

Schiffer TA, Lundberg JO, Weitzberg E, Carlström M. Modulation of mitochondria and NADPH oxidase function by the nitrate-nitrite-NO pathway in metabolic disease with focus on type 2 diabetes. Biochim Biophys Acta Mol Basis Dis 2020; 1866(8): 165811. [http://dx.doi.org/10.1016/j.bbadis.2020.165811] [PMID: 32339643]

[26]

Kapil V, Khambata RS, Jones DA, et al. The Noncanonical Pathway for In Vivo Nitric Oxide

Impaired NO 0etabolism in T2D

The Role of Nitric Oxide in Type 2 Diabetes 57

Generation: The Nitrate-Nitrite-Nitric Oxide Pathway. Pharmacol Rev 2020; 72(3): 692-766. [http://dx.doi.org/10.1124/pr.120.019240] [PMID: 32576603] [27]

Kobayashi J. Nitric oxide and insulin resistance. Immunoendocrinology (Houst) 2015; 2.

[28]

Gheibi S, Ghasemi A. Insulin secretion: The nitric oxide controversy. EXCLI J 2020; 19: 1227-45. [PMID: 33088259]

[29]

Smukler SR, Tang L, Wheeler MB, Salapatek AMF. Exogenous nitric oxide and endogenous glucosestimulated beta-cell nitric oxide augment insulin release. Diabetes 2002; 51(12): 3450-60. [http://dx.doi.org/10.2337/diabetes.51.12.3450] [PMID: 12453899]

[30]

Spinas GA, Laffranchi R, Francoys I, David I, Richter C, Reinecke M. The early phase of glucosestimulated insulin secretion requires nitric oxide. Diabetologia 1998; 41(3): 292-9. [http://dx.doi.org/10.1007/s001250050906] [PMID: 9541169]

[31]

Kaneko Y, Ishikawa T, Amano S, Nakayama K. Dual effect of nitric oxide on cytosolic Ca 2+ concentration and insulin secretion in rat pancreatic β-cells. Am J Physiol Cell Physiol 2003; 284(5): C1215-22. [http://dx.doi.org/10.1152/ajpcell.00223.2002] [PMID: 12529241]

[32]

Muhammed SJ, Lundquist I, Salehi A. Pancreatic β-cell dysfunction, expression of iNOS and the effect of phosphodiesterase inhibitors in human pancreatic islets of type 2 diabetes. Diabetes Obes Metab 2012; 14(11): 1010-9. [http://dx.doi.org/10.1111/j.1463-1326.2012.01632.x] [PMID: 22687049]

[33]

Eckersten D, Henningsson R. Nitric oxide (NO) — Production and regulation of insulin secretion in islets of freely fed and fasted mice. Regul Pept 2012; 174(1-3): 32-7. [http://dx.doi.org/10.1016/j.regpep.2011.11.006] [PMID: 22120830]

[34]

Kim JY, Song EH, Lee HJ, et al. Chronic ethanol consumption-induced pancreatic beta-cell dysfunction and apoptosis through glucokinase nitration and its down-regulation. J Biol Chem 2010; 285(48): 37251-62. [http://dx.doi.org/10.1074/jbc.M110.142315] [PMID: 20855893]

[35]

Henningsson R, Salehi A, Lundquist I. Role of nitric oxide synthase isoforms in glucose-stimulated insulin release. Am J Physiol Cell Physiol 2002; 283(1): C296-304. [http://dx.doi.org/10.1152/ajpcell.00537.2001] [PMID: 12055099]

[36]

Tsuura Y, Ishida H, Hayashi S, Sakamoto K, Horie M, Seino Y. Nitric oxide opens ATP-sensitive K+ channels through suppression of phosphofructokinase activity and inhibits glucose-induced insulin release in pancreatic beta cells. J Gen Physiol 1994; 104(6): 1079-98. [http://dx.doi.org/10.1085/jgp.104.6.1079] [PMID: 7699364]

[37]

Corbett JA, Sweetland MA, Wang JL, Lancaster JR Jr, McDaniel ML. Nitric oxide mediates cytokineinduced inhibition of insulin secretion by human islets of Langerhans. Proc Natl Acad Sci USA 1993; 90(5): 1731-5. [http://dx.doi.org/10.1073/pnas.90.5.1731] [PMID: 8383325]

[38]

Panagiotidis G, Åkesson B, Rydell EL, Lundquist I. Influence of nitric oxide synthase inhibition, nitric oxide and hydroperoxide on insulin release induced by various secretagogues. Br J Pharmacol 1995; 114(2): 289-96. [http://dx.doi.org/10.1111/j.1476-5381.1995.tb13225.x] [PMID: 7533613]

[39]

McConell GK, Rattigan S, Lee-Young RS, Wadley GD, Merry TL. Skeletal muscle nitric oxide signaling and exercise: a focus on glucose metabolism. Am J Physiol Endocrinol Metab 2012; 303(3): E301-7. [http://dx.doi.org/10.1152/ajpendo.00667.2011] [PMID: 22550064]

[40]

Stamler JS, Meissner G. Physiology of nitric oxide in skeletal muscle. Physiol Rev 2001; 81(1): 20937. [http://dx.doi.org/10.1152/physrev.2001.81.1.209] [PMID: 11152758]

58 The Role of Nitric Oxide in Type 2 Diabetes

Bahadoran et al.

[41]

Wang H, Wang AX, Aylor K, Barrett EJ. Nitric oxide directly promotes vascular endothelial insulin transport. Diabetes 2013; 62(12): 4030-42. [http://dx.doi.org/10.2337/db13-0627] [PMID: 23863813]

[42]

Eghbalzadeh K, Brixius K, Bloch W, Brinkmann C. Skeletal muscle nitric oxide (NO) synthases and NO-signaling in "diabesity"--what about the relevance of exercise training interventions? Nitric oxide : biology and chemistry. 2014; 37: 28-40.

[43]

Lira VA, Soltow QA, Long JHD, Betters JL, Sellman JE, Criswell DS. Nitric oxide increases GLUT4 expression and regulates AMPK signaling in skeletal muscle. Am J Physiol Endocrinol Metab 2007; 293(4): E1062-8. [http://dx.doi.org/10.1152/ajpendo.00045.2007] [PMID: 17666490]

[44]

Roy D, Perreault M, Marette A. Insulin stimulation of glucose uptake in skeletal muscles and adipose tissues in vivo is NO dependent. Am J Physiol 1998; 274(4): E692-9. [PMID: 9575831]

[45]

Tanaka T, Nakatani K, Morioka K, et al. Nitric oxide stimulates glucose transport through insulinindependent GLUT4 translocation in 3T3-L1 adipocytes. Eur J Endocrinol 2003; 149(1): 61-7. [http://dx.doi.org/10.1530/eje.0.1490061] [PMID: 12824867]

[46]

Engeli S, Janke J, Gorzelniak K, et al. Regulation of the nitric oxide system in human adipose tissue. J Lipid Res 2004; 45(9): 1640-8. [http://dx.doi.org/10.1194/jlr.M300322-JLR200] [PMID: 15231849]

[47]

Xia N, Horke S, Habermeier A, et al. Uncoupling of Endothelial Nitric Oxide Synthase in Perivascular Adipose Tissue of Diet-Induced Obese Mice. Arterioscler Thromb Vasc Biol 2016; 36(1): 78-85. [http://dx.doi.org/10.1161/ATVBAHA.115.306263] [PMID: 26586660]

[48]

Jang JE, Ko MS, Yun JY, et al. Nitric Oxide Produced by Macrophages Inhibits Adipocyte Differentiation and Promotes Profibrogenic Responses in Preadipocytes to Induce Adipose Tissue Fibrosis. Diabetes 2016; 65(9): 2516-28. [http://dx.doi.org/10.2337/db15-1624] [PMID: 27246913]

[49]

Abudukadier A, Fujita Y, Obara A, et al. Tetrahydrobiopterin has a glucose-lowering effect by suppressing hepatic gluconeogenesis in an endothelial nitric oxide synthase-dependent manner in diabetic mice. Diabetes 2013; 62(9): 3033-43. [http://dx.doi.org/10.2337/db12-1242] [PMID: 23649519]

[50]

Sadri P, Lautt WW. Blockade of hepatic nitric oxide synthase causes insulin resistance. Am J Physiol 1999; 277(1): G101-8. [PMID: 10409156]

[51]

Horton RA, Ceppi ED, Knowles RG, Titheradge MA. Inhibition of hepatic gluconeogenesis by nitric oxide: a comparison with endotoxic shock. Biochem J 1994; 299(3): 735-9. [http://dx.doi.org/10.1042/bj2990735] [PMID: 8192661]

[52]

Molina y Vedia L, McDonald B, Reep B, et al. Nitric oxide-induced S-nitrosylation of glyceraldehyde-3-phosphate dehydrogenase inhibits enzymatic activity and increases endogenous ADP-ribosylation. J Biol Chem 1992; 267(35): 24929-32. [http://dx.doi.org/10.1016/S0021-9258(19)73985-4] [PMID: 1281150]

[53]

Charbonneau A, Marette A. Inducible nitric oxide synthase induction underlies lipid-induced hepatic insulin resistance in mice: potential role of tyrosine nitration of insulin signaling proteins. Diabetes 2010; 59(4): 861-71. [http://dx.doi.org/10.2337/db09-1238] [PMID: 20103705]

[54]

Chachlaki K, Malone SA, Qualls-Creekmore E, et al. Phenotyping of nNOS neurons in the postnatal and adult female mouse hypothalamus. J Comp Neurol 2017; 525(15): 3177-89. [http://dx.doi.org/10.1002/cne.24257] [PMID: 28577305]

[55]

Fioramonti X, Marsollier N, Song Z, et al. Ventromedial hypothalamic nitric oxide production is

Impaired NO 0etabolism in T2D

The Role of Nitric Oxide in Type 2 Diabetes 59

necessary for hypoglycemia detection and counterregulation. Diabetes 2010; 59(2): 519-28. [http://dx.doi.org/10.2337/db09-0421] [PMID: 19934009] [56]

Laffranchi R, Gogvadze V, Richter C, Spinas GA. Nitric oxide (nitrogen monoxide, NO) stimulates insulin secretion by inducing calcium release from mitochondria. Biochem Biophys Res Commun 1995; 217(2): 584-91. [http://dx.doi.org/10.1006/bbrc.1995.2815] [PMID: 7503739]

[57]

Willmott NJ, Galione A, Smith PA. Nitric oxide induces intracellular Ca 2+ mobilization and increases secretion of incorporated 5-hydroxytryptamine in rat pancreatic β-cells. FEBS Lett 1995; 371(2): 99104. [http://dx.doi.org/10.1016/0014-5793(95)00848-4] [PMID: 7672132]

[58]

Rizzo MA, Piston DW. Regulation of β cell glucokinase by S-nitrosylation and association with nitric oxide synthase. J Cell Biol 2003; 161(2): 243-8. [http://dx.doi.org/10.1083/jcb.200301063] [PMID: 12707306]

[59]

Baron AD, Clark MG. Role of blood flow in the regulation of muscle glucose uptake. Annu Rev Nutr 1997; 17(1): 487-99. [http://dx.doi.org/10.1146/annurev.nutr.17.1.487] [PMID: 9240937]

[60]

Etgen GJ Jr, Fryburg DA, Gibbs EM. Nitric oxide stimulates skeletal muscle glucose transport through a calcium/contraction- and phosphatidylinositol-3-kinase-independent pathway. Diabetes 1997; 46(11): 1915-9. [http://dx.doi.org/10.2337/diab.46.11.1915] [PMID: 9356048]

[61]

Sugita H, Fujimoto M, Yasukawa T, et al. Inducible nitric-oxide synthase and NO donor induce insulin receptor substrate-1 degradation in skeletal muscle cells. J Biol Chem 2005; 280(14): 1420311. [http://dx.doi.org/10.1074/jbc.M411226200] [PMID: 15805118]

[62]

Ribière C, Jaubert AM, Sabourault D, Lacasa D, Giudicelli Y. Insulin stimulates nitric oxide production in rat adipocytes. Biochem Biophys Res Commun 2002; 291(2): 394-9. [http://dx.doi.org/10.1006/bbrc.2002.6444] [PMID: 11846418]

[63]

Giordano A, Tonello C, Bulbarelli A, et al. Evidence for a functional nitric oxide synthase system in brown adipocyte nucleus. FEBS Lett 2002; 514(2-3): 135-40. [http://dx.doi.org/10.1016/S0014-5793(02)02245-7] [PMID: 11943139]

[64]

Nisoli E, Tonello C, Briscini L, Carruba MO. Inducible nitric oxide synthase in rat brown adipocytes: implications for blood flow to brown adipose tissue. Endocrinology 1997; 138(2): 676-82. [http://dx.doi.org/10.1210/endo.138.2.4956] [PMID: 9003002]

[65]

Eipel C, Abshagen K, Vollmar B. Regulation of hepatic blood flow: The hepatic arterial buffer response revisited. World J Gastroenterol 2010; 16(48): 6046-57. [http://dx.doi.org/10.3748/wjg.v16.i48.6046] [PMID: 21182219]

[66]

Shepherd AI, Wilkerson DP, Fulford J, et al. Effect of nitrate supplementation on hepatic blood flow and glucose homeostasis: a double-blind, placebo-controlled, randomized control trial. Am J Physiol Gastrointest Liver Physiol 2016; 311(3): G356-64. [http://dx.doi.org/10.1152/ajpgi.00203.2016] [PMID: 27418682]

[67]

Duparc T, Colom A, Cani PD, et al. Central apelin controls glucose homeostasis via a nitric oxidedependent pathway in mice. Antioxid Redox Signal 2011; 15(6): 1477-96. [http://dx.doi.org/10.1089/ars.2010.3454] [PMID: 21395477]

[68]

Abtahi S, Mirza A, Howell E, Currie PJ. Ghrelin enhances food intake and carbohydrate oxidation in a nitric oxide dependent manner. Gen Comp Endocrinol 2017; 250: 9-14. [http://dx.doi.org/10.1016/j.ygcen.2017.05.017] [PMID: 28552460]

[69]

Leshan RL, Greenwald-Yarnell M, Patterson CM, Gonzalez IE, Myers MG Jr. Leptin action through hypothalamic nitric oxide synthase-1–expressing neurons controls energy balance. Nat Med 2012;

60 The Role of Nitric Oxide in Type 2 Diabetes

Bahadoran et al.

18(5): 820-3. [http://dx.doi.org/10.1038/nm.2724] [PMID: 22522563] [70]

Marsollier N, Kassis N, Mezghenna K, et al. Deregulation of hepatic insulin sensitivity induced by central lipid infusion in rats is mediated by nitric oxide. PLoS One 2009; 4(8): e6649. [http://dx.doi.org/10.1371/journal.pone.0006649] [PMID: 19680547]

[71]

Tessari P, Coracina A, Puricelli L, et al. Acute effect of insulin on nitric oxide synthesis in humans: a precursor-product isotopic study. Am J Physiol Endocrinol Metab 2007; 293(3): E776-82. [http://dx.doi.org/10.1152/ajpendo.00481.2006] [PMID: 17551000]

[72]

Bahadoran Z, Mirmiran P, Jeddi S, Carlström M, Azizi F, Ghasemi A. Circulating markers of nitric oxide homeostasis and cardiometabolic diseases: insights from population-based studies. Free Radic Res 2019; 53(4): 359-76. [http://dx.doi.org/10.1080/10715762.2019.1587168] [PMID: 30821533]

[73]

Ghasemi A, Zahediasl S, Azizi F. Reference values for serum nitric oxide metabolites in an adult population. Clin Biochem 2010; 43(1-2): 89-94. [http://dx.doi.org/10.1016/j.clinbiochem.2009.09.011] [PMID: 19782059]

[74]

Gumanova NG, Deev AD, Klimushina MV, Kots AY, Shalnova SA. Serum nitrate and nitrite are associated with the prevalence of various chronic diseases except cancer. Int Angiol 2017; 36(2): 1606. [http://dx.doi.org/10.23736/S0392-9590.16.03674-9] [PMID: 26899180]

[75]

Piatti PM, Monti LD, Zavaroni I, et al. Alterations in nitric oxide/cyclic-GMP pathway in nondiabetic siblings of patients with type 2 diabetes. J Clin Endocrinol Metab 2000; 85(7): 2416-20. [http://dx.doi.org/10.1210/jc.85.7.2416] [PMID: 10902787]

[76]

Bahadoran Z, Ghasemi A, Mirmiran P, Azizi F, Hadaegh F. Beneficial effects of inorganic nitrate/nitrite in type 2 diabetes and its complications. Nutr Metab (Lond) 2015; 12(1): 16. [http://dx.doi.org/10.1186/s12986-015-0013-6] [PMID: 25991919]

[77]

Assmann TS, Brondani LA, Boucas AP, Rheinheimer J, de Souza BM, Canani LH, et al. Nitric oxide levels in patients with diabetes mellitus: A systematic review and meta-analysis. 2016. [http://dx.doi.org/10.1016/j.niox.2016.09.009]

[78]

Zahedi Asl S, Ghasemi A, Azizi F. Serum nitric oxide metabolites in subjects with metabolic syndrome. Clin Biochem 2008; 41(16-17): 1342-7. [http://dx.doi.org/10.1016/j.clinbiochem.2008.08.076] [PMID: 18793628]

[79]

Ozcelik O, Algul S. Nitric oxide levels in response to the patients with different stage of diabetes. Cell Mol Biol 2017; 63(1): 49-52. [http://dx.doi.org/10.14715/cmb/2017.63.1.10] [PMID: 28234625]

[80]

Adela R, Nethi SK, Bagul PK, et al. Hyperglycaemia enhances nitric oxide production in diabetes: a study from South Indian patients. PLoS One 2015; 10(4): e0125270. [http://dx.doi.org/10.1371/journal.pone.0125270] [PMID: 25894234]

[81]

Manju M, Mishra S, Toora BD, Vijayakumar , Vinod R. Relationship between Glycosylated Hemoglobin, Serum Nitric Oxide and Mean Arterial Blood Pressure. Int J Biomed Sci 2014; 10(4): 252-7. [PMID: 25598756]

[82]

Bahadoran ZMP, Carlström M, Norouzirad R, Jeddi S, Azizi F, Ghasemi A. Different Pharmacokinetic Response to an Acute Dose of Inorganic Nitrate in Patients with Type 2 Diabetes. Endocr Metab Immune Disord Drug Targets 2020.

[83]

Pereira FO, Frode TS, Medeiros YS. Evaluation of tumour necrosis factor alpha, interleukin-2 soluble receptor, nitric oxide metabolites, and lipids as inflammatory markers in type 2 diabetes mellitus. Mediators Inflamm 2006; 2006(1): 1-7. [http://dx.doi.org/10.1155/MI/2006/39062] [PMID: 16864902]

Impaired NO 0etabolism in T2D

The Role of Nitric Oxide in Type 2 Diabetes 61

[84]

Ghasemi A, Zahediasl S, Azimzadeh I, Azizi F. Increased serum nitric oxide metabolites in dysglycaemia. Ann Hum Biol 2011; 38(5): 577-82. [http://dx.doi.org/10.3109/03014460.2011.575384] [PMID: 21561301]

[85]

Shahid SM, Jawed M, Mahboob T. Relationship between serum nitric oxide and sialic acid in coexisted diabetes, hypertension and nephropathy. Pak J Pharm Sci 2013; 26(3): 593-7. [PMID: 23625435]

[86]

Pal R, Ghosh A, Sherpa ML, Bhutia Y, Dahal S. Serum nitric oxide status in patients with type 2 diabetes mellitus in Sikkim. Int J Appl Basic Med Res 2011; 1(1): 31-5. [http://dx.doi.org/10.4103/2229-516X.81977] [PMID: 23776769]

[87]

Vanizor B, Örem A, Karahan SC, et al. Decreased nitric oxide end-products and its relationship with high density lipoprotein and oxidative stress in people with type 2 diabetes without complications. Diabetes Res Clin Pract 2001; 54(1): 33-9. [http://dx.doi.org/10.1016/S0168-8227(01)00281-9] [PMID: 11532328]

[88]

Caimi G, Hopps E, Montana M, et al. Evaluation of nitric oxide metabolites in a group of subjects with metabolic syndrome. Diabetes Metab Syndr 2012; 6(3): 132-5. [http://dx.doi.org/10.1016/j.dsx.2012.09.012] [PMID: 23158975]

[89]

Kagota S, Yamaguchi Y, Tanaka N, et al. Disturbances in nitric oxide/cyclic guanosine monophosphate system in SHR/NDmcr-cp rats, a model of metabolic syndrome. Life Sci 2006; 78(11): 1187-96. [http://dx.doi.org/10.1016/j.lfs.2005.06.029] [PMID: 16188278]

[90]

Scherrer U, Sartori C. Defective nitric oxide synthesis: a link between metabolic insulin resistance, sympathetic overactivity and cardiovascular morbidity. Eur J Endocrinol 2000; 142(4): 315-23. [http://dx.doi.org/10.1530/eje.0.1420315] [PMID: 10754469]

[91]

Ghasemi A, Jeddi S. Anti-obesity and anti-diabetic effects of nitrate and nitrite. 2017. [http://dx.doi.org/10.1016/j.niox.2017.08.003]

[92]

Avogaro A, Toffolo G, Kiwanuka E, de Kreutzenberg SV, Tessari P, Cobelli C. L-arginine-nitric oxide kinetics in normal and type 2 diabetic subjects: a stable-labelled 15N arginine approach. Diabetes 2003; 52(3): 795-802. [http://dx.doi.org/10.2337/diabetes.52.3.795] [PMID: 12606522]

[93]

Honing MLH, Morrison PJ, Banga JD, Stroes ESG, Rabelink TJ. Nitric oxide availability in diabetes mellitus. Diabetes Metab Rev 1998; 14(3): 241-9. [http://dx.doi.org/10.1002/(SICI)1099-0895(1998090)14:33.0.CO;2-R] [PMID: 9816472]

[94]

Caldwell RB, Zhang W, Rojas M, Bartoli M, El-Remessy AB, Tsai N-T, et al. Decreased Nitric Oxide Bioavailability in Diabetic Retinopathy: Involvement of Arginase Activity. Invest Ophthalmol Vis Sci 2009; 50(13): 32.

[95]

Kövamees O, Shemyakin A, Checa A, et al. Arginase Inhibition Improves Microvascular Endothelial Function in Patients With Type 2 Diabetes Mellitus. J Clin Endocrinol Metab 2016; 101(11): 3952-8. [http://dx.doi.org/10.1210/jc.2016-2007] [PMID: 27399350]

[96]

Faria AM, Papadimitriou A, Silva KC, Lopes de Faria JM, Lopes de Faria JB. Uncoupling endothelial nitric oxide synthase is ameliorated by green tea in experimental diabetes by re-establishing tetrahydrobiopterin levels. Diabetes 2012; 61(7): 1838-47. [http://dx.doi.org/10.2337/db11-1241] [PMID: 22586583]

[97]

Chu S, Bohlen HG. High concentration of glucose inhibits glomerular endothelial eNOS through a PKC mechanism. Am J Physiol Renal Physiol 2004; 287(3): F384-92. [http://dx.doi.org/10.1152/ajprenal.00006.2004] [PMID: 15140758]

[98]

Cosentino F, Eto M, De Paolis P, et al. High glucose causes upregulation of cyclooxygenase-2 and alters prostanoid profile in human endothelial cells: role of protein kinase C and reactive oxygen

62 The Role of Nitric Oxide in Type 2 Diabetes

Bahadoran et al.

species. Circulation 2003; 107(7): 1017-23. [http://dx.doi.org/10.1161/01.CIR.0000051367.92927.07] [PMID: 12600916] [99]

Geraldes P, King GL. Activation of protein kinase C isoforms and its impact on diabetic complications. Circ Res 2010; 106(8): 1319-31. [http://dx.doi.org/10.1161/CIRCRESAHA.110.217117] [PMID: 20431074]

[100] Zatterale F, Longo M, Naderi J, et al. Chronic Adipose Tissue Inflammation Linking Obesity to Insulin Resistance and Type 2 Diabetes. Front Physiol 2020; 10: 1607. [http://dx.doi.org/10.3389/fphys.2019.01607] [PMID: 32063863] [101] Lai P, Mohamed F, Monge JC, Stewart DJ. Downregulation of eNOS mRNA expression by TNFα: identification and functional characterization of RNA–protein interactions in the 3′UTR. Cardiovasc Res 2003; 59(1): 160-8. [http://dx.doi.org/10.1016/S0008-6363(03)00296-7] [PMID: 12829187] [102] Neumann P, Gertzberg N, Johnson A. TNF-α induces a decrease in eNOS promoter activity. Am J Physiol Lung Cell Mol Physiol 2004; 286(2): L452-9. [http://dx.doi.org/10.1152/ajplung.00378.2002] [PMID: 14555463] [103] Yan G, You B, Chen SP, Liao JK, Sun J. Tumor necrosis factor-alpha downregulates endothelial nitric oxide synthase mRNA stability via translation elongation factor 1-alpha 1. Circ Res 2008; 103(6): 591-7. [http://dx.doi.org/10.1161/CIRCRESAHA.108.173963] [PMID: 18688046] [104] Sansbury BE, Hill BG. Regulation of obesity and insulin resistance by nitric oxide. Free Radic Biol Med 2014; 73: 383-99. [http://dx.doi.org/10.1016/j.freeradbiomed.2014.05.016] [PMID: 24878261] [105] Karantzoulis-Fegaras F, Antoniou H, Lai SLM, et al. Characterization of the human endothelial nitricoxide synthase promoter. J Biol Chem 1999; 274(5): 3076-93. [http://dx.doi.org/10.1074/jbc.274.5.3076] [PMID: 9915847] [106] Srinivasan S, Hatley ME, Bolick DT, et al. Hyperglycaemia-induced superoxide production decreases eNOS expression via AP-1 activation in aortic endothelial cells. Diabetologia 2004; 47(10): 1727-34. [http://dx.doi.org/10.1007/s00125-004-1525-1] [PMID: 15490108] [107] da Costa RM, Silva JF, Alves JV, et al. Increased O-GlcNAcylation of Endothelial Nitric Oxide Synthase Compromises the Anti-contractile Properties of Perivascular Adipose Tissue in Metabolic Syndrome. Front Physiol 2018; 9: 341. [http://dx.doi.org/10.3389/fphys.2018.00341] [PMID: 29681862] [108] Du XL, Edelstein D, Dimmeler S, Ju Q, Sui C, Brownlee M. Hyperglycemia inhibits endothelial nitric oxide synthase activity by posttranslational modification at the Akt site. J Clin Invest 2001; 108(9): 1341-8. [http://dx.doi.org/10.1172/JCI11235] [PMID: 11696579] [109] Kashyap SR, Roman LJ, Lamont J, et al. Insulin resistance is associated with impaired nitric oxide synthase activity in skeletal muscle of type 2 diabetic subjects. J Clin Endocrinol Metab 2005; 90(2): 1100-5. [http://dx.doi.org/10.1210/jc.2004-0745] [PMID: 15562034] [110] Bonini MG, Dull RO, Minshall RD. Caveolin-1 Regulation of Endothelial Nitric Oxide Synthase (eNOS) Function and Oxidative Stress in the Endothelium. In: Laher I, Ed. Systems Biology of Free Radicals and Antioxidants 2014; 1343-63. [http://dx.doi.org/10.1007/978-3-642-30018-9_183] [111] Haddad D, Al Madhoun A, Nizam R, Al-Mulla F. Role of Caveolin-1 in Diabetes and Its Complications. Oxid Med Cell Longev 2020; 2020: 1-20. [http://dx.doi.org/10.1155/2020/9761539] [PMID: 32082483] [112] Butler M, McKay RA, Popoff IJ, et al. Specific inhibition of PTEN expression reverses hyperglycemia

Impaired NO 0etabolism in T2D

The Role of Nitric Oxide in Type 2 Diabetes 63

in diabetic mice. Diabetes 2002; 51(4): 1028-34. [http://dx.doi.org/10.2337/diabetes.51.4.1028] [PMID: 11916922] [113] Yin L, Cai W-J, Chang X-Y, Li J, Zhu L-Y, Su X-H, et al. Analysis of PTEN expression and promoter methylation in Uyghur patients with mild type 2 diabetes mellitus. 2018. [http://dx.doi.org/10.1097/MD.0000000000013513] [114] Crabtree MJ, Smith CL, Lam G, Goligorsky MS, Gross SS. Ratio of 5,6,7,8-tetrahydrobiopterin to 7,8-dihydrobiopterin in endothelial cells determines glucose-elicited changes in NO vs. superoxide production by eNOS. Am J Physiol Heart Circ Physiol 2008; 294(4): H1530-40. [http://dx.doi.org/10.1152/ajpheart.00823.2007] [PMID: 18192221] [115] Wang S, Fang F, Jin WB, Wang X, Zheng DW. Assessment of serum arginase I as a type 2 diabetes mellitus diagnosis biomarker in patients. Exp Ther Med 2014; 8(2): 585-90. [http://dx.doi.org/10.3892/etm.2014.1768] [PMID: 25009624] [116] Kashyap SR, Lara A, Zhang R, Park YM, DeFronzo RA. Insulin reduces plasma arginase activity in type 2 diabetic patients. Diabetes Care 2008; 31(1): 134-9. [http://dx.doi.org/10.2337/dc07-1198] [PMID: 17928367] [117] Shatanawi A, Momani MS. Plasma arginase activity is elevated in type 2 diabetic patients. 2017. [118] Romero MJ, Platt DH, Tawfik HE, et al. Diabetes-induced coronary vascular dysfunction involves increased arginase activity. Circ Res 2008; 102(1): 95-102. [http://dx.doi.org/10.1161/CIRCRESAHA.107.155028] [PMID: 17967788] [119] Abbasi F, Asagmi T, Cooke JP, et al. Plasma concentrations of asymmetric dimethylarginine are increased in patients with type 2 diabetes mellitus. Am J Cardiol 2001; 88(10): 1201-3. [http://dx.doi.org/10.1016/S0002-9149(01)02063-X] [PMID: 11703973] [120] Lu TM, Lin SJ, Lin MW, Hsu CP, Chung MY. The association of dimethylarginine dimethylaminohydrolase 1 gene polymorphism with type 2 diabetes: a cohort study. Cardiovasc Diabetol 2011; 10(1): 16. [http://dx.doi.org/10.1186/1475-2840-10-16] [PMID: 21303562] [121] Antoniades C, Shirodaria C, Leeson P, et al. Association of plasma asymmetrical dimethylarginine (ADMA) with elevated vascular superoxide production and endothelial nitric oxide synthase uncoupling: implications for endothelial function in human atherosclerosis. Eur Heart J 2009; 30(9): 1142-50. [http://dx.doi.org/10.1093/eurheartj/ehp061] [PMID: 19297385] [122] Xuan C, Chang FJ, Liu XC, et al. Endothelial nitric oxide synthase enhancer for protection of endothelial function from asymmetric dimethylarginine–induced injury in human internal thoracic artery. J Thorac Cardiovasc Surg 2012; 144(3): 697-703. [http://dx.doi.org/10.1016/j.jtcvs.2012.01.020] [PMID: 22336756] [123] Omodeo-Salè F, Cortelezzi L, Vommaro Z, Scaccabarozzi D, Dondorp AM. Dysregulation of L arginine metabolism and bioavailability associated to free plasma heme. Am J Physiol Cell Physiol 2010; 299(1): C148-54. [http://dx.doi.org/10.1152/ajpcell.00405.2009] [PMID: 20357184] [124] Ramírez-Zamora S, Méndez-Rodríguez ML, Olguín-Martínez M, et al. Increased erythrocytes byproducts of arginine catabolism are associated with hyperglycemia and could be involved in the pathogenesis of type 2 diabetes mellitus. PLoS One 2013; 8(6): e66823. [http://dx.doi.org/10.1371/journal.pone.0066823] [PMID: 23826148] [125] Mahdi A, Tengbom J, Alvarsson M, Wernly B, Zhou Z, Pernow J. Red Blood Cell Peroxynitrite Causes Endothelial Dysfunction in Type 2 Diabetes Mellitus via Arginase. Cells 2020; 9(7): 1712. [http://dx.doi.org/10.3390/cells9071712] [PMID: 32708826] [126] Raza H, Prabu SK, John A, Avadhani NG. Impaired mitochondrial respiratory functions and oxidative stress in streptozotocin-induced diabetic rats. Int J Mol Sci 2011; 12(5): 3133-47.

64 The Role of Nitric Oxide in Type 2 Diabetes

Bahadoran et al.

[http://dx.doi.org/10.3390/ijms12053133] [PMID: 21686174] [127] Shenouda SM, Widlansky ME, Chen K, et al. Altered mitochondrial dynamics contributes to endothelial dysfunction in diabetes mellitus. Circulation 2011; 124(4): 444-53. [http://dx.doi.org/10.1161/CIRCULATIONAHA.110.014506] [PMID: 21747057] [128] Elfering SL, Sarkela TM, Giulivi C. Biochemistry of mitochondrial nitric-oxide synthase. J Biol Chem 2002; 277(41): 38079-86. [http://dx.doi.org/10.1074/jbc.M205256200] [PMID: 12154090] [129] Brodsky SV, Gao S, Li H, Goligorsky MS. Hyperglycemic switch from mitochondrial nitric oxide to superoxide production in endothelial cells. Am J Physiol Heart Circ Physiol 2002; 283(5): H2130-9. [http://dx.doi.org/10.1152/ajpheart.00196.2002] [PMID: 12384491] [130] Haynes V, Elfering SL, Squires RJ, et al. Mitochondrial nitric-oxide synthase: role in pathophysiology. IUBMB Life 2003; 55(10-11): 599-603. [PMID: 14711005] [131] Litvinova L, Atochin DN, Fattakhov N, Vasilenko M, Zatolokin P, Kirienkova E. Nitric oxide and mitochondria in metabolic syndrome. Front Physiol 2015; 6(20): 20. [http://dx.doi.org/10.3389/fphys.2015.00020] [PMID: 25741283] [132] Finocchietto P, Barreyro F, Holod S, et al. Control of muscle mitochondria by insulin entails activation of Akt2-mtNOS pathway: implications for the metabolic syndrome. PLoS One 2008; 3(3): e1749. [http://dx.doi.org/10.1371/journal.pone.0001749] [PMID: 18335029] [133] Blasco-Baque V, Garidou L, Pomié C, et al. Periodontitis induced by Porphyromonas gingivalis drives periodontal microbiota dysbiosis and insulin resistance via an impaired adaptive immune response. Gut 2017; 66(5): 872-85. [http://dx.doi.org/10.1136/gutjnl-2015-309897] [PMID: 26838600] [134] Blasco-Baque V, Kémoun P, Loubieres P, et al. [Impact of periodontal disease on arterial pressure in diabetic mice]. Ann Cardiol Angeiol (Paris) 2012; 61(3): 173-7. [http://dx.doi.org/10.1016/j.ancard.2012.04.012] [PMID: 22621847] [135] Sun X, Li M, Xia L, et al. Alteration of salivary microbiome in periodontitis with or without type-2 diabetes mellitus and metformin treatment. Sci Rep 2020; 10(1): 15363. [http://dx.doi.org/10.1038/s41598-020-72035-1] [PMID: 32958790] [136] McLennan S, Yue DK, Fisher E, et al. Deficiency of ascorbic acid in experimental diabetes. Relationship with collagen and polyol pathway abnormalities. Diabetes 1988; 37(3): 359-61. [http://dx.doi.org/10.2337/diab.37.3.359] [PMID: 2836250] [137] Wilson R, Willis J, Gearry R, et al. Inadequate Vitamin C Status in Prediabetes and Type 2 Diabetes Mellitus: Associations with Glycaemic Control, Obesity, and Smoking. Nutrients 2017; 9(9): 997. [http://dx.doi.org/10.3390/nu9090997] [PMID: 28891932] [138] Christie-David DJ, Gunton JE. Vitamin C deficiency and diabetes mellitus - easily missed? Diabet Med 2017; 34(2): 294-6. [http://dx.doi.org/10.1111/dme.13287] [PMID: 27859562] [139] Lundberg JO, Weitzberg E, Cole JA, Benjamin N. Nitrate, bacteria and human health. Nat Rev Microbiol 2004; 2(7): 593-602. [http://dx.doi.org/10.1038/nrmicro929] [PMID: 15197394] [140] Govoni M, Jansson EA, Weitzberg E, Lundberg JO. The increase in plasma nitrite after a dietary nitrate load is markedly attenuated by an antibacterial mouthwash. 2008. [http://dx.doi.org/10.1016/j.niox.2008.08.003] [141] Zhang Y, Zhang H. Microbiota associated with type 2 diabetes and its related complications. Food Sci Hum Wellness 2013; 2(3-4): 167-72. [http://dx.doi.org/10.1016/j.fshw.2013.09.002]

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[142] Goh CE, Trinh P, Colombo PC, et al. Association Between Nitrate-Reducing Oral Bacteria and Cardiometabolic Outcomes: Results From ORIGINS. J Am Heart Assoc 2019; 8(23): e013324. [http://dx.doi.org/10.1161/JAHA.119.013324] [PMID: 31766976] [143] Bahadoran Z, Mirmiran P, Kashfi K, Ghasemi A. Lost-in-Translation of Metabolic Effects of Inorganic Nitrate in Type 2 Diabetes: Is Ascorbic Acid the Answer? Int J Mol Sci 2021; 22(9): 4735. [http://dx.doi.org/10.3390/ijms22094735] [PMID: 33947005] [144] Rassaf T, Bryan NS, Kelm M, Feelisch M. Concomitant presence of N-nitroso and S-nitroso proteins in human plasma. Free Radic Biol Med 2002; 33(11): 1590-6. [http://dx.doi.org/10.1016/S0891-5849(02)01183-8] [PMID: 12446216] [145] Rassaf T, Preik M, Kleinbongard P, et al. Evidence for in vivo transport of bioactive nitric oxide in human plasma. J Clin Invest 2002; 109(9): 1241-8. [http://dx.doi.org/10.1172/JCI0214995] [PMID: 11994413] [146] Rassaf T, Kleinbongard P, Preik M, et al. Plasma nitrosothiols contribute to the systemic vasodilator effects of intravenously applied NO: experimental and clinical Study on the fate of NO in human blood. Circ Res 2002; 91(6): 470-7. [http://dx.doi.org/10.1161/01.RES.0000035038.41739.CB] [PMID: 12242264] [147] Rassaf T, Feelisch M, Kelm M. Circulating no pool: assessment of nitrite and nitroso species in blood and tissues. Free Radic Biol Med 2004; 36(4): 413-22. [http://dx.doi.org/10.1016/j.freeradbiomed.2003.11.011] [PMID: 14975444] [148] Doctor A, Spinella P. Effect of processing and storage on red blood cell function in vivo. Semin Perinatol 2012; 36(4): 248-59. [http://dx.doi.org/10.1053/j.semperi.2012.04.005] [PMID: 22818545] [149] McMahon TJ, Doctor A. Extrapulmonary effects of inhaled nitric oxide: role of reversible Snitrosylation of erythrocytic hemoglobin. Proc Am Thorac Soc 2006; 3(2): 153-60. [http://dx.doi.org/10.1513/pats.200507-066BG] [PMID: 16565424] [150] James PE, Lang D, Tufnell-Barret T, Milsom AB, Frenneaux MP. Vasorelaxation by red blood cells and impairment in diabetes: reduced nitric oxide and oxygen delivery by glycated hemoglobin. Circ Res 2004; 94(7): 976-83. [http://dx.doi.org/10.1161/01.RES.0000122044.21787.01] [PMID: 14963010] [151] Padrón J, Peiró C, Cercas E, Llergo JL, Sánchez-Ferrer CF. Enhancement of S-nitrosylation in glycosylated hemoglobin. Biochem Biophys Res Commun 2000; 271(1): 217-21. [http://dx.doi.org/10.1006/bbrc.2000.2617] [PMID: 10777705] [152] Kim-Shapiro DB, Schechter AN, Gladwin MT. Unraveling the reactions of nitric oxide, nitrite, and hemoglobin in physiology and therapeutics. Arterioscler Thromb Vasc Biol 2006; 26(4): 697-705. [http://dx.doi.org/10.1161/01.ATV.0000204350.44226.9a] [PMID: 16424350] [153] Datta B, Tufnell-Barrett T, Bleasdale RA, et al. Red blood cell nitric oxide as an endocrine vasoregulator: a potential role in congestive heart failure. Circulation 2004; 109(11): 1339-42. [http://dx.doi.org/10.1161/01.CIR.0000124450.07016.1D] [PMID: 15023874] [154] Figueroa XF, Lillo MA, Gaete PS, Riquelme MA, Sáez JC. Diffusion of nitric oxide across cell membranes of the vascular wall requires specific connexin-based channels. Neuropharmacology 2013; 75: 471-8. [http://dx.doi.org/10.1016/j.neuropharm.2013.02.022] [PMID: 23499665] [155] Wright JA, Richards T, Becker DL. Connexins and Diabetes. Cardiol Res Pract 2012; 2012: 1-8. [http://dx.doi.org/10.1155/2012/496904] [PMID: 22536530] [156] Looft-Wilson RC, Billaud M, Johnstone SR, Straub AC, Isakson BE. Interaction between nitric oxide signaling and gap junctions: Effects on vascular function. Biochim Biophys Acta Biomembr 2012; 1818(8): 1895-902. [http://dx.doi.org/10.1016/j.bbamem.2011.07.031] [PMID: 21835160]

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[157] Yazir Y, Polat S, Utkan T, Aricioglu F. Role of the nitric oxide-soluble guanylyl cyclase pathway in cognitive deficits in streptozotocin-induced diabetic rats. Psychiatry and Clinical Psychopharmacology 2019; 29(1): 34-44. [http://dx.doi.org/10.1080/24750573.2018.1471883] [158] Young ME, Leighton B. Young ME, Leighton B. Evidence for altered sensitivity of the nitric oxide/cGMP signalling cascade in insulin-resistant skeletal muscle. The Biochemical journal 1998; 329((Pt 1)(Pt 1)): 73-9.

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CHAPTER 4

Asymmetrical Dimethyl Arginine, Nitric Oxide, and Type 2 Diabetes Zahra Bahadoran1, Mattias Carlström2, Parvin Mirmiran3 and Asghar Ghasemi4,* Nutrition and Endocrine Research Center, Research Institute for Endocrine Sciences, Shahid Beheshti University of Medical Sciences, Tehran, Iran 2 Department of Physiology and Pharmacology, Karolinska Institute, Stockholm, Sweden 3 Department of Clinical Nutrition and Human Dietetics, Faculty of Nutrition Sciences and Food Technology, National Nutrition and Food Technology Research Institute, Shahid Beheshti University of Medical Sciences, Tehran, Iran 4 Endocrine Physiology Research Center, Research Institute for Endocrine Sciences, Shahid Beheshti University of Medical Sciences, Tehran, Iran 1

Abstract: Asymmetric dimethylarginine (ADMA), an endogenous competitive inhibitor of nitric oxide (NO) synthase (NOS) isoenzymes, can substantially inhibit vascular NO production at concentrations that are observed in pathophysiological conditions. Over-production of ADMA (via overexpression and/or activity of class 1 of the protein arginine methyltransferases, PRMT-1) alongside decreased catabolism (due to decreased expression and/or activity of dimethylarginine dimethyloaminohydrolase, DDAH) in type 2 diabetes (T2D) and insulin resistance results in increased circulatory and intracellular ADMA levels. Such pathological elevated ADMA levels lead to a decreased NO bioavailability and the development of diabetes complications, including cardiovascular diseases, nephropathy, and retinopathy; elevated ADMA levels also increase the mortality risk in these patients. Here, we discuss current documents indicating how disrupted ADMA metabolism contributes to the development of T2D and its complications. The role of other endogenous methylarginines, i.e., NGmonomethyl-L-arginine (L-NMMA) and NG, NG′-dimethyl-L-arginine (SDMA) on NO production and T2D are also discussed.

Keywords: Asymmetric Dimethylarginine, Cationic Amino Acid Transporter, LCitrulline, Dimethylarginine, Dimethylaminohydrolase, Endothelial Nitric Oxide Synthase, L-Arginine, Nitric Oxide, NG-Monomethyl-L-Arginine, NG, NG′-Dimethyl-L-Arginine, Protein Arginine Methyltransferases, Type 2 Diabetes. Corresponding author Asghar Ghasemi: Endocrine Physiology Research Center, Research Institute for Endocrine Sciences, Shahid Beheshti University of Medical Sciences, Tehran, Iran; No. 24, Erabi Street, Velenjak, Tehran, Iran; Phone: +98 21 22409309; Fax: +98 21 22416264, Email: [email protected]

*

Asghar Ghasemi, Khosrow Kashfi, Zahra Bahadoran (Eds.) All rights reserved-© 2022 Bentham Science Publishers

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INTRODUCTION Asymmetric dimethylarginine (NG, NG-dimethyl-L-arginine, ADMA), a naturally occurring amino acid, is synthesized upon hydrolysis of methylated cellular proteins and circulates within the plasma [1, 2]. ADMA and other methylarginines were isolated from human urine in 1970 by Kakimoto et al. [3]. ADMA is an endogenous inhibitor of nitric oxide (NO) synthase (NOS) isoenzymes [1, 2]. The first report introducing ADMA as an endogenous inhibitor of NOS goes back to 1992, when Vallance et al. described that accumulation of intracellular ADMA decreases NO availability and contributes to the development of hypertension and renal dysfunction [4]. Beyond inhibition of NOS activity, ADMA may reduce NOS expression and cause uncoupling of NOS in endothelial cells leading to increased superoxide generation and subsequent oxidative stress [5, 6]. In healthy humans, the mean plasma level of ADMA is ~0.5-0.7 μM [7, 8], with a range of 0.22 to 0.79 μM [9]. Several human studies reported increased plasma ADMA levels in pathologic conditions, including hypertension, kidney diseases, hypercholesterolemia, atherosclerosis, type 2 diabetes (T2D), and chronic heart failure [10 - 13]. ADMA has also received more clinical attention since its elevated level is an independent risk factor for cardiometabolic diseases [14, 15]. Elevated ADMA level is an independent predictor of cardiovascular disease [relative risk (RR)=1.42, 95% CI=1.29-1.56], coronary heart disease (RR=1.39, 95% CI=1.19-1.62), stroke (RR=1.60, 95% CI=1.33-1.91) [15], and all-cause mortality (RR=1.31, 95% CI=1.13-1.53) [16]. Here, we summarize ADMA metabolism and the importance of the ADMAdimethylarginine dimethylaminohydrolase (DDAH) pathway on whole-body NO synthesis and bioavailability. Then we discuss current reports regarding how the disrupted ADMA-DDAH pathway can contribute to the development of T2D and its complications. We also focused on the potential role of other endogenous methylarginines, i.e., NG-monomethyl-L-arginine (L-NMMA) and NG, NG′-dimethyl-L-arginine or symmetric dimethylarginine (SDMA) on NO production and development of T2D and its complications. ADMA BIOSYNTHESIS AND METABOLISM ADMA is released upon hydrolysis of post-translationally methylated intracellular proteins by protein arginine methyltransferases (PRMTs). Methylation of Larginine (Arg) residues in cellular proteins is a post-translational modification, transferring 1 or 2 methyl groups to the guanidine nitrogens of Arg [1, 2, 17]. In mammals, two PRMT isoenzymes are identified, type I (PRMT 1, 3, 4, 6, and 8) and type II (PRMT 5, 7, and F-box only protein 11, FBXO11) [18]. The PRMT type I is responsible for about 85% of total protein Arg methylation activity [19].

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Each day about 300 µmol ADMA is constitutively synthesized during the turnover of methylated Arg residues in proteins [1, 20]. About 80-90% of ADMA is metabolized by the dimethylarginine dimethylaminohydrolase (DDAH) into Lcitrulline (Cit) and dimethylamine, and a small part (10-20%) is metabolized by aminotransferase and excreted by the kidneys [1, 2, 21]. About 250 μmol of ADMA is daily degraded by DDAH [22], and urinary excretion of ADMA over a 24-h period is estimated to be 13.5±3.1 mg (~65 µmol per 24-h) in healthy adults [4]. In humans, red blood cells (RBCs) play a critical role in the synthesis and storage of ADMA; there is fast bidirectional traffic of ADMA across the plasma membrane of the RBCs that leads to equilibrium between intra- and extracellular ADMA [23]. In humans, two isoforms of DDAH are found: DDAH-1 and DDAH-2; DDAH-1 is the predominant form in the liver and kidney tubules [24] as well as in the brain at sites of neural NOS (nNOS) expression [25]. About 70% of ADMA is metabolized in the kidney and liver via DDAH-1 [26]. DDAH-1 activity in the kidney and liver is responsible for the metabolism of excessive circulating ADMA [27]. Although DDAH-1 regulates the degradation of ADMA in neuronal tissues, recent data indicate that it is the major isomer regulating systemic ADMA and cardiovascular NO bioavailability [28, 29]. DDAH-2 predominates in tissues expressing endothelial NOS (eNOS) (e.g., heart, vascular endothelium, and smooth muscle cells) and inducible NOS (iNOS) (e.g., immune tissues) [24, 30, 31]. DDAH-2 is a major player in regulating ADMA levels in the heart and vessels [28, 29]. The Km values of DDAH-1 and DDAH-2 for ADMA are higher than their intracellular concentrations [31]. Km value of DDAH-1 for ADMA is 170 μM in humans, and Kcat is 1.66 μmol/L/min [32]. Km value of DDAH-2 for ADMA is 16 μM and Vmax value is 4.8 nmol/mg/min [33]. The apparent rate of ADMA metabolism for DDAH-2 is ~70 times less than that of DDAH-1 [33]. Fig. (1) summarizes ADMA biosynthesis and metabolism. A wide distribution of two DDAH isoforms in various tissues indicates that the regulation of methylarginines level has critical biological importance [31]. Both intra- and extracellular levels of ADMA may be substantially elevated upon increased protein methylation or proteolysis, decreased DDAH activity, or decreased cationic amino acid transporter (CAT) activity [34]. DDAHs’ expression and activity also contribute to the pathogenesis of endothelial dysfunction [10]. DDAH-2 critically determines NO availability in endothelial cells [33], and its gene silencing reduces endothelial-dependent relaxation by 40% [35]. Regulation of plasma ADMA level is highly dependent on factors that affect the expression and activity of DDAH

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[36]; i.e., hyperglycemia, oxidative stress, and angiotensin II can inhibit the DDAH expression and/or activity [37 - 39].

Fig. (1). An overview of asymmetric dimethylarginine (ADMA) biosynthesis and metabolism. Methylation of L-arginine residues within cellular proteins occurs via protein arginine methyltransferases (PRMTs) (PRMT-I and PRMT-II). The methylation process of L-arginine residues is supported by Sadenosylmethionine (SAM) as a methyl donor. Proteolytic breakdown of the proteins leads to the generation of ADMA. A minor fraction of endogenously synthesized ADMA is eliminated by urinary excretion (1020%); ADMA is mainly metabolized by the enzymes dimethylarginine dimethylaminohydrolase (DDAH) (DDAH-I and DDAH-II) to L-citrulline and dimethylamine (80-90%). SAH, S-adenosylhomocysteine. Created with Biorender.com.

Arg is another important regulator of DDAH activity and intracellular levels of ADMA [34]; Arg is a competitive inhibitor of DDAH with a relatively high inhibitory constant (Ki = 2.5 mM) [40]. Arg (0-400 µM) dose-dependently inhibits ADMA metabolism (at either physiological or pathological intracellular concentrations of ADMA) and increases its intracellular levels [40]. The cellular performance of Arg methylation is not clear; however, it seems to contribute to the regulation of RNA processing, transport, and stability as well as regulation of the transcription process, DNA repair, protein localization, proteinprotein interactions, signal transduction, and recycling or desensitization of receptors [18, 41 - 43]. In mice, about 1.4% of protein-incorporated Arg residues

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in the lung and 0.3-0.6% in the other tissues are ADMA; ADMA residues in protein hydrolysates of the lung, heart, kidney, and liver were determined as 4.23±2.19, 1.11±0.53, 1.41±0.26 and 1.05±0.42 nmol/mg protein [44]. Adma and Regulation of No Synthesis ADMA competes with Arg for all isoforms of NOS, including eNOS, nNOS, and iNOS [17]. Although intracellular Arg concentrations exceed the Km of eNOS for Arg, high-normal levels of ADMA are enough to decrease eNOS activity via competition with Arg [10]. Both intracellular and extracellular availability of ADMA affects its mediatory role in NO synthesis [27]. Fig. (2) shows how ADMA can inhibit NO synthesis.

Fig. (2). Effects of increased intracellular concentrations of asymmetric dimethylarginine (ADMA) on nitric oxide (NO) biosynthesis. ADMA can inhibit NO production by decreasing endothelial NO synthase (eNOS) expression and decreasing the affinity of eNOS for L-arginine (L-arg); ADMA-bound eNOS is uncoupled and generates superoxide anion rather than NO. Beyond its inhibitory effect on eNOS activity, ADMA competes with arginine for transport into cells. DDAH, dimethylarginine dimethylaminohydrolase; PRMTs, protein arginine methyltransferases; L-Cit, L-citrulline; SDMA, NG, NG′-dimethyl-L-arginine. Created with Biorender.com.

Cellular Uptake of ADMA Due to its active transport into the cells via the CAT family, cellular levels of ADMA can reach up to 5-20-fold of plasma level, a range that can tonically inhibit NOSs [34]. ADMA has a higher affinity than Arg for both CAT-1 and CAT-2 transporters and a similar affinity as Arg for other CAT isoforms, e.g.,

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CAT-2B [21]. In one study, the potential capacity of endothelial cells to uptake and accumulate ADMA, in either the absence or presence of extracellular Arg, was assessed. Baseline cellular concentrations of Arg and ADMA were 215 and 2.7 µM, and following a 20-min incubation of the cells with 10 µM, intracellular ADMA levels increased to 68.4 µM [44]. The ADMA uptake was dosedependent; at the concentration of 0.5 µM, intracellular ADMA concentration reached up to 4.4 µM, and increased exposure to ADMA by 20-fold increased its intracellular concentration by 15-fold [44]. The presence of Arg reduced cellular uptake of ADMA by 2.9-fold (from 68.4 to 23.5 µM when the cells were incubated with 10 µM ADMA) [44]. Since the CAT family transporter system is upregulated by pro-inflammatory cytokines, including tumor necrosis factor-α (TNF-α) and interleukin1-β (IL-1β) [45], intracellular ADMA concentrations may be increased in inflammatory conditions. The concentration of free cellular ADMA in the lung, heart, kidney, and liver was determined as 10, 14, 181, and 88 µmol/mg protein [44]. The intracellular concentration of ADMA was about 3.6 μM in the bovine aortic endothelial cells (BAECs) [46]. Such physiological concentrations of ADMA exert a modest effect (~10%) on endothelial NO production; however, higher cellular concentrations to 3-9-fold, substantially (~30-70%) inhibit eNOS-derived NO [46]. Caveolar co-localization of CAT-1 and eNOS in the endothelial cells seems to facilitate selective accessibility of circulating ADMA to the NOS enzyme, so it is reasonable to speculate that NOS inhibition may be more dependent on plasma ADMA concentration than intracellular ADMA sources [34, 47]. Inhibitory Effects of ADMA on NOS Expression and Activity Although competitive inhibitory effects of ADMA on NOS enzyme activity are well documented, there is controversy regarding the apparent Ki values and the magnitude of the inhibition. Km values of eNOS (i.e., half-saturating Arg concentrations) ranging from 2 to 4 µM and its Vmax ranging from 0.065 to 0.14 µmol/mg/min [44, 48, 49]. Km values of eNOS in the presence of ADMA increased from 5.32 to 31.25 μM [50]. The Ki value of ADMA for eNOS activity was 0.9 μM [46]. The Ki value of ADMA for nNOS has been usually determined below 1 μM [34, 51]). Incubation of human left internal thoracic artery rings (obtained from patients undergoing coronary artery bypass grafting) with ADMA (at a concentration of 100 µM) prevented acetylcholine-induced relaxation by 64% (12.7% vs. 35.3% in the presence of ADMA compared to control) [6]; ADMA also reduced eNOS expression level by 85% (from 0.36 to 0.05) and increased superoxide anion

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production by 83% (from 0.51 to 2.97 relative light unit (RLU) per second per mg dry weight) [6]. In an experiment, purified human eNOS was incubated with a wide range of ADMA (0-500 μM) in the presence of 100 μM Arg, and NO formation was measured over a 30 min period; ADMA dose-dependently inhibited NO production with 19% and 86% inhibition at concentrations of 10 and 500 μM ADMA [46]. ADMA at the concentration of 25 μM reduced eNOS enzyme activity by 76%; NMMA at a concentration of 10 μM inhibited NO production by 23%; this inhibitory effect was dose-dependent and complete inhibition of nNOS occurred at the concentration of 100 μM L-NMMA in the presence of highconcentration of Arg (100 μM) [51]. ADMA and T2D The underlying mechanisms explaining the association between ADMA and diabetes or insulin resistance have not been well documented; however, available evidence indicates that elevated ADMA levels may be both a consequence or a cause of insulin resistance [52]. Considering hormonal actions of NO in glucose and insulin homeostasis [53, 54] and the central role of NO-disrupted pathway in the pathophysiology of dysglycemia and insulin resistance [55, 56], elevated ADMA may be considered a potential risk factor for T2D. It has been speculated that the co-existence of insulin resistance and endothelial dysfunction is partially related to elevated plasma or tissue ADMA [57]. In the following sections, we summarize the evidence supporting the association between disrupted ADMADDAH pathway and T2D and present plasma and tissue concentrations of ADMA in diabetic patients. DDAH and T2D: Lessons from Genetic Studies Genetically-modified experimental models (either knockout or overexpressed DDAH models) provide evidence that the ADMA-DDAH pathway has a critical role in regulating glucose and insulin homeostasis. In cultured endothelial cells, overexpression of DDAH induced more than a 2-fold increase in NOS activity and NO production [58]. Overexpression of DDAH-1 reduced insulin resistance index by 50%, enhanced insulin sensitivity, and increased Akt phosphorylation in the liver after intraperitoneal glucose challenge [57]. Moreover, DDAH-1 overexpressing mice showed blunted glucose-induced increased ADMA levels in response to glucose challenge [57]. In the DDAH-1 transgenic mice (overexpressed human DDAH-1), with a 3-fold higher DDAH activity compared to wild-type mice (0.9 vs. 0.3 µmol/µg protein/min), ADMA levels significantly decreased by 2-fold while urinary excretion of NO metabolites increased by 2-

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fold [58]; skeletal muscle and cardiac NOS activity in this model increased by 100% and 70%, respectively [58]. Although extrapolation of these animal-based findings to humans may be difficult due to the lack of evidence on DDAH gene deficiency in humans, studies of DDAH gene polymorphisms strongly support the causal relationship between disrupted ADMA-DDAH pathway and insulin resistance and T2D. Polymorphisms of DDAH-1 (i.e., rs669173, rs7521189, rs2474123, and rs13373844) and DDAH-2 (i.e., rs3131383 and the TGCCCAGGAG haplotype) genes are strongly associated with high serum ADMA concentrations and development of T2D [59]. In a cohort study, among six single nucleotide polymorphisms (SNPs) in DDAH1 (i.e., rs233112, rs1498373, rs1498374, rs587843, rs1403956, and rs1241321), the rs1241321 was associated with developing T2D [60]; carrying allele A versus G decreased risk of T2D by 25% (OR=0.75, 95% CI=0.60-0.93) and AA versus GG+AG genotype was related to a 36% reduced risk of T2D (OR=0.64, 95% CI=0.47-0.87) [60]. In non-diabetic subjects, fasting plasma glucose and homeostatic model assessment of insulin resistance (HOMA-IR) were significantly lower in subjects with AA genotype in the SNP rs1241321 [60]. Among the six SNPs, s233112, rs1498374, rs1498373, and rs1403956 were related to plasma ADMA levels [60]. Furthermore, a significant difference in the distribution of haplotype frequencies of the DDAH1 gene was observed between diabetic and healthy subjects; the haplotype GGCAGC was associated with a decreased risk of T2D (OR=0.67, 95% CI=0.46-0.98); the haplotypes GATAAG and GGTGGC were associated with higher plasma ADMA levels [60]. Compared with AG-GG individuals, patients with an AA genotype at rs1241321 were more insulin-sensitive and had a better long-term clinical outcome during a 28-month follow-up [60]. A functional DDAH-1 promoter polymorphism, i.e., 396 4N deletion-insertion polymorphism (-396 395insGCGT; Del/Del, Del/Ins, Ins/Ins genotypes), has been shown to reduce the expression of DDAH-1 gene due to disrupted metal regulatory transcription factor-1 binding to the promoter region. This polymorphism is related to elevated plasma ADMA levels and increased risk of T2D (OR=1.38, 95% CI=1.13-1.69); among the subjects who carried Ins/Ins alleles, HOMA-IR was significantly higher compared to those who carried Del/Del and Del/Ins [61]. Plasma and Tissue Concentrations of ADMA in T2D Serum ADMA concentrations have been reported to be increased in insulin resistance [62], T2D [63, 64] and its complications, including retinopathy [65,

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66], cardiovascular morbidity [67] and mortality [68, 69], and nephropathy [70]. Plasma ADMA concentration was 2-fold higher in untreated type 2 diabetic patients than in matched healthy controls (1.59±0.22 vs. 0.69±0.04 µM) [63]. The Arg-to-ADMA ratio, used as an index of Arg bioavailability, was significantly lower in patients with T2D compared to healthy adults (196±67 vs. 225±86 µM); the Arg-to-ADMA ratio was negatively associated with T2D (for each 10 unit increased ratio, OR=0.95, 95% CI=0.93-0.97) and was negatively correlated with the insulin resistance index in non-diabetic subjects [60]. In nondiabetic subjects, plasma ADMA concentrations were also positively associated with impaired insulin-mediated glucose disposal (r=0.73; P=0.001) [62]. Compared to insulinsensitive subjects, ADMA levels were significantly higher in normotensive subjects with insulin resistance and hypertensive insulin-resistant individuals (1.34±0.33 and 1.52±0.29 vs. 0.70±0.18 µM) [62]. Plasma ADMA in diabetic patients is also related to HOMA-IR and high-sensitive C reactive protein (hsCRP) levels [64]. Having diabetic complications is reported to be related to an elevated circulating ADMA; diabetic patients with clinical evidence of macrovascular atherosclerosis (i.e., stroke, myocardial infarction, coronary heart disease, or peripheral arterial occlusive disease) had higher ADMA levels compared to those without macrovascular complications (mean=0.63, 95% CI=0.54–0.74 vs. mean=0.55 95% CI=0.48–0.62) [69]. Compared to healthy subjects (0.45±0.05 µM), plasma levels of ADMA were higher in patients with T2D with and without retinopathy (0.60±0.06 µM and 0.51±0.06 µM [65]. ADMA concentrations in diabetic patients with non-proliferative diabetic retinopathy and proliferative diabetic retinopathy compared with patients without retinopathy were 0.86±0.37 and 0.82±0.31 µM vs. 0.93±0.42 µM, respectively [66]. Circulating ADMA levels in diabetic patients is significantly related to glomerular filtration rate (GFR); i.e., plasma ADMA levels were negatively correlated with estimated GFR (eGFR) (r=-0.21, P 6.5% (HR=3.0, 95% CI=1.2-7.7 in the third compared to the first tertile; HR per increase of 1 SD=1.38, 95% CI=1.0-1.9) [67]. The plasma level of ADMA was reported as an independent predictor of diabetic retinopathy (OR 1.77, 95% CI=1.44–2.17) [65]. Elevated plasma ADMA levels significantly increased chance of having macrovascular disease by 63% (OR=1.63, 95% CI=1.21-2.19) per 0.1 µM [69]. Follow-up of diabetic patients for 5 years showed that a higher ADMA level than the median value (>0.46 µM) increased the incidence of nephropathy [hazard ratio (HR)=2.72, 95% CI=1.255.95] [70]; each 1 µM elevation of plasma ADMA concentration increased the risk of nephropathy by 30% (HR=1.30, 95% CI=1.04–1.63) [70]. In the patients with microalbuminuria, a higher ADMA level than 0.51 µM increased the progression of nephropathy by 7.5-fold (HR=7.57, 95% CI 1.42–40.38) [70]. High ADMA levels were also related to features of cardiovascular diseases (CVD) (i.e., myocardial infarction, percutaneous coronary intervention, coronary artery bypass graft, stroke, carotid revascularization, and all-cause mortality) in patients with T2D; after a median follow-up of 21 months, patients with higher plasma ADMA concentrations (>0.63 compared to ≤0.53 µM) had a higher risk of CVD events (HR=2.37, 95% CI=1.05-5.35) [71]. Elevated plasma ADMA levels predict the risk of CVD events following 5.7 years, independent of traditional CVD risk factors; higher ADMA (>0.49 vs. ≤0.45 µM) was related to increased risk of CVD (HR=2.3, 95% CI= 1.1-4.8) and per each 1 SD (0.09 µM) elevated ADMA level, the risk increased by 30% (HR=1.30, 95% CI=1.01-1.68) [67]. The predictive role of elevated-ADMA for CVD events was stronger in poor-glycemic (HbA1C>6.5%) controlled patients (HR=3.0, 95% CI=1.2-7.7) [67]. ADMA level in type 2 diabetic patients is also a strong predictor of all-cause mortality. A 6-year follow-up study of diabetic patients showed that those with higher baseline ADMA levels (≥0.46 µM) had an 80% higher risk of mortality (HR=1.8, 95% CI=1.2-2.7) [72]. To sum up, a disrupted DDAH-ADMA pathway with a decreased DDAH expression/activity and increased ADMA level occurs in patients with T2D. Elevated plasma ADMA concentration can strongly and independently predict diabetes complications. Since glycemic control and status of the renal function

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affect ADMA levels, the prognostic value of ADMA for complications of T2D may differ. Other Methylarginines and T2D Besides ADMA, L-NMMA and SDMA are also released by the hydrolysis of methylated-Arg residues from intracellular proteins [3]. These methylarginine derivates occur at ~20-50% that of ADMA [18]. The mean plasma concentration of L-NMMA and SDMA is about 0.1 and 0.4 µM in humans [44, 73]. The highest circulating levels of SDMA in humans are observed in chronic renal disease, with a median of 2.42 µM (IQR=1.93-2.87 µM) [74]. The circulating level of SDMA is suggested as a good surrogate for kidney function since it is highly correlated with inulin clearance (r=0.85, 95% CI=0.76-0.91) and serum creatinine (r=0.75, 95% CI=0.46-0.89) [75]. ADMA is now considered a marker of renal function and an independent cardiovascular risk factor [76, 77]. Elevated levels of SDMA, were associated with increased risk of all-cause mortality (RR=1.31, 95% CI=1.181.46) and cardiovascular diseases (RR=1.36, 95% CI=1.10-1.68) [77]. Like ADMA, L-NMMA is predominantly metabolized by DDAH-1 and DDAH2; the Km value of DDAH-1 for L-NMMA is 90 μM in humans, and its Kcat is 0.79/min [32]. Unlike ADMA and L-NMMA, SDMA is not removed by DDAH but also is metabolized by the alanine glyoxylate aminotransferase 2 (AGXT2) to α-keto-δ-N, N-dimethylguanidino-valeric acid (DMGV) [3]; SDMA is mainly removed via renal excretion [3]. Among the methylarginines, ADMA is the primary inhibitor of NO biosynthesis in humans, and its plasma concentration is about 2- to 4-fold higher than that of L-NMMA [3, 30]. Although the potential capacity of L-NMMA to inhibit NOS enzymes’ activity was reported to be comparable with that of ADMA [46, 50, 51], its lower circulatory concentrations make L-NMMA clinically a less important NOS inhibitor. In an experiment, purified human eNOS was incubated with a wide range of ADMA (0-500 μM) in the presence of 100 μM Arg, and NO formation was measured over a 30 min period; L-NMMA dose-dependently inhibited NO production with 17% and 90% inhibition at concentrations of 10 and 500 μM [46]. In another experiment, L-NMMA at a concentration of 25 μM reduced eNOS activity by 61.2%; in the presence of L-NMMA, the Km value of eNOS for Arg increased from 5.32 to14.29 μM [50]. L-NMMA at a concentration of 10 μM inhibited NO production by 26%, while almost complete inhibition of nNOS occurred at a concentration of 100 μM L-NMMA even in the presence of highconcentration Arg (100 μM) [51].

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The IC50 for L-NMMA for NOS enzymes ranges from 3.5 to 6.6 μM (IC50 for eNOS=3.5, IC50 for nNOS=4.9, IC50 for iNOS=6.6, in the presence of 30 μM Arg at 37 ◦C) [78]. Ki values of L-NMMA were determined to be 0.50 μM [51] and 1.1 μM [46] for nNOS and eNOS activity, respectively. Like ADMA, L-NMMA is transported into the cells via CATs; BAECs, in the absence of extracellular Arg, can uptake L-NMMA and accumulate it up 7-fold higher than its concentrations outside the cell [44]. Cellular uptake of L-NMMA was inhibited by 90% and 65% in the presence of lysine (1 μM) and Arg (100 μM) [44]. The Km for transport of L-NMMA is about 70 μM, and the Vmax is 2 μmol/mg protein/min in human endothelial cells [79]. Unlike L-NMMA and ADMA, SDMA has been suggested not to be an inhibitor of NOSs [30]; however, recent evidence reports that SDMA inhibits dosedependently NO production in the intact endothelial cells [80]. The inhibitory effect of SDMA on NO production may be due to its inhibitory effect on Arg uptake by the cell; in vitro studies reported that SDMA at a concentration of mM can completely inhibit cellular Arg uptake [81]; however, it is not clear how this mechanism would be physiologically important at its circulating concentrations in vivo. Because of its lower clinical importance than ADMA, limited studies investigated the metabolic changes of L-NMMA and SMDA in T2D and the possible effects of endogenous L-NMMA and SMDA on glucose and insulin homeostasis. L-NMMA and SMDA levels were increased in obese insulin-resistant subjects by 34% and 32%, respectively [82]. Plasma SDMA and L-NMMA were positively associated with 2-h glucose (r=0.32 and 0.41, respectively), postprandial insulin levels (r=0.35 and 0.38, respectively), and were negatively correlated with insulin sensitivity (r=-0.49 and -0.52, respectively) [82]. Administration of L-NMMA (6 mg/kg) significantly reduces leg glucose uptake in both patients with T2D and healthy subjects; a greater reduction was observed in the diabetic group compared with the controls (75±13% vs. 34±14%) [83]. Infusion of L-NMMA (bolus infusion of 3 mg/kg over 5 min, followed by constant intravenous infusion of 1.25 mg/kg over 25 min) significantly decreased functional activity of NO in the renal circulation; renal plasma flow decreased by 10.7, 9.4, and 11.6% in patients with low (5.2-6.4%), medium (6.4-7.3%), and high (7.3-9.7%) HbA1C levels, respectively [84]. Pharmaceutical Interventions for Elevated Adma Currently, no approved drug or pharmacological agent that can lower the pathologic levels of ADMA is available [85]; inhibition of PRMTs or induction of DDAH activity has been suggested as a pharmacologic strategy to reduce ADMA

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indirectly [86]. Recently, a novel long-acting recombinant DDAH (M-DDAH) has been developed to effectively reduce ADMA levels in preclinical models of endothelial dysfunction, hypertension, and ischemia-reperfusion injury, and improve endothelial function, reduce blood pressure and protect from ischemiareperfusion renal injury [85]. Some clinical trials have been conducted to assess the potential efficacy of different pharmaceutical agents and dietary supplements (e.g., dietary fiber [87] and omega-3 fatty acids [88]) aimed to reduce ADMA. Limited and inconsistent data regarding the effects of oral anti-diabetic agents on ADMA levels in diabetic patients is available. Metformin treatment in type 2 diabetic patients decreased plasma ADMA concentrations (from 1.65±0.21 to 1.18±0.13 µM) concurrent with decreased glycemic parameters [89]; the combination of metformin with a sulfonylurea compound resulted in a similar result (decreased ADMA from 1.75±0.13 to 1.19±0.08 µM) [89]. After a 16-week treatment with pioglitazone (mean dose of 16.6±4.6 mg daily) or glimepiride (mean dose of 1.2±0.8 mg daily), pioglitazone significantly decreased ADMA levels (from 0.59 to 0.51 µM) and improved insulin sensitivity (decreased HOMA-IR value from 1.8 to 1.6) [90]. Administration of pioglitazone (30 mg daily) for 12 weeks significantly decreased urinary ADMA (from 1.27±0.5 to 0.97±0.3 µM) and improved endothelium-dependent vasodilation by 91% (from 4.4±3.9 to 8.4±4.1%) [91]. In contrast, pioglitazone therapy (30 mg daily) for 12 weeks had no significant effect on plasma concentrations of ADMA (0.80±0.05 µM after treatment vs. 0.73±0.04 µM at baseline) and NO metabolites (24.8±1.9 µM after treatment vs. 25.8±2.1 µM at baseline) [92]. In patients with insulin resistance, treatment with rosiglitazone, an insulin-sensitizing agent (4 mg per day for 4 weeks and then 4 mg twice daily for 8 weeks), improved insulin sensitivity and reduced mean plasma ADMA concentrations (from 1.50±0.30 to 1.05±0.33 µM, P = 0.001) [62]. Treatment of ob/ob−/− mice with sodium-glucose cotransporter 2 inhibitors (SGLT2), as the first-line anti-diabetes drugs, significantly increased the Arg-to-ADMA ratio; however, it did not affect serum ADMA per se [93]. Available data regarding the effects of anti-diabetic drugs on ADMA metabolism is not conclusive. CONCLUDING REMARKS Decreased NO bioavailability and NO-related complications in T2D are partly attributed to disrupted ADMA metabolism and increased circulatory levels. DDAH gene polymorphism studies and genetically-modified experimental models of DDAH provide evidence supporting a causal relationship between disrupted ADMA-DDAH pathway and insulin resistance and T2D. Elevated ADMA levels in patients with T2D predict future risk of developing diabetes-associated microand macrovascular diseases and cardiovascular mortality. ADMA-DDAH

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pathway has recently received much interest as a potential target for managing insulin resistance, T2D, and its complications. CONFLICT OF INTEREST None Declared. ACKNOWLEDGEMENT None CONSENT OF PUBLICATION None REFERENCES [1]

Fulton MD, Brown T, Zheng YG. The Biological Axis of Protein Arginine Methylation and Asymmetric Dimethylarginine. Int J Mol Sci 2019; 20(13): 3322. [http://dx.doi.org/10.3390/ijms20133322] [PMID: 31284549]

[2]

Leiper JM, Vallance P. The synthesis and metabolism of asymmetric dimethylarginine (ADMA). Eur J Clin Pharmacol 2006; 62(S1): 33-8. [http://dx.doi.org/10.1007/s00228-005-0013-y]

[3]

Kakimoto Y, Akazawa S. Isolation and identification of N-G,N-G- and N-G,N′-G-dimethyl-arginine, N-epsilon-mono-, di-, and trimethyllysine, and glucosylgalactosyl- and galactosyl-delta-hydroxylysine from human urine. J Biol Chem 1970; 245(21): 5751-8. [http://dx.doi.org/10.1016/S0021-9258(18)62716-4] [PMID: 5472370]

[4]

Leone A, Moncada S, Vallance P, Calver A, Collier J. Accumulation of an endogenous inhibitor of nitric oxide synthesis in chronic renal failure. Lancet 1992; 339(8793): 572-5. [http://dx.doi.org/10.1016/0140-6736(92)90865-Z] [PMID: 1347093]

[5]

Antoniades C, Shirodaria C, Leeson P, et al. Association of plasma asymmetrical dimethylarginine (ADMA) with elevated vascular superoxide production and endothelial nitric oxide synthase uncoupling: implications for endothelial function in human atherosclerosis. Eur Heart J 2009; 30(9): 1142-50. [http://dx.doi.org/10.1093/eurheartj/ehp061] [PMID: 19297385]

[6]

Xuan C, Chang FJ, Liu XC, et al. Endothelial nitric oxide synthase enhancer for protection of endothelial function from asymmetric dimethylarginine–induced injury in human internal thoracic artery. J Thorac Cardiovasc Surg 2012; 144(3): 697-703. [http://dx.doi.org/10.1016/j.jtcvs.2012.01.020] [PMID: 22336756]

[7]

Fleszar MG, Wiśniewski J, Krzystek-Korpacka M, et al. Quantitative Analysis of l-Arginine, Dimethylated Arginine Derivatives, l-Citrulline, and Dimethylamine in Human Serum Using Liquid Chromatography–Mass Spectrometric Method. Chromatographia 2018; 81(6): 911-21. [http://dx.doi.org/10.1007/s10337-018-3520-6] [PMID: 29887621]

[8]

Németh B, Ajtay Z, Hejjel L, et al. The issue of plasma asymmetric dimethylarginine reference range – A systematic review and meta-analysis. PLoS One 2017; 12(5): e0177493. [http://dx.doi.org/10.1371/journal.pone.0177493] [PMID: 28494019]

[9]

Deneva-Koycheva T, Vladimirova-Kitova L, Angelova E, Tsvetkova T. Plasma asymmetric dimethylarginine levels in healthy people. Folia Med (Plovdiv) 2011; 53(1): 28-33. [http://dx.doi.org/10.2478/v10153-010-0024-z] [PMID: 21644402]

ADMA and T2D

The Role of Nitric Oxide in Type 2 Diabetes 81

[10]

Böger RH. Asymmetric dimethylarginine, an endogenous inhibitor of nitric oxide synthase, explains the “L-arginine paradox” and acts as a novel cardiovascular risk factor. J Nutr 2004; 134(10) (Suppl.): 2842S-7S. [http://dx.doi.org/10.1093/jn/134.10.2842S] [PMID: 15465797]

[11]

Landim MBP, Filho AC, Chagas ACP. Asymmetric dimethylarginine (ADMA) and endothelial dysfunction: implications for atherogenesis. Clinics (São Paulo) 2009; 64(5): 471-8. [http://dx.doi.org/10.1590/S1807-59322009000500015] [PMID: 19488614]

[12]

Palau V, Riera M, Duran X, et al. Circulating ADAMs are associated with renal and cardiovascular outcomes in chronic kidney disease patients. Nephrol Dial Transplant 2020; 35(9): 1642. [http://dx.doi.org/10.1093/ndt/gfz110] [PMID: 30102333]

[13]

Yokoro M, Minami M, Okada S, et al. Urinary sodium-to-potassium ratio and serum asymmetric dimethylarginine levels in patients with type 2 diabetes. Hypertens Res 2018; 41(11): 913-22. [http://dx.doi.org/10.1038/s41440-018-0098-1] [PMID: 30209284]

[14]

Heunisch F, Chaykovska L, von Einem G, et al. ADMA predicts major adverse renal events in patients with mild renal impairment and/or diabetes mellitus undergoing coronary angiography. Medicine (Baltimore) 2017; 96(6): e6065. [http://dx.doi.org/10.1097/MD.0000000000006065] [PMID: 28178159]

[15]

Willeit P, Freitag DF, Laukkanen JA, Chowdhury S, Gobin R, Mayr M, et al. Asymmetric dimethylarginine and cardiovascular risk: systematic review and meta-analysis of 22 prospective studies. 2015. [http://dx.doi.org/10.1161/JAHA.115.001833]

[16]

Zhou S, Zhu Q, Li X, et al. Asymmetric dimethylarginine and all-cause mortality: a systematic review and meta-analysis. Sci Rep 2017; 7(1): 44692. [http://dx.doi.org/10.1038/srep44692] [PMID: 28294182]

[17]

Vallance P, Leiper J. Cardiovascular biology of the asymmetric dimethylarginine:dimethylarginine dimethylaminohydrolase pathway. Arterioscler Thromb Vasc Biol 2004; 24(6): 1023-30. [http://dx.doi.org/10.1161/01.ATV.0000128897.54893.26] [PMID: 15105281]

[18]

Bedford MT, Clarke SG. Protein arginine methylation in mammals: who, what, and why. Mol Cell 2009; 33(1): 1-13. [http://dx.doi.org/10.1016/j.molcel.2008.12.013] [PMID: 19150423]

[19]

Tang J, Frankel A, Cook RJ, et al. PRMT1 is the predominant type I protein arginine methyltransferase in mammalian cells. J Biol Chem 2000; 275(11): 7723-30. [http://dx.doi.org/10.1074/jbc.275.11.7723] [PMID: 10713084]

[20]

Kielstein JT, Fliser D, Veldink H. Asymmetric dimethylarginine and symmetric dimethylarginine: axis of evil or useful alliance? Semin Dial 2009; 22(4): 346-50. [http://dx.doi.org/10.1111/j.1525-139X.2009.00578.x] [PMID: 19708979]

[21]

Arrigoni F, Ahmetaj B, Leiper J. The biology and therapeutic potential of the DDAH/ADMA pathway. Curr Pharm Des 2010; 16(37): 4089-102. [http://dx.doi.org/10.2174/138161210794519246] [PMID: 21247398]

[22]

Morris SM Jr. Arginine metabolism in vascular biology and disease. Vasc Med 2005; 10(1_suppl) (Suppl. 1): S83-7. [http://dx.doi.org/10.1177/1358836X0501000112] [PMID: 16444873]

[23]

Davids M, van Hell AJ, Visser M, Nijveldt RJ, van Leeuwen PAM, Teerlink T. Role of the human erythrocyte in generation and storage of asymmetric dimethylarginine. Am J Physiol Heart Circ Physiol 2012; 302(8): H1762-70. [http://dx.doi.org/10.1152/ajpheart.01205.2011] [PMID: 22367507]

[24]

Tran CTL, Fox MF, Vallance P, Leiper JM. Chromosomal localization, gene structure, and expression pattern of DDAH1: comparison with DDAH2 and implications for evolutionary origins. Genomics

82 The Role of Nitric Oxide in Type 2 Diabetes

Bahadoran et al.

2000; 68(1): 101-5. [http://dx.doi.org/10.1006/geno.2000.6262] [PMID: 10950934] [25]

Frey D, Braun O, Briand C, Vašák M, Grütter MG. Structure of the mammalian NOS regulator dimethylarginine dimethylaminohydrolase: A basis for the design of specific inhibitors. Structure 2006; 14(5): 901-11. [http://dx.doi.org/10.1016/j.str.2006.03.006] [PMID: 16698551]

[26]

Franceschelli S, Ferrone A, Pesce M, Riccioni G, Speranza L. Biological functional relevance of asymmetric dimethylarginine (ADMA) in cardiovascular disease. Int J Mol Sci 2013; 14(12): 2441221. [http://dx.doi.org/10.3390/ijms141224412] [PMID: 24351825]

[27]

Wilcken DEL, Sim AS, Wang J, Wang XL. Asymmetric dimethylarginine (ADMA) in vascular, renal and hepatic disease and the regulatory role of l-arginine on its metabolism. Mol Genet Metab 2007; 91(4): 309-17. [http://dx.doi.org/10.1016/j.ymgme.2007.04.017] [PMID: 17560156]

[28]

Liu X, Fassett J, Wei Y, Chen Y. Regulation of DDAH1 as a Potential Therapeutic Target for Treating Cardiovascular Diseases. Evid Based Complement Alternat Med 2013; 2013: 1-6. [http://dx.doi.org/10.1155/2013/619207] [PMID: 23878601]

[29]

Hu X, Atzler D, Xu X, et al. Dimethylarginine dimethylaminohydrolase-1 is the critical enzyme for degrading the cardiovascular risk factor asymmetrical dimethylarginine. Arterioscler Thromb Vasc Biol 2011; 31(7): 1540-6. [http://dx.doi.org/10.1161/ATVBAHA.110.222638] [PMID: 21493890]

[30]

Vallance P, Leiper J. Blocking NO synthesis: how, where and why? Nat Rev Drug Discov 2002; 1(12): 939-50. [http://dx.doi.org/10.1038/nrd960] [PMID: 12461516]

[31]

Leiper JM, Maria JSANTA, Chubb A, et al. Identification of two human dimethylarginine dimethylaminohydrolases with distinct tissue distributions and homology with microbial arginine deiminases. Biochem J 1999; 343(1): 209-14. [http://dx.doi.org/10.1042/bj3430209] [PMID: 10493931]

[32]

Hong L, Fast W. Inhibition of human dimethylarginine dimethylaminohydrolase-1 by S-nitrosoL-homocysteine and hydrogen peroxide. Analysis, quantification, and implications for hyperhomocysteinemia. J Biol Chem 2007; 282(48): 34684-92. [http://dx.doi.org/10.1074/jbc.M707231200] [PMID: 17895252]

[33]

Pope AJ, Karuppiah K, Cardounel AJ. Role of the PRMT–DDAH–ADMA axis in the regulation of endothelial nitric oxide production. Pharmacol Res 2009; 60(6): 461-5. [http://dx.doi.org/10.1016/j.phrs.2009.07.016] [PMID: 19682581]

[34]

Teerlink T, Luo Z, Palm F, Wilcox CS. Cellular ADMA: Regulation and action. Pharmacol Res 2009; 60(6): 448-60. [http://dx.doi.org/10.1016/j.phrs.2009.08.002] [PMID: 19682580]

[35]

Palm F, Onozato ML, Luo Z, Wilcox CS. Dimethylarginine dimethylaminohydrolase (DDAH): expression, regulation, and function in the cardiovascular and renal systems. Am J Physiol Heart Circ Physiol 2007; 293(6): H3227-45. [http://dx.doi.org/10.1152/ajpheart.00998.2007] [PMID: 17933965]

[36]

Tain YL, Hsu CN. Toxic Dimethylarginines: Asymmetric Dimethylarginine (ADMA) and Symmetric Dimethylarginine (SDMA). Toxins (Basel) 2017; 9(3): 92. [http://dx.doi.org/10.3390/toxins9030092] [PMID: 28272322]

[37]

Sorrenti V, Mazza F, Campisi A, Vanella L, Volti G, Giacomo C. High glucose-mediated imbalance of nitric oxide synthase and dimethylarginine dimethylaminohydrolase expression in endothelial cells. Curr Neurovasc Res 2006; 3(1): 49-54. [http://dx.doi.org/10.2174/156720206775541778] [PMID: 16472125]

ADMA and T2D

The Role of Nitric Oxide in Type 2 Diabetes 83

[38]

Tain YL, Kao YH, Hsieh CS, et al. Melatonin blocks oxidative stress-induced increased asymmetric dimethylarginine. Free Radic Biol Med 2010; 49(6): 1088-98. [http://dx.doi.org/10.1016/j.freeradbiomed.2010.06.029] [PMID: 20600827]

[39]

Brands MW, Bell TD, Gibson B. Nitric oxide may prevent hypertension early in diabetes by counteracting renal actions of superoxide. Hypertension 2004; 43(1): 57-63. [http://dx.doi.org/10.1161/01.HYP.0000104524.25807.EE] [PMID: 14656952]

[40]

Wang J, Sim AS, Wang XL, Wilcken DEL. L-arginine regulates asymmetric dimethylarginine metabolism by inhibiting dimethylarginine dimethylaminohydrolase activity in hepatic (HepG2) cells. Cell Mol Life Sci 2006; 63(23): 2838-46. [http://dx.doi.org/10.1007/s00018-006-6271-8] [PMID: 17075694]

[41]

Lee DY, Teyssier C, Strahl BD, Stallcup MR. Role of protein methylation in regulation of transcription. Endocr Rev 2005; 26(2): 147-70. [http://dx.doi.org/10.1210/er.2004-0008] [PMID: 15479858]

[42]

Stallcup MR. Role of protein methylation in chromatin remodeling and transcriptional regulation. Oncogene 2001; 20(24): 3014-20. [http://dx.doi.org/10.1038/sj.onc.1204325] [PMID: 11420716]

[43]

Boisvert FM, Côté J, Boulanger MC, Richard S. A proteomic analysis of arginine-methylated protein complexes. Mol Cell Proteomics 2003; 2(12): 1319-30. [http://dx.doi.org/10.1074/mcp.M300088-MCP200] [PMID: 14534352]

[44]

Bulau P, Zakrzewicz D, Kitowska K, et al. Analysis of methylarginine metabolism in the cardiovascular system identifies the lung as a major source of ADMA. Am J Physiol Lung Cell Mol Physiol 2007; 292(1): L18-24. [http://dx.doi.org/10.1152/ajplung.00076.2006] [PMID: 16891395]

[45]

Malandro MS, Kilberg MS. Molecular biology of mammalian amino acid transporters. Annu Rev Biochem 1996; 65(1): 305-36. [http://dx.doi.org/10.1146/annurev.bi.65.070196.001513] [PMID: 8811182]

[46]

Cardounel AJ, Cui H, Samouilov A, et al. Evidence for the pathophysiological role of endogenous methylarginines in regulation of endothelial NO production and vascular function. J Biol Chem 2007; 282(2): 879-87. [http://dx.doi.org/10.1074/jbc.M603606200] [PMID: 17082183]

[47]

McDonald KK, Zharikov S, Block ER, Kilberg MS. A caveolar complex between the cationic amino acid transporter 1 and endothelial nitric-oxide synthase may explain the “arginine paradox”. J Biol Chem 1997; 272(50): 31213-6. [http://dx.doi.org/10.1074/jbc.272.50.31213] [PMID: 9395443]

[48]

Martasek P, Liu Q, Liu J, et al. Characterization of bovine endothelial nitric oxide synthase expressed in E. coli. Biochem Biophys Res Commun 1996; 219(2): 359-65. [http://dx.doi.org/10.1006/bbrc.1996.0238] [PMID: 8604992]

[49]

Sessa WC, Barber CM, Lynch KR. Mutation of N-myristoylation site converts endothelial cell nitric oxide synthase from a membrane to a cytosolic protein. Circ Res 1993; 72(4): 921-4. [http://dx.doi.org/10.1161/01.RES.72.4.921] [PMID: 7680289]

[50]

Kadkhodaei Elyaderani M, Malek Askar AM, Rostami M, Aberomand M, Kheirollah AR. Inhibitory effect of asymmetric dimethylarginine and NG-Monomethyl-L-arginine methyl ester on nitric oxide synthase activity. Majallah-i Danishgah-i Ulum-i Pizishki-i Gurgan 2013; 15(3): 84-92.

[51]

Cardounel AJ, Zweier JL. Endogenous methylarginines regulate neuronal nitric-oxide synthase and prevent excitotoxic injury. J Biol Chem 2002; 277(37): 33995-4002. [http://dx.doi.org/10.1074/jbc.M108983200] [PMID: 12091378]

[52]

N C, J C. Asymmetric dimethylarginine (ADMA): a potential link between endothelial dysfunction and cardiovascular diseases in insulin resistance syndrome? Diabetologia 2002; 45(12): 1609-16.

84 The Role of Nitric Oxide in Type 2 Diabetes

Bahadoran et al.

[http://dx.doi.org/10.1007/s00125-002-0975-6] [PMID: 12488950] [53]

Bahadoran Z, Mirmiran P, Ghasemi A. Role of Nitric Oxide in Insulin Secretion and Glucose Metabolism. Trends Endocrinol Metab 2020; 31(2): 118-30. [http://dx.doi.org/10.1016/j.tem.2019.10.001] [PMID: 31690508]

[54]

Bahadoran Z, Carlstrom M. Nitric oxide: To be or not to be an endocrine hormone? 2020; 229(1): e13443.

[55]

Tessari P, Cecchet D, Cosma A, et al. Nitric oxide synthesis is reduced in subjects with type 2 diabetes and nephropathy. Diabetes 2010; 59(9): 2152-9. [http://dx.doi.org/10.2337/db09-1772] [PMID: 20484137]

[56]

Lin KY, Ito A, Asagami T, et al. Impaired nitric oxide synthase pathway in diabetes mellitus: role of asymmetric dimethylarginine and dimethylarginine dimethylaminohydrolase. Circulation 2002; 106(8): 987-92. [http://dx.doi.org/10.1161/01.CIR.0000027109.14149.67] [PMID: 12186805]

[57]

Sydow K, Mondon CE, Schrader J, Konishi H, Cooke JP. Dimethylarginine dimethylaminohydrolase overexpression enhances insulin sensitivity. Arterioscler Thromb Vasc Biol 2008; 28(4): 692-7. [http://dx.doi.org/10.1161/ATVBAHA.108.162073] [PMID: 18239148]

[58]

Dayoub H, Achan V, Adimoolam S, et al. Dimethylarginine dimethylaminohydrolase regulates nitric oxide synthesis: genetic and physiological evidence. Circulation 2003; 108(24): 3042-7. [http://dx.doi.org/10.1161/01.CIR.0000101924.04515.2E] [PMID: 14638548]

[59]

Abhary S, Burdon KP, Kuot A, Javadiyan S, Whiting MJ, Kasmeridis N, et al. Sequence variation in DDAH1 and DDAH2 genes is strongly and additively associated with serum ADMA concentrations in individuals with type 2 diabetes. 2010. [http://dx.doi.org/10.1371/journal.pone.0009462]

[60]

Lu TM, Lin SJ, Lin MW, Hsu CP, Chung MY. The association of dimethylarginine dimethylaminohydrolase 1 gene polymorphism with type 2 diabetes: a cohort study. Cardiovasc Diabetol 2011; 10(1): 16. [http://dx.doi.org/10.1186/1475-2840-10-16] [PMID: 21303562]

[61]

Zhu F, Zhou C, Wen Z, Wang DW. DDAH1 promoter -396 4N insertion variant is associated with increased risk of type 2 diabetes in a gender-dependent manner. Molecular genetics & genomic medicine 2020; 8(1): e1011-.

[62]

Stühlinger MC, Abbasi F, Chu JW, et al. Relationship between insulin resistance and an endogenous nitric oxide synthase inhibitor. JAMA 2002; 287(11): 1420-6. [http://dx.doi.org/10.1001/jama.287.11.1420] [PMID: 11903029]

[63]

Abbasi F, Asagmi T, Cooke JP, et al. Plasma concentrations of asymmetric dimethylarginine are increased in patients with type 2 diabetes mellitus. Am J Cardiol 2001; 88(10): 1201-3. [http://dx.doi.org/10.1016/S0002-9149(01)02063-X] [PMID: 11703973]

[64]

Nakhjavani M, Karimi-Jafari H, Esteghamati A, Khalilzadeh O, Asgarani F, Ghadiri-Anari A. ADMA is a correlate of insulin resistance in early-stage diabetes independent of hs-CRP and body adiposity. Ann Endocrinol (Paris) 2010; 71(4): 303-8. [http://dx.doi.org/10.1016/j.ando.2010.02.026] [PMID: 20434720]

[65]

Malecki MT, Undas A, Cyganek K, et al. Plasma asymmetric dimethylarginine (ADMA) is associated with retinopathy in type 2 diabetes. Diabetes Care 2007; 30(11): 2899-901. [http://dx.doi.org/10.2337/dc07-1138] [PMID: 17704346]

[66]

Yonem A, Duran C, Unal M, Ipcioglu OM, Ozcan O. Plasma apelin and asymmetric dimethylarginine levels in type 2 diabetic patients with diabetic retinopathy. Diabetes Res Clin Pract 2009; 84(3): 21923. [http://dx.doi.org/10.1016/j.diabres.2009.03.001] [PMID: 19344973]

[67]

Hsu CP, Hsu PF, Chung MY, Lin SJ, Lu TM. Asymmetric dimethylarginine and long-term adverse

ADMA and T2D

The Role of Nitric Oxide in Type 2 Diabetes 85

cardiovascular events in patients with type 2 diabetes: relation with the glycemic control. Cardiovasc Diabetol 2014; 13(1): 156. [http://dx.doi.org/10.1186/s12933-014-0156-1] [PMID: 25467091] [68]

Lajer M, Tarnow L, Jorsal A, Teerlink T, Parving HH, Rossing P. Plasma concentration of asymmetric dimethylarginine (ADMA) predicts cardiovascular morbidity and mortality in type 1 diabetic patients with diabetic nephropathy. Diabetes Care 2008; 31(4): 747-52. [http://dx.doi.org/10.2337/dc07-1762] [PMID: 18162497]

[69]

Krzyzanowska K, Mittermayer F, Krugluger W, et al. Asymmetric dimethylarginine is associated with macrovascular disease and total homocysteine in patients with type 2 diabetes. Atherosclerosis 2006; 189(1): 236-40. [http://dx.doi.org/10.1016/j.atherosclerosis.2005.12.007] [PMID: 16414052]

[70]

Hanai K, Babazono T, Nyumura I, et al. Asymmetric dimethylarginine is closely associated with the development and progression of nephropathy in patients with type 2 diabetes. Nephrol Dial Transplant 2009; 24(6): 1884-8. [http://dx.doi.org/10.1093/ndt/gfn716] [PMID: 19131352]

[71]

Krzyzanowska K, Mittermayer F, Wolzt M, Schernthaner G. Asymmetric dimethylarginine predicts cardiovascular events in patients with type 2 diabetes. Diabetes Care 2007; 30(7): 1834-9. [http://dx.doi.org/10.2337/dc07-0019] [PMID: 17456842]

[72]

Zobel EH, von Scholten BJ, Reinhard H, et al. Symmetric and asymmetric dimethylarginine as risk markers of cardiovascular disease, all-cause mortality and deterioration in kidney function in persons with type 2 diabetes and microalbuminuria. Cardiovasc Diabetol 2017; 16(1): 88. [http://dx.doi.org/10.1186/s12933-017-0569-8] [PMID: 28697799]

[73]

Tsikas D, Bollenbach A, Hanff E, Kayacelebi AA. Asymmetric dimethylarginine (ADMA), symmetric dimethylarginine (SDMA) and homoarginine (hArg): the ADMA, SDMA and hArg paradoxes. Cardiovasc Diabetol 2018; 17(1): 1. [http://dx.doi.org/10.1186/s12933-017-0656-x] [PMID: 29301528]

[74]

Aucella F, Maas R, Vigilante M, et al. Methylarginines and mortality in patients with end stage renal disease: A prospective cohort study. Atherosclerosis 2009; 207(2): 541-5. [http://dx.doi.org/10.1016/j.atherosclerosis.2009.05.011] [PMID: 19501358]

[75]

Kielstein JT, Salpeter SR, Bode-Boeger SM, Cooke JP, Fliser D. Symmetric dimethylarginine (SDMA) as endogenous marker of renal function—a meta-analysis. Nephrol Dial Transplant 2006; 21(9): 2446-51. [http://dx.doi.org/10.1093/ndt/gfl292] [PMID: 16766542]

[76]

Oliva-Damaso E, Oliva-Damaso N, Rodriguez-Esparragon F, et al. Asymmetric (ADMA) and Symmetric (SDMA) Dimethylarginines in Chronic Kidney Disease: A Clinical Approach. Int J Mol Sci 2019; 20(15): 3668. [http://dx.doi.org/10.3390/ijms20153668] [PMID: 31357472]

[77]

Schlesinger S, Sonntag SR, Lieb W, Maas R. Asymmetric and Symmetric Dimethylarginine as Risk Markers for Total Mortality and Cardiovascular Outcomes: A Systematic Review and Meta-Analysis of Prospective Studies. PLoS One 2016; 11(11): e0165811. [http://dx.doi.org/10.1371/journal.pone.0165811] [PMID: 27812151]

[78]

Sharma R. Sharma R. Enzyme inhibition and bioapplications: BoD–Books on Demand 2012.

[79]

Bogle RG, MacAllister RJ, Whitley GS, Vallance P. Induction of NG-monomethyl-L-arginine uptake: a mechanism for differential inhibition of NO synthases? Am J Physiol Cell Physiol 1995; 269(3): C750-6. [http://dx.doi.org/10.1152/ajpcell.1995.269.3.C750] [PMID: 7573406]

[80]

Bode-Böger SM, Scalera F, Kielstein JT, et al. Symmetrical dimethylarginine: a new combined parameter for renal function and extent of coronary artery disease. J Am Soc Nephrol 2006; 17(4): 1128-34.

86 The Role of Nitric Oxide in Type 2 Diabetes

Bahadoran et al.

[http://dx.doi.org/10.1681/ASN.2005101119] [PMID: 16481412] [81]

Closs EI, Basha FZ, Habermeier A, Förstermann U. Closs EI, Basha FZ, Habermeier A, Förstermann U. Interference of L-arginine analogues with L-arginine transport mediated by the y+ carrier hCAT2B. Nitric oxide : biology and chemistry. 1997; 1(1): 65-73.

[82]

Marliss EB, Chevalier S, Gougeon R, et al. Elevations of plasma methylarginines in obesity and ageing are related to insulin sensitivity and rates of protein turnover. Diabetologia 2006; 49(2): 351-9. [http://dx.doi.org/10.1007/s00125-005-0066-6] [PMID: 16369774]

[83]

Kingwell BA, Formosa M, Muhlmann M, Bradley SJ, McConell GK. Nitric oxide synthase inhibition reduces glucose uptake during exercise in individuals with type 2 diabetes more than in control subjects. Diabetes 2002; 51(8): 2572-80. [http://dx.doi.org/10.2337/diabetes.51.8.2572] [PMID: 12145173]

[84]

Schneider MP, Ott C, Schmidt S, Kistner I, Friedrich S, Schmieder RE. Poor glycemic control is related to increased nitric oxide activity within the renal circulation of patients with type 2 diabetes. Diabetes Care 2013; 36(12): 4071-5. [http://dx.doi.org/10.2337/dc13-0806] [PMID: 24130344]

[85]

Lee Y, Mehrotra P, Basile D, et al. Specific Lowering of Asymmetric Dimethylarginine by Pharmacological Dimethylarginine Dimethylaminohydrolase Improves Endothelial Function, Reduces Blood Pressure and Ischemia-Reperfusion Injury. J Pharmacol Exp Ther 2021; 376(2): 181-9. [http://dx.doi.org/10.1124/jpet.120.000212] [PMID: 33214214]

[86]

Trocha M, Szuba A, Merwid-Lad A, Sozański T. Effect of selected drugs on plasma asymmetric dimethylarginine (ADMA) levels. Pharmazie 2010; 65(8): 562-71. [PMID: 20824955]

[87]

King DE, DeLegge M. The impact of fiber supplementation on ADMA levels 2009. [http://dx.doi.org/10.1177/0884533608329229]

[88]

Eid HMA, Arnesen H, Hjerkinn EM, Lyberg T, Ellingsen I, Seljeflot I. Effect of diet and omega-3 fatty acid intervention on asymmetric dimethylarginine. Nutr Metab (Lond) 2006; 3(1): 4. [http://dx.doi.org/10.1186/1743-7075-3-4] [PMID: 16396682]

[89]

Asagami T, Abbasi F, Stuelinger M, et al. Metformin treatment lowers asymmetric dimethylarginine concentrations in patients with type 2 diabetes. Metabolism 2002; 51(7): 843-6. [http://dx.doi.org/10.1053/meta.2002.33349] [PMID: 12077728]

[90]

Tahara N, Yamagishi S, Mizoguchi M, Tahara A, Imaizumi T. Pioglitazone decreases asymmetric dimethylarginine levels in patients with impaired glucose tolerance or type 2 diabetes. Rejuvenation Res 2013; 16(5): 344-51. [http://dx.doi.org/10.1089/rej.2013.1434] [PMID: 23777507]

[91]

Staniloae C, Mandadi V, Kurian D, et al. Pioglitazone improves endothelial function in non-diabetic patients with coronary artery disease. Cardiology 2007; 108(3): 164-9. [http://dx.doi.org/10.1159/000096601] [PMID: 17077630]

[92]

King DE, Player M, Everett CJ. The impact of pioglitazone on ADMA and oxidative stress markers in patients with type 2 diabetes. Prim Care Diabetes 2012; 6(2): 157-61. [http://dx.doi.org/10.1016/j.pcd.2011.06.002] [PMID: 21705294]

[93]

Adingupu DD, Göpel SO, Grönros J, et al. SGLT2 inhibition with empagliflozin improves coronary microvascular function and cardiac contractility in prediabetic ob/ob−/− mice. Cardiovasc Diabetol 2019; 18(1): 16. [http://dx.doi.org/10.1186/s12933-019-0820-6] [PMID: 30732594]

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CHAPTER 5

Nitric Oxide-Related Oral Microbiota Dysbiosis in Type 2 Diabetes Zahra Bahadoran1, Pedro González-Muniesa2,3,4,5, Parvin Mirmiran1,6 and Asghar Ghasemi7, * Nutrition and Endocrine Research Center, Research Institute for Endocrine Sciences, Shahid Beheshti University of Medical Sciences, Tehran, Iran 2 Department of Nutrition, Food Science and Physiology, School of Pharmacy and Nutrition, University of Navarra, Pamplona, Spain 3 Center for Nutrition Research; School of Pharmacy and Nutrition, University of Navarra Pamplona, Spain 4 CIBER Physiopathology of Obesity and Nutrition (CIBERobn), Carlos III Health Institute (ISCIII), Spain 5 IDISNA – Navarra Institute for Health Research, Pamplona, Spain 6 Department of Clinical Nutrition and Human Dietetics, Faculty of Nutrition Sciences and Food Technology, National Nutrition and Food Technology Research Institute,Shahid Beheshti University of Medical Sciences, Tehran, Iran 7 Endocrine Physiology Research Center, Research Institute for Endocrine Sciences, Shahid Beheshti University of Medical Sciences, Tehran, Iran 1

Abstract: The nitrate (NO3)-nitrite (NO2)-nitric oxide (NO) pathway, as a storage reservoir for endogenous NO production, is dependent on the oral bacteria with NO3reducing capacity. Undesirable changes of oral microbiota towards a decreased load of health-related NO3-reducing bacteria and an overgrowth of pathogenic species, leading to subsequent decreased NO2 production in the oral cavity and decreased systemic NO availability, are now considered risk factors for the development of insulin resistance and type 2 diabetes (T2D). This chapter discusses available evidence focusing on oral microbiota dysbiosis in T2D, especially NO3-reducing bacteria and their metabolic activity (including NO3-reductase and NO2-reductase activity), affecting net oral NO2 accumulation and the NO3-NO2-NO pathway.

Keywords: Nitrate, Nitrite, Nitric oxide, Nitrate reductase, Nitrite reductase, Oral microbiota, Type 2 diabetes. Corresponding author Asghar Ghasemi: Endocrine Physiology Research Center, Research Institute for Endocrine Sciences, Shahid Beheshti University of Medical Sciences, Tehran, Iran; [email protected]., No. 24, Erabi Street, Velenjak, Tehran, Iran; Phone: +98 21 22409309; Fax: +98 21 22416264.

*

Asghar Ghasemi, Khosrow Kashfi, Zahra Bahadoran (Eds.) All rights reserved-© 2022 Bentham Science Publishers

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INTRODUCTION Dysbiosis in the oral microbiota is associated with increased cardiovascular and metabolic disorders [1, 2]. It has been suggested that the link between oral microbiota dysbiosis and cardiometabolic disorders is in part due to decreased abundance of species with nitrate (NO3)-reducing capacity and concurrent increase of pathogenic bacterial species in the oral cavity [3, 4]. In the oral cavity, the commensal facultative and obligate anaerobic bacteria with NO3-reducing capacity reduce salivary NO3 to nitrite (NO2) via a two-electron reduction, using anaerobic respiration by the action of NO3 reductases (NaRs) [5]. Although mammalian NaRs activity may contribute to mammalian NO3 reduction and regulation of NO2 and nitric oxide (NO) metabolism in the human body [6], the role of oral microbiota is of great importance. Although changes in the composition of oral microbiota in type 2 diabetes (T2D) have been reported [7, 8], this issue remains a matter of debate [9, 10]; T2D is associated with increased loading of diseases-associated oral bacteria and reduced community of health-related bacteria [11]. Since the recycling process of inorganic NO3 to NO, a ubiquitous endocrine hormone involved in glucose and insulin homeostasis [12], is critically dependent upon oral commensal NO3reducing bacteria [13, 14], oral dysbiosis of these communities has been suggested to contribute to the development of insulin resistance T2D [15]. In this chapter, we focus on NO-related oral microbiota dysbiosis in T2D. AN OVERVIEW OF ORAL MICROBIOTA The term microbiota describes the ecological community of symbiotic, commensal, and pathogenic microorganisms [16]. Oral microbiota is the second largest, second most diverse, complex, and dynamic microbial community in the human body, including about 775 species of bacteria (12 phyla and 185 genera) [17]. The commensal bacteria resident in the oral cavity interacts with the host in a balanced manner, whereas potentially pathogenic bacteria emerge following an imbalanced oral resident microbiota [18]. The concept of a fluid continuum now replaces the concept of commensalism vs. pathogenicity as a fixed duality since labeling bacteria as strict commensals vs. pathogens was a too restrictive approach [19]. About 96% of the oral microbiota comprises the six broad phyla, Firmicutes, Actinobacteria, Proteobacteria, Fusobacteria, Bacteroidetes, and Spirochaetes [17, 20]. The Saccharibacteria, Synergistetes, SR1, Gracilibacteria, Chlamydia, Chloroflexi, Tenericutes, Euryarchaeota, TM7, and Chlorobi comprise 4% of the remaining taxa [21]. The human oral microbiota database (HOMD) provides a

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comprehensive database of oral bacterial taxa, a 16S rRNA identification tool, and genome sequences (www.homd.org). Although the rat tongue microbiota is less diverse than the human [99±40 vs. 249±30 operational taxonomic units (OUT, a pragmatic proxy for species at different taxonomic levels, and used to categorize bacteria based on sequence similarity); 2.92±0.53 vs. 5.54±0.33 Shannon diversity index], the physiological activity of oral microbiota is comparable in both species [4]. The Firmicutes and Proteobacteria comprised 40-80% of the tongue communities in both humans and rats; however, the Actinobacteria is the predominant phyla in rat tongues, whereas human tongues contained more Bacteroidetes [4]. About 70% of human tongue bacterial composition comprises the gram-positive species (mainly Staphylococcus, Micrococcus, and Streptococcus), and 30% are gram-negative [22]. The oral microbiota has both pro- and anti-inflammatory activities that maintain oral homeostasis [23]. The balance between the resident species in the oral cavity determines how the microbiota changes toward a health-related (symbiosis) state or a disease-associated (dysbiosis) state [16]. Factors including poor oral hygiene, gingival inflammation, change in saliva flow rate or composition, aging, medications, diseases, dietary habits, physical activity, smoking, and a poor immune system drive the oral microbiota composition to dysbiosis and overgrowth of pathogenic species [24, 25]. From the metabolic function point of view, oral bacteria contribute to 4 major metabolic pathways: 1) saccharolytic bacteria, including Streptococcus, Actinomyces, and Lactobacillus species that metabolize carbohydrates into organic acids; 2) proteolytic and amino acid-degrading bacteria, including Fusobacterium, Prevotella, and Porphyromonas species that metabolize proteins and peptides into amino acids, and further into short-chain fatty acids, ammonia, sulfur compounds, and indole/skatole) [26]; 3) bacteria like Streptococcus, Actinomyces, and Lactobacillus that contribute to alkalinization and acid neutralization via arginine/agmatine deiminase system; 4) species including Actinomyces and Veillonella with NO3-reducing capacity that convert NO3 to NO2 and inhibits bacterial acid production [26]. The metabolic activities of oral bacteria are closely related to systemic metabolic health and diseases [16, 26]. Although it is difficult to make a clear distinction, carbohydrate metabolizers and acid-producing bacteria, leading to the accumulation of organic acids, are related to oral dysbiosis. In contrast, those involving accumulating ammonia and NO2 and inhibiting acid production are considered health-associated species [16, 26].

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Sometimes, oral dysbiosis is due to a change in the metabolic properties of bacteria rather than a change in the community, which means the overall community structure remains relatively intact while its metabolic properties are drastically changed [27]. The Porphyromonas gingivalis, Prevotella intermedia and Veillonella modify their metabolic properties in response to environmental factors [26]. Oral Nitrate-Reducing Bacteria Among the oral microbiota related to metabolic homeostasis, the role of bacteria in NaR activity is critical because of their impact on the NO3-NO2-NO pathway, the central part of the nitrogen cycle in humans [13]. There is a symbiotic relationship between oral NO3-reducing bacteria and the host [5, 28] because these species can inhibit the outgrowth of the pathogens like Escherichia coli and Candida albicans via the produced NO2 [29, 30] and provide a source for systemic NO production compensating NO insufficiency [28]. The oral NO3 reduction in humans mainly occurs on the dorsal surface of the tongue [5]. The oral NaR activity by the commensal facultative and obligate anaerobic bacteria occurs under a low-oxygen and neutral or slightly alkaline environment (pH ~ 7.0-8.0) [5, 31]. Bacterial NO3 reduction occurs by the action of three types of NaRs, including a cytoplasmic assimilatory nitrate reductase (NAS), a membrane-associated cytoplasmic nitrate reductase (NarG, NarZ), and a periplasmic nitrate reductase (NAP); however, NarG has been suggested as the enzyme responsible for the accumulation of NO2 from NO3 in the oral cavity [13]. The NO2 produced by the bacteria may be subjected to further reduction since many of these bacteria have additional reductases that induce NO2 reduction to nitrogen derivates (i.e., NO, N2) (under the anaerobic and acidic condition with an optimum pH = 4.7); oral NO2 can also be diverted into ammonia production, upon a pathway called as “dissimilatory nitrate reduction to ammonium” or DNRA pathway [13, 32]. The complete denitrification pathway (proceeding by coppercontaining nitrite reductase, NirK or cytochrome c nitrite reductase, NirS, quinoldependent type NO reductase, qnorB, and N2O reductase, nosZ), which usually occur in dental plaques under aerobic conditions, may result in high-concentration toxic NO and development of periodontitis and dental caries [32]. High levels of ammonia-forming NO2 reductases (i.e., NADH-dependent, NirBD nitrite reductase, and cytochrome c nitrite reductase, Nrf) are suggested to steal NO2 away from the systemic NO production [33]. In humans, oral NaR activity produces 85.4±15.9 (range 13.4-184.6) nmol NO2/min [5]. Salivary NO2 has been reported to reach its maximum concentration following 15-30 min (from basal levels of 0.26±0.04 to 2.11±0.56 mM) upon oral

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NO3 ingestion (at a dose of 10 mg/kg) [14]. Females have greater oral NaR capacity [34]; the explanation for this sex difference is not fully established. However, it is determined that the oral microbiota’s diversity and overall community structure are not the response [34]. The potential differences in residence site, group size, bacterial species, or sex-differences in bacterial metabolic activity have been suggested as explanations [34]. In rats, NO3-reducing bacterial load is 10-fold higher in the posterior than the anterior of the tongue (65% vs. 6.5%), and NO2 production is less than 7.8 nmol/cm2/h [35]. At the posterior of the tongue, NO3 reduction has Km = 830-1100 µM NO3, Vmax = 600-1000 nmol/cm2/h NO2, and the NO2 production is increased by increasing NO3 substrate levels (10 and 20 mM) to 400 and 800 nmol/cm2/h [35]. Increasing NO3 from 10 to 10,000 µM improved NO2 production in the rat tongue up to 1000 µM [29]. The source of salivary NO3, used as fuel for the oral NO3-reducing bacteria, is the entero-salivary circulation of NO3 (both from diet and endogenous NO production), which encourages the bacteria to reside and survive within the oral cavity and respire NO3 [5, 13]. NO3 is taken up from the plasma by the salivary glands, concentrated by 10-20 folds (200-1000 µM), and secreted into saliva [36, 37]. In humans, the parotid gland is the main contributor to concentrating salivary NO3, and its NO3 concentration is approximately 3-fold more than whole mixed saliva [38]. Fasting NO2 salivary concentrations range 100-1000 fold higher than the concentration in plasma [36]. The NO3-reducing species represent about 20±16% of all measured taxa in the oral cavity of humans [15]. About 132 NaR-positive species reside within the oral cavity, on the tongue, supragingival plaque, and saliva; the Veillonella (47 species, 35.6%) and Actinomyces (52 species, 39.4%) genera are the majority of bacteria isolated from the three sites [5]. Other species, including Porphyromonas, Fusobacterium, Leptotrichia, and Brevibacillus, are also involved in oral NaR activity [5, 39]. The genus Veillonella, Actinomyces, Haemophilus, and Neisseria are the most abundant genera involved in the oral NO3-reducing activity [3]. The majority of OTUs with NaR activity have been identified to be originated from the genera Granulicatella, Actinomyces, Veillonella, Prevotella, Neisseria, and Haemophilus [39]. Commensal Neisseria has been reported as the core of healthy oral microbiota in humans [40]. Others reported the Veillonella, Prevotella, Haemophilus, and Streptococcus as the main common genera on the tongue dorsum of healthy individuals [41], where a significant amount of NO2 is produced in the oral cavity. Prevotella and Veillonella (~ 42.1±10.1% and 20.5±12.3%) are the leading oral NO3-reducing bacteria in healthy humans [42].

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Notably, the oral bacteria proposed as key NO2 accumulators (e.g., Prevotella and Veillonella) based on in vitro experiments do not thrive under high NO3 availability in vivo [43]. Therefore, it could not contribute to NO2 production in vivo in response to oral NO3 loading [43]. Tongue NO3-reducing bacteria are mainly Gram-negative cocci (58.1%), while in dental plaque, Gram-positive rods (73%) are the main flora [5]. Major NO3reducing bacteria on the tongue are the strict anaerobes (Veillonella atypica and Veillonella dispar) and the facultative anaerobes (Actinomyces odontolyticus and Rothia mucilaginosa); the Actinomyces odontolyticus, the second most common tongue isolate, is responsible for the primary oral NO3 reducing activity (a rate of 187.8 pmol NO2/min/µg protein, under anaerobic conditions with 2 mM NO3) [5]. Some NO3-reducing bacterial species, including Veillonella parvula, Corynebacterium spp., Selenomonas noxia, and Eikenella corrodens, have only been found in dental plaques [5]. The Actinomyces odontolyticus and Veillonella dispar were reported to contribute to at least 80% of oral NO3 reduction [39]. Metagenomic analysis of NO3reducing bacteria in the oral cavity of healthy humans reported composition of Streptococcus (20.2±9.7%), Veillonella (14.1±4.1%), Prevotella (11.8±5.9%), Neisseria (10.8±9.62%), and Haemophilus (8.6±4.93%) [39]. The community with the highest NO3-reducing capacity includes fourteen species present at an abundance of at least 0.1%, including Neisseria flavescens, Haemophilus parainfluenzae, Neisseria mucosa, Prevotella melaninogenica, Granulicatella adiacens, Veillonella dispar, Veillonella atypica, Veillonella parvula, Neisseria sicca, Prevotella salivae, Actinomyces odontolyticus, Actinomyces viscosus, Actinomyces oris, and Neisseria subflava [39]. Regardless of the inter- and intraindividual variations and changes in tongue microbiota, Prevotella melaninogenica and Veillonella dispar seems to be the most abundant species of NO3-reducing bacteria [44]. The temporal dynamics of tongue microbiota in the case of NO3-reducing bacteria is considerable; during 15-21 days, a profound within-person variation in the abundance of the NO3-reducing bacteria, including Prevotella melaninogenica (37%), Veillonella dispar (35%), Haemophilus parainfluenzae (79%), Neisseria subflava (70%), Veillonella parvula (43%), Rothia mucilaginosa (60%), and Rothia dentocariosa (132%) on the dorsal surface of the tongue has been reported caused variations of salivary and circulating NO metabolites [44]. In rats, oral NO3 reduction was evident on the dorsal epithelium of the posterior one-third of the tongue [29], where higher proportions of gram-negative bacteria were found deep within the tongue clefts than on the surface [35]. The

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Staphylococcus sciuri (40%), Staphylococcus intermedius (25%), Pasteurella spp. (20%), Streptococcus spp. (10%), and Listonella (5%) were involved in NaR activity in the tongue of rats [35]. In addition to NO3-reducing bacteria, other species genetically lacking NaR indirectly contribute to the NO3 reduction community as helper species maximizing the community’s metabolic efficiency [39]. The species with NO2reducing capacity (e.g., Neisseria gonorrhoeae and Escherichia coli) may limit sufficient salivary NO2 accumulation, thereby suppressing the NO3-NO2-pathway [13, 39]. Some anaerobic bacteria associated with chronic periodontitis convert NO3 to ammonia rather than NO2 [4]; such species possessing ammonia-forming NiRs (e.g., Leptotrichia and Prevotella) have been suggested, can steal NO2 away from gastric NO production, resulting in increased blood pressure [33]. The species like Haemophilus and Neisseria, possessing NO-forming NiRs and involving the denitrification pathway, may also inhibit NO2 accumulation [32]; however, they produce physiological levels of NO in the oral cavity and are related to lower levels of blood pressure [33]. As many oral NO3-reducing bacteria can further process the produced NO2, the NO3-reducing bacteria in general and NO2 accumulating bacteria in specific should be differentiated [43]. Therefore, an ideal NO3-reducing community needs higher NO3 reduction efficacy (more potent NO3-reducing bacteria and helper species) along with no NiR enzymes [28] or explicitly lacking ammonia-forming NiRs. The use of the single-taxon comparison approach and selective-assessing NO3reducing species in previous studies has limited detection of complex synergistic and potential antagonistic relationships between NO3-reducing species with the oral bacterial ecosystem, a critical factor determining how the species are beneficial or detrimental to the host metabolism [45]. A network analysis of NO3reducing oral microbiota revealed two diverse modules of co-occurring bacteria (Rothia-Streptococcus and Neisseria-Haemophilus) related to cardiovascular and cognitive indices of health and a module (Prevotella-Veillonella) associated with pro-inflammatory metabolism and progression of dysbiosis [45]. Oral Nitrate Reduction and Nitric Oxide Homeostasis The critical role of NO3-reducing bacteria on systemic NO availability is highlighted by the evidence indicating that circulating NO2 is decreased and NOmediated biological effects are partially or entirely prevented when the oral microbiota is abolished via antiseptic mouthwash [14, 46, 47]. The oral bacterial community was reduced by 80%, and NaR activity in the oral cavity was abolished entirely following the use of antibacterial mouthwash [14]; similarly, plasma NO2 concentrations were expected to be increased following an oral dose

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of inorganic NO2 (from 103±9 to 242±34 and 286±62 nM after 1 and 3 h), which remained unchanged (72±23 nM, Cmax=2 h after ingestion) due to the use of an antiseptic mouthwash [14]. Likewise, the vascular effects of NO3 supplementation are blunted by removing saliva from the mouth or using an antibacterial mouthwash. In rats, chlorhexidine antiseptic mouthwash (0.3 ml twice daily, sprayed at the dorsal section of the tongue for one week) decreased the oral load of NO3-reducing bacteria, NO3induced gastric NO production (from ~13,000 to ~2,000 ppb), and circulating NO2 levels (from 1750 to 500 nM) and blunted NO3-induced blood pressure reduction [47]. Impairment of the entero-salivary circuit of NO3 (via spitting saliva) substantially prevented elevation of circulating NO2 in response to ingested NO3 (500 mL beetroot juice containing 45 mM NO3), blocked NO3-induced hypotensive effects, and abolished the inhibitory effects on platelet aggregation in healthy humans [48]. Such evidence implies that circulating NO2 availability (as a storage pool of systemic NO) after ingestion of NO3 is critically dependent on oral NaR activity by the commensal bacteria, and removal of these bacteria diminishes the NOdependent biological effects of dietary NO3 [14]. The importance of oral microbiota in NO generation is also clearly established by the experiments that reported a negligible gastric NO formation, even following the dietary load of NO3, in germ-free sterile rats [49]. The variations of circulating NO metabolites and substantial inter-individual difference in response to oral ingestion of inorganic NO3 (e.g., increased plasma NO2 40-800 nM, with a timeto-peak range of 1.5-6 h, following an oral dose of NO3 [50]) are partially attributed to profound inter- and intra-individual variations of NO3-reducing bacteria abundance on the human tongue [44]. The NO2 produced by the NO3-reducing bacteria is a vital storage pool of systemic NO when NO production by the NO synthase (NOS) system is compromised [48, 51]. The abundance of NO3-reducing bacteria is associated with the generation of salivary NO2, and the subjects with higher OUT levels of NO3reducing bacteria (62.6±6.9% vs. 40.9±6.1%) on the dorsal surface of the tongue significantly produced a more significant amount of salivary NO2 following the ingestion of inorganic NO3 [42]. A higher abundance of Rothia and Neisseria and a lower abundance of Prevotella and Veillonella are related to higher circulating NO2 in response to NO3 supplementation in vivo [43].

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Changes in Oral Microbiota in T2D There is a mutual relation between oral microbiota and T2D. Oral microbiota seems to contribute to the development of T2D [52, 53], and diabetes makes the oral bacterial composition more pathogenic, as transplanting the oral microbiota of diabetic mice to germ-free normal mice results in the development of inflammation [54]. Oral diabetic dysbiosis, characterized by the overgrowth of specific bacteria, including Porphyromonas gingivalis, Prevotella intermedia, and Prevotella copri, is associated with the progression of insulin resistance and impaired glucose metabolism [55 - 57]. The role of oral microbiota in glucose and insulin homeostasis and progression of T2D is greatly supported by several epidemiological studies linking periodontitis (caused by an overgrowth of gram-negative bacteria including Porphyromonas gingivalis, Actinobacillus actinomycetemcomitans, Tannerella forsythia, Treponema denticola, and Prevotella intermedia in the oral cavity [58, 59]) with development of T2D and insulin resistance [60, 61]. The Aggregatibacter actinomycetemcomitans (OR= 2.34, 95% CI=1.31-4.18), Fusobacterium nucleatum (OR= 2.43, 95% C=1.32-4.48), Porphyromonas gingivalis (OR= 2.33, 95% CI=1.33- 4.10), and Veillonella parvula (OR=3.03, 95% CI=1.54-5.98) were associated with elevated risk of prediabetes [62]. Likewise, the severity of periodontitis can predict poor glycemic control in patients with T2D over time [63], and improved glycemic control can be achieved following periodontal treatment in patients with T2D [64, 65]. Vice versa, effective glycemic control in patients with T2D positively changes salivary microbiota composition by decreasing the abundance of Prevotella copri, Alloprevotella rava, Ralstonia pickettii, genera that induced periodontitis [57]. Some bacteria in the oral cavity have been proposed as the main species related to metabolic disorders, e.g., metabolic syndrome (MetS) and T2D. Table 1 addresses changes in oral microbiota in patients with T2D compared to healthy subjects. The Rothia, Capnocytophaga, Granulicatella, Lautropia, Cardiobacterium, and Aggregatibacter are abundant among subjects with MetS [66]. Some genera, such as Leptotrichia, Staphylococcus, Catonella, and Bulleidia, are introduced as hyperglycemia-related bacteria [52]. Subjects with dysglycemia showed a lower abundance of Peptococcus and a higher abundance of Dialister [66]. In patients with T2D, the Fusobacteria and Actinobacteria are more abundant while Proteobacteria are reduced [7]. Furthermore, the Firmicutes to Bacteroidetes ratio increased in patients with T2D, with higher numbers of Neisseria, Streptococcus, Haemophilus, Pseudomonas genera, and lower numbers of Acinetobacter were observed in these patients compared with healthy subjects [8].

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Table 1. Changes in oral microbiome community associated with hyperglycemia and type 2 diabetes. Increased Genera [52, 59, 66-68]

Decreased Genera [7, 8, 53]

Phyla: Fusobacteria, Actinobacteria, Veillonella parvula, V. dispar, Eikenella corrodens species Genera: Rothia, Capnocytophaga, Granulicatella, Lautropia, Cardiobacterium, Aggregatibacter, Leptotrichia, Staphylococcus, Catonella, Bulleidia, Dialister, Neisseria, Streptococcus, Haemophilus, Pseudomonas, Gemella, Eikenella, Selenomonas, Actinomyces, Veillonella, P. gingivalis, T. forsythensis Treponema denticola, Prevotella nigrescens, Streptococcus sanguinis, Streptococcus oralis, Streptococcus intermedius species

Phyla: Proteobacteria Genera: Peptococcus Acinetobacter, Actinomyces, Atopobium, Bifidobacterium, Scardovia, Corynebacterium, Porphyromonas, Filifactor, Eubacterium, Synergistetes, Tannerella, Treponema

Patients with uncontrolled T2D also had higher percentages of total clones of Aggregatibacter, Neisseria, Gemella, Eikenella, Selenomonas, Actinomyces, Capnocytophaga, Fusobacterium, Veillonella, and Streptococcus genera, and lower percentages of Porphyromonas, Filifactor, Eubacterium, Synergistetes, Tannerella, and Treponema genera [67]. The quantity of the Porphyromonas gingivalis, Treponema denticola, and Tannerella forsythia (the most critical pathogens in adult periodontal disease) was significantly higher in patients with T2D and positively correlated with HbA1c levels [69]. The total mean count for Capnocytophaga spp. was also significantly higher in patients with T2D [70]. An elevated abundance of Treponema denticola, Prevotella nigrescens, Streptococcus sanguinis, Streptococcus oralis, and Streptococcus intermedius was reported in supragingival plaque in patients with T2D [59]. Patients with T2D showed lower Bifidobacteria [71], Actinobacteria, and its belonging genera like Actinomyces and Atopobium in the oral cavity [53]. A higher load of Actinomyces and Atopobium were associated with a lower chance of having T2D by 66% and 72%, respectively [53]. In animal models of T2D, hyperglycemia-induced inflammation causes an adverse shift of oral microbiota toward a higher load of pathogens and higher Enterobacteriaceae, Aerococcus, Enterococcus, and Staphylococcus [54]. Highfat diet-induced diabetic mice displayed an increased prevalence of periodontal pathogenic microbiota, including Fusobacterium nucleatum and Prevotella intermedia in the oral cavity [72]. Diabetes-related factors, i.e., increased glucose levels, advanced glycation end products (AGEs), and overproduction of proinflammatory cytokines inducing inflammation in periodontal tissues, are suggested to have a central role in the overgrowth of pathogenic species in the oral cavity [11, 61, 73]. Elevated gingival levels of interleukine-1β (IL1-β), tumor

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necrosis factor-α (TNF-α), interleukin-6 (IL-6), receptor activator of nuclear factor kappa-light-chain-enhancer of activated B cells (NF-kB) ligand (RANKL)/osteoprotegerin (OPG), and oxygen metabolites in poorly-controlled diabetes are also suggested as pathogenic mechanisms linking diabetes and oral microbiota changes [74]. Mechanisms Linking Oral Dysbiosis with Impaired Glucose and Insulin Homeostasis The underlying mechanisms linking oral microbiota dysbiosis and the risk of T2D are rarely documented. Most available evidence introduces local and systemic inflammation as a critical linking mechanism [75, 76]. As addressed in Fig.(1)., two main mechanisms are involved: (1) translocation of the oral pathogens, e.g., P.gingivalis (a key species in the development of chronic periodontitis) and their toxins, including lipopolysaccharide (LPS) and gingipain into critical organs involved in carbohydrate metabolism and (2) decreased NO bioavailability predisposing to insulin resistance and T2D. Transferring the oral pathogens (e.g., P.gingivalis) to adipose tissue [76], hepatocytes [77, 78], skeletal muscle [79, 80], brain [77], and pancreatic β-cells [81 - 83] may lead to inflammation, cell apoptosis, tissue dysfunction and imbalanced systemic immune responses. The pathogen translocation into the βcells disturbs islet morphology, and induces SerpinE1 (a serine protease inhibitor) and β-cell apoptosis, leading to impaired glucose metabolism [81]. Likewise, the pathogens-originated toxic metabolites induce trans-differentiation of α and βcells to bihormonal cells, expressing both glucagon and insulin [82]. LPS stimulates insulin secretion, upregulates gene expression of immune responserelated factors (a cluster of differentiation 8a, Cd8a, and Cd14), intercellular adhesion molecule-1 (ICAM-1), and insulin signaling-related factors (glucose--phosphatase catalytic subunit, G6PC, and insulin-like 3, InsL3) in the β-cell [83]. In adipose tissue, P.gingivalis down-regulates the expression of a number of genes involved in insulin sensitivity, including peroxisome proliferator-activated receptor γ (PPARγ), peroxisome proliferator-activated receptor α (PPARα), C1q and TNF Related 9 (C1QTNF9), insulin Receptor Substrate 1 (IRS1), sirtuin 1 (Sirt1), and solute carrier family 2 member 4 (Slc2a4) [76]. P.gingivalis translocation from the mouth into skeletal muscle induces intramuscular fat deposition and impairs insulin signaling and glucose uptake; these effects are mediated via induction of expression of TNF-α, Ccl2, IL-6, PPARγ coactivator1β, and myogenin, and decreasing mRNA expression of forkhead box O1 (Foxo1) and Akt phosphorylation [79]. P.gingivalis translocation into hepatocytes suppresses insulin-induced phosphorylation of IRS-1, Akt, and glycogen synthase

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kinase-3β and decreases glycogen synthesis, leading to elevated plasma glucose [78]. Moreover, P.gingivalis induces oxidative stress and inflammation in the liver [77]. In the brain, P.gingivalis reduces glucose utilization (indicated as decreased glucose-6-phosphate, fructose-6-phosphate, and pyruvate levels), decreases pentose phosphate shunt activity and NADPH, and induces oxidative stress [77].

Fig. (1). Underlying mechanisms linking oral dysbiosis to impaired glucose and insulin homeostasis. 1) Potential translocation of the oral pathogens, e.g., P. gingivalis and toxic metabolites, including lipopolysaccharides and gingipain, into peripheral tissues impairs insulin secretion and insulin signaling and disturbs the balance of glucose production/utilization in target tissues. 2) Decreased NO bioavailability resulting in insulin resistance and the development of T2D. LPS, lipopolysaccharide; NO, nitric oxide; T2D, type 2 diabetes; TG, triglycerides; ICAM-1, intercellular adhesion molecule-1, G6PC, glucose-6-phosphatase catalytic subunit; InsL3, insulin-like 3; IL1-β interleukine-1β; TNF-α, tumor necrosis factor-α; IL-6, interleukine-6; NF-kB, nuclear factor kappa-light-chain-enhancer of activated B cells; PPARγ; peroxisome proliferator-activated receptor-γ, PPARα, peroxisome proliferator-activated receptor- α, C1QTNF9, C1q and TNF related 9; IRS1, insulin receptor substrate 1; Sirt1, sirtuin 1, Slc2a4, solute carrier family 2 member 4; CRP, c-reactive protein; JNK, c-JUN N-terminal kinase; ERK, p38 and extracellular signal-regulated kinase. Created with Biorender.com.

The second pathway linking oral dysbiosis to impaired insulin and glucose homeostasis is decreased NO bioavailability see Fig. (1). This issue is discussed in the following section in detail.

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Oral Nitrate-Reducing Bacteria and Nitric Oxide Metabolism in T2D Compared to healthy subjects, those with T2D had lower oral NO3-reducing capacity, as determined by the amount of salivary NO2 to total nitrates concentration; on the other hand, high-NaR values had a higher whole-body NO exposure and showed a better glycemic response and more reduction of blood pressure following ingestion of a NO3-rich meal [84]. Dysbiotic NO3-reducing bacteria in T2D and their relation to the progression or prevention of impaired carbohydrate metabolism are under investigation. The oral dysbiosis of NO3-reducing bacteria may be involved in the development of T2D and worsening of glycemic control in patients with T2D by blunting the NO3-NO2-NO pathway and decreasing NO availability. In a population of 300 non-diabetic adults aged 20-55 years, a higher NO3-reducing taxa summary score (NO3TSS, indicating the total community exposure of NO3-reducing microbiota in the oral cavity) was associated with a lower natural log-transformed homeostatic model assessment of insulin resistance (HOMA-IR) (adjusted β regression=0.09, 95% CI=0.15-0.03) and 1.03 mg/dL (95% CI=1.90-0.16) lower levels of plasma glucose [15]. Likewise, the association of oral NO3-reducing bacterial load with a prevalence ratio of prediabetes was statistically borderline significant (0.79, 95% CI= 0.61-1.03) in a model adjusted for age, sex, race, education, body mass index, smoking, percentage of periodontal sites and dietary pattern [15]. A higher load of some oral NO3-reducing bacteria, e.g., Rothia dentocariosa, was associated with a lower chance of insulin resistance and prediabetes [15]. In contrast, some species, including Prevotella and Veillonella, are associated with T2D and its complications (e.g., atherosclerotic plaque) [85] and elevated risks of all-cause mortality [86]. On the other hand, an elevated oral load of species with NO2-reducing capacity, e.g., Porphyromonas gingivalis, occurred in T2D [69]. This has been suggested to lead to a decreased capacity of NO2 accumulation in the oral cavity in patients with T2D. CONCLUDING REMARKS T2D is associated with oral microbial dysbiosis, and a low level of health-related NO3-reducing species decreases the oral NaR capacity and thus systemic NO availability. On the other hand, oral microbiota dysbiosis and reduced NO availability contribute to impaired glucose metabolism and insulin resistance, therefore being causal for T2D. This bilateral linkage may potentially form a vicious cycle in T2D. Restoration of the oral microbiota to a health-associated state may be suggested as a therapeutic approach to potentiate systemic NO production and provide a rescue pathway for such conditions of NO insufficiency. It has been suggested that inorganic NO3 may act as a prebiotic modulating oral

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microbiota, leading to potentiate NO2 production and systemic available NO. Inorganic NO3 may improve oral net NO2 production and systemic NO availability by increasing Neisseria and Rothia and decreasing Prevotella and Veillonella species [4, 43, 87]. Since shifting from Prevotella-Veillonella towards Neisseria-Haemophilus and Streptococcus Rothia modules, in response to NO3 supplementation have been related to metabolic health [45], it may be considered a potential therapeutic agent in patients with T2D. Inorganic NO3 may also increase the salivary flow rate and prevent decreased oral pH by inhibiting acidproducing bacteria [88 - 90]; NO3, therefore, may be considered a potential prebiotic for oral microbiota dysbiosis associated with T2D [91]. Appropriate changes provide a more optimal environment for NaR activity in the oral cavity and boost systemic NO availability. Furthermore, antibiotic mouthwash resulting in loss of health-related NO3-reducing bacteria and decreased systemic NO bioavailability should be reconsidered. CONSENT FOR PUBLICATION Not applicable. CONFLICT OF INTEREST The author declares no conflict of interest, financial or otherwise. ACKNOWLEDGEMENTS Declared none. REFERENCES [1]

Pietiäinen M, Liljestrand JM, Kopra E, Pussinen PJ. Mediators between oral dysbiosis and cardiovascular diseases. > 2018. [http://dx.doi.org/10.1111/eos.12423]

[2]

Minty M, Canceil T, Serino M, Burcelin R, Tercé F, Blasco-Baque V. Oral microbiota-induced periodontitis: a new risk factor of metabolic diseases. Rev Endocr Metab Disord 2019; 20(4): 449-59. [http://dx.doi.org/10.1007/s11154-019-09526-8] [PMID: 31741266]

[3]

Pignatelli P, Fabietti G, Ricci A, Piattelli A, Curia MC. How Periodontal Disease and Presence of Nitric Oxide Reducing Oral Bacteria Can Affect Blood Pressure. Int J Mol Sci 2020; 21(20): 7538. [http://dx.doi.org/10.3390/ijms21207538] [PMID: 33066082]

[4]

Hyde ER, Luk B, Cron S, et al. Characterization of the rat oral microbiome and the effects of dietary nitrate. Free Radic Biol Med 2014; 77: 249-57. [http://dx.doi.org/10.1016/j.freeradbiomed.2014.09.017] [PMID: 25305639]

[5]

Doel JJ, Benjamin N, Hector MP, Rogers M, Allaker RP. Evaluation of bacterial nitrate reduction in the human oral cavity. Eur J Oral Sci 2005; 113(1): 14-9. [http://dx.doi.org/10.1111/j.1600-0722.2004.00184.x] [PMID: 15693824]

[6]

Jansson EÅ, Huang L, Malkey R, et al. A mammalian functional nitrate reductase that regulates nitrite

NO and Oral Microbiota

The Role of Nitric Oxide in Type 2 Diabetes 101

and nitric oxide homeostasis. Nat Chem Biol 2008; 4(7): 411-7. [http://dx.doi.org/10.1038/nchembio.92] [PMID: 18516050] [7]

Matsha TE, Prince Y, Davids S, et al. Oral Microbiome Signatures in Diabetes Mellitus and Periodontal Disease. J Dent Res 2020; 99(6): 658-65. [http://dx.doi.org/10.1177/0022034520913818] [PMID: 32298191]

[8]

Chen B, Wang Z, Wang J, et al. The oral microbiome profile and biomarker in Chinese type 2 diabetes mellitus patients. Endocrine 2020; 68(3): 564-72. [http://dx.doi.org/10.1007/s12020-020-02269-6] [PMID: 32246318]

[9]

Ohlrich EJ, Cullinan MP, Leichter JW. Diabetes, periodontitis, and the subgingival microbiota. J Oral Microbiol 2010; 2(1): 5818. [http://dx.doi.org/10.3402/jom.v2i0.5818] [PMID: 21523215]

[10]

Almeida-Santos A, Martins-Mendes D, Gayà-Vidal M, Pérez-Pardal L, Beja-Pereira A. Characterization of the Oral Microbiome of Medicated Type-2 Diabetes Patients. Front Microbiol 2021; 12: 610370. [http://dx.doi.org/10.3389/fmicb.2021.610370] [PMID: 33613481]

[11]

Graves DT, Corrêa JD, Silva TA. The Oral Microbiota Is Modified by Systemic Diseases. J Dent Res 2019; 98(2): 148-56. [http://dx.doi.org/10.1177/0022034518805739] [PMID: 30359170]

[12]

Bahadoran Z, Mirmiran P, Ghasemi A. Role of Nitric Oxide in Insulin Secretion and Glucose Metabolism. Trends Endocrinol Metab 2020; 31(2): 118-30. [http://dx.doi.org/10.1016/j.tem.2019.10.001] [PMID: 31690508]

[13]

Lundberg JO, Weitzberg E, Cole JA, Benjamin N. Nitrate, bacteria and human health. Nat Rev Microbiol 2004; 2(7): 593-602. [http://dx.doi.org/10.1038/nrmicro929] [PMID: 15197394]

[14]

Govoni M, Jansson EÅ, Weitzberg E, Lundberg JO. The increase in plasma nitrite after a dietary nitrate load is markedly attenuated by an antibacterial mouthwash. Nitric Oxide 2008; 19(4): 333-7. [http://dx.doi.org/10.1016/j.niox.2008.08.003] [PMID: 18793740]

[15]

Goh CE, Trinh P, Colombo PC, et al. Association Between Nitrate-Reducing Oral Bacteria and Cardiometabolic Outcomes: Results From ORIGINS. J Am Heart Assoc 2019; 8(23): e013324. [http://dx.doi.org/10.1161/JAHA.119.013324] [PMID: 31766976]

[16]

Kilian M, Chapple ILC, Hannig M, et al. The oral microbiome – an update for oral healthcare professionals. Br Dent J 2016; 221(10): 657-66. [http://dx.doi.org/10.1038/sj.bdj.2016.865] [PMID: 27857087]

[17]

Deo PN, Deshmukh R. Oral microbiome: Unveiling the fundamentals. J Oral Maxillofac Pathol 2019; 23(1): 122-8. [PMID: 31110428]

[18]

Tada A, Hanada N. Opportunistic respiratory pathogens in the oral cavity of the elderly. FEMS Immunol Med Microbiol 2010; 60(1): 1-17. [http://dx.doi.org/10.1111/j.1574-695X.2010.00709.x] [PMID: 20579096]

[19]

Lamont RJ, Koo H, Hajishengallis G. The oral microbiota: dynamic communities and host interactions. Nat Rev Microbiol 2018; 16(12): 745-59. [http://dx.doi.org/10.1038/s41579-018-0089-x] [PMID: 30301974]

[20]

Verma D, Garg PK, Dubey AK. Insights into the human oral microbiome. Arch Microbiol 2018; 200(4): 525-40. [http://dx.doi.org/10.1007/s00203-018-1505-3] [PMID: 29572583]

[21]

Dewhirst FE, Chen T, Izard J, et al. The human oral microbiome. J Bacteriol 2010; 192(19): 5002-17. [http://dx.doi.org/10.1128/JB.00542-10] [PMID: 20656903]

102 The Role of Nitric Oxide in Type 2 Diabetes

Bahadoran et al.

[22]

Gordon DF Jr, Gibbons RJ. Studies of the predominant cultivable micro-organisms from the human tongue. Arch Oral Biol 1966; 11(6): 627-32. [http://dx.doi.org/10.1016/0003-9969(66)90229-9] [PMID: 5225869]

[23]

Devine DA, Marsh PD, Meade J. Modulation of host responses by oral commensal bacteria. J Oral Microbiol 2015; 7(1): 26941. [http://dx.doi.org/10.3402/jom.v7.26941] [PMID: 25661061]

[24]

McLean JS. Advancements toward a systems level understanding of the human oral microbiome. Front Cell Infect Microbiol 2014; 4: 98. [http://dx.doi.org/10.3389/fcimb.2014.00098] [PMID: 25120956]

[25]

Arweiler NB, Netuschil L. The Oral Microbiota. Adv Exp Med Biol 2016; 902: 45-60. [http://dx.doi.org/10.1007/978-3-319-31248-4_4] [PMID: 27161350]

[26]

Takahashi N. Oral Microbiome Metabolism. J Dent Res 2015; 94(12): 1628-37. [http://dx.doi.org/10.1177/0022034515606045] [PMID: 26377570]

[27]

Bostanci N, Krog MC, Hugerth LW, et al. Dysbiosis of the Human Oral Microbiome During the Menstrual Cycle and Vulnerability to the External Exposures of Smoking and Dietary Sugar. Front Cell Infect Microbiol 2021; 11: 625229. [http://dx.doi.org/10.3389/fcimb.2021.625229] [PMID: 33816334]

[28]

Bryan NS, Petrosino JF. Nitrate-Reducing Oral Bacteria: Linking Oral and Systemic Health. In: Bryan NS, Loscalzo J, Eds. > Nitrite and Nitrate in Human Health and Disease. Cham: Springer International Publishing 2017; pp. 21-31. [http://dx.doi.org/10.1007/978-3-319-46189-2_3]

[29]

Duncan C, Dougall H, Johnston P, et al. Chemical generation of nitric oxide in the mouth from the enterosalivary circulation of dietary nitrate. Nat Med 1995; 1(6): 546-51. [http://dx.doi.org/10.1038/nm0695-546] [PMID: 7585121]

[30]

Li H, Thompson I, Carter P, et al. Salivary nitrate? an ecological factor in reducing oral acidity. Oral Microbiol Immunol 2007; 22(1): 67-71. [http://dx.doi.org/10.1111/j.1399-302X.2007.00313.x] [PMID: 17241173]

[31]

van Maanen JM, van Geel AA, Kleinjans JC. Modulation of nitrate-nitrite conversion in the oral cavity. Cancer Detect Prev 1996; 20(6): 590-6. [PMID: 8939344]

[32]

Schreiber F, Stief P, Gieseke A, et al. Denitrification in human dental plaque. BMC Biol 2010; 8(1): 24. [http://dx.doi.org/10.1186/1741-7007-8-24] [PMID: 20307293]

[33]

Tribble GD, Angelov N, Weltman R, et al. Frequency of Tongue Cleaning Impacts the Human Tongue Microbiome Composition and Enterosalivary Circulation of Nitrate. Front Cell Infect Microbiol 2019; 9(39): 39. [http://dx.doi.org/10.3389/fcimb.2019.00039] [PMID: 30881924]

[34]

Kapil V, Rathod KS, Khambata RS, et al. Sex differences in the nitrate-nitrite-NO• pathway: Role of oral nitrate-reducing bacteria. Free Radic Biol Med 2018; 126: 113-21. [http://dx.doi.org/10.1016/j.freeradbiomed.2018.07.010] [PMID: 30031863]

[35]

Li H, Duncan C, Townend J, et al. Nitrate-reducing bacteria on rat tongues. Appl Environ Microbiol 1997; 63(3): 924-30. [http://dx.doi.org/10.1128/aem.63.3.924-930.1997] [PMID: 9055411]

[36]

Lundberg JO, Govoni M. Inorganic nitrate is a possible source for systemic generation of nitric oxide. Free Radic Biol Med 2004; 37(3): 395-400. [http://dx.doi.org/10.1016/j.freeradbiomed.2004.04.027] [PMID: 15223073]

[37]

Qin L, Liu X, Sun Q, et al. Sialin ( SLC17A5 ) functions as a nitrate transporter in the plasma

NO and Oral Microbiota

The Role of Nitric Oxide in Type 2 Diabetes 103

membrane. Proc Natl Acad Sci USA 2012; 109(33): 13434-9. [http://dx.doi.org/10.1073/pnas.1116633109] [PMID: 22778404] [38]

Granli T, Dahl R, Brodin P, Bøckman OC. Nitrate and nitrite concentrations in human saliva: Variations with salivary flow-rate. Food Chem Toxicol 1989; 27(10): 675-80. [http://dx.doi.org/10.1016/0278-6915(89)90122-1] [PMID: 2606404]

[39]

Hyde ER, Andrade F, Vaksman Z, Parthasarathy K, Jiang H, Parthasarathy DK, et al. Metagenomic analysis of nitrate-reducing bacteria in the oral cavity: implications for nitric oxide homeostasis. > 2014. [http://dx.doi.org/10.1371/journal.pone.0088645]

[40]

Zaura E, Keijser BJF, Huse SM, Crielaard W. Defining the healthy “core microbiome” of oral microbial communities. BMC Microbiol 2009; 9(1): 259. [http://dx.doi.org/10.1186/1471-2180-9-259] [PMID: 20003481]

[41]

Human Microbiome Project Consortium. Structure, function and diversity of the healthy human microbiome. Nature 2012; 486(7402): 207-14. [http://dx.doi.org/10.1038/nature11234] [PMID: 22699609]

[42]

Burleigh MC, Liddle L, Monaghan C, et al. Salivary nitrite production is elevated in individuals with a higher abundance of oral nitrate-reducing bacteria. Free Radic Biol Med 2018; 120: 80-8. [http://dx.doi.org/10.1016/j.freeradbiomed.2018.03.023] [PMID: 29550328]

[43]

Vanhatalo A, Blackwell JR, L’Heureux JE, et al. Nitrate-responsive oral microbiome modulates nitric oxide homeostasis and blood pressure in humans. Free Radic Biol Med 2018; 124: 21-30. [http://dx.doi.org/10.1016/j.freeradbiomed.2018.05.078] [PMID: 29807159]

[44]

Liddle L, Burleigh MC, Monaghan C, et al. Variability in nitrate-reducing oral bacteria and nitric oxide metabolites in biological fluids following dietary nitrate administration: An assessment of the critical difference. Nitric Oxide 2019; 83: 1-10. [http://dx.doi.org/10.1016/j.niox.2018.12.003] [PMID: 30528912]

[45]

Vanhatalo A, L’Heureux JE, Kelly J, et al. Network analysis of nitrate-sensitive oral microbiome reveals interactions with cognitive function and cardiovascular health across dietary interventions. Redox Biol 2021; 41: 101933. [http://dx.doi.org/10.1016/j.redox.2021.101933] [PMID: 33721836]

[46]

Kapil V, Haydar SMA, Pearl V, Lundberg JO, Weitzberg E, Ahluwalia A. Physiological role for nitrate-reducing oral bacteria in blood pressure control. Free Radic Biol Med 2013; 55: 93-100. [http://dx.doi.org/10.1016/j.freeradbiomed.2012.11.013] [PMID: 23183324]

[47]

Petersson J, Carlström M, Schreiber O, et al. Gastroprotective and blood pressure lowering effects of dietary nitrate are abolished by an antiseptic mouthwash. Free Radic Biol Med 2009; 46(8): 1068-75. [http://dx.doi.org/10.1016/j.freeradbiomed.2009.01.011] [PMID: 19439233]

[48]

Webb AJ, Patel N, Loukogeorgakis S, Okorie M, Aboud Z, Misra S, et al. Acute blood pressure lowering, vasoprotective, and antiplatelet properties of dietary nitrate via bioconversion to nitrite. > 2008. [http://dx.doi.org/10.1161/HYPERTENSIONAHA.107.103523]

[49]

Sobko T, Reinders C, Norin E, Midtvedt T, Gustafsson LE, Lundberg JO. Gastrointestinal nitric oxide generation in germ-free and conventional rats. Am J Physiol Gastrointest Liver Physiol 2004; 287(5): G993-7. [http://dx.doi.org/10.1152/ajpgi.00203.2004] [PMID: 15256364]

[50]

McIlvenna LC, Monaghan C, Liddle L, et al. Beetroot juice versus chard gel: A pharmacokinetic and pharmacodynamic comparison of nitrate bioavailability. Nitric Oxide 2017; 64: 61-7. [http://dx.doi.org/10.1016/j.niox.2016.12.006] [PMID: 28042082]

[51]

Carlström M, Larsen FJ, Nyström T, et al. Dietary inorganic nitrate reverses features of metabolic syndrome in endothelial nitric oxide synthase-deficient mice. Proc Natl Acad Sci USA 2010; 107(41):

104 The Role of Nitric Oxide in Type 2 Diabetes

Bahadoran et al.

17716-20. [http://dx.doi.org/10.1073/pnas.1008872107] [PMID: 20876122] [52]

Wang RR, Xu YS, Ji MM, et al. Association of the oral microbiome with the progression of impaired fasting glucose in a Chinese elderly population. J Oral Microbiol 2019; 11(1): 1605789. [http://dx.doi.org/10.1080/20002297.2019.1605789] [PMID: 31069021]

[53]

Long J, Cai Q, Steinwandel M, et al. Association of oral microbiome with type 2 diabetes risk. J Periodontal Res 2017; 52(3): 636-43. [http://dx.doi.org/10.1111/jre.12432] [PMID: 28177125]

[54]

Xiao E, Mattos M, Vieira GHA, et al. Diabetes Enhances IL-17 Expression and Alters the Oral Microbiome to Increase Its Pathogenicity. Cell Host Microbe 2017; 22(1): 120-128.e4. [http://dx.doi.org/10.1016/j.chom.2017.06.014] [PMID: 28704648]

[55]

Blasco-Baque V, Garidou L, Pomié C, et al. Periodontitis induced by Porphyromonas gingivalis drives periodontal microbiota dysbiosis and insulin resistance via an impaired adaptive immune response. Gut 2017; 66(5): 872-85. [http://dx.doi.org/10.1136/gutjnl-2015-309897] [PMID: 26838600]

[56]

Blasco-Baque V, Kémoun P, Loubieres P, et al. [Impact of periodontal disease on arterial pressure in diabetic mice]. Ann Cardiol Angeiol (Paris) 2012; 61(3): 173-7. [http://dx.doi.org/10.1016/j.ancard.2012.04.012] [PMID: 22621847]

[57]

Sun X, Li M, Xia L, et al. Alteration of salivary microbiome in periodontitis with or without type-2 diabetes mellitus and metformin treatment. Sci Rep 2020; 10(1): 15363. [http://dx.doi.org/10.1038/s41598-020-72035-1] [PMID: 32958790]

[58]

Darveau RP, Tanner A, Page RC. The microbial challenge in periodontitis. Periodontol 2000 1997; 14(1): 12-32. [http://dx.doi.org/10.1111/j.1600-0757.1997.tb00190.x] [PMID: 9567964]

[59]

Hintao J, Teanpaisan R, Chongsuvivatwong V, Ratarasan C, Dahlen G. The microbiological profiles of saliva, supragingival and subgingival plaque and dental caries in adults with and without type 2 diabetes mellitus. Oral Microbiol Immunol 2007; 22(3): 175-81. [http://dx.doi.org/10.1111/j.1399-302X.2007.00341.x] [PMID: 17488443]

[60]

Soskolne WA, Klinger A. The relationship between periodontal diseases and diabetes: an overview. Ann Periodontol 2001; 6(1): 91-8. [http://dx.doi.org/10.1902/annals.2001.6.1.91] [PMID: 11887477]

[61]

Chang PC, Lim LP. Interrelationships of periodontitis and diabetes: A review of the current literature. J Dent Sci 2012; 7(3): 272-82. [http://dx.doi.org/10.1016/j.jds.2012.02.002]

[62]

Demmer RT, Jacobs DR Jr, Singh R, et al. Periodontal Bacteria and Prediabetes Prevalence in ORIGINS. J Dent Res 2015; 94(9_suppl) (Suppl.): 201S-11S. [http://dx.doi.org/10.1177/0022034515590369] [PMID: 26082387]

[63]

Taylor GW, Burt BA, Becker MP, et al. Severe periodontitis and risk for poor glycemic control in patients with non-insulin-dependent diabetes mellitus. J Periodontol 1996; 67(10s) (Suppl.): 1085-93. [http://dx.doi.org/10.1902/jop.1996.67.10s.1085]

[64]

Teeuw WJ, Gerdes VEA, Loos BG. Effect of periodontal treatment on glycemic control of diabetic patients: a systematic review and meta-analysis. Diabetes Care 2010; 33(2): 421-7. [http://dx.doi.org/10.2337/dc09-1378] [PMID: 20103557]

[65]

Simpson TC, Needleman I, Wild SH, Moles DR, Mills EJ. Treatment of periodontal disease for glycaemic control in people with diabetes. Cochrane Database Syst Rev 2010; (5): CD004714. [PMID: 20464734]

[66]

Si J, Lee C, Ko G. Oral Microbiota: Microbial Biomarkers of Metabolic Syndrome Independent of Host Genetic Factors. Front Cell Infect Microbiol 2017; 7: 516.

NO and Oral Microbiota

The Role of Nitric Oxide in Type 2 Diabetes 105

[http://dx.doi.org/10.3389/fcimb.2017.00516] [PMID: 29326886] [67]

Casarin RCV, Barbagallo A, Meulman T, et al. Subgingival biodiversity in subjects with uncontrolled type-2 diabetes and chronic periodontitis. J Periodontal Res 2013; 48(1): 30-6. [http://dx.doi.org/10.1111/j.1600-0765.2012.01498.x] [PMID: 22762355]

[68]

Campus G, Salem A, Uzzau S, Baldoni E, Tonolo G. Diabetes and periodontal disease: a case-control study. J Periodontol 2005; 76(3): 418-25. [http://dx.doi.org/10.1902/jop.2005.76.3.418] [PMID: 15857077]

[69]

Aemaimanan P, Amimanan P, Taweechaisupapong S. Quantification of key periodontal pathogens in insulin-dependent type 2 diabetic and non-diabetic patients with generalized chronic periodontitis. Anaerobe 2013; 22: 64-8. [http://dx.doi.org/10.1016/j.anaerobe.2013.06.010] [PMID: 23827459]

[70]

Ciantar M, Gilthorpe MS, Hurel SJ, Newman HN, Wilson M, Spratt DA. Capnocytophaga spp. in periodontitis patients manifesting diabetes mellitus. J Periodontol 2005; 76(2): 194-203. [http://dx.doi.org/10.1902/jop.2005.76.2.194] [PMID: 15974842]

[71]

Shillitoe E, Weinstock R, Kim T, et al. The oral microflora in obesity and type-2 diabetes. J Oral Microbiol 2012; 4(1): 19013. [http://dx.doi.org/10.3402/jom.v4i0.19013] [PMID: 23119124]

[72]

Blasco-Baque V, Serino M, Vergnes JN, et al. High-fat diet induces periodontitis in mice through lipopolysaccharides (LPS) receptor signaling: protective action of estrogens. PLoS One 2012; 7(11): e48220. [http://dx.doi.org/10.1371/journal.pone.0048220] [PMID: 23133617]

[73]

Wu YY, Xiao E, Graves DT. Diabetes mellitus related bone metabolism and periodontal disease. Int J Oral Sci 2015; 7(2): 63-72. [http://dx.doi.org/10.1038/ijos.2015.2] [PMID: 25857702]

[74]

Polak D, Shapira L. An update on the evidence for pathogenic mechanisms that may link periodontitis and diabetes. 2018; 150-66. [http://dx.doi.org/10.1111/jcpe.12803]

[75]

Zhao L, Cao L, Zhao TY, et al. Cardiovascular events in hyperuricemia population and a cardiovascular benefit-risk assessment of urate-lowering therapies: a systematic review and metaanalysis. Chin Med J (Engl) 2020; 133(8): 982-93. [http://dx.doi.org/10.1097/CM9.0000000000000682] [PMID: 32106120]

[76]

Arimatsu K, Yamada H, Miyazawa H, et al. Oral pathobiont induces systemic inflammation and metabolic changes associated with alteration of gut microbiota. Sci Rep 2014; 4(1): 4828. [http://dx.doi.org/10.1038/srep04828] [PMID: 24797416]

[77]

Ilievski V, Kinchen JM, Prabhu R, et al. Experimental Periodontitis Results in Prediabetes and Metabolic Alterations in Brain, Liver and Heart: Global Untargeted Metabolomic Analyses. J Oral Biol (Northborough) 2016; 3(1) [PMID: 27390783]

[78]

Ishikawa M, Yoshida K, Okamura H, et al. Oral Porphyromonas gingivalis translocates to the liver and regulates hepatic glycogen synthesis through the Akt/GSK-3β signaling pathway. Biochim Biophys Acta Mol Basis Dis 2013; 1832(12): 2035-43. [http://dx.doi.org/10.1016/j.bbadis.2013.07.012] [PMID: 23899607]

[79]

Watanabe K, Katagiri S, Takahashi H, et al. Porphyromonas gingivalis impairs glucose uptake in skeletal muscle associated with altering gut microbiota. FASEB J 2021; 35(2): e21171. [http://dx.doi.org/10.1096/fj.202001158R] [PMID: 33197074]

[80]

Kawamura N, Ohnuki Y, Matsuo I, et al. Effects of chronic Porphyromonas gingivalis lipopolysaccharide infusion on skeletal muscles in mice. J Physiol Sci 2019; 69(3): 503-11. [http://dx.doi.org/10.1007/s12576-019-00670-z] [PMID: 30848475]

106 The Role of Nitric Oxide in Type 2 Diabetes

Bahadoran et al.

[81]

Ilievski V, Bhat UG, Suleiman-Ata S, et al. Oral application of a periodontal pathogen impacts SerpinE1 expression and pancreatic islet architecture in prediabetes. J Periodontal Res 2017; 52(6): e12474. [http://dx.doi.org/10.1111/jre.12474] [PMID: 28643938]

[82]

Ilievski V, Toth PT, Valyi-Nagy K, et al. Identification of a periodontal pathogen and bihormonal cells in pancreatic islets of humans and a mouse model of periodontitis. Sci Rep 2020; 10(1): 9976. [http://dx.doi.org/10.1038/s41598-020-65828-x] [PMID: 32561770]

[83]

Bhat UG, Ilievski V, Unterman TG, Watanabe K. Porphyromonas gingivalis lipopolysaccharide upregulates insulin secretion from pancreatic β cell line MIN6. J Periodontol 2014; 85(11): 1629-36. [http://dx.doi.org/10.1902/jop.2014.140070] [PMID: 24921432]

[84]

Bahadoran Z, Mirmiran P, Carlström M, Norouzirad R, Jeddi S, Azizi F, et al. Different Pharmacokinetic Response to an Acute Dose of Inorganic Nitrate in Patients with Type 2 Diabetes. Endocr Metab Immune Disord Drug Targets 2020.

[85]

Zhang Y, Zhang H. Microbiota associated with type 2 diabetes and its related complications. Food Sci Hum Wellness 2013; 2(3-4): 167-72. [http://dx.doi.org/10.1016/j.fshw.2013.09.002]

[86]

Kageyama S, Takeshita T, Furuta M, Tomioka M, Asakawa M, Suma S, et al. Relationships of variations in the tongue microbiota and pneumonia mortality in nursing home residents. > The Journals of Gerontology: Series A 2018; 1097.1102 [http://dx.doi.org/10.1093/gerona/glx205]

[87]

Velmurugan S, Gan JM, Rathod KS, et al. Dietary nitrate improves vascular function in patients with hypercholesterolemia: a randomized, double-blind, placebo-controlled study. Am J Clin Nutr 2016; 103(1): 25-38. [http://dx.doi.org/10.3945/ajcn.115.116244] [PMID: 26607938]

[88]

Burleigh MC, Sculthorpe N, Henriquez FL, Easton C. Nitrate-rich beetroot juice offsets salivary acidity following carbohydrate ingestion before and after endurance exercise in healthy male runners. > 2020. [http://dx.doi.org/10.1371/journal.pone.0243755]

[89]

Hohensinn B, Haselgrübler R, Müller U, et al. Sustaining elevated levels of nitrite in the oral cavity through consumption of nitrate-rich beetroot juice in young healthy adults reduces salivary pH. Nitric Oxide 2016; 60: 10-5. [http://dx.doi.org/10.1016/j.niox.2016.08.006] [PMID: 27593618]

[90]

Radcliffe CE, Akram NC, Hurrell F, Drucker DB. Effects of nitrite and nitrate on the growth and acidogenicity of Streptococcus mutans. J Dent 2002; 30(7-8): 325-31. [http://dx.doi.org/10.1016/S0300-5712(02)00046-5] [PMID: 12554114]

[91]

Bahadoran Z, Mirmiran P, Carlström M, Ghasemi A. Inorganic nitrate: A potential prebiotic for oral microbiota dysbiosis associated with type 2 diabetes. Nitric Oxide 2021; 116: 38-46. [http://dx.doi.org/10.1016/j.niox.2021.09.001] [PMID: 34506950]

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CHAPTER 6

Nitric Oxide and Type 2 Diabetes: Lessons from Genetic Studies Zahra Bahadoran1, Parvin Mirmiran2, Mattias Carlström3 and Asghar Ghasemi4,* Nutrition and Endocrine Research Center, Research Institute for Endocrine Sciences, Shahid Beheshti University of Medical Sciences, Tehran, Iran 2 Department of Clinical Nutrition and Human Dietetics, Faculty of Nutrition Sciences and Food Technology, National Nutrition and Food Technology Research Institute, Shahid Beheshti University of Medical Sciences, Tehran, Iran 3 Department of Physiology and Pharmacology, Karolinska Institute, Stockholm, Sweden 4 Endocrine Physiology Research Center, Research Institute for Endocrine Sciences, Shahid Beheshti University of Medical Sciences, Tehran, Iran 1

Abstract: Nitric oxide (NO), a multifunctional gasotransmitter, is now considered an endocrine hormone that essentially contributes to the regulation of glucose and insulin homeostasis. Here, we discuss current genetic data linking NO metabolism to metabolic disorders, especially insulin resistance and type 2 diabetes (T2D). Although several gene variants of NO synthases [NOSs, i.e., neuronal NOS (nNOS), endothelial NOS (eNOS), and inducible NOS (iNOS)] isoforms have been identified in humans that affect NO bioactivity and metabolism, only the eNOS polymorphisms are reported to be associated with insulin resistance and T2D. Among the functional eNOS gene polymorphisms, the single nucleotide polymorphisms (SNPs) rs2070744 (T786C), rs1799983 (G894T), and rs869109213 (eNOS 4b/4a) are related to the risk of developing insulin resistance and T2D.

Keywords: Endothelial Nitric Oxide Synthase, Gene Polymorphisms, Inducible Nitric Oxide Synthase, Insulin Resistance, Neuronal Nitric Oxide Synthase, Nitric Oxide, Type 2 Diabetes. INTRODUCTION Emerging data suggest that impaired nitric oxide (NO) homeostasis is involved in the development of insulin resistance and type 2 diabetes (T2D) [1, 2]. The Corresponding author Asghar Ghasemi: Endocrine Physiology Research Center, Research Institute for Endocrine Sciences, Shahid Beheshti University of Medical Sciences, Tehran, Iran; No. 24, Erabi Street, Velenjak, Tehran, Iran; Phone: +98 21 22409309; Fax: +98 21 22416264, Email: [email protected]

*

Asghar Ghasemi, Khosrow Kashfi, Zahra Bahadoran (Eds.) All rights reserved-© 2022 Bentham Science Publishers

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critical role of NO on glucose and insulin homeostasis is greatly supported by findings of the genetically-modified animal models, including NO synthase (NOS) gene knockout models or over-expressed NOSs [3 - 5]. Extrapolation of the results obtained in the genetically-modified NOS isoforms in the animal models to humans is not straightforward; however, studies that investigated gene polymorphisms of human NOSs confirm the relation between NO metabolism and the development of insulin resistance and T2D. Among several reports on NOS gene polymorphisms, endothelial NOS (eNOS) gene variants have gained enormous attention due to their association with hypertension and cardiovascular diseases; a meta-analysis of 155 published studies showed that the most common eNOS polymorphisms, i.e., rs1799983 (G894T), rs2070744 (T786C), and rs869109213 (eNOS 4b/4a) are significantly associated with coronary artery disease in the general populations [6]. Another meta-analysis of 74 studies showed that the eNOS polymorphisms G894T and T786C increase the risk of hypertension by about 16-40% among different populations [7]. The genetic variants of eNOS that have formerly been reported for individual susceptibility to vascular dysfunction and hypertension [8] are now considered the risk factors for insulin resistance and T2D [9 - 12]. These functional eNOS polymorphisms affect gene expression or protein structure of eNOS, resulting in inadequate eNOS-derived NO production and impaired glucose and insulin homeostasis [9]. Here, we review genetic evidence linking NO metabolism to metabolic disorders, especially insulin resistance and T2D. A BRIEF OVERVIEW OF NOS ENZYMES: GENE STRUCTURE AND CHROMOSOMAL LOCALIZATION The enzymatic NO synthesis pathway is mediated by NO synthase (NOS), in which L-arginine is converted to NO by constitutive or inducible isoforms of NOSs, including eNOS (EC 1.14.13.39), neuronal NOS (nNOS, EC 1.14.13.39), and inducible NOS (iNOS, EC 1.14.13.39) [13, 14]. The NOSs are flavoheme homodimer enzymes (with two functional domains in each monomer: oxygenase and reductase domains), which catalyze the formation of NO through two consecutive monooxygenation reactions [14, 15]; calmodulin (CaM)-binding region in the middle of the molecule, has been called the third NOSs domain in some papers [16]. Both nNOS and eNOS are activated by the reversible binding of CaM at elevated intracellular Ca2+ levels; CaM binds to the linker region between the reductase and oxygenase domains and activates the enzyme by inducing intramolecular electron transfer [17]. The main characteristics of NOS isoforms are summarized in Table 1. In addition, a number

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The Role of Nitric Oxide in Type 2 Diabetes 109

of splice variants (nNOSµ, nNOSβ, and nNOSδ) are translated from the nNOS gene [18]. The human eNOS gene is located in the 7q36.1 region of chromosome 7 and comprises 28 exons (https://www.ncbi.nlm.nih.gov/gene/4846). The human eNOS gene has a length of 21-22 kb and encodes an mRNA of 4052 nucleotides [19]. The eNOS promoter region is TATA-less, includes Sp1 and GATA motifs, and has several binding sites for transcription factors, i.e., activator proteins (AP-1 and AP-2), nuclear factors [nuclear factor-1 (NF-1), interleukin-6 (IL-6), nuclear factor κB (NF-κB)], Ets protein polyomavirus enhancer activator 3 (PEA3), 1 myc-associated zine-finger protein (MAZ), 1 Ying Yang (YY1), acute-phase response elements, shear-stress response elements, and sterol regulatory elements [20 - 22]. The eNOS promoter sequence also contains several half-sites of the estrogen- and glucocorticoid-responsive elements [21]. Mutation of the Sp1 site decreased human eNOS promoter activity by about 85%, whereas deletion of the GATA binding site completely inactive eNOS promoter [23]. Table 1. Characteristics of NOS isoforms. NOS Isoforms Constitutive

Inducible

nNOS (NOS1)

eNOS (NOS3)

iNOS (NOS2)

Brain

Endothelial cells

Macrophages in the liver, kidney, and lung

Red blood cells, alveolar macrophages, placenta, kidney tubular epithelial cells

Cytokine-induced cells

Physiological functions [27]

Learning and memory processes, regulation of systemic blood pressure, renal autoregulation, and local cerebral blood flow

Regulation of vascular tone

Implicated in immune defense, antitumor and antimicrobial activities

Cellular localization [27]

Cytoplasm, mitochondria, and plasma membrane

Plasma membrane caveolae and cytoplasm

Cytoplasm

Human locus (Gene ID) [25]

4842

4846

4843

Main sites of expression [24]

Spinal cord, sympathetic ganglia, and adrenal glands, peripheral nitrergic nerves, Other sites of epithelial cells, pancreatic expression [24 - 26] islet cells, cardiac and skeletal myocytes, smooth muscle cells, renal macula densa cells

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(Table 1) cont.....

NOS Isoforms Constitutive

Inducible

nNOS (NOS1)

eNOS (NOS3)

iNOS (NOS2)

Chromosomal location

The 12q24.2 region of chromosome 12

The 7q36.1 region of chromosome 7

The 17q11.2 region of chromosome 17

Gene size [19]

> 200 kbp

21-22 kbp

37 kbp

Molecular size (kDa) [24]

150-160

133

130

Number of amino acids [28]

1434

1203

1153

Km for L-arg (µM) [29, 30]

1.4-2.2

2.9

2.8-32.3

O2-dependency (Km as µM) [14]

350

4

130

Kr (S-1) [14]

3-4

0.1

0.9-1.5

-1

Kd (S ) [14]

5

3

2

-1

Kox (S ) [14]

0.2

0.6

3

Physiological inhibitors [31]

ADMA, L-NMMA

ADMA, L-NMMA

ADMA, L-NMMA

Mechanism of activation [27, 30, 32 - 34]

Ca2+/calmodulin-dependent†

Ca2+/calmodulin-dependent‡ ; Ca2+-independent (e.g., shear stress-induced tyrosine phosphorylation)

Ca2+-independent (e.g. cytokines-dependent)

Amount of NO production [27]

Small (~nM)

Small (~nM)

Large (~µM)

† Inactive at 100 nM Ca2+ and fully active at 500 nM [24] (half-maximal activity between 200 and 400 nM of Ca2+ concentration) ‡ Activated by Ca2+ in the range of 100-500 nM [24] L-arg, L-arginine; ADMA, asymmetric dimethylarginine; L-NMMA, monomethyl L-arginine Kr, rate of ferric heme reduction; Kd, dissociation rate of the ferric heme-NO complex. Kox, rate of reaction between the ferrous heme-NO complex and O2

Among eNOS promoter binding sites, Sp1, Sp3, and YY1 have been reported to positively regulate human eNOS promoter activity, while MAZ inhibits the eNOS promoter [35]. Beyond these regulatory regions of the eNOS gene promoter, a sequence including 269 nucleotides at positions -4907 to -4638 upstream of the transcription start site acts as an enhancer of eNOS expression in the endothelial cells [36]. The human nNOS gene is localized on the 12q24.2 region of chromosome 12. The nNOS gene comprises 33 coding exons distributed over 240-kb genomic

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The Role of Nitric Oxide in Type 2 Diabetes 111

DNA [37]. In healthy humans, the nNOS is highly expressed in the brain [mean Reads Per Kilobase gene model per Million total reads (RPKM)=1.11±0.49], kidney (mean RPKM=0.95±0.22), salivary glands (mean RPKM=0.72±0.18), skin (mean RPKM=0.67±0.22), lung (mean RPKM= 0.57±0.38), and prostate (mean RPKM= 0.57±0.57) [38]. The classical nNOS isoform (nNOSα), the exon 2containing form, is predominantly expressed in the neuronal cells [37]. The other nNOS isoforms, i.e., nNOSβ and nNOSμ, are produced by alternative splicing that skips exon 2 and has different first exons, i.e., exon 1a and 1b [39]; both of these variants lack the PSD-95/discs large/ZO-1 homology domain (PDZ) domain located in the exon 2 [37]. The human iNOS gene is localized on the 17q11.2 region of chromosome 17, has a length of approximately 37 kb, and comprises 26 exons and 25 introns [40]. Updated reports establish 27 exons for the iNOS gene (https://www.ncbi. nlm.nih.gov/gene/4843), in which exons 1-13 are responsible for encoding the oxygenase domain, and exons 14-27 encode for the reductase domain of iNOS [41]. The transcription start site is located in exon 2, and the stop codon is located in exon 27. In healthy humans, the iNOS is highly expressed in the small intestine (mean RPKM= 10.2±12.2), appendix (mean RPKM=7.9±3.1), duodenum (mean RPKM=5.3±0.74), urinary bladder (mean RPKM=3.2±2.8), and colon (mean RPKM= 2.39±1.36) [38]. Genetically-Modified NOS Enzymes and Impaired Glucose and Insulin Homeostasis Genetic approaches, including knockout or overexpressed eNOS animal models, have helped explain NO's role in the development of insulin resistance. A clustering of disrupted features of glucose and insulin metabolism has been reported in both complete (eNOS-/-) [4, 42 - 44] and partial (eNOS+/-) eNOSdeficient mice [45, 46], whereas genetically-modified eNOS overexpressed models were resistant to chemically- and high-fat diet (HFD)-induced hyperinsulinemia [47, 48]; nNOS disruption in mice impairs glucose metabolism and insulin resistance [3 - 5]. Table 2 shows carbohydrate metabolism in the animal models of the genetically-modified NOS isoforms. Overexpression of iNOS in the skeletal muscle induces insulin resistance by Snitrosation of proteins involved in the early steps of the insulin signal transduction pathway, including insulin receptor, insulin receptor substrate-1 (IRS-1), and protein kinase B [49]. Following exposure to HFD, iNOS-deficient mice, compared to wild-type ones, displayed normal glucose tolerance, insulin sensitivity, and insulin-stimulated glucose uptake in the skeletal muscle [50]. Overexpression of iNOS, using a liver-specific iNOS transgenic model, was

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associated with hepatic insulin resistance, hyperglycemia, and hyperinsulinemia [51]. Finally, findings obtained from the triple NOSs knockout mouse demonstrate the importance of NOS in the regulation of cardiovascular, metabolic, and renal functions [52]. Tsutsui and colleagues showed that these mice exhibited several features of cardiovascular disease, including hypertension, arteriosclerosis, cardiac hypertrophy, and myocardial infarction, with reduced lifespan. The triple knockout mice displayed all features of metabolic syndrome, and when fed with an HFD diet, they developed severe dyslipidemia. Moreover, these NOS-deficient mice also displayed profound renal, lung, and bone abnormalities [52]. Table 2. Carbohydrate metabolism in the genetically-modified NOS isoforms animal models. Model

Fasting Glucose

Fasting Insulin

Insulin Sensitivity

Glucose Tolerance

eNOS-/- and nNOS-/- mice‡ [4]

↔

↔

↓*

NR

eNOS female mice [42]

↔

↑

↓*

NR

↑

↓*

↓†

-/-

eNOS female mice [43] -/-

eNOS female mice exposed to HFD [45]

↔

↑

↔

NR

eNOS-/- male mice [5]

NR

NR

NR

↓

eNOS female mice [44]

↑

NR

NR

↓

eNOS compared to overexpressed DDAH-1 female mice [53]

↑

↑

NR

NR

iNOS overexpressed transgenic female mice [51]

↑

↑

↓

↓

n/i/eNOS-/- male mice [5]

NR

NR

NR

↓

+/-

-/-

-/-

eNOS overexpressed transgenic Lower average blood glucose concentration compared to WT male mice exposed to STZ or ALX Lower incidence of diabetes compared to WT; increased survival [48] eNOS-/- male mice exposed to STZ Higher average blood glucose concentration compared to WT or ALX [48] Higher incidence of diabetes compared to WT; decreased survival iNOS-/- mice with lipid-induced insulin resistance [54]

Normal insulin sensitivity and insulin-stimulated glucose uptake in the skeletal muscles compared to WT

iNOS-/- mice exposed to HFD [50]

Normal glucose tolerance, insulin sensitivity, and insulin-stimulated glucose uptake in skeletal muscles compared to WT

* By euglycemic hyperinsulinemic clamp study † Following metabolic stress (i.e., HFD) ‡ Sex not indicated ALX, alloxan; DDAH, dimethylarginine dimethylaminohydrolase-1; HFD, high-fat diet; insulin resistance, insulin resistance; NOx, nitrate+nitrite; NR, not reported; STZ, streptozotocin; WT, wild type

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Common Polymorphisms of NOS Enzymes Although gene variants of all NOS isoforms have been reported in humans, only the eNOS polymorphisms are reported to be associated with IR and T2D. Here, we first briefly overview the well-known polymorphisms of nNOS and iNOS, and then common polymorphisms of eNOS will be discussed in more detail. Common Polymorphisms of nNOS and iNOS A functional single nucleotide polymorphism (SNP) has been characterized in the promoter region of the first exon in nNOS, ex1c-SNP rs41279104; the polymorphism has been reported to be related to schizophrenia, infantile hypertrophic pyloric stenosis, verbal intelligence, and working memory performance [55 - 57]. The rs41279104 occurs in a putative regulatory region of nNOS and reduces nNOS expression by approximately 30% [57]. Other variants, including 3 microsatellites, i.e., an intronic AAT repeat of unclear significance, a CA repeat in the 3′ UTR of exon 29 (influences nNOS mRNA processing), and a highly polymorphic CA repeat 33 bp upstream of the TATA box of exon 1f (nNOS1 ex1f-VNTR), have also been reported in humans [58]. A number of nNOS polymorphisms, including SNPs rs3782218, rs11068447, rs7295972, rs2293052, rs12829185, rs1047735, rs3741475, rs2682826, rs2072324, rs944725, rs12944039, rs2248814, rs2297516, rs1060826, and rs2255929 are related to Parkinson's disease [59]. There is currently no evidence linking human nNOS polymorphisms and the risk of cardiometabolic disorders, including T2D and insulin resistance. The iNOS gene polymorphisms are determined in both coding regions and regulatory regions (e.g., promoter) [41]; those that occur in the coding region may affect the activity of the enzyme, whereas polymorphisms in the promoter region are related to levels of the enzyme produced [41]. In the human iNOS promoter region, three polymorphisms were reported, including an SNP G⁄C at position 954 and two microsatellite repeats, i.e., a biallelic tetranucleotide repeat sequence (TAAA)n and a highly polymorphic (nine alleles) pentanucleotide (CCTTT)n repeat [41]. The most well-known polymorphisms of the coding region are those related to inflammatory bowel disease (i.e., rs2297518 and rs1137933) [60, 61] and Parkinson’s disease (i.e., rs2072324, rs944725, rs12944039, rs2248814, rs2297516, rs1060826, and rs2255929) [59]; all of these polymorphisms affect the activity of the iNOS and the levels of produced NO. An iNOS C/T polymorphism, occurring within exon 16 of the reductase domain, has been associated with increased susceptibility to the risk of gastric cancer [62]. Other iNOS polymorphisms are characterized in diabetic retinopathy (pentanucleotide repeat sequence CCTTTn at promoter region) [63], malaria

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(pentanucleotide repeat sequence CCTTTn, -954 G/C and -1170 C/T at promoter region) [64, 65], and rheumatoid arthritis (pentanucleotide repeat sequence CCTTTn, tetranucleotide repeat sequence TAAAn, -954 G/C and -786 T/C polymorphism at promoter region) [66, 67]. Common Polymorphisms of eNOS Several polymorphisms have been characterized in the eNOS gene, i.e., SNPs, variable number of tandem repeats (VNTRs), microsatellites, and insertions/deletions [20]; some of these polymorphisms functionally affect the eNOS gene expression or activity and therefore modulate endogenous NO synthesis [20]. These polymorphisms affect the regulation of the eNOS gene expression at the transcriptional, post-transcriptional, and post-translational levels [20]. The common clinically relevant polymorphisms of eNOS, i.e., an SNP in exon 7 (G894T, rs1799983, Glu298Asp), an SNP in the promoter region (T786C, rs2070744), an SNP in intron 18 (IVS18-27A→C), and a VNTR in intron 4 (eNOS 4b4a, rs869109213), have been reported to be associated with the risk of cardiometabolic diseases [9 - 12, 68, 69]. Although these polymorphisms identified in the eNOS gene are all functional, the G894T polymorphism is the only variation leading to amino acid substitution in the final version of the protein [70]. The G894T polymorphism is located at exon 7 of the eNOS gene; in this SNP, the substitution of guanine residue (G base) at position 894 by thymine residue (T base) at the codon 298 results in the glutamate (Glu) to be replaced by the aspartate (Asp), at the corresponding amino acid sequence (Glutamate-GAG to Aspartate-GAT) [8]. The amino acid Asp in the mutated eNOS protein is targeted by selective proteolytic cleavage in vascular endothelium, resulting in decreased bioactivity of eNOS and diminished NO synthesis [71, 72]. Since G894T eNOS polymorphism occurs in the active region of the enzyme, in which the substrate L-arginine and the cofactors heme and tetrahydrobiopterin (BH4) bind to the enzyme, the G894T can partially change the structure of the protein, leading to its diminished activity, by affecting its ability to bind to substrates and possibly by eNOS uncoupling [73]. Epidemiologic studies have described the genotype distribution of eNOS G894T polymorphism, and a different prevalence of the polymorphism has been reported among different populations; the GG genotype (57-70%) seems to be more common than the GT (22.9%) and TT (7.1%) genotypes among the African population [74]. In the black African population, including the South African (GG=78.6%, GT=19.0%, and TT=2.4%) [75], and African Americans

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(GG=70.4%, GT=23.9%, and TT=5.6%) [76], the wild-type GG genotype is predominant. In Egypt, the genotype distribution of eNOS G894T polymorphism is 58.4% GG, 33.7% GT, and 7.9% TT [77]; the frequency of the G and T were 75.3% and 24.7%, respectively [77]. GG genotype is also predominant among the Asian populations; distribution of the polymorphism G894T of the eNOS gene in Korea (GG=97.6%, GT=19.5%, and TT=0.9%), Japan (GG=84.4%, GT=17.4%, and TT=0.0%), and India (GG=74.3%, GT=25.7%, and TT= 0%) shows a relatively rare TT genotype [78, 79]. In an Asian population, the genotypes frequency of eNOS G894T was reported as 57%, 37% and 6% for GG, GT, and TT, respectively [80]. Among the European populations, frequency of GG genotype is lower than the other populations and range from 40% to 50% (Germany: GG=50.5%, GT=40%, and TT=9.5%; UK: GG=47.8%, GT=42%, and TT=10.2%; European HapMap-CEU study: GG= 40.0%, GT=51.7%, and TT=8.3%) [70, 81]. The G and T allele frequencies in these studies were reported as 65.8-71.1% and 29.0-34.2%, respectively. In the Turkish population, the genotype frequencies of eNOS Glu298Asp polymorphism (GG=49.3%, GT=41.3%, and TT=9.3%) seem to be similar to the European population [82]. Despite a lower frequency, the T allele for the G894T polymorphism of the eNOS gene has a greater risk of developing cardiometabolic diseases than the G allele [83]. The T786C variant of the eNOS gene is located in the upstream position -786; the eNOS T786C polymorphism (rs2070744) occurs by a single mutation of thymine residue (T base) to cytosine residue (C base) that affects eNOS protein levels and enzymatic activity [84]. The frequencies of the eNOS T786C genotypes, i.e., TT, TC, and CC, were reported to be 76%, 23%, and 1%, respectively [85]. Among European populations, genotype distribution of T786C was reported as CC=17.7%, CT=40.4%, and TT=41.9% [86]. African Americans were reported to carry 73.1%, 23.9%, and 3.0% TT, TC, and CC of the eNOS T786C polymorphism [76]. In an Asian population, eNOS T786C genotypes, i.e. TT, TC, and CC were reported 56%, 37% and 7%, respectively [87]. The 4b4a variants of the eNOS gene include a allele (5 tandem 27-bp repeats) and b allele (4 tandem 27-bp repeats) [88]. The frequency of the b allele was reported as 89.8%, and the frequency of the a allele was reported as 10.2% [71]. The frequencies of genotypes of the eNOS4b4a, i.e., aa, ab and bb genotypes, were determined as 1%, 23%, and 76% in a group of healthy children [88]. Although the distribution of eNOS 4a4b genotypes differs among races, the frequencies of the aa, ab, and bb genotypes were reported with a prevalent bb genotype [Japanese: aa= 1%, ab=18%, and bb=81% [89], aa= 1.4%, ab=19%, and bb=79.6% [90], aa= 1.7%, ab=16.9%, and bb=81.4% [71]; Australian Caucasians aa= 1%, ab=32%, and

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bb=67% [91], Germans: aa= 2.4%, ab=27%, and bb=70% [92]; Turkish: aa= 0.6%, ab=18.0%, and bb=81.4% [93]; African Americans: aa= 5.6%, ab=23.9%, and bb=70.4% [76]. The eNOS Polymorphisms and Serum NO Metabolites Serum concentrations of the NO metabolites (often referred to as NOx, which is the sum of nitrite and nitrate) across the genotypes of the eNOS Glu298Asp polymorphism have shown no considerable difference. However, the TT genotype seems to be related to a higher serum NOx. In a group of the healthy adult Egyptian population, serum NOx concentration was reported as 29.5±1.8, 30.6±2.4, and 34.8±5.0 µM in the subjects with GG, GT, and TT genotypes, respectively [77]. Similarly, higher serum NOx concentrations were observed among subjects who carried TT genotype compared to those who carried GG or GT (36.2±13.9 vs. 30.2±14.1 and 29.1±10.5 µM) [82]. In contrast, serum NOx concentrations and NOS activity were significantly lower in subjects with TT genotype than those with GG and GT genotypes for the eNOS G298T [94]. Serum NOx concentrations were 18.1±3.6, 37.3±5.4, and 40.6±4.8 µM in TT, GT, and GG genotypes, respectively. These levels correlated with their serum NOS activity, which was 54.2±4.3, 86.8±6.4, and 90.4±5.8 U/mL in TT, GT, and GG genotypes, respectively [94]. In a group of healthy Venezuelans, no significant differences in the urinary excretion of NO metabolites were reported between the GG and the GT+TT groups (978±103 vs. 938±108 µmol/day), while the 4a/b genotype was associated with a 25% decreased levels of NO metabolites [95]. In the 4b4a VNTR polymorphism, predominant genotypes eNOS4 aa and eNOS ab were related to a significantly lower serum NOx than the eNOS4 bb genotype (31.2±2.00 vs. 35.5±0.93 µM) [71]. The eNOS Polymorphisms and Development of Insulin Resistance The genotype frequency distributions of the eNOS polymorphism G894T were 77.6% GG, 17.4% GT, and 5.0% TT in patients with insulin resistance, which were significantly more frequent than in the control group (47.2% GG, 40.4% GT, and 12.4% TT) [96]. Compared to controls, the median (inter-quartile range, IQR) of homeostasis model assessment of insulin resistance (HOMA-IR) was significantly higher in subjects with GG, GT, and TT genotypes of eNOS G894T polymorphism (median=19.6 vs. 1.16 in GG, 19.2 vs. 1.07 in GT and 18.3 vs. 0.95 in TT) [96]. The TT genotype of eNOS polymorphism contributed to the occurrence of insulin resistance by 5% (crude OR=0.24, 95% CI=0.10-0.58, P=0.001; adjusted

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OR=0.13, 95% CI=0.01-2.11, P=0.091); GT/TT genotypes contributed to the occurrence of IR by 22.4% (crude OR=0.26, 95% CI=0.16-0.42, P=0.001; adjusted OR=0.29, 95% CI=0.08-1.01, P=0.038) [96]. A significant association was also observed between haplotypes at the eNOS locus (i.e., the Exon7 and IVS18+loci and T2D, in a Caucasian population [11]. In this study, normalglycemic subjects homozygous for both D298 and IVS18+27C had higher levels of insulin, C-peptide, and NO and higher HOMA-IR values compared with those to have the double wild-type homozygotes; these characteristics are related to prediabetes state, in which hyperinsulinemia and/or insulin resistance precedes the development of T2D [11]. The eNOS Polymorphisms and Development of T2D Although many studies have investigated the possible link between T2D and the eNOS gene polymorphisms, the results are controversial. In a group of the south Indian population, the chance of having T2D was 7.2-fold higher (OR=7.2, 95% CI=4.1-12.7) among subjects who carried mutant genotypes GT and TT compared to those who carried wild type (GG genotype) for eNOS G894T polymorphism [97]. In contrast, the prevalence of T2D in the GG compared to the GT genotype of eNOS G894T polymorphism was reported to be similar (33 vs. 31%) in patients with acute myocardial infarction [90]. In a group of Egyptian patients with T2D, no significant difference was observed in distribution of eNOS T786C polymorphism between patients and controls (TT = 24.0 vs. 33.0%, TC= 76.0 vs. 67.0% in T2D and control subjects, respectively), while TT genotype of eNOS G894T was more frequent in patients with T2D (GG= 61.0 vs. 46.0%, GT= 32.0 vs. 52.0%, and TT=7.0 vs. 2.0% in T2D and control subjects, respectively, P=0.001) [9]. Carrying a allele in 4b4a VNTR and T allele in G894T might be related to an elevated risk of T2D by 38% and 22% (OR=1.38, 95% CI=1.16-1.64, and OR=1.22, 95R CI=1.06-1.41) [98]. A meta-analysis (including 19 studies involving 8009 subjects for 4b4a VNTR and 19 studies involving 8600 subjects for G894T), assessed the association between eNOS gene polymorphisms and the risk of T2D, reported that the dominant models of polymorphisms of 4b4a VNTR (i.e., aa+ab vs. bb genotypes) and G894T (i.e., TT+GT vs. GG genotypes) were significantly related to increased risk of T2D by 34% (pooled estimated OR=1.34, 95% CI=1.15-1.57) and 25% (pooled estimated OR=1.25, 95% CI=1.06-1.48) [98]; these values were greater among Asian population (pooled estimated OR=1.40, 95% CI=1.09-1.79 and pooled estimated OR=1.49, 95% CI=1.08-2.05) [98]. In recessive models (aa vs. ab+bb for 4b4a VNTR and TT vs. GT +GG for G894T), the risk of T2D was 1.84 (95% CI=1.09-3.09) and 1.36 (95% CI=1.05-1.74), respectively [98].

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The eNOS Polymorphisms and T2D Complications Several eNOS polymorphisms are related to an increased risk of T2D complications, including diabetic nephropathy (DN) and retinopathy. The mutant genotypes of G894T, T786C, and 4b4a VNTR were associated with higher risk of DN (OR=5.5, 95% CI=1.53-19.79; OR=1.8, 95% CI=1.03-3.16; OR=6.23, 95% CI=2.23-16.31, respectively) [99]. Compared to the GG genotype as the reference, the risk of developing end-stage renal disease (ESRD) among diabetic patients who carried GT and TT genotypes was 1.61 (95% CI=0.52-5.03) and 5.10 (95% CI=1.09-25.80), respectively [94]. In a group of Egyptian patients with T2D, the TT genotype of eNOS G894T polymorphism was more prevalent in patients with microalbuminuria, while there was no significant relation between eNOS T-786C polymorphism and DN [9]. A meta-analysis showed that compared with the 4b allele, the 4a allele is related to an elevated risk of DN (OR=1.26, 95% CI=1.10-1.45 in the global population; OR=1.51, 95% CI=1.13-2.01, in the Asian population) [100]. Moreover, compared to wildtype genotype, subjects who carried aa+ab genotypes have an increased risk of the nephropathy (OR=1.27, 95% CI=1.09-1.48 in global population; OR=1.54, 95% CI=1.16-2.05 in the Asian population) [100]. Carrying a versus b allele was also related to an increased risk of DN among Asiana (pooled estimated OR=1.59, 95% CI=1.22-2.09), and especially in the Chinese population (pooled estimated OR=2.02, 95% CI=1.31–3.11), but not in the non-Asian population (pooled estimated OR=0.99, 95% CI=0.84–1.17) [101]; aa versus bb genotype was also related to a considerable risk of nephropathy among T2D patients from Asian countries (pooled estimated OR= 3.94, 95% CI=2.72–5.71). However, it was not related to the development of nephropathy in patients from non-Asian countries (pooled estimated OR=1.02, 95% CI=0.64–1.61) [101]. All these eNOS gene polymorphisms have been suggested to lead to defective NO synthesis and decreased NO levels, contributing to DN's development and progression [99]. A meta-analysis of 48 published papers (including 3793 patients and 3161 controls for 4b4a, 2654 patients and 1993 controls for G894T, 1348 patients and 1175 controls for T786C) showed that carrying a versus b allele in the 4b4a VNTR polymorphism, increased risk of DN among East-Asian population (pooled estimated OR=1.68, 95% CI=1.23-2.30) but not Caucasian population (pooled estimated OR=1.03, 95% CI=0.90-1.18); aa versus bb genotypes was also related to an elevated risk of DN by ~3-fold (pooled estimated OR=2.92, 95% CI=1.78-4.81) only among Asian patients [102]. Similarly, carrying the T versus

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G allele in G894T polymorphism increased the risk of DN by 69% (pooled estimated OR=1.69, 95% CI=1.37-2.08) in T2D patients in Asian countries [102]. Another eNOS gene polymorphism, an intronic SNP rs891512 (corresponding to the G24943A transition of eNOS that changes cysteine 991 to serine), has been reported to be associated with T2D complications [103]; the GA+AA genotypes compared to GG genotype in SNP rs891512, were related to an increased chance of having hypertension (48.8% vs. 20.0%) and dyslipidemia in patients with T2D (39.4% vs. 30.4%) [103]. The polymorphism 4b4a VNTR was reported to be associated with a higher risk of retinopathy in patients with T2D; a meta-analysis of 15 studies (including 3183 cases and 3410 controls) indicated that carrying aa versus bb genotypes is related to a borderline decreased risk of retinopathy among Asian population (pooled estimated OR=0.78, 95% CI=0.61-1.01, P=0.06), while it increased risk among Caucasians (pooled estimated OR=0.1.64, 95% CI=0.98-2.73, P=0.06) [104]. CONCLUDING REMARKS Taken together, among NOS enzymes, mostly eNOS polymorphisms are associated with developing insulin resistance and T2D; the most common eNOS gene polymorphisms that might be linked with the risk of T2D are 4b4a VNTR and G894T variants. These functional polymorphisms may affect the activity of the eNOS and hence endogenous NO generation. Findings of meta-analyses address the underlying ethnicity-specific effect of eNOS gene polymorphisms on T2D risk and its complications. Asian populations seem to be more susceptible to mutant genotypes of eNOS. These data are relevant from a pharmacoethnicity point of view and may help develop drugs with genetic testing labels, leading to a better decision-making strategy towards more personalized medicine [105]. However, longitudinal study designs, well-controlled for the known risk factors of T2D, are required to confirm this conclusion. CONSENT FOR PUBLICATION Not applicable. CONFLICT OF INTEREST The author declares no conflict of interest, financial or otherwise. ACKNOWLEDGEMENTS Declared none.

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REFERENCES [1]

Tessari P, Cecchet D, Cosma A, et al. Nitric oxide synthesis is reduced in subjects with type 2 diabetes and nephropathy. Diabetes 2010; 59(9): 2152-9. [http://dx.doi.org/10.2337/db09-1772] [PMID: 20484137]

[2]

Natali A, Ribeiro R, Baldi S, et al. Systemic inhibition of nitric oxide synthesis in non-diabetic individuals produces a significant deterioration in glucose tolerance by increasing insulin clearance and inhibiting insulin secretion. Diabetologia 2013; 56(5): 1183-91. [http://dx.doi.org/10.1007/s00125-013-2836-x] [PMID: 23370528]

[3]

Hong YH, Yang C, Betik AC, Lee-Young RS, McConell GK. Skeletal muscle glucose uptake during treadmill exercise in neuronal nitric oxide synthase-μ knockout mice. Am J Physiol Endocrinol Metab 2016; 310(10): E838-45. [http://dx.doi.org/10.1152/ajpendo.00513.2015] [PMID: 27006199]

[4]

Shankar RR, Wu Y, Shen HQ, Zhu JS, Baron AD. Mice with gene disruption of both endothelial and neuronal nitric oxide synthase exhibit insulin resistance. Diabetes 2000; 49(5): 684-7. [http://dx.doi.org/10.2337/diabetes.49.5.684] [PMID: 10905473]

[5]

Nakata S, Tsutsui M, Shimokawa H, et al. Spontaneous myocardial infarction in mice lacking all nitric oxide synthase isoforms. Circulation 2008; 117(17): 2211-23. [http://dx.doi.org/10.1161/CIRCULATIONAHA.107.742692] [PMID: 18413498]

[6]

Colombo MG, Paradossi U, Andreassi MG, et al. Endothelial nitric oxide synthase gene polymorphisms and risk of coronary artery disease. Clin Chem 2003; 49(3): 389-95. [http://dx.doi.org/10.1373/49.3.389] [PMID: 12600950]

[7]

Niu W, Qi Y. An updated meta-analysis of endothelial nitric oxide synthase gene: three wellcharacterized polymorphisms with hypertension. 2011. [http://dx.doi.org/10.1371/journal.pone.0024266]

[8]

Casas JP, Cavalleri GL, Bautista LE, Smeeth L, Humphries SE, Hingorani AD. Endothelial nitric oxide synthase gene polymorphisms and cardiovascular disease: a HuGE review. Am J Epidemiol 2006; 164(10): 921-35. [http://dx.doi.org/10.1093/aje/kwj302] [PMID: 17018701]

[9]

Moguib O, Raslan HM, Abdel Rasheed I, et al. Endothelial nitric oxide synthase gene (T786C and G894T) polymorphisms in Egyptian patients with type 2 diabetes. J Genet Eng Biotechnol 2017; 15(2): 431-6. [http://dx.doi.org/10.1016/j.jgeb.2017.05.001] [PMID: 30647683]

[10]

Thameem F, Puppala S, Arar NH, et al. Endothelial nitric oxide synthase (eNOS) gene polymorphisms and their association with type 2 diabetes-related traits in Mexican Americans. Diab Vasc Dis Res 2008; 5(2): 109-13. [http://dx.doi.org/10.3132/dvdr.2008.018] [PMID: 18537098]

[11]

Monti LD, Barlassina C, Citterio L, et al. Endothelial nitric oxide synthase polymorphisms are associated with type 2 diabetes and the insulin resistance syndrome. Diabetes 2003; 52(5): 1270-5. [http://dx.doi.org/10.2337/diabetes.52.5.1270] [PMID: 12716763]

[12]

Tso AW, Tan KC, Wat NM, Janus ED, Lam TH, S L Lam K. Endothelial nitric oxide synthase G894T (Glu298Asp) polymorphism was predictive of glycemic status in a 5-year prospective study of Chinese subjects with impaired glucose tolerance. Metabolism 2006; 55(9): 1155-8. [http://dx.doi.org/10.1016/j.metabol.2006.04.012] [PMID: 16919532]

[13]

Carlström M, Liu M, Yang T, et al. Cross-talk Between Nitrate-Nitrite-NO and NO Synthase Pathways in Control of Vascular NO Homeostasis. Antioxid Redox Signal 2015; 23(4): 295-306. [http://dx.doi.org/10.1089/ars.2013.5481] [PMID: 24224525]

[14]

Stuehr DJ, Santolini J, Wang ZQ, Wei CC, Adak S. Update on mechanism and catalytic regulation in the NO synthases. J Biol Chem 2004; 279(35): 36167-70.

NO and T2D: Genetic Studies

The Role of Nitric Oxide in Type 2 Diabetes 121

[http://dx.doi.org/10.1074/jbc.R400017200] [PMID: 15133020] [15]

Santolini J. The molecular mechanism of mammalian NO-synthases: A story of electrons and protons. J Inorg Biochem 2011; 105(2): 127-41. [http://dx.doi.org/10.1016/j.jinorgbio.2010.10.011] [PMID: 21194610]

[16]

Lee SJ, Stull JT. Calmodulin-dependent regulation of inducible and neuronal nitric-oxide synthase. J Biol Chem 1998; 273(42): 27430-7. [http://dx.doi.org/10.1074/jbc.273.42.27430] [PMID: 9765272]

[17]

Daff S. Calmodulin-dependent regulation of mammalian nitric oxide synthase. Biochem Soc Trans 2003; 31(3): 502-5. [http://dx.doi.org/10.1042/bst0310502] [PMID: 12773144]

[18]

Tengan C, Rodrigues G, Godinho R. Nitric oxide in skeletal muscle: role on mitochondrial biogenesis and function. Int J Mol Sci 2012; 13(12): 17160-84. [http://dx.doi.org/10.3390/ijms131217160] [PMID: 23242154]

[19]

Marsden PA, Heng HH, Scherer SW, et al. Structure and chromosomal localization of the human constitutive endothelial nitric oxide synthase gene. J Biol Chem 1993; 268(23): 17478-88. [http://dx.doi.org/10.1016/S0021-9258(19)85359-0] [PMID: 7688726]

[20]

Oliveira-Paula GH, Lacchini R, Tanus-Santos JE. Endothelial nitric oxide synthase: From biochemistry and gene structure to clinical implications of NOS3 polymorphisms. Gene 2016; 575(2): 584-99. [http://dx.doi.org/10.1016/j.gene.2015.09.061] [PMID: 26428312]

[21]

Li H, Wallerath T, Förstermann U. Physiological mechanisms regulating the expression of endothelial-type NO synthase. 2002. [http://dx.doi.org/10.1016/S1089-8603(02)00127-1]

[22]

Qian XX, Mata-Greenwood E, Liao WX, Zhang H, Zheng J, Chen D. Transcriptional regulation of endothelial nitric oxide synthase expression in uterine artery endothelial cells by c-Jun/AP-1. Mol Cell Endocrinol 2007; 279(1-2): 39-51. [http://dx.doi.org/10.1016/j.mce.2007.08.017] [PMID: 17933457]

[23]

Zhang R, Min W, Sessa WC. Functional analysis of the human endothelial nitric oxide synthase promoter. Sp1 and GATA factors are necessary for basal transcription in endothelial cells. J Biol Chem 1995; 270(25): 15320-6. [http://dx.doi.org/10.1074/jbc.270.25.15320] [PMID: 7541039]

[24]

Förstermann U, Closs EI, Pollock JS, et al. Nitric oxide synthase isozymes. Characterization, purification, molecular cloning, and functions. Hypertension 1994; 23(6_pt_2): 1121-31. [http://dx.doi.org/10.1161/01.HYP.23.6.1121] [PMID: 7515853]

[25]

Cortese-Krott MM, Kelm M. Endothelial nitric oxide synthase in red blood cells: Key to a new erythrocrine function? Redox Biol 2014; 2: 251-8. [http://dx.doi.org/10.1016/j.redox.2013.12.027] [PMID: 24494200]

[26]

Zhao Y, Vanhoutte PM, Leung SWS. Vascular nitric oxide: Beyond eNOS. J Pharmacol Sci 2015; 129(2): 83-94. [http://dx.doi.org/10.1016/j.jphs.2015.09.002] [PMID: 26499181]

[27]

Wu G, Meininger CJ. Nitric oxide and vascular insulin resistance. Biofactors 2009; 35(1): 21-7. [http://dx.doi.org/10.1002/biof.3] [PMID: 19319842]

[28]

Alderton WK, Cooper CE, Knowles RG. Nitric oxide synthases: structure, function and inhibition. Biochem J 2001; 357(3): 593-615. [http://dx.doi.org/10.1042/bj3570593] [PMID: 11463332]

[29]

Huynh NN, Chin-Dusting J. Amino acids, arginase and nitric oxide in vascular health. Clin Exp Pharmacol Physiol 2006; 33(1-2): 1-8. [http://dx.doi.org/10.1111/j.1440-1681.2006.04316.x] [PMID: 16445692]

122 The Role of Nitric Oxide in Type 2 Diabetes

Bahadoran et al.

[30]

Forstermann U, Sessa WC. Nitric oxide synthases: regulation and function. 2012. [http://dx.doi.org/10.1093/eurheartj/ehr304]

[31]

Anthony S, Leiper J, Vallance P. Endogenous production of nitric oxide synthase inhibitors. Vasc Med 2005; 10(1_suppl) (Suppl. 1): S3-9. [http://dx.doi.org/10.1177/1358836X0501000102] [PMID: 16444863]

[32]

Berridge MJ. Cell signalling biology. Portland Press 2014.

[33]

Andrew P, Mayer B. Enzymatic function of nitric oxide synthases. Cardiovasc Res 1999; 43(3): 52131. [http://dx.doi.org/10.1016/S0008-6363(99)00115-7] [PMID: 10690324]

[34]

Fleming I, Bauersachs J, Fisslthaler B, Busse R. Ca2+-independent activation of the endothelial nitric oxide synthase in response to tyrosine phosphatase inhibitors and fluid shear stress. Circ Res 1998; 82(6): 686-95. [http://dx.doi.org/10.1161/01.RES.82.6.686] [PMID: 9546377]

[35]

Karantzoulis-Fegaras F, Antoniou H, Lai SLM, et al. Characterization of the human endothelial nitricoxide synthase promoter. J Biol Chem 1999; 274(5): 3076-93. [http://dx.doi.org/10.1074/jbc.274.5.3076] [PMID: 9915847]

[36]

Laumonnier Y, Nadaud S, Agrapart M, Soubrier F. Characterization of an upstream enhancer region in the promoter of the human endothelial nitric-oxide synthase gene. J Biol Chem 2000; 275(52): 4073241. [http://dx.doi.org/10.1074/jbc.M004696200] [PMID: 11013235]

[37]

Eliasson MJL, Blackshaw S, Schell MJ, Snyder SH. Neuronal nitric oxide synthase alternatively spliced forms: Prominent functional localizations in the brain. Proc Natl Acad Sci USA 1997; 94(7): 3396-401. [http://dx.doi.org/10.1073/pnas.94.7.3396] [PMID: 9096405]

[38]

Fagerberg L, Hallström BM, Oksvold P, et al. Analysis of the human tissue-specific expression by genome-wide integration of transcriptomics and antibody-based proteomics. Mol Cell Proteomics 2014; 13(2): 397-406. [http://dx.doi.org/10.1074/mcp.M113.035600] [PMID: 24309898]

[39]

Brenman JE, Chao DS, Gee SH, et al. Interaction of nitric oxide synthase with the postsynaptic density protein PSD-95 and alpha1-syntrophin mediated by PDZ domains. Cell 1996; 84(5): 757-67. [http://dx.doi.org/10.1016/S0092-8674(00)81053-3] [PMID: 8625413]

[40]

Chartrain NA, Geller DA, Koty PP, et al. Molecular cloning, structure, and chromosomal localization of the human inducible nitric oxide synthase gene. J Biol Chem 1994; 269(9): 6765-72. [http://dx.doi.org/10.1016/S0021-9258(17)37441-0] [PMID: 7509810]

[41]

Qidwai T, Jamal F. Inducible nitric oxide synthase (iNOS) gene polymorphism and disease prevalence. Scand J Immunol 2010; 72(5): 375-87. [http://dx.doi.org/10.1111/j.1365-3083.2010.02458.x] [PMID: 21039732]

[42]

Duplain H, Burcelin R, Sartori C, et al. Insulin resistance, hyperlipidemia, and hypertension in mice lacking endothelial nitric oxide synthase. Circulation 2001; 104(3): 342-5. [http://dx.doi.org/10.1161/01.CIR.104.3.342] [PMID: 11457755]

[43]

Cook S, Hugli O, Egli M, et al. Clustering of cardiovascular risk factors mimicking the human metabolic syndrome X in eNOS null mice. Swiss Med Wkly 2003; 133(25-26): 360-3. [PMID: 12947532]

[44]

Carlström M, Larsen FJ, Nyström T, et al. Dietary inorganic nitrate reverses features of metabolic syndrome in endothelial nitric oxide synthase-deficient mice. Proc Natl Acad Sci USA 2010; 107(41): 17716-20. [http://dx.doi.org/10.1073/pnas.1008872107] [PMID: 20876122]

NO and T2D: Genetic Studies

The Role of Nitric Oxide in Type 2 Diabetes 123

[45]

Cook S, Hugli O, Egli M, et al. Partial gene deletion of endothelial nitric oxide synthase predisposes to exaggerated high-fat diet-induced insulin resistance and arterial hypertension. Diabetes 2004; 53(8): 2067-72. [http://dx.doi.org/10.2337/diabetes.53.8.2067] [PMID: 15277387]

[46]

Vecoli C, Novelli M, Pippa A, Giacopelli D, Beffy P, Masiello P, et al. Partial deletion of eNOS gene causes hyperinsulinemic state, unbalance of cardiac insulin signaling pathways and coronary dysfunction independently of high fat diet 2014. [http://dx.doi.org/10.1371/journal.pone.0104156]

[47]

Sansbury BE, Cummins TD, Tang Y, et al. Overexpression of endothelial nitric oxide synthase prevents diet-induced obesity and regulates adipocyte phenotype. Circ Res 2012; 111(9): 1176-89. [http://dx.doi.org/10.1161/CIRCRESAHA.112.266395] [PMID: 22896587]

[48]

Zhang J, Kawashima S, Yokoyama M, Huang P, Hill CE. Protective effect of endothelial nitric oxide synthase against induction of chemically-induced diabetes in mice. 2007. [http://dx.doi.org/10.1016/j.niox.2007.06.001]

[49]

Carvalho-Filho MA, Ueno M, Hirabara SM, et al. S-nitrosation of the insulin receptor, insulin receptor substrate 1, and protein kinase B/Akt: a novel mechanism of insulin resistance. Diabetes 2005; 54(4): 959-67. [http://dx.doi.org/10.2337/diabetes.54.4.959] [PMID: 15793233]

[50]

Perreault M, Marette A. Targeted disruption of inducible nitric oxide synthase protects against obesity-linked insulin resistance in muscle. Nat Med 2001; 7(10): 1138-43. [http://dx.doi.org/10.1038/nm1001-1138] [PMID: 11590438]

[51]

Shinozaki S, Choi CS, Shimizu N, et al. Liver-specific inducible nitric-oxide synthase expression is sufficient to cause hepatic insulin resistance and mild hyperglycemia in mice. J Biol Chem 2011; 286(40): 34959-75. [http://dx.doi.org/10.1074/jbc.M110.187666] [PMID: 21846719]

[52]

Tsutsui M, Tanimoto A, Tamura M, et al. Significance of nitric oxide synthases: Lessons from triple nitric oxide synthases null mice. J Pharmacol Sci 2015; 127(1): 42-52. [http://dx.doi.org/10.1016/j.jphs.2014.10.002] [PMID: 25704017]

[53]

Razny U, Kiec-Wilk B, Polus A, et al. The adipose tissue gene expression in mice with different nitric oxide availability. J Physiol Pharmacol 2010; 61(5): 607-18. [PMID: 21081805]

[54]

Cha HN, Song SE, Kim YW, Kim JY, Won KC, Park SY. Lack of inducible nitric oxide synthase prevents lipid-induced skeletal muscle insulin resistance without attenuating cytokine level. J Pharmacol Sci 2011; 117(2): 77-86. [http://dx.doi.org/10.1254/jphs.11093FP] [PMID: 22001626]

[55]

Roth NJ, Zipperich S, Kopf J, Deckert J, Reif A. Influence of two functional polymorphisms in NOS1 on baseline cortisol and working memory in healthy subjects 2019. [http://dx.doi.org/10.1016/j.niox.2019.04.003]

[56]

O’Donovan MC, Craddock N, Norton N, et al. Identification of loci associated with schizophrenia by genome-wide association and follow-up. Nat Genet 2008; 40(9): 1053-5. [http://dx.doi.org/10.1038/ng.201] [PMID: 18677311]

[57]

Saur D, Vanderwinden JM, Seidler B, Schmid RM, De Laet MH, Allescher HD. Single-nucleotide promoter polymorphism alters transcription of neuronal nitric oxide synthase exon 1c in infantile hypertrophic pyloric stenosis. Proc Natl Acad Sci USA 2004; 101(6): 1662-7. [http://dx.doi.org/10.1073/pnas.0305473101] [PMID: 14757827]

[58]

Freudenberg F, Alttoa A, Reif A. Neuronal nitric oxide synthase ( NOS1 ) and its adaptor, NOS1AP, as a genetic risk factors for psychiatric disorders. Genes Brain Behav 2015; 14(1): 46-63. [http://dx.doi.org/10.1111/gbb.12193] [PMID: 25612209]

124 The Role of Nitric Oxide in Type 2 Diabetes

Bahadoran et al.

[59]

Hancock DB, Martin ER, Vance JM, Scott WK. Nitric oxide synthase genes and their interactions with environmental factors in Parkinson’s disease. Neurogenetics 2008; 9(4): 249-62. [http://dx.doi.org/10.1007/s10048-008-0137-1] [PMID: 18663495]

[60]

Martín MC, Martinez A, Mendoza JL, et al. Influence of the inducible nitric oxide synthase gene (NOS2A) on inflammatory bowel disease susceptibility. Immunogenetics 2007; 59(11): 833-7. [http://dx.doi.org/10.1007/s00251-007-0255-1] [PMID: 17955236]

[61]

Dhillon SS, Mastropaolo LA, Murchie R, Griffiths C, Thöni C, Elkadri A, et al. Higher activity of the inducible nitric oxide synthase contributes to very early onset inflammatory bowel disease 2014. [http://dx.doi.org/10.1038/ctg.2013.17]

[62]

Shen J, Wang R-T, Wang L-W, Xu Y-C, Wang X-R. A novel genetic polymorphism of inducible nitric oxide synthase is associated with an increased risk of gastric cancer. World J Gastroenterol 2004; 10(22): 3278-83. [http://dx.doi.org/10.3748/wjg.v10.i22.3278] [PMID: 15484300]

[63]

Warpeha KM, Xu W, Liu L, et al. Genotyping and functional analysis of a polymorphic (CCTTT) repeat of NOS2A in diabetic retinopathy. FASEB J 1999; 13(13): 1825-32. [http://dx.doi.org/10.1096/fasebj.13.13.1825] [PMID: 10506586]

[64]

Hobbs MR, Udhayakumar V, Levesque MC, et al. A new NOS2 promoter polymorphism associated with increased nitric oxide production and protection from severe malaria in Tanzanian and Kenyan children. Lancet 2002; 360(9344): 1468-75. [http://dx.doi.org/10.1016/S0140-6736(02)11474-7] [PMID: 12433515]

[65]

Boutlis CS, Bockarie MJ, Booth J, et al. Inducible nitric oxide synthase (NOS2) promoter CCTTT repeat polymorphism: relationship to in vivo nitric oxide production/NOS activity in an asymptomatic malaria-endemic population. Am J Trop Med Hyg 2003; 69(6): 569-73. [http://dx.doi.org/10.4269/ajtmh.2003.69.569] [PMID: 14740870]

[66]

Gonzalez-Gay MA, Llorca J, Palomino-Morales R, Gomez-Acebo I, Gonzalez-Juanatey C, Martin J. Influence of nitric oxide synthase gene polymorphisms on the risk of cardiovascular events in rheumatoid arthritis. Clin Exp Rheumatol 2009; 27(1): 116-9. [PMID: 19327239]

[67]

Pascual M, López-Nevot MA, Cáliz R, et al. Genetic determinants of rheumatoid arthritis: the inducible nitric oxide synthase (NOS2) gene promoter polymorphism. Genes Immun 2002; 3(5): 299301. [http://dx.doi.org/10.1038/sj.gene.6363856] [PMID: 12140750]

[68]

Salvi E, Kuznetsova T, Thijs L, et al. Target sequencing, cell experiments, and a population study establish endothelial nitric oxide synthase (eNOS) gene as hypertension susceptibility gene. Hypertension 2013; 62(5): 844-52. [http://dx.doi.org/10.1161/HYPERTENSIONAHA.113.01428] [PMID: 24019403]

[69]

Lacchini R, Silva PS, Tanus-Santos JE. A pharmacogenetics-based approach to reduce cardiovascular mortality with the prophylactic use of statins. Basic Clin Pharmacol Toxicol 2010; 106(5): 357-61. [http://dx.doi.org/10.1111/j.1742-7843.2010.00551.x] [PMID: 20210789]

[70]

Hingorani AD, Liang CF, Fatibene J, et al. A common variant of the endothelial nitric oxide synthase (Glu298-->Asp) is a major risk factor for coronary artery disease in the UK. Circulation 1999; 100(14): 1515-20. [http://dx.doi.org/10.1161/01.CIR.100.14.1515] [PMID: 10510054]

[71]

Tsukada T, Yokoyama K, Arai T, et al. Evidence of association of the ecNOS gene polymorphism with plasma NO metabolite levels in humans. Biochem Biophys Res Commun 1998; 245(1): 190-3. [http://dx.doi.org/10.1006/bbrc.1998.8267] [PMID: 9535806]

[72]

Tesauro M, Thompson WC, Rogliani P, Qi L, Chaudhary PP, Moss J. Intracellular processing of endothelial nitric oxide synthase isoforms associated with differences in severity of cardiopulmonary

n

NO and T2D: Genetic Studies

The Role of Nitric Oxide in Type 2 Diabetes 125

diseases: Cleavage of proteins with aspartate vs. glutamate at position 298. Proc Natl Acad Sci USA 2000; 97(6): 2832-5. [http://dx.doi.org/10.1073/pnas.97.6.2832] [PMID: 10717002] [73]

Chen XJ, Qiu CG, Kong XD, et al. The association between an endothelial nitric oxide synthase gene polymorphism and coronary heart disease in young people and the underlying mechanism. Mol Med Rep 2018; 17(3): 3928-34. [PMID: 29359785]

[74]

Lira Neto AB, Farias MCO, Vasconcelos NBR, Xavier AF Jr, Assunção ML, Ferreira HS. Prevalence of endothelial nitric oxide synthase (ENOS) gene G894T polymorphism and its association with hypertension: a population-based study with Brazilian women. Arch Med Sci Atheroscler Dis 2019; 4(1): 63-73. [http://dx.doi.org/10.5114/amsad.2019.84539] [PMID: 31211272]

[75]

Hillermann R, Carelse K, Gebhardt GS. The Glu298Asp variant of the endothelial nitric oxide synthase gene is associated with an increased risk for abruptio placentae in pre-eclampsia. J Hum Genet 2005; 50(8): 415-9. [http://dx.doi.org/10.1007/s10038-005-0270-8] [PMID: 16059745]

[76]

Li R, Lyn D, Lapu-Bula R, et al. Relation of endothelial nitric oxide synthase gene to plasma nitric oxide level, endothelial function, and blood pressure in African Americans*1. Am J Hypertens 2004; 17(7): 560-7. [http://dx.doi.org/10.1016/j.amjhyper.2004.02.013] [PMID: 15233974]

[77]

Gad MZ, Abdel Rahman MF, Hashad IM, Abdel-Maksoud SM, Farag NM, Abou-Aisha K. Endothelial nitric oxide synthase (G894T) gene polymorphism in a random sample of the Egyptian population: comparison with myocardial infarction patients. Genet Test Mol Biomarkers 2012; 16(7): 695-700. [http://dx.doi.org/10.1089/gtmb.2011.0342] [PMID: 22731641]

[78]

Moon J, Yoon S, Kim E, Shin C, Jo SA, Jo I. Lack of evidence for contribution of Glu298Asp (G894T) polymorphism of endothelial nitric oxide synthase gene to plasma nitric oxide levels. Thromb Res 2002; 107(3-4): 129-34. [http://dx.doi.org/10.1016/S0049-3848(02)00208-6] [PMID: 12431478]

[79]

Nishevitha NS, Angeline T, Jeyaraj N. Endothelial nitric oxide synthase (eNOS) Glu298-->Asp polymorphism (G894T) among south Indians. Indian J Med Res 2009; 129(1): 68-71. [PMID: 19287060]

[80]

Adibmanesh A, Bijanzadeh M, Mohammadzadeh G, Alidadi R, Rashidi M, Talaiezadeh A. The Correlation of Endothelial Nitric Oxide Synthase Gene rs1799983 Polymorphisms with Colorectal Cancer. Int J Cancer Manag 2020; 13(5)e97220 [http://dx.doi.org/10.5812/ijcm.97220]

[81]

Krex D, Fortun S, Kuhlisch E, Schackert HK, Schackert G. The role of endothelial nitric oxide synthase (eNOS) genetic variants in European patients with intracranial aneurysms. J Cereb Blood Flow Metab 2006; 26(10): 1250-5. [http://dx.doi.org/10.1038/sj.jcbfm.9600284] [PMID: 16467782]

[82]

Afrasyap L, Ozturk G. NO level and endothelial NO synthase gene polymorphism (Glu298Asp) in the patients with coronary artery disease from the Turkish population. Acta Biochim Biophys Sin (Shanghai) 2004; 36(10): 661-6. [http://dx.doi.org/10.1093/abbs/36.10.661] [PMID: 15483745]

[83]

Xie X, Shi X, Xun X, Rao L. Endothelial nitric oxide synthase gene single nucleotide polymorphisms and the risk of hypertension: A meta-analysis involving 63,258 subjects. Clin Exp Hypertens 2017; 39(2): 175-82. [http://dx.doi.org/10.1080/10641963.2016.1235177] [PMID: 28287883]

[84]

Piccoli JCE, Manfredini V, Faoro D, Farias FM, Bodanese LC, Bogo MR. Association between

126 The Role of Nitric Oxide in Type 2 Diabetes

Bahadoran et al.

endothelial nitric oxide synthase gene polymorphism ( -786T>C ) and interleukin-6 in acute coronary syndrome. Hum Exp Toxicol 2014; 33(4): 396-402. [http://dx.doi.org/10.1177/0960327113499046] [PMID: 23918902] [85]

Azuma S, Uojima H, Chuma M, et al. Influence of NOS3 rs2070744 genotypes on hepatocellular carcinoma patients treated with lenvatinib. Sci Rep 2020; 10(1): 17054. [http://dx.doi.org/10.1038/s41598-020-73930-3] [PMID: 33051476]

[86]

Paolo Rossi G, Cesari M, Zanchetta M, et al. The T-786C endothelial nitric oxide synthase genotype is a novel risk factor for coronary artery disease in Caucasian patients of the GENICA study. J Am Coll Cardiol 2003; 41(6): 930-7. [http://dx.doi.org/10.1016/S0735-1097(02)03012-7] [PMID: 12651036]

[87]

Mousavi-Nasab FS, Colagar AH. Investigation of the association of endothelial nitric oxide synthase (eNOS)-T786C gene polymorphism with the risk of male infertility in an Iranian population. Environ Sci Pollut Res Int 2020; 27(18): 22434-40. [http://dx.doi.org/10.1007/s11356-020-08860-8] [PMID: 32314287]

[88]

Dursun H, Noyan A, Matyar S, et al. Association of eNOS gene intron 4 a/b VNTR polymorphisms in children with nephrotic syndrome. Gene 2013; 522(2): 192-5. [http://dx.doi.org/10.1016/j.gene.2013.03.080] [PMID: 23570878]

[89]

Wang XL, Sim AS, Badenhop RF, Mccredie RM, Wilcken DEL. A smoking–dependent risk of coronary artery disease associated with a polymorphism of the endothelial nitric oxide synthase gene. Nat Med 1996; 2(1): 41-5. [http://dx.doi.org/10.1038/nm0196-41] [PMID: 8564837]

[90]

Hibi K, Ishigami T, Tamura K, et al. Endothelial nitric oxide synthase gene polymorphism and acute myocardial infarction. Hypertension 1998; 32(3): 521-6. [http://dx.doi.org/10.1161/01.HYP.32.3.521] [PMID: 9740620]

[91]

Ichihara S, Yamada Y, Fujimura T, Nakashima N, Yokota M. Association of a polymorphism of the endothelial constitutive nitric oxide synthase gene with myocardial infarction in the Japanese population. Am J Cardiol 1998; 81(1): 83-6. [http://dx.doi.org/10.1016/S0002-9149(97)10806-2] [PMID: 9462613]

[92]

Gardemann A, Lohre J, Cayci S, Katz N, Tillmanns H, Haberbosch W. The T allele of the missense Glu298Asp endothelial nitric oxide synthase gene polymorphism is associated with coronary heart disease in younger individuals with high atherosclerotic risk profile. Atherosclerosis 2002; 160(1): 167-75. [http://dx.doi.org/10.1016/S0021-9150(01)00554-8] [PMID: 11755935]

[93]

Çine N, Hatemi AC, Erginel-Unaltuna N. Association of a polymorphism of the ecNOS gene with myocardial infarction in a subgroup of Turkish MI patients. Clin Genet 2002; 61(1): 66-70. [http://dx.doi.org/10.1034/j.1399-0004.2002.610113.x] [PMID: 11903359]

[94]

Bessa SSE-D, Hamdy SM. Impact of nitric oxide synthase Glu298Asp polymorphism on the development of end-stage renal disease in type 2 diabetic Egyptian patients. Ren Fail 2011; 33(9): 878-84. [http://dx.doi.org/10.3109/0886022X.2011.605978] [PMID: 21854353]

[95]

Hoffmann IS, Tavares-Mordwinkin R, Castejon AM, Alfieri AB, Cubeddu LX. Endothelial nitric oxide synthase polymorphism, nitric oxide production, salt sensitivity and cardiovascular risk factors in Hispanics. J Hum Hypertens 2005; 19(3): 233-40. [http://dx.doi.org/10.1038/sj.jhh.1001801] [PMID: 15565175]

[96]

Albegali AA, Shahzad M, Mahmood S, Ullah MI, Amar A, Sajjad O. Genetic polymorphism of eNOS (G894T) gene in insulin resistance in type 2 diabetes patients of Pakistani population. Int J Diabetes Dev Ctries 2020; 40(2): 203-8. [http://dx.doi.org/10.1007/s13410-019-00775-6]

[97]

Angeline T, Krithiga HR, Isabel W, Asirvatham AJ, Poornima A. Endothelial nitric oxide synthase

NO and T2D: Genetic Studies

The Role of Nitric Oxide in Type 2 Diabetes 127

gene polymorphism (G894T) and diabetes mellitus (type II) among South Indians. Oxid Med Cell Longev 2011; 2011: 1-4. [http://dx.doi.org/10.1155/2011/462607] [PMID: 22110783] [98]

Jia Z, Zhang X, Kang S, Wu Y. Association of endothelial nitric oxide synthase gene polymorphisms with type 2 diabetes mellitus: A meta-analysis. Endocr J 2013; 60(7): 893-901. [http://dx.doi.org/10.1507/endocrj.EJ12-0463] [PMID: 23563728]

[99]

Ahluwalia TS, Ahuja M, Rai TS, et al. Endothelial nitric oxide synthase gene haplotypes and diabetic nephropathy among Asian Indians. Mol Cell Biochem 2008; 314(1-2): 9-17. [http://dx.doi.org/10.1007/s11010-008-9759-8] [PMID: 18401556]

[100] Zeng R, Duan L, Sun L, et al. A meta-analysis on the relationship of eNOS 4b/a polymorphism and diabetic nephropathy susceptibility. Ren Fail 2014; 36(10): 1520-35. [http://dx.doi.org/10.3109/0886022X.2014.958955] [PMID: 25296103] [101] Ma Z, Chen R, Ren H, Guo X, Chen JG, Chen L. Endothelial nitric oxide synthase (eNOS) 4b/a polymorphism and the risk of diabetic nephropathy in type 2 diabetes mellitus: A meta-analysis. Meta Gene 2014; 2: 50-62. [http://dx.doi.org/10.1016/j.mgene.2013.10.015] [PMID: 25606389] [102] He Y, Fan Z, Zhang J, et al. Polymorphisms of eNOS gene are associated with diabetic nephropathy: a meta-analysis. Mutagenesis 2011; 26(2): 339-49. [http://dx.doi.org/10.1093/mutage/geq100] [PMID: 21084433] [103] Seelenfreund D, Lobos SR, Quesada A, et al. Association of the intronic polymorphism rs891512 (G24943A) of the endothelial nitric oxide synthase gene with hypertension in Chilean type 2 diabetes patients. Diabetes Res Clin Pract 2012; 96(2): e47-9. [http://dx.doi.org/10.1016/j.diabres.2012.01.029] [PMID: 22425436] [104] Ma Z, Chen R, Ren HZ, Guo X, Guo J, Chen L. Association between eNOS 4b/a polymorphism and the risk of diabetic retinopathy in type 2 diabetes mellitus: a meta-analysis. J Diabetes Res 2014; 2014: 1-8. [http://dx.doi.org/10.1155/2014/549747] [PMID: 24895640] [105] Bachtiar M, Ooi BNS, Wang J, et al. Towards precision medicine: interrogating the human genome to identify drug pathways associated with potentially functional, population-differentiated polymorphisms. Pharmacogenomics J 2019; 19(6): 516-27. [http://dx.doi.org/10.1038/s41397-019-0096-y] [PMID: 31578463]

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CHAPTER 7

Role of Nitric Oxide in Diabetic Wound Healing Hamideh Afzali1, Tara Ranjbar2, Khosrow Kashfi2 and Asghar Ghasemi1,* Endocrine Physiology Research Center, Research Institute for Endocrine Sciences, Shahid Beheshti University of Medical Sciences, Tehran, Iran 2 Department of Molecular, Cellular, and Biomedical Sciences, Sophie Davis School of Biomedical Education, City University of New York School of Medicine, New York, NY 10031, USA 1

Abstract: Nitric oxide (NO), a gaseous free radical, is a key signaling molecule in the different phases of the normal wound healing process. The beneficial effects of NO in wound healing are related to its antibacterial properties, regulation of inflammatory response, stimulation of proliferation and differentiation of keratinocytes and fibroblasts, and promotion of angiogenesis and collagen deposition. NO deficiency is an important mechanism responsible for poor healing in diabetic wounds. In this chapter, the function of NO in diabetic wound healing and the possible therapeutic significance of NO in the treatment of diabetic wounds are discussed. Current knowledge supports this notion that NO-based intervention is a promising therapeutic approach for diabetic wound healing.

Keywords: Advanced glycated end products, Coagulation, Diabetic foot ulcer, Endothelial nitric oxide synthase, Hexosamine pathway, Hyperglycemia, Neuropathy, Nitric oxide, Peripheral arterial disease, Polyol pathway, Protein kinase C, Reactive oxygen species, Superoxide anion, Wound healing. INTRODUCTION The worldwide prevalence of diabetes is increasing [1]. Delay in wound healing is one of the most disabling problems in diabetes [2]. Results of a systematic review and meta-analysis indicate that the global prevalence of diabetic foot ulcer (DFU) is 6.3%, and this prevalence is higher in men (4.5%) than in women (3.5%) and type 2 (6.4%) than in type 1 (5.5%) diabetic patients [3]. The lifetime risk for developing DFU in a diabetic patient is ~25% [4]. Compared to diabetic patients without ulcers, those with DFU have a 50% higher risk of mortality [5] and a 1020 times more chance of lower limb amputation [6]. In addition, the yearly cost of Corresponding author Asghar Ghasemi: Endocrine Physiology Research Center, Research Institute for Endocrine Sciences, Shahid Beheshti University of Medical Sciences, Tehran, Iran; [email protected]., No. 24, Erabi Street, Velenjak, Tehran, Iran; Phone: +98 21 22409309; Fax: +98 21 22416264.

*

Asghar Ghasemi, Khosrow Kashfi, Zahra Bahadoran (Eds.) All rights reserved-© 2022 Bentham Science Publishers

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care for people with diabetes and foot ulcers is 5.4 times higher than for people with diabetes but without foot ulcers [7]. Diabetic patients with DFU have a lower quality of life [8] since chronic wounds decrease a patient's ability to do simple tasks and social functions and are among the leading causes of hospitalization [2, 8]. Current standard care for a diabetic wound is debridement, pressure offloading, appropriate dressing, and infection and glycemic control [9, 10]. However, the current treatment for DFU seems insufficient since a meta-analysis of randomized clinical trials reported that healing rates are 24.2% and 30.9% at 12 and 20 weeks among patients with neuropathic DFU who received standard care [11]. In addition, a recent meta-analysis demonstrated that the global recurrence rate of DFU was high, with 22.1% per person-year [12]. The increasing prevalence of diabetes, adverse effects of DFU on a patient's quality of life, and the high economic burden of DFU warrant further research for finding new therapeutic strategies for more effective wound management in diabetic patients. Understanding pathophysiological mechanisms that interrupt the normal wound healing process in diabetic patients helps in finding new treatments. Nitric oxide (NO) plays a significant role in skin pathophysiological responses, such as vasodilation, response to ultraviolet (UV) irradiation, inflammation, and apoptosis, and therefore affects several distinct aspects of wound healing [13]. NO regulates inflammatory response during the wound healing process, stimulates proliferation and differentiation of keratinocytes and fibroblasts, promotes angiogenesis and collagen deposition, and has antibacterial properties [14 - 16]. Decreased NO bioavailability in diabetes is an important factor in poor ulcer healing [17], and, therefore, NO-based therapies for DFU have received increasing attention in recent years. NO’s role as a mediator in normal wound healing has been reviewed extensively [14 - 16]. This chapter summarizes NO’s role in diabetic wound healing and discusses the potential applications of NObased treatment strategies in diabetic wounds. Types of Wound A wound is created following disruption of skin integrity, mucosal surfaces, or organ tissues [18]. According to the healing time, wounds are classified as acute and chronic types [19]. Acute wounds (e.g., surgical incisions) heal quickly through an orderly and timely process [18] in 5-10 days [19] or within 30 days from injury [19, 20]. Chronic wounds (e.g., diabetic ulcers, pressure ulcers, and venous ulcers) are not repaired after 12 weeks of initial insult [18, 20]. These wounds cannot produce anatomical and functional integration of the injury site through an orderly and timely process [21].

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Chronic wounds, which make up to ~70% of all skin wounds, are characterized by prolonged pathological inflammation, persistent infections, the inability of epidermal and/or dermal cells to respond to repair stimuli, and the formation of drug-resistant microbial biofilms [22]. Chronic ulcers are rarely seen in healthy people [21] and are more common in people with diabetes, obesity, or spinal cord injury [21]. Pathophysiology of Diabetic Foot Ulcer Peripheral neuropathy and peripheral arterial disease (PAD) are the two main risk factors that lead to DFU [23]. More than 60% of DFUs result from underlying peripheral neuropathy [23]. PAD incidence is 2–4 times more common in patients with diabetes compared to non-diabetic individuals [24]. Peripheral Neuropathy Increased levels of intracellular advanced glycated end products, increased hexosamine pathway flux and polyol pathway, activation of protein kinase C (PKC), and reduction of endothelial nitric oxide synthase (eNOS) expression are the main mechanisms causing hyperglycemic nerve damage [23, 25]. Neuropathy in diabetic patients is reflected in sensory, motor, and autonomic nervous system divisions [23]. Sensory neuropathy is the most common predictor of DFU in diabetes [4] and causes damage to sensation, which protects against stimuli, such as heat, pressure, and pain [4]. As a result, these patients are less sensitive to pressure-related trauma or other minor skin injuries, increasing their susceptibility to injury [4]. Damage to the motor nerves in the motor neuropathy causes deformities in the foot, abnormal foot pressure, and subsequent callus formation. It will gradually cause skin damage and create a wound [23]. In autonomic neuropathy, the foot becomes dry due to decreased secretory functions of the sebaceous and sweat glands [4]. Dry skin is prone to fissures and thus creates a site vulnerable to microbial infection [4]. Peripheral Arterial Disease (PAD) PAD is characterized by stenosis or occlusion of the lower limb’s arteries [26]. It commonly affects the tibial and peroneal arteries of the calf. It leads to acute or chronic ischemia, and in combination with digital artery disease, it also impairs wound healing by affecting circulation and blood flow of the lower limbs [23]. Hyperglycemia, smoking, age, hypertension, and hyperlipidemia are the most important risk factors for PAD [26]. Endothelial dysfunction decreases NO

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bioavailability, the most serious impairment in diabetic patients with PAD that affects microcirculation [26]. NO is a potent endothelium-derived vasodilator, that inhibits platelet activation, decreases inflammation, and vascular smooth muscle cell migration and proliferation [4, 26]. Therefore, the disturbance of NO homeostasis can lead to a cascade of events in the vasculature culminating in atherosclerosis and its consequent complications [26]. Hyperglycemia, insulin resistance, and free fatty acid production are mechanisms underlying disturbed NO homeostasis [26]. Hyperglycemia inhibits eNOS and increases the production of reactive oxygen species (ROS) [26]. In addition, the superoxide anion (as a species of ROS) binds to NO, producing peroxynitrite and limiting NO’s bioavailability [4]. PHASES OF WOUND HEALING As shown in Fig. (1), normal wound healing has four phases: hemostasis (coagulation), inflammation, proliferation, and tissue remodeling [18, 20, 27]. Hemostasis (Coagulation) The homeostasis phase begins immediately after injury [19], and its primary purpose is to prevent bleeding [19]. After wounding, damage to small blood vessels triggers neural reflex mechanisms, resulting in rapid contraction of vascular smooth muscles in blood vessels [19]. This contraction temporarily stops the bleeding for a few minutes and eventually leads to hypoxia and tissue acidosis [18, 19], which increase the production of NO, adenosine, histamine, and other vasoactive metabolites; these metabolites produce relaxation and increase vascular permeability, thus facilitate the migration of inflammatory cells into the wound space [19]. Simultaneously the coagulation cascade is activated and leads to platelet aggregation and clot formation to limit blood loss and the formation of a provisional fibrin-rich matrix for cell migration in the subsequent phases [19]. Platelets, trapped within the clot, release contents of their α-granules [19] and dense granules [18] that contain cytokines and growth factors, e.g., plateletderived growth factor (PDGF), transforming growth factor-β (TGF-β), epidermal growth factor (EGF), and insulin-like growth factor (IGF) [19]. These factors cause the activation and attraction of neutrophils, macrophages, endothelial cells, and fibroblasts [19].

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Fig. (1). The wound healing process in normal and diabetic wounds. There are four phases of wound healing: hemostasis, inflammation, proliferation, and remodeling. Immediately after injury, the hemostasis phase begins. Platelets form a plug and release several cytokines, which recruit neutrophils and other leukocytes to the injury site to start the inflammation phase. Leukocytes start clearing the wound of bacteria, debris, and other foreign invaders. In the proliferation phase, granular tissue and new blood vessels form, keratinocytes migrate to the wound center, form a new epithelium, and fibroblasts produce collagen. In the final phase (remodeling), collagen type III is replaced by collagen type I, vascular density decreases, wound contracts, and fibroblasts release enzymes to remove damaged extraneous extracellular matrix. In a diabetic condition, each wound healing phase may be disrupted and causes a delay in the normal healing process. Created with Biorender.com.

Inflammation The main purpose of the inflammatory phase is to produce an immune barrier against invading microorganisms [18]. Neutrophils are the first cells that enter the wound bed about one hour after wounding by various chemoattractant agents, such as complement components, TGF-β, and interleukins [18]. The migration of neutrophils into the wound peaks about 24 hours after wounding and continues until about 48 hours later [18]. Neutrophils destroy bacteria and dead tissue debris at the wound site via different mechanisms, including phagocytosis, the release of antimicrobial peptides, proteolytic enzymes, and ROS production [18]. Once completed their function, neutrophils are removed from the wound site via apoptosis or phagocytosis by macrophages [18, 28].

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Monocytes also enter the wound from the blood and differentiate into macrophages [18]. Macrophages are larger phagocytic cells that reach their peak concentration within 48-72 hours after wounding [18]. Macrophages are attracted to the wound by chemical messengers released from platelets and damaged blood cells and can survive in the more acidic wound environment present at this stage [18]. Macrophages are a major source of growth factors, such as TGF-β, vascular endothelial growth factor (VEGF), and EGF; these growth factors play an essential role in regulating inflammatory response, stimulating angiogenesis, and increasing granular tissue formation. Lymphocytes take action 72-120 hours after injury, produce extracellular matrix scaffold, and cause collagen remodeling [18]. Proliferation The proliferative phase is characterized by re-epithelialization, angiogenesis, granular tissue formation, and collagen deposition [29, 30]. Re-epithelialization is a term used to describe skin regeneration with new epithelium on the wound and needs an orderly series of events whereby keratinocytes migrate, proliferate, and differentiate [29]. Re-epithelialization starts approximately 16-24 h after injury, and during re-epithelialization, the keratinocytes migrate from the surrounding wound margins toward the center of the wound [29]. To produce more cells to cover the wound, keratinocytes in the basal layer of the wound edge and epithelial stem cells from hair follicles or sweat glands begin to proliferate [29, 30]. This process is stimulated by changes in mechanical tension, electrical gradients, and several wound-related signals, e.g., NO, cytokines and growth factors, including EGF, IGF-1, keratinocyte growth factor (KGF), and nerve growth factor (NGF) secreted from multiple cell types in the wound [30]. Keratinocyte migration terminates when migrating cells touch each other, forming new adhesion structures [30]. Angiogenesis, the formation of new blood vessels from preexisting vessels, is vital for healing [31]. These new vessels supply blood containing oxygen and nutrients required to support the growth and function of repair cells [31]. After forming a hemostatic plug, angiogenesis starts with TGF-β, PDGF, and FGF released from platelets and later by VEGF, which is released from various cells, such as keratinocytes and macrophages due to tissue hypoxia [18]. Combined with the other cytokines, these growth factors trigger new blood vessel formation in the wound bed [18]. Although both vasculogenesis, the de novo formation of new blood vessels by endothelial progenitor cells (EPCs) and angiogenesis occur during wound healing, angiogenesis is investigated mostly as a mechanism of neovascularization in the diabetic wound [31].

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Granular tissue, named after granular appearance when examined visually, begins to form approximately 2-4 days after wounding [30]. It is characterized by a high density of fibroblasts, granulocytes, macrophages, and blood vessels in complex collagen bundles [30]. Fibroblasts are dominating cells in granular tissue formation [30]. Following the wound insult, fibroblasts migrate mainly from the nearby dermis to the wound in response to growth factors released from the hemostatic clot (predominantly TGF-β and PDGF) [18]. Fibroblasts degrade the provisional wound matrix by producing proteinases, e.g., matrix metalloproteinases (MMPs), and gradually replace it with granular tissue by the production of immature collagen and extracellular matrix (ECM) substances (i.e., fibronectin, glycosaminoglycans, hyaluronic acid, and proteoglycans) [30]. The ECM is an important healing mediator, provides a scaffold for cell adhesion and migration, and facilitates signal transduction in the wound [30]. At the end of this phase, the fibroblast differentiates from the myofibroblast phenotype, generating contraction forces that promote wound closure [30]. Collagen, a key component in providing tensile strength of the wound, is one of the main components of the matrix synthesized by fibroblasts [32]. The collagen composition of unwounded skin is approximately 80% collagen type I and 10% collagen type III [32]. By contrast, granular tissue predominantly comprises collagen type III, with only 10% collagen type I [32]. Tissue Remodeling The remodeling phase is the last phase of wound healing that can take up to 2 years or more [18]. This phase is responsible for developing new epithelium and scar formation and requires a balance between the production of new cells and the apoptosis of existing cells [18]. The normal balance between synthesis and degradation of ECM is regulated by the MMP/TIMP (tissue inhibitor of metalloproteinases) ratio [33]. MMPs cleave collagen, fibronectin, and other ECM components; TIMPs bind to and inhibit activated MMPs [33]. During the remodeling phase, components of the ECM undergo specific changes, so that collagen type III is replaced by collagen type I, vascular density decreases, and myofibroblasts cause the wound to contract. Finally, a mature scar with high tensile strength is formed [30]. CHANGES IN HEALING PHASES IN DIABETIC WOUNDS As shown in Fig. (1) and Table 1, in a diabetic wound, each phase of wound healing may be disrupted and causes a delay in the normal healing process [34]. Indeed, the inflammation phase is prolonged and ineffective in diabetic wounds [19]. In the proliferative phase, diabetic wounds have failure in reepithelialization [35]; keratinocytes at the margins of diabetic ulcers are highly

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proliferative but have lower ability for differentiation and migration, factors that may contribute to slow wound repair [35]. In addition, decreased angiogenesis is found in diabetic wound healing in type 1 and type 2 diabetic animals [36 - 38]. Topical administration of high glucose levels in wound sites of non-diabetic rats leads to inhibition of angiogenesis and granular tissue formation [39]. Furthermore, delay in granular tissue formation has been reported in full-thickness skin wounds of db/db type 2 diabetic mice [40, 41] and type 1 diabetic rats [42]. In diabetic wounds, the ability of migration and proliferation of fibroblasts [33, 43], response to growth factors and cytokines, and production of collagen and fibronectin are decreased [33]. Table 1. Changes in wound healing phases in diabetes. Phase

Features

Ref.

Hemostasis (Coagulation)

Increased risk of infection

[55]

Poor vascular supply

[55]

Inflammation

Prolonged and ineffective

[19]

Failure in re-epithelialization

[35]

Decreased angiogenesis

[36 - 38]

Delay in granular tissue formation

[40, 41]

Decreased collagen levels

[44 - 46]

Increased expression of MMPs

[47, 48]

Decreased expression of TIMPs

[47, 48]

Increased MMP/TIMP ratio

[47, 48]

Decreased tensile strength and wound contraction

[49, 50]

Proliferation

Tissue Remodeling

MMP, matrix metalloproteinase; TIMP, tissue inhibitor of metalloproteinases.

Hydroxyproline assay and Masson’s trichrome staining of diabetic wounds in humans and animals indicate decreased collagen levels in diabetic wounds [44 46]. Regarding tissue remodeling, it has been reported that in diabetic wound homogenates of both humans and animals, expression of MMPs increases, whereas expression of TIMPs decreases [33, 47, 48]. Decreased tensile strength and wound contraction during the remodeling phase also are observed in type 1 and type 2 diabetic animal models [49, 50]. Nitric Oxide Synthesis in the Skin Nitric oxide is produced in the skin via two pathways: (1) Classic L-arginine-NO pathway in which L-arginine is converted to NO by three isoforms of NOS including eNOS, neuronal NOS (nNOS), and inducible NOS (iNOS) [51]; (2)

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NOS-independent NO pathway, which also named nitrate-nitrite-NO pathway [52, 53]. In the latter pathway, surface bacteria in the skin [52] and UV radiation [53, 54] contribute to NO production from nitrite. Expression of NOS Isoforms in the Skin In the skin, eNOS is expressed in normal melanocytes [56], fibroblasts [57, 58], endothelial cells [57, 58], apocrine and eccrine secretory glands [57, 58], arrector pili muscle [57], and dermal papilla cells [51]. However, there is no consensus about eNOS expression in keratinocytes of normal human skin [56, 57]. nNOS is expressed in both keratinocytes and melanocytes of normal human skin [59, 60]. iNOS expression can be detected in all skin cells after stimulation with proinflammatory stimuli, mainly interleukin-1 β (IL-1β), tumor necrosis factor-α (TNF-α), and interferon-gamma (IFN-γ) [61]. NOS-Independent NO Synthesis in the Skin NOS-independent NO production in the skin is supported by the data showing that the enzymatic inhibition of NO synthesis by the NOS antagonist L-NMMA (NG-Monomethyl-L–arginine, systemic infusion) does not affect NO production in the surface of the normal human skin [52]. In addition, it has been shown that NOS inhibitors do not affect UVA-induced NO formation in the skin [53]. UV radiation triggers a rapid NOS-independent NO formation in the human skin by photo-decomposition of RSNO and nitrite Fig. (2). [53] that has a protective effect against UVA-induced cell death [62]. UV irradiation also increases iNOS activity; however, it has a delay and starts 8 to 10 h after exposure [53, 63]. The Role of Surface Bacteria in Skin Production of NO Ammonia oxidizing bacteria (AOB) are an important group of microorganisms in soil and water and are essential components of the nitrogen cycle and environmental nitrification processes [64]. Nitrosomonas eutropha in the skin, as a commensal AOB, oxidizes sweat ammonia (NH3) as an energy source and generates nitrite (NO2-) [65], which is converted to NO under acidic skin conditions or by photochemical reactions Fig. (2) [52, 53]. Modern hygiene practices have led to the removal of skin bacteria, including those that were once a vital part of the normal commensal microflora of the skin [64]. It has also been reported that skin NO generation is lower in patients who have been systemically treated for a long time with tetracycline antibiotics, indicating the involvement of a bacterial mechanism for NO generation in the skin’s surface [52].

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Fig. (2). Nitric oxide (NO) synthase-independent NO synthesis in the skin. AOB, ammonia-oxidizing bacteria; NH3, ammonia, NO3-, nitrate; NO2-, nitrite, RSNO, S-nitrosothiols; UVA, ultraviolet A. Created by BioRender.com.

UVA Radiation and NO Production Human skin is exposed to UV radiation daily, mainly through sunlight [66]. Solar UV is subdivided into three wavelength ranges: UVA (315-400 nm), UVB (280–315 nm), and UVC (100-280 nm) [66], of which the atmosphere absorbs UVC, and thus sunlight mainly consists of UVA (95-90%) and UVB (5-10%) [66]. UVB is almost entirely absorbed by the epidermis, with a relatively small amount reaching the dermis [66]; however, UVA penetrates deeply into the dermis [66]. Exposing normal human skin samples to UVA irradiation (at a dose equivalent to approximately 90-120 min of sun exposure in the mid-European summer) causes a high amount of NO formation in the skin, which is not affected by NOS inhibitors [53]. Depletion of the NO metabolites (nitrite, RSNO, and reduced thiols) or the presence of the NO scavenger during UVA exposure completely blocks UVA-induced NO formation [53]. During the UVA challenge, nitrite and RSNOs are the major sources of NO production, and unexpectedly, nitrate does not contribute to UVA-stimulated NO release from the human skin [53, 63].

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NO AND WOUND HEALING Before NO’s role in wound healing was known, studies showed that dietary intake of L-arginine promotes wound healing in both animals [67, 68] and humans [69]. The beneficial effects of arginine on wound healing may partly be due to the production of proline and polyamines from the arginase pathway, which is directly involved in collagen synthesis and cell proliferation, respectively Fig. (3) [70]. However, a study performed on wounds in iNOS knockout mice showed that arginine supplementation does not improve collagen deposition in iNOS knockout mice to the same extent as in wild-type; this data suggests that the iNOS-NO pathway is important for arginine-mediated effects on wound healing [71]. In subsequent experiments, NO production after wounding was confirmed by increasing urinary nitrate excretion [72], increasing nitrate/nitrite in wound fluid [73], and increasing the activity and expression of NOS isoforms in the wound [38, 74].

Fig. (3). Two pathways of L-arginine metabolism involved in wound healing. NOS, nitric oxide (NO) synthase; OAT, ornithine aminotransferase; ODC, ornithine decarboxylase. Created by BioRender.com.

NO Metabolites as an Index of Wound NO Nitrate and nitrite, collectively called NOx, are present as stable NO metabolites in plasma, urine, and tissues [75]. In experimental and clinical wound healing studies, NOx is used as a reliable alternative indicator of wound NO biological activity [75]. For measuring NOx, wound fluid is extracted from a cultured sponge in the wound environment, or wound/skin homogenates are used [41, 76 78]. Paunel et al. reported that in normal human skin, the concentrations of

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nitrate, nitrite, and RSNOs are 5, 25, and 360 times higher than those of plasma, respectively [53]. [Human skin: nitrate: 82.4±33.6 μM; nitrite: 5.1±1.6 μM; RSNOs: 2.6±1 μM. Human plasma: nitrate: 14.1±1.7 μM; nitrite: 0.20±0.02 μM; RSNOs: 7.2±1.1 nM [79]. Role of NO different Phases of Wound Healing NO affects multiple aspects of the wound healing process, including inflammation, angiogenesis, cell proliferation, matrix deposition, and remodeling [14]. NO’s role as a mediator of normal wound healing has been reviewed extensively [14 - 16] and is summarized here in brief. Inflammation Macrophages are important cells of the innate immune system that regulate various processes during normal wound healing, including cleaning, reepithelization, revascularization, and fibroblast regeneration [80]. Macrophages switch their phenotype throughout the wound healing process to perform various functions [80]. In the early stages of repair, about 85% of macrophages have the M1 phenotype, and by secreting NO and pro-inflammatory factors involved in cleaning bacteria, foreign debris, and dead cells, 15% have the M2 phenotype [81]. By changing the local environment of the wound, at days 5-7 post-injury, this ratio switches so that only 15-20% of the macrophages have M1 phenotype, and most of them have M2 phenotype [81, 82]. M1 macrophages are the primary source of iNOS expression in the inflammatory phase [83]. NO produced by iNOS in macrophages is an essential component of the host immune response against various pathogens [83]. In rodents, iNOS and arginase-1 are hallmark molecules for M1 and M2 macrophages, respectively [80, 84]. Numerous studies have shown that NO affects differentiation [85 - 87], migration [88 - 91], and phagocytic activity [92] of macrophages. The antimicrobial effects of NO are concentration-dependent [93]. At low concentrations (< 1 μM), NO acts as a signaling molecule that stimulates proliferation, differentiation, the activity of the immune cells, and cytokine production [93]. At higher concentrations (> 1 μM), NO binds to the DNA, lipids, and proteins of pathogens and thus kills or inhibits target microorganisms [93]. Microbial products such as lipopolysaccharide and lipoteichoic acid, and proinflammatory cytokines such as IFN-γ, TNF-α, IL-1, and IL-2 stimulate iNOS, which produces high concentrations of NO [94]. The application of exogenous NO for antimicrobial therapy is similar to the action of iNOS, both of which produce high amounts of NO for long periods to defend against microbes [93]. One possible mechanism for the antimicrobial activity of NO is its spontaneous reactions with reactive oxygen intermediates, such as hydrogen peroxide (H2O2)

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and superoxide (O2-), to produce a variety of antimicrobial molecular species, including peroxynitrite (OONO-), RSNO, nitrogen dioxide (NO2), dinitrogen trioxide (N2O3), and dinitrogen tetroxide (N2O4) [95]. These reactions occur when NO concentrations exceed 1 μM [93]. These reactive intermediates damage microbial DNA, inhibit the essential metabolic enzymes of bacteria, destroy the microbial cell membrane through lipid peroxidation, and deplete intracellular iron stores and thereby kill foreign microorganisms [95]. Vasculogenesis and Angiogenesis The eNOS/NO signaling pathway plays an important role in neovascularization processes (vasculogenesis and angiogenesis) during wound healing [96, 97]. Vasculogenesis is defined as new blood vessel formation from endothelial progenitor cells (EPCs) during embryonic development [31]. It can also occur in ischemic conditions in adult tissues [31, 98]. Bone marrow-derived EPCs are major cells involved in postnatal vasculogenesis [99, 100]. Data obtained from eNOS-deficient mice indicates an important role for eNOS-derived NO in EPCs mobilization and neovascularization [101]. EPC mobilization to sites of wound ischemia starts with releasing hypoxia-VEGF-A [102]. Immediately following injury, the wound becomes hypoxic because of damage to the blood vessels [103]. This site's low oxygen levels lead to hypoxia-inducible factor (HIF) accumulation, which can bind to the VEGF gene promoter and induce VEGF gene expression [104]. Hypoxia enhances VEGF expression in keratinocytes, fibroblasts, endothelial cells, mast cells, and macrophages in different stages of wound healing [105 - 107]. In the bone marrow, VEGF induces protein kinase Bdependent phosphorylation and activation of eNOS and increases NO [101], which activates MMP-9 [108]. MMP-9 facilitates the release of chemokine stem cell factors like soluble kit ligand (SCF), which stimulates mobilization of bone marrow EPCs to the circulation [108, 109]. EPCs homing from circulation to the wound site is done with the help of stromal cell-derived factor-1 (SDF-1) [110]. Angiogenesis, the formation of new blood vessels from existing vessels, is an important feature of the proliferative phase of healing [103, 111]. Wound angiogenesis is a substantial process for tissue formation and repair, and re-supply of oxygen and other nutrients to the wound site [103]. Angiogenesis occurs in several differentiated steps, including vasodilation, basement membrane degradation, migration and proliferation of endothelial cells, lumen formation, and endothelial survival and differentiation [112]. NO participates in angiogenesis by inducing vasodilation and endothelial cell proliferation and migration [112, 113]. NO’s importance in wound angiogenesis has been demonstrated in eNOS knockout mice in which angiogenesis is decreased and wound closure impaired

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[114]. In iNOS knockout mice, angiogenesis is lower in incisional and more markedly in excisional skin wounds in the first 7-day post-injury [115]. Re-epithelialization Several hours after injury, re-epithelialization initiates with the proliferation and migration of keratinocytes from the wound edge into the wound [29]. Results of an in vitro experiment indicates that NO at low concentrations (0.01 to 0.25 mM) increases keratinocyte proliferation and at high concentrations (≥ 0.5 mM) increases cytostasis [116]. iNOS inhibition using the specific iNOS inhibitor LN6-(1-iminoethyl)-lysine (L-NIL) in mice causes delayed re-epithelialization of the wounds, which was due to decreased keratinocyte proliferative capacity within the hyperproliferative epithelium during the process of tissue regeneration [117]. In addition, eNOS-deficient mice display reduced wound margin epithelia associated with reduced keratinocyte proliferation, indicating the contribution of eNOS in re-epithelialization [38]. Fibroblasts, principal cells of the dermis, play a pivotal role in normal wound healing and are involved in key processes, including creating new ECM and collagen structures, and wound contraction [118]. Data obtained from iNOSknockout mice indicates that loss of the iNOS gene function leads to reduced fibroblasts proliferation, impaired collagen synthesis, decreased contractile properties in dermal fibroblasts [119], and reduced numbers of myofibroblasts in the wound bed [89]. In contrast, it has been reported that NO donor SNAP at low concentrations (5-25 μM) restores collagen synthesis to normal in iNOS-knockout cells and at higher doses (50-400 μM) inhibits collagen synthesis [119]. These results indicate that NO plays a substantial role in collagen synthesis in fibroblasts. In addition, NO regulates MMP synthesis in fibroblast [120]. MMPs belong to a family of zinc-dependent proteolytic enzymes with multiple roles in tissue remodeling and degradation of various proteins in the ECM [120]. All wounds require a certain amount of these enzymes, but MMPs could be very damaging at high concentrations and cause excessive degradation and impaired wound healing [121]. NO AND DIABETIC WOUND HEALING As shown in Table 2, NOx levels are lower in diabetic wounds, indicating decreased NO synthesis due to decreased eNOS and iNOS expressions [38, 41, 122]. Decreased NO synthesis in the diabetic wound may reflect a decreased number of NO-producing cells (e.g., macrophages, keratinocytes, and fibroblasts) migrating into the wound or a reduced capacity of these cells to produce NO [76]. Decreased wound NO in diabetes impairs wound healing as manifested by an impaired inflammatory response [77, 122], decreased collagen synthesis

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[46, 76 - 78], poor re-epithelization and angiogenesis [41, 78], and reduced wound breaking strength [41, 45]. Table 2. Nitric oxide metabolites (NOx) levels in rodent models of wound healing. Animal (Body Weight)

Wound Type

Measurement Time

Sample

Male Sprague Dawley rat (290-310 g)

Incisional (7 cm midline dorsal skin)

10

Wound fluid

Male Sprague Dawley rat (NR)

Incisional (7 cm midline dorsal skin)

10

Wound fluid

Male Lewis rat (225-266 g)

Incisional (7 cm midline dorsal skin)

10

Wound fluid

Male Sprague Dawley rat (225-250 g)

Incisional (7 cm midline dorsal skin)

10

Wound fluid

Female mice Incisional (22–25 g) (4 cm dorsal skin)

7

Wound homogenate

Male Swiss mice (25-30 g)

6

Wound homogenate

Excisional (2 cm ×2 cm, fullthickness)

Male Wistar rat (190-210 g)

Excisional (8 mm, fullthickness)

3, 7, 14

Male Sprague Dawley rat (240-280 g)

Incisional (7 cm midline dorsal skin)

1, 3 and 10

Status

NOx

Normal

145.2 μM

Diabetes*

46.4 μM

Normal

110 μM

Diabetes*

90 μM

Normal

0.69 μM

Diabetes*

0.61 μM

Normal

∼62 μM

Diabetes*

∼42 μM

Normal

∼16 nmol/g

Diabetes**

∼7 nmol/g

Normal

∼45 μM

Diabetes*

∼25 μM

Normal

5.2, 7.3, 5.6 nmol/mg protein

Diabetes***

2.4, 3.8, 3.7 nmol/mg protein

Diabetes*

882, 734.4, 461 μM

Wound homogenate

Wound fluid

Ref.

[76]

[77]

[46]

[128]

[41]

[78]

[122]

[45]

In all studies, NOx was measured by the Griess reaction. NR; not reported. * Type 1 diabetes (T1D) (STZ/70 mg/kg), ** Type 2 diabetes (T2D) (db+/db+ mice), ***T2D (low-dose of STZ/high-fat diet).

In diabetic wounds, macrophage dysfunction impairs the resolution of inflammation and leads to a prolonged inflammatory phase [28]. It has been reported that topical application of acidified nitrite increases the numerical density of macrophages on day 7 after wounding in type 2 diabetic rats [123] and restores delayed inflammatory response in diabetic rats [123]. Chronic, nonhealing wounds in diabetes are characterized by impaired neovascularization

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(vasculogenesis and angiogenesis processes) in granular tissue [111, 124]. Bone marrow-derived EPCs are major cells involved in the vasculogenesis in the skin wound in T1D and T2D [125, 126]. In both types of diabetes, EPCs have a lower number and display dysfunction [99, 100]. In addition, it has been reported that impairment of bone marrow eNOS phosphorylation in streptozotocin (STZ)induced diabetic mice attenuates EPC mobilization from bone marrow to the circulation [127]. Role of NO Different Phases of Diabetic Wound Healing Although both vasculogenesis and angiogenesis are known to occur during wound healing, angiogenesis is mostly investigated as a mechanism of neovascularization in a diabetic wound. Decreased angiogenesis in skin wounds is frequently reported in diabetic wound healing in type 1 and type 2 diabetic animals [36 - 38]. The cutaneous eNOS expression significantly decreases in STZ-induced type 1 diabetic animals, which causes impaired wound angiogenesis and healing [129, 130]. Wound angiogenesis is a key factor in successful wound healing. NOS/NO signaling has clinical importance for creating potential therapeutic targets to increase wound angiogenesis, especially in diseases such as diabetes. It is reported that the lack of eNOS protein expression in type 2 diabetic mice has been accompanied by impaired epithelial recovery [38]. In a study conducted on human diabetic fibroblasts, failure in NO production by fibroblasts was associated with elevated MMPs [120]. Using the same experimental system, this group demonstrated that NO donor administration stimulates NO production by fibroblasts, increases cell proliferation, and decreases MMP-8 and -9 expression in a dose-dependent manner [120]. According to an excellent review by Auke et al., poor healing in diabetes could be due to overexpression of the MMPs [121]. NO AND THERAPEUTIC STRATEGIES FOR DIABETIC WOUND As described above, impaired wound healing in diabetes has been associated with reduced NO production. Therefore, NO as a wound healing therapeutic agent is vital for improving healing. However, its high reactivity and short half-life provide challenges for designing appropriate NO-based treatments for diabetic wounds. A multicenter, prospective, observer-blinded, parallel-group, randomized controlled trial, including 135 participants (T1D or T2D) with a chronic, fullthickness foot ulcer (present for at least 6 weeks), assessed the safety and efficacy of EDX110, an NO generating medical device, in the treatment of DFU compared against an optimal standard of care [131]. Both groups received standard care (debridement, offloading, and antimicrobial treatment); however, the NO-treated

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group also received EDX110 dressing. The result indicated improved healing, 88.6% ulcer area reduction at 12 weeks compared with 46.9% in those receiving standard dressings [131]. Of note, wound infection is a major complication in diabetic patients, and more than 50% of non-traumatic lower-extremity amputations are related to DFU infections [132]. Methicillin-resistant Staphylococcus aureus (MRSA) is a major hospital-acquired pathogen that is a serious problem in cases of DFU [133]. Therefore, there is a dire need to manage antibiotic-resistant bacteria-infected wounds effectively. NO participates in wound repairing and has antimicrobial properties, making it an excellent candidate for treating skin infections [134]. Due to the high prevalence of antibiotic-resistant bacteria, perhaps the most important aspect of using NO in infected wounds is the lack of NO-resistance bacteria to date [134]. Studies in both animals [135, 136] and humans [137] have shown the beneficial effects of NO as a new antimicrobial agent for treating infected wounds. However, fewer studies have been done on infected diabetic wounds. Table 3 summarizes results obtained from NO-based treatments on diabetic wound healing. Table 3. Nitric oxide (NO)-based therapeutic strategies for diabetic wound healing. Type of NO-Based Therapy

Type of Diabetes, Animal (STZ)

L-arginine

T1D, male Sprague-Dawley rats (STZ, 70 mg/kg)

Oral Incisional (gavage, 1 g/kg, ↑ Wound breaking wound twice daily, from strength (7 cm, dorsal day 3 before ↑ Wound fluid NOx skin) wounding)

[128]

L-arginine

T1D, male Sprague-Dawley rats (STZ, 70 mg/kg)

↑ Wound breaking strength IP injection ↑ Wound fluid (1 g/kg/day, hydroxyproline immediately content after wounding) ↑ Wound fluid NOx ↑ Expression of procollagen I and II

[46]

L-arginine

A laparotomy T1D, male mice model (STZ 60 mg/kg) procedure

Oral (gavage, 2 g/kg/day)

↑ Collagen deposition ↑ New blood vessel formation ↑ TGF-β expression

[140]

L-arginine

T1D, male mice (STZ 60 mg/kg)

Topical (10% and 15%)

↑ Collagen deposition ↑ New blood vessel formation

[140]

Type of Wound

Incisional wound (7 cm, dorsal skin)

A laparotomy model procedure

Route of Administration

Results

Ref.

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(Table ) cont.....

Type of NO-Based Therapy

Type of Diabetes, Animal (STZ)

Type of Wound

T1D, male mice Excisional (STZ 45 mg/kg wound Gene therapy of eNOS for 5 consecutive (1.5 ×1.5 cm, days) dorsal skin)

Incisional wound (7 cm, dorsal skin)

Route of Administration

Results

Ref.

Topical (placing 200 μL of viral solution directly onto the wound surface for 30 minutes, immediately after wounding)

↑ Wound closure rate ↑ Cutaneous eNOS protein expression and activity ↑ Cutaneous NOx level ↓ Superoxide level

[141]

Oral (gavage, 0.4 mg/kg/day)

↑ Wound breaking strength ↑ Wound fluid hydroxyproline content ↑ Wound fluid NOx ↑ Wound tissue eNOS expression

[45]

↑ eNOS expression in regenerated tissues ↑ NO synthesis in regenerated tissues ↑ Neovascularization ↑ Skin blood flow

[130]

↑ Wound closure rate

[27]

Pravastatin (a statin)

T1D, male Sprague-Dawley rats (STZ 70 mg/kg)

Statin-loaded tissue engineering scaffold

Excisional wound T1D, male Topical (a fullSprague-Dawley (immediately thickness rats round wound, after wounding) (STZ 45 mg/kg) 12 mm diameter).

Excisional wound Topical (a fullT2D, male mice Acidified nitrite cream (from day 2 after thickness (Lepr db/db) wounding) round wound, 12 mm diameter)

Acidified nitrite cream

T2D, male Wistar rats (STZ/HFD)

↑ Wound closure rate Improvement of Excisional inflammatory wound response (a fullTopical Augmentation of thickness (from day 3 after antioxidant defense round wound, wounding) ↑ Dermis 8 mm reconstruction diameter) ↑ Neovascularization ↑ Collagen deposition

[122, 123]

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(Table ) cont.....

Type of NO-Based Therapy

Chitosan-based NOreleasing (CS/NO) dressing

NO-releasing poly(vinyl alcohol) hydrogel dressings

Type of Diabetes, Animal (STZ)

Type of Wound

Route of Administration

Results

Excisional ↑ Biofilm dispersal wound Topical ↑ Wound sizeT1D, male mice (a full(from day 3 after reduction (40 mg/kg STZ thickness wounding, ↑ Epithelialization on 5 consecutive round wound, redressed every 3 rate days) 6 mm days) ↑ Collagen diameter) deposition

T2D, Female mice (db/db)

Excisional wound (a fullTopical thickness (redressed every round wound, 2-3 days) 15 mm diameter)

↑ Granular tissue thickness

Ref.

[148]

[146]

↓ Number of wound Excisional bacteria Improved wound Topical wound T1D SD male (a fullAsiaticoside (AC) NO (0.2 ml gel twice inflammatory rats thickness gel daily, from day 2 reaction (50 mg/kg STZ) round wound, after wounding) ↑ Expression of 18 mm VEGF, iNOS, and diameter) eNOS.

[149]

Excisional wound Topical T1D, Wistar rats (a fullGlyceryl trinitrate (twice daily, (either sex) thickness (GTN) ointment 0.2% from day 0 after (75 mg/kg STZ) round wound, wounding) 15 mm diameter)

↑ Re-epithelization

[150]

Excisional wound Topical T1D, Sprague(a full(20 mg of GSNO-PVMMA/PVP Dawley rats thickness complex powder complex powder (65 mg/kg STZ) round wound, applied on the 8 mm wound site) diameter)

↑ Wound closure rate

[151]

Two excisional wounds Topical T1D, male mice (a full(immediately (STZ 120 mg/kg) thickness after wounding) round wound, 4 mm diameter)

↑ Wound closure ↑ Antioxidant capacity ↑ Vascularization ↑ Fibroblasts formation ↑ Collagen synthesis

[152]

Bandage formulated with NO donor nanoparticles (NONPs)

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The Role of Nitric Oxide in Type 2 Diabetes 147

(Table ) cont.....

Type of NO-Based Therapy

Molsidomine (a NO donor)

Type of Diabetes, Animal (STZ)

Type of Wound

Route of Administration

Incisional Oral T1D, male Lewis wound (gavage, 1 rats (7 cm midline mg/kg, (STZ 70 mg/kg) dorsal skin) three times daily)

Results

Ref.

↑ Wound breaking strength ↑ Wound fluid hydroxyproline content ↑ MMP-2 activity

[77]

eNOS, endothelial NO synthase; GSNO-PVMMA/PVP, nitrosoglutathione- polyvinyl methyl ether-comaleic anhydride/polyvinyl pyrrolidone; iNOS, inducible NO synthase; IP, intraperitoneal; MMP, matrix metalloproteinase; NOx, nitric oxide metabolites; STZ, streptozotocin; T1D, type 1 diabetes; T2D, type 2 diabetes; TGF-β, transforming growth factor-β; VEGF, vascular endothelial growth factor; ↑, increase; ↓, decrease.

L-arginine Several researchers have demonstrated the beneficial effects of L-arginine (as a precursor of NO) on diabetic wound healing of both humans [138, 139] and animals [46, 128, 140]. L-arginine by increasing wound fluid NOx [46, 128], wound breaking strength [46, 128], collagen deposition [46, 140], and new blood vessel formation accelerates diabetic wound healing [140]. L-arginine has been used for the treatment of diabetic wounds through dietary supplementation [139, 140], topical application [140], IP injection [46], and subcutaneous injection [138]. Regulation of NOS Expression Regulating the expression and activity of different isoforms of NOS are strategies to increase NO production for diabetic wound treatment. NOS delivering to the wound site using a gene vector technique is one of these strategies. Luo et al. indicated that decreased eNOS protein and activity delayed wound healing in type 1 diabetic mice [141]. It has been reported that increased local NO bioavailability using cutaneous gene therapy of eNOS is an effective solution for improving wound healing by accelerating protein expression and activity of eNOS in diabetic mice [141]. Statins directly upregulate eNOS expression and increase NO biosynthesis and bioavailability [45, 130]. Laing et al., studying the effects of Pravastatin on wound healing in STZ-induced type 1 diabetic mice, indicated that it enhances wound breaking strength, promotes hydroxyproline accumulation, upregulates eNOS expression, and elevates wound fluid nitrite/nitrate levels [45]. It has also been shown that a statin-loaded tissue engineering scaffold (TES) recovers the high-glucose-induced decreases in cell viability and promotes NO synthesis in

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human umbilical vein endothelial cells (HUVECs) [130]. In STZ-induced type 1 diabetic rats, this statin-loaded TES structure promoted eNOS expression and NO synthesis in the regenerated tissues of the skin wound, accelerated neovascularization, and elevated skin blood flow and thus accelerated wound healing [130]. Extracorporeal shock-wave therapy (ESWT) also accelerates wound healing in STZ-induced type 1 diabetic male Wistar rats by increasing eNOS and VEGF expression, thereby increasing new blood vessel formation and blood perfusion [142]. Acidified Nitrite NO generation from acidified nitrite is a simple technique used for treating diabetic wounds. Effects of daily topical administration of acidified nitrite (3% sodium nitrate, 4.5% citric acid) on wound healing have been assessed in type 2 diabetic (Lepr db/db) male mice; results indicate that wound closure at day 18 after wounding was approximately 30% higher in the acidified nitrite-treated compared to the placebo group when administrated on day 2 after wounding [27]. Effects of topical acidified nitrite have also been evaluated on wound healing in type 2 diabetic rats induced by a combination of a high-fat diet (HFD) and lowdose STZ [122, 123]. Application of acidified nitrite from the third day after wounding increased wound closure rate and decreased time taken for 50% closure [122]. The beneficial effects of acidified nitrite on wound healing were independent of its systemic effects. They were associated with restoring delayed inflammatory response, accelerating dermis reconstruction, neovascularization, collagen deposition, and augmentation of antioxidant defense mechanisms [122, 123]. It has been shown that NO inhibits platelet aggregation and adhesion to the vascular endothelium via a cGMP-dependent manner [143 - 145], indicating the importance of the time of applying NO-based treatments for wound healing [27, 146]. Weller et al. reported that applying acidified nitrite (3.0% nitrite/4.5% citric acid) on the day of wounding immediately after injury impairs wound healing of incisional wounds due to platelet inhibition in normal mice [27]. However, acidified nitrite significantly accelerated wound healing when applied from day 3 after wounding (after the coagulation phase) [27]. In addition, the rate of wound closure decreased when an NO hydrogel dressing was used from the day of injury on a full-thickness excisional wound in type 2 diabetic mice [146]. NO Donor Systems NO donors have been used to treat diabetic wounds [147]. NO donors can be applied directly to wounds through their encapsulation in multitudes of NO donor systems and complexes such as dressings, gels, ointment, polymers, nanoparticles,

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and scaffolds [147]. NO generating systems have been developed to store and spontaneously release NO to wounds. Effect of chitosan-based NO-releasing (CS/NO) dressing was evaluated for methicillin-resistant staphylococcus aureus (MRSA) biofilm-infected wounds in type 1 diabetic mice [148]. CS/NO was used from day 3 to day 15 after wounding and were replaced with new dressings every 3 days. In MRSA biofilm-infected wounds, the CS/NO film-treated group was compared to untreated and CS filmtreated groups. There were faster biofilm dispersal, more wound size reduction, increased epithelialization rates, and collagen deposition [148]. Nie et al. assessed the effect of Asiaticoside (AC) NO gel on a cutaneous wound of diabetic SD male rats [149]. AC is extracted from the traditional Chinese medicine, Centella Asiatica. AC + NO gel was used from day 2 after wounding to day 14 after wounding. Results indicated that compared to untreated diabetic rats, the number of bacteria in the wound of rats was lower in the AC + NO treated rats at days 3 and 7 after wounding. In addition, AC + NO gel improved the inflammatory response and increased expressions of VEGF, iNOS, and eNOS [149]. Ghori et al. assessed the effect of a topical NO donor, 0.2% glyceryl trinitrate (GTN) ointment, on different models of wounds (excision wound and incision wound) in type 1 diabetic Wistar rats [150]. The result indicated that the percentage of re-epithelization at day 11 after wounding was significantly higher in the 0.2% GTN ointment-treated group. however, there was no significant effect on the excision wound closure rate. GTN treatment had no significant effect on mean breaking strength, granular tissue, and hydroxyproline content of healed resutured incision wounds at day 11 after wounding. GTN treatment had no impact on polymorphonuclear cell infiltration, macrophage, fibroblast, or neoangiogenesis at day 11 after wounding, suggesting that NO did not affect granular tissue formation or maturation in this particular study setup [150]. Li and Lee assessed the effects of GSNO-PVMMA/PVP complex powder (nitrosoglutathione- polyvinyl methyl ether-co-maleic anhydride/polyvinyl pyrrolidone) as a polymeric NO donor on the full-thickness wound healing in type 1 diabetic rats [151]. This complex released NO under ambient light conditions for 10 days. For treatment, after wound induction, 20 mg of GSNOPVMMA/PVP complex powder was applied to the wound site and quickly adhered to the wound tissue with the addition of two drops of sterile saline. Then wounds were covered with transparent Tegaderm dressings. The result indicated that GSNO-PVMMA/PVP complex significantly accelerated wound closure rate at days 4, 7, and 10 after wounding, whereas the difference became less signific-

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ant on days 13 and 16. This may be related to the fact that NO release from this complex generally lasts only up to 10 days [151]. CONCLUDING REMARKS Insufficient NO in diabetic wounds seems to be a major contributor to the impairment of diabetic wound healing. NO-based therapies could be considered treatment modalities that can have many beneficial effects on diabetic wound healing. NO has an antibacterial effect, regulates inflammation, increases cell proliferation, and stimulates new blood vessel formation and collagen deposition; all of these effects are potentially promising for treating diabetic wounds and because NO is a short-lived gas molecule, maintaining an adequate NO level at the wound site is an evident problem for the treatment of diabetic wounds. Numerous studies have been performed to design a suitable NO-based device. Despite the high prevalence of diabetic ulcers in T2D, most of them have been investigated in animal models of T1D, indicating the need for further investigation in type 2 diabetic models and the need for verification in clinical trials. CONSENT FOR PUBLICATION Not applicable. CONFLICT OF INTEREST The author declares no conflict of interest, financial or otherwise. ACKNOWLEDGEMENT Declared none. REFERENCES [1]

Cho NH, Shaw JE, Karuranga S, et al. IDF Diabetes Atlas: Global estimates of diabetes prevalence for 2017 and projections for 2045. Diabetes Res Clin Pract 2018; 138: 271-81. [http://dx.doi.org/10.1016/j.diabres.2018.02.023] [PMID: 29496507]

[2]

Vileikyte L. Diabetic foot ulcers: a quality of life issue. Diabetes Metab Res Rev 2001; 17(4): 246-9. [http://dx.doi.org/10.1002/dmrr.216] [PMID: 11544609]

[3]

Zhang P, Lu J, Jing Y, Tang S, Zhu D, Bi Y. Global epidemiology of diabetic foot ulceration: a systematic review and meta-analysis. Ann Med 2017; 49(2): 106-16. [http://dx.doi.org/10.1080/07853890.2016.1231932] [PMID: 27585063]

[4]

Alavi A, Sibbald RG, Mayer D, et al. Diabetic foot ulcers. J Am Acad Dermatol 2014; 70(1): 1.e11.e18. [http://dx.doi.org/10.1016/j.jaad.2013.06.055] [PMID: 24355275]

[5]

Iversen MM, Tell GS, Riise T, et al. History of foot ulcer increases mortality among individuals with

NO and Diabetic Wound Healing

The Role of Nitric Oxide in Type 2 Diabetes 151

diabetes: ten-year follow-up of the Nord-Trøndelag Health Study, Norway. Diabetes Care 2009; 32(12): 2193-9. [http://dx.doi.org/10.2337/dc09-0651] [PMID: 19729524] [6]

Moxey PW, Gogalniceanu P, Hinchliffe RJ, et al. Lower extremity amputations - a review of global variability in incidence. Diabet Med 2011; 28(10): 1144-53. [http://dx.doi.org/10.1111/j.1464-5491.2011.03279.x] [PMID: 21388445]

[7]

Driver VR, Fabbi M, Lavery LA, Gibbons G. The costs of diabetic foot: The economic case for the limb salvage team. J Vasc Surg 2010; 52(3) (Suppl.): 17S-22S. [http://dx.doi.org/10.1016/j.jvs.2010.06.003] [PMID: 20804928]

[8]

Boulton AJM, Vileikyte L, Ragnarson-Tennvall G, Apelqvist J. The global burden of diabetic foot disease. Lancet 2005; 366(9498): 1719-24. [http://dx.doi.org/10.1016/S0140-6736(05)67698-2] [PMID: 16291066]

[9]

Game FL, Apelqvist J, Attinger C, et al. IWGDF guidance on use of interventions to enhance the healing of chronic ulcers of the foot in diabetes. Diabetes Metab Res Rev 2016; 32 (Suppl. 1): 75-83. [http://dx.doi.org/10.1002/dmrr.2700] [PMID: 26340818]

[10]

Everett E, Mathioudakis N. Update on management of diabetic foot ulcers. Ann N Y Acad Sci 2018; 1411(1): 153-65. [http://dx.doi.org/10.1111/nyas.13569] [PMID: 29377202]

[11]

Margolis DJ, Kantor J, Berlin JA. Healing of diabetic neuropathic foot ulcers receiving standard treatment. A meta-analysis. Diabetes Care 1999; 22(5): 692-5. [http://dx.doi.org/10.2337/diacare.22.5.692] [PMID: 10332667]

[12]

Fu XL, Ding H, Miao WW, Mao CX, Zhan MQ, Chen HL. Global recurrence rates in diabetic foot ulcers: A systematic review and meta-analysis. Diabetes Metab Res Rev 2019; 35(6): e3160. [http://dx.doi.org/10.1002/dmrr.3160] [PMID: 30916434]

[13]

Cals-Grierson MM, Ormerod AD. Nitric oxide function in the skin. 2004; 10(4): 179-93. [http://dx.doi.org/10.1016/j.niox.2004.04.005]

[14]

Luo J, Chen AF. Nitric oxide: a newly discovered function on wound healing. Acta Pharmacol Sin 2005; 26(3): 259-64. [http://dx.doi.org/10.1111/j.1745-7254.2005.00058.x] [PMID: 15715920]

[15]

Witte MB, Barbul A. Role of nitric oxide in wound repair. Am J Surg 2002; 183(4): 406-12. [http://dx.doi.org/10.1016/S0002-9610(02)00815-2] [PMID: 11975928]

[16]

Frank S, Kämpfer H, Wetzler C, Pfeilschifter J. Nitric oxide drives skin repair: Novel functions of an established mediator. Kidney Int 2002; 61(3): 882-8. [http://dx.doi.org/10.1046/j.1523-1755.2002.00237.x] [PMID: 11849442]

[17]

Stancic A, Jankovic A, Korac A, Buzadzic B, Otasevic V, Korac B. The role of nitric oxide in diabetic skin (patho) physiology. Mech Ageing Dev 2017; 30(3): 11-9. [PMID: 28865932]

[18]

Young A, McNaught CE. The physiology of wound healing. Surgery 2011; 29(10): 475-9. [http://dx.doi.org/10.1016/j.mpsur.2011.06.011]

[19]

Velnar T, Bailey T, Smrkolj V. The wound healing process: an overview of the cellular and molecular mechanisms. J Int Med Res 2009; 37(5): 1528-42. [http://dx.doi.org/10.1177/147323000903700531] [PMID: 19930861]

[20]

Malone-Povolny MJ, Maloney SE, Schoenfisch MH. Nitric Oxide Therapy for Diabetic Wound Healing 2019; 8(12): e1801210.

[21]

Lazarus GS, Cooper DM, Knighton DR, et al. Definitions and guidelines for assessment of wounds and evaluation of healing. Wound Repair Regen 1994; 2(3): 165-70. [http://dx.doi.org/10.1046/j.1524-475X.1994.20305.x] [PMID: 17156107]

152 The Role of Nitric Oxide in Type 2 Diabetes

Afzali et al.

[22]

Demidova-Rice TN, Hamblin MR, Herman IM. Acute and impaired wound healing: pathophysiology and current methods for drug delivery, part 1: normal and chronic wounds: biology, causes, and approaches to care. Adv Skin Wound Care 2012; 25(7): 304-14. [http://dx.doi.org/10.1097/01.ASW.0000416006.55218.d0] [PMID: 22713781]

[23]

Noor S, Zubair M, Ahmad J. Diabetic foot ulcer—A review on pathophysiology, classification and microbial etiology. Diabetes Metab Syndr 2015; 9(3): 192-9. [http://dx.doi.org/10.1016/j.dsx.2015.04.007] [PMID: 25982677]

[24]

Tresierra-Ayala MÁ, García Rojas A. Association between peripheral arterial disease and diabetic foot ulcers in patients with diabetes mellitus type 2. Medicina Universitaria 2017; 19(76): 123-6. [http://dx.doi.org/10.1016/j.rmu.2017.07.002]

[25]

Veves A, Akbari CM, Primavera J, et al. Endothelial dysfunction and the expression of endothelial nitric oxide synthetase in diabetic neuropathy, vascular disease, and foot ulceration. Diabetes 1998; 47(3): 457-63. [http://dx.doi.org/10.2337/diabetes.47.3.457] [PMID: 9519754]

[26]

Association AD. Peripheral arterial disease in people with diabetes. Diabetes Care 2003; 26(12): 333341. [http://dx.doi.org/10.2337/diacare.26.12.3333] [PMID: 14633825]

[27]

Weller R, Finnen MJ. The effects of topical treatment with acidified nitrite on wound healing in normal and diabetic mice. Nitric Oxide 2006; 15(4): 395-9. [http://dx.doi.org/10.1016/j.niox.2006.04.002] [PMID: 16731016]

[28]

Barman PK, Koh TJ. Macrophage Dysregulation and Impaired Skin Wound Healing in Diabetes. Front Cell Dev Biol 2020; 8: 528. [http://dx.doi.org/10.3389/fcell.2020.00528] [PMID: 32671072]

[29]

Rousselle P, Braye F, Dayan G. Re-epithelialization of adult skin wounds: Cellular mechanisms and therapeutic strategies. Adv Drug Deliv Rev 2019; 146: 344-65. [http://dx.doi.org/10.1016/j.addr.2018.06.019] [PMID: 29981800]

[30]

Reinke JM, Sorg H. Wound repair and regeneration. Eur Surg Res 2012; 49(1): 35-43. [http://dx.doi.org/10.1159/000339613] [PMID: 22797712]

[31]

Johnson KE, Wilgus TA. Vascular Endothelial Growth Factor and Angiogenesis in the Regulation of Cutaneous Wound Repair. Adv Wound Care (New Rochelle) 2014; 3(10): 647-61. [http://dx.doi.org/10.1089/wound.2013.0517] [PMID: 25302139]

[32]

Rangaraj A, Harding K, Leaper D. Role of collagen in wound management. Wounds uk 2011; 7(2): 54-63.

[33]

Kunkemoeller B, Kyriakides TR. Redox Signaling in Diabetic Wound Healing Regulates Extracellular Matrix Deposition. Antioxid Redox Signal 2017; 27(12): 823-38. [http://dx.doi.org/10.1089/ars.2017.7263] [PMID: 28699352]

[34]

Baltzis D, Eleftheriadou I, Veves A. Pathogenesis and treatment of impaired wound healing in diabetes mellitus: new insights. Adv Ther 2014; 31(8): 817-36. [http://dx.doi.org/10.1007/s12325-014-0140-x] [PMID: 25069580]

[35]

Usui ML, Mansbridge JN, Carter WG, Fujita M, Olerud JE. Keratinocyte migration, proliferation, and differentiation in chronic ulcers from patients with diabetes and normal wounds. J Histochem Cytochem 2008; 56(7): 687-96. [http://dx.doi.org/10.1369/jhc.2008.951194] [PMID: 18413645]

[36]

McLaughlin PJ, Immonen JA, Zagon IS. Topical naltrexone accelerates full-thickness wound closure in type 1 diabetic rats by stimulating angiogenesis. Exp Biol Med (Maywood) 2013; 238(7): 733-43. [http://dx.doi.org/10.1177/1535370213492688] [PMID: 23788174]

[37]

Jacobi J, Jang JJ, Sundram U, Dayoub H, Fajardo LF, Cooke JP. Nicotine accelerates angiogenesis and

NO and Diabetic Wound Healing

The Role of Nitric Oxide in Type 2 Diabetes 153

wound healing in genetically diabetic mice. Am J Pathol 2002; 161(1): 97-104. [http://dx.doi.org/10.1016/S0002-9440(10)64161-2] [PMID: 12107094] [38]

Stallmeyer B, Anhold M, Wetzler C, Kahlina K, Pfeilschifter J, Frank S. Regulation of eNOS in normal and diabetes-impaired skin repair: implications for tissue regeneration. Nitric Oxide 2002; 6(2): 168-77. [http://dx.doi.org/10.1006/niox.2001.0407] [PMID: 11890741]

[39]

Teixeira AS, Andrade SP. Glucose-induced inhibition of angiogenesis in the rat sponge granuloma is prevented by aminoguanidine. Life Sci 1999; 64(8): 655-62. [http://dx.doi.org/10.1016/S0024-3205(98)00607-9] [PMID: 10069528]

[40]

Greenhalgh DG, Sprugel KH, Murray MJ, Ross R. PDGF and FGF stimulate wound healing in the genetically diabetic mouse. Am J Pathol 1990; 136(6): 1235-46. [PMID: 2356856]

[41]

Bitto A, Irrera N, Pizzino G, et al. Activation of the EPOR-β common receptor complex by cibinetide ameliorates impaired wound healing in mice with genetic diabetes. Biochim Biophys Acta Mol Basis Dis 2018; 1864(2): 632-9. [http://dx.doi.org/10.1016/j.bbadis.2017.12.006] [PMID: 29223734]

[42]

Tan WS, Arulselvan P, Ng SF, Mat Taib CN, Sarian MN, Fakurazi S. Improvement of diabetic wound healing by topical application of Vicenin-2 hydrocolloid film on Sprague Dawley rats. BMC Complement Altern Med 2019; 19(1): 20. [http://dx.doi.org/10.1186/s12906-018-2427-y] [PMID: 30654793]

[43]

Lerman OZ, Galiano RD, Armour M, Levine JP, Gurtner GC. Cellular dysfunction in the diabetic fibroblast: impairment in migration, vascular endothelial growth factor production, and response to hypoxia. Am J Pathol 2003; 162(1): 303-12. [http://dx.doi.org/10.1016/S0002-9440(10)63821-7] [PMID: 12507913]

[44]

Black E, Vibe-Petersen J, Jorgensen LN, et al. Decrease of collagen deposition in wound repair in type 1 diabetes independent of glycemic control. Arch Surg 2003; 138(1): 34-40. [http://dx.doi.org/10.1001/archsurg.138.1.34] [PMID: 12511146]

[45]

Laing T, Hanson R, Chan F, Bouchier-Hayes D. Effect of pravastatin on experimental diabetic wound healing. J Surg Res 2010; 161(2): 336-40. [http://dx.doi.org/10.1016/j.jss.2009.01.024] [PMID: 20031169]

[46]

Shi HP, Most D, Efron DT, Witte MB, Barbul A. Supplemental L-arginine enhances wound healing in diabetic rats. Wound repair and regeneration : official publication of the Wound Healing Society [and] the European Tissue Repair Society 2003; 11(3): 198-203.

[47]

Lobmann R, Ambrosch A, Schultz G, Waldmann K, Schiweck S, Lehnert H. Expression of matrixmetalloproteinases and their inhibitors in the wounds of diabetic and non-diabetic patients. Diabetologia 2002; 45(7): 1011-6. [http://dx.doi.org/10.1007/s00125-002-0868-8] [PMID: 12136400]

[48]

Wall SJ, Bevan D, Thomas DW, Harding KG, Edwards DR, Murphy G. Differential expression of matrix metalloproteinases during impaired wound healing of the diabetes mouse. J Invest Dermatol 2002; 119(1): 91-8. [http://dx.doi.org/10.1046/j.1523-1747.2002.01779.x] [PMID: 12164930]

[49]

Slavkovsky R, Kohlerova R, Tkacova V, Jiroutova A, Tahmazoglu B, Velebny V, et al. Zucker diabetic fatty rat: a new model of impaired cutaneous wound repair with type II diabetes mellitus and obesity. Wound repair and regeneration : official publication of the Wound Healing Society [and] the European Tissue Repair Society 2011; 19(4): 515-25. [http://dx.doi.org/10.1111/j.1524-475X.2011.00703.x]

[50]

Minossi JG, Lima FO, Caramori CA, et al. Alloxan diabetes alters the tensile strength, morphological and morphometric parameters of abdominal wall healing in rats. Acta Cir Bras 2014; 29(2): 118-24. [http://dx.doi.org/10.1590/S0102-86502014000200008] [PMID: 24604316]

154 The Role of Nitric Oxide in Type 2 Diabetes

Afzali et al.

[51]

Wolf R, Schönfelder G, Paul M, Blume-Peytavi U. Nitric oxide in the human hair follicle: constitutive and dihydrotestosterone-induced nitric oxide synthase expression and NO production in dermal papilla cells. J Mol Med (Berl) 2003; 81(2): 110-7. [http://dx.doi.org/10.1007/s00109-002-0402-y] [PMID: 12601527]

[52]

Weller R, Pattullo S, Smith L, Golden M, Ormerod A, Benjamin N. Nitric oxide is generated on the skin surface by reduction of sweat nitrate. J Invest Dermatol 1996; 107(3): 327-31. [http://dx.doi.org/10.1111/1523-1747.ep12363167] [PMID: 8751965]

[53]

Paunel AN, Dejam A, Thelen S, et al. Enzyme-independent nitric oxide formation during UVA challenge of human skin: characterization, molecular sources, and mechanisms. Free Radic Biol Med 2005; 38(5): 606-15. [http://dx.doi.org/10.1016/j.freeradbiomed.2004.11.018] [PMID: 15683717]

[54]

Opländer C, Suschek C. The role of photolabile dermal nitric oxide derivates in ultraviolet radiation (UVR)-induced cell death. Int J Mol Sci 2012; 14(1): 191-204. [http://dx.doi.org/10.3390/ijms14010191] [PMID: 23344028]

[55]

Sharp A, Clark J. Diabetes and its effects on wound healing. Nursing standard (Royal College of Nursing (Great Britain). 2011; 25: pp. (45)41-7.

[56]

Jackson M, Frame F, Weller R, McKenzie RC. Expression of nitric oxide synthase III (eNOS) mRNA by human skin cells: melanocytes but not keratinocytes express eNOS mRNA. Arch Dermatol Res 1998; 290(6): 350-2. [http://dx.doi.org/10.1007/s004030050316] [PMID: 9705168]

[57]

Shimizu Y, Sakai M, Umemura Y, Ueda H. Immunohistochemical localization of nitric oxide synthase in normal human skin: expression of endothelial-type and inducible-type nitric oxide synthase in keratinocytes. J Dermatol 1997; 24(2): 80-7. [http://dx.doi.org/10.1111/j.1346-8138.1997.tb02748.x] [PMID: 9065701]

[58]

Sakai M, Shimizu Y, Nagatsu I, Ueda H. Immunohistochemical localization of NO synthases in normal human skin and psoriatic skin. Arch Dermatol Res 1996; 288(10): 625-7. [http://dx.doi.org/10.1007/BF02505267] [PMID: 8919047]

[59]

Ivanova K, Le Poole IC, Gerzer R, Westerhof W, Das PK. Effects of nitric oxide on the adhesion of human melanocytes to extracellular matrix components. The Journal of Pathology: A Journal of the Pathological Society of Great Britain and Ireland 1997; 183(4): 469-76. [http://dx.doi.org/10.1002/(SICI)1096-9896(199712)183:43.0.CO;2-T]

[60]

Baudouin JE, Tachon P. Constitutive nitric oxide synthase is present in normal human keratinocytes. J Invest Dermatol 1996; 106(3): 428-31. [http://dx.doi.org/10.1111/1523-1747.ep12343523] [PMID: 8648171]

[61]

Cals-Grierson MM, Ormerod AD. Nitric oxide function in the skin. Nitric Oxide 2004; 10(4): 179-93. [http://dx.doi.org/10.1016/j.niox.2004.04.005] [PMID: 15275864]

[62]

Suschek CV, Briviba K, Bruch-Gerharz D, Sies H, Kröncke KD, Kolb-Bachofen V. Even after UVAexposure will nitric oxide protect cells from reactive oxygen intermediate-mediated apoptosis and necrosis. Cell Death Differ 2001; 8(5): 515-27. [http://dx.doi.org/10.1038/sj.cdd.4400839] [PMID: 11423912]

[63]

Mowbray M, McLintock S, Weerakoon R, et al. Enzyme-independent NO stores in human skin: quantification and influence of UV radiation. J Invest Dermatol 2009; 129(4): 834-42. [http://dx.doi.org/10.1038/jid.2008.296] [PMID: 18818674]

[64]

Whitlock DR, Feelisch M. Soil bacteria, nitrite and the skin The Hygiene Hypothesis and Darwinian Medicine. Springer 2009; pp. 103-15. [http://dx.doi.org/10.1007/978-3-7643-8903-1_6]

[65]

Notay M, Saric-Bosanac S, Vaughn AR, et al. The use of topical Nitrosomonas eutropha for cosmetic improvement of facial wrinkles. J Cosmet Dermatol 2020; 19(3): 689-93.

NO and Diabetic Wound Healing

The Role of Nitric Oxide in Type 2 Diabetes 155

[http://dx.doi.org/10.1111/jocd.13060] [PMID: 31257694] [66]

D’Orazio J, Jarrett S, Amaro-Ortiz A, Scott T. UV radiation and the skin. Int J Mol Sci 2013; 14(6): 12222-48. [http://dx.doi.org/10.3390/ijms140612222] [PMID: 23749111]

[67]

Seifter E, Rettura G, Barbul A, Levenson SM. Arginine: an essential amino acid for injured rats. Surgery 1978; 84(2): 224-30. [PMID: 684614]

[68]

Barbul A, Rettura G, Levenson SM, Seifter E. Wound healing and thymotropic effects of arginine: a pituitary mechanism of action. Am J Clin Nutr 1983; 37(5): 786-94. [http://dx.doi.org/10.1093/ajcn/37.5.786] [PMID: 6846217]

[69]

Nussbaum MS. Arginine stimulates wound healing and immune function in elderly human beings. JPEN J Parenter Enteral Nutr 1994; 18(2): 194. [http://dx.doi.org/10.1177/0148607194018002194] [PMID: 8201760]

[70]

Stechmiller JK, Childress B, Cowan L. Arginine supplementation and wound healing. Nutrition in clinical practice : official publication of the American Society for Parenteral and Enteral Nutrition 2005; 20(1): 52-61. [http://dx.doi.org/10.1177/011542650502000152]

[71]

Shi HP, Efron DT, Most D, Tantry US, Barbul A. Supplemental dietary arginine enhances wound healing in normal but not inducible nitric oxide synthase knockout mice. Surgery 2000; 128(2): 374-8. [http://dx.doi.org/10.1067/msy.2000.107372] [PMID: 10923019]

[72]

Dunphy M. The influence of wound healing of urinary Nitrate levels in Rats. Wounds 1991; 3: 50-8.

[73]

Schäffer MR, Tantry U, van Wesep RA, Barbul A. Nitric oxide metabolism in wounds. J Surg Res 1997; 71(1): 25-31. [http://dx.doi.org/10.1006/jsre.1997.5137] [PMID: 9271274]

[74]

Albina JE, Mills CD, Henry WL Jr, Caldwell MD. Temporal expression of different pathways of 1arginine metabolism in healing wounds. Journal of immunology (Baltimore, Md : 1950) 1990; 144(10): 3877-80.

[75]

Boykin JV Jr. Wound nitric oxide bioactivity: a promising diagnostic indicator for diabetic foot ulcer management.Journal of wound, ostomy, and continence nursing : official publication of The Wound, Ostomy and Continence Nurses Society 2010; 37(1): 25-32. [http://dx.doi.org/10.1097/WON.0b013e3181c68b61]

[76]

Schäffer MR, Tantry U, Efron PA, Ahrendt GM, Thornton FJ, Barbul A. Diabetes-impaired healing and reduced wound nitric oxide synthesis: A possible pathophysiologic correlation. Surgery 1997; 121(5): 513-9. [http://dx.doi.org/10.1016/S0039-6060(97)90105-7] [PMID: 9142149]

[77]

Witte MB, Kiyama T, Barbul A. Nitric oxide enhances experimental wound healing in diabetes. Br J Surg 2002; 89(12): 1594-601. [http://dx.doi.org/10.1046/j.1365-2168.2002.02263.x] [PMID: 12445072]

[78]

Tatmatsu-Rocha JC, Ferraresi C, Hamblin MR, et al. Low-level laser therapy (904nm) can increase collagen and reduce oxidative and nitrosative stress in diabetic wounded mouse skin. J Photochem Photobiol B 2016; 164: 96-102. [http://dx.doi.org/10.1016/j.jphotobiol.2016.09.017] [PMID: 27661759]

[79]

Rassaf T, Bryan NS, Kelm M, Feelisch M. Concomitant presence of N-nitroso and S-nitroso proteins in human plasma. Free Radic Biol Med 2002; 33(11): 1590-6. [http://dx.doi.org/10.1016/S0891-5849(02)01183-8] [PMID: 12446216]

[80]

Krzyszczyk P, Schloss R, Palmer A, Berthiaume F. The Role of Macrophages in Acute and Chronic Wound Healing and Interventions to Promote Pro-wound Healing Phenotypes. Front Physiol 2018; 9: 419.

156 The Role of Nitric Oxide in Type 2 Diabetes

Afzali et al.

[http://dx.doi.org/10.3389/fphys.2018.00419] [PMID: 29765329] [81]

Daley JM, Brancato SK, Thomay AA, Reichner JS, Albina JE. The phenotype of murine wound macrophages. J Leukoc Biol 2010; 87(1): 59-67. [http://dx.doi.org/10.1189/jlb.0409236] [PMID: 20052800]

[82]

Hesketh M, Sahin KB, West ZE, Murray RZ. Macrophage Phenotypes Regulate Scar Formation and Chronic Wound Healing. Int J Mol Sci 2017; 18(7): 1545. [http://dx.doi.org/10.3390/ijms18071545] [PMID: 28714933]

[83]

Xue Q, Yan Y, Zhang R, Xiong H. Regulation of iNOS on Immune Cells and Its Role in Diseases. Int J Mol Sci 2018; 19(12): 3805. [http://dx.doi.org/10.3390/ijms19123805] [PMID: 30501075]

[84]

Kloc M, Ghobrial RM, Wosik J, Lewicka A, Lewicki S, Kubiak JZ. Macrophage functions in wound healing. J Tissue Eng Regen Med 2019; 13(1): 99-109. [PMID: 30445662]

[85]

Xiong H, Zhu C, Li F, et al. Inhibition of interleukin-12 p40 transcription and NF-kappaB activation by nitric oxide in murine macrophages and dendritic cells. J Biol Chem 2004; 279(11): 10776-83. [http://dx.doi.org/10.1074/jbc.M313416200] [PMID: 14679201]

[86]

Lu G, Zhang R, Geng S, et al. Myeloid cell-derived inducible nitric oxide synthase suppresses M1 macrophage polarization. Nat Commun 2015; 6(1): 6676. [http://dx.doi.org/10.1038/ncomms7676] [PMID: 25813085]

[87]

Giordano D, Li C, Suthar MS, et al. Nitric oxide controls an inflammatory-like Ly6C hi PDCA1 + DC subset that regulates Th1 immune responses. J Leukoc Biol 2011; 89(3): 443-55. [http://dx.doi.org/10.1189/jlb.0610329] [PMID: 21178115]

[88]

Zhou J, Dehne N, Brüne B. Nitric oxide causes macrophage migration via the HIF-1-stimulated small GTPases Cdc42 and Rac1. Free Radic Biol Med 2009; 47(6): 741-9. [http://dx.doi.org/10.1016/j.freeradbiomed.2009.06.006] [PMID: 19523512]

[89]

Kitano T, Yamada H, Kida M, Okada Y, Saika S, Yoshida M. Impaired Healing of a Cutaneous Wound in an Inducible Nitric Oxide Synthase-Knockout Mouse. Dermatol Res Pract 2017; 2017: 111. [http://dx.doi.org/10.1155/2017/2184040] [PMID: 28487726]

[90]

Ormerod AD, Copeland P, Hay I, Husain A, Ewen SWB. The inflammatory and cytotoxic effects of a nitric oxide releasing cream on normal skin. J Invest Dermatol 1999; 113(3): 392-7. [http://dx.doi.org/10.1046/j.1523-1747.1999.00692.x] [PMID: 10469339]

[91]

Han G, Nguyen LN, Macherla C, et al. Nitric oxide-releasing nanoparticles accelerate wound healing by promoting fibroblast migration and collagen deposition. Am J Pathol 2012; 180(4): 1465-73. [http://dx.doi.org/10.1016/j.ajpath.2011.12.013] [PMID: 22306734]

[92]

Tümer C, Bilgin H, Obay B, Diken H, Atmaca M, Kelle M. Effect of nitric oxide on phagocytic activity of lipopolysaccharide-induced macrophages: Possible role of exogenous l-arginine. Cell Biol Int 2007; 31(6): 565-9. [http://dx.doi.org/10.1016/j.cellbi.2006.11.029] [PMID: 17241792]

[93]

Schairer DO, Chouake JS, Nosanchuk JD, Friedman AJ. The potential of nitric oxide releasing therapies as antimicrobial agents. Virulence 2012; 3(3): 271-9. [http://dx.doi.org/10.4161/viru.20328] [PMID: 22546899]

[94]

Fang FC. Perspectives series: host/pathogen interactions. Mechanisms of nitric oxide-related antimicrobial activity. J Clin Invest 1997; 99(12): 2818-25. [http://dx.doi.org/10.1172/JCI119473] [PMID: 9185502]

[95]

Jones ML, Ganopolsky JG, Labbé A, Wahl C, Prakash S. Antimicrobial properties of nitric oxide and its application in antimicrobial formulations and medical devices. Appl Microbiol Biotechnol 2010; 88(2): 401-7.

NO and Diabetic Wound Healing

The Role of Nitric Oxide in Type 2 Diabetes 157

[http://dx.doi.org/10.1007/s00253-010-2733-x] [PMID: 20680266] [96]

Morbidelli L, Donnini S, Ziche M. Role of nitric oxide in the modulation of angiogenesis. Curr Pharm Des 2003; 9(7): 521-30. [http://dx.doi.org/10.2174/1381612033391405] [PMID: 12570800]

[97]

Sharifpanah F, Behr S, Wartenberg M, Sauer H. Mechanical strain stimulates vasculogenesis and expression of angiogenesis guidance molecules of embryonic stem cells through elevation of intracellular calcium, reactive oxygen species and nitric oxide generation. Biochim Biophys Acta Mol Cell Res 2016; 1863(12): 3096-105. [http://dx.doi.org/10.1016/j.bbamcr.2016.10.001] [PMID: 27725190]

[98]

Bauer SM, Goldstein LJ, Bauer RJ, Chen H, Putt M, Velazquez OC. The bone marrow-derived endothelial progenitor cell response is impaired in delayed wound healing from ischemia. J Vasc Surg 2006; 43(1): 134-41. [http://dx.doi.org/10.1016/j.jvs.2005.08.038] [PMID: 16414400]

[99]

Loomans CJM, de Koning EJP, Staal FJT, et al. Endothelial progenitor cell dysfunction: a novel concept in the pathogenesis of vascular complications of type 1 diabetes. Diabetes 2004; 53(1): 195-9. [http://dx.doi.org/10.2337/diabetes.53.1.195] [PMID: 14693715]

[100] Tepper OM, Galiano RD, Capla JM, et al. Human endothelial progenitor cells from type II diabetics exhibit impaired proliferation, adhesion, and incorporation into vascular structures. Circulation 2002; 106(22): 2781-6. [http://dx.doi.org/10.1161/01.CIR.0000039526.42991.93] [PMID: 12451003] [101] Aicher A, Heeschen C, Mildner-Rihm C, et al. Essential role of endothelial nitric oxide synthase for mobilization of stem and progenitor cells. Nat Med 2003; 9(11): 1370-6. [http://dx.doi.org/10.1038/nm948] [PMID: 14556003] [102] Elson DA, Ryan HE, Snow JW, Johnson R, Arbeit JM. Coordinate up-regulation of hypoxia inducible factor (HIF)-1alpha and HIF-1 target genes during multi-stage epidermal carcinogenesis and wound healing. Cancer Res 2000; 60(21): 6189-95. [PMID: 11085544] [103] Falanga V. Wound healing and its impairment in the diabetic foot. Lancet 2005; 366(9498): 1736-43. [http://dx.doi.org/10.1016/S0140-6736(05)67700-8] [PMID: 16291068] [104] Ahluwalia A, Tarnawski AS. Critical role of hypoxia sensor--HIF-1α in VEGF gene activation. Implications for angiogenesis and tissue injury healing. Curr Med Chem 2012; 19(1): 90-7. [http://dx.doi.org/10.2174/092986712803413944] [PMID: 22300081] [105] Steinbrech DS, Mehrara BJ, Chau D, et al. Hypoxia upregulates VEGF production in keloid fibroblasts. Ann Plast Surg 1999; 42(5): 514-20. [http://dx.doi.org/10.1097/00000637-199905000-00009] [PMID: 10340860] [106] Rossiter H, Barresi C, Pammer J, et al. Loss of vascular endothelial growth factor a activity in murine epidermal keratinocytes delays wound healing and inhibits tumor formation. Cancer Res 2004; 64(10): 3508-16. [http://dx.doi.org/10.1158/0008-5472.CAN-03-2581] [PMID: 15150105] [107] Brown LF, Yeo KT, Berse B, et al. Expression of vascular permeability factor (vascular endothelial growth factor) by epidermal keratinocytes during wound healing. J Exp Med 1992; 176(5): 1375-9. [http://dx.doi.org/10.1084/jem.176.5.1375] [PMID: 1402682] [108] Heissig B, Hattori K, Dias S, et al. Recruitment of stem and progenitor cells from the bone marrow niche requires MMP-9 mediated release of kit-ligand. Cell 2002; 109(5): 625-37. [http://dx.doi.org/10.1016/S0092-8674(02)00754-7] [PMID: 12062105] [109] Goldstein LJ, Gallagher KA, Bauer SM, et al. Endothelial progenitor cell release into circulation is triggered by hyperoxia-induced increases in bone marrow nitric oxide. Stem Cells 2006; 24(10): 230918.

158 The Role of Nitric Oxide in Type 2 Diabetes

Afzali et al.

[http://dx.doi.org/10.1634/stemcells.2006-0010] [PMID: 16794267] [110] Ceradini DJ, Kulkarni AR, Callaghan MJ, et al. Progenitor cell trafficking is regulated by hypoxic gradients through HIF-1 induction of SDF-1. Nat Med 2004; 10(8): 858-64. [http://dx.doi.org/10.1038/nm1075] [PMID: 15235597] [111] Okonkwo U, DiPietro L. Diabetes and Wound Angiogenesis. Int J Mol Sci 2017; 18(7): 1419. [http://dx.doi.org/10.3390/ijms18071419] [PMID: 28671607] [112] Carmeliet P. Mechanisms of angiogenesis and arteriogenesis. Nat Med 2000; 6(4): 389-95. [http://dx.doi.org/10.1038/74651] [PMID: 10742145] [113] Ziche M, Morbidelli L. Nitric oxide and angiogenesis. J Neurooncol 2000; 50(1/2): 139-48. [http://dx.doi.org/10.1023/A:1006431309841] [PMID: 11245273] [114] Lee PC, Salyapongse AN, Bragdon GA, et al. Impaired wound healing and angiogenesis in eNOSdeficient mice. Am J Physiol 1999; 277(4): H1600-8. [PMID: 10516200] [115] Chin LC, Kumar P, Palmer JA, et al. The influence of nitric oxide synthase 2 on cutaneous wound angiogenesis. Br J Dermatol 2011; 165(6): 1223-35. [http://dx.doi.org/10.1111/j.1365-2133.2011.10599.x] [PMID: 21895624] [116] Krischel V, Bruch-Gerharz D, Suschek C, Kröncke KD, Ruzicka T, Kolb-Bachofen V. Biphasic effect of exogenous nitric oxide on proliferation and differentiation in skin derived keratinocytes but not fibroblasts. J Invest Dermatol 1998; 111(2): 286-91. [http://dx.doi.org/10.1046/j.1523-1747.1998.00268.x] [PMID: 9699731] [117] Stallmeyer B, Kämpfer H, Kolb N, Pfeilschifter J, Frank S. The function of nitric oxide in wound repair: inhibition of inducible nitric oxide-synthase severely impairs wound reepithelialization. J Invest Dermatol 1999; 113(6): 1090-8. [http://dx.doi.org/10.1046/j.1523-1747.1999.00784.x] [PMID: 10594757] [118] Bainbridge P. Wound healing and the role of fibroblasts. Journal of wound care 2013; 22(8): 407-8. [119] Shi HP, Most D, Efron DT, Tantry U, Fischel MH, Barbul A. The role of iNOS in wound healing. Surgery 2001; 130(2): 225-9. [http://dx.doi.org/10.1067/msy.2001.115837] [PMID: 11490353] [120] Burrow JW, Koch JA, Chuang HH, Zhong W, Dean DD, Sylvia VL. Nitric oxide donors selectively reduce the expression of matrix metalloproteinases-8 and -9 by human diabetic skin fibroblasts. J Surg Res 2007; 140(1): 90-8. [http://dx.doi.org/10.1016/j.jss.2006.11.010] [PMID: 17418871] [121] Ayuk SM, Abrahamse H, Houreld NN. The Role of Matrix Metalloproteinases in Diabetic Wound Healing in relation to Photobiomodulation. J Diabetes Res 2016; 2016: 1-9. [http://dx.doi.org/10.1155/2016/2897656] [PMID: 27314046] [122] Afzali H, Khaksari M, Norouzirad R, Jeddi S, Kashfi K, Ghasemi A. Acidified nitrite improves wound healing in type 2 diabetic rats: Role of oxidative stress and inflammation. Nitric Oxide 2020; 103: 208. [http://dx.doi.org/10.1016/j.niox.2020.07.001] [PMID: 32693171] [123] Afzali H, Khaksari M, Jeddi S, Kashfi K, Abdollahifar MA, Ghasemi A. Acidified Nitrite Accelerates Wound Healing in Type 2 Diabetic Male Rats: A Histological and Stereological Evaluation. Molecules 2021; 26(7): 1872. [http://dx.doi.org/10.3390/molecules26071872] [PMID: 33810327] [124] Brem H, Tomic-Canic M. Cellular and molecular basis of wound healing in diabetes. J Clin Invest 2007; 117(5): 1219-22. [http://dx.doi.org/10.1172/JCI32169] [PMID: 17476353] [125] Stepanovic V, Awad O, Jiao C, Dunnwald M, Schatteman GC. Leprdb diabetic mouse bone marrow

NO and Diabetic Wound Healing

The Role of Nitric Oxide in Type 2 Diabetes 159

cells inhibit skin wound vascularization but promote wound healing. Circ Res 2003; 92(11): 1247-53. [http://dx.doi.org/10.1161/01.RES.0000074906.98021.55] [PMID: 12730094] [126] Sivan-Loukianova E, Awad OA, Stepanovic V, Bickenbach J, Schatteman GC. CD34+ blood cells accelerate vascularization and healing of diabetic mouse skin wounds. J Vasc Res 2003; 40(4): 368-77. [http://dx.doi.org/10.1159/000072701] [PMID: 12891006] [127] Westerweel PE, Teraa M, Rafii S, et al. Impaired endothelial progenitor cell mobilization and dysfunctional bone marrow stroma in diabetes mellitus. PLoS One 2013; 8(3): e60357. [http://dx.doi.org/10.1371/journal.pone.0060357] [PMID: 23555959] [128] Witte MB, Thornton FJ, Tantry U, Barbul A. L-Arginine supplementation enhances diabetic wound healing: Involvement of the nitric oxide synthase and arginase pathways. Metabolism 2002; 51(10): 1269-73. [http://dx.doi.org/10.1053/meta.2002.35185] [PMID: 12370845] [129] Kant V, Gopal A, Kumar D, et al. Curcumin-induced angiogenesis hastens wound healing in diabetic rats. J Surg Res 2015; 193(2): 978-88. [http://dx.doi.org/10.1016/j.jss.2014.10.019] [PMID: 25454972] [130] Yang Y, Yin D, Wang F, Hou Z, Fang Z. In situ eNOS/NO up-regulation—a simple and effective therapeutic strategy for diabetic skin ulcer. Sci Rep 2016; 6(1): 30326. [http://dx.doi.org/10.1038/srep30326] [PMID: 27453476] [131] Edmonds ME, Bodansky HJ, Boulton AJM, Chadwick PJ, Dang CN, D'Costa R, et al. Multicenter, randomized controlled, observer-blinded study of a nitric oxide generating treatment in foot ulcers of patients with diabetes-ProNOx1 study. Wound repair and regeneration : official publication of the Wound Healing Society [and] the European Tissue Repair Society 2018; 26(2): 228-37. [http://dx.doi.org/10.1111/wrr.12630] [132] Armstrong DG, Lavery LA, Quebedeaux TL, Walker SC. Surgical morbidity and the risk of amputation due to infected puncture wounds in diabetic versus nondiabetic adults. J Am Podiatr Med Assoc 1997; 87(7): 321-6. [http://dx.doi.org/10.7547/87507315-87-7-321] [PMID: 9241975] [133] Dang CN, Prasad YDM, Boulton AJM, Jude EB. Methicillin-resistant Staphylococcus aureus in the diabetic foot clinic: a worsening problem. Diabet Med 2003; 20(2): 159-61. [http://dx.doi.org/10.1046/j.1464-5491.2003.00860.x] [PMID: 12581269] [134] Englander L, Friedman A. Nitric oxide nanoparticle technology: a novel antimicrobial agent in the context of current treatment of skin and soft tissue infection. J Clin Aesthet Dermatol 2010; 3(6): 4550. [PMID: 20725551] [135] saNurhasni H, Cao J, Choi M, et al. Nitric oxide-releasing poly(lactic-co-glycolic acid)polyethylenimine nanoparticles for prolonged nitric oxide release, antibacterial efficacy, and in vivo wound healing activity. International journal of nanomedicine 2015; 10: 3065-80. [136] Martinez LR, Han G, Chacko M, et al. Antimicrobial and healing efficacy of sustained release nitric oxide nanoparticles against Staphylococcus aureus skin infection. J Invest Dermatol 2009; 129(10): 2463-9. [http://dx.doi.org/10.1038/jid.2009.95] [PMID: 19387479] [137] Ormerod AD, Shah AAJ, Li H, Benjamin NB, Ferguson GP, Leifert C. An observational prospective study of topical acidified nitrite for killing methicillin-resistant Staphylococcus aureus (MRSA) in contaminated wounds. BMC Res Notes 2011; 4(1): 458. [http://dx.doi.org/10.1186/1756-0500-4-458] [PMID: 22032298] [138] Arana V, Paz Y, González A, Méndez V, Méndez JD. Healing of diabetic foot ulcers in L-arginin-treated patients. Biomedicine & pharmacotherapy = Biomedecine & pharmacotherapie. 2004; 58(10): 588-97.

160 The Role of Nitric Oxide in Type 2 Diabetes

Afzali et al.

[139] Armstrong DG, Hanft JR, Driver VR, et al. Effect of oral nutritional supplementation on wound healing in diabetic foot ulcers: a prospective randomized controlled trial. Diabet Med 2014; 31(9): 1069-77. [http://dx.doi.org/10.1111/dme.12509] [PMID: 24867069] [140] Jerônimo MS, Barros AP, MoritaI VEZ, et al. Oral or topical administration of L-arginine changes the expression of TGF and iNOS and results in early wounds healing. Acta Cir Bras 2016; 31(9): 586-96. [http://dx.doi.org/10.1590/S0102-865020160090000003] [PMID: 27737343] [141] Luo JD, Wang YY, Fu WL, Wu J, Chen AF. Gene therapy of endothelial nitric oxide synthase and manganese superoxide dismutase restores delayed wound healing in type 1 diabetic mice. Circulation 2004; 110(16): 2484-93. [http://dx.doi.org/10.1161/01.CIR.0000137969.87365.05] [PMID: 15262829] [142] Kuo YR, Wang CT, Wang FS, Chiang YC, Wang CJ. Extracorporeal shock-wave therapy enhanced wound healing via increasing topical blood perfusion and tissue regeneration in a rat model of STZinduced diabetes. Wound Repair Regen 2009; 17(4): 522-30. [http://dx.doi.org/10.1111/j.1524-475X.2009.00504.x] [PMID: 19614917] [143] Wang GR, Zhu Y, Halushka PV, Lincoln TM, Mendelsohn ME. Mechanism of platelet inhibition by nitric oxide: In vivo phosphorylation of thromboxane receptor by cyclic GMP-dependent protein kinase. Proc Natl Acad Sci USA 1998; 95(9): 4888-93. [http://dx.doi.org/10.1073/pnas.95.9.4888] [PMID: 9560198] [144] Cheung PY, Salas E, Schulz R, Radomski MW. Nitric oxide and platelet function: Implications for neonatology. Semin Perinatol 1997; 21(5): 409-17. [http://dx.doi.org/10.1016/S0146-0005(97)80006-7] [PMID: 9352613] [145] Freedman JE, Loscalzo J, Barnard MR, Alpert C, Keaney JF, Michelson AD. Nitric oxide released from activated platelets inhibits platelet recruitment. J Clin Invest 1997; 100(2): 350-6. [http://dx.doi.org/10.1172/JCI119540] [PMID: 9218511] [146] Masters KSB, Leibovich SJ, Belem P, West JL, Poole-Warren LA. Effects of nitric oxide releasing poly(vinyl alcohol) hydrogel dressings on dermal wound healing in diabetic mice. Wound Repair Regen 2002; 10(5): 286-94. [http://dx.doi.org/10.1046/j.1524-475X.2002.10503.x] [PMID: 12406164] [147] Malone-Povolny MJ, Maloney SE, Schoenfisch MH. Nitric Oxide Therapy for Diabetic Wound Healing. Adv Healthc Mater 2019; 8(12): 1801210. [http://dx.doi.org/10.1002/adhm.201801210] [PMID: 30645055] [148] Choi M, Hasan N, Cao J, Lee J, Hlaing SP, Yoo JW. Chitosan-based nitric oxide-releasing dressing for anti-biofilm and in vivo healing activities in MRSA biofilm-infected wounds. Int J Biol Macromol 2020; 142: 680-92. [http://dx.doi.org/10.1016/j.ijbiomac.2019.10.009] [PMID: 31622708] [149] Nie X, Zhang H, Shi X, et al. Asiaticoside nitric oxide gel accelerates diabetic cutaneous ulcers healing by activating Wnt/β-catenin signaling pathway. Int Immunopharmacol 2020; 79: 106109. [http://dx.doi.org/10.1016/j.intimp.2019.106109] [PMID: 31865242] [150] Ghori V, Mandavia DR, Patel TK, Tripathi CB. Effect of topical nitric oxide donor (0.2 % glyceryl trinitrate) on wound healing in diabetic wistar rats. Int J Diabetes Dev Ctries 2014; 34(1): 45-9. [http://dx.doi.org/10.1007/s13410-013-0138-y] [151] Li Y, Lee PI. Controlled nitric oxide delivery platform based on S-nitrosothiol conjugated interpolymer complexes for diabetic wound healing. Mol Pharm 2010; 7(1): 254-66. [http://dx.doi.org/10.1021/mp900237f] [PMID: 20030413] [152] Samaha R, Othman AI, El-Sherbiny IM, Amer MA, Elhusseini F, ElMissiry MA, et al. Topical Nitric oxide in nanoformulation enhanced wound healing in experimental diabetes in mice. Res J Pharm Biol Chem Sci 2017; 8(4): 499-514.

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CHAPTER 8

Role of Nitric Oxide in Type 2 Diabetes-Induced Osteoporosis Nasibeh Yousefzadeh1, Sajad Jeddi1, Khosrow Kashfi2 and Asghar Ghasemi1,* Endocrine Physiology Research Center, Research Institute for Endocrine Sciences, Shahid Beheshti University of Medical Sciences, Tehran, Iran 2 Department of Molecular, Cellular and Biomedical Sciences, Sophie Davis School of Biomedical Education, City University of New York School of Medicine, New York, NY 10031 , USA 1

Abstract: Osteoporosis affects 200 million people worldwide. Osteoporosis in subjects with diabetes is called diabetoporosis, and type 2 diabetes (T2D) contributes to and aggravates osteoporotic fractures. Hyperglycemia, insulin resistance, bone vasculature impairment, increased inflammation, oxidative stress, and bone marrow adiposity contribute to a higher incidence of osteoporotic fractures in T2D. Decreased nitric oxide (NO) bioavailability due to lower endothelial NO synthase (eNOS)-derived NO and higher inducible NOS (iNOS)-derived NO is one of the main mechanisms of the diabetoporosis. Available data indicates that T2D increases osteoclast-mediated bone resorption and decreases osteoblast-mediated bone formation, mediated in part by reducing eNOS-derived NO and increasing iNOS-derived NO. NO donors delay osteoporosis and decrease osteoporotic fractures in subjects with T2D, suggesting the potential therapeutic implication of NO-based interventions for diabetoporosis.

Keywords: Bone mineral density, Bone marrow stromal cells, Diabetoporosis, Endothelial nitric oxide synthase, Inducible nitric oxide synthase, Nitric oxide, Osteoporosis, Type 2 diabetes. INTRODUCTION Osteoporosis is a silent illness that affects 200 million people worldwide [1 - 3] and is generally diagnosed after an osteoporotic fracture [4, 5]. Osteoporosis is characterized by low bone mineral density (BMD) and deterioration of the bone microarchitecture [6, 7]. Osteoporosis causes about 9 million fractures annually, severely impacting patients' quality of life and imposing high healthcare costs [1, 8]. In addition, ~40% of older women will experience an osteoporotic fracture during their lifetime [5, 9], increasing their mortality rate by 15-20% [10 - 13]. Corresponding author Asghar Ghasemi: Endocrine Physiology Research Center, Research Institute for Endocrine Sciences, Shahid Beheshti University of Medical Sciences, Tehran, Iran; [email protected]., No. 24, Erabi Street, Velenjak, Tehran, Iran; Phone: +98 21 22409309; Fax: +98 21 22416264.

*

Asghar Ghasemi, Khosrow Kashfi, Zahra Bahadoran (Eds.) All rights reserved-© 2022 Bentham Science Publishers

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Osteoporosis is generally associated with senescence and estrogen deficiency; however, other factors, including diabetes, contribute to and deteriorate osteoporotic fracture [14]. Osteoporosis in subjects with diabetes was firstly reported by Albright and Reifenste in 1948 and named diabetoporosis by Ferrari S. in 2015 [15]. Diabetoporosis is one of the leading causes of osteoporotic fractures [14] and is characterized by decreased bone quality and quantity [16]. According to population-based studies conducted from 1980 to 2016, the risk of osteoporotic fractures has been increased in subjects with both type 1 diabetes (T1D) and type 2 diabetes (T2D) [17 - 21]. The risk of osteoporotic fractures is 200-700% higher in subjects with T1D [17, 22, 23] and 40-80% higher in subjects with T2D [22, 24]. In addition, fracture healing is delayed in subjects with T1D and T2D; a study of 5966 cases of hip fracture in patients with T1D and T2D showed that these patients required longer in-hospital stay [25]. These data emphasize the need for developing new strategies against osteoporotic fractures in patients with diabetes, especially in subjects with T2D, which accounts for ~90% of diabetic subjects [26]. Nitric oxide (NO) bioavailability is decreased in the bones of humans and animals with T2D and can be considered one of the primary mechanisms underlying diabetoporosis [27]. NO is produced in bone cells by the three isoforms of NO synthase (NOS) enzymes, including endothelial, neural, and inducible NOS (eNOS, nNOS, and iNOS, respectively) [28, 29]. NO in the bone acts as a double-edged sword; a low level of NO increases osteoblast-mediated bone formation [30, 31], decreases osteoclast-mediated bone resorption [32, 33], has protective effects against osteoporotic fractures, and increases the rate of bone healing [30, 34] in postmenopausal women and ovariectomized rats. A high NO level has adverse effects on bone cells’ activity [28, 35]. eNOS-/- rodents have decreased osteoblast [36] and increased osteoclast activities [37 - 39] that are associated with lower trabecular bone volume and cortical thickness as well as lower BMD [40, 41]. These changes increase the risk of osteoporotic fractures [42] and decrease the rate of the bone healing process [43] in eNOS-/- rodents. In addition, iNOS-/- rodents show reduced bone growth and bone length [44] only in pre-natal but not in adult bones [44]. Reduced osteoclasts and osteoblasts in nNOS-/- rodents are associated with lower bone remodeling [45, 46]. nNOS-/- rodents have lower bone remodeling and lower numbers of osteoclasts and osteoblasts. The effect of NO on bone function in healthy subjects has been previously reviewed [47, 48]. This chapter deals with the role of NO in diabetoporosis.

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NITRIC OXIDE AND BONE: A BRIEF OVERVIEW The effect of NO on bone function is dependent on its concentration; a low level of NO is beneficial for several physiological functions of bone, including normal bone formation [49, 50], development [28, 51], remodeling [52], and fracture healing [53], whereas, a high NO level has detrimental effects on all of these functions [28]. In support of this notion, low and middle doses of nitroglycerin, as a NO donor, stimulate osteoblast activity and bone formation [35], but its high doses decrease osteoblast activity [35] and thus decrease the rate of bone turnover [35]. Regarding the effects of NO on osteoclast activity and bone resorption, it has been reported that a low level of NO may be necessary for normal osteoclast activity; this proposition rests on observations that NOS inhibitors inhibit the activity and motility of isolated osteoclasts [34, 54]. However, a high NO level inhibits osteoclast formation and activity and promotes apoptosis in osteoclasts [35]. There is a substantial body of evidence showing that the cyclic guanosine monophosphate (cGMP)-dependent signaling is vital for normal bone formation [50], and cGMP has been proposed as the primary mediator of NO on bone function [52]. The stimulatory effects of NO on osteoblasts are mediated by cGMP since it is abolished by guanylate cyclase (GC) inhibitors [55]. NO, via activation of soluble GC (sGC), increases osteoblastic bone formation [56], whereas the effect of NO on osteoclasts is mainly inhibitory and, in part, cGMPindependent [47, 56]. NO via activation of sGC is also a key regulator of angiogenesis in the bone that plays an essential role in bone repair [57]. In addition, NO, via core-binding factor alpha 1 (a critical transcription factor for osteoblastic differentiation and osteogenesis)/cGMP/PKG pathway, increases matrix metalloproteinase-13 (MMP-13) expression in osteoblasts, which is an essential factor for bone development [28, 51]; therapeutic effects of estrogen in bone are also in part mediated by the eNOS/cGMP pathway [55, 58, 59]. NOS Expression in the Bone Cells NO is produced in the bone cells by eNOS, nNOS, and iNOS [55, 60 - 62]. eNOS is mainly expressed in osteoblasts and osteocytes [63, 64], but its expression has also been documented in osteoclasts and bone marrow stromal cells [55, 65]. eNOS is also expressed in chondrocytes of the epiphyseal growth plate, mainly in the first four weeks of the neonatal period, and after that, it declines with age [66]. iNOS is expressed in osteoclasts in neonatal rats under physiological conditions [66]; in adults, it is expressed in response to pro-inflammatory cytokines under pathological conditions in all bone cells [54, 67, 68].

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Compared to eNOS, iNOS can produce much larger quantities of NO (picomolar range vs. nanomolar range) [34]. The level of expression of iNOS in bone cells is associated with the type and combination of cytokines; it has been shown that a combination of interleukin-1 (IL-1), tumor necrosis factor-α (TNF-α), and interferons (IFN) cytokines provide a more effective induction than a single cytokine [49]. nNOS is expressed during skeletal development [66] and fracture healing [53] in bone lining cells and also in osteocytes [63, 64]. TYPE 2 DIABETES AND BONE INDICES T2D not only aggravates osteopenia (T-scores between -1 and -2.5) and osteoporosis (T-scores≤-2.5) but also is one of the causes of osteopenia and osteoporosis [14]. According to the World Health Organization criteria, osteoporosis is defined as a BMD that ranks 2.5 standard deviations below the mean for young, healthy subjects [70, 71] (T-scores≤-2.5; T-score is a standard deviation and a mathematical term that calculates how much a result varies from the mean). Clinically, measurement of BMD is used to classify the onset and extent of osteoporosis; however, microarchitecture of trabecular and cortical bones is a key component of bone quality; therefore, it needs to be considered too [69 - 76]. T2D affects mineral density and microarchitecture of the bone and increases the risk of osteoporosis [22]. Type 2 Diabetes and BMD Conflicting results have been reported about changes in BMD in subjects with T2D, with increased [77 - 79], unchanged [80], or decreased [81, 82] BMD have been documented. In subjects with T2D, BMD increases at the femoral neck [83, 84] and decreases at the hip [22, 85]. Increased BMD in subjects with T2D is partly due to high insulin levels, which is an osteogenic factor and can stimulate osteoblast activity and differentiation [86]. A positive correlation between fasting circulating insulin and BMD has been reported in clinical [87] and experimental studies [88, 89]. On the other hand, lower BMD mainly occurs in patients with long-term T2D (i.e., > 5 years) [90]. Type 2 Diabetes and Trabecular and Cortical Bone Microarchitectures Despite having a normal, decreased, or increased BMD, patients with T2D have a higher risk of osteoporotic fractures [77, 80, 91], suggesting a different etiology of osteoporotic fractures than the general population [92]. This paradox may be explained by measuring indices that are not reflected in BMD measured with Dual-energy X-ray absorptiometry (DEXA) [93, 94]: (1) trabecular bone

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microarchitecture (i.e., bone volume/tissue volume (BV/TV), trabecular separation (Tb.Sp), trabecular number (Tb.N), and trabecular thickness (Tb.Th)); (2) cortical bone microarchitecture (i.e., number and size of cortical bone pores). In postmenopausal women with T2D compared to healthy women, the trabecular bones have lower quality (i.e., larger trabecular bone holes, lower BV/TV, greater branch density at the distal radius) [95], and cortical bones are more porous [96]. According to a meta-analysis, increased risk of the hip [19, 97] and distal radius and tibia [94] fractures in subjects with T2D are associated with increased cortical porosity [94] and decreased Tb.Th, and Tb.N as well as increased Tb.Sp [98]. The mechanism of changed trabecular and cortical bone microarchitectures in T2D is not fully understood. However, studies in animals with T2D have demonstrated decreased bone formation and increased bone resorption [99, 100]. In support, cross-sectional studies indicate lower circulating osteocalcin, a marker of bone formation, in subjects with T2D [101, 102]. In addition, a meta-analysis of 66 human studies reported an overall low bone turnover in diabetic patients [103]. Patients with T2D have low bone formation and resorption [104, 105], whereas animals with T2D display low bone formation and high bone resorption [106 - 108]. Increased bone resorption in animals with T2D is indicated by a higher level of bone resorption markers, including carboxy-terminal collagen crosslinks (CTX) or tartrate-resistant acid phosphatase (TRAP) in serum, as well as higher osteoclasts numbers in bone [106, 109]. Type 2 Diabetes and Bone Cells The effect of T2D on bone cells is complex and exerted via direct and indirect pathways [88]. As shown in Fig. (1), T2D directly decreases osteoblast and increases osteoclast activity and differentiation [110 - 121]. In addition, T2D decreases bone blood flow, increases fat accumulation in the bone marrow, and increases inflammation and oxidative stress in the bone matrix, resulting in decreased osteoblast and increased osteoclast activity and differentiation [119 121]. These changes in the bones of T2D patients reduce trabecular and cortical bone quality and contribute to a higher incidence of osteoporotic fractures and delayed fracture healing [119 - 122]. In the direct pathway, hyperglycemia and insulin resistance decrease osteoblastmediated bone formation and increase osteoclast-mediated bone resorption [110 121]. In osteoblasts of humans and animals with T2D, lower levels of activation markers, including alkaline phosphatase (ALP) and collagen synthesis [123, 124], as well as differentiation markers, including runt-related transcription factor 2 (Runx-2), osteocalcin, bone morphogenetic protein-2 (BMP-2), drosophila distal

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less gene (Dlx-5), and osteopontin (OPN) [110 - 117] have been observed. In addition, higher production of Wnt inhibitors, sclerostin, and Dickkopf WNT signaling pathway inhibitor-1 (DKK-1) by osteocytes causes lower osteoblasts differentiation in T2D [125].

Fig. (1). Main pathophysiological mechanisms involved in diabetoporosis. Subjects with T2D have a higher risk of osteoporotic fracture due to lower bone turnover and healing rates, higher bone mineralization, and abnormal posttranslational modifications of collagen. Bone vasculature impairment, increased inflammation, oxidative stress, and bone marrow adiposity are key factors that contribute to a higher incidence of osteoporotic fractures and delayed fracture healing in T2D. T2D, type 2 diabetes; Runx-2, Runt-related transcription factor 2; BMP-2, bone morphogenetic protein-2; NFAT, nuclear factor of activated T cells; RANKL, receptor activator of nuclear factor kappa-Β ligand; TRAP, tartrate-resistant acid phosphatase; DKK-1, Dickkopf WNT signaling pathway inhibitor-1; AGEs, advanced glycation end products. The Figure source is [27], Diabetoporosis: Role of nitric oxide, EXCLI Journal, 2021; 20:764-780.

In osteoclasts of humans and animals with T2D, higher activities of osteoclasts’ markers, including the nuclear factor of activated T cells (NFAT), receptor activator of nuclear factor kappa-Β ligand (RANKL), macrophage-colony stimulating factor (M-CSF), and TRAP have been observed [118 - 121]. Osteoprotegerin (OPG) level, a soluble receptor of RANKL, which negatively regulates osteoclast differentiation, is also lower in T2D [126].

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In the indirect pathway, hyperglycemia and insulin resistance decrease osteoblastmediated bone formation and increase osteoclast-mediated bone resorption by increasing fat accumulation in the marrow cavity, advanced glycation end products (AGEs), oxidative stress, and inflammation as well as impairing bone vasculature [119 - 122]. These changes might explain the higher risk of bone fractures and osteoporosis in T2D. In addition, the presence of independent risk factors for fracture, including lower vitamin D and calcium levels, higher risk of falls, visual impairment, decreased physical activity, and being overweight, all of which are common clinical features in T2D [127 - 129], can partly explain the higher rates of osteoporotic fractures observed in subjects with T2D. Bone NO Bioavailability in Type 2 Diabetes A decrease in NO bioavailability in bones of animals and humans with T2D has been observed in clinical and experimental studies. As shown in Fig. (2), in diabetic bones, NO synthesis is decreased, and NO oxidation is increased (due to NO quenching by AGEs) [130, 131]. In T2D, eNOS-derived NO synthesis in bone cells decreases because of decreased expression [119] and activity [132] of eNOS, uncoupling of eNOS [119], decreased availability of L-arginine [133], and dysfunction of eNOS-caveolin-1 complex [134, 135].

Fig. (2). Proposed mechanisms involved in decreased endothelial nitric oxide (eNOS)-derived NO bioavailability and activity in bones of type 2 diabetic subjects. NO, nitric oxide; eNOS, endothelial nitric oxide synthase; iNOS, inducible nitric oxide synthase. The Figure source is [27], Diabetoporosis: Role of nitric oxide, EXCLI Journal, 2021;20:764-780.

BONE REMODELING Bone remodeling is a continuing process of bone formation and resorption that gives bone its mature structure to maintain normal calcium levels in the body and

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helps repair bone micro-damages [136, 137]. In bone remodeling, bone resorption and formation are coupled, which creates an anatomical structure known as basic multicellular units (BMU) [138, 139]. BMU composes the remodeling unit of bone and includes osteoclasts, osteoblasts, osteocytes, and bone-lining cells [136, 140]. Bone remodeling is regulated by both systemic (including parathyroid hormone, calcitriol, growth hormone, glucocorticoids, thyroid hormones, and sex hormones) and local (cytokines and growth factors) factors that affect bone cell functions through both RANKL and OPG systems [136, 137]. RANKL and OPG are produced by pre-osteoblasts [141, 142] and osteoblasts [122], respectively; RANKL receptors are expressed on hematopoietic osteoclast progenitors and osteoclasts membrane [141, 142]. OPG and RANKL directly regulate osteoclasts differentiation and bone resorption [143]. RANKL increases osteoclastogenesis and activates mature osteoclasts in the presence of M-CSF [144]. OPG negatively regulates RANKL binding to RANK [122] and inhibits osteoclasts differentiation and activation [145]. In T2D, an imbalance between RANKL and OPG expression may contribute to the higher bone resorption, higher risk of fracture, and delayed fracture repair [146]. Fernanda et al. reported that in alloxan-induced diabetes in rats, RANK, RANKL, and OPG were lower at the fracture site (tibia); however, the RANKL/OPG ratio was significantly higher, suggesting an increased resorptive activity [146]. The higher RANKL/OPG ratio in T2D is partly due to increased iNOS-derived NO that stimulates RANKL and M-CSF expression in pre-osteoblasts [147, 148] and decreases eNOS-derived NO that inhibits the production of M-CSF and RANKL and increases the production of OPG [14]. Bone Remodeling in Type 2 Diabetes: Role of NO The remodeling cycle consists of 4 consecutive steps: (1) activation, (2) resorption, (3) reversal, and (4) formation [136, 137]. Since the duration of the formation phase (4 to 6 months) is longer than other phases (2 to 4 weeks for resorption and 4 to 5 weeks in reversal), any increase in the rate of bone remodeling will result in a loss of bone formation [138, 149 - 151]. The duration of the remodeling cycles in normal trabecular and cortical bones are about 200 and 120 days, respectively [152]. In step 1 (activation), the osteocytes sense initiating remodeling signals and translate them into biological signals [153, 154]. Initiating remodeling signals (mechanical forces, thyroid hormones, parathyroid hormone, and estrogens) increase eNOS-derived NO in osteocytes [61, 155, 156] that has an inhibitory

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effect on the expression of transforming growth factor β (TGF-β) and sclerostin (SOST) in osteocytes [153, 157]. TGF-β has an inhibitory effect on osteoclast mediated-bone resorption, and SOST has an inhibitory effect on osteoblast mediated-bone formation [158 - 161]. Initiating remodeling signals in this step are also sensed by bone lining cells that create a raised canopy above the remodeling surface and facilitate the recruitment of hematopoietic stem cells (HSC, as osteoclast progenitor cells) and mesenchymal stem cells (MSC, as osteoblast progenitor cells) to the BMU [162]. In step 2 (resorption), the decreased TGF-β in osteocytes recruits HSC from the bone marrow or the circulation to the BMU; recruited HSCs are then differentiated to osteoclasts and start bone resorption by secreting acid phosphatase, cathepsin K, and collagenase [163]. iNOS-derived NO stimulates this step; it increases differentiation of HSC to pre-osteoclast and osteoclasts by increasing peroxisome proliferator-activated receptor γ (PPARγ) production in HSC, increasing RANKL and M-CSF expression in pre-osteoblast [147, 148]. In addition, iNOS-derived NO increases osteoclast activity by increasing cathepsin K and collagenase expression [39, 164, 165]. In contrast, eNOS-derived NO inhibits this step by decreasing the production of M-CSF and RANKL in both pre-osteoblasts and osteoblasts [14] and decreasing the activity of cathepsin K and collagenase in osteoclasts [39, 164, 165]. In step 3 (reversal), mononuclear macrophage-like cells engulf and remove demineralized undigested collagen and generate transition signals that stop bone resorption and start bone formation [153]. In step 4 (formation and mineralization), the decreased SOST in osteocytes recruits MSCs that are differentiated into osteoblasts and start the bone formation [166]. eNOS-derived NO stimulates this step; it increases osteogenesis and decreases adipogenesis [167 - 170]. eNOS-derived NO stimulates differentiation of MSC to osteoblast [171] by increasing the expression of osteogenic transcription factors such as Runx2, osterix (OSX), and OPN [168]. eNOS-derived NO also represses the expression of adipogenic transcription factors such as PPARγ and lipoprotein lipase (LPL) [167 - 170] and directly activates osteoblast activity by increasing the ALP [172] and osteocalcin levels [173]. As shown in Fig. (3), T2D increases osteoclast-mediated bone resorption and decreases osteoblast-mediated bone formation, which is mediated in part by decreasing eNOS-derived NO and increasing iNOS-derived NO. Steps 1 and 4 of the bone remodeling process in T2D are inhibited, whereas step 2 is stimulated. T2D at step 1 decreases the production of NO by eNOS in osteocytes that decreasing their capabilities in detecting and initiating the bone remodeling signals [174, 175]. T2D at step 2 decreases the eNOS-derived NO and increases

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iNOS-derived NO that causing increases in osteoclast-mediated bone resorption [39, 164, 165]. In addition, T2D, by decreasing eNOS-derived NO, decreases bone formation in step 4 [176].

Fig. (3). Nitric oxide-mediated effects on bone remodeling in type 2 diabetes. T2D, type 2 diabetes; PPAR-γ, peroxisome proliferator-activated receptor γ; LPL, lipoprotein lipase; MSC, mesenchymal stem cells; HSC, hematopoietic stem cells; TGF-β, transforming growth factor β; SOST, sclerostin; NO, nitric oxide; eNOS, endothelial nitric oxide synthase; iNOS, inducible nitric oxide synthase; RANKL, receptor activator of nuclear factor kappa-Β ligand; OPG, osteoprotegerin; M-CSF, macrophage-colony stimulating factor; Runx2, Runt-related transcription factor 2; OSX, osterix; cGMP, cyclic guanosine monophosphate. The Figure source is [27], Diabetoporosis: Role of nitric oxide, EXCLI Journal, 2021;20:764-780.

NITRIC OXIDE-BASED TREATMENT OF DIABETOPOROSIS The most detrimental effects of T2D on trabecular and cortical bone quality originate from hyperglycemia and its consequences (AGE production, fat accumulation in the bone, and impaired vascularization); thus, effective glycemic control should be considered for the treatment of osteoporotic fractures in T2D [14]. Some anti-diabetic drugs, including metformin and sulfonylureas, positively

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affect osteoporotic fractures in T2D [177]. Metformin decreases fracture risk in diabetic bones by increasing bone formation and decreasing bone resorption and bone adiposity [178, 179]. It has been reported that metformin increases osteoblastogenesis by decreasing PPARγ expression [178, 180], which causes increasing MSC differentiation towards the osteoblasts [178, 180] and decreasing it towards the adipocytes [178, 181]. In addition, metformin promotes osteoblast proliferation, differentiation, and activation by increasing cellular AMP/ATP ratio (inhibits the respiratory chain complex I) [182, 183], expression and phosphorylation of 5ʹ-AMP-activated protein kinase (AMPK), Runx-2 and extracellular signal-regulated kinase (ERK) [184], as well as decreasing AGEs production and glycogen synthase kinase 3 beta /Wnt/β-catenin pathway activity [184]. Metformin also decreases osteoclastogenesis by decreasing RANKL expression in osteoblasts [185]. In addition, metformin decreases osteoporosis (inhibiting osteoclasts and decreasing osteoblast activity) through its antiinflammatory effect on the bone [184]. It should be noted that metformin is structurally similar to aminoguanidine (AG), an inhibitor of iNOS [186], and then can increase NO bioavailability in diabetic bones [187] by decreasing iNOS and increasing eNOS activity [188, 189]. However, this is not the case for other antidiabetic drugs; for example, inhibitors of sodium-glucose cotransporter 2 (SGLT2) can increase bone resorption and negatively affect osteoporotic fractures in T2D [190]. Therefore, based on results obtained from large-scale randomized controlled trials, anti-osteoporotic medications, including bisphosphonates, calcitonin, vitamin D, and calcium supplementations, have been introduced to combating against osteoporotic fractures in T2D [191]. As shown in Table 1, several anti-diabetic and anti-osteoporotic drugs are available to combat osteoporotic fracture in T2D, but these drugs have side effects on bone function and metabolisms. Therefore, new treatments need to be developed with minimal side effects and maximal beneficial effects on bone quality and quantity. NO donors have the potential to be cost-effective novel treatments against osteoporotic fractures in T2D. Possible Strategies for Nitric Oxide-based Treatment of Diabetoporosis Epidemiological studies have shown that organic nitrates can reduce the risk of osteoporotic fractures [223, 224]. The first randomized controlled human study about the effects of NO donors on osteoporotic fractures was reported in 1996 [50]. This study assessed the impact of nitroglycerine on osteoporotic fractures in postmenopausal women and reported that nitroglycerine is as potent as estrogen in protection against osteoporotic fractures [50]. The protective effect of nitroglycerin was also observed in ovariectomized rodents [50, 65, 225 - 227] and in ovariectomized [32, 228] and postmenopausal women [225].

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Nitroglycerin suppresses osteoclast activity and increases osteoblast activity [227] and inhibits bone resorption [28], and stimulates bone formation [33, 225, 229]. Organic nitrates are the only FDA-approved NO donors for heart failure; their anti-osteoporotic effects are lost on long-term use due to the potential development of tolerance and endothelial dysfunction [230]. Inorganic nitrite and nitrate are NO donors with NO-like activity in animals and humans. It has been suggested that they can act as suitable alternatives to organic nitrates [231]. These agents can protect against diabetoporosis directly by decreasing osteoclastmediated bone resorption and increasing osteoblast-mediated bone formation, or indirectly by improving hyperglycemia and insulin resistance [232 - 234] and reducing body weight [235]. Table 1. Mechanisms and side effects of current drugs used for the treatment of osteoporosis. Drugs

Fracture Risk

Bone Parameters

Other Side Effects

Bone Bone BMD Adipogenesis formation resorption Anti-diabetic Drugs Metformin [192]

↑

↓

↑

↓

↓

Sulfonylureas [192]

↑

↑↓

↔

↔

↑

↑

↓

Thiazolidinediones [192] Incretin system [192]

↑

↓

Androgens [193, 194]

↔

↔

NPS 2143 [195 - 197]

↑

↑

Romosozumab [198, 199]

↑

Osteocalcin [200]

↑

↓ Mineralization; ↓ PTH level; ↓ Bone turnovers rate; ↔ Fracture healing

↑ ↑

↑

↑

↔

↔

↔

↔

↔

↑

↔

↔

↔

↔

↔

↔

↓

↔

↔

↔

↑ Tendency to cause cancer; Hyperglycemia

↓

↔

↔

↔

Cancer; ↑ Risk of developing diabetes

Anti-osteoporotic Drugs

Calcitonin [193, 201 - 203] Estrogen [204 - 206]

↑

↑ Risk of prostate cancer

Heart attack and myocardial infarction

NO, T2D, and Osteoporosis

The Role of Nitric Oxide in Type 2 Diabetes 173

(Table 1) cont.....

Drugs Tamoxifen [207]

Fracture Risk

Bone Parameters

Other Side Effects

↔

↓

↔

↔

↔

Bisphosphonates [208 - 210]

↔

↓

↔

↔

↔

↑ Bone brittle ↑ Osteonecrosis

Denosumab [211, 212]

↔

↓

↔

↔

↔

↑ Skin eczema; Hypocalcaemia; ↑ Vertebral fractures

Cathepsin K inhibitors [213, 214]

↔

↓

↔

↔

↔

↑ Skin rashes; ↑ Cardiocerebrovascular events

Calcium [215, 216]

↑

↔

↔

↔

↔

↑ Risk of cardiovascular diseases; ↑ Kidney stones; ↑ Risk of hip fractures

↑

↔

↑

↔

↔

Hyperglycemia; ↓ Insulin sensitivity; ↑ Cortical porosity

Teriparatide and abaloparatide [217 - 222]

↑, increase; ↓, decrease; ↔, no change; BMD, bone mineral density; PTH, parathyroid hormones.

CONCLUDING REMARKS T2D, directly and indirectly, decreases osteoblast-mediated bone formation and increases osteoclast-mediated bone resorption; both deteriorate trabecular and cortical bone quality and increase the risk of osteoporotic fracture. Decreased NO bioavailability in diabetic bone, as a primary mechanism of diabetoporosis, is due to decreased eNOS-derived NO, decreased availability of L-arginine, and decreased activity of cGMP/PKG as well as increased iNOS-derived NO and activity of arginase. Therefore, a treatment that decreases hyperglycemia and increases NO bioavailability (both can be done using NO donors) can potentially be used to prevent and treat T2D-induced osteoporosis. Such a treatment can promote osteoblast function and bone circulation and decrease osteoclast function and fat accumulation in the marrow cavity, all of which improve bone quality and decrease the risk of osteoporotic fracture in subjects with T2D. NO donors can potentially be used as safe and cost-effective novel therapeutic agents in diabetoporosis. This issue, however, remains to be verified in a well-designed clinical trial. CONSENT OF PUBLICATION Permission from EXCLI Journal for Figures 1, 2, and 3.

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Yousefzadeh et al.

CONFLICT OF INTEREST The author declares no conflict of interest, financial or otherwise. ACKNOWLEDGEMENT Declared none. REFERENCES [1]

Pavone V, Testa G, Giardina SMC, Vescio A, Restivo DA, Sessa G. Pharmacological Therapy of Osteoporosis: A Systematic Current Review of Literature. Front Pharmacol 2017; 8: 803-3. [http://dx.doi.org/10.3389/fphar.2017.00803] [PMID: 29163183]

[2]

Tian L, Yang R, Wei L, et al. Prevalence of osteoporosis and related lifestyle and metabolic factors of postmenopausal women and elderly men. Medicine (Baltimore) 2017; 96(43): e8294. [http://dx.doi.org/10.1097/MD.0000000000008294] [PMID: 29068999]

[3]

Ström O, Borgström F, Kanis JA, et al. Osteoporosis: burden, health care provision and opportunities in the EU. Arch Osteoporos 2011; 6(1-2): 59-155. [http://dx.doi.org/10.1007/s11657-011-0060-1] [PMID: 22886101]

[4]

Alswat KA. Gender Disparities in Osteoporosis. J Clin Med Res 2017; 9(5): 382-7. [http://dx.doi.org/10.14740/jocmr2970w] [PMID: 28392857]

[5]

Sözen T, Özışık L, Calik Basaran N. An overview and management of osteoporosis. Eur J Rheumatol 2017; 4(1): 46-56. [http://dx.doi.org/10.5152/eurjrheum.2016.048] [PMID: 28293453]

[6]

Lelovas PP, Xanthos TT, Thoma SE, Lyritis GP, Dontas IA. The laboratory rat as an animal model for osteoporosis research. Comp Med 2008; 58(5): 424-30. [PMID: 19004367]

[7]

Bliuc D, Nguyen ND, Alarkawi D, Nguyen TV, Eisman JA, Center JR. Accelerated bone loss and increased post-fracture mortality in elderly women and men. Osteoporos Int 2015; 26(4): 1331-9. [http://dx.doi.org/10.1007/s00198-014-3014-9] [PMID: 25600473]

[8]

Lin X, Xiong D, Peng YQ, et al. Epidemiology and management of osteoporosis in the People’s Republic of China: current perspectives. Clin Interv Aging 2015; 10: 1017-33. [PMID: 26150706]

[9]

Stagi S, Cavalli L, Iurato C, Seminara S, Brandi ML, de Martino M. Bone metabolism in children and adolescents: main characteristics of the determinants of peak bone mass. Clin Cases Miner Bone Metab 2013; 10(3): 172-9. [PMID: 24554926]

[10]

Wang CB, Lin CFJ, Liang WM, et al. Excess mortality after hip fracture among the elderly in Taiwan: A nationwide population-based cohort study. Bone 2013; 56(1): 147-53. [http://dx.doi.org/10.1016/j.bone.2013.05.015] [PMID: 23727435]

[11]

Johnell O, Kanis JA. An estimate of the worldwide prevalence, mortality and disability associated with hip fracture. Osteoporos Int 2004; 15(11): 897-902. [http://dx.doi.org/10.1007/s00198-004-1627-0] [PMID: 15490120]

[12]

González-Zabaleta J, Pita-Fernandez S, Seoane-Pillado T, López-Calviño B, Gonzalez-Zabaleta JL. Comorbidity as a predictor of mortality and mobility after hip fracture. Geriatr Gerontol Int 2016; 16(5): 561-9. [http://dx.doi.org/10.1111/ggi.12510] [PMID: 25981487]

[13]

Hernlund E, Svedbom A, Ivergård M, et al. Osteoporosis in the European Union: medical

NO, T2D, and Osteoporosis

The Role of Nitric Oxide in Type 2 Diabetes 175

management, epidemiology and economic burden. Arch Osteoporos 2013; 8(1-2): 136. [http://dx.doi.org/10.1007/s11657-013-0136-1] [PMID: 24113837] [14]

Wongdee K, Charoenphandhu N. Osteoporosis in diabetes mellitus: Possible cellular and molecular mechanisms. World J Diabetes 2011; 2(3): 41-8. [http://dx.doi.org/10.4239/wjd.v2.i3.41] [PMID: 21537459]

[15]

Ferrari S. Pathophysiology of diabetoporosis. Endocrine Abstracts. BioScientifica 2015. [http://dx.doi.org/10.1530/endoabs.37.S17.2]

[16]

Ferrari SL, Abrahamsen B, Napoli N, et al. Bone and Diabetes Working Group of IOF. Diagnosis and management of bone fragility in diabetes: an emerging challenge. Osteoporos Int 2018; 29(12): 258596. [http://dx.doi.org/10.1007/s00198-018-4650-2] [PMID: 30066131]

[17]

Shah VN, Shah CS, Snell-Bergeon JK. Type 1 diabetes and risk of fracture: meta-analysis and review of the literature. Diabet Med 2015; 32(9): 1134-42. [http://dx.doi.org/10.1111/dme.12734] [PMID: 26096918]

[18]

Ahmed LA, Joakimsen RM, Berntsen GK, Fønnebø V, Schirmer H. Diabetes mellitus and the risk of non-vertebral fractures: the Tromsø study. Osteoporos Int 2006; 17(4): 495-500. [http://dx.doi.org/10.1007/s00198-005-0013-x] [PMID: 16283065]

[19]

Forsén L, Meyer HE, Midthjell K, Edna TH. Diabetes mellitus and the incidence of hip fracture: results from the Nord-Trøndelag Health Survey. Diabetologia 1999; 42(8): 920-5. [http://dx.doi.org/10.1007/s001250051248] [PMID: 10491750]

[20]

de Liefde II, van der Klift M, de Laet CEDH, van Daele PLA, Hofman A, Pols HAP. Bone mineral density and fracture risk in type-2 diabetes mellitus: the Rotterdam Study. Osteoporos Int 2005; 16(12): 1713-20. [http://dx.doi.org/10.1007/s00198-005-1909-1] [PMID: 15940395]

[21]

Lipscombe LL, Jamal SA, Booth GL, Hawker GA. The risk of hip fractures in older individuals with diabetes: a population-based study. Diabetes Care 2007; 30(4): 835-41. [http://dx.doi.org/10.2337/dc06-1851] [PMID: 17392544]

[22]

Vestergaard P. Discrepancies in bone mineral density and fracture risk in patients with type 1 and type 2 diabetes—a meta-analysis. Osteoporos Int 2007; 18(4): 427-44. [http://dx.doi.org/10.1007/s00198-006-0253-4] [PMID: 17068657]

[23]

Janghorbani M, Van Dam RM, Willett WC, Hu FB. Systematic review of type 1 and type 2 diabetes mellitus and risk of fracture. Am J Epidemiol 2007; 166(5): 495-505. [http://dx.doi.org/10.1093/aje/kwm106] [PMID: 17575306]

[24]

Moayeri A, Mohamadpour M, Mousavi S, Shirzadpour E, Mohamadpour S, Amraei M. Fracture risk in patients with type 2 diabetes mellitus and possible risk factors: a systematic review and metaanalysis. Ther Clin Risk Manag 2017; 13: 455-68. [http://dx.doi.org/10.2147/TCRM.S131945] [PMID: 28442913]

[25]

Norris R, Parker M. Diabetes mellitus and hip fracture: A study of 5966 cases. Injury 2011; 42(11): 1313-6. [http://dx.doi.org/10.1016/j.injury.2011.03.021] [PMID: 21489532]

[26]

Wu Y, Ding Y, Tanaka Y, Zhang W. Risk factors contributing to type 2 diabetes and recent advances in the treatment and prevention. Int J Med Sci 2014; 11(11): 1185-200. [http://dx.doi.org/10.7150/ijms.10001] [PMID: 25249787]

[27]

Yousefzadeh N, Jeddi S, Kashfi K, Ghasemi A. Diabetoporosis: Role of nitric oxide. EXCLI J 2021; 20: 764-80. [PMID: 34121973]

[28]

Saura M, Tarin C, Zaragoza C. Recent insights into the implication of nitric oxide in osteoblast differentiation and proliferation during bone development. ScientificWorldJournal 2010; 10: 624-32.

176 The Role of Nitric Oxide in Type 2 Diabetes

Yousefzadeh et al.

[http://dx.doi.org/10.1100/tsw.2010.58] [PMID: 20419275] [29]

Rosselli M, Keller PJ, Dubey RK. Role of nitric oxide in the biology, physiology and pathophysiology of reproduction. Hum Reprod Update 1998; 4(1): 3-24. [http://dx.doi.org/10.1093/humupd/4.1.3] [PMID: 9622410]

[30]

Jamal SA, Hamilton CJ. Nitric oxide donors for the treatment of osteoporosis. Curr Osteoporos Rep 2012; 10(1): 86-92. [http://dx.doi.org/10.1007/s11914-011-0087-7] [PMID: 22210559]

[31]

Tai YT, Cherng YG, Chang CC, Hwang YP, Chen JT, Chen RM. Pretreatment with low nitric oxide protects osteoblasts from high nitric oxide-induced apoptotic insults through regulation of c-Jun Nterminal kinase/c-Jun-mediatedBcl-2 gene expression and protein translocation. J Orthop Res 2007; 25(5): 625-35. [http://dx.doi.org/10.1002/jor.20365] [PMID: 17262823]

[32]

Wimalawansa SJ. Nitroglycerin therapy is as efficacious as standard estrogen replacement therapy (Premarin) in prevention of oophorectomy-induced bone loss: a human pilot clinical study. J Bone Miner Res 2000; 15(11): 2240-4. [http://dx.doi.org/10.1359/jbmr.2000.15.11.2240] [PMID: 11092405]

[33]

Wimalawansa SJ. Restoration of ovariectomy-induced osteopenia by nitroglycerin. Calcif Tissue Int 2000; 66(1): 56-60. [http://dx.doi.org/10.1007/s002230050011] [PMID: 10602846]

[34]

van’T Hof RJ, Ralston SH. Nitric oxide and bone. Immunology 2001; 103(3): 255-61. [http://dx.doi.org/10.1046/j.1365-2567.2001.01261.x] [PMID: 11454054]

[35]

Hao YJ, Tang Y, Chen FB, Pei FX. Different doses of nitric oxide donor prevent osteoporosis in ovariectomized rats. Clin Orthop Relat Res 2005; &NA;(435): 226-31. [http://dx.doi.org/10.1097/01.blo.0000153990.74837.73] [PMID: 15930943]

[36]

Afzal F, Polak J, Buttery L. Endothelial nitric oxide synthase in the control of osteoblastic mineralizing activity and bone integrity. J Pathol 2004; 202(4): 503-10. [http://dx.doi.org/10.1002/path.1536] [PMID: 15095278]

[37]

Armour KE, Van 'T Hof RJ, Grabowski PS, Reid DM, Ralston SH. Evidence for a pathogenic role of nitric oxide in inflammation-induced osteoporosis. J Bone Miner Res 1999; 14(12): 2137-42. [http://dx.doi.org/10.1359/jbmr.1999.14.12.2137] [PMID: 10620073]

[38]

Kasten TP, Collin-Osdoby P, Patel N, et al. Potentiation of osteoclast bone-resorption activity by inhibition of nitric oxide synthase. Proc Natl Acad Sci USA 1994; 91(9): 3569-73. [http://dx.doi.org/10.1073/pnas.91.9.3569] [PMID: 7513424]

[39]

Percival MD, Ouellet M, Campagnolo C, Claveau D, Li C. Inhibition of cathepsin K by nitric oxide donors: evidence for the formation of mixed disulfides and a sulfenic acid. Biochemistry 1999; 38(41): 13574-83. [http://dx.doi.org/10.1021/bi991028u] [PMID: 10521264]

[40]

Hefler LA, Reyes CA, O’Brien WE, Gregg AR. Perinatal development of endothelial nitric oxide synthase-deficient mice. Biol Reprod 2001; 64(2): 666-73. [http://dx.doi.org/10.1095/biolreprod64.2.666] [PMID: 11159371]

[41]

Armour KE, Armour KJ, Gallagher ME, et al. Defective bone formation and anabolic response to exogenous estrogen in mice with targeted disruption of endothelial nitric oxide synthase. Endocrinology 2001; 142(2): 760-6. [http://dx.doi.org/10.1210/endo.142.2.7977] [PMID: 11159848]

[42]

Yan Q, Feng Q, Beier F. Endothelial nitric oxide synthase deficiency in mice results in reduced chondrocyte proliferation and endochondral bone growth. Arthritis Rheum 2010; 62(7): 2013-22. [PMID: 20506524]

[43]

Collin-Osdoby P, Nickols GA, Osdoby P. Bone cell function, regulation, and communication: A role

NO, T2D, and Osteoporosis

The Role of Nitric Oxide in Type 2 Diabetes 177

for nitric oxide. J Cell Biochem 1995; 57(3): 399-408. [http://dx.doi.org/10.1002/jcb.240570305] [PMID: 7539433] [44]

Watanuki M, Sakai A, Sakata T, et al. Role of inducible nitric oxide synthase in skeletal adaptation to acute increases in mechanical loading. J Bone Miner Res 2002; 17(6): 1015-25. [http://dx.doi.org/10.1359/jbmr.2002.17.6.1015] [PMID: 12054156]

[45]

van’t Hof RJ, MacPhee J, Libouban H, Helfrich MH, Ralston SH. Regulation of bone mass and bone turnover by neuronal nitric oxide synthase. Endocrinology 2004; 145(11): 5068-74. [http://dx.doi.org/10.1210/en.2004-0205] [PMID: 15297441]

[46]

Jung JY, Lin AC, Ramos LM, Faddis BT, Chole RA. Nitric oxide synthase I mediates osteoclast activity in vitro and in vivo. J Cell Biochem 2003; 89(3): 613-21. [http://dx.doi.org/10.1002/jcb.10527] [PMID: 12761894]

[47]

Kalyanaraman H, Schall N, Pilz RB. Nitric oxide and cyclic GMP functions in bone. Nitric Oxide 2018; 76: 62-70. [http://dx.doi.org/10.1016/j.niox.2018.03.007] [PMID: 29550520]

[48]

Kalyanaraman H, Ramdani G, Pilz RB. Targeting NO signaling for the treatment of osteoporosis. Curr Med Chem 2016; 23(24): 2746-53. [http://dx.doi.org/10.2174/0929867323666160805123422]

[49]

Ralston SH, Ho LP, Helfrich MH, Grabowski PS, Johnston PW, Benjamin N. Nitric oxide: A cytokine-induced regulator of bone resorption. J Bone Miner Res 1995; 10(7): 1040-9. [http://dx.doi.org/10.1002/jbmr.5650100708] [PMID: 7484279]

[50]

Wimalawansa SJ. Rationale for using nitric oxide donor therapy for prevention of bone loss and treatment of osteoporosis in humans. Ann N Y Acad Sci 2007; 1117(1): 283-97. [http://dx.doi.org/10.1196/annals.1402.066] [PMID: 18056048]

[51]

Zaragoza C, López-Rivera E, García-Rama C, et al. Cbfa-1 mediates nitric oxide regulation of MMP13 in osteoblasts. J Cell Sci 2006; 119(9): 1896-902. [http://dx.doi.org/10.1242/jcs.02895] [PMID: 16636074]

[52]

Wimalawansa S, Chapa T, Fang L, Yallampalli C, Simmons D, Wimalawansa S. Frequency-dependent effect of nitric oxide donor nitroglycerin on bone. J Bone Miner Res 2000; 15(6): 1119-25. [http://dx.doi.org/10.1359/jbmr.2000.15.6.1119] [PMID: 10841180]

[53]

Zhu W, Diwan AD, Lin JH, Murrell GAC. Nitric oxide synthase isoforms during fracture healing. J Bone Miner Res 2001; 16(3): 535-40. [http://dx.doi.org/10.1359/jbmr.2001.16.3.535] [PMID: 11277271]

[54]

Brandi ML, Hukkanen M, Umeda T, et al. Bidirectional regulation of osteoclast function by nitric oxide synthase isoforms. Proc Natl Acad Sci USA 1995; 92(7): 2954-8. [http://dx.doi.org/10.1073/pnas.92.7.2954] [PMID: 7535933]

[55]

Mancini L, Moradi-Bidhendi N, Becherini L, Martineti V, MacIntyre I. The biphasic effects of nitric oxide in primary rat osteoblasts are cGMP dependent. Biochem Biophys Res Commun 2000; 274(2): 477-81. [http://dx.doi.org/10.1006/bbrc.2000.3164] [PMID: 10913363]

[56]

Joshua J, Schwaerzer GK, Kalyanaraman H, et al. Soluble guanylate cyclase as a novel treatment target for osteoporosis. Endocrinology 2014; 155(12): 4720-30. [http://dx.doi.org/10.1210/en.2014-1343] [PMID: 25188528]

[57]

Diwan AD, Wang MX, Jang D, Zhu W, Murrell GAC. Nitric oxide modulates fracture healing. J Bone Miner Res 2000; 15(2): 342-51. [http://dx.doi.org/10.1359/jbmr.2000.15.2.342] [PMID: 10703937]

[58]

Van ’t Hof RJ, Ralston SH. Cytokine-Induced Nitric Oxide Inhibits Bone Resorption by Inducing Apoptosis of Osteoclast Progenitors and Suppressing Osteoclast Activity. Cytokine-induced nitric oxide inhibits bone resorption by inducing apoptosis of osteoclast progenitors and suppressing

178 The Role of Nitric Oxide in Type 2 Diabetes

Yousefzadeh et al.

osteoclast activity. J Bone Miner Res 1997; 12(11): 1797-804. [http://dx.doi.org/10.1359/jbmr.1997.12.11.1797] [PMID: 9383684] [59]

Wimalawansa SJ. Nitric oxide and bone. Ann N Y Acad Sci 2010; 1192(1): 391-403. [http://dx.doi.org/10.1111/j.1749-6632.2009.05230.x] [PMID: 20392265]

[60]

Ralston SH, Todd D, Helfrich M, Benjamin N, Grabowski PS. Human osteoblast-like cells produce nitric oxide and express inducible nitric oxide synthase. Endocrinology 1994; 135(1): 330-6. [http://dx.doi.org/10.1210/endo.135.1.7516867] [PMID: 7516867]

[61]

Armour KE, Ralston SH. Estrogen upregulates endothelial constitutive nitric oxide synthase expression in human osteoblast-like cells. Endocrinology 1998; 139(2): 799-802. [http://dx.doi.org/10.1210/endo.139.2.5910] [PMID: 9449657]

[62]

Klein-Nulend J, Helfrich MH, Sterck JGH, et al. Nitric oxide response to shear stress by human bone cell cultures is endothelial nitric oxide synthase dependent. Biochem Biophys Res Commun 1998; 250(1): 108-14. [http://dx.doi.org/10.1006/bbrc.1998.9270] [PMID: 9735341]

[63]

Helfrich MH, Evans DE, Grabowski PS, Pollock JS, Ohshima H, Ralston SH. Expression of nitric oxide synthase isoforms in bone and bone cell cultures. J Bone Miner Res 1997; 12(7): 1108-15. [http://dx.doi.org/10.1359/jbmr.1997.12.7.1108] [PMID: 9200011]

[64]

Fox SW, Chow JWM. Nitric oxide synthase expression in bone cells. Bone 1998; 23(1): 1-6. [http://dx.doi.org/10.1016/S8756-3282(98)00070-2] [PMID: 9662123]

[65]

Wimalawansa SJ. Nitric oxide: novel therapy for osteoporosis. Expert Opin Pharmacother 2008; 9(17): 3025-44. [http://dx.doi.org/10.1517/14656560802197162] [PMID: 19006476]

[66]

Hukkanen MVJ, Platts LAM, De Marticorena IF, O’Shaughnessy M, Macintyre I, Polak JM. Developmental regulation of nitric oxide synthase expression in rat skeletal bone. J Bone Miner Res 1999; 14(6): 868-77. [http://dx.doi.org/10.1359/jbmr.1999.14.6.868] [PMID: 10352094]

[67]

Zheng H, Yu X, Collin-Osdoby P, Osdoby P. RANKL stimulates inducible nitric-oxide synthase expression and nitric oxide production in developing osteoclasts. An autocrine negative feedback mechanism triggered by RANKL-induced interferon-beta via NF-kappaB that restrains osteoclastogenesis and bone resorption. J Biol Chem 2006; 281(23): 15809-20. [http://dx.doi.org/10.1074/jbc.M513225200] [PMID: 16613848]

[68]

Wimalawansa SJ. Chapter 59 Skeletal Effects of Nitric Oxide Novel Agent for Osteoporosis. Principles of Bone Biology. 2008; pp. 1273-310.

[69]

Turner RT, Vandersteenhoven JJ, Bell NH. The effects of ovariectomy and 17β-estradiol on cortical bone histomorphometry in growing rats. J Bone Miner Res 1987; 2(2): 115-22. [http://dx.doi.org/10.1002/jbmr.5650020206] [PMID: 3455160]

[70]

Danielsen CC, Mosekilde L, Svenstrup B. Cortical bone mass, composition, and mechanical properties in female rats in relation to age, long-term ovariectomy, and estrogen substitution. Calcif Tissue Int 1993; 52(1): 26-33. [http://dx.doi.org/10.1007/BF00675623] [PMID: 8453502]

[71]

Sharma D, Larriera AI, Palacio-Mancheno PE, et al. The effects of estrogen deficiency on cortical bone microporosity and mineralization. Bone 2018; 110: 1-10. [http://dx.doi.org/10.1016/j.bone.2018.01.019] [PMID: 29357314]

[72]

Aerssens J, van Audekercke R, Talalaj M, Geusens P, Bramm E, Dequeker J. Effect of 1alpha-vitamin D3 and estrogen therapy on cortical bone mechanical properties in the ovariectomized rat model. Endocrinology 1996; 137(4): 1358-64. [http://dx.doi.org/10.1210/endo.137.4.8625911] [PMID: 8625911]

[73]

Kimmel DB, Wronski TJ. Nondestructive measurement of bone mineral in femurs from

NO, T2D, and Osteoporosis

The Role of Nitric Oxide in Type 2 Diabetes 179

ovariectomized rats. Calcif Tissue Int 1990; 46(2): 101-10. [http://dx.doi.org/10.1007/BF02556093] [PMID: 2105147] [74]

Miller SC, Bowman BM, Miller MA, Bagi CM. Calcium absorption and osseous organ-, tissue-, and envelope-specific changes following ovariectomy in rats. Bone 1991; 12(6): 439-46. [http://dx.doi.org/10.1016/8756-3282(91)90033-F] [PMID: 1797059]

[75]

Zhang Y, Lai WP, Leung PC, Wu CF, Wong MS. Short- to mid-term effects of ovariectomy on bone turnover, bone mass and bone strength in rats. Biol Pharm Bull 2007; 30(5): 898-903. [http://dx.doi.org/10.1248/bpb.30.898] [PMID: 17473432]

[76]

Francisco JI, Yu Y, Oliver RA, Walsh WR. Relationship between age, skeletal site, and time postovariectomy on bone mineral and trabecular microarchitecture in rats. J Orthop Res 2011; 29(2): 18996. [http://dx.doi.org/10.1002/jor.21217] [PMID: 20722002]

[77]

van Daele PLA, Stolk RP, Burger H, et al. Bone density in non-insulin-dependent diabetes mellitus. The Rotterdam Study. Ann Intern Med 1995; 122(6): 409-14. [http://dx.doi.org/10.7326/0003-4819-122-6-199503150-00002] [PMID: 7856988]

[78]

Schwartz AV, Sellmeyer DE, Ensrud KE, et al. Study of Osteoporotic Features Research Group. Older women with diabetes have an increased risk of fracture: a prospective study. J Clin Endocrinol Metab 2001; 86(1): 32-8. [http://dx.doi.org/10.1210/jcem.86.1.7139] [PMID: 11231974]

[79]

Lunt M, Masaryk P, Scheidt-Nave C, et al. The effects of lifestyle, dietary dairy intake and diabetes on bone density and vertebral deformity prevalence: the EVOS study. Osteoporos Int 2001; 12(8): 68898. [http://dx.doi.org/10.1007/s001980170069] [PMID: 11580083]

[80]

Sosa M, Dominguez M, Navarro MC, et al. Bone mineral metabolism is normal in non-insuli-dependent diabetes mellitus. J Diabetes Complications 1996; 10(4): 201-5. [http://dx.doi.org/10.1016/1056-8727(95)00062-3] [PMID: 8835919]

[81]

Nicodemus KK, Folsom AR. Iowa Women’s Health Study. Type 1 and type 2 diabetes and incident hip fractures in postmenopausal women. Diabetes Care 2001; 24(7): 1192-7. [http://dx.doi.org/10.2337/diacare.24.7.1192] [PMID: 11423501]

[82]

Levin ME, Boisseau VC, Avioli LV. Effects of diabetes mellitus on bone mass in juvenile and adultonset diabetes. N Engl J Med 1976; 294(5): 241-5. [http://dx.doi.org/10.1056/NEJM197601292940502] [PMID: 1244549]

[83]

Yamaguchi T, Kanazawa I, Yamamoto M, et al. Associations between components of the metabolic syndrome versus bone mineral density and vertebral fractures in patients with type 2 diabetes. Bone 2009; 45(2): 174-9. [http://dx.doi.org/10.1016/j.bone.2009.05.003] [PMID: 19446053]

[84]

Petit MA, Paudel ML, Taylor BC, et al. Osteoporotic Fractures in Men (MrOs) Study Group. Bone mass and strength in older men with type 2 diabetes: The Osteoporotic Fractures in Men Study. J Bone Miner Res 2010; 25(2): 285-91. [http://dx.doi.org/10.1359/jbmr.090725] [PMID: 19594301]

[85]

Yaturu S, Humphrey S, Landry C, Jain SK. Decreased bone mineral density in men with metabolic syndrome alone and with type 2 diabetes. Med Sci Monit 2009; 15(1): CR5-9. [PMID: 19114969]

[86]

Li H, Liu D, Zhao CQ, Jiang LS, Dai LY. Insulin potentiates the proliferation and bone morphogenetic protein-2-induced osteogenic differentiation of rat spinal ligament cells via extracellular signalregulated kinase and phosphatidylinositol 3-kinase. Spine 2008; 33(22): 2394-402. [http://dx.doi.org/10.1097/BRS.0b013e3181838fe5] [PMID: 18923314]

[87]

Barrett-Connor E, Kritz-Silverstein D. Does hyperinsulinemia preserve bone? Diabetes Care 1996;

180 The Role of Nitric Oxide in Type 2 Diabetes

Yousefzadeh et al.

19(12): 1388-92. [http://dx.doi.org/10.2337/diacare.19.12.1388] [PMID: 8941469] [88]

Palermo A, D’Onofrio L, Buzzetti R, Manfrini S, Napoli N. Pathophysiology of Bone Fragility in Patients with Diabetes. Calcif Tissue Int 2017; 100(2): 122-32. [http://dx.doi.org/10.1007/s00223-016-0226-3] [PMID: 28180919]

[89]

Fulzele K, Riddle RC, DiGirolamo DJ, et al. Insulin receptor signaling in osteoblasts regulates postnatal bone acquisition and body composition. Cell 2010; 142(2): 309-19. [http://dx.doi.org/10.1016/j.cell.2010.06.002] [PMID: 20655471]

[90]

Chau DL, Edelman SV, Chandran M. Osteoporosis and Diabetes. Curr Diab Rep 2003; 3(1): 37-42. [http://dx.doi.org/10.1007/s11892-003-0051-8] [PMID: 12643144]

[91]

Bonds DE, Larson JC, Schwartz AV, et al. Risk of fracture in women with type 2 diabetes: the Women’s Health Initiative Observational Study. J Clin Endocrinol Metab 2006; 91(9): 3404-10. [http://dx.doi.org/10.1210/jc.2006-0614] [PMID: 16804043]

[92]

Jindal M, et al. Bone density versus bone quality as a predictor of bone strength. Orthopedics and Rheumatology Open Access Journal 2018; 12(1): 555830. [http://dx.doi.org/10.19080/OROAJ.2018.12.555830]

[93]

Ho-Pham LT, Nguyen TV. Association between trabecular bone score and type 2 diabetes: a quantitative update of evidence. Osteoporos Int 2019; 30(10): 2079-85. [http://dx.doi.org/10.1007/s00198-019-05053-z] [PMID: 31214749]

[94]

Patsch JM, Burghardt AJ, Yap SP, et al. Increased cortical porosity in type 2 diabetic postmenopausal women with fragility fractures. J Bone Miner Res 2013; 28(2): 313-24. [http://dx.doi.org/10.1002/jbmr.1763] [PMID: 22991256]

[95]

Pritchard JM, Giangregorio LM, Atkinson SA, et al. Association of larger holes in the trabecular bone at the distal radius in postmenopausal women with type 2 diabetes mellitus compared to controls. Arthritis Care Res (Hoboken) 2012; 64(1): 83-91. [http://dx.doi.org/10.1002/acr.20602] [PMID: 22213724]

[96]

Burghardt AJ, Issever AS, Schwartz AV, et al. High-resolution peripheral quantitative computed tomographic imaging of cortical and trabecular bone microarchitecture in patients with type 2 diabetes mellitus. J Clin Endocrinol Metab 2010; 95(11): 5045-55. [http://dx.doi.org/10.1210/jc.2010-0226] [PMID: 20719835]

[97]

Janghorbani M, Feskanich D, Willett WC, Hu F. Prospective Study of Diabetes and Risk of Hip Fracture. Prospective study of diabetes and risk of hip fracture: the Nurses’ Health Study. Diabetes Care 2006; 29(7): 1573-8. [http://dx.doi.org/10.2337/dc06-0440] [PMID: 16801581]

[98]

Nilsson AG, Sundh D, Johansson L, et al. Type 2 Diabetes Mellitus Is Associated With Better Bone Microarchitecture But Lower Bone Material Strength and Poorer Physical Function in Elderly Women: A Population-Based Study. J Bone Miner Res 2017; 32(5): 1062-71. [http://dx.doi.org/10.1002/jbmr.3057] [PMID: 27943408]

[99]

Kawashima Y, Fritton JC, Yakar S, et al. Type 2 diabetic mice demonstrate slender long bones with increased fragility secondary to increased osteoclastogenesis. Bone 2009; 44(4): 648-55. [http://dx.doi.org/10.1016/j.bone.2008.12.012] [PMID: 19150422]

[100] Patsch JM, Kiefer FW, Varga P, et al. Increased bone resorption and impaired bone microarchitecture in short-term and extended high-fat diet–induced obesity. Metabolism 2011; 60(2): 243-9. [http://dx.doi.org/10.1016/j.metabol.2009.11.023] [PMID: 20171704] [101] Akin O, Göl K, Aktürk M, Erkaya S. Evaluation of bone turnover in postmenopausal patients with type 2 diabetes mellitus using biochemical markers and bone mineral density measurements. Gynecol Endocrinol 2003; 17(1): 19-29. [http://dx.doi.org/10.1080/gye.17.1.19.29] [PMID: 12724015]

NO, T2D, and Osteoporosis

The Role of Nitric Oxide in Type 2 Diabetes 181

[102] Isaia GC, Ardissone P, Di Stefano M, et al. Bone metabolism in type 2 diabetes mellitus. Acta Diabetol 1999; 36(1-2): 35-8. [http://dx.doi.org/10.1007/s005920050142] [PMID: 10436250] [103] Hygum K, Starup-Linde J, Harsløf T, Vestergaard P, Langdahl BL. MECHANISMS IN ENDOCRINOLOGY: Diabetes mellitus, a state of low bone turnover – a systematic review and metaanalysis. Eur J Endocrinol 2017; 176(3): R137-57. [http://dx.doi.org/10.1530/EJE-16-0652] [PMID: 28049653] [104] Napoli N, Strollo R, Defeudis G, et al. NIRAD (NIRAD 10) and Action LADA Study Groups. Serum Sclerostin and Bone Turnover in Latent Autoimmune Diabetes in Adults. J Clin Endocrinol Metab 2018; 103(5): 1921-8. [http://dx.doi.org/10.1210/jc.2017-02274] [PMID: 29506222] [105] Purnamasari D, Puspitasari MD, Setiyohadi B, Nugroho P, Isbagio H. Low bone turnover in premenopausal women with type 2 diabetes mellitus as an early process of diabetes-associated bone alterations: a cross-sectional study. BMC Endocr Disord 2017; 17(1): 72. [http://dx.doi.org/10.1186/s12902-017-0224-0] [PMID: 29187183] [106] Xu F, Dong Y, Huang X, et al. Decreased osteoclastogenesis, osteoblastogenesis and low bone mass in a mouse model of type 2 diabetes. Mol Med Rep 2014; 10(4): 1935-41. [http://dx.doi.org/10.3892/mmr.2014.2430] [PMID: 25109926] [107] Hamann C, Picke AK, Campbell GM, et al. Effects of parathyroid hormone on bone mass, bone strength, and bone regeneration in male rats with type 2 diabetes mellitus. Endocrinology 2014; 155(4): 1197-206. [http://dx.doi.org/10.1210/en.2013-1960] [PMID: 24467747] [108] Hamann C, Rauner M, Höhna Y, et al. Sclerostin antibody treatment improves bone mass, bone strength, and bone defect regeneration in rats with type 2 diabetes mellitus. J Bone Miner Res 2013; 28(3): 627-38. [http://dx.doi.org/10.1002/jbmr.1803] [PMID: 23109114] [109] Devlin MJ, Van Vliet M, Motyl K, et al. Early-onset type 2 diabetes impairs skeletal acquisition in the male TALLYHO/JngJ mouse. Endocrinology 2014; 155(10): 3806-16. [http://dx.doi.org/10.1210/en.2014-1041] [PMID: 25051433] [110] Sarkar PD, Choudhury AB. Relationships between serum osteocalcin levels versus blood glucose, insulin resistance and markers of systemic inflammation in central Indian type 2 diabetic patients. Eur Rev Med Pharmacol Sci 2013; 17(12): 1631-5. [PMID: 23832730] [111] Chiu KC, Chu A, Go VLW, Saad MF. Hypovitaminosis D is associated with insulin resistance and β cell dysfunction. Am J Clin Nutr 2004; 79(5): 820-5. [http://dx.doi.org/10.1093/ajcn/79.5.820] [PMID: 15113720] [112] Perez-Diaz I, Sebastian-Barajas G, Hernandez-Flores ZG, Rivera-Moscoso R, Osorio-Landa HK, Flores-Rebollar A. The impact of vitamin D levels on glycemic control and bone mineral density in postmenopausal women with type 2 diabetes. J Endocrinol Invest 2015; 38(12): 1365-72. [http://dx.doi.org/10.1007/s40618-015-0394-4] [PMID: 26476727] [113] Mathieu C, Gysemans C, Giulietti A, Bouillon R. Vitamin D and diabetes. Diabetologia 2005; 48(7): 1247-57. [http://dx.doi.org/10.1007/s00125-005-1802-7] [PMID: 15971062] [114] Inaba M, Terada M, Koyama H, et al. Influence of high glucose on 1,25-dihydroxyvitamin D3induced effect on human osteoblast-like MG-63 cells. J Bone Miner Res 1995; 10(7): 1050-6. [http://dx.doi.org/10.1002/jbmr.5650100709] [PMID: 7484280] [115] Hamann C, Goettsch C, Mettelsiefen J, et al. Delayed bone regeneration and low bone mass in a rat model of insulin-resistant type 2 diabetes mellitus is due to impaired osteoblast function. Am J Physiol

182 The Role of Nitric Oxide in Type 2 Diabetes

Yousefzadeh et al.

Endocrinol Metab 2011; 301(6): E1220-8. [http://dx.doi.org/10.1152/ajpendo.00378.2011] [PMID: 21900121] [116] Lattanzio S, Santilli F, Liani R, et al. Circulating dickkopf-1 in diabetes mellitus: association with platelet activation and effects of improved metabolic control and low-dose aspirin. J Am Heart Assoc 2014; 3(4): e001000. [http://dx.doi.org/10.1161/JAHA.114.001000] [PMID: 25037197] [117] Wei J, Shimazu J, Makinistoglu MP, et al. Glucose Uptake and Runx2 Synergize to Orchestrate Osteoblast Differentiation and Bone Formation. Cell 2015; 161(7): 1576-91. [http://dx.doi.org/10.1016/j.cell.2015.05.029] [PMID: 26091038] [118] Picke AK, Salbach-Hirsch J, Hintze V, et al. Sulfated hyaluronan improves bone regeneration of diabetic rats by binding sclerostin and enhancing osteoblast function. Biomaterials 2016; 96: 11-23. [http://dx.doi.org/10.1016/j.biomaterials.2016.04.013] [PMID: 27131598] [119] Kalyanaraman H, et al. Kalyanaraman, H., et al., Protein Kinase G Activation Reverses Oxidative Stress and Restores Osteoblast Function and Bone Formation in Male Mice With Type 1 Diabetes. 2018; 607-23. [120] Hofbauer LC, Brueck CC, Singh SK, Dobnig H. Osteoporosis in patients with diabetes mellitus. J Bone Miner Res 2007; 22(9): 1317-28. [http://dx.doi.org/10.1359/jbmr.070510] [PMID: 17501667] [121] McFarlane SI, Muniyappa R, Shin JJ, Bahtiyar G, Sowers JR. Osteoporosis and cardiovascular disease: brittle bones and boned arteries, is there a link? Endocr J 2004; 23(1): 01-10. [http://dx.doi.org/10.1385/ENDO:23:1:01] [PMID: 15034190] [122] Costantini S, Conte C. Bone health in diabetes and prediabetes. World J Diabetes 2019; 10(8): 421-45. [http://dx.doi.org/10.4239/wjd.v10.i8.421] [PMID: 31523379] [123] Gunczler P, Lanes R, Paz-Martinez V, et al. Decreased lumbar spine bone mass and low bone turnover in children and adolescents with insulin dependent diabetes mellitus followed longitudinally. J Pediatr Endocrinol Metab 1998; 11(3): 413-9. [http://dx.doi.org/10.1515/JPEM.1998.11.3.413] [PMID: 11517957] [124] Gunczler P, Lanes R, Paoli M, Martinis R, Villaroel O, Weisinger JR. Decreased bone mineral density and bone formation markers shortly after diagnosis of clinical type 1 diabetes mellitus. J Pediatr Endocrinol Metab 2001; 14(5): 525-8. [http://dx.doi.org/10.1515/JPEM.2001.14.5.525] [PMID: 11393573] [125] Hie M, Iitsuka N, Otsuka T, Tsukamoto I. Insulin-dependent diabetes mellitus decreases osteoblastogenesis associated with the inhibition of Wnt signaling through increased expression of Sost and Dkk1 and inhibition of Akt activation. Int J Mol Med 2011; 28(3): 455-62. [PMID: 21567076] [126] Silva JAF, Lopes Ferrucci D, Peroni LA, et al. Periodontal disease-associated compensatory expression of osteoprotegerin is lost in type 1 diabetes mellitus and correlates with alveolar bone destruction by regulating osteoclastogenesis. Cells Tissues Organs 2012; 196(2): 137-50. [http://dx.doi.org/10.1159/000330879] [PMID: 22301390] [127] Oei L, Rivadeneira F, Zillikens MC, Oei EHG. Diabetes, diabetic complications, and fracture risk. Curr Osteoporos Rep 2015; 13(2): 106-15. [http://dx.doi.org/10.1007/s11914-015-0260-5] [PMID: 25648962] [128] Brown SA, Sharpless JL. Osteoporosis: an under-appreciated complication of diabetes. Clin Diabetes 2004; 22(1): 10-20. [http://dx.doi.org/10.2337/diaclin.22.1.10] [129] Schwartz AV, Hillier TA, Sellmeyer DE, et al. Older women with diabetes have a higher risk of falls: a prospective study. Diabetes Care 2002; 25(10): 1749-54. [http://dx.doi.org/10.2337/diacare.25.10.1749] [PMID: 12351472]

NO, T2D, and Osteoporosis

The Role of Nitric Oxide in Type 2 Diabetes 183

[130] Alikhani M, Alikhani Z, Boyd C, et al. Advanced glycation end products stimulate osteoblast apoptosis via the MAP kinase and cytosolic apoptotic pathways. Bone 2007; 40(2): 345-53. [http://dx.doi.org/10.1016/j.bone.2006.09.011] [PMID: 17064973] [131] Bucala R, Tracey KJ, Cerami A. Advanced glycosylation products quench nitric oxide and mediate defective endothelium-dependent vasodilatation in experimental diabetes. J Clin Invest 1991; 87(2): 432-8. [http://dx.doi.org/10.1172/JCI115014] [PMID: 1991829] [132] Mordwinkin NM, Meeks CJ, Jadhav SS, et al. Angiotensin-(1-7) administration reduces oxidative stress in diabetic bone marrow. Endocrinology 2012; 153(5): 2189-97. [http://dx.doi.org/10.1210/en.2011-2031] [PMID: 22434085] [133] Bhatta A, Sangani R, Kolhe R, et al. Deregulation of arginase induces bone complications in highfat/high-sucrose diet diabetic mouse model. Mol Cell Endocrinol 2016; 422: 211-20. [http://dx.doi.org/10.1016/j.mce.2015.12.005] [PMID: 26704078] [134] Cao C, Zhang H, Gong L, He Y, Zhang N. High glucose conditions suppress the function of bone marrow-derived endothelial progenitor cells via inhibition of the eNOS-caveolin-1 complex. Mol Med Rep 2012; 5(2): 341-6. [PMID: 22020343] [135] Aicher A, Heeschen C, Mildner-Rihm C, et al. Essential role of endothelial nitric oxide synthase for mobilization of stem and progenitor cells. Nat Med 2003; 9(11): 1370-6. [http://dx.doi.org/10.1038/nm948] [PMID: 14556003] [136] Feng X, McDonald JM. Disorders of bone remodeling. Annu Rev Pathol 2011; 6(1): 121-45. [http://dx.doi.org/10.1146/annurev-pathol-011110-130203] [PMID: 20936937] [137] Hadjidakis DJ, Androulakis II. Bone Remodeling. Ann N Y Acad Sci 2006; 1092(1): 385-96. [http://dx.doi.org/10.1196/annals.1365.035] [PMID: 17308163] [138] Clarke B. Normal bone anatomy and physiology. Clin J Am Soc Nephrol 2008; 3 (Suppl. 3): S131-9. [http://dx.doi.org/10.2215/CJN.04151206] [PMID: 18988698] [139] Kobayashi S, Takahashi HE, Ito A, et al. Trabecular minimodeling in human iliac bone☆☆Sources of funding for the article: This study was supported in part by a Health Sciences Research Grant for Comprehensive Research on Aging and Health from the Ministry of Health, Welfare, and Labor of Japan. Bone 2003; 32(2): 163-9. [http://dx.doi.org/10.1016/S8756-3282(02)00947-X] [PMID: 12633788] [140] Rosen CJ. The epidemiology and pathogenesis of osteoporosis, in Endotext [Internet]. 2017. [141] Hsu H, Lacey DL, Dunstan CR, et al. Tumor necrosis factor receptor family member RANK mediates osteoclast differentiation and activation induced by osteoprotegerin ligand. Proc Natl Acad Sci USA 1999; 96(7): 3540-5. [http://dx.doi.org/10.1073/pnas.96.7.3540] [PMID: 10097072] [142] Lacey DL, Timms E, Tan HL, et al. Osteoprotegerin ligand is a cytokine that regulates osteoclast differentiation and activation. Cell 1998; 93(2): 165-76. [http://dx.doi.org/10.1016/S0092-8674(00)81569-X] [PMID: 9568710] [143] Grimaud E, Soubigou L, Couillaud S, et al. Receptor activator of nuclear factor kappaB ligand (RANKL)/osteoprotegerin (OPG) ratio is increased in severe osteolysis. Am J Pathol 2003; 163(5): 2021-31. [http://dx.doi.org/10.1016/S0002-9440(10)63560-2] [PMID: 14578201] [144] Kong YY, Feige U, Sarosi I, et al. Activated T cells regulate bone loss and joint destruction in adjuvant arthritis through osteoprotegerin ligand. Nature 1999; 402(6759): 304-9. [http://dx.doi.org/10.1038/46303] [PMID: 10580503] [145] Simonet WS, Lacey DL, Dunstan CR, et al. Osteoprotegerin: a novel secreted protein involved in the

184 The Role of Nitric Oxide in Type 2 Diabetes

Yousefzadeh et al.

regulation of bone density. Cell 1997; 89(2): 309-19. [http://dx.doi.org/10.1016/S0092-8674(00)80209-3] [PMID: 9108485] [146] de Amorim FPLG, Ornelas SS, Diniz SF, Batista AC, da Silva TA. Imbalance of RANK, RANKL and OPG expression during tibial fracture repair in diabetic rats. J Mol Histol 2008; 39(4): 401-8. [http://dx.doi.org/10.1007/s10735-008-9178-x] [PMID: 18592139] [147] Boyle WJ, Simonet WS, Lacey DL. Osteoclast differentiation and activation. Nature 2003; 423(6937): 337-42. [http://dx.doi.org/10.1038/nature01658] [PMID: 12748652] [148] Karst M, Gorny G, Galvin RJS, Oursler MJ. Roles of stromal cell RANKL, OPG, and M-CSF expression in biphasic TGF-β regulation of osteoclast differentiation. J Cell Physiol 2004; 200(1): 99106. [http://dx.doi.org/10.1002/jcp.20036] [PMID: 15137062] [149] Faienza MF, Ventura A, Marzano F, Cavallo L. Postmenopausal osteoporosis: the role of immune system cells. Clin Dev Immunol 2013; 2013: 1-6. [http://dx.doi.org/10.1155/2013/575936] [PMID: 23762093] [150] Raisz LG. Pathogenesis of osteoporosis: concepts, conflicts, and prospects. J Clin Invest 2005; 115(12): 3318-25. [http://dx.doi.org/10.1172/JCI27071] [PMID: 16322775] [151] Kenkre JS, Bassett JHD. The bone remodelling cycle. Ann Clin Biochem 2018; 55(3): 308-27. [http://dx.doi.org/10.1177/0004563218759371] [PMID: 29368538] [152] Eriksen EF. Cellular mechanisms of bone remodeling. Rev Endocr Metab Disord 2010; 11(4): 219-27. [http://dx.doi.org/10.1007/s11154-010-9153-1] [PMID: 21188536] [153] Raggatt LJ, Partridge NC. Cellular and molecular mechanisms of bone remodeling. J Biol Chem 2010; 285(33): 25103-8. [http://dx.doi.org/10.1074/jbc.R109.041087] [PMID: 20501658] [154] Bonewald LF. Osteocytes as dynamic multifunctional cells. Ann N Y Acad Sci 2007; 1116(1): 281-90. [http://dx.doi.org/10.1196/annals.1402.018] [PMID: 17646259] [155] Fox SW, Chambers TJ, Chow JW. Nitric oxide is an early mediator of the increase in bone formation by mechanical stimulation. Am J Physiol 1996; 270(6 Pt 1): E955-60. [PMID: 8764178] [156] Kalyanaraman H, Schwappacher R, Joshua J, et al. Nongenomic thyroid hormone signaling occurs through a plasma membrane-localized receptor. Sci Signal 2014; 7(326): ra48-8. [http://dx.doi.org/10.1126/scisignal.2004911] [PMID: 24847117] [157] Heino TJ, Hentunen TA, Väänänen HK. Osteocytes inhibit osteoclastic bone resorption through transforming growth factor-β: Enhancement by estrogen. J Cell Biochem 2002; 85(1): 185-97. [http://dx.doi.org/10.1002/jcb.10109] [PMID: 11891862] [158] van Bezooijen RL, Roelen BAJ, Visser A, et al. Sclerostin is an osteocyte-expressed negative regulator of bone formation, but not a classical BMP antagonist. J Exp Med 2004; 199(6): 805-14. [http://dx.doi.org/10.1084/jem.20031454] [PMID: 15024046] [159] Li X, Zhang Y, Kang H, et al. Sclerostin binds to LRP5/6 and antagonizes canonical Wnt signaling. J Biol Chem 2005; 280(20): 19883-7. [http://dx.doi.org/10.1074/jbc.M413274200] [PMID: 15778503] [160] Robling AG, Niziolek PJ, Baldridge LA, et al. Mechanical stimulation of bone in vivo reduces osteocyte expression of Sost/sclerostin. J Biol Chem 2008; 283(9): 5866-75. [http://dx.doi.org/10.1074/jbc.M705092200] [PMID: 18089564] [161] Gasser JA, Kneissel M. Bone physiology and biology. Bone toxicology. Springer 2017; pp. 27-94. [http://dx.doi.org/10.1007/978-3-319-56192-9_2]

NO, T2D, and Osteoporosis

The Role of Nitric Oxide in Type 2 Diabetes 185

[162] Arias CF, Herrero MA, Echeverri LF, Oleaga GE, López JM. Bone remodeling: A tissue-level process emerging from cell-level molecular algorithms. PLoS One 2018; 13(9): e0204171. [http://dx.doi.org/10.1371/journal.pone.0204171] [PMID: 30231062] [163] Henriksen K, Bollerslev J, Everts V, Karsdal MA. Osteoclast activity and subtypes as a function of physiology and pathology--implications for future treatments of osteoporosis. Endocr Rev 2011; 32(1): 31-63. [http://dx.doi.org/10.1210/er.2010-0006] [PMID: 20851921] [164] Gyurko R, Shoji H, Battaglino RA, et al. Inducible nitric oxide synthase mediates bone development and P. gingivalis-induced alveolar bone loss. Bone 2005; 36(3): 472-9. [http://dx.doi.org/10.1016/j.bone.2004.12.002] [PMID: 15777672] [165] Alselami NM, Noureldeen AFN, AL-Ghamdi MA, Khan JA, Moselhy SS. Bone turnover biomarkers in obese postmenopausal Saudi women with type-ІІ diabetes mellitus. Afr Health Sci 2015; 15(1): 906. [http://dx.doi.org/10.4314/ahs.v15i1.12] [PMID: 25834535] [166] Franz-Odendaal TA, Hall BK, Witten PE. Buried alive: How osteoblasts become osteocytes. Dev Dyn 2006; 235(1): 176-90. [http://dx.doi.org/10.1002/dvdy.20603] [PMID: 16258960] [167] Yang S, Guo L, Su Y, et al. Nitric oxide balances osteoblast and adipocyte lineage differentiation via the JNK/MAPK signaling pathway in periodontal ligament stem cells. Stem Cell Res Ther 2018; 9(1): 118. [http://dx.doi.org/10.1186/s13287-018-0869-2] [PMID: 29716662] [168] Aguirre J, Buttery L, O’Shaughnessy M, et al. Endothelial nitric oxide synthase gene-deficient mice demonstrate marked retardation in postnatal bone formation, reduced bone volume, and defects in osteoblast maturation and activity. Am J Pathol 2001; 158(1): 247-57. [http://dx.doi.org/10.1016/S0002-9440(10)63963-6] [PMID: 11141498] [169] Zhao S, Mugabo Y, Ballentine G, et al. α/β-Hydrolase Domain 6 Deletion Induces Adipose Browning and Prevents Obesity and Type 2 Diabetes. Cell Rep 2016; 14(12): 2872-88. [http://dx.doi.org/10.1016/j.celrep.2016.02.076] [PMID: 26997277] [170] Rosen ED, Sarraf P, Troy AE, et al. PPAR gamma is required for the differentiation of adipose tissue in vivo and in vitro. Mol Cell 1999; 4(4): 611-7. [http://dx.doi.org/10.1016/S1097-2765(00)80211-7] [PMID: 10549292] [171] Hikiji H, Shin WS, Oida S, Takato T, Koizumi T, Toyo-oka T. Direct action of nitric oxide on osteoblastic differentiation. FEBS Lett 1997; 410(2-3): 238-42. [http://dx.doi.org/10.1016/S0014-5793(97)00597-8] [PMID: 9237637] [172] Inoue A, Hiruma Y, Hirose S, Yamaguchi A, Hagiwara H. Reciprocal regulation by cyclic nucleotides of the differentiation of rat osteoblast-like cells and mineralization of nodules. Biochem Biophys Res Commun 1995; 215(3): 1104-10. [http://dx.doi.org/10.1006/bbrc.1995.2577] [PMID: 7488037] [173] Pun KK, Lau P, Ho PWM. The characterization, regulation, and function of insulin receptors on osteoblast-like clonal osteosarcoma cell line. J Bone Miner Res 1989; 4(6): 853-62. [http://dx.doi.org/10.1002/jbmr.5650040610] [PMID: 2692404] [174] Bakker AD, da Silva VC, Krishnan R, et al. Tumor necrosis factor α and interleukin-1β modulate calcium and nitric oxide signaling in mechanically stimulated osteocytes. Arthritis Rheum 2009; 60(11): 3336-45. [http://dx.doi.org/10.1002/art.24920] [PMID: 19877030] [175] Collin-Osdoby P, Rothe L, Bekker S, Anderson F, Osdoby P. Decreased nitric oxide levels stimulate osteoclastogenesis and bone resorption both in vitro and in vivo on the chick chorioallantoic membrane in association with neoangiogenesis. J Bone Miner Res 2000; 15(3): 474-88.

186 The Role of Nitric Oxide in Type 2 Diabetes

Yousefzadeh et al.

[http://dx.doi.org/10.1359/jbmr.2000.15.3.474] [PMID: 10750562] [176] Pezhman L, et al. The impact of forced swimming on expression of RANKL and OPG in a type 2 diabetes mellitus rat model. > 2019; 195-200. [http://dx.doi.org/10.1080/13813455.2018.1446178] [177] Deng J, Abbas U, Chang O, Dhivagaran T, Sanger S, Bozzo A. Antidiabetic and antiosteoporotic pharmacotherapies for prevention and treatment of type 2 diabetes-induced bone disease: protocol for two network meta-analyses. BMJ Open 2020; 10(1): e034741-1. [http://dx.doi.org/10.1136/bmjopen-2019-034741] [PMID: 32014879] [178] Molinuevo MS, Schurman L, McCarthy AD, et al. Effect of metformin on bone marrow progenitor cell differentiation: In vivo and in vitro studies. J Bone Miner Res 2010; 25(2): 211-21. [http://dx.doi.org/10.1359/jbmr.090732] [PMID: 19594306] [179] McCarthy AD, Cortizo AM, Sedlinsky C. Metformin revisited: Does this regulator of AMP-activated protein kinase secondarily affect bone metabolism and prevent diabetic osteopathy. World J Diabetes 2016; 7(6): 122-33. [http://dx.doi.org/10.4239/wjd.v7.i6.122] [PMID: 27022443] [180] Jeyabalan J, Shah M, Viollet B, Chenu C. AMP-activated protein kinase pathway and bone metabolism. J Endocrinol 2012; 212(3): 277-90. [http://dx.doi.org/10.1530/JOE-11-0306] [PMID: 21903861] [181] Zhao J, Yue W, Zhu MJ, Sreejayan N, Du M. AMP-activated protein kinase (AMPK) cross-talks with canonical Wnt signaling via phosphorylation of β-catenin at Ser 552. Biochem Biophys Res Commun 2010; 395(1): 146-51. [http://dx.doi.org/10.1016/j.bbrc.2010.03.161] [PMID: 20361929] [182] El-Mir MY, Nogueira V, Fontaine E, Avéret N, Rigoulet M, Leverve X. Dimethylbiguanide inhibits cell respiration via an indirect effect targeted on the respiratory chain complex I. J Biol Chem 2000; 275(1): 223-8. [http://dx.doi.org/10.1074/jbc.275.1.223] [PMID: 10617608] [183] Stage TB, Christensen MMH, Jørgensen NR, et al. Effects of metformin, rosiglitazone and insulin on bone metabolism in patients with type 2 diabetes. Bone 2018; 112: 35-41. [http://dx.doi.org/10.1016/j.bone.2018.04.004] [PMID: 29654849] [184] Jiating L, Buyun J, Yinchang Z. Role of Metformin on Osteoblast Differentiation in Type 2 Diabetes. BioMed Res Int 2019; 2019: 1-6. [http://dx.doi.org/10.1155/2019/9203934] [PMID: 31886264] [185] Lee YS, Kim YS, Lee SY, et al. AMP kinase acts as a negative regulator of RANKL in the differentiation of osteoclasts. Bone 2010; 47(5): 926-37. [http://dx.doi.org/10.1016/j.bone.2010.08.001] [PMID: 20696287] [186] Herrero MB, Viggiano JM, Perez MS, de GMF. Effects of nitric oxide synthase inhibitors on the outcome of in vitro fertilization in the mouse. Reprod Fertil Dev 1996; 8(2): 301-4. [http://dx.doi.org/10.1071/RD9960301] [PMID: 8726870] [187] Sambe T, Mason RP, Dawoud H, Bhatt DL, Malinski T. Metformin treatment decreases nitroxidative stress, restores nitric oxide bioavailability and endothelial function beyond glucose control. Biomed Pharmacother 2018; 98: 149-56. [http://dx.doi.org/10.1016/j.biopha.2017.12.023] [PMID: 29253762] [188] Morley JE, Flood JF. Evidence that nitric oxide modulates food intake in mice. Life Sci 1991; 49(10): 707-11. [http://dx.doi.org/10.1016/0024-3205(91)90102-H] [PMID: 1875780] [189] De Luca B, Monda M, Sullo A. Changes in eating behavior and thermogenic activity following inhibition of nitric oxide formation. Am J Physiol 1995; 268(6 Pt 2): R1533-8. [PMID: 7611531]

NO, T2D, and Osteoporosis

The Role of Nitric Oxide in Type 2 Diabetes 187

[190] Ye Y, Zhao C, Liang J, Yang Y, Yu M, Qu X. Effect of Sodium-Glucose Co-transporter 2 Inhibitors on Bone Metabolism and Fracture Risk. Front Pharmacol 2019; 9: 1517-7. [http://dx.doi.org/10.3389/fphar.2018.01517] [PMID: 30670968] [191] Tang J, Hu Y, Wu Y. Therapeutic effect of zoledronic acid on diabetic osteoporosis. Mod Diagn Treat 2016; 11: 2047-8. [192] Palermo A, D’Onofrio L, Eastell R, Schwartz AV, Pozzilli P, Napoli N. Oral anti-diabetic drugs and fracture risk, cut to the bone: safe or dangerous? A narrative review. Osteoporos Int 2015; 26(8): 2073-89. [http://dx.doi.org/10.1007/s00198-015-3123-0] [PMID: 25910746] [193] Chau DL, Edelman SV. Osteoporosis and Diabetes. Clin Diabetes 2002; 20(3): 153-7. [http://dx.doi.org/10.2337/diaclin.20.3.153] [194] Ward LM, Rauch F. Anabolic Therapy for the Treatment of Osteoporosis in Childhood. Curr Osteoporos Rep 2018; 16(3): 269-76. [http://dx.doi.org/10.1007/s11914-018-0434-z] [PMID: 29589203] [195] Nemeth EF, Goodman WG. Calcimimetic and Calcilytic Drugs: Feats, Flops, and Futures. Calcif Tissue Int 2016; 98(4): 341-58. [http://dx.doi.org/10.1007/s00223-015-0052-z] [PMID: 26319799] [196] Nemeth EF, Delmar EG, Heaton WL, et al. Calcilytic compounds: potent and selective Ca2+ receptor antagonists that stimulate secretion of parathyroid hormone. J Pharmacol Exp Ther 2001; 299(1): 32331. [PMID: 11561095] [197] John MR, Widler L, Gamse R, et al. ATF936, a novel oral calcilytic, increases bone mineral density in rats and transiently releases parathyroid hormone in humans. Bone 2011; 49(2): 233-41. [http://dx.doi.org/10.1016/j.bone.2011.04.007] [PMID: 21514409] [198] Lim SY, Bolster M. Profile of romosozumab and its potential in the management of osteoporosis. Drug Des Devel Ther 2017; 11: 1221-31. [http://dx.doi.org/10.2147/DDDT.S127568] [PMID: 28458516] [199] Fabre S, Funck-Brentano T, Cohen-Solal M. Anti-Sclerostin Antibodies in Osteoporosis and Other Bone Diseases. J Clin Med 2020; 9(11): 3439. [http://dx.doi.org/10.3390/jcm9113439] [PMID: 33114755] [200] Kanazawa I. Interaction between bone and glucose metabolism [Review]. Endocr J 2017; 64(11): 1043-53. [http://dx.doi.org/10.1507/endocrj.EJ17-0323] [PMID: 28966224] [201] Austin LA, Heath H III. Calcitonin. N Engl J Med 1981; 304(5): 269-78. [http://dx.doi.org/10.1056/NEJM198101293040505] [PMID: 7003392] [202] Khosla S, Hofbauer LC. Osteoporosis treatment: recent developments and ongoing challenges. Lancet Diabetes Endocrinol 2017; 5(11): 898-907. [http://dx.doi.org/10.1016/S2213-8587(17)30188-2] [PMID: 28689769] [203] Gattereau A, Bielmann P, Durivage J, Davignon J, Larochelle P. Effect of acute and chronic administration of calcitonin on serum glucose in patients with Paget’s disease of bone. J Clin Endocrinol Metab 1980; 51(2): 354-7. [http://dx.doi.org/10.1210/jcem-51-2-354] [PMID: 7400300] [204] Russo J, Russo IH. The role of estrogen in the initiation of breast cancer. J Steroid Biochem Mol Biol 2006; 102(1-5): 89-96. [http://dx.doi.org/10.1016/j.jsbmb.2006.09.004] [PMID: 17113977] [205] Mauvais-Jarvis F, Clegg DJ, Hevener AL. The role of estrogens in control of energy balance and glucose homeostasis. Endocr Rev 2013; 34(3): 309-38.

188 The Role of Nitric Oxide in Type 2 Diabetes

Yousefzadeh et al.

[http://dx.doi.org/10.1210/er.2012-1055] [PMID: 23460719] [206] Chen F, OuYang Y, Ye T, Ni B, Chen A. Estrogen inhibits RANKL-induced osteoclastic differentiation by increasing the expression of TRPV5 channel. J Cell Biochem 2014; 115(4): 651-8. [http://dx.doi.org/10.1002/jcb.24700] [PMID: 24150765] [207] Morita M, Sato Y, Iwasaki R, et al. Selective Estrogen Receptor Modulators Suppress Hif1α Protein Accumulation in Mouse Osteoclasts. PLoS One 2016; 11(11): e0165922. [http://dx.doi.org/10.1371/journal.pone.0165922] [PMID: 27802325] [208] Khosla S, Burr D, Cauley J, et al. American Society for Bone and Mineral Research. Bisphosphonateassociated osteonecrosis of the jaw: report of a task force of the American Society for Bone and Mineral Research. J Bone Miner Res 2007; 22(10): 1479-91. [http://dx.doi.org/10.1359/jbmr.0707onj] [PMID: 17663640] [209] Russell RGG. Bisphosphonates: The first 40years. Bone 2011; 49(1): 2-19. [http://dx.doi.org/10.1016/j.bone.2011.04.022] [PMID: 21555003] [210] Burr DB, Liu Z, Allen MR. Duration-dependent effects of clinically relevant oral alendronate doses on cortical bone toughness in beagle dogs. Bone 2015; 71: 58-62. [http://dx.doi.org/10.1016/j.bone.2014.10.010] [PMID: 25445446] [211] Zhang N, Zhang ZK, Yu Y, Zhuo Z, Zhang G, Zhang BT. Pros and Cons of Denosumab Treatment for Osteoporosis and Implication for RANKL Aptamer Therapy. Front Cell Dev Biol 2020; 8: 325. [http://dx.doi.org/10.3389/fcell.2020.00325] [PMID: 32478071] [212] Tsourdi E, Langdahl B, Cohen-Solal M, et al. Discontinuation of Denosumab therapy for osteoporosis: A systematic review and position statement by ECTS. Bone 2017; 105: 11-7. [http://dx.doi.org/10.1016/j.bone.2017.08.003] [PMID: 28789921] [213] Mohsin S, Baniyas MMYH, AlDarmaki RSMH, Tekes K, Kalász H, Adeghate EA. An update on therapies for the treatment of diabetes-induced osteoporosis. Expert Opin Biol Ther 2019; 19(9): 93748. [http://dx.doi.org/10.1080/14712598.2019.1618266] [PMID: 31079501] [214] Dai R, Wu Z, Chu HY, et al. Cathepsin K: The Action in and Beyond Bone. Front Cell Dev Biol 2020; 8: 433. [http://dx.doi.org/10.3389/fcell.2020.00433] [PMID: 32582709] [215] Ilich JZ, Kerstetter JE. Nutrition in bone health revisited: a story beyond calcium. J Am Coll Nutr 2000; 19(6): 715-37. [http://dx.doi.org/10.1080/07315724.2000.10718070] [PMID: 11194525] [216] Li K, Wang XF, Li DY, et al. The good, the bad, and the ugly of calcium supplementation: a review of calcium intake on human health. Clin Interv Aging 2018; 13: 2443-52. [http://dx.doi.org/10.2147/CIA.S157523] [PMID: 30568435] [217] Pettway GJ, Meganck JA, Koh AJ, Keller ET, Goldstein SA, McCauley LK. Parathyroid hormone mediates bone growth through the regulation of osteoblast proliferation and differentiation. Bone 2008; 42(4): 806-18. [http://dx.doi.org/10.1016/j.bone.2007.11.017] [PMID: 18234576] [218] Tella SH, Gallagher JC. Biological agents in management of osteoporosis. Eur J Clin Pharmacol 2014; 70(11): 1291-301. [http://dx.doi.org/10.1007/s00228-014-1735-5] [PMID: 25204309] [219] Neer RM, Arnaud CD, Zanchetta JR, et al. Effect of parathyroid hormone (1-34) on fractures and bone mineral density in postmenopausal women with osteoporosis. N Engl J Med 2001; 344(19): 1434-41. [http://dx.doi.org/10.1056/NEJM200105103441904] [PMID: 11346808] [220] Tella SH, Kommalapati A, Correa R. Profile of Abaloparatide and Its Potential in the Treatment of Postmenopausal Osteoporosis. Cureus 2017; 9(5): e1300. [http://dx.doi.org/10.7759/cureus.1300] [PMID: 28680788]

NO, T2D, and Osteoporosis

The Role of Nitric Oxide in Type 2 Diabetes 189

[221] Karras SN, Anagnostis P, Antonopoulou V, et al. The combined effect of vitamin D and parathyroid hormone concentrations on glucose homeostasis in older patients with prediabetes: A cross-sectional study. Diab Vasc Dis Res 2018; 15(2): 150-3. [http://dx.doi.org/10.1177/1479164117738443] [PMID: 29113459] [222] Takakura A, Lee JW, Hirano K, et al. Administration frequency as well as dosage of PTH are associated with development of cortical porosity in ovariectomized rats. Bone Res 2017; 5(1): 17002. [http://dx.doi.org/10.1038/boneres.2017.2] [PMID: 28503340] [223] Rejnmark L, Vestergaard P, Mosekilde L. Decreased fracture risk in users of organic nitrates: a nationwide case-control study. J Bone Miner Res 2006; 21(11): 1811-7. [http://dx.doi.org/10.1359/jbmr.060804] [PMID: 17054422] [224] Pouwels S, Lalmohamed A, van Staa T, et al. Use of organic nitrates and the risk of hip fracture: a population-based case-control study. J Clin Endocrinol Metab 2010; 95(4): 1924-31. [http://dx.doi.org/10.1210/jc.2009-2342] [PMID: 20130070] [225] Wimalawansa SJ, De Marco G, Gangula P, Yallampalli C. Nitric oxide donor alleviates ovariectomyinduced bone loss. Bone 1996; 18(4): 301-4. [http://dx.doi.org/10.1016/8756-3282(96)00005-1] [PMID: 8726385] [226] Samuels A, Perry MJ, Gibson RL, Colley S, Tobias JH. Role of endothelial nitric oxide synthase in estrogen-induced osteogenesis. Bone 2001; 29(1): 24-9. [http://dx.doi.org/10.1016/S8756-3282(01)00471-9] [PMID: 11472887] [227] Hukkanen M, Platts LAM, Lawes T, et al. Effect of nitric oxide donor nitroglycerin on bone mineral density in a rat model of estrogen deficiency-induced osteopenia. Bone 2003; 32(2): 142-9. [http://dx.doi.org/10.1016/S8756-3282(02)00955-9] [PMID: 12633786] [228] Nabhan AF, Rabie NH. Isosorbide mononitrate versus alendronate for postmenopausal osteoporosis. Int J Gynaecol Obstet 2008; 103(3): 213-6. [http://dx.doi.org/10.1016/j.ijgo.2008.07.011] [PMID: 18805524] [229] Kerwin JF Jr, Lancaster JR Jr, Feldman PL. Nitric oxide: a new paradigm for second messengers. J Med Chem 1995; 38(22): 4343-62. [http://dx.doi.org/10.1021/jm00022a001] [PMID: 7473563] [230] Daiber A, Münzel T. Organic Nitrate Therapy, Nitrate Tolerance, and Nitrate-Induced Endothelial Dysfunction: Emphasis on Redox Biology and Oxidative Stress. Antioxid Redox Signal 2015; 23(11): 899-942. [http://dx.doi.org/10.1089/ars.2015.6376] [PMID: 26261901] [231] Münzel T, Daiber A. Inorganic nitrite and nitrate in cardiovascular therapy: A better alternative to organic nitrates as nitric oxide donors? Vascul Pharmacol 2018; 102: 1-10. [http://dx.doi.org/10.1016/j.vph.2017.11.003] [PMID: 29174923] [232] Ghasemi A, Jeddi S. Anti-obesity and anti-diabetic effects of nitrate and nitrite. Nitric Oxide 2017; 70: 9-24. [http://dx.doi.org/10.1016/j.niox.2017.08.003] [PMID: 28804022] [233] Lundberg JO, Carlström M, Weitzberg E. Metabolic Effects of Dietary Nitrate in Health and Disease. Cell Metab 2018; 28(1): 9-22. [http://dx.doi.org/10.1016/j.cmet.2018.06.007] [PMID: 29972800] [234] Kapil V, Khambata RS, Jones DA, et al. The Noncanonical Pathway for In Vivo Nitric Oxide Generation: The Nitrate-Nitrite-Nitric Oxide Pathway. Pharmacol Rev 2020; 72(3): 692-766. [http://dx.doi.org/10.1124/pr.120.019240] [PMID: 32576603] [235] Bahadoran Z, Jeddi S, Gheibi S, Mirmiran P, Kashfi K, Ghasemi A. Inorganic nitrate, a natural antiobesity agent: A systematic review and meta-analysis of animal studies. EXCLI J 2020; 19: 972-83. [PMID: 32788911]

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CHAPTER 9

Hyperuricemia, Type 2 Diabetes and Insulin Resistance: Role of Nitric Oxide Zahra Bahadoran1, Parvin Mirmiran1,2, Khosrow Kashfi3,4 and Asghar Ghasemi5,* Nutrition and Endocrine Research Center, Research Institute for Endocrine Sciences, Shahid Beheshti University of Medical Sciences, Tehran, Iran 2 Department of Clinical Nutrition and Human Dietetics, Faculty of Nutrition Sciences and Food Technology, National Nutrition and Food Technology Research Institute, Shahid Beheshti University of Medical Sciences, Tehran, Iran 3 Department of Molecular, Cellular, and Biomedical Sciences, Sophie Davis School of Biomedical Education, City University of New York School of Medicine, New York, NY10031, USA 4 Graduate Program in Biology, City University of New York Graduate Center, New YorkNY10016, USA 5 Endocrine Physiology Research Center, Research Institute for Endocrine Sciences, Shahid Beheshti University of Medical Sciences, Tehran, Iran 1

Abstract: Uric acid (UA) is the end product of purine catabolism in humans. Hyperuricemia, defined as elevated plasma concentrations of UA above 7 mg/dL, is a risk factor for developing hypertension, cardiovascular diseases, chronic kidney disease, and type 2 diabetes. Hyperuricemia can induce pancreatic β-cell death and impaired insulin secretion. It can also disrupt insulin-induced glucose disposal and insulin signaling in different insulin-sensitive tissues, including cardiomyocytes, skeletal muscle cells, adipocytes, hepatocytes, and endothelial cells. These events lead to the development of systemic insulin resistance and impaired glucose metabolism. Induction of inflammation, oxidative stress, and impairment of nitric oxide (NO) metabolism mediate hyperuricemia-induced insulin resistance and dysglycemia. This chapter is focused on the potential mediatory role of NO metabolism on hyperuricemia-induced dysglycemia and insulin resistance.

Keywords: Hyperuricemia, Insulin Receptor, Insulin Resistance, Type 2 Diabetes, Uric Acid.

Corresponding author Asghar Ghasemi: Endocrine Physiology Research Center, Research Institute for Endocrine Sciences, Shahid Beheshti University of Medical Sciences, Tehran, Iran; No. 24, Erabi Street, Velenjak, Tehran, Iran; Phone: +98 21 22409309; Fax: +98 21 22416264, Email: [email protected]

*

Asghar Ghasemi, Khosrow Kashfi, Zahra Bahadoran (Eds.) All rights reserved-© 2022 Bentham Science Publishers

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INTRODUCTION Uric acid (UA), the end product of adenine- and guanine-based purines catabolism in humans, is synthesized by xanthine oxidoreductase (XOR) from xanthine [1]. Both endogenous (i.e., de novo purine biosynthesis as well as cell and tissue turnover) and exogenous (i.e., dietary purines occurring in the seafood, meats, and legumes) sources of purines are involved in UA production [2 - 4]. Increased plasma concentrations of UA above 7 mg/dL (1 mg/dL ≈59.48 µM), which accompanies by a doubled amount of exchangeable pool of UA (from 1200 to 2027 mg) and also hyperuricosuria (urinary excretion of UA> 800 mg/day in men and >750 mg/day in women) [4, 5], is the primary cause of gout [6]. Hyperuricemia is a risk factor for developing cardiometabolic disorders, including hypertension [7, 8], cardiovascular diseases [9, 10], chronic kidney disease [11], type 2 diabetes (T2D) [12 - 15], and mortality [16, 17]. In addition, hyperuricemia has been suggested as a component of metabolic syndrome, the cluster of metabolic and hemodynamic abnormalities, including abdominal obesity, glucose intolerance, insulin resistance, dyslipidemia, and hypertension [18]. Although not fully established, current documents imply that increased plasma UA concentration is a causative factor for developing insulin resistance and dysglycemia [12, 13]. Several mechanisms may explain the cause-and-effect relationship between hyperuricemia and the progression of T2D; high-UA concentrations can induce pancreatic β-cell death and impaired insulin secretion [19, 20]. High-UA can also disrupt insulin-induced glucose disposal and insulin signaling in various insulinsensitive tissues, including cardiomyocytes [21], skeletal muscle cells [22], adipocytes [23], hepatocytes [24], and endothelial cells [25]; these events consequently lead to the development of systemic insulin resistance [26, 27]. Induction of oxidative stress, inflammatory processes, and impaired nitric oxide (NO) metabolism are crucial underlying mechanisms by which high-UA concentration imposes detrimental effects on glucose and insulin homeostasis. In this chapter, considering both epidemiological and experimental evidence, we discuss the potential cause-and-effect relation between hyperuricemia and T2D and insulin resistance development. Furthermore, we focus on the possible mediating role of NO in hyperuricemia-induced dysglycemia and insulin resistance.

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A BRIEF OVERVIEW OF URIC ACID METABOLISM AND FUNCTION Uric Acid Synthesis In Human: Role of XOR Uric acid is a weak hydrogenated organic acid (pKa1 of 5.75 and pKa2 of 10.3); under normal conditions, i.e., pH 7.4 and 37°C, the most predominant (~98-99%) form of UA within the circulation and synovial fluid is urate anion (i.e., monodeprotonated ionic form) [28]. Uric acid synthesis mainly occurs in the liver, whereas other tissues, such as the intestine, myocardium, kidney, and vascular endothelium, also contribute to UA synthesis to a lesser extent [29]. UA is the metabolic end product of purine in humans (due to lack of uricase); it can be, however, be diverted into further catabolism by uricase to produce allantoin in other mammals [2, 30]; loss of uricase activity in humans has been an evolutionary process, which allowed them to readily accumulate fat via the metabolism of fructose from fruits [31]. Many enzymes, including nucleotidase, adenosine deaminase, and purine nucleoside phosphorylase, participate in the purine catabolism [i.e., converting adenosine monophosphate (AMP), and guanine monophosphate (GMP) to inosine and guanosine, respectively, and then into hypoxanthine (HPX)]. XOR, which converts HPX into xanthine and then to UA, is the key and rate-limiting enzyme in the pathway [1]. Positive regulators of XOR gene expression are hypoxia, lipopolysaccharide, inflammatory cytokines [interferon γ, interleukin-1 (IL-1), interleukin-6 (IL-6), tumor necrosis factor-α (TNF-α)], dexamethasone, cortisol, and prolactin [32]. In addition to oxygen pressure, NO can also modify XOR activity; exogenous NO and also NO produced by XOR (reduction of nitrite to NO via xanthine as reducing substrate) are accompanied by the enzyme inactivation (through NOinduced conversion of xanthine to its desulfo-form) and inactivates XOR [33, 34]. The maximum XOR activity in mammals is in the liver and intestinal epithelial cells; XOR is mainly located in the cytoplasm and cell membrane through cell surface binding mediated by glycosaminoglycans [35, 36]. As reviewed elsewhere, besides purines, XOR can also catabolize different endogenous metabolites (i.e., aldehydes, pyrimidines, pteridines, azopurines, and heterocyclic compounds) and different xenobiotics (e.g., antiviral and anticancer agents) [37, 38]. Regulation of Circulating Uric Acid Levels Normal serum UA concentration is 3.5-7.2 mg/dL in adult men and postmenopausal women and 2.6-6.0 mg/dL in premenopausal women; however, a

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threshold level of < 6.0 mg/dL is suggested as a better cut off value to identify healthy subjects [39]. There are different cut-off values for defining hyperuricemia; the American College of Rheumatology (ACR) guideline set it as serum UA greater than 6.8-7.0 mg/dL, whereas European League Against Rheumatism (EULAR) 2016 guideline considered a value > 6 mg/dL [40]. Hyperuricemia is due to UA overproduction (~10%), decreased UA renal excretion (~80%), and a combined overproduction-underexcretion of UA (~10%) [41, 42]. Based on urinary UA excretion (UUE) and fractional excretion of UA (FEUA), there are three types of hyperuricemia: overproduction hyperuricemia (UUE > 25.0 mg/h/1.73 m2), underexcretion hyperuricemia (FEUA < 5.5%), and combined model; the normal condition is defined as UUE ≤ 25.0 mg/h/1.73 m2 and FEUA ≥5.5% [41]. The mean exchangeable body pool size of UA estimates to be about 1200 mg (ranging 992-1650 mg) in healthy humans (800-1500 mg in men and 500-1000 mg in women [4]), and 2027 mg (ranging 1248-3199 mg) in hyperuricemic subjects. The mean turnover rate of whole-body UA pool in healthy and hyperuricemic subjects is estimated to be ~707 mg/day (ranging 602-836 mg/day) and 861 mg/day (ranging 506-1542 mg/day) [43]. The endogenous synthesis rate of UA in the human body is estimated to be 300-400 mg/day; contribution of the dietary source is approximately 300 mg/day consuming a regular diet, and a purine-rich diet would be responsible for an increasing 1-2 mg/dL of serum UA [44, 45]. Alcohol consumption (by increasing ATP degradation and inhibiting the tubular secretion of UA) [46] and dietary fructose (by induction of xanthine oxidase activity, ATP depletion, activation of AMP deaminase, increased amounts of adenosine di- and mono-phosphates, and inhibition of UA excretion) increase UA levels [47 - 49]. About two-thirds (62.8-69.8%) [50] of UA is eliminated by the kidneys in urine (with a normal uricosuria level of 600-800 mg/day in adults [4]), and approximately one-third to one-fourth via the gastrointestinal tract [1, 5]. UA is freely filtrated in the kidney; of the filtrated load (plasma concentration of uric acid × glomerular filtration rate), 90% is reabsorbed, and therefore, fractional excretion of uric acid is ~10% (7-12%) [1, 51, 52]. Proximal tubule both reabsorbs and secrets uric acid [1]. The renal UA clearance rate in healthy subjects is ~4.5-5.9 and 8.5-9.7 ml/min under free-purine and high-purine diets, respectively [53]. Hyperuricemia is associated with hyperuricosuria, defined as urinary excretion of urate > 800 mg/day in men and >750 mg/day in women [4, 5].

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Physiologic Roles of Normal Uric Acid Levels Although physiological functions of normal levels of UA have been poorly documented, both in vitro and in vivo studies indicate that physiological concentrations of UA can exert antioxidant [54], anti-inflammatory, and chondroprotective effects [55]. About half of the total antioxidant capacity in human plasma is attributed to circulating UA [54, 56]; UA comprises ~10-15% of hydroxyl radical-scavenging and 30-65% of the peroxyl radical-scavenging capacity of plasma [54]. UA may act as an antioxidant or pro-oxidant depending on the UA concentration, the nature and concentration of free radicals, and the presence and concentration of other antioxidant mechanisms [51]. At physiological levels, UA has been suggested to act as an antioxidant to preserve endothelial NO levels, probably by preventing the uncoupling of endothelial NO synthase (eNOS) by reacting with peroxynitrite or by preventing the oxidant-induced inactivation of extracellular superoxide dismutase (SOD) [57]. Uric acid may also act as a vehicle of NO because it facilitates the reaction of NO with glutathione (by transferring a nitroso group to glutathione) and produces more S-nitrosoglutathione [58], a molecule that acts as a source of bioavailable NO and plays a critical role in mediating the downstream signaling effects of NO [59]. Uric acid is also essential for several physiological processes, including endothelial function, immune response, and defense against neurological and autoimmune diseases [29, 54]. Likewise, UA is a major antioxidant in human nasal airway secretions that acts as the major inhibitor of ozone (O3)-induced oxidation and removes inhaled O3 from the human upper airway [60, 61]. Pathological Effects of Hyperuricemia UA’s elevated serum levels lead to the deposition of monosodium urate monohydrate crystals in the supersaturated extracellular fluids of the joints and other tissues, a process mediating most of the clinical features of gout [62]. Beyond gout, as the most known pathologic feature, hyperuricemia predisposes the onset of cardiometabolic disorders [7 - 9, 11] and increases mortality risk [16, 17]. Furthermore, epidemiological evidence indicates that hyperuricemia is related to the development of vascular dysfunction and the incidence of cardiovascular diseases [63, 64]. In addition, elevated serum UA level is associated with the development of carotid atherosclerosis and unstable plaque [65]. Risk of cardiovascular disease (CVD) mortality was reported to be 2.5-fold (HR=2.53, 95% CI=1.18-5.41) at UA levels of 7-9 mg/dL, compared to UA levels of 5-7 mg/dL; among patients with T2D, UA levels of 5-7 mg/dL was an

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independent risk of CVD mortality (HR = 2.25, 95% CI=1.25-4.06) [66]. Metaanalysis of prospective cohort studies showed that hyperuricemia was related to the risk of major adverse cardiovascular events (RR= 1.72, 95% CI= 1.28-2.33) and cardiovascular diseases (RR= 1.35, 95% CI= 1.12-1.62) [67]. The overall effect (pooled estimated effect size) of hyperuricemia on the risk of coronary heart disease (CHD) mortality and all-cause mortality was 1.14 (95% CI=1.06-1.23) and 1.20 (95% CI=1.13-1.28). Each increase of 1 mg/dL of serum UA increased the risk of CHD and all-cause mortality by 20% and 9%, respectively [68]. Hyperuricemia is also related to the elevated risk of thyroid dysfunction and the development of kidney disease [69]. Moreover, some epidemiological studies indicated that elevated serum UA might be related to the risk of female reproductive disorders, e.g., polycystic ovary syndrome (PCOS), endometriosis, pregnancy complications, and adverse fetal outcomes, through induction of oxidative stress, chronic inflammation, and mitochondrial dysfunction [70]. HYPERURICEMIA, T2D AND INSULIN RESISTANCE Epidemiological Evidence Epidemiologic studies indicate that hyperuricemia is a predisposing factor in the onset of T2D. A cohort of 37,296 healthy men and women showed sex difference in the relation between serum UA and risk of T2D; higher levels of serum UA (>7.05 vs. 4.8 mg/dL, respectively); one mg/dL increment of serum UA increased risk of IFG/T2D by 66% (HR=1.66, 95% CI=1.44–1.92) [72]. Hyperglycemia is associated with IFG (OR = 2.90, 95% CI= 1.83-4.58), combined IFG/impaired glucose tolerance (IGT) (OR = 3.96, 95% CI= 1.83-8.54), and T2D (OR=2.49, 95% CI= 1.55-3.99) in women but not in men [73]. Elevated 1 mg/dL serum UA was related to a 27% increase in 5-year risk of T2D (HR=1.27, 95% CI=1.10-1.45; HR=1.21, 95% CI=1.03-1.43 in men and HR=1.34, 95% CI=1.01-1.79 in women) [74].

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A 5-year follow-up among healthy subjects showed that persistent hyperuricemia increased risk of T2D by 75% (RR =1.75, 95% CI= 1.47-2.08); a minor change of serum UA, a 10% decreased and a 30% increased, was accompanied by a 16% decreased (RR = 0.84, 95% CI = 0.72-0.99) and a 71% increased (RR = 1.71, 95% CI = 1.27-2.30) of T2D, respectively [75]. It has been investigated that body mass index could partially mediate the association of hyperuricemia with the risk of T2D, and the percentage of the mediated association is about 20.3% (95% CI=15.7-24.8%) [76]. A 6-year followup among Japanese men reported a 78% increased risk of IFG/T2D in subjects who had an elevated serum UA (>6.69 vs. 6.69 mg/dL [77]. A pooled analysis of cohort studies investigated the potential role of hyperuricemia as a risk factor of T2D, and reported a 24% attributable risk of high-serum UA for the incidence of T2D; each 1 mg/dL (~59.48 μM) increase in plasma level of UA was accompanied by a 6-17% increased risk of T2D [12, 13]. Furthermore, the activity of XOR (an important and rate-limiting enzyme in the UA biosynthesis pathway) in plasma was correlated with fasting insulin levels and homeostatic model assessment of insulin resistance (HOMA-IR) in patients with T2D and metabolic syndrome [78]. Experimental and Clinical Evidence The causal relationship between high-UA concentrations and T2D and insulin resistance is supported by the evidence that UA-lowering pharmaceutical agents, e.g., allopurinol (a xanthine oxidase inhibitor) or benzbromarone (a uricosuric agent), improve glycemic control and insulin resistance. A three-month treatment of subjects with asymptomatic hyperuricemia using allopurinol significantly improved fasting blood glucose, fasting insulin, and HOMA-IR index [79]. Following using UA-lowering drugs, improved insulin resistance in subjects with congestive heart failure [80] and reduced glycosylated hemoglobin (HbA1C) levels in patients with T2D [81] was also reported. Likewise, lowering UA concentrations improve insulin resistance in animal models of metabolic syndrome [23]. Both febuxostat and allopurinol, the xanthine oxidase inhibitors, improved glucose intolerance and insulin resistance, induced in mice fed a highfat, high-cholesterol, and high-cholate diet [82].

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Underlying Mechanisms Connecting UA to Insulin Resistance and T2D Several mechanisms explain the association between hyperuricemia and the development of T2D and insulin resistance. These mechanisms may be discussed as three main categories (1) UA-induced inflammation, (2) UA-induced oxidative stress, and (3) UA-induced impairment of NO metabolism. In this section, oxidative stress and inflammatory pathways are briefly reviewed, and the latter is discussed in more detail in the following section. Some experimental studies indicated that high-UA concentrations contribute to the development of diabetes via inhibition of AMP-activated protein kinase, leading to increased gluconeogenesis and induction of inflammation and oxidative stress [23, 83, 84]. High-UA concentrations blunt insulin signaling in insulinsensitive cells, including cardiomyocytes [21], skeletal muscle cells [22], adipocytes [23], hepatocytes [24], and endothelial cells [25]; this action is partly mediated by inducing inflammation. Hyperuricemia induces TNF-α, a potent paracrine and endocrine mediator of inflammatory pathways, which plays a crucial role in developing dysglycemia and insulin resistance [85]. High-UA concentrations induce TNF-α gene expression, and reactive oxygen species (ROS) are important mediators in the UA-induced expression of TNF-α [86]. High-UA levels also activate the nuclear factor-κB (NF-κB) and the mitogen-activated protein kinase (MAPK) signaling molecules [extracellular signal-regulated kinases (ERK) p44/42 and p38)] and cyclooxygenase-2 (COX-2) mRNA expression. These pathways are responsible for expressing several inflammatory cytokines, e.g., monocyte chemoattractant protein-1 (MCP-1) [87]. Hyperuricemia acts as a mediator of the pro-inflammatory endocrine imbalance in the adipose tissue thereby, induces systemic insulin resistance [23]. High-UA concentrations increase both mRNA expression and transcription of MCP-1, a key adipokine mediating the pro-inflammatory pathways in the adipocytes [23]; UAinduced MCP-1 production was blocked by scavenging superoxide or by inhibiting NADPH oxidase and by stimulating peroxisome-proliferator-activated receptor-γ (PPARγ) [23]. High-UA concentrations also activate NADPH oxidase and the downstream redox-dependent pro-inflammatory signaling via protein kinase p38 [88]; such data suggests that hyperuricemia may induce redoxdependent signaling and oxidative stress in the adipocytes, a major cause of systemic insulin resistance [88]. Hyperuricemia may also induce hepatic insulin resistance because a high-UA concentration induces the expression of hepatic inflammatory molecules by activating the pro-inflammatory IκB kinase/IκBα/NFκB signaling cascade [89]; high-UA concentration dose-dependently enhances the

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expression of C-reactive protein, fibrinogen, ferritin, and complement C3, markers associated with the development of insulin resistance and metabolic disorders [89]. Role of No in Hyperuricemia-Induced Dysglycemia and Insulin Resistance Hyperuricemia imposes imbalanced NO homeostasis, including inhibiting eNOSderived NO production or inducing iNOS-derived overproduction of NO, a phenomenon strongly associated with developing insulin resistance and T2D [90]. Both in vitro and animal experiments indicate that high-UA levels can inhibit NO production and reduce circulating NO; furthermore, a circadian rhythm has been identified in humans, in which UA and NO levels are inversely correlated [91]. Fig. (1) illustrates the potential effects of hyperuricemia on NO metabolism and its connection to the development of impaired carbohydrate metabolism.

Fig. (1). An overview of potential effects of high-uric acid concentrations on eNOS- and iNOS-derived nitric oxide (NO) production and its connection to impaired glucose and insulin homeostasis. eNOS, endothelial NO synthase; iNOS, inducible NO synthase. Created with BioRender.com

Inhibitory effect of UA on eNOS activity and decreased NO production is mediated by altering eNOS expression and/or phosphorylation [25, 92], by decreasing L-arginine bioavailability for eNOS ([either via increased arginase activity [92] or decreased L-arginine transport into cells [93]], or by decreasing interaction between eNOS and calmodulin (CaM, as an eNOS activator) [94]. A high-UA (~20 mg/dL) decreases eNOS expression and NO production in endothelial cells by 3-fold; this effect was mediated through stimulating the expression of intracellular high mobility group box chromosomal protein 1

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(HMGB1) and advanced glycation end products (AGEs) and activating HMGB1/AGE signaling pathway [95]. Likewise, a high-UA concentration significantly decreased eNOS expression and NO production through activation of mitochondrial Na+/Ca2+ exchanger and increased mitochondrial [Ca2+], and by increasing intracellular levels of ROS and H2O2 [96]. Another mechanism by which UA induced decreased NO availability is its direct interaction with NO, in a rapid and irreversible reaction, producing 6aminouracil [57] or nitrosated UA [58], leading to depletion of NO stores. An imbalanced NO metabolism in response to high concentrations of UA in critical tissues involved in glucose and insulin homeostasis has been suggested to mediate hyperuricemia-induced dysglycemia and insulin resistance. Uric acid inhibits NO’s bioavailability in the insulin-sensitive tissues, thereby reducing insulinstimulated glucose uptake. On the other hand, toxic levels of iNOS-derived NO in response to hyperuricemia may disturb glucose-stimulated insulin secretion (GSIS) by pancreatic β-cells. A positive association reported between serum UA and arginase activity and reduced circulating NO metabolites in patients with metabolic syndrome implies that UA-induced decreased NO bioavailability predisposes to systemic insulin resistance [97]. High-UA concentrations stimulate NADPH oxidase-dependent production of reactive oxygen species (ROS), resulting in the activation of MAP kinases p38 and ERK1/2 and a diminished NO bioavailability in adipose tissue [88]. Longterm exposure of pre-adipocytes to UA (at a concentration of 15 mg/dL UA) during adipocyte differentiation induced a dose-dependent decrease in NO bioavailability; a UA-induced decreased NO availability was due to increased NADPH oxidase activity and ROS production but not mediated by changing eNOS activation via phosphorylation of Ser1177 [88]; these events have been suggested as major causes of systemic insulin resistance [88]. We recently reviewed extensively [98] how hyperuricemia interferes with insulin signaling in endothelial cells, leading to decreased endothelial NO availability and the development of endothelial insulin resistance. High-UA concentrations inhibit insulin-induced activation and expression of eNOS and diminish NO production in endothelial cells, resulting in endothelial insulin resistance [25, 94, 99]. We described that the action of UA is mediated by interfering with insulin signaling at both the receptor and post-receptor levels. UA can directly interfere with the insulin signaling pathway at the receptor level by impairing tyrosine-kinase activity and autophosphorylation of the β-subunit of the insulin receptor, or by increasing angiotensin II (Ang-II) levels which inhibits insulin-stimulated tyrosine

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phosphorylation of the insulin receptor at its β-subunit, for more details see Fig. (2).

Fig. (2). Potential effects of high uric acid (UA) levels on endothelial nitric oxide (NO) production. High-UA disturbs eNOS activation by impairing insulin signaling at receptor and post-receptor levels (i.e., proximal IRS and PI3K-Akt components, and distal eNOS-NO system). High-UA concentrations also decrease eNOS expression or disturb its activity by decreasing intracellular Ca+2 and/or making eNOS uncoupled. High-UA concentrations may also activate arginase and decrease substrate (L-arg) level for eNOS. Ang-II, angiotensin II; Akt, protein kinase B; AP-1, activator protein 1; CaM, calmodulin; CRP, C-reactive protein; eNOS, endothelial NO synthase; ENPP1, ectonucleotide pyrophosphatase/phosphodiesterase 1; ERK, extracellular signal-regulated kinases; ICAM-1, intercellular adhesion molecule; IL-6, interleukin-6; IL-1β, interleukin-1β; IRS, insulin receptor substrate; L-arg, L-arginine; MAPK, mitogen-activated protein kinase; MCP-1; monocyte chemoattractant protein-1; NF-κB, transcription factor nuclear factor kappa B; Orn, ornithine; PI3K, phosphatidylinositol 3-kinase; PKC, protein kinase C; ROS, reactive oxygen species; TNF-α, tumor necrosis factor-α; VCAM-1, vascular cell adhesion molecule. Created with BioRender.com.

At the proximal post-receptor level, UA disrupts the action of insulin receptor substrate (IRS) and phosphatidylinositol 3-kinase (PI3K)/protein kinase B (Akt) in the insulin signaling pathway. At the distal post-receptor level, high-UA

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concentrations impair the eNOS-NO system by decreasing eNOS expression and activity and by direct inactivation of NO see Fig. (2). Although no direct evidence is available, UA-induced insulin resistance in inulinsensitive tissues may be mediated by the impairment of the eNOS-NO system in these organs. High-UA concentrations impaired insulin signaling in the liver, skeletal muscle, and adipose tissue by inhibiting insulin-stimulated IRSphosphorylation at Ser307 and Akt phosphorylation at Ser473 [24], the upstream pathways of eNOS phosphorylation and activation [90]. Therefore, it can be speculated that similar NO-dependent mechanisms, aforementioned for the endothelial cells, mediate hyperuricemia-induced insulin resistance in the liver, skeletal muscle, and adipose tissue. On the other hand, a high-UA concentration can be highly toxic and induce pancreatic β-cell dysfunction, impairing insulin secretion [19, 20]. The underlying mechanisms by which high-UA concentrations induce pancreatic β-cells dysfunction has not been well elucidated. We recently discussed [20] that highUA-induced β-cell dysfunction seems to be mediated via two principal mechanisms, including the NF-κB-iNOS-NO signaling pathway and ROS-AMP activated protein kinase (AMPK)- ERK signaling pathway see Fig. (3). The deleterious effect of high-UA concentration on β-cell is partially mediated through activation of the NF-κB signaling pathway leading to upregulation of iNOS expression and excessive NO production [100]. Furthermore, the expression of MafA (i.e., an essential transcriptional regulator of islet β-cells) is inhibited by UA-stimulated overproduction of NO, leading to pancreatic β-cell dysfunction [100]. CONCLUDING REMARKS The available evidence indicates that hyperuricemia is an independent risk factor for developing insulin resistance and T2D. High-UA concentrations exhibit deleterious effects on carbohydrate metabolism due to impairing NO metabolism and decreasing its availability. A high-intracellular UA concentration decreases the responsiveness of the endothelial cells to insulin, resulting in the development of endothelial insulin resistance. Limited direct evidence is available in other insulin-sensitive cells, including skeletal muscle, adipocytes, and hepatocytes. UA seems to impair insulin signaling probably through impairment of the eNOS-NO system. In addition, toxic NO levels produced via UA-stimulated iNOS overexpression/overactivity in the pancreatic β-cells has detrimental effects on insulin secretion and β-cell function. Future clinical trials will show whether UAlowering drugs have beneficial effects in preventing cardiometabolic disorders, including T2D.

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Fig. (3). Mechanisms underlying uric acid (UA)-induced β-cell dysfunction. UA probably enters the β-cells via glucose transporter 9 (GLUT9). Intracellular UA increases reactive oxygen species (ROS), which phosphorylates and activates AMP-activated protein kinase (AMPK) and then extracellular signal-regulated kinase (ERK). Phosphorylated ERK causes β-cell apoptosis. UA also phosphorylates and degrades inhibitor of kappa B (IκB) that permits the transcription factor nuclear factor kappa B (NF-κB) to enter the nucleus and increases expression of inducible nitric oxide synthase (iNOS). NO overproduction decreases glucosestimulated insulin secretion (GSIS) and causes β-cell apoptosis. CXCL-1, chemokine (C-X-C motif) ligand 1; MCP-1, monocyte chemoattractant protein-1; IL-6, interleukin-6. Reproduced with no change from Ghasemi A, Uric acid-induced pancreatic β-cell dysfunction. 2021;21(1):24. BMC Endocrine Disorders [20] underhttp://creativecommons.org/publicdomain/zero/1.0.

CONSENT OF PUBLICATION Permission from BMC Endocrine Disorders for (Fig. (3)) CONFLICT OF INTEREST The author declares no conflict of interest, financial or otherwise. ACKNOWLEDGEMENT Declared none.

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REFERENCES [1]

Maiuolo J, Oppedisano F, Gratteri S, Muscoli C, Mollace V. Regulation of uric acid metabolism and excretion. Int J Cardiol 2016; 213: 8-14. [http://dx.doi.org/10.1016/j.ijcard.2015.08.109] [PMID: 26316329]

[2]

Wright AF, Rudan I, Hastie ND, Campbell H. A ‘complexity’ of urate transporters. Kidney Int 2010; 78(5): 446-52. [http://dx.doi.org/10.1038/ki.2010.206] [PMID: 20613716]

[3]

Jakše B, Jakše B, Pajek M, Pajek J. Uric Acid and Plant-Based Nutrition. Nutrients 2019; 11(8): 1736. [http://dx.doi.org/10.3390/nu11081736] [PMID: 31357560]

[4]

Williams AW, Wilson DM. Uric acid metabolism in humans. Semin Nephrol 1990; 10(1): 9-14. [PMID: 2404330]

[5]

Benn CL, Dua P, Gurrell R, et al. Physiology of Hyperuricemia and Urate-Lowering Treatments. Front Med (Lausanne) 2018; 5(160): 160. [http://dx.doi.org/10.3389/fmed.2018.00160] [PMID: 29904633]

[6]

Martillo MA, Nazzal L, Crittenden DB. The crystallization of monosodium urate. Curr Rheumatol Rep 2014; 16(2): 400. [http://dx.doi.org/10.1007/s11926-013-0400-9] [PMID: 24357445]

[7]

Grayson PC, Kim SY, LaValley M, Choi HK. Hyperuricemia and incident hypertension: A systematic review and meta-analysis. Arthritis Care Res (Hoboken) 2011; 63(1): 102-10. [http://dx.doi.org/10.1002/acr.20344] [PMID: 20824805]

[8]

Wang J, Qin T, Chen J, et al. Hyperuricemia and risk of incident hypertension: a systematic review and meta-analysis of observational studies. PLoS One 2014; 9(12): e114259. [http://dx.doi.org/10.1371/journal.pone.0114259] [PMID: 25437867]

[9]

Kim SY, Guevara JP, Kim KM, Choi HK, Heitjan DF, Albert DA. Hyperuricemia and coronary heart disease: A systematic review and meta-analysis. Arthritis Care Res (Hoboken) 2010; 62(2): NA. [http://dx.doi.org/10.1002/acr.20065] [PMID: 20191515]

[10]

Kim SY, Guevara JP, Kim KM, Choi HK, Heitjan DF, Albert DA. Hyperuricemia and risk of stroke: A systematic review and meta-analysis. Arthritis Rheum 2009; 61(7): 885-92. [http://dx.doi.org/10.1002/art.24612] [PMID: 19565556]

[11]

Li L, Yang C, Zhao Y, Zeng X, Liu F, Fu P. Is hyperuricemia an independent risk factor for new-onset chronic kidney disease?: a systematic review and meta-analysis based on observational cohort studies. BMC Nephrol 2014; 15(1): 122. [http://dx.doi.org/10.1186/1471-2369-15-122] [PMID: 25064611]

[12]

Kodama S, Saito K, Yachi Y, et al. Association between serum uric acid and development of type 2 diabetes. Diabetes Care 2009; 32(9): 1737-42. [http://dx.doi.org/10.2337/dc09-0288] [PMID: 19549729]

[13]

Lv Q, Meng XF, He FF, et al. High serum uric acid and increased risk of type 2 diabetes: a systemic review and meta-analysis of prospective cohort studies. PLoS One 2013; 8(2): e56864. [http://dx.doi.org/10.1371/journal.pone.0056864] [PMID: 23437258]

[14]

Dehghan A, van Hoek M, Sijbrands EJG, Hofman A, Witteman JCM. High serum uric acid as a novel risk factor for type 2 diabetes. Diabetes Care 2008; 31(2): 361-2. [http://dx.doi.org/10.2337/dc07-1276] [PMID: 17977935]

[15]

Bhole V, Choi JWJ, Woo Kim S, de Vera M, Choi H. Serum uric acid levels and the risk of type 2 diabetes: a prospective study. Am J Med 2010; 123(10): 957-61. [http://dx.doi.org/10.1016/j.amjmed.2010.03.027] [PMID: 20920699]

[16]

Wang R, Song Y, Yan Y, Ding Z. Elevated serum uric acid and risk of cardiovascular or all-cause mortality in people with suspected or definite coronary artery disease: A meta-analysis.

204 The Role of Nitric Oxide in Type 2 Diabetes

Bahadoran et al.

Atherosclerosis 2016; 254: 193-9. [http://dx.doi.org/10.1016/j.atherosclerosis.2016.10.006] [PMID: 27755985] [17]

Konta T, Ichikawa K, Kawasaki R, et al. Association between serum uric acid levels and mortality: a nationwide community-based cohort study. Sci Rep 2020; 10(1): 6066. [http://dx.doi.org/10.1038/s41598-020-63134-0] [PMID: 32269262]

[18]

Zavaroni I, Mazza S, Fantuzzi M, et al. Changes in insulin and lipid metabolism in males with asymptomatic hyperuricaemia. J Intern Med 1993; 234(1): 25-30. [http://dx.doi.org/10.1111/j.1365-2796.1993.tb00700.x] [PMID: 8326285]

[19]

Lu J, He Y, Cui L, Xing X, Liu Z, Li X, et al. Hyperuricemia Predisposes to the Onset of Diabetes via Promoting Pancreatic β-Cell Death in Uricase-Deficient Male Mice. 2020. [http://dx.doi.org/10.2337/db19-0704]

[20]

Ghasemi A. Uric acid-induced pancreatic β-cell dysfunction. BMC Endocr Disord 2021; 21(1): 24. [http://dx.doi.org/10.1186/s12902-021-00698-6] [PMID: 33593356]

[21]

Zhi L, Yuzhang Z, Tianliang H, Hisatome I, Yamamoto T, Jidong C. High Uric Acid Induces Insulin Resistance in Cardiomyocytes In Vitro and In Vivo. PLoS One 2016; 11(2): e0147737. [http://dx.doi.org/10.1371/journal.pone.0147737] [PMID: 26836389]

[22]

Yuan H, Hu Y, Zhu Y, et al. Metformin ameliorates high uric acid-induced insulin resistance in skeletal muscle cells. Mol Cell Endocrinol 2017; 443: 138-45. [http://dx.doi.org/10.1016/j.mce.2016.12.025] [PMID: 28042024]

[23]

Baldwin W, McRae S, Marek G, et al. Hyperuricemia as a mediator of the proinflammatory endocrine imbalance in the adipose tissue in a murine model of the metabolic syndrome. Diabetes 2011; 60(4): 1258-69. [http://dx.doi.org/10.2337/db10-0916] [PMID: 21346177]

[24]

Zhu Y, Hu Y, Huang T, et al. High uric acid directly inhibits insulin signalling and induces insulin resistance. Biochem Biophys Res Commun 2014; 447(4): 707-14. [http://dx.doi.org/10.1016/j.bbrc.2014.04.080] [PMID: 24769205]

[25]

Choi YJ, Yoon Y, Lee KY, et al. Uric acid induces endothelial dysfunction by vascular insulin resistance associated with the impairment of nitric oxide synthesis. FASEB J 2014; 28(7): 3197-204. [http://dx.doi.org/10.1096/fj.13-247148] [PMID: 24652948]

[26]

Adachi SI, Yoshizawa F, Yagasaki K. Hyperuricemia in type 2 diabetic model KK-A(y)/Ta mice: a potent animal model with positive correlation between insulin resistance and plasma high uric acid levels. 2017; 10(1): 577.

[27]

Martínez-Sánchez FD, Vargas-Abonce VP, Guerrero-Castillo AP, Santos-Villavicencio ML, EseizaAcevedo J, Meza-Arana CE, et al. Serum Uric Acid concentration is associated with insulin resistance and impaired insulin secretion in adults at risk for Type 2 Diabetes. Prim Care Diabetes 2020. [PMID: 33218916]

[28]

Ndrepepa G. Uric acid and cardiovascular disease. 2018. [http://dx.doi.org/10.1016/j.cca.2018.05.046]

[29]

El Ridi R, Tallima H. Physiological functions and pathogenic potential of uric acid: A review. J Adv Res 2017; 8(5): 487-93. [http://dx.doi.org/10.1016/j.jare.2017.03.003] [PMID: 28748115]

[30]

So A, Thorens B. Uric acid transport and disease. J Clin Invest 2010; 120(6): 1791-9. [http://dx.doi.org/10.1172/JCI42344] [PMID: 20516647]

[31]

Kratzer JT, Lanaspa MA, Murphy MN, et al. Evolutionary history and metabolic insights of ancient mammalian uricases. Proc Natl Acad Sci USA 2014; 111(10): 3763-8. [http://dx.doi.org/10.1073/pnas.1320393111] [PMID: 24550457]

[32]

Berry CE, Hare JM. Xanthine oxidoreductase and cardiovascular disease: molecular mechanisms and

Hyperuricemia, T2D and NO

The Role of Nitric Oxide in Type 2 Diabetes 205

pathophysiological implications. J Physiol 2004; 555(3): 589-606. [http://dx.doi.org/10.1113/jphysiol.2003.055913] [PMID: 14694147] [33]

Godber BLJ, Doel JJ, Sapkota GP, et al. Reduction of nitrite to nitric oxide catalyzed by xanthine oxidoreductase. J Biol Chem 2000; 275(11): 7757-63. [http://dx.doi.org/10.1074/jbc.275.11.7757] [PMID: 10713088]

[34]

Ichimori K, Fukahori M, Nakazawa H, Okamoto K, Nishino T. Inhibition of xanthine oxidase and xanthine dehydrogenase by nitric oxide. Nitric oxide converts reduced xanthine-oxidizing enzymes into the desulfo-type inactive form. J Biol Chem 1999; 274(12): 7763-8. [http://dx.doi.org/10.1074/jbc.274.12.7763] [PMID: 10075667]

[35]

Rouquette M, Page S, Bryant R, et al. Xanthine oxidoreductase is asymmetrically localised on the outer surface of human endothelial and epithelial cells in culture. FEBS Lett 1998; 426(3): 397-401. [http://dx.doi.org/10.1016/S0014-5793(98)00385-8] [PMID: 9600274]

[36]

Frederiks WM, Vreeling-Sindelárová H. Ultrastructural localization of xanthine oxidoreductase activity in isolated rat liver cells. Acta Histochem 2002; 104(1): 29-37. [http://dx.doi.org/10.1078/0065-1281-00629] [PMID: 11993848]

[37]

Beedham C. Xanthine Oxidoreductase and Aldehyde Oxidase. [http://dx.doi.org/10.1016/B978-0-08-046884-6.00410-3]

[38]

Pritsos CA. Cellular distribution, metabolism and regulation of the xanthine oxidoreductase enzyme system. Chem Biol Interact 2000; 129(1-2): 195-208. [http://dx.doi.org/10.1016/S0009-2797(00)00203-9] [PMID: 11154741]

[39]

Desideri G, Castaldo G, Lombardi A, et al. Is it time to revise the normal range of serum uric acid levels? Eur Rev Med Pharmacol Sci 2014; 18(9): 1295-306. [PMID: 24867507]

[40]

Valsaraj R, Singh AK, Gangopadhyay KK, et al. Management of asymptomatic hyperuricemia: Integrated Diabetes & Endocrine Academy (IDEA) consensus statement. Diabetes Metab Syndr 2020; 14(2): 93-100. [http://dx.doi.org/10.1016/j.dsx.2020.01.007] [PMID: 31991299]

[41]

Ichida K, Matsuo H, Takada T, et al. Decreased extra-renal urate excretion is a common cause of hyperuricemia. Nat Commun 2012; 3(1): 764. [http://dx.doi.org/10.1038/ncomms1756] [PMID: 22473008]

[42]

Oka Y, Tashiro H, Sirasaki R, et al. Hyperuricemia in hematologic malignancies is caused by an insufficient urinary excretion. Nucleosides Nucleotides Nucleic Acids 2014; 33(4-6): 434-8. [http://dx.doi.org/10.1080/15257770.2013.872274] [PMID: 24940701]

[43]

Scott JT, Holloway VP, Glass HI, Arnot RN. Studies of uric acid pool size and turnover rate. Ann Rheum Dis 1969; 28(4): 366-73. [http://dx.doi.org/10.1136/ard.28.4.366] [PMID: 5794063]

[44]

Emmerson BT. The management of gout. N Engl J Med 1996; 334(7): 445-51. [http://dx.doi.org/10.1056/NEJM199602153340707] [PMID: 8552148]

[45]

de Oliveira EP, Burini RC. High plasma uric acid concentration: causes and consequences. Diabetol Metab Syndr 2012; 4(1): 12. [http://dx.doi.org/10.1186/1758-5996-4-12] [PMID: 22475652]

[46]

Nishimura T, Shimizu T, Mineo I, et al. Influence of daily drinking habits on ethanol-induced hyperuricemia. Metabolism 1994; 43(6): 745-8. [http://dx.doi.org/10.1016/0026-0495(94)90125-2] [PMID: 8201965]

[47]

Johnson RJ, Perez-Pozo SE, Sautin YY, et al. Hypothesis: could excessive fructose intake and uric acid cause type 2 diabetes? Endocr Rev 2009; 30(1): 96-116. [http://dx.doi.org/10.1210/er.2008-0033] [PMID: 19151107]

206 The Role of Nitric Oxide in Type 2 Diabetes

Bahadoran et al.

[48]

Kaneko C, Ogura J, Sasaki S, et al. Fructose suppresses uric acid excretion to the intestinal lumen as a result of the induction of oxidative stress by NADPH oxidase activation. Biochim Biophys Acta, Gen Subj 2017; 1861(3): 559-66. [http://dx.doi.org/10.1016/j.bbagen.2016.11.042] [PMID: 27913188]

[49]

Nakagawa T, Hu H, Zharikov S, et al. A causal role for uric acid in fructose-induced metabolic syndrome. Am J Physiol Renal Physiol 2006; 290(3): F625-31. [http://dx.doi.org/10.1152/ajprenal.00140.2005] [PMID: 16234313]

[50]

Sorensen LB. Role of the intestinal tract in the elimination of uric acid. Arthritis Rheum 1965; 8(4): 694-706. [http://dx.doi.org/10.1002/art.1780080429] [PMID: 5859543]

[51]

Bobulescu IA, Moe OW. Renal transport of uric acid: evolving concepts and uncertainties. Adv Chronic Kidney Dis 2012; 19(6): 358-71. [http://dx.doi.org/10.1053/j.ackd.2012.07.009] [PMID: 23089270]

[52]

Mandal AK, Mount DB. The molecular physiology of uric acid homeostasis. Annu Rev Physiol 2015; 77(1): 323-45. [http://dx.doi.org/10.1146/annurev-physiol-021113-170343] [PMID: 25422986]

[53]

Löffler W, Gröbner W, Medina R, Zöllner N. Influence of dietary purines on pool size, turnover, and excretion of uric acid during balance conditions. Res Exp Med (Berl) 1982; 181(2): 113-23. [http://dx.doi.org/10.1007/BF01852188] [PMID: 6294765]

[54]

Becker BF. Towards the physiological function of uric acid. Free Radic Biol Med 1993; 14(6): 615-31. [http://dx.doi.org/10.1016/0891-5849(93)90143-I] [PMID: 8325534]

[55]

Lai JH, Luo SF, Hung LF, et al. Physiological concentrations of soluble uric acid are chondroprotective and anti-inflammatory. Sci Rep 2017; 7(1): 2359. [http://dx.doi.org/10.1038/s41598-017-02640-0] [PMID: 28539647]

[56]

Ames BN, Cathcart R, Schwiers E, Hochstein P. Uric acid provides an antioxidant defense in humans against oxidant- and radical-caused aging and cancer: a hypothesis. Proc Natl Acad Sci USA 1981; 78(11): 6858-62. [http://dx.doi.org/10.1073/pnas.78.11.6858] [PMID: 6947260]

[57]

Gersch C, Palii SP, Kim KM, Angerhofer A, Johnson RJ, Henderson GN. Inactivation of nitric oxide by uric acid. Nucleosides Nucleotides Nucleic Acids 2008; 27(8): 967-78. [http://dx.doi.org/10.1080/15257770802257952] [PMID: 18696365]

[58]

Suzuki T. Nitrosation of uric acid induced by nitric oxide under aerobic conditions. Nitric Oxide 2007; 16(2): 266-73. [http://dx.doi.org/10.1016/j.niox.2006.10.008] [PMID: 17166753]

[59]

Broniowska KA, Diers AR, Hogg N. S-Nitrosoglutathione. Biochim Biophys Acta, Gen Subj 2013; 1830(5): 3173-81. [http://dx.doi.org/10.1016/j.bbagen.2013.02.004] [PMID: 23416062]

[60]

Peden DB, Hohman R, Brown ME, et al. Uric acid is a major antioxidant in human nasal airway secretions. Proc Natl Acad Sci USA 1990; 87(19): 7638-42. [http://dx.doi.org/10.1073/pnas.87.19.7638] [PMID: 2217195]

[61]

Cross CE, Motchnik PA, Bruener BA, et al. Oxidative damage to plasma constituents by ozone. FEBS Lett 1992; 298(2-3): 269-72. [http://dx.doi.org/10.1016/0014-5793(92)80074-Q] [PMID: 1544461]

[62]

Khanna D, Fitzgerald JD, Khanna PP, et al. 2012 American College of Rheumatology guidelines for management of gout. Part 1: Systematic nonpharmacologic and pharmacologic therapeutic approaches to hyperuricemia. Arthritis Care Res (Hoboken) 2012; 64(10): 1431-46. [http://dx.doi.org/10.1002/acr.21772] [PMID: 23024028]

Hyperuricemia, T2D and NO

The Role of Nitric Oxide in Type 2 Diabetes 207

[63]

Bos MJ, Koudstaal PJ, Hofman A, Witteman JCM, Breteler MMB. Uric acid is a risk factor for myocardial infarction and stroke: the Rotterdam study. Stroke 2006; 37(6): 1503-7. [http://dx.doi.org/10.1161/01.STR.0000221716.55088.d4] [PMID: 16675740]

[64]

Fang J, Alderman MH. Serum uric acid and cardiovascular mortality the NHANES I epidemiologic follow-up study, 1971-1992. National Health and Nutrition Examination Survey. JAMA 2000; 283(18): 2404-10. [http://dx.doi.org/10.1001/jama.283.18.2404] [PMID: 10815083]

[65]

Hao L, Zhou Y, Xu H. A study of the correlation between vitamin D uric acid levels and senile acute cerebral infarction. Int J Clin Exp Med 2019; 12(7): 9343-50.

[66]

Chen PH, Chen YW, Liu WJ, Hsu SW, Chen CH, Lee CL. Approximate Mortality Risks between Hyperuricemia and Diabetes in the United States. J Clin Med 2019; 8(12): 2127. [http://dx.doi.org/10.3390/jcm8122127] [PMID: 31816820]

[67]

Zhao L, Cao L, Zhao TY, et al. Cardiovascular events in hyperuricemia population and a cardiovascular benefit-risk assessment of urate-lowering therapies: a systematic review and metaanalysis. Chin Med J (Engl) 2020; 133(8): 982-93. [http://dx.doi.org/10.1097/CM9.0000000000000682] [PMID: 32106120]

[68]

Zuo T, Liu X, Jiang L, Mao S, Yin X, Guo L. Hyperuricemia and coronary heart disease mortality: a meta-analysis of prospective cohort studies. BMC Cardiovasc Disord 2016; 16(1): 207. [http://dx.doi.org/10.1186/s12872-016-0379-z] [PMID: 27793095]

[69]

Feng X, Huang J, Peng Y, Xu Y. Association between decreased thyroid stimulating hormone and hyperuricemia in type 2 diabetic patients with early-stage diabetic kidney disease. BMC Endocr Disord 2021; 21(1): 1-8. [http://dx.doi.org/10.1186/s12902-020-00672-8] [PMID: 33407357]

[70]

Hu J, Xu W, Yang H, Mu L. Uric acid participating in female reproductive disorders: a review. Reprod Biol Endocrinol 2021; 19(1): 65. [http://dx.doi.org/10.1186/s12958-021-00748-7] [PMID: 33906696]

[71]

Lou Y, Qin P, Wang C, Ma J, Peng X, Xu S, et al. Sex-Specific Association of Serum Uric Acid Level and Change in Hyperuricemia Status with Risk of Type 2 Diabetes Mellitus: A Large Cohort Study in China. Journal of Diabetes Research. 2020 2020.

[72]

Yamada T, Fukatsu M, Suzuki S, Wada T, Joh T. Elevated serum uric acid predicts impaired fasting glucose and type 2 diabetes only among Japanese women undergoing health checkups. Diabetes Metab 2011; 37(3): 252-8. [http://dx.doi.org/10.1016/j.diabet.2010.10.009] [PMID: 21377910]

[73]

Binh TQ, Tran Phuong P, Thanh Chung N, et al. First Report on Association of Hyperuricemia with Type 2 Diabetes in a Vietnamese Population. Int J Endocrinol 2019; 2019: 1-7. [http://dx.doi.org/10.1155/2019/5275071] [PMID: 31565055]

[74]

Kuwabara M, Kuwabara R, Hisatome I, et al. “Metabolically Healthy” Obesity and Hyperuricemia Increase Risk for Hypertension and Diabetes: 5-year Japanese Cohort Study. Obesity (Silver Spring) 2017; 25(11): 1997-2008. [http://dx.doi.org/10.1002/oby.22000] [PMID: 28922565]

[75]

Liu J, Tao L, Zhao Z, Mu Y, Zou D, Zhang J, et al. Two-year changes in hyperuricemia and risk of diabetes: a five-year prospective cohort study. 2018. [http://dx.doi.org/10.1155/2018/6905720]

[76]

Han T, Meng X, Shan R, Zi T, Li Y, Ma H, et al. Temporal relationship between hyperuricemia and obesity, and its association with future risk of type 2 diabetes.2018. [http://dx.doi.org/10.1038/s41366-018-0074-5]

[77]

Nakanishi N, Okamoto M, Yoshida H, Matsuo Y, Suzuki K, Tatara K. Serum uric acid and risk for development of hypertension and impaired fasting glucose or Type II diabetes in Japanese male office

208 The Role of Nitric Oxide in Type 2 Diabetes

Bahadoran et al.

workers. Eur J Epidemiol 2002; 18(6): 523-30. [http://dx.doi.org/10.1023/A:1024600905574] [PMID: 12908717] [78]

Sunagawa S, Shirakura T, Hokama N, et al. Activity of xanthine oxidase in plasma correlates with indices of insulin resistance and liver dysfunction in patients with type 2 diabetes mellitus and metabolic syndrome: A pilot exploratory study. J Diabetes Investig 2019; 10(1): 94-103. [http://dx.doi.org/10.1111/jdi.12870] [PMID: 29862667]

[79]

Takir M, Kostek O, Ozkok A, Elcioglu OC, Bakan A, Erek A, et al. Lowering Uric Acid With Allopurinol Improves Insulin Resistance and Systemic Inflammation in Asymptomatic Hyperuricemia. 2015. [http://dx.doi.org/10.1097/JIM.0000000000000242]

[80]

Ogino K, Kato M, Furuse Y, et al. Uric acid-lowering treatment with benzbromarone in patients with heart failure: a double-blind placebo-controlled crossover preliminary study. Circ Heart Fail 2010; 3(1): 73-81. [http://dx.doi.org/10.1161/CIRCHEARTFAILURE.109.868604] [PMID: 19933411]

[81]

Dogan A, Yarlioglues M, Kaya MG, et al. Effect of long-term and high-dose allopurinol therapy on endothelial function in normotensive diabetic patients. Blood Press 2011; 20(3): 182-7. [http://dx.doi.org/10.3109/08037051.2010.538977] [PMID: 21133824]

[82]

Nishikawa T, Nagata N, Shimakami T, et al. Xanthine oxidase inhibition attenuates insulin resistance and diet-induced steatohepatitis in mice. Sci Rep 2020; 10(1): 815. [http://dx.doi.org/10.1038/s41598-020-57784-3] [PMID: 31965018]

[83]

Cicerchi C, Li N, Kratzer J, et al. Uric acid-dependent inhibition of AMP kinase induces hepatic glucose production in diabetes and starvation: evolutionary implications of the uricase loss in hominids. FASEB J 2014; 28(8): 3339-50. [http://dx.doi.org/10.1096/fj.13-243634] [PMID: 24755741]

[84]

Roncal-Jimenez CA, Lanaspa MA, Rivard CJ, et al. Sucrose induces fatty liver and pancreatic inflammation in male breeder rats independent of excess energy intake. Metabolism 2011; 60(9): 1259-70. [http://dx.doi.org/10.1016/j.metabol.2011.01.008] [PMID: 21489572]

[85]

Zhou Y, Zhao M, Pu Z, Xu G, Li X. Relationship between oxidative stress and inflammation in hyperuricemia: Analysis based on asymptomatic young patients with primary hyperuricemia. Medicine (Baltimore). 2018;97(49):e13108-e. 2018; 97(49): e13108-.

[86]

Tang L, Xu Y, Wei Y, He X. Uric acid induces the expression of TNF-α via the ROS-MAPK-NF-κB signaling pathway in rat vascular smooth muscle cells. Mol Med Rep 2017; 16(5): 6928-33. [http://dx.doi.org/10.3892/mmr.2017.7405] [PMID: 28901421]

[87]

Kanellis J, Watanabe S, Li JH, Kang DH, Li P, Nakagawa T, et al. Uric acid stimulates monocyte chemoattractant protein-1 production in vascular smooth muscle cells via mitogen-activated protein kinase and cyclooxygenase-2. 2003. [http://dx.doi.org/10.1161/01.HYP.0000072820.07472.3B]

[88]

Sautin YY, Nakagawa T, Zharikov S, Johnson RJ. Adverse effects of the classic antioxidant uric acid in adipocytes: NADPH oxidase-mediated oxidative/nitrosative stress. Am J Physiol Cell Physiol 2007; 293(2): C584-96. [http://dx.doi.org/10.1152/ajpcell.00600.2006] [PMID: 17428837]

[89]

Spiga R, Marini MA, Mancuso E, et al. Uric Acid Is Associated With Inflammatory Biomarkers and Induces Inflammation via Activating the NF-κB Signaling Pathway in HepG2 Cells. Arterioscler Thromb Vasc Biol 2017; 37(6): 1241-9. [http://dx.doi.org/10.1161/ATVBAHA.117.309128] [PMID: 28408375]

[90]

Bahadoran Z, Mirmiran P, Ghasemi A. Role of Nitric Oxide in Insulin Secretion and Glucose Metabolism. Trends Endocrinol Metab 2020; 31(2): 118-30. [http://dx.doi.org/10.1016/j.tem.2019.10.001] [PMID: 31690508]

Hyperuricemia, T2D and NO

The Role of Nitric Oxide in Type 2 Diabetes 209

[91]

Kanabrocki EL, Third JL, Ryan MD, et al. Circadian relationship of serum uric acid and nitric oxide. JAMA 2000; 283(17): 2240-1. [http://dx.doi.org/10.1001/jama.283.17.2235] [PMID: 10807381]

[92]

Papežíková I, Pekarová M, Kolářová H, et al. Uric acid modulates vascular endothelial function through the down regulation of nitric oxide production. Free Radic Res 2013; 47(2): 82-8. [http://dx.doi.org/10.3109/10715762.2012.747677] [PMID: 23136942]

[93]

Schwartz IF, Grupper A, Chernichovski T, et al. Hyperuricemia attenuates aortic nitric oxide generation, through inhibition of arginine transport, in rats. J Vasc Res 2011; 48(3): 252-60. [http://dx.doi.org/10.1159/000320356] [PMID: 21099230]

[94]

Park J-H, Jin YM, Hwang S, Cho D-H, Kang D-H, Jo I. Uric acid attenuates nitric oxide production by decreasing the interaction between endothelial nitric oxide synthase and calmodulin in human umbilical vein endothelial cells: a mechanism for uric acid-induced cardiovascular disease development. 2013. [http://dx.doi.org/10.1016/j.niox.2013.04.003]

[95]

Cai W, Duan XM, Liu Y, et al. Uric Acid Induces Endothelial Dysfunction by Activating the HMGB1/RAGE Signaling Pathway. BioMed Res Int 2017; 2017: 1-11. [http://dx.doi.org/10.1155/2017/4391920] [PMID: 28116308]

[96]

Hong Q, Qi K, Feng Z, et al. Hyperuricemia induces endothelial dysfunction via mitochondrial Na+/Ca2+ exchanger-mediated mitochondrial calcium overload. Cell Calcium 2012; 51(5): 402-10. [http://dx.doi.org/10.1016/j.ceca.2012.01.003] [PMID: 22361139]

[97]

Uslu S, Ozcelik E, Kebapci N, Temel HE, Demirci F, Ergun B, et al. Effects of serum uric acid levels on the arginase pathway in women with metabolic syndrome. 2016. [http://dx.doi.org/10.1007/s11845-015-1347-9]

[98]

Bahadoran Z, Mirmiran P, Kashfi K, Ghasemi A. Hyperuricemia-induced endothelial insulin resistance: the nitric oxide connection. Pflugers Arch 2021; 1-16. [PMID: 34313822]

[99]

Tassone EJ, Cimellaro A, Perticone M, et al. Uric Acid Impairs Insulin Signaling by Promoting Enpp1 Binding to Insulin Receptor in Human Umbilical Vein Endothelial Cells. Front Endocrinol (Lausanne) 2018; 9: 98. [http://dx.doi.org/10.3389/fendo.2018.00098] [PMID: 29619007]

[100] Jia L, Xing J, Ding Y, et al. Hyperuricemia causes pancreatic β-cell death and dysfunction through NF-κB signaling pathway. PLoS One 2013; 8(10): e78284. [http://dx.doi.org/10.1371/journal.pone.0078284] [PMID: 24205181]

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CHAPTER 10

Therapeutic Management of Type 2 Diabetes: The Nitric Oxide Axis Tara Ranjbar1, Jennifer L. O’Connor1,2 and Khosrow Kashfi1,3,* Department of Molecular, Cellular, and Biomedical Sciences, Sophie Davis School of Biomedical Education, City University of New York School of Medicine, New York, NY, USA 2 Department of Chemistry and Physics, State University of New York at Old Westbury, Old Westbury, NY, USA 3 Graduate Program in Biology, City University of New York Graduate Center, New York, NY, USA 1

Abstract: According to the World Health Organization (WHO), the prevalence of obesity across the globe has nearly tripled since 1975, with 39 million children under the age of 5 being overweight or obese in 2020. Obesity is the most common risk factor for developing type 2diabetes (T2D), which may lead to elevated serum triglycerides, hypertension, and insulin resistance. In the pathogenesis of T2D, there is a reduction in nitric oxide (NO) bioavailability. Restoration of NO levels has been associated with many favorable metabolic effects in T2D. Drugs that potentiate NO levels may have a role in improving T2D-associated adverse effects. Current medications approved for use in the management of T2D include biguanides, thiazolidinediones, sulfonylureas, meglitinides, dipeptidyl peptidase-4 (DPP-4) inhibitors, glucagon-like peptide-1 (GLP1) receptor agonists, alpha-glucosidase inhibitors, and sodium-glucose co-transporter 2 (SGLT2) inhibitors. These drugs mitigate the many adverse effects associated with T2D. This chapter discusses these classes of drugs, examines their mechanism of action, and presents evidence that these drugs directly or indirectly modulate NO levels.

Keywords: Alpha-glucosidase inhibitors, Biguanides, Dipeptidyl peptidase-4 inhibitors, Glucagon-like peptide-1, Glucagon-like peptide-1 receptor agonists, Meglitinides, Metformin, Nitric oxide, Sodium-glucose co-transporter, Sodiumglucose co-transporter inhibitors, Sulfonylureas, Thiazolidinediones, Type 2 diabetes.

Corresponding author Khosrow Kashfi: Department of Molecular, Cellular, and Biomedical Sciences, Sophie Davis School of Biomedical Education, City University of New York School of Medicine, New York, NY, USA, Graduate Program in Biology, City University of New York Graduate Center, New York, NY, USA; [email protected].

*

Asghar Ghasemi, Khosrow Kashfi, Zahra Bahadoran (Eds.) All rights reserved-© 2022 Bentham Science Publishers

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INTRODUCTION In 1825, Jean Anthelme Brillat-Savarin wrote, in Physiologie du Gout, ou Meditations de Gastronomie Transcendante: “Dis-moi ce que tu manges, je te dirai ce que tu es.” (Tell me what you eat and I will tell you what you are) [1]. The German philosopher and anthropologist Ludwig Andreas von Feuerbach, in an essay titled Concerning Spiritualism and Materialism, wrote: “Der Mensch ist, was er ißt” (man is what he eats) [2, 3]. The food you eat is a reflecting image of yourself. Thus, maintaining a well-balanced and healthy diet is essential for good health. According to the World Health Organization (WHO), the prevalence of obesity across the globe has nearly tripled since 1975, with 39 million children under the age of 5 being overweight or obese in 2020 [4]. In the United States, approximately one-third of the adult population is obese, and an additional onethird is overweight [5]. Obesity is the fastest-growing lethal disease in Western and developing countries. People do not die from obesity itself but from its complications, which shorten their lifespan [6, 7]. Type 2 diabetes (T2D), referred to as adult-onset or non-insulin-dependent diabetes, accounts for over 90-95% of all diabetes. It is a complex chronic metabolic disorder characterized by alterations in lipid metabolism, insulin resistance, hyperglycemia, and pancreatic β-cell dysfunction [8]. Since in T2D, patients are unable to store and utilize their glucose within the muscles, adipose tissues, and liver [9], these patients are in a constant hyperglycemic state [10]. Risk factors associated with the development of T2D include obesity, especially in the intra-abdominal region, sedentary lifestyle, and family history [11]. For this reason, T2D patients are often overweight, but weight loss and exercise can improve their blood glucose levels. Many complications are associated with T2D, including cardiovascular disease, kidney disease, peripheral neuropathy, and cataracts [12]. One mechanism by which high glucose levels can affect the heart is its non-enzymatic glycation and cross-link, which produces “advanced glycosylation end products” (AGEs) [13]. The AGEs trap circulating low-density lipoprotein cholesterol (LDL-C) within the medium and large-sized vessels leading to atherosclerosis [14]. Depending on the location of this atherosclerosis, it can lead to coronary artery disease, stroke, and peripheral vascular disease. When the AGEs are within the smaller sizes arteries and arterioles, this may cause diabetic kidney disease and renal failure [15]. For these reasons, type 2 diabetic patients need to maintain appropriate blood glucose levels to reduce the risks of these complications. In the pathogenesis of T2D, there is a reduction in nitric oxide (NO) bioavailability [16]. Restoration of NO levels has been associated with many

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favorable metabolic effects in T2D [16]. NO is produced in all tissues by NO synthase (NOS)-dependent and independent pathways [16]. There are three isoforms of NOS, neuronal (nNOS/NOS-1), inducible (iNOS/NOS-2), and endothelial (eNOS/NOS-3), with all three being expressed in the pancreatic βcells [16]. Drugs that potentiate NO levels may have a role in improving T2Dassociated adverse effects. Current drugs approved for use in the management of T2D include biguanides, thiazolidinediones, sulfonylureas, meglitinides, dipeptidyl peptidase-4 (DPP-4) inhibitors, glucagon-like peptide-1 (GLP-1) receptor agonists, alpha-glucosidase inhibitors, and sodium-glucose co-transporter 2 (SGLT2) inhibitors [17, 18]. These drugs mitigate the many adverse effects associated with T2D. This chapter discusses these classes of drugs, examines their mechanism of action, and presents evidence that these drugs directly or indirectly modulate NO metabolism. BIGUANIDES General Mechanism of Action Although the term biguanides refer to a whole class of oral T2D drugs, metformin (N, N-Dimemethylbiguanide) [widely known as glucophage] is the only approved biguanide derivative currently available for the treatment of hyperglycemia. It is on the World Health Organization's List of Essential Medicines [19]. Metformin is a first-line T2D drug used to reduce blood glucose levels [20] and body weight [21]. Generally, it is prescribed as monotherapy for treating T2D, but it can also be used in combination with other medications, such as pioglitazone and vildagliptin, which are thiazolidinediones and DPP-4 inhibitors, respectively [22]. The functional purpose of metformin is to lower both the basal and postprandial plasma glucose levels [23]. It decreases hepatic glucose production, reduces intestinal glucose absorption, and improves insulin sensitivity by increasing peripheral glucose uptake/utilization by the skeletal muscles and adipocytes [22, 23]. Metformin has also been shown to be an effective drug to reduce weight in insulin-sensitive and insulin-resistant overweight and obese patients [24]. The hepatocytes take up metformin through the organic cation transporter-1 (OCT-1) [25]. Its mechanism of action involves reducing hepatic glucose production by inhibiting gluconeogenesis while maintaining insulin uptake by the periphery [26]. At the molecular level, metformin has been found to inhibit the hepatic mitochondrial respiratory chain at complex I [27], which ultimately leads to the activation of AMP-activated protein kinase (AMPK) [28]. AMPK is a heterotrimeric enzyme involved in metabolic regulation [29] and is composed of a catalytic subunit and two regulatory subunits [30]. The catalytic subunit of this

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enzyme comes in two isoforms: AMPK alpha1 and AMPK alpha2. The AMPK alpha 2 subunit is found in the heart, liver, and skeletal muscle [31]. Metformin activates AMPK phosphorylation at Thr 172 and through an allosteric AMP site [32]. The activation of AMPK decreases glucagon-induced 3',5'-cyclic adenosine monophosphate (cAMP) levels [33], resulting in an augmentation in the host’s insulin sensitivity capabilities [34]. Although activation of AMPK has been at the forefront of metformin’s mechanism of action, this notion is still somewhat controversial. AMPK activation occurs when there is an increase in the ratio of cytoplasmic AMP:ATP or ADP:ATP, such as when the cell recognizes oxidative stress, metabolic stress, nutrient deprivation, or hypoxia [35]. The increase in the AMP:ATP ratio was also found to inhibit fructose-1, 6-bisphosphatase, which is the rate-limiting step in gluconeogenesis, thus reducing hepatic glucose production [36]. Since gluconeogenesis is a highly energy-consuming process, it is essential to reduce ATP production when inhibiting gluconeogenesis from maintaining the balance between supply and demand [37]. Since metformin is positively charged, it accumulates within the mitochondria and inhibits complex I of the oxidative phosphorylation pathway resulting in decreased ATP production [27, 37, 38]. Apart from reducing cellular gluconeogenesis, metformin suppresses fatty acid synthesis and upregulates skeletal muscles’ glucose uptake through an AMPK-mediated mechanism [39]. AMPK activation inhibits acetyl-CoA carboxylase-2, the rate-limiting enzyme in fatty acid synthesis [40]; thus, acetyl-CoA cannot be converted into malonyl-CoA, which is a potent inhibitor of carnitine palmitoyltransferas-1, the rate-limiting enzyme in fatty acid oxidation [40, 41]. Since malonyl-CoA levels are reduced, lipid synthesis diminishes while fatty acid oxidation increases [32]. Metformin upregulates AMPK alpha 2, the main isoform of AMPK found in skeletal muscles, allowing glucose uptake into the muscles [42]. Metformin is contraindicated in patients with impaired renal function due to potential lactic acid accumulation [42]. Metformin and Its Nitric Oxide Connection In obese and T2D patients, expression of tumor necrosis factor-alpha (TNF-a) is increased [43], resulting in lower eNOS expression and hence reduced levels of NO [44], especially within adipocytes and skeletal muscles [45]. To compensate for the lower eNOS levels, there are an upregulation of iNOS that can be seen in the pancreatic β-cells [46], skeletal muscles, hepatocytes [47], and adipocytes [48]. Increased iNOS levels have been associated with insulin resistance and worsening pathophysiology of T2D [49]. Metformin contributes to weight loss through its anorexic effects by inhibiting iNOS, which is upregulated in insulin

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resistance [50, 51]. This occurs because metformin is structurally similar to aminoguanidine (AG), an inhibitor of iNOS [52]. Production of NO by the endothelial cells signifies a healthy endothelium, which is essential for maintaining vascular stability, coagulation and fibrinolysis, and blood pressure [53, 54]. T2D patients are at an increased risk of death from cardiovascular disease, myocardial infarctions, and stroke [55]. Metformin increases NO levels resulting in vascular endothelial vasodilatory effects; this reduces the risk for detrimental cardiovascular events [56]. By restoring eNOS levels, metformin also reduces peroxynitrite (ONOO-) formation, a potent cytotoxic vasoconstrictor, thus shifting the balance towards vasodilation [57]. The positive influence of metformin on the NO/L-arginine pathway prevents further generation of ONOO- and preserves bioavailable NO concentrations within a host [57]. This promotes vasorelaxation and vasodilation and ultimately contributes to better health outcomes. THIAZOLIDINEDIONES General Mechanism of Action Thiazolidinediones (TZDs) are a class of oral antidiabetic medications that decrease hepatic glucose production, increase hepatic glucose uptake, increase tissue sensitivity to insulin (which in turn increases glucose uptake), and reduce lipidemia [58]. All drugs ending with the suffix “zone” are members of this class. Currently, pioglitazone and rosiglitazone are 2 members of this class that are FDA (Food and Drug Administration) approved for either monotherapy or combination therapy with other drugs like metformin [59]. TZDs target the nuclear transcription factor peroxisome proliferator-activated receptor-gamma (PPAR-γ) in the liver, muscle, and adipose tissue [60, 61]. PPAR-γ heterodimerizes with the retinoid X receptor-α and activates the transcription of target genes by binding the PPAR response element (PPRE) [62]. These include genes that are involved in energy homeostasis, glucose metabolism, lipoprotein lipase, adipocyte fatty acidbinding protein, malic enzyme, glucokinase, fatty acyl-CoA synthase, and the glucose transporter-4 (GLUT4), which is involved in insulin-sensitive glucose uptake in skeletal muscle and adipocytes [61, 63 - 65]. TZDs also improve pancreatic β-cells function by targeting free fatty acids on the islet cells [66] and reducing circulating FFAs by about 20% [67]. TZDs have antilipidemic effects; they decrease plasma fatty acid levels, decrease triglycerides, and increase highdensity lipoprotein cholesterol (HDL-C) [68]. TZDs increase the secretion of adiponectin, which can promote fat oxidation and increase insulin sensitivity [69]. In summary, TZDs increase insulin sensitivity through the intracellular metabolic

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pathways to enhance insulin’s properties [70]. Since TZDs work at the gene level, it takes about 6 weeks to 6 months to see maximum efficacy [71]. Thiazolidinediones and Their Nitric Oxide Connection Aside from increasing insulin sensitivity and modulating glucose and lipid metabolism, TZDs also improve endothelial function [72]. PPAR-γ is expressed on both vascular smooth muscle cells and endothelial cells, which is why TZDs can impact NO release [73]. Treatment of umbilical vein endothelial cells (HUVECs) and human aortic endothelial cells with PPAR-γ ligands (15d-PGJ2 or ciglitazone) increased eNOS activity and NO levels [73]. Angiotensin II (Ang II) induces endothelial dysfunction by increasing nitrosative stress [74] and downregulating PPARγ [75]. Pioglitazone significantly improved NO bioavailability and reduced ONOO− formation in an Ang II–infused in vivo model. It also upregulated PPARγ expression in vascular tissue [75]. Also, treating Zucker diabetic fatty (ZDF) rats with rosiglitazone improved endothelial function [76]. In T2D patients, rosiglitazone increased NO levels even after L-NMMA (pan NOS inhibitor) administration [77]. This resulted in restored endothelial function suggesting effects that were mediated through eNOS. Aside from increasing NO bioavailability, rosiglitazone provided beneficial anti-T2D effects by reducing microalbuminuria levels and slowing down the progression of diabetic kidney damage [78]. Rosiglitazone has been linked with increased risks for cardiovascular events due to fluid retention, worsening peripheral edema, and precipitating heart failure. For this reason, T2D patients who have co-existing cardiac issues are not advised to take this drug [79]. SULFONYLUREAS General Mechanism of Action Sulfonylureas are a class of anti-hyperglycemic drugs used in the treatment of T2D. Generally, they are divided into first and second generations, whose primary mechanism of action is to increase insulin release by stimulating pancreatic βcells [80]. They target the ATP-sensitive potassium (KATP) channel, which controls β-cell membrane potential. Inhibition of KATP channels by sulfonylureas induces membrane depolarization, which in turn activates voltage-gated Ca2+ ion channels resulting in Ca2+ influx into the β-cells. The Ca2+ influx is a key triggering factor for insulin granule exocytosis [81, 82]. Sulfonylureas have several extra-pancreatic effects that may augment their hypoglycemic effects. They increase tissue uptake of glucose by stimulating

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glycolysis in the skeletal muscle [83], liver [84], and heart [85]; they also decrease the hepatic output of glucose by inhibiting gluconeogenesis [84]. A much less appreciated effect of sulfonylureas is their inhibition of fatty acid oxidation. Glyburide and tolbutamide inhibited rat liver, heart, and skeletal muscle carnitine palmitoyltransferase-1, the key regulatory enzyme in the fatty acid oxidation pathway [86]. The KATP channel is a hetero-octameric complex of two different types of protein subunits: an inwardly rectifying K+ channel, Kir6.x, and a sulfonylurea receptor, SUR [82, 87, 88]. There are multiple isoforms for the Kir6.x and SUR proteins; however, in most tissues, it is the Kir6.2 isoform that forms a tetramer and acts as a channel pore, allowing K+ into the cell [89]. Kir6.2 has been found to interact with various SUR subunits, like SUR1, located in the pancreas and brain [90]. KATP channel inhibitors fall into two categories: those interacting with Kir6.2 and those interacting with SUR. Sulfonylureas fall into the latter category and work by binding to its SUR receptor at a high affinity [91], resulting in KATP channel closure. Sulfonylureas can also interact with kir6.2 but do so at a lower affinity [82]. Sulfonylureas and thiazolidinediones have opposite effects on β-cell functionality; β-cell stress is decreased by TZDs but increased with sulfonylureas [92]. TZDs are insulin sensitizers meanwhile sulfonylureas are insulin secretagogues. Both drugs improve glycemic control whether prescribed alone or in combination. Older sulfonylureas have been linked with adverse cardiovascular events such as left ventricular dysfunction and myocardial infarction [93]; newer sulfonylureas have fewer risks [94]. Sulfonylurea and Their Nitric Oxide Connection Treatment of human endothelial cells with glimepiride increased eNOS activity by its phosphorylation at Ser-1177, resulting in enhanced NO levels [95]. The concentration of glimepiride necessary to achieve this induction was within its pharmacologically active range. Glimepiride phosphorylates and activates the insulin receptor substrate-1 (IRS-1) [96]. IRS-1 is an upstream regulator of phosphatidylinositol 3-kinase (PI3-kinase) in adipocytes, which is involved in translocating GLUT-4 to muscle and adipocytes for insulin-dependent glucose uptake [97]. Treatment of human coronary artery endothelial cells with glimepiride induced NO production through the PI3-kinase pathway, which is essential for atheroprotection [96]. Thus, glimepiride inhibits atheromatous plaques formation caused by high cholesterol

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levels [98]. T2D rats have lower serum NO concentrations; treatment with glyburide restored serum levels of NO production to normal values [99]. MEGLITINIDES General Mechanism of Action Meglitinides are considered to be “non-sulfonylurea” secretagogues. They are similar to sulfonylureas, but reduce blood glucose levels much faster, have shorter half-lives, and are not sulfa drugs [100]. There are currently two meglitinides available in the US for the treatment of T2D: repaglinide and nateglinide. Both drugs have been approved for monotherapy or in combination with other T2D drugs other than sulfonylureas [101]. These drugs have a similar mechanism of action to sulfonylureas; they increase insulin secretion by the pancreatic β-cells but in a shorter duration of time [102]. Since this class of drugs has a shorter halflife than sulfonylureas, meglitinides are less difficult to control and, therefore, less likely to cause excessive hypoglycemia, increased weight gain, and elevated insulin levels [102]. Repaglinide inhibits KATP channels resulting in membrane depolarization and calcium influx. This calcium influx stimulates the release of insulin-containing granules, thus increasing plasma insulin levels [88]. Repaglinide binds to SUR1 of the β-cells; however, this binding site is different from that of glibenclamide and nateglinide [103]. Compared to repaglinide, nateglinide works much faster, has a higher affinity for the SUR1 receptor, and has a shorter duration of action [104]. The half-life of nateglinide and repaglinide at their respective receptors is about 2 seconds and 3 minutes, respectively [105]. Thus, the dissociation of nateglinide from its receptor is about 90 times faster, indicating a very short on-off effect on insulin release [104]. Of note, both drugs improve first-phase insulin release, but they do not affect the total daily amount of insulin released by the pancreas [106]. Meglitinides and Their Nitric Oxide Connection Nitric oxide is essential in regulating pancreatic islet blood flow [107]. Nateglinide contributes to increasing islet blood flow in a NO-dependent manner and enhances insulin secretion [107]. Nateglinide activates eNOS found mainly within the secretory granules of the pancreatic β-cells, resulting in increased NO production [107]. Repaglinide is used to reduce concentrations of fasting serum glucose, HbA1c, triglycerides, and free fatty acids [108]. Repaglinide can also increase serum

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insulin levels and high-density lipoprotein cholesterol (HDL-C). In T2D patients, repaglinide administration resulted in better brachial reactivity. Brachial reactivity, a measure of endothelial function, was determined using a highfrequency ultrasound technique. Endothelial function was measured through the flow-mediated dilatation of the brachial artery. Repaglinide increased the diameter and flow of the brachial artery, indicating improved endothelial function [109], which must be due to enhanced eNOS activity. High insulin levels increase neutrophil migration and could influence platelet endothelial cell adhesion molecule-1 levels on the endothelium [110]. When HUVECs were incubated with high insulin concentrations, there was an increase in neutrophil migration to the site. When the KATP channel blockers gliclazide, glibenclamide, glimepiride, and nateglinide, were preincubated with the insulin-enhanced HUVECs, neutrophil migration and PECAM-1 (platelet endothelial cell adhesion molecule-1) expression were inhibited only by gliclazide. Since the NOS inhibitors N(ω)nitro-L-arginine methyl ester (L-NAME) and L-NIO did not reverse the actions of gliclazide, it can be inferred that endogenous NO production was not involved in gliclazide’s activity. Instead, it was found that mitogen-activated protein kinase (MAPK) mediated gliclazide’s actions [111]. Gliclazide reduced the effects of the MAPK activator, anisomycin, on neutrophil transendothelial migration and endothelial PECAM-1 expression, independent of insulin [112]. Hyperglycemia that is seen in T2D increases ROS (reactive oxygen species), sequestering NO levels, promoting vasoconstrictors, and damaging the endothelium [18]. In T2D patients, nateglinide administration significantly increased NO levels, reduced blood glucose concentrations, improved insulin resistance, and decreased endothelial oxidative stress [113, 114]. DIPEPTIDYL PEPTIDASE-4 (DPP-4) INHIBITORS General Mechanism of Action DPP-4 Inhibitors such as sitagliptin, saxagliptin, linagliptin, and alogliptin reduce both fasting and postprandial hyperglycemia by inhibiting the incretins' degradation GLP-1 and glucose-dependent insulinotropic peptide (GIP). GLP-1 and GIP increase insulin release in response to an oral glucose load and are 1520% less functional in T2D patients [115]. In T2D, the secretions of these incretins decrease glucose levels by upregulating insulin [116] and inhibiting glucagon release [117]. Therefore, GLP-1 and GIP are involved in glucosedependent insulin release. DPP-4 rapidly degrades these hormones; thus, inhibiting this enzyme increases GLP-1 and GIP levels [118]. The decreased glucagon secretion and increased insulin secretion are responsible for an increased glucose uptake/utilization as well as a decline in the production

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of hepatic glucose, resulting in lower glucose and A1C (an average measure of blood glucose levels over 3 months) levels [118]. In T2D patients, DPP-4 inhibitors reduced fasting and postprandial glucose levels [119]. DPP-4 inhibitors can be used as monotherapy, but they are mainly prescribed combined with other drugs such as metformin. DPP-4 Inhibitors and Their Nitric Oxide Connection In T2D rats, eNOS expression in mesenteric arteries is decreased. When linagliptin was administered to these rats, there was increased eNOS activity and higher NO levels [120]. Active GLP-1, whose levels are upregulated through inhibition of DPP-4, have exhibited vasodilatory effects via NO and cGMP-reliant mechanisms [121]. Linagliptin also reduces superoxide levels caused by hyperglycemia via a radical scavenger mechanism [120]. This is quite important since oxidative stress uncouples eNOS and thus lowers NO levels contributing to endothelial dysfunction [122]. Since most patients with diabetes also have hypertension, the effects of saxagliptin were investigated on blood pressure and endothelial cell function in spontaneously hypertensive rats [123]. Saxagliptin administration increased aortic and/or glomerular NO levels decreased blood pressure, and ONOO- levels [123]. GLUCAGON-LIKE PEPTIDE 1 RECEPTOR (GLP-1) AGONISTS General Mechanism of Action GLP-1 agonists such as exenatide and liraglutide stimulate the incretin system in response to oral glucose to secrete insulin and reduce blood glucose levels [124, 125]. These drugs are injected subcutaneously and may be used alone or in combination with other antidiabetic drugs, including insulin and metformin. In combination therapy, GLP-1 agonists treat persistently high A1C and high blood glucose levels [126]. GLP-1 agonists and the DPP-4 inhibitors can reduce body weight through delayed gastric emptying and reduce both fasting and prandial glucose levels [127]. Upon food consumption, enteroendocrine K and L cells detect/recognize nutrients and release GLP-1. GLP-1 binds to pancreatic GLP-1 receptors to increase insulin [128] and reduce glucagon secretions [129]. GLP-1 agonists also reduce the absorption rate of sugars in the GI tract and act on the brain to reduce appetite [130]. They also induce satiety via a central effect on the hypothalamus, alongside their role in delaying gastric emptying [131]. Since the effects of natural GLP-1 are short-lived due to rapid degradation by the DPP-4 enzymes, GLP-1 receptor agonists were developed to mimic the effects of

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natural GLP-1 without rapid degradation [132]. Of note, an ultralong acting GLP1 agonist, semaglutide, which is subcutaneously administered once-weekly, has been shown (ClinicalTrials.gov, number NCT01930188) to be effective at improving glycaemic control and reducing body weight in patients with type 2 diabetes on metformin, thiazolidinediones, or both [133]. An oral formulation is also available (first approved oral GLP-1 receptor agonist). Although semaglutide has been approved as a second-line treatment option for better glycaemic control in type 2 diabetes and cardiovascular outcome trials have established that it can reduce various CV risk factors in patients with established CV disorders, it does have gastrointestinal adverse effects [134]. GLP-1 Receptor Agonists and Their Nitric Oxide Connection DPP-4 rapidly degrades the incretin hormone GLP-1(7-36), also called (GLP-1), to GLP-1(9-36), a truncated metabolite generally thought to be inactive. Using a DPP-4–resistant GLP-1 receptor agonist and inhibitors of DPP-4 and NOS showed that the effects of GLP-1(7-36) were partly mediated by GLP-1(9-36) through a NOS–requiring a mechanism that is independent of the known GLP-1R [121]. Both GLP-1(7-36) and GLP-1(9-36) improved coronary flow and vasodilation of resistance-level mesenteric arteries from wild-type and GLP-1R-/mice, this observation correlated with NO-dependent cGMP release. The vasodilation occurred through the L-arginine-NO pathway; this was verified by treating pre-contracted mesenteric arteries with L-NNA (a NOS inhibitor). LNNA inhibited vasodilation in response to GLP-1 and GLP-1(9-36), implying that vasodilation requires NOS [121]. In HUVECs, treatment with liraglutide stimulated NO production in a dosedependent manner, with the highest NO levels being produced at 3 hr with modest amounts at 4-5 hr [135]. NO production was highly dependent not only on the GLP-1 receptor but also on cAMP, cAMP-dependent protein kinase, AMPK, and eNOS. Liraglutide also targets endothelial cells and suppresses restenosis, resulting from coronary angioplasty in diabetes patients. The protective effects it exerts are maintained in hyperglycemic patients [136]. Administration of recombinant GLP-1 to T2D patients with co-existing coronary artery disease improved endothelial dysfunction. T2D patients have poor flow-mediated vasodilation (FMD) due to impaired NO production. After administering GLP-1, T2D patients demonstrated an increase in FMD, indicating that GLP-1 improved the endothelium’s functions through a NO-dependent mechanism [137]. GLP-1 agonists also can increase glucose-mediated uptake within skeletal muscles in a NO-dependent manner [138]. GLP-1 administration increased the plasma NO levels by 3-fold compared to the controls [139]. This elevation in NO

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levels allowed for enhanced glucose uptake by the muscles through NOdependent microvascular recruitment and insulin delivery. To ensure that this mechanism was NO-dependent, L-NAME abrogated the GLP-1 increase glucose uptake within the muscles [139]. GLP-1 mediated this mechanism by increasing protein kinase A (PKA) activity, which activates eNOS and hence NO levels [140]. ALPHA-GLUCOSIDASE INHIBITORS General Mechanism of Action Alpha-glucosidases are a family of enzymes, such as glucoamylase, sucrase, maltase, and isomaltase, that are present on the small intestinal brush border; they catalyze the final step in the digestion of complex non-absorbable carbohydrates into simple absorbable carbohydrates [141, 142]. Alpha-glucosidase inhibitors (AGI) such as acarbose, miglitol, and voglibose are competitive inhibitors of these enzymes and thus block the absorption of carbohydrates from the small intestine [142]. These drugs can suppress postprandial hyperglycemia by slowing down carbohydrate metabolism and absorption [143]. These drugs can be administered alone or combined with other antidiabetic drugs in the management of T2D. Alpha-Glucosidase Inhibitors and Their Nitric Oxide Connection AGIs increase NO and activate eNOS indirectly by stimulating GLP-1 [144]. Since AGIs prevent the breakdown of disaccharides, these undigested carbohydrates travel down the GI tract acting on L cells, and releasing GLP-1 [145]. GLP-1 is then involved in glucose-dependent insulin release [146] and NO production [147]. AGIs can be used to mitigate cardiovascular complications that are seen in T2D [148]. Voglibose administration to rabbits, by increasing GLP-1, reduced the size of myocardial infarctions [149]. Acarbose therapy of newly diagnosed T2D patients resulted in elevated GLP-1, serum insulin, serum NO, and eNOS activity [144]. SODIUM-GLUCOSE CO-TRANSPORTER 2 INHIBITORS (SGLT2) INHIBITORS General Mechanism of Action SGLT2 inhibitors are drugs that generally contain the suffix “glifozin,” e.g., empagliflozin, dapagliflozin, canagliflozin, ipragliflozin, and tofogliflozin. They can be used as a monotherapy, especially when patients cannot tolerate metformin or in combination with metformin or insulin. SGLT2 proteins are expressed within the proximal convoluted tubule of the kidneys [150] and are involved in

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the reabsorption of around 90% of filtered glucose [151]. Glucose is filtered from the glomerulus into Bowman's capsule located at the end of each nephron in the renal cortex. The presence of SGLT2 serves to transport the filtered glucose back into the tubular cell, where it is then entered the blood (i.e., reabsorption) [152]. SGLT2 inhibition results in glucose not being reabsorbed but is excreted in the urine [153]. In healthy individuals, around 180 mg/dL of glucose is reabsorbed through SGLT2. This threshold increases in patients with T2D and can increase blood glucose levels even more [154]. By inhibiting SGLT2, the glucose reabsorption threshold can drop to 40 to 120 mg/dL [155]. Unlike the mechanism associated with thiazolidinediones, SGLT2 inhibitors work independently of insulin's actions, which reduces the risks of low hypoglycemic levels [156]. The combination of SGLT2 inhibitors and insulin allows for glycemic maintenance without the possibility of weight gain. Multiple studies have shown that SGLT2 inhibition results in weight loss, caused by a reduction in available calories due to urinary glucose excretion and a reduction in the mass of both subcutaneous and visceral fat [157 - 159]. SGLT2 inhibitors also cause a non-dose-dependent decrease in systolic and diastolic blood pressure, which occurs due to osmotic diuresis and local rennin-angiotensin system inhibition [160]. It is important to mention that these drugs should not be taken in individuals with renal insufficiency since the glucose is not being reabsorbed and remains in the urine to be excreted [161]. SGLT2 Inhibitors and Their Nitric Oxide Connection Pretreatment of endothelial cells with phlorizin, an SGLT2 inhibitor, increased cytosolic Ca2+ levels due to induced glucose production [162]. This is significant because intracellular calcium activates eNOS activity, resulting in NO production. SGLT2 inhibition in neurogenic hypertensive mice protected against endothelial dysfunction and improved vascular function, possibly by reducing dimethylarginine levels, an endogenous NOS inhibitor [163]. In a recent study, administration of gliflozins (canagliflozin, dapagliflozin, and empagliflozin) to freshly isolated human platelets did not produce any toxic effects, but these drugs reduced platelet aggregation, intracellular calcium mobilization, thromboxane B2 levels, PAC-1 (procaspase-activating compound 1), and Akt expression, and this response was potentiated by NO plus prostaglandin I2 (PGI2). These results underscore the importance of these endothelium-derived factors in platelet inhibition and the protective cardiovascular profile of these compounds [164]. In a study involving type 2 diabetic patients who were administered SGLT2 inhibitors, the patients demonstrated reduced hospitalization rates for various

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outcomes, including heart failure, MI, and stroke, compared to patients taking other T2D drugs [165]. NITRATE-NITRITE-NO PATHWAY: A POTENTIAL THERAPEUTIC TARGET FOR T2D? Decreased eNOS-derived NO bioavailability, overproduction of iNOS-derived NO, and impaired nitrate-nitrite-NO pathway are involved in the pathogenesis of T2D [166, 167]. Supplementation with inorganic nitrate (NO3) or nitrite (NO2) to restore NO levels has been associated with many favorable metabolic outcomes in T2D [168, 169]. Inorganic NO3 and NO2 represent storage pools for NO and can complement or be an alternative to the NOS-dependent pathway. In animal models of T2D, supplementation of diets rich in inorganic NO3 and NO2 has effectively improved glucose and insulin homeostasis. NO3 and NO2 increase insulin secretion by increasing pancreatic blood flow and pancreatic islet insulin content [169, 170]. NO3 and NO2 increase insulin sensitivity by increasing GLUT4 expression and protein levels in epididymal adipose tissue, skeletal muscle, and translocation into the cell membrane, increasing the browning of white adipose tissue and decreasing adipocyte size [168, 169, 171, 172]. Of note, the favorable effects of NO on glucose and insulin homeostasis are comparable to metformin therapy [173]. Increasing endogenous levels of NO can decrease blood pressure and have numerous physiological benefits. NO can be derived from foods that contain sulfites. In the oral cavity, nitrite combined with dietary sulfites and later with the gastric juices in the stomach forms NO [174]. Dietary nitrates, which can be found in various food products such as vegetables, fruit, and processed meats, must first be reduced into nitrite before conversion to NO [175]. Commensal bacteria present on the tongue have an essential role in this process [47]. The vital role of oral microflora in nitrate reduction was underscored in several studies that utilized antiseptic mouthwash; when the function of the bacteria was tampered with, the positive/beneficial effects were eliminated. Antiseptic mouthwashes reduced oral nitrite production by 90% and decreased plasma nitrite levels by 25% [176]. Although NO3 and NO2 therapy have been effective in animal models of T2D, various pharmacological or dietary manipulations have failed to translate such beneficial effects on glucose and insulin parameters, including fasting and postprandial serum glucose and insulin concentrations, insulin resistance indices, and HbA1c levels to patients with T2D. The redox microenvironment affecting the conversion of ingested NO3 and its gastric conversion to NO2 and NO is suggested as a potential reason for this lost-in-translation [177], with ascorbic acid

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(AA) having a central role. Rats are AA-synthesizing species, whereas humans cannot synthesize AA and have a lower AA body pool and plasma concentrations. This may partly explain why humans with T2D do not benefit from NO3/NO2 supplementation. CONCLUDING REMARKS In patients with T2D, cardiovascular diseases are the leading cause of morbidity and mortality. NO induces vascular smooth muscle relaxation and reduces the risk of thrombosis by inhibiting platelet aggregation and adhesion [178]. Thus, a slow NO-releasing type 2 diabetic medication may be useful to circumvent the endogenous NO deficiency and endothelial dysfunction that is seen in T2D patients. To this end, several NO-releasing antidiabetic drugs have been reported [179, 180]. NO-glibenclamide (glyburide) derivatives have shown decreased endothelial dysfunction, and vascular inflammation in diabetic rats, displayed excellent vasorelaxant effects and gave robust hypoglycaemic activity [179]. This was due to the insulin secretagogue mechanism of action, typical of sulfonylureas. Various hybrid NO-releasing nateglinide and meglitinide have also shown appreciable anti-hyperglycemic activity that was comparable to the parent drugs in nonfasted diabetic rats [180]. The released NO from these prodrugs effectively lowered systolic and diastolic blood pressure in the T2D rats. Therefore, it would be interesting to see more hybrid NO donor type II antidiabetic prodrugs as these could potentially mitigate the risk of cardiovascular events frequently observed in diabetic individuals. Species differences in AA metabolism need to be considered when studies are being designed to evaluate the therapeutic applications of inorganic NO3 in animal models of T2D. Experimental studies using non-AA-synthesizing species, such as the guinea pig, are warranted to confirm that AA is responsible for the lost-i-translation of the antidiabetic effects of inorganic NO3. Since pharmacological and or dietary manipulations have failed to translate the beneficial impact of NO3 /NO2 on glucose and insulin parameters in humans, it would be quite worthwhile to repeat some of these studies in conjunction with AA supplementation. Finally, in the era of precision medicine, engineered platforms for drug delivery that are biocompatible in many contexts and degrade to form non-toxic metabolites are very attractive; efforts in this arena are in their infancy. CONSENT FOR PUBLICATION Not applicable.

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CONFLICT OF INTEREST The author declares no conflict of interest, financial or otherwise. ACKNOWLEDGMENTS Supported in part by the National Institutes of Health [R24 DA018055; R01GM123508] and the Professional Staff Congress-City University of New York (PSC-CUNY) [TRADB-49-271]. REFERENCES [1]

Brillat-Savarin JA. Physiologie du Goût, ou Méditations de Gastronomie Transcendante; ouvrage théorique, historique et à l'ordre du jour, dédié aux Gastronomes parisiens, par un Professeur, membre de plusieurs sociétés littéraires et savantes. 1825.

[2]

Abbt I. [Is man what he eats?]. Schweiz Rundsch Med Prax 1993; 82(38): 1029-32. [Is man what he eats?]. [PMID: 8210864]

[3]

Cherno M. Feuerbach’s “Man is what He Eats”: A Rectification. J Hist Ideas 1963; 24(3): 397-406. [http://dx.doi.org/10.2307/2708215]

[4]

Organization WH. Obesity and overweight. 2021.

[5]

Hales CM, Fryar CD, Carroll MD, Freedman DS, Ogden CL. Trends in Obesity and Severe Obesity Prevalence in US Youth and Adults by Sex and Age, 2007-2008 to 2015-2016. JAMA 2018; 319(16): 1723-5. [http://dx.doi.org/10.1001/jama.2018.3060] [PMID: 29570750]

[6]

Alemán JO, Eusebi LH, Ricciardiello L, Patidar K, Sanyal AJ, Holt PR. Mechanisms of obesityinduced gastrointestinal neoplasia. Gastroenterology 2014; 146(2): 357-73. [http://dx.doi.org/10.1053/j.gastro.2013.11.051] [PMID: 24315827]

[7]

Fontaine KR, Redden DT, Wang C, Westfall AO, Allison DB. Years of life lost due to obesity. JAMA 2003; 289(2): 187-93. [http://dx.doi.org/10.1001/jama.289.2.187] [PMID: 12517229]

[8]

Podell BK, Ackart DF, Richardson MA, DiLisio JE, Pulford B, Basaraba RJ. A model of type 2 diabetes in the guinea pig using sequential diet-induced glucose intolerance and streptozotocin treatment. Dis Model Mech 2017; 10(2): dmm.025593. [http://dx.doi.org/10.1242/dmm.025593] [PMID: 28093504]

[9]

Czech MP. Insulin action and resistance in obesity and type 2 diabetes. Nat Med 2017; 23(7): 804-14. [http://dx.doi.org/10.1038/nm.4350] [PMID: 28697184]

[10]

Chao JH, Hirsch IB. Initial Management of Severe Hyperglycemia in Type 2 Diabetes. In: Feingold KR, Anawalt B, Boyce A, Chrousos G, de Herder WW, Dhatariya K, Eds. Endotext. South Dartmouth, MA 2000.

[11]

Bellou V, Belbasis L, Tzoulaki I, Evangelou E. Risk factors for type 2 diabetes mellitus: An exposurewide umbrella review of meta-analyses. PLoS One 2018; 13(3): e0194127. [http://dx.doi.org/10.1371/journal.pone.0194127] [PMID: 29558518]

[12]

Chiu CJ, Milton RC, Gensler G, Taylor A. Dietary carbohydrate intake and glycemic index in relation to cortical and nuclear lens opacities in the Age-Related Eye Disease Study. Am J Clin Nutr 2006; 83(5): 1177-84. [http://dx.doi.org/10.1093/ajcn/83.5.1177] [PMID: 16685063]

226 The Role of Nitric Oxide in Type 2 Diabetes

Ranjbar et al.

[13]

Negre-Salvayre A, Salvayre R, Augé N, Pamplona R, Portero-Otín M. Hyperglycemia and glycation in diabetic complications. Antioxid Redox Signal 2009; 11(12): 3071-109. [http://dx.doi.org/10.1089/ars.2009.2484] [PMID: 19489690]

[14]

Hammes HP, Alt A, Niwa T, et al. Differential accumulation of advanced glycation end products in the course of diabetic retinopathy. Diabetologia 1999; 42(6): 728-36. [http://dx.doi.org/10.1007/s001250051221] [PMID: 10382593]

[15]

Ishibashi Y, Yamagishi S, Matsui T, et al. Pravastatin inhibits advanced glycation end products (AGEs)-induced proximal tubular cell apoptosis and injury by reducing receptor for AGEs (RAGE) level. Metabolism 2012; 61(8): 1067-72. [http://dx.doi.org/10.1016/j.metabol.2012.01.006] [PMID: 22386936]

[16]

Gheibi S, Samsonov AP, Gheibi S, Vazquez AB, Kashfi K. Regulation of carbohydrate metabolism by nitric oxide and hydrogen sulfide: Implications in diabetes. Biochem Pharmacol 2020; 176: 113819. [http://dx.doi.org/10.1016/j.bcp.2020.113819] [PMID: 31972170]

[17]

Bhardwaj A, Kaur J, Wuest F, Knaus EE. Do nitric oxide-releasing drugs offer a potentially new paradigm for the management of cardiovascular risks in diabetes? Expert Rev Cardiovasc Ther 2014; 12(5): 533-6. [http://dx.doi.org/10.1586/14779072.2014.897227] [PMID: 24725228]

[18]

Förstermann U. Oxidative stress in vascular disease: causes, defense mechanisms and potential therapies. Nat Clin Pract Cardiovasc Med 2008; 5(6): 338-49. [http://dx.doi.org/10.1038/ncpcardio1211] [PMID: 18461048]

[19]

Model List of Essential Medicines [Internet]. 2019. Available form: bitstream/handle/10665/325771/WHO-MVP-EMP-IAU-2019.06-eng.pdf

[20]

Grigorescu F, Laurent A, Chavanieu A, Capony JP. Cellular mechanism of metformin action. Diabete Metab 1991; 17(1 Pt 2): 146-9. [PMID: 1936468]

[21]

Klip A, Leiter LA. Cellular mechanism of action of metformin. Diabetes Care 1990; 13(6): 696-704. [http://dx.doi.org/10.2337/diacare.13.6.696] [PMID: 2162756]

[22]

Sanchez-Rangel E, Inzucchi SE. Metformin: clinical use in type 2 diabetes. Diabetologia 2017; 60(9): 1586-93. [http://dx.doi.org/10.1007/s00125-017-4336-x] [PMID: 28770321]

[23]

Hundal HS, Ramlal T, Reyes R, Leiter LA, Klip A. Cellular mechanism of metformin action involves glucose transporter translocation from an intracellular pool to the plasma membrane in L6 muscle cells. Endocrinology 1992; 131(3): 1165-73. [http://dx.doi.org/10.1210/endo.131.3.1505458] [PMID: 1505458]

[24]

Seifarth C, Schehler B, Schneider HJ. Effectiveness of metformin on weight loss in non-diabetic individuals with obesity. Exp Clin Endocrinol Diabetes 2013; 121(1): 27-31. [PMID: 23147210]

[25]

Wang DS, Jonker JW, Kato Y, Kusuhara H, Schinkel AH, Sugiyama Y. Involvement of organic cation transporter 1 in hepatic and intestinal distribution of metformin. J Pharmacol Exp Ther 2002; 302(2): 510-5. [http://dx.doi.org/10.1124/jpet.102.034140] [PMID: 12130709]

[26]

Natali A, Ferrannini E. Effects of metformin and thiazolidinediones on suppression of hepatic glucose production and stimulation of glucose uptake in type 2 diabetes: a systematic review. Diabetologia 2006; 49(3): 434-41. [http://dx.doi.org/10.1007/s00125-006-0141-7] [PMID: 16477438]

[27]

Vial G, Detaille D, Guigas B. Role of Mitochondria in the Mechanism(s) of Action of Metformin. Front Endocrinol (Lausanne) 2019; 10: 294. [http://dx.doi.org/10.3389/fendo.2019.00294] [PMID: 31133988]

https://apps.who.int/iris/

NO and T2DM Drugs

The Role of Nitric Oxide in Type 2 Diabetes 227

[28]

Ross FA, MacKintosh C, Hardie DG. AMP-activated protein kinase: a cellular energy sensor that comes in 12 flavours. FEBS J 2016; 283(16): 2987-3001. [http://dx.doi.org/10.1111/febs.13698] [PMID: 26934201]

[29]

Hardie DG, Carling D. The AMP-activated protein kinase--fuel gauge of the mammalian cell? Eur J Biochem 1997; 246(2): 259-73. [http://dx.doi.org/10.1111/j.1432-1033.1997.00259.x] [PMID: 9208914]

[30]

Hardie DG, Carling D, Carlson M. The AMP-activated/SNF1 protein kinase subfamily: metabolic sensors of the eukaryotic cell? Annu Rev Biochem 1998; 67(1): 821-55. [http://dx.doi.org/10.1146/annurev.biochem.67.1.821] [PMID: 9759505]

[31]

Stapleton D, Mitchelhill KI, Gao G, et al. Mammalian AMP-activated protein kinase subfamily. J Biol Chem 1996; 271(2): 611-4. [http://dx.doi.org/10.1074/jbc.271.2.611] [PMID: 8557660]

[32]

Zhou G, Myers R, Li Y, et al. Role of AMP-activated protein kinase in mechanism of metformin action. J Clin Invest 2001; 108(8): 1167-74. [http://dx.doi.org/10.1172/JCI13505] [PMID: 11602624]

[33]

Johanns M, Lai YC, Hsu MF, et al. AMPK antagonizes hepatic glucagon-stimulated cyclic AMP signalling via phosphorylation-induced activation of cyclic nucleotide phosphodiesterase 4B. Nat Commun 2016; 7(1): 10856. [http://dx.doi.org/10.1038/ncomms10856] [PMID: 26952277]

[34]

Rena G, Hardie DG, Pearson ER. The mechanisms of action of metformin. Diabetologia 2017; 60(9): 1577-85. [http://dx.doi.org/10.1007/s00125-017-4342-z] [PMID: 28776086]

[35]

Hardie DG, Ross FA, Hawley SA. AMPK: a nutrient and energy sensor that maintains energy homeostasis. Nat Rev Mol Cell Biol 2012; 13(4): 251-62. [http://dx.doi.org/10.1038/nrm3311] [PMID: 22436748]

[36]

Vincent MF, Marangos PJ, Gruber HE, van den Berghe G. Inhibition by AICA riboside of gluconeogenesis in isolated rat hepatocytes. Diabetes 1991; 40(10): 1259-66. [http://dx.doi.org/10.2337/diab.40.10.1259] [PMID: 1657665]

[37]

Owen MR, Doran E, Halestrap AP. Evidence that metformin exerts its anti-diabetic effects through inhibition of complex 1 of the mitochondrial respiratory chain. Biochem J 2000; 348(3): 607-14. [http://dx.doi.org/10.1042/bj3480607] [PMID: 10839993]

[38]

El-Mir MY, Nogueira V, Fontaine E, Avéret N, Rigoulet M, Leverve X. Dimethylbiguanide inhibits cell respiration via an indirect effect targeted on the respiratory chain complex I. J Biol Chem 2000; 275(1): 223-8. [http://dx.doi.org/10.1074/jbc.275.1.223] [PMID: 10617608]

[39]

Goodyear LJ. AMP-activated protein kinase: a critical signaling intermediary for exercise-stimulated glucose transport? Exerc Sport Sci Rev 2000; 28(3): 113-6. [PMID: 10916702]

[40]

McGarry JD, Brown NF. The mitochondrial carnitine palmitoyltransferase system. From concept to molecular analysis. Eur J Biochem 1997; 244(1): 1-14. [http://dx.doi.org/10.1111/j.1432-1033.1997.00001.x] [PMID: 9063439]

[41]

Kashfi K, Cook GA. Topology of hepatic mitochondrial carnitine palmitoyltransferase I. Adv Exp Med Biol 1999; 466: 27-42. [http://dx.doi.org/10.1007/0-306-46818-2_3] [PMID: 10709625]

[42]

Musi N, Hirshman MF, Nygren J, et al. Metformin increases AMP-activated protein kinase activity in skeletal muscle of subjects with type 2 diabetes. Diabetes 2002; 51(7): 2074-81. [http://dx.doi.org/10.2337/diabetes.51.7.2074] [PMID: 12086935]

228 The Role of Nitric Oxide in Type 2 Diabetes

Ranjbar et al.

[43]

Hotamisligil GS, Shargill NS, Spiegelman BM. Adipose expression of tumor necrosis factor-alpha: direct role in obesity-linked insulin resistance. Science 1993; 259(5091): 87-91. [http://dx.doi.org/10.1126/science.7678183] [PMID: 7678183]

[44]

Bender SB, Herrick EK, Lott ND, Klabunde RE. Diet-induced obesity and diabetes reduce coronary responses to nitric oxide due to reduced bioavailability in isolated mouse hearts. Diabetes Obes Metab 2007; 9(5): 688-96. [http://dx.doi.org/10.1111/j.1463-1326.2006.00650.x] [PMID: 17697061]

[45]

Valerio A, Cardile A, Cozzi V, et al. TNF- downregulates eNOS expression and mitochondrial biogenesis in fat and muscle of obese rodents. J Clin Invest 2006; 116(10): 2791-8. [http://dx.doi.org/10.1172/JCI28570.] [PMID: 16981010]

[46]

Shimabukuro M, Ohneda M, Lee Y, Unger RH. Role of nitric oxide in obesity-induced beta cell disease. J Clin Invest 1997; 100(2): 290-5. [http://dx.doi.org/10.1172/JCI119534] [PMID: 9218505]

[47]

Fujimoto M, Shimizu N, Kunii K, Martyn JAJ, Ueki K, Kaneki M. A role for iNOS in fasting hyperglycemia and impaired insulin signaling in the liver of obese diabetic mice. Diabetes 2005; 54(5): 1340-8. [http://dx.doi.org/10.2337/diabetes.54.5.1340] [PMID: 15855318]

[48]

Lumeng CN, Bodzin JL, Saltiel AR. Obesity induces a phenotypic switch in adipose tissue macrophage polarization. J Clin Invest 2007; 117(1): 175-84. [http://dx.doi.org/10.1172/JCI29881] [PMID: 17200717]

[49]

Sansbury BE, Hill BG. Regulation of obesity and insulin resistance by nitric oxide. Free Radic Biol Med 2014; 73: 383-99. [http://dx.doi.org/10.1016/j.freeradbiomed.2014.05.016] [PMID: 24878261]

[50]

Morley JE, Flood JF. Evidence that nitric oxide modulates food intake in mice. Life Sci 1991; 49(10): 707-11. [http://dx.doi.org/10.1016/0024-3205(91)90102-H] [PMID: 1875780]

[51]

De Luca B, Monda M, Sullo A. Changes in eating behavior and thermogenic activity following inhibition of nitric oxide formation. Am J Physiol 1995; 268(6 Pt 2): R1533-8. [PMID: 7611531]

[52]

Herrero MB, Viggiano JM, Perez MS, de GMF. Effects of nitric oxide synthase inhibitors on the outcome of in vitro fertilization in the mouse. Reprod Fertil Dev 1996; 8(2): 301-4. [http://dx.doi.org/10.1071/RD9960301] [PMID: 8726870]

[53]

Tousoulis D, Kampoli AM, Tentolouris Nikolaos Papageorgiou C, Stefanadis C, Stefanadis C. The role of nitric oxide on endothelial function. Curr Vasc Pharmacol 2012; 10(1): 4-18. [http://dx.doi.org/10.2174/157016112798829760] [PMID: 22112350]

[54]

An H, Wei R, Ke J, et al. Metformin attenuates fluctuating glucose-induced endothelial dysfunction through enhancing GTPCH1-mediated eNOS recoupling and inhibiting NADPH oxidase. J Diabetes Complications 2016; 30(6): 1017-24. [http://dx.doi.org/10.1016/j.jdiacomp.2016.04.018] [PMID: 27217019]

[55]

Matheus ASM, Tannus LRM, Cobas RA, Palma CCS, Negrato CA, Gomes MB. Impact of diabetes on cardiovascular disease: an update. Int J Hypertens 2013; 2013: 1-15. [http://dx.doi.org/10.1155/2013/653789] [PMID: 23533715]

[56]

Widlansky ME, Gokce N, Keaney JF Jr, Vita JA. The clinical implications of endothelial dysfunction. J Am Coll Cardiol 2003; 42(7): 1149-60. [http://dx.doi.org/10.1016/S0735-1097(03)00994-X] [PMID: 14522472]

[57]

Sambe T, Mason RP, Dawoud H, Bhatt DL, Malinski T. Metformin treatment decreases nitroxidative stress, restores nitric oxide bioavailability and endothelial function beyond glucose control. Biomed Pharmacother 2018; 98: 149-56.

NO and T2DM Drugs

The Role of Nitric Oxide in Type 2 Diabetes 229

[http://dx.doi.org/10.1016/j.biopha.2017.12.023] [PMID: 29253762] [58]

Eggleton JS, Jialal I. Thiazolidinediones. Treasure Island, FL: StatPearls 2021.

[59]

Yau H, Rivera K, Lomonaco R, Cusi K. The future of thiazolidinedione therapy in the management of type 2 diabetes mellitus. Curr Diab Rep 2013; 13(3): 329-41. [http://dx.doi.org/10.1007/s11892-013-0378-8] [PMID: 23625197]

[60]

Vieira R, Souto SB, Sánchez-López E, et al. Sugar-Lowering Drugs for Type 2 Diabetes Mellitus and Metabolic Syndrome—Strategies for In Vivo Administration: Part-II. J Clin Med 2019; 8(9): 1332. [http://dx.doi.org/10.3390/jcm8091332] [PMID: 31466386]

[61]

Tyagi S, Sharma S, Gupta P, Saini AS, Kaushal C. The peroxisome proliferator-activated receptor: A family of nuclear receptors role in various diseases. J Adv Pharm Technol Res 2011; 2(4): 236-40. [http://dx.doi.org/10.4103/2231-4040.90879] [PMID: 22247890]

[62]

Kim H, Ahn Y. Role of peroxisome proliferator-activated receptor-gamma in the glucose-sensing apparatus of liver and beta-cells. Diabetes 2004; 53 (Suppl. 1): S60-5. [http://dx.doi.org/10.2337/diabetes.53.2007.S60] [PMID: 14749267]

[63]

Choi SS, Park J, Choi JH. Revisiting PPARγ as a target for the treatment of metabolic disorders. BMB Rep 2014; 47(11): 599-608. [http://dx.doi.org/10.5483/BMBRep.2014.47.11.174] [PMID: 25154720]

[64]

Ferré P. The biology of peroxisome proliferator-activated receptors: relationship with lipid metabolism and insulin sensitivity. Diabetes 2004; 53 (Suppl. 1): S43-50. [http://dx.doi.org/10.2337/diabetes.53.2007.S43] [PMID: 14749265]

[65]

Laplante M, Sell H, MacNaul KL, Richard D, Berger JP, Deshaies Y. PPAR-gamma activation mediates adipose depot-specific effects on gene expression and lipoprotein lipase activity: mechanisms for modulation of postprandial lipemia and differential adipose accretion. Diabetes 2003; 52(2): 291-9. [http://dx.doi.org/10.2337/diabetes.52.2.291] [PMID: 12540599]

[66]

Dubois M, Vantyghem MC, Schoonjans K, Pattou F. [Thiazolidinediones in type 2 diabetes. Role of peroxisome proliferator-activated receptor gamma (PPARgamma)]. Ann Endocrinol (Paris) 2002; 63(6 Pt 1): 511-23. [Thiazolidinediones in type 2 diabetes. Role of peroxisome proliferator-activated receptor gamma (PPARgamma)]. [PMID: 12527853]

[67]

Boden G, Homko C, Mozzoli M, Showe LC, Nichols C, Cheung P. Thiazolidinediones upregulate fatty acid uptake and oxidation in adipose tissue of diabetic patients. Diabetes 2005; 54(3): 880-5. [http://dx.doi.org/10.2337/diabetes.54.3.880] [PMID: 15734868]

[68]

Feingold KR. Dyslipidemia in Diabetes. In: Feingold KR, Anawalt B, Boyce A, Chrousos G, Eds. Endotext South Dartmouth (MA): MDTextcom, Inc. 2000.

[69]

Yu JG, Javorschi S, Hevener AL, et al. The effect of thiazolidinediones on plasma adiponectin levels in normal, obese, and type 2 diabetic subjects. Diabetes 2002; 51(10): 2968-74. [http://dx.doi.org/10.2337/diabetes.51.10.2968] [PMID: 12351435]

[70]

Yamanouchi T. Concomitant therapy with pioglitazone and insulin for the treatment of type 2 diabetes. Vasc Health Risk Manag 2010; 6: 189-97. [http://dx.doi.org/10.2147/VHRM.S5838] [PMID: 20407626]

[71]

Floyd JS, Barbehenn E, Lurie P, Wolfe SM. Case series of liver failure associated with rosiglitazone and pioglitazone. Pharmacoepidemiol Drug Saf 2009; 18(12): 1238-43. [http://dx.doi.org/10.1002/pds.1804] [PMID: 19623674]

[72]

Thiazolidinediones Y-JH. N Engl J Med 2004; 351(11): 1106-18. [http://dx.doi.org/10.1056/NEJMra041001] [PMID: 15356308]

[73]

Calnek DS, Mazzella L, Roser S, Roman J, Hart CM. Peroxisome proliferator-activated receptor gamma ligands increase release of nitric oxide from endothelial cells. Arterioscler Thromb Vasc Biol

230 The Role of Nitric Oxide in Type 2 Diabetes

Ranjbar et al.

2003; 23(1): 52-7. [http://dx.doi.org/10.1161/01.ATV.0000044461.01844.C9] [PMID: 12524224] [74]

Imanishi T, Kobayashi K, Kuroi A, et al. Effects of angiotensin II on NO bioavailability evaluated using a catheter-type NO sensor. Hypertension 2006; 48(6): 1058-65. [http://dx.doi.org/10.1161/01.HYP.0000248920.16956.d8] [PMID: 17060506]

[75]

Imanishi T, Kuroi A, Ikejima H, et al. Effects of pioglitazone on nitric oxide bioavailability measured using a catheter-type nitric oxide sensor in angiotensin II-infusion rabbit. Hypertens Res 2008; 31(1): 117-25. [http://dx.doi.org/10.1291/hypres.31.117] [PMID: 18360026]

[76]

Lu X, Guo X, Karathanasis SK, et al. Rosiglitazone reverses endothelial dysfunction but not remodeling of femoral artery in Zucker diabetic fatty rats. Cardiovasc Diabetol 2010; 9(1): 19. [http://dx.doi.org/10.1186/1475-2840-9-19] [PMID: 20482873]

[77]

Pistrosch F, Herbrig K, Kindel B, Passauer J, Fischer S, Gross P. Rosiglitazone improves glomerular hyperfiltration, renal endothelial dysfunction, and microalbuminuria of incipient diabetic nephropathy in patients. Diabetes 2005; 54(7): 2206-11. [http://dx.doi.org/10.2337/diabetes.54.7.2206] [PMID: 15983223]

[78]

Veelken R, Hilgers KF, Hartner A, Haas A, Böhmer KP, Sterzel RB. Nitric oxide synthase isoforms and glomerular hyperfiltration in early diabetic nephropathy. J Am Soc Nephrol 2000; 11(1): 71-9. [http://dx.doi.org/10.1681/ASN.V11171] [PMID: 10616842]

[79]

Rosen CJ. The rosiglitazone story--lessons from an FDA Advisory Committee meeting. N Engl J Med 2007; 357(9): 844-6. [http://dx.doi.org/10.1056/NEJMp078167] [PMID: 17687124]

[80]

Costello RA, Shivkumar A. Sulfonylureas. Treasure Island, FL: StatPearls 2021.

[81]

Sola D, Rossi L, Schianca GPC, et al. State of the art paper Sulfonylureas and their use in clinical practice. Arch Med Sci 2015; 4(4): 840-8. [http://dx.doi.org/10.5114/aoms.2015.53304] [PMID: 26322096]

[82]

Proks P, Reimann F, Green N, Gribble F, Ashcroft F. Sulfonylurea stimulation of insulin secretion. Diabetes 2002; 51 (Suppl. 3): S368-76. [http://dx.doi.org/10.2337/diabetes.51.2007.S368] [PMID: 12475777]

[83]

Daniels EL, Lewis SB. Acute tolbutamide administration alone or combined with insulin enhances glucose uptake in the perfused rat hindlimb. Endocrinology 1982; 110(5): 1840-2. [http://dx.doi.org/10.1210/endo-110-5-1840] [PMID: 7042317]

[84]

Matsutani A, Kaku K, Kaneko T. Tolbutamide stimulates fructose-2, 6-bisphosphate formation in perfused rat liver. Diabetes 1984; 33(5): 495-8. [http://dx.doi.org/10.2337/diab.33.5.495] [PMID: 6547102]

[85]

Tan BH, Wilson GL, Schaffer SW. Effect of tolbutamide on myocardial metabolism and mechanical performance of the diabetic rat. Diabetes 1984; 33(12): 1138-43. [http://dx.doi.org/10.2337/diab.33.12.1138] [PMID: 6500190]

[86]

Cook GA. The hypoglycemic sulfonylureas glyburide and tolbutamide inhibit fatty acid oxidation by inhibiting carnitine palmitoyltransferase. J Biol Chem 1987; 262(11): 4968-72. [http://dx.doi.org/10.1016/S0021-9258(18)61140-8] [PMID: 3104327]

[87]

Ashcroft FM, Gribble FM. ATP-sensitive K + channels and insulin secretion: their role in health and disease. Diabetologia 1999; 42(8): 903-19. [http://dx.doi.org/10.1007/s001250051247] [PMID: 10491749]

[88]

Aguilar-Bryan L, Bryan J. Molecular biology of adenosine triphosphate-sensitive potassium channels. Endocr Rev 1999; 20(2): 101-35. [PMID: 10204114]

NO and T2DM Drugs

The Role of Nitric Oxide in Type 2 Diabetes 231

[89]

Nichols CG, Shyng SL, Nestorowicz A, et al. Adenosine diphosphate as an intracellular regulator of insulin secretion. Science 1996; 272(5269): 1785-7. [http://dx.doi.org/10.1126/science.272.5269.1785] [PMID: 8650576]

[90]

Gribble FM, Davis TME, Higham CE, Clark A, Ashcroft FM. The antimalarial agent mefloquine inhibits ATP-sensitive K-channels. Br J Pharmacol 2000; 131(4): 756-60. [http://dx.doi.org/10.1038/sj.bjp.0703638] [PMID: 11030725]

[91]

Gribble FM, Tucker SJ, Seino S, Ashcroft FM. Tissue specificity of sulfonylureas: studies on cloned cardiac and beta-cell K(ATP) channels. Diabetes 1998; 47(9): 1412-8. [http://dx.doi.org/10.2337/diabetes.47.9.1412] [PMID: 9726229]

[92]

Del Prato S, Pulizzi N. The place of sulfonylureas in the therapy for type 2 diabetes mellitus. Metabolism 2006; 55(5) (Suppl. 1): S20-7. [http://dx.doi.org/10.1016/j.metabol.2006.02.003] [PMID: 16631807]

[93]

Scognamiglio R, Avogaro A, Vigili de Kreutzenberg S, et al. Effects of treatment with sulfonylurea drugs or insulin on ischemia-induced myocardial dysfunction in type 2 diabetes. Diabetes 2002; 51(3): 808-12. [http://dx.doi.org/10.2337/diabetes.51.3.808] [PMID: 11872684]

[94]

Johnsen SP, Monster TB, Olsen ML, et al. Risk and short-term prognosis of myocardial infarction among users of antidiabetic drugs. Am J Ther 2006; 13(2): 134-40. [http://dx.doi.org/10.1097/00045391-200603000-00009] [PMID: 16645430]

[95]

Salani B, Repetto S, Cordera R, Maggi D. Glimepiride activates eNOS with a mechanism Akt but not caveolin-1 dependent. Biochem Biophys Res Commun 2005; 335(3): 832-5. [http://dx.doi.org/10.1016/j.bbrc.2005.07.149] [PMID: 16099429]

[96]

Ueba H, Kuroki M, Hashimoto S, et al. Glimepiride induces nitric oxide production in human coronary artery endothelial cells via a PI3-kinase-Akt dependent pathway. Atherosclerosis 2005; 183(1): 35-9. [http://dx.doi.org/10.1016/j.atherosclerosis.2005.01.055] [PMID: 16216590]

[97]

Kelly KL, Ruderman NB. Insulin-stimulated phosphatidylinositol 3-kinase. Association with a 185kDa tyrosine-phosphorylated protein (IRS-1) and localization in a low density membrane vesicle. J Biol Chem 1993; 268(6): 4391-8. [http://dx.doi.org/10.1016/S0021-9258(18)53622-X] [PMID: 8382701]

[98]

Motoyama K, Koyama H, Moriwaki M, et al. Atheroprotective and plaque-stabilizing effects of enzymatically modified isoquercitrin in atherogenic apoE-deficient mice. Nutrition 2009; 25(4): 421-7. [http://dx.doi.org/10.1016/j.nut.2008.08.013] [PMID: 19026522]

[99]

Altan N, Buğdayci G, Tutkun FK, Sancak B, Nazaroğlu NK. The effect of the sulfonylurea glyburide on nitric oxide in streptozotocin-induced diabetic rat. Gen Pharmacol 1998; 31(2): 319-21. [http://dx.doi.org/10.1016/S0306-3623(97)00430-8] [PMID: 9688480]

[100] Landgraf R. Meglitinide analogues in the treatment of type 2 diabetes mellitus. Drugs Aging 2000; 17(5): 411-25. [http://dx.doi.org/10.2165/00002512-200017050-00007] [PMID: 11190420] [101] Analogues M. LiverTox: Clinical and Research Information on Drug-Induced Liver Injury. Bethesda (MD)2012. 2012. [102] Guardado-Mendoza R, Prioletta A, Jiménez-Ceja LM, Sosale A, Folli F. State of the art paper The role of nateglinide and repaglinide, derivatives of meglitinide, in the treatment of type 2 diabetes mellitus. Arch Med Sci 2013; 5(5): 936-43. [http://dx.doi.org/10.5114/aoms.2013.34991] [PMID: 24273582] [103] Fuhlendorff J, Rorsman P, Kofod H, et al. Stimulation of insulin release by repaglinide and glibenclamide involves both common and distinct processes. Diabetes 1998; 47(3): 345-51. [http://dx.doi.org/10.2337/diabetes.47.3.345] [PMID: 9519738]

232 The Role of Nitric Oxide in Type 2 Diabetes

Ranjbar et al.

[104] Hu S. Interaction of nateglinide with KATP channel in β-cells underlies its unique insulinotropic action. Eur J Pharmacol 2002; 442(1-2): 163-71. [http://dx.doi.org/10.1016/S0014-2999(02)01499-1] [PMID: 12020694] [105] Hu S, Wang S, Fanelli B, et al. Pancreatic beta-cell K(ATP) channel activity and membrane-binding studies with nateglinide: A comparison with sulfonylureas and repaglinide. J Pharmacol Exp Ther 2000; 293(2): 444-52. [PMID: 10773014] [106] Paolisso G, Rizzo MR, Barbieri M, Manzella D, Ragno E, Maugeri D. Cardiovascular risk in type 2 diabetics and pharmacological regulation of mealtime glucose excursions. Diabetes Metab 2003; 29(4): 335-40. [http://dx.doi.org/10.1016/S1262-3636(07)70044-7] [PMID: 14526261] [107] Iwase M, Nakamura U, Uchizono Y, et al. Nateglinide, a non-sulfonylurea rapid insulin secretagogue, increases pancreatic islet blood flow in rats. Eur J Pharmacol 2005; 518(2-3): 243-50. [http://dx.doi.org/10.1016/j.ejphar.2005.05.044] [PMID: 16023099] [108] Owens DR. Repaglinide – prandial glucose regulator: a new class of oral antidiabetic drugs. Diabet Med 1998; 15(S4) (Suppl. 4): S28-36. [http://dx.doi.org/10.1002/(SICI)1096-9136(1998120)15:4+3.0.CO;2-T] [PMID: 9868989] [109] Manzella D, Grella R, Abbatecola AM, Paolisso G. Repaglinide administration improves brachial reactivity in type 2 diabetic patients. Diabetes Care 2005; 28(2): 366-71. [http://dx.doi.org/10.2337/diacare.28.2.366] [PMID: 15677794] [110] M O, N O, S I, et al. High insulin enhances neutrophil transendothelial migration through increasing surface expression of platelet endothelial cell adhesion molecule-1 via activation of mitogen activated protein kinase. Diabetologia 2002; 45(10): 1449-56. [http://dx.doi.org/10.1007/s00125-002-0902-x] [PMID: 12378388] [111] Okouchi M, Okayama N, Omi H, et al. The antidiabetic agent, gliclazide, reduces high insulin–enhanced neutrophil-transendothelial migration through direct effects on the endothelium. Diabetes Metab Res Rev 2004; 20(3): 232-8. [http://dx.doi.org/10.1002/dmrr.444] [PMID: 15133755] [112] Kumar N, Dey CS. Gliclazide increases insulin receptor tyrosine phosphorylation but not p38 phosphorylation in insulin-resistant skeletal muscle cells. J Exp Biol 2002; 205(23): 3739-46. [http://dx.doi.org/10.1242/jeb.205.23.3739] [PMID: 12409500] [113] Wang L, Guo L, Zhang L, et al. Effects of glucose load and nateglinide intervention on endothelial function and oxidative stress. J Diabetes Res 2013; 2013: 1-9. [http://dx.doi.org/10.1155/2013/849295] [PMID: 23691521] [114] Shimabukuro M, Higa N, Takasu N, Tagawa T, Ueda S. A single dose of nateglinide improves postchallenge glucose metabolism and endothelial dysfunction in Type 2 diabetic patients. Diabet Med 2004; 21(9): 983-6. [http://dx.doi.org/10.1111/j.1464-5491.2004.01272.x] [PMID: 15317602] [115] Muscelli E, Mari A, Casolaro A, et al. Separate impact of obesity and glucose tolerance on the incretin effect in normal subjects and type 2 diabetic patients. Diabetes 2008; 57(5): 1340-8. [http://dx.doi.org/10.2337/db07-1315] [PMID: 18162504] [116] Kjems LL, Holst JJ, Vølund A, Madsbad S. The influence of GLP-1 on glucose-stimulated insulin secretion: effects on beta-cell sensitivity in type 2 and nondiabetic subjects. Diabetes 2003; 52(2): 380-6. [http://dx.doi.org/10.2337/diabetes.52.2.380] [PMID: 12540611] [117] Holst JJ, Toft-Nielsen MB, Ørskov C, Nauck M, Willms B. On the effects of glucagon-like peptide-1 on blood glucose regulation in normal and diabetic subjects. Ann N Y Acad Sci 1996; 805(1): 729-36.

NO and T2DM Drugs

The Role of Nitric Oxide in Type 2 Diabetes 233

[http://dx.doi.org/10.1111/j.1749-6632.1996.tb17549.x] [PMID: 8993469] [118] Vella A, Smushkin G. Inhibition of dipeptidyl peptidase-4: The mechanisms of action and clinical use of vildagliptin for the management of type 2 diabetes. Diabetes Metab Syndr Obes 2009; 2: 83-90. [http://dx.doi.org/10.2147/DMSO.S4790] [PMID: 21437121] [119] Ahrén B, Landin-Olsson M, Jansson PA, Svensson M, Holmes D, Schweizer A. Inhibition of dipeptidyl peptidase-4 reduces glycemia, sustains insulin levels, and reduces glucagon levels in type 2 diabetes. J Clin Endocrinol Metab 2004; 89(5): 2078-84. [http://dx.doi.org/10.1210/jc.2003-031907] [PMID: 15126524] [120] Salheen SM, Panchapakesan U, Pollock CA, Woodman OL. The Dipeptidyl Peptidase-4 Inhibitor Linagliptin Preserves Endothelial Function in Mesenteric Arteries from Type 1 Diabetic Rats without Decreasing Plasma Glucose. PLoS One 2015; 10(11): e0143941. [http://dx.doi.org/10.1371/journal.pone.0143941] [PMID: 26618855] [121] Ban K, Noyan-Ashraf MH, Hoefer J, Bolz SS, Drucker DJ, Husain M. Cardioprotective and vasodilatory actions of glucagon-like peptide 1 receptor are mediated through both glucagon-like peptide 1 receptor-dependent and -independent pathways. Circulation 2008; 117(18): 2340-50. [http://dx.doi.org/10.1161/CIRCULATIONAHA.107.739938] [PMID: 18427132] [122] Schulz E, Jansen T, Wenzel P, Daiber A, Münzel T. Nitric oxide, tetrahydrobiopterin, oxidative stress, and endothelial dysfunction in hypertension. Antioxid Redox Signal 2008; 10(6): 1115-26. [http://dx.doi.org/10.1089/ars.2007.1989] [PMID: 18321209] [123] Mason RP, Jacob RF, Kubant R, Ciszewski A, Corbalan JJ, Malinski T. Dipeptidyl peptidase-4 inhibition with saxagliptin enhanced nitric oxide release and reduced blood pressure and sICAM-1 levels in hypertensive rats. J Cardiovasc Pharmacol 2012; 60(5): 467-73. [http://dx.doi.org/10.1097/FJC.0b013e31826be204] [PMID: 22932707] [124] Collins L, Costello RA. Glucagon-like Peptide-1 Receptor Agonists. Treasure Island, FL: StatPearls 2021. [125] DeFronzo RA. Banting Lecture. From the triumvirate to the ominous octet: a new paradigm for the treatment of type 2 diabetes mellitus. Diabetes 2009; 58(4): 773-95. [http://dx.doi.org/10.2337/db09-9028] [PMID: 19336687] [126] Garber AJ, Abrahamson MJ, Barzilay JI, et al. Consensus Statement By The American Association Of Clinical Endocrinologists And American College Of Endocrinology On The Comprehensive Type 2 Diabetes Management Algorithm – 2016 EXECUTIVE SUMMARY. Endocr Pract 2016; 22(1): 84113. [http://dx.doi.org/10.4158/EP151126.CS] [PMID: 26731084] [127] Ahrén B, Schmitz O. GLP-1 receptor agonists and DPP-4 inhibitors in the treatment of type 2 diabetes. Horm Metab Res 2004; 36(11/12): 867-76. [http://dx.doi.org/10.1055/s-2004-826178] [PMID: 15655721] [128] Nauck MA, Wollschläger D, Werner J, et al. Effects of subcutaneous glucagon-like peptide 1 (GLP-1 [7-36 amide]) in patients with NIDDM. Diabetologia 1996; 39(12): 1546-53. [http://dx.doi.org/10.1007/s001250050613] [PMID: 8960841] [129] Baggio LL, Drucker DJ. Biology of Incretins: GLP-1 and GIP. Gastroenterology 2007; 132(6): 213157. [http://dx.doi.org/10.1053/j.gastro.2007.03.054] [PMID: 17498508] [130] Vilsbøll T, Christensen M, Junker AE, Knop FK, Gluud LL. Effects of glucagon-like peptide-1 receptor agonists on weight loss: systematic review and meta-analyses of randomised controlled trials. BMJ 2012; 344(jan10 2): d7771. [http://dx.doi.org/10.1136/bmj.d7771] [PMID: 22236411] [131] Nauck MA, Niedereichholz U, Ettler R, et al. Glucagon-like peptide 1 inhibition of gastric emptying outweighs its insulinotropic effects in healthy humans. Am J Physiol 1997; 273(5): E981-8.

234 The Role of Nitric Oxide in Type 2 Diabetes

Ranjbar et al.

[PMID: 9374685] [132] Gupta V. Glucagon-like peptide-1 analogues: An overview. Indian J Endocrinol Metab 2013; 17(3): 413-21. [http://dx.doi.org/10.4103/2230-8210.111625] [PMID: 23869296] [133] Ahrén B, Masmiquel L, Kumar H, et al. Efficacy and safety of once-weekly semaglutide versus oncedaily sitagliptin as an add-on to metformin, thiazolidinediones, or both, in patients with type 2 diabetes (SUSTAIN 2): a 56-week, double-blind, phase 3a, randomised trial. Lancet Diabetes Endocrinol 2017; 5(5): 341-54. [http://dx.doi.org/10.1016/S2213-8587(17)30092-X] [PMID: 28385659] [134] Mahapatra MK, Karuppasamy M, Sahoo BM. Semaglutide, a glucagon like peptide-1 receptor agonist with cardiovascular benefits for management of type 2 diabetes. Rev Endocr Metab Disord 2022; 23(3): 521-39. [http://dx.doi.org/10.1007/s11154-021-09699-1] [PMID: 34993760] [135] Hattori Y, Jojima T, Tomizawa A, et al. RETRACTED ARTICLE: A glucagon-like peptide-1 (GLP1) analogue, liraglutide, upregulates nitric oxide production and exerts anti-inflammatory action in endothelial cells. Diabetologia 2010; 53(10): 2256-63. [http://dx.doi.org/10.1007/s00125-010-1831-8] [PMID: 20593161] [136] Kushima H, Mori Y, Koshibu M, et al. The role of endothelial nitric oxide in the anti-restenotic effects of liraglutide in a mouse model of restenosis. Cardiovasc Diabetol 2017; 16(1): 122. [http://dx.doi.org/10.1186/s12933-017-0603-x] [PMID: 28969637] [137] Nyström T, Gutniak MK, Zhang Q, et al. Effects of glucagon-like peptide-1 on endothelial function in type 2 diabetes patients with stable coronary artery disease. Am J Physiol Endocrinol Metab 2004; 287(6): E1209-15. [http://dx.doi.org/10.1152/ajpendo.00237.2004] [PMID: 15353407] [138] Ayala JE, Bracy DP, James FD, Julien BM, Wasserman DH, Drucker DJ. The glucagon-like peptide-1 receptor regulates endogenous glucose production and muscle glucose uptake independent of its incretin action. Endocrinology 2009; 150(3): 1155-64. [http://dx.doi.org/10.1210/en.2008-0945] [PMID: 19008308] [139] Chai W, Dong Z, Wang N, et al. Glucagon-like peptide 1 recruits microvasculature and increases glucose use in muscle via a nitric oxide-dependent mechanism. Diabetes 2012; 61(4): 888-96. [http://dx.doi.org/10.2337/db11-1073] [PMID: 22357961] [140] Dixit M, Loot AE, Mohamed A, et al. Gab1, SHP2, and protein kinase A are crucial for the activation of the endothelial NO synthase by fluid shear stress. Circ Res 2005; 97(12): 1236-44. [http://dx.doi.org/10.1161/01.RES.0000195611.59811.ab] [PMID: 16284184] [141] Sou S, Takahashi H, Yamasaki R, Kagechika H, Endo Y, Hashimoto Y. Alpha-glucosidase inhibitors with a 4,5,6,7-tetrachlorophthalimide skeleton pendanted with a cycloalkyl or dicarba-clos-dodecaborane group. Chem Pharm Bull (Tokyo) 2001; 49(6): 791-3. [http://dx.doi.org/10.1248/cpb.49.791] [PMID: 11411542] [142] Kumar V, Prakash O, Kumar S, Narwal S. α-glucosidase inhibitors from plants: A natural approach to treat diabetes. Pharmacogn Rev 2011; 5(9): 19-29. [http://dx.doi.org/10.4103/0973-7847.79096] [PMID: 22096315] [143] Akmal M, Wadhwa R. Alpha Glucosidase Inhibitors. Treasure Island, FL: StatPearls 2021. [144] Zheng M, Yang J, Shan C, et al. Effects of 24-week treatment with acarbose on glucagon-like peptide 1 in newly diagnosed type 2 diabetic patients: a preliminary report. Cardiovasc Diabetol 2013; 12(1): 73. [http://dx.doi.org/10.1186/1475-2840-12-73] [PMID: 23642288] [145] Qualmann C, Nauck MA, Holst JJ, øSrskov C, Creutzfeldt W. Glucagon-like peptide 1 (7-36 amide) secretion in response to luminal sucrose from the upper and lower gut. A study using alpha-

NO and T2DM Drugs

The Role of Nitric Oxide in Type 2 Diabetes 235

glucosidase inhibition (acarbose). Scand J Gastroenterol 1995; 30(9): 892-6. [http://dx.doi.org/10.3109/00365529509101597] [PMID: 8578189] [146] Drucker DJ. The biology of incretin hormones. Cell Metab 2006; 3(3): 153-65. [http://dx.doi.org/10.1016/j.cmet.2006.01.004] [PMID: 16517403] [147] Gresele P, Migliacci R, Arosio E, Bonizzoni E, Minuz P, Violi F, et al. Effect on walking distance and atherosclerosis progression of a nitric oxide-donating agent in intermittent claudication. J Vasc Surg 2012; 56(6): 1622-8. [148] Hanefeld M, Cagatay M, Petrowitsch T, Neuser D, Petzinna D, Rupp M. Acarbose reduces the risk for myocardial infarction in type 2 diabetic patients: meta-analysis of seven long-term studies. Eur Heart J 2004; 25(1): 10-6. [http://dx.doi.org/10.1016/S0195-668X(03)00468-8] [PMID: 14683737] [149] Iwasa M, Kobayashi H, Yasuda S, et al. Antidiabetic drug voglibose is protective against ischemiareperfusion injury through glucagon-like peptide 1 receptors and the phosphoinositide 3-kinase-At-endothelial nitric oxide synthase pathway in rabbits. J Cardiovasc Pharmacol 2010; 55(6): 625-34. [http://dx.doi.org/10.1097/FJC.0b013e3181dcd240] [PMID: 20351564] [150] Scheen AJ. Pharmacodynamics, efficacy and safety of sodium-glucose co-transporter type 2 (SGLT2) inhibitors for the treatment of type 2 diabetes mellitus. Drugs 2015; 75(1): 33-59. [http://dx.doi.org/10.1007/s40265-014-0337-y] [PMID: 25488697] [151] Fioretto P, Giaccari A, Sesti G. Efficacy and safety of dapagliflozin, a sodium glucose cotransporter 2 (SGLT2) inhibitor, in diabetes mellitus. Cardiovasc Diabetol 2015; 14(1): 142. [http://dx.doi.org/10.1186/s12933-015-0297-x] [PMID: 26474563] [152] Kalra S. Sodium Glucose Co-Transporter-2 (SGLT2) Inhibitors: A Review of Their Basic and Clinical Pharmacology. Diabetes Ther 2014; 5(2): 355-66. [http://dx.doi.org/10.1007/s13300-014-0089-4] [PMID: 25424969] [153] Lee YJ, Lee YJ, Han HJ. Regulatory mechanisms of Na + /glucose cotransporters in renal proximal tubule cells. Kidney Int 2007; 72(106): S27-35. [http://dx.doi.org/10.1038/sj.ki.5002383] [PMID: 17653207] [154] Moses R, Colagiuri S, Pollock C. SGLT2 inhibitors: New medicines for addressing unmet needs in type 2 diabetes. Australas Med J 2014; 7(10): 405-15. [http://dx.doi.org/10.4066/AMJ.2014.2181] [PMID: 25379062] [155] Desouza CV, Gupta N, Patel A. Cardiometabolic Effects of a New Class of Antidiabetic Agents. Clin Ther 2015; 37(6): 1178-94. [http://dx.doi.org/10.1016/j.clinthera.2015.02.016] [PMID: 25754876] [156] Nauck M. Update on developments with SGLT2 inhibitors in the management of type 2 diabetes. Drug Des Devel Ther 2014; 8: 1335-80. [http://dx.doi.org/10.2147/DDDT.S50773] [PMID: 25246775] [157] Scheen AJ. Pharmacokinetic and pharmacodynamic profile of empagliflozin, a sodium glucose cotransporter 2 inhibitor. Clin Pharmacokinet 2014; 53(3): 213-25. [http://dx.doi.org/10.1007/s40262-013-0126-x] [PMID: 24430725] [158] Khamseh ME, Prusty V, Latif Z, Gonzalez-Galvez G, Dieuzeide G, Zilov A. Type 2 diabetes mellitus management and body mass index: experiences with initiating insulin detemir in the a1chieve study. Diabetes Ther 2014; 5(1): 127-40. [http://dx.doi.org/10.1007/s13300-014-0054-2] [PMID: 24477670] [159] Bolinder J, Ljunggren Ö, Kullberg J, et al. Effects of dapagliflozin on body weight, total fat mass, and regional adipose tissue distribution in patients with type 2 diabetes mellitus with inadequate glycemic control on metformin. J Clin Endocrinol Metab 2012; 97(3): 1020-31. [http://dx.doi.org/10.1210/jc.2011-2260] [PMID: 22238392] [160] Lambers Heerspink HJ, de Zeeuw D, Wie L, Leslie B, List J. Dapagliflozin a glucose-regulating drug

236 The Role of Nitric Oxide in Type 2 Diabetes

Ranjbar et al.

with diuretic properties in subjects with type 2 diabetes. Diabetes Obes Metab 2013; 15(9): 853-62. [http://dx.doi.org/10.1111/dom.12127] [PMID: 23668478] [161] Scheen AJ. Pharmacokinetics, Pharmacodynamics and Clinical Use of SGLT2 Inhibitors in Patients with Type 2 Diabetes Mellitus and Chronic Kidney Disease. Clin Pharmacokinet 2015; 54(7): 691708. [http://dx.doi.org/10.1007/s40262-015-0264-4] [PMID: 25805666] [162] Taubert D, Rosenkranz A, Berkels R, Roesen R, Schömig E. Acute effects of glucose and insulin on vascular endothelium. Diabetologia 2004; 47(12): 2059-71. [http://dx.doi.org/10.1007/s00125-004-1586-1] [PMID: 15662548] [163] Herat LY, Magno AL, Rudnicka C, et al. SGLT2 Inhibitor–Induced Sympathoinhibition. JACC Basic Transl Sci 2020; 5(2): 169-79. [http://dx.doi.org/10.1016/j.jacbts.2019.11.007] [PMID: 32140623] [164] Lescano CH, Leonardi G, Torres PHP, et al. The sodium-glucose cotransporter-2 (SGLT2) inhibitors synergize with nitric oxide and prostacyclin to reduce human platelet activation. Biochem Pharmacol 2020; 182: 114276. [http://dx.doi.org/10.1016/j.bcp.2020.114276] [PMID: 33039417] [165] Kosiborod M, Cavender MA, Fu AZ, et al. Lower Risk of Heart Failure and Death in Patients Initiated on Sodium-Glucose Cotransporter-2 Inhibitors Versus Other Glucose-Lowering Drugs. Circulation 2017; 136(3): 249-59. [http://dx.doi.org/10.1161/CIRCULATIONAHA.117.029190] [PMID: 28522450] [166] Carlström M, Larsen FJ, Nyström T, et al. Dietary inorganic nitrate reverses features of metabolic syndrome in endothelial nitric oxide synthase-deficient mice. Proc Natl Acad Sci USA 2010; 107(41): 17716-20. [http://dx.doi.org/10.1073/pnas.1008872107] [PMID: 20876122] [167] Bahadoran Z, Mirmiran P, Ghasemi A. Role of Nitric Oxide in Insulin Secretion and Glucose Metabolism. Trends Endocrinol Metab 2020; 31(2): 118-30. [http://dx.doi.org/10.1016/j.tem.2019.10.001] [PMID: 31690508] [168] Gheibi S, Bakhtiarzadeh F, Jeddi S, Farrokhfall K, Zardooz H, Ghasemi A. Nitrite increases glucosestimulated insulin secretion and islet insulin content in obese type 2 diabetic male rats. Nitric oxide: biology and chemistry 2017; 64: 39-41. [http://dx.doi.org/10.1016/j.niox.2017.01.003] [169] Gheibi S, Jeddi S, Carlstrom M, Gholami H, Ghasemi A. Effects of long-term nitrate supplementation on carbohydrate metabolism, lipid profiles, oxidative stress, and inflammation in male obese type 2 diabetic rats. Nitric oxide: biology and chemistry 2018; 75: 27-41. [http://dx.doi.org/10.1016/j.niox.2018.02.002] [170] Nyström T, Ortsäter H, Huang Z, et al. Inorganic nitrite stimulates pancreatic islet blood flow and insulin secretion. Free Radic Biol Med 2012; 53(5): 1017-23. [http://dx.doi.org/10.1016/j.freeradbiomed.2012.06.031] [PMID: 22750508] [171] Roberts LD, Ashmore T, Kotwica AO, et al. Inorganic nitrate promotes the browning of white adipose tissue through the nitrate-nitrite-nitric oxide pathway. Diabetes 2015; 64(2): 471-84. [http://dx.doi.org/10.2337/db14-0496] [PMID: 25249574] [172] Ohtake K, Nakano G, Ehara N, Sonoda K, Ito J, Uchida H, et al. Dietary nitrite supplementation improves insulin resistance in type 2 diabetic KKA(y) mice. Nitric oxide: biology and chemistry 2015; 44: 31-8. [173] Cordero-Herrera I, Guimarães DD, Moretti C, Zhuge Z, Han H, McCann Haworth S, et al. Head-t-head comparison of inorganic nitrate and metformin in a mouse model of cardiometabolic disease. Nitric oxide: biology and chemistry 2020; 97: 48-56. [http://dx.doi.org/10.1016/j.niox.2020.01.013]

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[174] Takahama U, Hirota S. Effects of the food additive sulfite on nitrite-dependent nitric oxide production under conditions simulating the mixture of saliva and gastric juice. J Agric Food Chem 2012; 60(4): 1102-12. [http://dx.doi.org/10.1021/jf2049257] [PMID: 22224438] [175] Hord NG, Tang Y, Bryan NS. Food sources of nitrates and nitrites: the physiologic context for potential health benefits. Am J Clin Nutr 2009; 90(1): 1-10. [http://dx.doi.org/10.3945/ajcn.2008.27131] [PMID: 19439460] [176] Kapil V, Haydar SMA, Pearl V, Lundberg JO, Weitzberg E, Ahluwalia A. Physiological role for nitrate-reducing oral bacteria in blood pressure control. Free Radic Biol Med 2013; 55: 93-100. [http://dx.doi.org/10.1016/j.freeradbiomed.2012.11.013] [PMID: 23183324] [177] Bahadoran Z, Mirmiran P, Kashfi K, Ghasemi A. Lost-in-Translation of Metabolic Effects of Inorganic Nitrate in Type 2 Diabetes: Is Ascorbic Acid the Answer? Int J Mol Sci 2021; 22(9): 4735. [http://dx.doi.org/10.3390/ijms22094735] [PMID: 33947005] [178] Butler AR, Williams DLH. The physiological role of nitric oxide. Chem Soc Rev 1993; 22(4): 233-41. [http://dx.doi.org/10.1039/cs9932200233] [179] Calderone V, Rapposelli S, Martelli A, et al. NO-glibenclamide derivatives: Prototypes of a new class of nitric oxide-releasing anti-diabetic drugs. Bioorg Med Chem 2009; 17(15): 5426-32. [http://dx.doi.org/10.1016/j.bmc.2009.06.049] [PMID: 19595600] [180] Kaur J, Bhardwaj A, Huang Z, et al. Synthesis and biological investigations of nitric oxide releasing nateglinide and meglitinide type II antidiabetic prodrugs: in-vivo antihyperglycemic activities and blood pressure lowering studies. J Med Chem 2012; 55(17): 7883-91. [http://dx.doi.org/10.1021/jm300997w] [PMID: 22916833]

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CHAPTER 11

Brain Insulin Resistance, Nitric Oxide and Alzheimer’s Disease Pathology Zhe Pei1, Kuo-Chieh Lee1, Amber Khan1,2 and Hoau-Yan Wang1,2,* Department of Molecular, Cellular and Biomedical Sciences, City University of New York School of Medicine, 160 Convent Avenue, New York, New York 10031, USA. 2 Department of Biology, Neuroscience Program, Graduate School of The City University of New York, 365 Fifth Avenue, New York, New York 10061, USA. 1

Abstract: Alzheimer’s disease (AD) is a devastating age-related neurodegenerative disease characterized by progressive pathological changes and functional and cognitive impairments. Brain insulin resistance appears to contribute significantly to the pathology and cognitive deficits among several pathological mechanisms. Brain insulin resistance has been demonstrated in animal models of AD and postmortem human brain tissue from patients with AD dementia. Studies conducted in AD models and humans suggest attenuating brain insulin resistance by agents such as glucagon-like peptide1 (GLP-1) analogs and small molecule drug candidate PTI-125 reduces many AD pathologic features and symptoms. Insulin affects NO levels by activating endothelial and neuronal nitric oxide synthase (eNOS, nNOS), and systemic insulin resistance has been linked to reduced nitric oxide (NO) bioavailability. Increasing NO availability reduces systemic insulin resistance, and the insulin signaling pathway is associated with the activation of eNOS, implying a causal relationship. This chapter explores this relationship and the role of impaired NO availability in brain insulin resistance in AD dementia.

Keywords: α-Amino-3-Hydroxy-5-Methyl-4-Isoxazolepropionic Acid (AMPA) Receptor, CaMKII (Calcium-Calmodulin-Dependent Kinase II), GammaAminobutyric acid (GABA) Receptor, Glutamate, Insulin Resistance, NADPH Oxidase 2 (Nox2), NADPH Oxidase Subunit NOX2, NG-Monomethyl-LArginine (L-NMMA), Nitric Oxide Synthase (NOS), N-methyl-D-Aspartate (NMDA) Receptor, Reactive Oxygen Species (ROS), Type-2 Diabetes (T2D).

* *Corresponding author Hoau-Yan Wang: Department of Molecular, Cellular and Biomedical Sciences, City University of New York School of Medicine, 160 Convent Avenue, New York, NY 10031, USA. Email: [email protected]

Asghar Ghasemi, Khosrow Kashfi, Zahra Bahadoran (Eds.) All rights reserved-© 2022 Bentham Science Publishers

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INTRODUCTION Alzheimer’s disease (AD) is a progressive neurodegenerative disorder with many underlying pathophysiological changes that gradually lead to dementia [1 - 4].The lack of effective treatments for AD dementia and the enormous socioeconomic impact on society underscores the urgent need to develop effective treatments for this devastating disease [5, 6]. Many promising therapeutic agents in development for AD aim to reduce brain insulin resistance, a common early pathological feature of AD dementia with or without diabetes [7 - 10]. The pathological factors that contribute to brain insulin resistance are not fully understood. Nitric oxide (NO) is one of several biological molecules that interact with the insulin signaling pathway bi-directionally. In this chapter, we discuss the role of the NO system in the development of brain insulin resistance and explore the possibility that manipulating NO might be therapeutic for AD dementia. INSULIN RECEPTOR SIGNALING AND ITS INTERACTION WITH NO SYSTEM Insulin, a peptide secreted by the beta (β) cells in the pancreas, crosses the bloodbrain barrier in a regulated and saturable manner to enter the central nervous system (CNS). Although de novo synthesis of insulin in the brain is still debated, support for local brain insulin synthesis includes the detection of C-peptide and insulin mRNA in various brain regions in humans, with the mRNA levels, being especially high in the hippocampus, striatum, and thalamus [11 - 15]. Insulin expression is decreased in AD compared to normal controls [14]. Insulin produces its cellular actions by binding its cognate insulin receptors (IRs) present on all cells, including neurons and glia in brain regions such as the olfactory bulb, cerebral cortex, hippocampus, hypothalamus, and amygdala [8, 16, 17]. IRs are more concentrated in neurons relative to glial cells and are particularly highly expressed in postsynaptic densities [8, 16 - 18]. Upon insulin binding to the extracellular α-subunit domains of IRs, the intracellular IR βsubunit domains dimerize, leading to activation of their intrinsic tyrosine kinase to cause autophosphorylation. Insulin-like growth factor-1 (IGF-1) also binds and activates IRs with lower affinity, leading to the same trophic and metabolic actions as insulin, including neuronal plasticity [19, 20]. In addition to regulation of glucose utilization and homeostasis, insulin activates PI3K-Akt (Phosphoinositide 3-kinase - Protein kinase B/Akt) and mTOR (Mechanistic target of rapamycin) signaling via recruitment of insulin receptor substrate family (IRS) proteins, such as IRS-1 and IRS-2. This insulin-stimulated PI3K/Akt/mTOR pathway has many other functions in cells throughout the body, including the neuronal and vascular systems. Insulin activates Akt via IRS1-PI3K

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to directly phosphorylate serine1177 residues and activate vascular endothelial NO synthase (eNOS), leading to NO production and consequent vasodilation and increased capillary blood flow [21, 22]. Insulin signaling promoting NO-mediated vasodilation in the brain is supported by increased blood flow in the insular cortex following intranasal insulin in men, independent of cortisol manipulation [23]. Expression of eNOS has been shown not only in the endothelium of the cerebrovasculature but, more importantly, in dendritic spines [24]. Innate eNOS activity confers protection against secondary neuronal injury; thus, impaired eNOS due to insufficient insulin signaling in the brain can conceivably contribute to pathologies in AD, leading to cognitive impairments [25]. Insulin has been shown to modulate a wide range of neuronal functions. Insulin regulates 1) trafficking of ligand-gated ion channels, 2) expression and localization of GABA (γ-Aminobutyric acid), NMDA (N-Methyl-D-aspartic acid or N-Methyl-D-aspartate), and AMPA (α-amino-3-hydroxy-5-mehyl-4-isoxazolepropionic acid) receptors, 3) catecholamine release and uptake, and 4) synaptic plasticity shown by long-term potentiation (LTP) and depression (LTD) in an NMDA receptor and PI3K dependent manner [26 - 29]. Insulin also promotes dendritic spine formation and excitatory synaptic development, and insulin regulates the development and health of excitatory synapses by activating PI3K/Akt/mTOR and Rac1/Cdc42 signaling [30]. Activation of the NMDA receptor recruits and activates neuronal NO synthase (nNOS) via Akt- and CaMKII(Ca2+/calmodulin-dependent protein kinase II)mediated phosphorylation of nNOS to promote the production of NO in the postsynaptic field [31, 32]. The activation of nNOS was also found to elevate AMPA receptor levels [32]. Thus, insulin can increase NO production in postsynaptic neurons by stimulating nNOS via activation of NMDA receptors. Increased NO promotes NADPH oxidase 2 (NOX2)-dependent ROS production postsynaptically, which may damage the dendritic field. Dendritic field destruction is one of the pathological changes in AD [33]. The importance of NO in modulating insulin receptor activity has also been illustrated by the blockade of the phosphatases SHP-1(Src homology region 2 domain-containing phosphatase-1), SHP-2(SH2 domain-containing protein tyrosine phosphatase-2), and PTP1B (Protein Tyrosine Phosphatase 1B) by Snitrosylation of the cysteine residue at the enzyme’s active sites concomitantly with a burst of NO production in response to insulin [34, 35]. Inhibition of the PTP1B, SHP-1, and SHP-2 by S-nitrosylation release inhibition of tyrosine phosphatases on insulin signaling. Hence, increased NO levels can promote NOdependent tyrosine-phosphorylated insulin receptors and its downstream effector

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IRS-1, thereby facilitating insulin signaling [35, 36]. Such potentiation of the insulin signaling could offset insulin resistance and related pathologies in AD. In contrast to the positive action of NO on insulin signaling in the endothelial cells, intracerebroventricular infusion of the NO donor S-nitrosoglutathione (GSNO) impairs insulin signaling and induces inducible NO synthase (iNOS) expression in the hypothalamus. This impaired insulin signaling (insulin resistance) and induction of iNOS recapitulates the food consumption pattern of obese individuals [37]. This NO-mediated suppression of insulin signaling was linked to S-nitrosylation of IR and its downstream signaling molecule, Akt, in the hypothalamus [37]. In accord, inhibition of iNOS or blocking S-nitrosylation of insulin signaling pathway reduces hypothalamic insulin resistance and normalizes energy homeostasis. However, the effects of intraventricular infusion of GSNO on levels of insulin signaling in other brain regions, especially the cognition-relevant hippocampus and cortex, remain unclear. Moreover, although these studies highlight the reciprocal interactions between the NO system and the insulin signaling pathways that are important for maintaining the functionality of a cell or the much more complex brain, especially in the presence of diseases such as Alzheimer’s disease (Fig. 1), these studies also indicate that NO’s influence on insulin signaling is cell-type-dependent, such that the functional output of diverse organs and brain regions are differentially affected. The Inter-Relationship between Memory/Cognitive Performance

Brain

Insulin

Signaling

and

Brain insulin signaling is an important regulator of food intake, body weight, reproduction, and learning and memory [10, 38]. Memory is the most relevant to AD pathogenesis among the many physiological activities regulated by brain insulin signaling. Several lines of evidence support the notion that brain insulin signaling plays a critical role in modulating cognitive function. Intranasal insulin administration improves cognition, including short- and long-term objective memory and working memory in animals and humans [38 - 43]. Intraventricular insulin administration improves memory and reduces chronic neuroinflammation in young but not old rats [44]. Intracerebroventricular administration of insulin improves passive avoidance task performance [45].

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Fig. (1). Reciprocal interactions between insulin signaling cascades and nitric oxide (NO) system in the brain. Insulin signaling is initiated by binding insulin (IN) to its cognate receptor, insulin receptors (IRs). This leads to autophosphorylation on tyrosine residues (pY) and activation of the IRs. The activation of IRs recruits (and tyrosine-phosphorylated) IRS-1 and the adaptor, Shc, leading to the activation of two parallel downstream PI3K/Akt/mTOR and Ras/Raf/MEK/MAPK pathways, respectively. Activation of PI3K/Akt/mTOR pathway can activate eNOS expressed in the endothelium of the cerebrovasculature and dendritic field by triggering phosphorylation on serine1177 residue of endothelial NO synthase (eNOS), thereby increasing NO production. IR activation can also potentiate NMDA receptors (NMDARs) activities to increase intracellular Ca2+ and recruitment and activation of the neuronal NO synthase (nNOS), resulting in increased NO production. The increase in NO production facilitates insulin-induced IR signaling and synaptic activation by inhibiting phosphatases, including PTP1B, SHIP1, and SHIP2, by promoting S-nitrosylation of these molecules, causing direct vasodilation and promoting anti-oxidative and -inflammatory activities under physiological conditions. Insulin signaling through activation of the Ras/Raf/MEK/MAPK cascade can suppress the production of proinflammatory cytokines such as tumor necrotic factor α (TNFα) via activation of transforming growth factor β (TGFβ), thereby reducing ROS production. Conversely, the aberrantly elevated proinflammatory cytokines in the brain of neurodegenerative diseases such as Alzheimer’s disease can disrupt the redox balance and increase reactive oxygen species (ROS), leading to brain insulin resistance, NMDAR impairments, and endothelial dysfunction by reducing eNOS expression, thereby reduces NO availability. In contrast to the positive effects of NO on insulin signaling, inducible NO synthase (iNOS), a mediator of inflammation, plays an important role in stress-induced insulin resistance probably by promoting S-nitrosylation of the IR and its downstream signaling molecule, Akt. Lastly, the heightened inflammatory processes in neurodegeneration can increase NO levels and the potential for brain insulin resistance, thereby accelerating pathology and cognitive impairment in Alzheimer’s disease. IRS-1: insulin receptor substrate-1; PI3 kinase: phosphatidylinositol 3 kinase; NMDAR: N-methyl-D-aspartate receptors; MAPK: mitogenactivated protein kinase; PTP1B: protein tyrosine phosphatase 1B; SHIP1: SH-2 containing inositol 5' polyphosphatase 1; SHIP2: SH-2 containing inositol 5' polyphosphatase 2; IL-6: Interleukin 6; IL-1β: Interleukin 1β. indicates a prominent positive contributor, indicates a minor or potential positive contributor, and indicates a negative contributor.

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Similarly, direct intra-hippocampal administration enhances spatial learning and memory [46 - 48]. In addition, increased IR mRNA and protein levels in the hippocampal CA1 region after a spatial memory task correlates with short-term memory formation [49]. The critical role of brain insulin signaling in facilitating cognition is also supported by genetic modulation of the insulin signaling cascade. Selective disruption of insulin signaling by antisense knockdown of the IR gene in hippocampi of rats impairs synaptic plasticity and spatial learning [50]. After learning-induced long-term memory consolidation, gene expression of IR in the hippocampal CA1 and CA3 regions was increased and decreased, respectively, together with a reduction in IR protein levels [51]. The learning experience and long-term memory formation also result in specific increases in levels of downstream molecules, such as IRS-1 and Akt, together with decreases in Akt activation (phosphorylation), recruitment of adaptor Shc, and activation of ERK1/2(Extracellular signal-regulated protein kinase1/2) [51]. These studies imply that activation of the brain insulin signaling facilitates cognitive function and that learning and memory formation reciprocally promotes neuronal insulin signaling. However, the notion that brain insulin signaling is critical to cognition, was not supported by a report showing that mice that had lost 95% of IRs and downstream signaling due to neuron-specific insulin receptor knockout (NIRKO) show unimpaired learning and memory or behavior in various cognitive tests [52]. Accumulating evidence also supports the notion that insulin positively influences neuronal activities in the brain and cognition in humans. Activating brain insulin signaling by acute intranasal insulin administration promotes neuroelectrophysiological activities, such as event-related and transcortical direct current shift [53, 54]. Similarly, intranasal insulin application also positively influences neuroimaging measurements [55, 56]. Acute and chronic intranasal administration of insulin improves memory and cognitive performance in healthy young adults, obese or type-2 diabetic older subjects, and even memory-impaired subjects ([38, 39, 57 - 63]. In contrast, no cognitive or functional benefits were observed with 12-month intranasal insulin administration to mild cognitive impairment and AD dementia patients in a randomized (1:1) double-blind clinical trial [64]. In contrast to the positive role of brain insulin signaling on cognitive performance, disruption of insulin signaling makes neurons more vulnerable to metabolic stress and accelerates neuronal dysfunction, leading to cognitive decline and dementia, including AD [8, 65 - 69]. Severity-correlated reductions in cognitive performance in type-2 diabetes (T2D) and AD are associated with a decrease in brain IR expression and the phosphorylation of the insulin signaling molecules with lower CSF (Cerebrospinal fluid) insulin levels in both AD and T2D patient brains [70].

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Decreased insulin signaling, including altered IR kinase activity and IRS expression, and increased basal (non-stimulated) activation (indicated by IRS-1 phosphorylation) become more prominent as AD progresses [8, 71 - 73]. Although IR protein levels were comparable in AD and control brains, the IR was distributed throughout the cell soma and dendrites of neurons in controls but was predominantly intracellular in AD neurons [8, 9, 72, 74]. The reduced insulin signaling in the AD brain was correlated with decreased IRS-1 and IRS-2 levels and the robust co-localization of the elevated phosphorylated S312- and S616IRS-1 with neurofibrillary tangles [72]. Impaired brain insulin signaling, indicated by an increased basal AKT phosphorylation and implied compromised insulin-driven AKT activation, is associated with AD neuropathology and lower cognitive function [75]. Resonating with the concept that decreased brain insulin signaling is a key pathogenic event in AD, the brain areas with the highest IR levels, such as the hippocampus and temporal lobe, have the greatest neuronal vulnerability and neurodegenerative pathology in AD [76, 77]. Together, the data reviewed here suggest that impaired insulin signaling is a key contributor to cognitive decline and the neuropathology of AD. Hence, failure to improve cognition by the 12-month intranasal insulin administration to mild cognitive impairment and AD dementia patients may be due to too severe insulin resistance in these trial subjects [64]. The Role of No in Brain Insulin Resistance and Cognitive Performance Brain insulin resistance refers to a reduced or failed response to insulin of brain cells. It may be caused by reduced IR protein levels, reduced binding affinity, or inability to recruit adaptor proteins and activate downstream signaling cascades such as PI3K-Akt. Reduced insulin responsiveness contributes to impaired neuroplasticity, neurotransmission with aberrant receptor regulation and/or neurotransmitter release, glucose uptake into GLUT4 (Glucose transporter type 4) -expressing neurons, and altered insulin-elicited homeostatic or inflammatory responses in glial cells. Ultimately, brain insulin resistance can disturb systemic metabolism, impair cognition, and cause psychiatric problems. Brain insulin resistance can occur in AD without apparent systemic insulin resistance or metabolic syndromes such as T2D [8, 9, 74]. Although the causal factors of brain insulin resistance are diverse and not yet fully elucidated, studies on systemic insulin resistance suggest that changes in the NO system interacting with IR signaling may contribute.

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Table 1 summarizes the cause-effect relationship between NOS changes and insulin resistance and/or cognitive performance. Table 1. Studies examine the cause-and-effect relationship between altered NO availability and insulin receptor signaling, cognition and/or Alzheimer’s disease pathology. NOS

Species/Manipulation

NO Level

IR

Cognitive Effects/AD Pathology

Ref.

nNOS

Hu. None

↑

-

None

[78]

nNOS

APP23 mice

↑

-

associate astrocytic APP

[79]

nNOS eNOS

NOS-KO Mice ICV L-NMMA

↓

+

None

[80]

nNOS

Rat ICV L-NMMA

↓

+

None

[81]

nNOS

Rat/Rabbit L-NMMA

↓

-

nNOS

Rat L-NMMA

↓

-

nNOS

Hu. None

nNOS

Mice NOS-KO 7-NI

↓

-

nNOS

Rat TRIM/7-NI

↓

-

nNOS

Mice 7-NI

↓

-

nNOS

Rat 7-NI

↓

-

Impaired learning and memory formation

[87]

nNOS

Rat L-arginine/ 7-NI

↓

-

NO positively affects working memory

[88]

iNOS

Hu. None

-

iNOS and eNOS were highly expressed in astrocytes in AD

[78]

Hu. None

↑

-

iNOS expression increases in temporal cortical neurons and astrocytes

[84]

iNOS

↑

-

iNOS

Calcium-dependent NOS enzymatic activity decreases; iNOS increases (neuron, microglia) in the AD model

[89]

Mice Tg2576 APP

iNOS

Rat 1400W/PGE2/Aminoguanidine

iNOS inhibition changes retinal glial activation

[90]

↑

↑

↑

-

-

Impaired learning NO contributes spatial memory AD Dementia Rate 0-3 Increase reactive oxygen species and NMDAR activation in brain Impaired learning and memory nNOS/eNOS both affect memory

[82] [83] [84] [33]

[85] [86]

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(Table 1) cont.....

NOS

Species/Manipulation

iNOS

Mice/Rat iNOS KO ICV GSNO

iNOS

Mice iNOS shRNA ICV L-NIL/L-NAME

eNOS

Mice eNOS+/–

eNOS

Mice SweArc tg AD mice

eNOS

Mice eNOS+/–

eNOS

Mice eNOS KO

eNOS

NO Level

IR

Cognitive Effects/AD Pathology

↑

+

Not determined

+

Not determined

+

Early cerebral infarctions at 3-6 months, amyloid angiopathy, and cognitive impairment

Ref. [37]

↓

[91]

↓

↓

-

AD model

[92]

[93]

-

Increased cerebrovascular betaamyloid

[94]

↓

-

Increased APP, BACE1, betaamyloid in brains

[95]

Mice eNOS KO; APP/PS1/eNOS KO

↓

-

Increased tau phosphorylation, p25/p35 ratio, CDK5 activity

[96]

Cell line/Mice eNOS KO L-NAME

↓

-

eNOS

↓

-

eNOS

metabolic syndrome is associated with worse cognition only in the presence of the eNOS-786C allele

[98]

Hu. eNOS T-786C

eNOS

Rat shRNA

-

eNOS affects neuronal survival and functional

[24]

↓

↑

Increased APP, beta-amyloid, and BACE1 levels

[97]

1400W, N-[[3-(aminomethyl)phenyl]methyl]-ethanimidamide, dihydrochloride; 7-NI,7-nitroindazole; AD, Alzheimer's disease; APP23 mouse, an Alzheimer mouse model with overexpression of mutant human APP/amyloid-Beta precursor protein (Swedish mutation); BACE1, beta-secretase 1/beta-site APP cleaving enzyme 1; CDK5, cyclin-dependent kinase 5; eNOS, endothelial nitric oxide synthase; GSNO, SNitrosoglutathione; Hu., human; ICV, intracerebroventricular injection; iNOS, inducible nitric oxide synthase; IR, insulin resistance; IHC, immunohistochemistry; KO, knockout; L-NAME, N(ω)-nitro-Larginine methyl ester; L-NIL, L-N6-(1-iminoethyl)-lysine; L-NMMA, L-NG-monomethyl Arginine acetate; NMDAR, N-methyl-D-aspartate receptor; nNOS, neuronal nitric oxide synthase; PGE2,9-oxo-11α,1S-dihydroxy-prosta-5Z,13E-dien-1-oic acid; TRIM, 1-(α,α,α-trifluoro-o-tolyl)-imidazole.

The availability of NO is regulated by enzymatic activity and levels of NOS isoforms, and by levels of reactive species, such as superoxide, that can quench and reduce NO. NO is generated by three NOS isoforms expressed in tissuespecific expression patterns [99 - 101]. While nNOS (NOS1) is predominantly found in neuronal tissue, NOS2 or inducible NOS (iNOS) is upregulated in

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activated macrophages, and NOS3 (eNOS) is abundantly expressed in endothelium and also found in dendritic spines [24, 101]. eNOS and nNOS, which catalyze the Ca2+-dependent constitutive NO production, occur predominantly in blood vessels and neural tissues, respectively. NO is also rapidly elevated during inflammation and may be a primary mediator of inflammatory injury in neurodegenerative disorders such as AD [101, 102]. Thus, elevated NO levels, directly resulting from inflammatory processes in neurodegeneration, likely increase the potential for insulin resistance and accelerate pathology and cognitive impairment in AD. Interestingly, systemic and presumably brain insulin resistance and insulin secretory defects are observed when NOS activity in the brain is inhibited by intracerebroventricular (ICV) injection of L-NMMA in free-moving rats [81]. In contrast, ICV infusion of S-nitrosoglutathione (GSNO), a NO donor, in mice impaired insulin signaling in the hypothalamus and replicated the food intake pattern of obese individuals by causing nitrosation of IR and its downstream Akt [37]. Further, S-nitrosation of the IR, IRS-1, and Akt (protein kinase B) can lead to insulin resistance [103, 104]. Genetically eliminating iNOS (iNOS null) or inhibiting iNOS using iNOS targeting antisense oligonucleotides reduces hypothalamic insulin resistance and normalizes energy homeostasis [37]. Thus, selective manipulation of the brain NO system can lead to systemic and brain insulin signaling defects, but the role of NO in brain insulin resistance remains controversial. Modulation of NOS can also affect cognitive performance. Systemic administration of the NO synthase inhibitor nitro-L-arginine methyl ester (LNAME) in rats and rabbits impairs maze (spatial) learning in rats [82, 105] as well as the conditioned eye-blink response in rabbits [82]. Inhibition of NOS by 7nitroindazole, L-NAME, or N-MMA, impairs passive-avoidance and elevated pulse-maze memory performance [106], T-maze [107] and memory of shock avoidance [108]. Conversely, administration of the NO precursor L-arginine or NO donors such as sodium nitroprusside, S-nitroso-N-acetylpenicillamine (SNAP), and molsidomine improves learning and memory, including avoidance memory, maze performance, and objective recognition [108 - 111] and prevents age-related memory deficits [108]. While these data collectively suggest that chemical manipulation of the NO system can lead to systemic and brain region-specific insulin resistance and changes in cognitive performance, whether brain insulin resistance is induced by perturbing brain NOS was not explicitly demonstrated in the cognitive tests. Furthermore, effects on cognitive performance were not assessed together with insulin signaling changes. Thus, the contribution to altered cognition and

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dementia by altered NO availability caused by insulin signaling changes is still unclear. To further elucidate the inter-relationship between brain insulin signaling and cognitive performance, genetic manipulations of the NO system have been employed, and polymorphisms of the NOS have been examined. Emerging data from animal models and humans indicate that polymorphisms in the eNOS gene influence susceptibility to systemic insulin resistance and metabolic disturbances leading to T2D [112 - 115]. In contrast, eNOS T786C and E298D mutations do not increase the risk of sporadic AD [116, 117]. Similarly, NOS gene polymorphisms do not alter disease risk in most late-onset AD and Lewy body dementia cases [118]. Further analysis of the E298 allele reveals its association with a higher risk of AD in the MIRAGE African American but not Caucasian population [119]. Although these studies suggest a causative role of reduced eNOS levels and sensitivity in developing systemic insulin resistance, metabolic disturbance, and blood vessel resistance in animal models, eNOS polymorphisms in humans do not appear to affect brain insulin signaling and play a minor role in the AD progression. In addition to eNOS, iNOS activity is considerably higher in AD patients' hippocampus than in controls [120]. Together with the demonstration that decreased NO availability leads to many features of the diabetic state [121], the modulation of NO availability, including genetic or polymorphism-induced changes in the NOS system, appears to influence insulin signaling in peripheral tissues and may be an important molecular mechanism underlying the development of insulin resistance in the peripheral tissues. However, such changes in NO availability have little impact on brain insulin signaling and cognition. Moreover, the impact of altered NO availability on cognitive performance resulting from compromised brain insulin signaling remains unclear. NO has long been regarded as a part of neurotoxic insult derived from neuroinflammation driven partly by the elevation of proinflammatory cytokines, including TNFα, IL6, and IL-1β in the AD brain. Proinflammatory cytokines such as TNFα disrupt gene expression to reduce eNOS protein levels in endothelium and probably in dendritic spines by decreasing eNOS mRNA stability [122 - 125]. Thus, by reducing eNOS levels, proinflammatory cytokines such as TNFα can interfere with insulin signaling to evoke tissue-specific insulin resistance. Since AD is associated with sustained neuroinflammation with elevated proinflammatory cytokines in the brain, especially in areas important for cognition such as the hippocampus and cortical regions [8, 9, 74], the insulin resistance induced by proinflammatory cytokines may be intertwined with neurodegeneration and dementia.

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Conversely, stimulation of insulin signaling via PI3K-Akt can activate eNOS by phosphorylating the enzyme on the serine1177 residue. Insulin signaling can also potentiate adiponectin signaling to activate AMP kinase that in turn activates eNOS through phosphorylation of S1177 to promote glucose uptake in GluT4 expression neurons [101, 126]. Activation of eNOS also requires its localization in the caveolae and linkage with heat shock protein 90 (HSP90). Obesityassociated insulin resistance can decrease eNOS activity by reducing caveolin-1 in caveolae and disrupting eNOS interaction with HSP90 and insulin signaling cascade [127, 128]. Hence, elevated proinflammatory cytokines and reactive oxygen species (ROS) in the AD brain can lead to reduced eNOS phosphorylation and activation, resulting in decreased NO availability and insulin resistance in the endothelium as well as impaired vasodilation [129, 130]. Finally, superoxide rapidly reacts with NO to produce the more potent oxidant peroxynitrite, leading to endothelial dysfunction, reduced NO availability, exacerbating brain insulin resistance, and promoting AD pathogenesis. Although these data point to the possible contribution of reduced NO by the elevated proinflammatory cytokines to insulin resistance in the AD brain, the interrelationships among proinflammatory cytokines, NO system, and insulin resistance need to be more clearly defined. CONCLUDING REMARKS In conclusion, ample evidence from animal models and humans illustrates that impairments in the NO system contribute to the development of insulin resistance and associated metabolic disturbance in peripheral tissues. However, the direct contribution of reduced NO availability to brain insulin resistance is much less clear. Insulin is a critical regulator of multiple brain functions, including synaptic plasticity, learning, and memory. Importantly, impaired insulin signaling (insulin resistance) in the AD brain can occur without apparent systemic insulin signaling defects. Thus, clarifying the causal relationship of changes in the NO system to insulin signaling perturbations might increase our understanding of AD pathogenic mechanisms and identify new therapeutic approaches, such as modulating NO availability in the brain to slow the progression of the disease. CONSENT FOR PUBLICATION Not applicable. CONFLICT OF INTEREST The author declares no conflict of interest, financial or otherwise.

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ACKNOWLEDGEMENT This work was supported by the National Institute of Health grants R01 NS084965, R01 AG057658, and RF1 AG059621. REFERENCES [1]

Wilson RS, Bienias JL, Evans DA, Bennett DA. Religious Orders Study: overview and change in cognitive and motor speed. Neuropsychol Dev Cogn B Aging Neuropsychol Cogn 2004; 11(2-3): 280303. [http://dx.doi.org/10.1080/13825580490511125]

[2]

Sperling RA, Aisen PS, Beckett LA, et al. Toward defining the preclinical stages of Alzheimer’s disease: Recommendations from the National Institute on Aging-Alzheimer’s Association workgroups on diagnostic guidelines for Alzheimer’s disease. Alzheimers Dement 2011; 7(3): 280-92. [http://dx.doi.org/10.1016/j.jalz.2011.03.003] [PMID: 21514248]

[3]

Bhushan A, Fondell E, Ascherio A, Yuan C, Grodstein F, Willett W. Adherence to Mediterranean diet and subjective cognitive function in men. Eur J Epidemiol 2018; 33(2): 223-34. [http://dx.doi.org/10.1007/s10654-017-0330-3] [PMID: 29147948]

[4]

Tiwari S, Atluri V, Kaushik A, Yndart A, Nair M. Alzheimer’s disease: pathogenesis, diagnostics, and therapeutics. Int J Nanomedicine 2019; 14: 5541-54. [http://dx.doi.org/10.2147/IJN.S200490] [PMID: 31410002]

[5]

Reitz C, Brayne C, Mayeux R. Epidemiology of Alzheimer disease. Nat Rev Neurol 2011; 7(3): 13752. [http://dx.doi.org/10.1038/nrneurol.2011.2] [PMID: 21304480]

[6]

Naylor MD, Kurtzman ET, Grabowski DC, Harrington C, McClellan M, Reinhard SC. Unintended consequences of steps to cut readmissions and reform payment may threaten care of vulnerable older adults. Health Aff (Millwood) 2012; 31(7): 1623-32. [http://dx.doi.org/10.1377/hlthaff.2012.0110] [PMID: 22722702]

[7]

Liu Y, Liu F, Grundke-Iqbal I, Iqbal K, Gong CX. Deficient brain insulin signalling pathway in Alzheimer’s disease and diabetes. J Pathol 2011; 225(1): 54-62. [http://dx.doi.org/10.1002/path.2912] [PMID: 21598254]

[8]

Talbot K, Wang HY, Kazi H, et al. Demonstrated brain insulin resistance in Alzheimer’s disease patients is associated with IGF-1 resistance, IRS-1 dysregulation, and cognitive decline. J Clin Invest 2012; 122(4): 1316-38. [http://dx.doi.org/10.1172/JCI59903] [PMID: 22476197]

[9]

Wang HY, Bakshi K, Frankfurt M, et al. Reducing amyloid-related Alzheimer’s disease pathogenesis by a small molecule targeting filamin A. J Neurosci 2012; 32(29): 9773-84. [http://dx.doi.org/10.1523/JNEUROSCI.0354-12.2012] [PMID: 22815492]

[10]

Arnold SE, Arvanitakis Z, Macauley-Rambach SL, et al. Brain insulin resistance in type 2 diabetes and Alzheimer disease: concepts and conundrums. Nat Rev Neurol 2018; 14(3): 168-81. [http://dx.doi.org/10.1038/nrneurol.2017.185] [PMID: 29377010]

[11]

Dorn A, Bernstein HG, Rinne A, Hahn HJ, Ziegler M. Insulin-like immunoreactivity in the human brain. Histochemistry 1982; 74(2): 293-300. [http://dx.doi.org/10.1007/BF00495838] [PMID: 6757198]

[12]

Devaskar SU, Giddings SJ, Rajakumar PA, Carnaghi LR, Menon RK, Zahm DS. Insulin gene expression and insulin synthesis in mammalian neuronal cells. J Biol Chem 1994; 269(11): 8445-54. [http://dx.doi.org/10.1016/S0021-9258(17)37214-9] [PMID: 8132571]

[13]

Frölich L, Blum-Degen D, Bernstein HG, et al. Brain insulin and insulin receptors in aging and sporadic Alzheimer’s disease. J Neural Transm (Vienna) 1998; 105(4): 423-38.

NO and Brain Insulin Resistance

The Role of Nitric Oxide in Type 2 Diabetes 251

[http://dx.doi.org/10.1007/s007020050068] [PMID: 9720972] [14]

Steen E, Terry BM, Rivera EJ, et al. Impaired insulin and insulin-like growth factor expression and signaling mechanisms in Alzheimer’s disease--is this type 3 diabetes? J Alzheimers Dis 2005; 7(1): 63-80. [http://dx.doi.org/10.3233/JAD-2005-7107] [PMID: 15750215]

[15]

Mehran AE, Templeman NM, Brigidi GS, et al. Hyperinsulinemia drives diet-induced obesity independently of brain insulin production. Cell Metab 2012; 16(6): 723-37. [http://dx.doi.org/10.1016/j.cmet.2012.10.019] [PMID: 23217255]

[16]

Marks JL, Porte D Jr, Stahl WL, Baskin DG. Localization of insulin receptor mRNA in rat brain by in situ hybridization. Endocrinology 1990; 127(6): 3234-6. [http://dx.doi.org/10.1210/endo-127-6-3234] [PMID: 2249648]

[17]

Unger J, Livingston J, Moss A. Insulin receptors in the central nervous system: Localization, signalling mechanisms and functional aspects. Prog Neurobiol 1991; 36(5): 343-62. [http://dx.doi.org/10.1016/0301-0082(91)90015-S] [PMID: 1887067]

[18]

Adamo M, Raizada MK, LeRoith D. Insulin and insulin-like growth factor receptors in the nervous system. Mol Neurobiol 1989; 3(1-2): 71-100. [http://dx.doi.org/10.1007/BF02935589] [PMID: 2553069]

[19]

Torres-Aleman I. Toward a comprehensive neurobiology of IGF-I. Dev Neurobiol 2010; 70(5): 38496. [PMID: 20186710]

[20]

Dyer AH, Vahdatpour C, Sanfeliu A, Tropea D. The role of Insulin-Like Growth Factor 1 (IGF-1) in brain development, maturation and neuroplasticity. Neuroscience 2016; 325: 89-99. [http://dx.doi.org/10.1016/j.neuroscience.2016.03.056] [PMID: 27038749]

[21]

Zeng ZH, Zhang ZH, Luo BH, He WK, Liang LY, He CC, et al. The functional changes of the perivascular adipose tissue in spontaneously hypertensive rats and the effects of atorvastatin therapy. 2009. [http://dx.doi.org/10.1080/10641960902977916]

[22]

Rafikov R, Fonseca FV, Kumar S, et al. eNOS activation and NO function: Structural motifs responsible for the posttranslational control of endothelial nitric oxide synthase activity. J Endocrinol 2011; 210(3): 271-84. [http://dx.doi.org/10.1530/JOE-11-0083] [PMID: 21642378]

[23]

Schilling TM, Ferreira de Sá DS, Westerhausen R, et al. Intranasal insulin increases regional cerebral blood flow in the insular cortex in men independently of cortisol manipulation. Hum Brain Mapp 2014; 35(5): 1944-56. [http://dx.doi.org/10.1002/hbm.22304] [PMID: 23907764]

[24]

Caviedes A, Varas-Godoy M, Lafourcade C, et al. Endothelial Nitric Oxide Synthase Is Present in Dendritic Spines of Neurons in Primary Cultures. Front Cell Neurosci 2017; 11: 180. [http://dx.doi.org/10.3389/fncel.2017.00180] [PMID: 28725180]

[25]

Srivastava K, Bath PMW, Bayraktutan U. Current therapeutic strategies to mitigate the eNOS dysfunction in ischaemic stroke. Cell Mol Neurobiol 2012; 32(3): 319-36. [http://dx.doi.org/10.1007/s10571-011-9777-z] [PMID: 22198555]

[26]

Van Der Heide LP, Kamal A, Artola A, Gispen WH, Ramakers GMJ. Insulin modulates hippocampal activity-dependent synaptic plasticity in a N-methyl-d-aspartate receptor and phosphatidyl-inositol3-kinase-dependent manner. J Neurochem 2005; 94(4): 1158-66. [http://dx.doi.org/10.1111/j.1471-4159.2005.03269.x] [PMID: 16092951]

[27]

De Felice FG. Alzheimer’s disease and insulin resistance: translating basic science into clinical applications. J Clin Invest 2013; 123(2): 531-9. [http://dx.doi.org/10.1172/JCI64595] [PMID: 23485579]

252 The Role of Nitric Oxide in Type 2 Diabetes

Pei et al.

[28]

Fadel JR, Reagan LP. Stop signs in hippocampal insulin signaling: the role of insulin resistance in structural, functional and behavioral deficits. Curr Opin Behav Sci 2016; 9: 47-54. [http://dx.doi.org/10.1016/j.cobeha.2015.12.004] [PMID: 26955646]

[29]

Gralle M. The neuronal insulin receptor in its environment. J Neurochem 2017; 140(3): 359-67. [http://dx.doi.org/10.1111/jnc.13909] [PMID: 27889917]

[30]

Chiu SL, Chen CM, Cline HT. Insulin receptor signaling regulates synapse number, dendritic plasticity, and circuit function in vivo. Neuron 2008; 58(5): 708-19. [http://dx.doi.org/10.1016/j.neuron.2008.04.014] [PMID: 18549783]

[31]

Crosbie R, Straub V, Yun H-Y, et al. mdx muscle pathology is independent of nNOS perturbation. Hum Mol Genet 1998; 7(5): 823-9. [http://dx.doi.org/10.1093/hmg/7.5.823] [PMID: 9536086]

[32]

Rameau GA, Tukey DS, Garcin-Hosfield ED, et al. Biphasic coupling of neuronal nitric oxide synthase phosphorylation to the NMDA receptor regulates AMPA receptor trafficking and neuronal cell death. J Neurosci 2007; 27(13): 3445-55. [http://dx.doi.org/10.1523/JNEUROSCI.4799-06.2007] [PMID: 17392461]

[33]

Girouard H, Wang G, Gallo EF, et al. NMDA receptor activation increases free radical production through nitric oxide and NOX2. J Neurosci 2009; 29(8): 2545-52. [http://dx.doi.org/10.1523/JNEUROSCI.0133-09.2009] [PMID: 19244529]

[34]

Wang H, Wang AX, Liu Z, Barrett EJ. Insulin signaling stimulates insulin transport by bovine aortic endothelial cells. Diabetes 2008; 57(3): 540-7. [http://dx.doi.org/10.2337/db07-0967] [PMID: 17977956]

[35]

Hsu PY, Calviello L, Wu HYL, et al. Super-resolution ribosome profiling reveals unannotated translation events in Arabidopsis. Proc Natl Acad Sci USA 2016; 113(45): E7126-35. [http://dx.doi.org/10.1073/pnas.1614788113] [PMID: 27791167]

[36]

Hsu MF, Meng TC. Enhancement of insulin responsiveness by nitric oxide-mediated inactivation of protein-tyrosine phosphatases. J Biol Chem 2010; 285(11): 7919-28. [http://dx.doi.org/10.1074/jbc.M109.057513] [PMID: 20064934]

[37]

Katashima CK, Silva VRR, Lenhare L, Marin RM, Carvalheira JBC. iNOS promotes hypothalamic insulin resistance associated with deregulation of energy balance and obesity in rodents. Sci Rep 2017; 7(1): 9265. [http://dx.doi.org/10.1038/s41598-017-08920-z] [PMID: 28835706]

[38]

Krug R, Benedict C, Born J, Hallschmid M. Comparable sensitivity of postmenopausal and young women to the effects of intranasal insulin on food intake and working memory. J Clin Endocrinol Metab 2010; 95(12): E468-72. [http://dx.doi.org/10.1210/jc.2010-0744] [PMID: 20719831]

[39]

Benedict C, Hallschmid M, Hatke A, et al. Intranasal insulin improves memory in humans. Psychoneuroendocrinology 2004; 29(10): 1326-34. [http://dx.doi.org/10.1016/j.psyneuen.2004.04.003] [PMID: 15288712]

[40]

Benedict C, Hallschmid M, Schmitz K, et al. Intranasal insulin improves memory in humans: superiority of insulin aspart. Neuropsychopharmacology 2007; 32(1): 239-43. [http://dx.doi.org/10.1038/sj.npp.1301193] [PMID: 16936707]

[41]

Reger MA, Watson GS, Green PS, et al. Intranasal insulin improves cognition and modulates -amyloid in early AD. Neurology 2008; 70(6): 440-8. [http://dx.doi.org/10.1212/01.WNL.0000265401.62434.36] [PMID: 17942819]

[42]

Marks DR, Tucker K, Cavallin MA, Mast TG, Fadool DA. Awake intranasal insulin delivery modifies protein complexes and alters memory, anxiety, and olfactory behaviors. J Neurosci 2009; 29(20): 6734-51. [http://dx.doi.org/10.1523/JNEUROSCI.1350-09.2009] [PMID: 19458242]

NO and Brain Insulin Resistance

The Role of Nitric Oxide in Type 2 Diabetes 253

[43]

Scherer T, Lindtner C, O’Hare J, et al. Insulin Regulates Hepatic Triglyceride Secretion and Lipid Content via Signaling in the Brain. Diabetes 2016; 65(6): 1511-20. [http://dx.doi.org/10.2337/db15-1552] [PMID: 26861781]

[44]

Adzovic L, Lynn AE, D’Angelo HM, et al. Insulin improves memory and reduces chronic neuroinflammation in the hippocampus of young but not aged brains. J Neuroinflammation 2015; 12(1): 63. [http://dx.doi.org/10.1186/s12974-015-0282-z] [PMID: 25889938]

[45]

Park C, Seeley R, Craft S, Woods S. Intracerebroventricular insulin enhances memory in a passiveavoidance task. Physiol Behav 2000; 68(4): 509-14. [http://dx.doi.org/10.1016/S0031-9384(99)00220-6] [PMID: 10713291]

[46]

Moosavi M, Naghdi N, Maghsoudi N, Zahedi Asl S. The effect of intrahippocampal insulin microinjection on spatial learning and memory. Horm Behav 2006; 50(5): 748-52. [http://dx.doi.org/10.1016/j.yhbeh.2006.06.025] [PMID: 16890939]

[47]

Moosavi M, Naghdi N, Choopani S. Intra CA1 insulin microinjection improves memory consolidation and retrieval. Peptides 2007; 28(5): 1029-34. [http://dx.doi.org/10.1016/j.peptides.2007.02.010] [PMID: 17360072]

[48]

Moosavi M, Naghdi N, Maghsoudi N, Zahediasl S. Insulin protects against stress-induced impairments in water maze performance. Behav Brain Res 2007; 176(2): 230-6. [http://dx.doi.org/10.1016/j.bbr.2006.10.011] [PMID: 17116337]

[49]

Zhao WQ, Chen H, Quon MJ, Alkon DL. Insulin and the insulin receptor in experimental models of learning and memory. Eur J Pharmacol 2004; 490(1-3): 71-81. [http://dx.doi.org/10.1016/j.ejphar.2004.02.045] [PMID: 15094074]

[50]

Grillo CA, Piroli GG, Lawrence RC, et al. Hippocampal Insulin Resistance Impairs Spatial Learning and Synaptic Plasticity. Diabetes 2015; 64(11): 3927-36. [http://dx.doi.org/10.2337/db15-0596] [PMID: 26216852]

[51]

Dou JT, Chen M, Dufour F, Alkon DL, Zhao WQ. Insulin receptor signaling in long-term memory consolidation following spatial learning. Learn Mem 2005; 12(6): 646-55. [http://dx.doi.org/10.1101/lm.88005] [PMID: 16287721]

[52]

Schubert M, Gautam D, Surjo D, et al. Role for neuronal insulin resistance in neurodegenerative diseases. Proc Natl Acad Sci USA 2004; 101(9): 3100-5. [http://dx.doi.org/10.1073/pnas.0308724101] [PMID: 14981233]

[53]

Kern W, Born J, Schreiber H, Fehm HL. Central nervous system effects of intranasally administered insulin during euglycemia in men. Diabetes 1999; 48(3): 557-63. [http://dx.doi.org/10.2337/diabetes.48.3.557] [PMID: 10078556]

[54]

Hallschmid M, Schultes B, Marshall L, et al. Transcortical direct current potential shift reflects immediate signaling of systemic insulin to the human brain. Diabetes 2004; 53(9): 2202-8. [http://dx.doi.org/10.2337/diabetes.53.9.2202] [PMID: 15331528]

[55]

Zhang H, Zhang T, Li S, et al. Long-term Impact of Childhood Adiposity on Adult Metabolic Syndrome Is Modified by Insulin Resistance: The Bogalusa Heart Study. Sci Rep 2015; 5(1): 17885. [http://dx.doi.org/10.1038/srep17885] [PMID: 26640243]

[56]

Stingl KT, Kullmann S, Guthoff M, Heni M, Fritsche A, Preissl H. Insulin modulation of magnetoencephalographic resting state dynamics in lean and obese subjects. Front Syst Neurosci 2010; 4: 157. [http://dx.doi.org/10.3389/fnsys.2010.00157] [PMID: 21191479]

[57]

Craft S, Asthana S, Newcomer JW, et al. Enhancement of memory in Alzheimer disease with insulin and somatostatin, but not glucose. Arch Gen Psychiatry 1999; 56(12): 1135-40. [http://dx.doi.org/10.1001/archpsyc.56.12.1135] [PMID: 10591291]

254 The Role of Nitric Oxide in Type 2 Diabetes

Pei et al.

[58]

Craft S, Baker LD, Montine TJ, et al. Intranasal insulin therapy for Alzheimer disease and amnestic mild cognitive impairment: a pilot clinical trial. Arch Neurol 2012; 69(1): 29-38. [http://dx.doi.org/10.1001/archneurol.2011.233] [PMID: 21911655]

[59]

Reger MA, Watson GS, Frey WH II, et al. Effects of intranasal insulin on cognition in memoryimpaired older adults: Modulation by APOE genotype. Neurobiol Aging 2006; 27(3): 451-8. [http://dx.doi.org/10.1016/j.neurobiolaging.2005.03.016] [PMID: 15964100]

[60]

Hallschmid M, Higgs S, Thienel M, Ott V, Lehnert H. Postprandial administration of intranasal insulin intensifies satiety and reduces intake of palatable snacks in women. Diabetes 2012; 61(4): 782-9. [http://dx.doi.org/10.2337/db11-1390] [PMID: 22344561]

[61]

Novak V, Milberg W, Hao Y, et al. Enhancement of vasoreactivity and cognition by intranasal insulin in type 2 diabetes. Diabetes Care 2014; 37(3): 751-9. [http://dx.doi.org/10.2337/dc13-1672] [PMID: 24101698]

[62]

Brunner Y, Kofoet A, Benedict C. Central Insulin Administration Improves Odor-Cued Reactivation of Spatial Memory in Young Men (vol 100, pg 212, 2015). J Clin Endocrinol Metab 2016; 101(10): 3863.

[63]

Claxton A, Baker LD, Hanson A, et al. Long-acting intranasal insulin detemir improves cognition for adults with mild cognitive impairment or early-stage Alzheimer’s disease dementia. J Alzheimers Dis 2015; 44(3): 897-906. [http://dx.doi.org/10.3233/JAD-141791] [PMID: 25374101]

[64]

Craft S, Raman R, Chow TW, et al. Safety, Efficacy, and Feasibility of Intranasal Insulin for the Treatment of Mild Cognitive Impairment and Alzheimer Disease Dementia. JAMA Neurol 2020; 77(9): 1099-109. [http://dx.doi.org/10.1001/jamaneurol.2020.1840] [PMID: 32568367]

[65]

Kapogiannis D, Mattson MP. Disrupted energy metabolism and neuronal circuit dysfunction in cognitive impairment and Alzheimer’s disease. Lancet Neurol 2011; 10(2): 187-98. [http://dx.doi.org/10.1016/S1474-4422(10)70277-5] [PMID: 21147038]

[66]

Correia SC, Santos RX, Carvalho C, et al. Insulin signaling, glucose metabolism and mitochondria: Major players in Alzheimer’s disease and diabetes interrelation. Brain Res 2012; 1441: 64-78. [http://dx.doi.org/10.1016/j.brainres.2011.12.063] [PMID: 22290178]

[67]

Ruiz HH, Chi T, Shin AC, et al. Increased susceptibility to metabolic dysregulation in a mouse model of Alzheimer’s disease is associated with impaired hypothalamic insulin signaling and elevated BCAA levels. Alzheimers Dement 2016; 12(8): 851-61. [http://dx.doi.org/10.1016/j.jalz.2016.01.008] [PMID: 26928090]

[68]

Stanley M, Macauley SL, Holtzman DM. Changes in insulin and insulin signaling in Alzheimer’s disease: cause or consequence? J Exp Med 2016; 213(8): 1375-85. [http://dx.doi.org/10.1084/jem.20160493] [PMID: 27432942]

[69]

Tumminia A, Vinciguerra F, Parisi M, Frittitta L. Type 2 Diabetes Mellitus and Alzheimer’s Disease: Role of Insulin Signalling and Therapeutic Implications. Int J Mol Sci 2018; 19(11): 3306. [http://dx.doi.org/10.3390/ijms19113306] [PMID: 30355995]

[70]

De La Monte SM. Insulin resistance and Alzheimer’s disease. BMB Rep 2009; 42(8): 475-81. [http://dx.doi.org/10.5483/BMBRep.2009.42.8.475] [PMID: 19712582]

[71]

Rivera EJ, Goldin A, Fulmer N, Tavares R, Wands JR, de la Monte SM. Insulin and insulin-like growth factor expression and function deteriorate with progression of Alzheimer’s disease: Link to brain reductions in acetylcholine. J Alzheimers Dis 2005; 8(3): 247-68. [http://dx.doi.org/10.3233/JAD-2005-8304] [PMID: 16340083]

[72]

Moloney AM, Griffin RJ, Timmons S, O’Connor R, Ravid R, O’Neill C. Defects in IGF-1 receptor, insulin receptor and IRS-1/2 in Alzheimer’s disease indicate possible resistance to IGF-1 and insulin signalling. Neurobiol Aging 2010; 31(2): 224-43.

NO and Brain Insulin Resistance

The Role of Nitric Oxide in Type 2 Diabetes 255

[http://dx.doi.org/10.1016/j.neurobiolaging.2008.04.002] [PMID: 18479783] [73]

Folch J, Olloquequi J, Ettcheto M, et al. The Involvement of Peripheral and Brain Insulin Resistance in Late Onset Alzheimer’s Dementia. Front Aging Neurosci 2019; 11: 236. [http://dx.doi.org/10.3389/fnagi.2019.00236] [PMID: 31551756]

[74]

Wang Q, Holmes MV, Davey Smith G, Ala-Korpela M. Genetic Support for a Causal Role of Insulin Resistance on Circulating Branched-Chain Amino Acids and Inflammation. Diabetes Care 2017; 40(12): 1779-86. [http://dx.doi.org/10.2337/dc17-1642] [PMID: 29046328]

[75]

Kellar D, Craft S. Brain insulin resistance in Alzheimer’s disease and related disorders: mechanisms and therapeutic approaches. Lancet Neurol 2020; 19(9): 758-66. [http://dx.doi.org/10.1016/S1474-4422(20)30231-3] [PMID: 32730766]

[76]

Crews L, Masliah E. Molecular mechanisms of neurodegeneration in Alzheimer’s disease. Hum Mol Genet 2010; 19(R1): R12-20. [http://dx.doi.org/10.1093/hmg/ddq160] [PMID: 20413653]

[77]

Grothe MJ, Sepulcre J, Gonzalez-Escamilla G, et al. Molecular properties underlying regional vulnerability to Alzheimer’s disease pathology. Brain 2018; 141(9): 2755-71. [http://dx.doi.org/10.1093/brain/awy189] [PMID: 30016411]

[78]

Lüth HJ, Münch G, Arendt T. Aberrant expression of NOS isoforms in Alzheimer’s disease is structurally related to nitrotyrosine formation. Brain Res 2002; 953(1-2): 135-43. [http://dx.doi.org/10.1016/S0006-8993(02)03280-8] [PMID: 12384247]

[79]

Lüth HJ, Holzer M, Gärtner U, Staufenbiel M, Arendt T. Expression of endothelial and inducible NOS-isoforms is increased in Alzheimer’s disease, in APP23 transgenic mice and after experimental brain lesion in rat: evidence for an induction by amyloid pathology. Brain Res 2001; 913(1): 57-67. [http://dx.doi.org/10.1016/S0006-8993(01)02758-5] [PMID: 11532247]

[80]

Shankar RR, Wu Y, Shen HQ, Zhu JS, Baron AD. Mice with gene disruption of both endothelial and neuronal nitric oxide synthase exhibit insulin resistance. Diabetes 2000; 49(5): 684-7. [http://dx.doi.org/10.2337/diabetes.49.5.684] [PMID: 10905473]

[81]

Shankar R, Zhu JS, Ladd B, Henry D, Shen HQ, Baron AD. Central nervous system nitric oxide synthase activity regulates insulin secretion and insulin action. J Clin Invest 1998; 102(7): 1403-12. [http://dx.doi.org/10.1172/JCI3030] [PMID: 9769333]

[82]

Chapman PF, Atkins CM, Allen MT, Haley JE, Steinmetz JE. Inhibition of nitric oxide synthesis impairs two different forms of learning. Neuroreport 1992; 3(7): 567-70. [http://dx.doi.org/10.1097/00001756-199207000-00005] [PMID: 1421108]

[83]

Zou LB, Yamada K, Tanaka T, Kameyama T, Nabeshima T. Nitric oxide synthase inhibitors impair reference memory formation in a radial arm maze task in rats. Neuropharmacology 1998; 37(3): 32330. [http://dx.doi.org/10.1016/S0028-3908(98)00042-2] [PMID: 9681930]

[84]

Fernández-Vizarra P, Fernández AP, Castro-Blanco S, et al. Expression of nitric oxide system in clinically evaluated cases of Alzheimer’s disease. Neurobiol Dis 2004; 15(2): 287-305. [http://dx.doi.org/10.1016/j.nbd.2003.10.010] [PMID: 15006699]

[85]

Yildiz Akar F, Ulak G, Tanyeri P, Erden F, Utkan T, Gacar N. 7-Nitroindazole, a neuronal nitric oxide synthase inhibitor, impairs passive-avoidance and elevated plus-maze memory performance in rats. Pharmacol Biochem Behav 2007; 87(4): 434-43. [http://dx.doi.org/10.1016/j.pbb.2007.05.019] [PMID: 17602730]

[86]

Mutlu O, Ulak G, Belzung C. Effects of nitric oxide synthase inhibitors 1-(2-trifluoromethylphenyl) imidazole (TRIM) and 7-nitroindazole (7-NI) on learning and memory in mice. Fundam Clin Pharmacol 2011; 25(3): 368-77. [http://dx.doi.org/10.1111/j.1472-8206.2010.00851.x] [PMID: 20608991]

256 The Role of Nitric Oxide in Type 2 Diabetes

Pei et al.

[87]

Hölscher C, McGlinchey L, Anwyl R, Rowan MJ. 7-Nitro indazole, a selective neuronal nitric oxide synthase inhibitor in vivo, impairs spatial learning in the rat. Learn Mem 1996; 2(6): 267-78. [http://dx.doi.org/10.1101/lm.2.6.267] [PMID: 10467579]

[88]

Akar FY, Celikyurt IK, Ulak G, Mutlu O. Effects of L-arginine on 7-nitroindazole-induced reference and working memory performance of rats. Pharmacology 2009; 84(4): 211-8. [http://dx.doi.org/10.1159/000235997] [PMID: 19738400]

[89]

Rodrigo J, Fernández-Vizarra P, Castro-Blanco S, et al. Nitric oxide in the cerebral cortex of amyloidprecursor protein (SW) Tg2576 transgenic mice. Neuroscience 2004; 128(1): 73-89. [http://dx.doi.org/10.1016/j.neuroscience.2004.06.030] [PMID: 15450355]

[90]

Mishra A, Newman EA. Inhibition of inducible nitric oxide synthase reverses the loss of functional hyperemia in diabetic retinopathy. Glia 2010; 58(16): 1996-2004. [http://dx.doi.org/10.1002/glia.21068] [PMID: 20830810]

[91]

Lee CH, Kim HJ, Lee YS, et al. Hypothalamic Macrophage Inducible Nitric Oxide Synthase Mediates Obesity-Associated Hypothalamic Inflammation. Cell Rep 2018; 25(4): 934-946.e5. [http://dx.doi.org/10.1016/j.celrep.2018.09.070] [PMID: 30355499]

[92]

Tan XL, Xue YQ, Ma T, et al. Partial eNOS deficiency causes spontaneous thrombotic cerebral infarction, amyloid angiopathy and cognitive impairment. Mol Neurodegener 2015; 10(1): 24. [http://dx.doi.org/10.1186/s13024-015-0020-0] [PMID: 26104027]

[93]

Merlini M, Shi Y, Keller S, et al. Reduced nitric oxide bioavailability mediates cerebroarterial dysfunction independent of cerebral amyloid angiopathy in a mouse model of Alzheimer’s disease. Am J Physiol Heart Circ Physiol 2017; 312(2): H232-8. [http://dx.doi.org/10.1152/ajpheart.00607.2016] [PMID: 27836896]

[94]

Austin SA, Katusic ZS. Partial loss of endothelial nitric oxide leads to increased cerebrovascular beta amyloid. J Cereb Blood Flow Metab 2020; 40(2): 392-403. [http://dx.doi.org/10.1177/0271678X18822474] [PMID: 30614363]

[95]

Austin SA, Santhanam AV, Hinton DJ, Choi DS, Katusic ZS. Endothelial nitric oxide deficiency promotes Alzheimer’s disease pathology. J Neurochem 2013; 127(5): 691-700. [http://dx.doi.org/10.1111/jnc.12334] [PMID: 23745722]

[96]

Austin SA, Katusic ZS. Loss of Endothelial Nitric Oxide Synthase Promotes p25 Generation and Tau Phosphorylation in a Murine Model of Alzheimer’s Disease. Circ Res 2016; 119(10): 1128-34. [http://dx.doi.org/10.1161/CIRCRESAHA.116.309686] [PMID: 27601478]

[97]

Austin SA, Santhanam AV, Katusic ZS. Endothelial nitric oxide modulates expression and processing of amyloid precursor protein. Circ Res 2010; 107(12): 1498-502. [http://dx.doi.org/10.1161/CIRCRESAHA.110.233080] [PMID: 21127294]

[98]

Kraal AZ, Moll AC, Arvanitis NR, et al. Metabolic syndrome is negatively associated with cognition among endothelial nitric oxide synthase (eNOS)- 786C carriers in schizophrenia-spectrum disorders. J Psychiatr Res 2019; 117: 142-7. [http://dx.doi.org/10.1016/j.jpsychires.2019.07.006] [PMID: 31421598]

[99]

Iyengar R, Stuehr DJ, Marletta MA. Macrophage synthesis of nitrite, nitrate, and N-nitrosamines: precursors and role of the respiratory burst. Proc Natl Acad Sci USA 1987; 84(18): 6369-73. [http://dx.doi.org/10.1073/pnas.84.18.6369] [PMID: 2819872]

[100] Palmer RMJ, Ashton DS, Moncada S. Vascular endothelial cells synthesize nitric oxide from Larginine. Nature 1988; 333(6174): 664-6. [http://dx.doi.org/10.1038/333664a0] [PMID: 3131684] [101] Mattila JT, Thomas AC. Nitric oxide synthase: non-canonical expression patterns. Front Immunol 2014; 5: 478. [http://dx.doi.org/10.3389/fimmu.2014.00478] [PMID: 25346730]

NO and Brain Insulin Resistance

The Role of Nitric Oxide in Type 2 Diabetes 257

[102] Strijbos PJLM. Nitric oxide in cerebral ischemic neurodegeneration and excitotoxicity. Crit Rev Neurobiol 1998; 12(3): 223-43. [http://dx.doi.org/10.1615/CritRevNeurobiol.v12.i3.40] [PMID: 9847056] [103] Carvalho-Filho MA, Ueno M, Hirabara SM, et al. S-nitrosation of the insulin receptor, insulin receptor substrate 1, and protein kinase B/Akt: a novel mechanism of insulin resistance. Diabetes 2005; 54(4): 959-67. [http://dx.doi.org/10.2337/diabetes.54.4.959] [PMID: 15793233] [104] Yasukawa T, Tokunaga E, Ota H, Sugita H, Martyn JAJ, Kaneki M. S-nitrosylation-dependent inactivation of Akt/protein kinase B in insulin resistance. J Biol Chem 2005; 280(9): 7511-8. [http://dx.doi.org/10.1074/jbc.M411871200] [PMID: 15632167] [105] Qiang M, Xie J, Wang H, Qiao J. Effect of nitric oxide synthesis inhibition on c-Fos expression in hippocampus and cerebral cortex following two forms of learning in rats. Behav Pharmacol 1999; 10(2): 215-22. [http://dx.doi.org/10.1097/00008877-199903000-00010] [PMID: 10780834] [106] Yildiz A, Guleryuz S, Ankerst DP, Öngür D, Renshaw PF. Protein kinase C inhibition in the treatment of mania: a double-blind, placebo-controlled trial of tamoxifen. Arch Gen Psychiatry 2008; 65(3): 255-63. [http://dx.doi.org/10.1001/archgenpsychiatry.2007.43] [PMID: 18316672] [107] Ingram RE, Miranda J, Segal ZV. Cognitive vulnerability to depression. New York, NY, US: Guilford Press 1998.xiii, 330-xiii. [108] Paul V, Reddy L, Ekambaram P. Prevention of picrotoxin convulsions-induced learning and memory impairment by nitric oxide increasing dose of l-arginine in rats. Pharmacol Biochem Behav 2003; 75(2): 329-34. [http://dx.doi.org/10.1016/S0091-3057(03)00084-4] [PMID: 12873623] [109] Bernabeu R, de Stein ML, Fin C, Izquierdo I, Medina JH. Role of hippocampal NO in the acquisition and consolidation of inhibitory avoidance learning. Neuroreport 1995; 6(11): 1498-500. [http://dx.doi.org/10.1097/00001756-199507310-00008] [PMID: 7579133] [110] Paul V, Reddy L, Ekambaram P. A reversal by L-arginine and sodium nitroprusside of ageing-induced memory impairment in rats by increasing nitric oxide concentration in the hippocampus. Indian J Physiol Pharmacol 2005; 49(2): 179-86. [PMID: 16170986] [111] Pitsikas N, Rigamonti AE, Cella SG, Sakellaridis N, Muller EE. The nitric oxide donor molsidomine antagonizes age-related memory deficits in the rat. Neurobiol Aging 2005; 26(2): 259-64. [http://dx.doi.org/10.1016/j.neurobiolaging.2004.04.003] [PMID: 15582753] [112] Monti LD, Barlassina C, Citterio L, et al. Endothelial nitric oxide synthase polymorphisms are associated with type 2 diabetes and the insulin resistance syndrome. Diabetes 2003; 52(5): 1270-5. [http://dx.doi.org/10.2337/diabetes.52.5.1270] [PMID: 12716763] [113] Fernández-Hernando C, Ackah E, Yu J, et al. Loss of Akt1 leads to severe atherosclerosis and occlusive coronary artery disease. Cell Metab 2007; 6(6): 446-57. [http://dx.doi.org/10.1016/j.cmet.2007.10.007] [PMID: 18054314] [114] González-Sánchez JL, Martínez-Larrad MT, Sáez ME, Zabena C, Martínez-Calatrava MJ, SerranoRíos M. Endothelial nitric oxide synthase haplotypes are associated with features of metabolic syndrome. Clin Chem 2007; 53(1): 91-7. [http://dx.doi.org/10.1373/clinchem.2006.075176] [PMID: 17110473] [115] Kang MK, Kim OJ, Jeon YJ, et al. Interplay between polymorphisms in the endothelial nitric oxide synthase (eNOS) gene and metabolic syndrome in determining the risk of ischemic stroke in Koreans. J Neurol Sci 2014; 344(1-2): 55-9. [http://dx.doi.org/10.1016/j.jns.2014.06.020] [PMID: 24976532]

258 The Role of Nitric Oxide in Type 2 Diabetes

Pei et al.

[116] Venturelli E, Galimberti D, Lovati C, et al. The T-786C NOS3 polymorphism in Alzheimer’s disease: Association and influence on gene expression. Neurosci Lett 2005; 382(3): 300-3. [http://dx.doi.org/10.1016/j.neulet.2005.03.032] [PMID: 15925107] [117] Sánchez-Guerra M, Combarros O, Alvarez-Arcaya A, et al. The Glu298Asp polymorphism in the NOS3 gene is not associated with sporadic Alzheimer’s disease. J Neurol Neurosurg Psychiatry 2001; 70(4): 566-7. [http://dx.doi.org/10.1136/jnnp.70.4.566] [PMID: 11300106] [118] Singleton A, Gibson AM, McKeith IG, Ballard CG, Edwardson JA, Morris CM. Nitric oxide synthase gene polymorphisms in Alzheimer’s disease and dementia with Lewy bodies. Neurosci Lett 2001; 303(1): 33-6. [http://dx.doi.org/10.1016/S0304-3940(01)01694-9] [PMID: 11297817] [119] Akomolafe A, Lunetta KL, Erlich PM, et al. Genetic association between endothelial nitric oxide synthase and Alzheimer disease. Clin Genet 2006; 70(1): 49-56. [http://dx.doi.org/10.1111/j.1399-0004.2006.00638.x] [PMID: 16813604] [120] Youn H, Ji I, Ji HP, Markesbery WR, Ji TH. Under-expression of Kalirin-7 Increases iNOS activity in cultured cells and correlates to elevated iNOS activity in Alzheimer’s disease hippocampus. J Alzheimers Dis 2007; 12(3): 271-81. [http://dx.doi.org/10.3233/JAD-2007-12309] [PMID: 18057561] [121] Carlström M, Larsen FJ, Nyström T, et al. Dietary inorganic nitrate reverses features of metabolic syndrome in endothelial nitric oxide synthase-deficient mice. Proc Natl Acad Sci USA 2010; 107(41): 17716-20. [http://dx.doi.org/10.1073/pnas.1008872107] [PMID: 20876122] [122] Alonso J, Sánchez de Miguel L, Montón M, Casado S, López-Farré A. Endothelial cytosolic proteins bind to the 3′ untranslated region of endothelial nitric oxide synthase mRNA: regulation by tumor necrosis factor alpha. Mol Cell Biol 1997; 17(10): 5719-26. [http://dx.doi.org/10.1128/MCB.17.10.5719] [PMID: 9315630] [123] Lai P, Mohamed F, Monge J-C, Stewart DJ. Downregulation of eNOS mRNA expression by TNFα: identification and functional characterization of RNA–protein interactions in the 3′UTR. Cardiovasc Res 2003; 59(1): 160-8. [http://dx.doi.org/10.1016/S0008-6363(03)00296-7] [PMID: 12829187] [124] Neumann P, Gertzberg N, Johnson A. TNF-α induces a decrease in eNOS promoter activity. Am J Physiol Lung Cell Mol Physiol 2004; 286(2): L452-9. [http://dx.doi.org/10.1152/ajplung.00378.2002] [PMID: 14555463] [125] Anderson HDI, Rahmutula D, Gardner DG. Tumor necrosis factor-α inhibits endothelial nitric-oxide synthase gene promoter activity in bovine aortic endothelial cells. J Biol Chem 2004; 279(2): 963-9. [http://dx.doi.org/10.1074/jbc.M309552200] [PMID: 14581470] [126] Zhao Y, Zhu J, Liang H, et al. Kang Le Xin reduces blood pressure through inducing endothelialdependent vasodilation by activating the AMPK-eNOS pathway. Front Pharmacol 2020; 10: 1548. [http://dx.doi.org/10.3389/fphar.2019.01548] [PMID: 32038237] [127] Michel T, Feron O. Nitric oxide synthases: which, where, how, and why? J Clin Invest 1997; 100(9): 2146-52. [http://dx.doi.org/10.1172/JCI119750] [PMID: 9410890] [128] Zhang QJ, Holland WL, Wilson L, et al. Ceramide mediates vascular dysfunction in diet-induced obesity by PP2A-mediated dephosphorylation of the eNOS-Akt complex. Diabetes 2012; 61(7): 184859. [http://dx.doi.org/10.2337/db11-1399] [PMID: 22586587] [129] Kim J, Formoso G, Li Y, et al. Epigallocatechin gallate, a green tea polyphenol, mediates NOdependent vasodilation using signaling pathways in vascular endothelium requiring reactive oxygen

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species and Fyn. J Biol Chem 2007; 282(18): 13736-45. [http://dx.doi.org/10.1074/jbc.M609725200] [PMID: 17363366] [130] Du X, Edelstein D, Obici S, Higham N, Zou MH, Brownlee M. Insulin resistance reduces arterial prostacyclin synthase and eNOS activities by increasing endothelial fatty acid oxidation. J Clin Invest 2006; 116(4): 1071-80. [http://dx.doi.org/10.1172/JCI23354] [PMID: 16528409]

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CHAPTER 12

Arginine, Nitric Oxide, and Type 2 Diabetes Parvin Mirmiran1,2, Zahra Bahadoran1, Khosrow Kashfi3 and Asghar Ghasemi4,* Nutrition and Endocrine Research Center, Research Institute for Endocrine Sciences, Shahid Beheshti University of Medical Sciences, Tehran, Iran 2 Department of Clinical Nutrition and Human Dietetics, National Nutrition and Food Technology Research Institute, Shahid Beheshti University of Medical Sciences, Tehran, Iran 3 Department of Molecular, Cellular and Biomedical Sciences, Sophie Davis School of Biomedical Education, City University of New York School of Medicine, New York, NY 10031, USA 4 Endocrine Physiology Research Center, Research Institute for Endocrine Sciences, Shahid Beheshti University of Medical Sciences, Tehran, Iran 1

Abstract: L Arginine (Arg), a semi-essential essential amino acid, has received significant research interest over the last two decades as nitric oxide (NO) precursor. Arg is widely used as a complementary treatment in various NO-disrupted conditions, e.g., hypertension, preeclampsia, and endothelial dysfunction. Here, we provide an overview of the potential efficacy of Arg as a NO precursor and its effects on glucose and insulin homeostasis and diabetes-induced cardiovascular complications.

Keywords: Arginine, Argininosuccinate lyase, Argininosuccinate synthase, Citrulline, Nitric oxide, Nitric oxide synthase, Ornithine aminotransferase, Ornithine transcarbamylase and ornithine decarboxylase, Type 2 diabetes. INTRODUCTION L-Arginine (Arg), a semi-essential or conditionally essential amino acid, is involved in synthesizing proteins, creatine, polyamines, agmatine, urea, and the metabolism of proline and glutamate in the body [1, 2]. Arg is provided by either the exogenous (dietary intake) or endogenous [de novo synthesis from L-citrulline (Cit) and turnover of proteins] sources; the sufficient magnitude of de novo synthesis makes Arg a non-essential amino acid in healthy adult humans. HowCorresponding author Asghar Ghasemi: Endocrine Physiology Research Center, Research Institute for Endocrine Sciences, Shahid Beheshti University of Medical Sciences, Tehran, Iran; [email protected]., No. 24, Erabi Street, Velenjak, Tehran, Iran; Phone: +98 21 22409309; Fax: +98 21 22416264. *

Asghar Ghasemi, Khosrow Kashfi, Zahra Bahadoran (Eds.) All rights reserved-© 2022 Bentham Science Publishers

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ever, during early development and pathologic conditions, such as infection, inflammation, and impaired renal or intestinal metabolic functions, de novo synthesis is not sufficient to meet metabolic needs [3]. Arg has received significant research interest over the last two decades as nitric oxide (NO) precursor [1, 2]. This property has led to the widespread use of Arg as a complementary treatment in various NO-disrupted conditions, including hypertension [4 - 6], preeclampsia [7], and endothelial dysfunction [8]. Because of its ability to increase NO production, Arg has been considered a potential complementary treatment in type 2 diabetes (T2D) to improve glucose and insulin homeostasis and diabetes-induced cardiovascular complications [6, 8 - 10]. In this review, the potential efficacy of Arg as a NO precursor is discussed in T2D. First, we provide an overview of the amino acid metabolism (biosynthesis pathways, catabolic pathways, and pharmacokinetics of oral ingested doses) and its contributions to cellular and whole-body NO synthesis. Then, we provide some evidence to investigate the undesirable change of metabolism of Arg in T2D. Finally, the effects of supplementation with Arg on glucose and insulin homeostasis, and diabetes-related cardiometabolic complications, investigated in animal experiments and human clinical trials, are discussed. PLASMA ARG FLUX Plasma levels of Arg range from 80-120 µM in healthy adults [1]. Plasma flux of an amino acid represents the difference between arterial and venous concentrations of the amino acid multiplied by plasma flow; a positive value indicates net influx (uptake), and a negative value indicates net efflux [11]. Fluxes of plasma Arg in healthy humans on a normal diet were estimated to be 63-70 and 70-95 µmol/kg/h in fasted and fed states, respectively [12, 13]; fed flux is higher because of increased entry of dietary Arg into plasma [14]. In healthy adults, about 10-15% (~5.5-9.2 µmol/kg/h) of the plasma Arg flux originates from de novo synthesis from Cit [12, 15]. Arg derived from protein turnover is ~ 36 µmol/kg/h [16]. As indicated in Fig. (1), the endogenous flux of Arg in the fed state is lower than in the fasted state (52 v. 63 µmol/kg/h), probably because of the availability of Arg from exogenous sources, which decreases protein turnover and de novo synthesis of Arg. Endogenous Arg flux, estimated after exclusion of dietary Arg intake from the plasma flux, remained unchanged following either free- and Arg-rich diets (~53 µmol/kg/h); contributions of protein breakdown and de novo synthesis of Arg were also similar in endogenous Arg flux in both conditions [16].

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Fig. (1). Determinants of plasma flux of L-arginine (Arg). Both exogenous (10-30%) and endogenous sources (60-90%) contribute to Arg plasma flux. Created with BioRender.com.

The relative amount of Arg in various dietary proteins has been determined at 315% [17]. The usual daily intake of Arg in healthy adults has been estimated to be 4-6 g/day, which is ~20% of its plasma flux [18]. The contribution of diet to plasma Arg flux may be as low as ~8-20% in the fasted state (6-11 µmol/kg/h) to as large as ~35–40% in the postprandial state (~22-36 µmol/kg/h) [14, 16, 19]. Following a 6-day Arg-free diet, these values reduced to 52±7 and 63±14 µmol/kg/h, whereas, during the same period, an Arg-rich diet increased plasma Arg fluxes to 69±8 and 87±12 µmol/kg/h in the fasted and fed states, respectively [16]. Fig. (1) displays determinants of plasma Arg flux. Arginine Biosynthesis Pathways A significant fraction of Arg is synthesized from the amino acid Cit through an intestinal-renal axis. About 50-80% of Cit released by the intestine is taken up by the kidneys [20, 21] and then converted into Arg within the proximal tubule via argininosuccinate synthase (ASS) and argininosuccinate lyase (ASL) enzymes (Fig. 2); about 75% [22] to 100% [20] of plasma Cit taken up by the kidney backs into the circulation as Arg. The extra-renal tissues are also involved (up to 40%) in Arg de novo synthesis for both meeting their needs for Arg and its release into circulation; in the nephrectomized mouse model (~80% nephrectomy), the amount of Cit accounted for plasma Arg decreased from 88 to 42% [23].

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Fig. (2). L-arginine is mainly synthesized from L-citrulline by an intestinal-renal axis. The extra-renal synthesis pathway of L-arginine from L-citrulline also contributes to the plasma L-arginine pool. ASS, argininosuccinate synthase; ASL, argininosuccinate lyase; NO, nitric oxide; NOS, NO synthase. Created with BioRender.com.

Arginine Catabolic Pathways In mammals, Arg is catabolized by five important enzymes, i.e., arginase, arginine-glycine transaminase (AGAT), kyotorphin synthase, nitric oxide synthase (NOS), and arginine decarboxylase [3, 24]. Different patterns of cellspecific expression and subcellular localization of these enzymes, compartmentalization of Arg metabolism, the presence of various inter-and intracellular transport systems, or fluxes of substrates can determine the fate of intracellular Arg [1, 18]. Fig. (3) displays Arg catabolic pathways. The intense focus on Arg as the NO precursor has resulted in lower attention to its other down-stream metabolic pathways (i.e., its role in protein synthesis, creatine, urea, polyamines, agmatine, proline, and glutamate) [1], which partake more fraction of Arg flux [12, 25]. A large fraction of Arg flux is diverted into arginase and the urea cycle (50% by hepatic arginase and 15% by extrahepatic arginase) [18]. About 10-30% of Arg (either exogenous or endogenous) is utilized to synthesize creatine using AGAT [18]. Compartmentalization of arginase with ornithine-utilizing enzymes (i.e., ornithine aminotransferase, OAT; ornithine transcarbamylase, OTC; and ornithine decarboxylase, ODC) shifts Arg into the production of proline, polyamines, and Cit [25 - 27]. A minor fraction of Arg flux (~1-2.8%) enters the NOS pathway [28] and acts as the largest source of nitrogen in the body for NO production [29]. Among the enzymes involved in Arg catabolism, we discuss arginase and NOS as the most important for cardiometabolic homeostasis [30].

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Fig. (3). L-arginine (Arg) catabolic pathways. A large fraction of Arg flux is diverted to arginase I and urea cycle (50% by hepatic and 15% by extrahepatic arginase I); 10-30% of Arg fraction is utilized for the synthesis of creatine (using L-arginine:glycine amidinotransferase), and only a minor fraction is shuttled into nitric oxide (NO) production. Cit, L-citrulline; NOS, NO synthase; OTC, ornithine transcarbamylase. Created with BioRender.com.

Arginase and Urea Production Quantitatively, the arginase pathway is the most critical catabolic pathway of Arg [12, 31]. There are two isoforms of arginase, a cytosolic isoform (Arginase I), which is primarily expressed in the liver (so-named liver arginase), and a mitochondrial isoform (arginase II), which is ubiquitously expressed in the extrahepatic tissues, particularly in the kidney (so named kidney arginase) [29, 32 - 34]. Nω-hydroxy-L-Arg, an intermediate of the NOS pathway, is a potent competitive inhibitor of arginase (Ki value=10-42 µM vs. Km value of 1 mM for arginine) [29, 34]; Cit is an allosteric inhibitor of arginase [33]. The arginase is widely expressed in mammalian tissues, and Arg is rapidly catabolized by the enzyme and increases serum concentrations of ornithine, urea, and proline [35]. The conversion rate of plasma Arg to urea was estimated as 11.5, and 12.8 µmol/kg/h in fed and fasted states, respectively; the fractions of plasma Arg flux diverted into urea production are 12.1% and 18.2% in the fed and fasted states (~15% Arg disappearance from plasma over 24-h) [12]. Arginase is co-expressed in NO-producing cells in the vasculature, and a modest level of arginase is constitutively expressed in the endothelial cells [36]. The Km of arginase and NOS for Arg are 2-20 mM and 2-20 μM, respectively; however, the Vmax of arginase is>1000 times of the NOS enzymes (1400 vs. 1 μmol/min/mg), indicating that increased arginase activity can limit the availability of Arg for NO synthesis [37 - 39].

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The amount of intracellular Arg catabolized by the arginase was ~200-fold more than those catabolized by NOS in endothelial cells [40]. Even in RBCs, considered as important as endothelial cells to supply plasma NO flux, the principal activity of arginase vs. endothelial NOS (eNOS, RBC-NOS) is well documented [41]. Arginase activity is significantly elevated in hypertension, exposure to inflammatory factors [e.g., lipopolysaccharides (LPS) and tumor necrosis factor-alpha (TNF-α)], and aging [30]. Increased arginase activity is involved in vascular dysfunction because arginase can reduce the supply of Arg needed to produce NO [36]. Arg and NO Production The NOS enzymes catalyze the oxidation of Arg to NO and Cit [28, 33, 42]. Three NOS isoforms, including constitutive neuronal (nNOS/NOS1), inducible (iNOS/NOS2), and constitutive eNOS (NOS3), have been identified [43 - 48]; all of them are expressed in endothelial cells [49]. The Km of nNOS, iNOS, and eNOS for Arg is 1.4-2.2, 2.8-32.3, and 2.9 µM, respectively [29, 38]. In healthy adults, 0.5-2.8% of the plasma Arg turnover is associated with NO production [12, 31, 50 - 52]. The conversion rate of plasma Arg to NO (estimated by the rate of conversion of the [15N]guanidino nitrogen of Arg to plasma [15N]ureido-Cit) is ~0.36 to 0.96 µmol/kg/h in healthy adults [12, 52]. About 14 µmol/kg (~0.6 µmol/kg/h) of endogenous Arg flux is used for NO synthesis [16]. Although a small fraction of the plasma Arg flux appears to be involved in NO production, the plasma Arg compartment serves as a significant (~54%) precursor pool for whole-body NO formation [12]. In some pathologic conditions, e.g., sepsis in which the patients experience a negative balance of Arg (higher rate of Arg oxidation than its de novo synthesis rate), the fraction of plasma Arg used for NO production may be increased [27]. In humans, about 0.34% of the dietary Arg trapped in the first pass within the splanchnic bed turns into NO (~16% of the whole endogenous NO synthesis per day) [13]. Less than 0.1% of the ingested dose of [15N]-Arg (85 mg/kg of body weight) was recovered in the 24-h urinary nitrate excreted [53]. More interestingly, the contribution of plasma Arg pool to whole-body NO synthesis (estimated according to urinary 15N-labeled nitrate excretion) was similar in both Arg-rich and Arg-free diets. In healthy adults, the contribution of Arg flux for NO production has been estimated to be 0.55 and 0.58% in Arg-rich and Arg-free diets, respectively; this observation was regardless of significant whole body Arg flux, and plasma concentrations occurred following Arg-rich diet [50]. As the endogenous competitive inhibitor of NOSs can antagonize NO production, asymmetric dimethyl-Arg (ADMA), increased availability of the original

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substrate (Arg) seems theoretical to be an effective strategy to restore NO formation, especially in subjects in whom NO production is impaired secondary to elevated ADMA. Targeting ADMA has received much attention because of its relationship with endothelial dysfunction and cardiovascular diseases [54, 55]. Short-term use of Arg to reverse the competitive ADMA-induced inhibition on NOS has given conflicting results; plasma ADMA concentrations have been reported to be remained unchanged [56] or even increased following Arg supplementation [57]. Theoretically, since Arg critically regulates intra- and extracellular levels of ADMA, either at the level of synthesis or its cellular transport, increased concentrations of Arg may result in increased ADMA concentration. Arg competitively inhibits dimethylarginine dimethylaminohydrolase (DDAH) and ADMA catabolism [58] and may saturate the y+ transport system (CAT transporters) and limit cellular export of ADMA, resulting in increased intracellular ADMA levels and inhibition of NO production [59]. Intracellular Arg Pools and NO Production Intracellular Arg is provided by three sources, including turnover of intracellular protein, Arg transported into the cell, and Arg synthesized endogenously from Cit via the action of ASL and ASS [3]. The transmembrane transport of Arg in endothelial cells is mainly mediated by CAT-1, localized in caveola [60]. Intraendothelial Arg concentration (100-3800 µM [29, 49, 60]) exceeds the Km of NOS enzymes, and Arg administration is not expected to enhance NO production; this is not, however, the case, a phenomenon that is called the Arg paradox [29, 48, 49, 61, 62]. The Arg paradox means that exogenous Arg administration drives NO production despite an excess of intracellular Arg availability [28, 61, 62]. Physiological concentrations of extracellular Arg regulate iNOS activity, and the higher the Arg concentrations, the higher iNOS translation [62]. Explanations for Arg paradox include stimulation of insulin secretion by Arg [49, 62], competitive inhibition of eNOS by ADMA [49, 60, 62], co-localization of Arg transporter (i.e., CAT-1 or system y+ transporter) and eNOS in caveolae [28, 49], and enhanced Arg-induced BH4 production [48, 49]. Co-localization of CAT-1 and eNOS makes Arg available to eNOS without mixing with intracellular pools [28]. Arg increases guanosine triphosphate cyclohydrolase I, the first and rate-limiting enzyme in de novo synthesis of BH4 [49]. Two intracellular pools of Arg, including pool I and pool II, are detected in endothelial cells and macrophages; pool I is exchangeable with extracellular cationic amino acids transported through the CAT system, whereas pool II does not rely on extracellular sources and is accessible to eNOS in endothelial cells

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(but not to iNOS in macrophages) and enable eNOS to be independent of extracellular Arg [63]. The iNOS activity in macrophages depends on the pool I and extracellular Arg when pool I cannot provide sufficient intracellular Arg [63]. Pool II seems to have two components; part one (named pool II-A) participates in the recycling of Cit to Arg and can be replenished by Cit, and part two (named pool II-B) is supplied by protein breakdown and is likely to accumulate the methyl-Arg and ADMA, and thus rendering its inhibitory effects on eNOS [64]. The regenerated Arg from Cit by ASS-ASL is preferred as a cellular source of Arg for NO production, and the capacity of the cell to recycle Cit to Arg, rather than extracellular accessibility to Arg itself, has been suggested to be rate-limiting for NO production [65]; this Cit-NO cycle, provides a ready source of Arg, especially for the cells with high-output NO synthesis [66]. Fig. (4) illustrates whole body Arg metabolism in relation NO production. Pharmacokinetics of Arg Arg is absorbed by the intestine (mainly jejunum) via a transport system shared with lysine, ornithine, and cysteine [21]; compared to other amino acids, Arg has relatively poor absorption [67]. Intestinal Arg absorption has saturable kinetics, and intragastric administration of high doses of Arg ceases its intestinal absorption and results in excessive secretion of water and electrolytes into the lumen; this is considered a nonspecific toxic reaction of Arg on the mucosa [67]. The intestinal absorption rate of Arg in rats has been reported to be 9.8 µmol/min/g (in the intestinal segment perfused with a dose of 20 mM Arg) [68]. Fig. (4) illustrates the pharmacokinetics and pharmacodynamics of Arg. Oral intake of Arg is subjected to a high (40-60%) splanchnic first-pass metabolism (FPM) by the intestine and liver [13, 31]. The fraction of orally ingested Arg converted into urea is 60% [31]. The conversion of ingested Arg into urea occurs rapidly within the early catabolic stage and reaches its maximum value within 30 min after ingestion; 90% of whole-body urea production from dietary Arg occurs almost entirely during its first pass (within the first 2-h post-ingestion period) [31]. The intestinal arginase activity critically modulates the release of endogenously synthesized or diet-derived Arg into the portal vein by the small intestine. Due to relatively high arginase activity in the intestine (arginase type II), 30-44% of exogenous Arg absorbed by the intestinal lumen is removed in the first pass within the splanchnic bed [69]; through intestinal arginase II activity, Arg is degraded and contributes into the synthesis of proline (13% in rat, 56% in pig), ornithine (32% in rat, 37% in pig), citrulline (17% in rat, 4% in pig), and less than 1% polyamines and NO [25]. Due to the high rate of hepatic arginase activity,

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most of the Arg that arrive in the liver is diverted into the urea cycle and thus hydrolyzed to ornithine and urea and provides a small amount of available systemic Arg [30]. Therefore substantial amounts of dietary Arg are not available to extra-intestinal tissues [25], and dietary Arg may only account for ~ 9-27% of its plasma flux [69, 70].

Fig. (4). The fate of orally ingested doses of L-arginine (Arg). Ingested Arg is extracted and utilized during the first-pass metabolism of the splanchnic region (intestinal and hepatic bed); Arg entered in the enterocytes is mainly confined into partial urea cycle by both cytosolic and mitochondrial arginases to produce urea, ornithine, citrulline (Cit), proline (pro), polyamines and CO2. The Arg delivered into the liver by the portal vein is subjected to further catabolism via arginase I and is mainly converted to urea; within the splanchnic metabolism, a minor fraction of the ingested dose of Arg is converted to NO. Finally, about 10-30% of ingested doses are available for circulation; OAT, ornithine aminotransferase; ODC, ornithine decarboxylase; OTC, ornithine transcarbamylase; GS, glutamine synthetase. The source of the Figure is Endogenous flux of nitric oxide: Citrulline is preferred to Arginine, Acta Physiologica (Oxford), 2021 Mar;231(3):e13572 [73].

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About 1 h after an oral load of 10 g of Arg, its peak plasma concentration ~287 µM (3-fold greater than the baseline level) can be observed [71]. Plasma Arg concentration after oral ingestion of an acute dose of 10 g Arg increased 3-fold whereas intravenous infusion of Arg (30 g over 30 min) increased its plasma concentration about 90-fold [71]; this substantial different pharmacokinetics of oral vs. intravenous Arg doses may imply on limited systemic availability of orally ingested Arg. Peak plasma Arg concentrations following infusion of 6 g Arg were ~3-fold higher than oral ingestion of the same dose (822 μM at Tmax=22 min vs. 310 μM at Tmax=90 min) [72]. Similar observations from the animal experiments clearly indicate the complexity of oral pharmacokinetics compared to intravenous doses of Arg [35]. Physiologic oral doses of Arg (up to 10 g) are eliminated from the plasma via non-renal mechanisms by a mean rate of 5 mL/min/kg; whereas high doses, resulting in supra-physiological plasma concentrations, are disappeared biphasically with a rapid renal clearance within 90 min (with a rate of 1.17 mL/min/kg) followed by a slower non-renal clearance (with a rate of 5 mL/min/kg) [71]; high doses of Arg exceeds the renal threshold for its reabsorption and result in Arg overflow into the urine [71, 72]. ARG, INSULIN RESISTANCE, AND T2D Changes in Arg Metabolism and Pathophysiology of T2D Current literature indicates that a decreased plasma concentration of Arg occurs among patients with T2D; however, this may differ at different stages of the disease and depends on the level of disease control. Compared to healthy adults, plasma concentrations of Arg in patients with T2D were considerably lower (38.2 vs. 148 µM); in the patients with microalbuminuria, more decreases in levels of plasma Arg were observed (24.6 vs. 51.6 μM) [74]. In a group of patients with T2D (mean age 61 years), the median (interquartile range; IQR) of Arg concentrations was significantly lower than the age-matched controls (median=33.5, IQR=10.2 vs. median 40.6, IQR=9.9 μM) [75]; plasma Arg concentration was negatively correlated with plasma glucose and glycated hemoglobin HbA1C (r= -0.22 and -0.21) [75]. In another study, there was no significant difference in plasma Arg concentration between healthy subjects and diabetic patients (137.7±23 vs. 134.9±34.8 μM); glycemic parameters were not related to Arg concentration [76]. Intensified diabetes management (with a target of HbA1C174 mmol per day) [104]. Compared to healthy subjects, diabetic patients showed better tolerability for doses of 9 g and reported lower gastrointestinal symptoms; it has been suggested that this may be attributed to an effect of diabetes on gastrointestinal motility and pharmacokinetics of Arg [104]. Beyond prevention of gastrointestinal adverse effects, defining an optimum dose of Arg (to be both effective and safe) is critical in patients with T2D since higher doses of Arg could paradoxically induce lipid oxidation, peroxynitrite formation, and NOS uncoupling [107], increased ADMA levels [57, 59], and ornithine-urea production [108] (via induction of arginase) [24, 109]. Increased level of plasma ADMA following oral doses of 3, 9, and 21 g per day of Arg was from 922 to 982, 1030, and 976 nM, respectively; ornithine levels also increased from 64.5 to 68.7, 85.0, and 79.4 µM during ingestion of these doses [106].

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CONCLUDING REMARKS Arg supplementation is considered a complementary treatment in T2D because of its ability to restore disrupted NO production. Experimental studies reported some beneficial effects of Arg therapy on either insulin-glucose homeostasis or diabetes-induced complications, especially diabetic nephropathy, and vascular dysfunction. However, limited long-term randomized clinical trials have been conducted to confirm the efficacy of Arg supplementation in patients with T2D. Undesirable side effects of Arg (especially at high doses or long-term loading) may also limit its utilization in diabetic patients. CONSENT OF PUBLICATION Permission from Acta Physiologica (Oxford) for Fig. (4). CONFLICT OF INTEREST The author declares no conflict of interest, financial or otherwise. ACKNOWLEDGEMENT Declared none. REFERENCES [1]

Morris SM Jr. Arginine metabolism: boundaries of our knowledge. J Nutr 2007; 137(6) (Suppl. 2): 1602S-9S. [http://dx.doi.org/10.1093/jn/137.6.1602S] [PMID: 17513435]

[2]

Wu G, Morris SM Jr. Arginine metabolism: nitric oxide and beyond. The Biochemical journal 1998; 336: 1-17. [http://dx.doi.org/10.1042/bj3360001]

[3]

Morris SM Jr. Arginine Metabolism Revisited. J Nutr 2016; 146(12): 2579S-86S. [http://dx.doi.org/10.3945/jn.115.226621] [PMID: 27934648]

[4]

Dong JY, Qin LQ, Zhang Z, et al. Effect of oral l-arginine supplementation on blood pressure: A meta-analysis of randomized, double-blind, placebo-controlled trials. Am Heart J 2011; 162(6): 95965. [http://dx.doi.org/10.1016/j.ahj.2011.09.012] [PMID: 22137067]

[5]

McRae MP. Therapeutic Benefits of l-Arginine: An Umbrella Review of Meta-analyses. J Chiropr Med 2016; 15(3): 184-9. [http://dx.doi.org/10.1016/j.jcm.2016.06.002] [PMID: 27660594]

[6]

Fisman EZ, Tenenbaum A, Shapira I, Pines A, Motro M. The nitric oxide pathway: is L-arginine a gate to the new millennium medicine? A meta-analysis of L-arginine effects. J Med 1999; 30(3-4): 131-48. [PMID: 17312667]

[7]

Zhu Q, Yue X, Tian QY, et al. Effect of L-arginine supplementation on blood pressure in pregnant women: a meta-analysis of placebo-controlled trials. Hypertens Pregnancy 2013; 32(1): 32-41. [http://dx.doi.org/10.3109/10641955.2012.697952] [PMID: 22957482]

276 The Role of Nitric Oxide in Type 2 Diabetes

Mirmiran et al.

[8]

Lucotti P, Monti L, Setola E, et al. Oral l-arginine supplementation improves endothelial function and ameliorates insulin sensitivity and inflammation in cardiopathic nondiabetic patients after an aortocoronary bypass. Metabolism 2009; 58(9): 1270-6. [http://dx.doi.org/10.1016/j.metabol.2009.03.029] [PMID: 19592054]

[9]

Piatti P, Monti LD, Valsecchi G, et al. Long-term oral L-arginine administration improves peripheral and hepatic insulin sensitivity in type 2 diabetic patients. Diabetes Care 2001; 24(5): 875-80. [http://dx.doi.org/10.2337/diacare.24.5.875] [PMID: 11347747]

[10]

You H, Gao T, Cooper TK, Morris SM Jr, Awad AS, Awad AS. Diabetic nephropathy is resistant to oral L -arginine or L -citrulline supplementation. Am J Physiol Renal Physiol 2014; 307(11): F1292301. [http://dx.doi.org/10.1152/ajprenal.00176.2014] [PMID: 25320354]

[11]

Fong Y, Rosenbaum M, Tracey KJ, et al. Recombinant growth hormone enhances muscle myosin heavy-chain mRNA accumulation and amino acid accrual in humans. Proc Natl Acad Sci USA 1989; 86(9): 3371-4. [http://dx.doi.org/10.1073/pnas.86.9.3371] [PMID: 2497466]

[12]

Castillo L, Beaumier L, Ajami AM, Young VR. Whole body nitric oxide synthesis in healthy men determined from [15N] arginine-to-[15N]citrulline labeling. Proc Natl Acad Sci USA 1996; 93(21): 11460-5. [http://dx.doi.org/10.1073/pnas.93.21.11460] [PMID: 8876157]

[13]

Castillo L, deRojas TC, Chapman TE, et al. Splanchnic metabolism of dietary arginine in relation to nitric oxide synthesis in normal adult man. Proc Natl Acad Sci USA 1993; 90(1): 193-7. [http://dx.doi.org/10.1073/pnas.90.1.193] [PMID: 8419922]

[14]

Castillo L, Chapman TE, Sanchez M, et al. Plasma arginine and citrulline kinetics in adults given adequate and arginine-free diets. Proc Natl Acad Sci USA 1993; 90(16): 7749-53. [http://dx.doi.org/10.1073/pnas.90.16.7749] [PMID: 8356080]

[15]

El-Hattab AW, Hsu JW, Emrick LT, et al. Restoration of impaired nitric oxide production in MELAS syndrome with citrulline and arginine supplementation. Mol Genet Metab 2012; 105(4): 607-14. [http://dx.doi.org/10.1016/j.ymgme.2012.01.016] [PMID: 22325939]

[16]

Castillo L, Ajami A, Branch S, et al. Plasma arginine kinetics in adult man: Response to an argininefree diet. Metabolism 1994; 43(1): 114-22. [http://dx.doi.org/10.1016/0026-0495(94)90166-X] [PMID: 8289668]

[17]

Lüneburg N, Xanthakis V, Schwedhelm E, et al. Reference intervals for plasma L-arginine and the Larginine:asymmetric dimethylarginine ratio in the Framingham Offspring Cohort. J Nutr 2011; 141(12): 2186-90. [http://dx.doi.org/10.3945/jn.111.148197] [PMID: 22031661]

[18]

Luiking YC, Castillo L, Deutz NE. Arginine, citrulline, and nitric oxide. Modern Nutrition in Health and Disease: Eleventh Edition: Wolters Kluwer Health Adis (ESP). 2012; pp. 477-86.

[19]

Castillo L, Sánchez M, Chapman TE, Ajami A, Burke JF, Young VR. The plasma flux and oxidation rate of ornithine adaptively decline with restricted arginine intake. Proc Natl Acad Sci USA 1994; 91(14): 6393-7. [http://dx.doi.org/10.1073/pnas.91.14.6393] [PMID: 8022794]

[20]

Ligthart-Melis GC, van de Poll MCG, Boelens PG, Dejong CHC, Deutz NEP, van Leeuwen PAM. Glutamine is an important precursor for de novo synthesis of arginine in humans. Am J Clin Nutr 2008; 87(5): 1282-9. [http://dx.doi.org/10.1093/ajcn/87.5.1282] [PMID: 18469251]

[21]

Barbul A. Arginine: biochemistry, physiology, and therapeutic implications. JPEN J Parenter Enteral Nutr 1986; 10(2): 227-38. [http://dx.doi.org/10.1177/0148607186010002227] [PMID: 3514981]

Arginine, NO and T2D

The Role of Nitric Oxide in Type 2 Diabetes 277

[22]

Windmueller HG, Spaeth AE. Source and fate of circulating citrulline. Am J Physiol 1981; 241(6): E473-80. [PMID: 7325229]

[23]

Marini JC, Didelija IC, Fiorotto ML. Extrarenal citrulline disposal in mice with impaired renal function. Am J Physiol Renal Physiol 2014; 307(6): F660-5. [http://dx.doi.org/10.1152/ajprenal.00289.2014] [PMID: 25056350]

[24]

Cynober L, Boucher JL, Vasson MP. Arginine metabolism in mammals. J Nutr Biochem 1995; 6(8): 402-13. [http://dx.doi.org/10.1016/0955-2863(95)00066-9]

[25]

Wu G. Intestinal mucosal amino acid catabolism. J Nutr 1998; 128(8): 1249-52. [http://dx.doi.org/10.1093/jn/128.8.1249] [PMID: 9687539]

[26]

Ozaki M, Gotoh T, Nagasaki A, et al. Expression of arginase II and related enzymes in the rat small intestine and kidney. J Biochem 1999; 125(3): 586-93. [http://dx.doi.org/10.1093/oxfordjournals.jbchem.a022324] [PMID: 10050048]

[27]

Argaman Z, Young VR, Noviski N, et al. Arginine and nitric oxide metabolism in critically ill septic pediatric patients. Crit Care Med 2003; 31(2): 591-7. [http://dx.doi.org/10.1097/01.CCM.0000050291.37714.74] [PMID: 12576971]

[28]

Luiking YC, Ten Have GAM, Wolfe RR, Deutz NEP. Arginine de novo and nitric oxide production in disease states. Am J Physiol Endocrinol Metab 2012; 303(10): E1177-89. [http://dx.doi.org/10.1152/ajpendo.00284.2012] [PMID: 23011059]

[29]

Huynh NN, Chin-Dusting J. Amino acids, arginase and nitric oxide in vascular health. Clin Exp Pharmacol Physiol 2006; 33(1-2): 1-8. [http://dx.doi.org/10.1111/j.1440-1681.2006.04316.x] [PMID: 16445692]

[30]

Morris SM Jr. Arginine metabolism in vascular biology and disease. Vasc Med 2005; 10(1_suppl) (Suppl. 1): S83-7. [http://dx.doi.org/10.1177/1358836X0501000112] [PMID: 16444873]

[31]

Mariotti F, Petzke KJ, Bonnet D, et al. Kinetics of the utilization of dietary arginine for nitric oxide and urea synthesis: insight into the arginine–nitric oxide metabolic system in humans. Am J Clin Nutr 2013; 97(5): 972-9. [http://dx.doi.org/10.3945/ajcn.112.048025] [PMID: 23535108]

[32]

Rodríguez-Gómez I, Manuel Moreno J, Jimenez R, et al. Effects of Arginase Inhibition in Hypertensive Hyperthyroid Rats. Am J Hypertens 2015; 28(12): 1464-72. [http://dx.doi.org/10.1093/ajh/hpv049] [PMID: 25907224]

[33]

Caldwell RB, Toque HA, Narayanan SP, Caldwell RW. Arginase: an old enzyme with new tricks. Trends Pharmacol Sci 2015; 36(6): 395-405. [http://dx.doi.org/10.1016/j.tips.2015.03.006] [PMID: 25930708]

[34]

Ash DE. Structure and function of arginases. J Nutr 2004; 134(10) (Suppl.): 2760S-4S. [http://dx.doi.org/10.1093/jn/134.10.2760S] [PMID: 15465781]

[35]

Wu G, Bazer FW, Cudd TA, et al. Pharmacokinetics and safety of arginine supplementation in animals. J Nutr 2007; 137(6) (Suppl. 2): 1673S-80S. [http://dx.doi.org/10.1093/jn/137.6.1673S] [PMID: 17513446]

[36]

Caldwell RW, Rodriguez PC, Toque HA, Narayanan SP, Caldwell RB. Arginase: A Multifaceted Enzyme Important in Health and Disease. Physiol Rev 2018; 98(2): 641-65. [http://dx.doi.org/10.1152/physrev.00037.2016] [PMID: 29412048]

[37]

Wu G, Morris SM Jr. Arginine metabolism: nitric oxide and beyond. Biochem J 1998; 336(1): 1-17. [http://dx.doi.org/10.1042/bj3360001] [PMID: 9806879]

[38]

Forstermann U, Sessa WC. Nitric oxide synthases: regulation and function. European Heart Journal

278 The Role of Nitric Oxide in Type 2 Diabetes

Mirmiran et al.

2012; 33(7): 829-37. [http://dx.doi.org/10.1093/eurheartj/ehr304] [39]

Ghasemi A, Mehrazin F, Zahediasl S. Effect of nitrate and l-arginine therapy on nitric oxide levels in serum, heart, and aorta of fetal hypothyroid rats. J Physiol Biochem 2013; 69(4): 751-9. [http://dx.doi.org/10.1007/s13105-013-0251-x] [PMID: 23568620]

[40]

Wu G, Meininger CJ. Impaired arginine metabolism and NO synthesis in coronary endothelial cells of the spontaneously diabetic BB rat. Am J Physiol 1995; 269(4 Pt 2): H1312-8. [PMID: 7485563]

[41]

Eligini S, Porro B, Lualdi A, Squellerio I, Veglia F, Chiorino E, et al. Nitric oxide synthetic pathway in red blood cells is impaired in coronary artery disease. PloS one 2013; 8(8): e66945. [http://dx.doi.org/10.1371/journal.pone.0066945]

[42]

Lundberg JO, Weitzberg E. NO-synthase independent NO generation in mammals. Biochem Biophys Res Commun 2010; 396(1): 39-45. [http://dx.doi.org/10.1016/j.bbrc.2010.02.136] [PMID: 20494108]

[43]

Wu G, Meininger CJ. Regulation of nitric oxide synthesis by dietary factors. Annu Rev Nutr 2002; 22(1): 61-86. [http://dx.doi.org/10.1146/annurev.nutr.22.110901.145329] [PMID: 12055338]

[44]

Dudzinski DM, Igarashi J, Greif D, Michel T. The regulation and pharmacology of endothelial nitric oxide synthase. Annu Rev Pharmacol Toxicol 2006; 46(1): 235-76. [http://dx.doi.org/10.1146/annurev.pharmtox.44.101802.121844] [PMID: 16402905]

[45]

Pacher P, Beckman JS, Liaudet L. Nitric oxide and peroxynitrite in health and disease. Physiol Rev 2007; 87(1): 315-424. [http://dx.doi.org/10.1152/physrev.00029.2006] [PMID: 17237348]

[46]

Murad F. Shattuck Lecture. Nitric oxide and cyclic GMP in cell signaling and drug development. N Engl J Med 2006; 355(19): 2003-11. [http://dx.doi.org/10.1056/NEJMsa063904] [PMID: 17093251]

[47]

Wang XL, Sim AS, Badenhop RF, Mccredie RM, Wilcken DEL. A smoking–dependent risk of coronary artery disease associated with a polymorphism of the endothelial nitric oxide synthase gene. Nat Med 1996; 2(1): 41-5. [http://dx.doi.org/10.1038/nm0196-41] [PMID: 8564837]

[48]

Luiking YC, Engelen MPKJ, Deutz NEP. Regulation of nitric oxide production in health and disease. Curr Opin Clin Nutr Metab Care 2010; 13(1): 97-104. [http://dx.doi.org/10.1097/MCO.0b013e328332f99d] [PMID: 19841582]

[49]

Wu G, Meininger CJ. Nitric oxide and vascular insulin resistance. Biofactors 2009; 35(1): 21-7. [http://dx.doi.org/10.1002/biof.3] [PMID: 19319842]

[50]

Castillo L, Sánchez M, Vogt J, et al. Plasma arginine, citrulline, and ornithine kinetics in adults, with observations on nitric oxide synthesis. Am J Physiol 1995; 268(2 Pt 1): E360-7. [PMID: 7864114]

[51]

Avogaro A, Toffolo G, Kiwanuka E, de Kreutzenberg SV, Tessari P, Cobelli C. L-arginine-nitric oxide kinetics in normal and type 2 diabetic subjects: a stable-labelled 15N arginine approach. Diabetes 2003; 52(3): 795-802. [http://dx.doi.org/10.2337/diabetes.52.3.795] [PMID: 12606522]

[52]

Kim IY, Schutzler SE, Schrader A, et al. Acute ingestion of citrulline stimulates nitric oxide synthesis but does not increase blood flow in healthy young and older adults with heart failure. Am J Physiol Endocrinol Metab 2015; 309(11): E915-24. [http://dx.doi.org/10.1152/ajpendo.00339.2015] [PMID: 26442881]

[53]

Leaf CD, Wishnok JS, Tannenbaum SR. L-Arginine is a precursor for nitrate biosynthesis in humans. Biochem Biophys Res Commun 1989; 163(2): 1032-7.

Arginine, NO and T2D

The Role of Nitric Oxide in Type 2 Diabetes 279

[http://dx.doi.org/10.1016/0006-291X(89)92325-5] [PMID: 2783109] [54]

Liu X, Xu X, Shang R, Chen Y. Asymmetric dimethylarginine (ADMA) as an important risk factor for the increased cardiovascular diseases and heart failure in chronic kidney disease. Nitric oxide: biology and chemistry 2018; 78: 113-20.

[55]

Zhou S, Zhu Q, Li X, et al. Asymmetric dimethylarginine and all-cause mortality: a systematic review and meta-analysis. Sci Rep 2017; 7(1): 44692. [http://dx.doi.org/10.1038/srep44692] [PMID: 28294182]

[56]

Walker HA, McGing E, Fisher I, et al. Endothelium-dependent vasodilation is independent of the plasma L-arginine/ADMA ratio in men with stable angina. J Am Coll Cardiol 2001; 38(2): 499-505. [http://dx.doi.org/10.1016/S0735-1097(01)01380-8] [PMID: 11499744]

[57]

Jabecka A, Ast J, Bogdaski P, et al. Oral L-arginine supplementation in patients with mild arterial hypertension and its effect on plasma level of asymmetric dimethylarginine, L-citruline, L-arginine and antioxidant status. Eur Rev Med Pharmacol Sci 2012; 16(12): 1665-74. [PMID: 23161038]

[58]

Wang J, Sim AS, Wang XL, Wilcken DEL. L-arginine regulates asymmetric dimethylarginine metabolism by inhibiting dimethylarginine dimethylaminohydrolase activity in hepatic (HepG2) cells. Cell Mol Life Sci 2006; 63(23): 2838-46. [http://dx.doi.org/10.1007/s00018-006-6271-8] [PMID: 17075694]

[59]

Teerlink T, Luo Z, Palm F, Wilcox CS. Cellular ADMA: Regulation and action. Pharmacol Res 2009; 60(6): 448-60. [http://dx.doi.org/10.1016/j.phrs.2009.08.002] [PMID: 19682580]

[60]

Rajapakse NW, Nanayakkara S, Kaye DM. Pathogenesis and treatment of the cardiorenal syndrome: Implications of L-arginine-nitric oxide pathway impairment. Pharmacol Ther 2015; 154: 1-12. [http://dx.doi.org/10.1016/j.pharmthera.2015.05.011] [PMID: 25989232]

[61]

Kurz S, Harrison DG. Insulin and the arginine paradox. J Clin Invest 1997; 99(3): 369-70. [http://dx.doi.org/10.1172/JCI119166] [PMID: 9022065]

[62]

Lee J, Ryu H, Ferrante RJ, Morris SM Jr, Ratan RR. Translational control of inducible nitric oxide synthase expression by arginine can explain the arginine paradox. Proc Natl Acad Sci USA 2003; 100(8): 4843-8. [http://dx.doi.org/10.1073/pnas.0735876100] [PMID: 12655043]

[63]

Closs EI, Scheld JS, Sharafi M, Förstermann U. Substrate supply for nitric-oxide synthase in macrophages and endothelial cells: role of cationic amino acid transporters. Mol Pharmacol 2000; 57(1): 68-74. [PMID: 10617680]

[64]

Simon A, Plies L, Habermeier A, Martiné U, Reining M, Closs EI. Role of neutral amino acid transport and protein breakdown for substrate supply of nitric oxide synthase in human endothelial cells. Circ Res 2003; 93(9): 813-20. [http://dx.doi.org/10.1161/01.RES.0000097761.19223.0D] [PMID: 14512444]

[65]

Xie L, Gross SS. Argininosuccinate synthetase overexpression in vascular smooth muscle cells potentiates immunostimulant-induced NO production. J Biol Chem 1997; 272(26): 16624-30. [http://dx.doi.org/10.1074/jbc.272.26.16624] [PMID: 9195976]

[66]

Xie L, Hattori Y, Tume N, Gross SS. The preferred source of arginine for high-output nitric oxide synthesis in blood vessels. Semin Perinatol 2000; 24(1): 42-5. [http://dx.doi.org/10.1016/S0146-0005(00)80054-3] [PMID: 10709858]

[67]

Hellier MD, Chir B, Holdsworth CD, Perrett D. Dibasic amino acid absorption in man. Gastroenterology 1973; 65(4): 613-8. [http://dx.doi.org/10.1016/S0016-5085(19)33041-0] [PMID: 4746764]

[68]

Mourad FH, O’Donnell LJ, Andre EA, et al. L-Arginine, nitric oxide, and intestinal secretion: studies

280 The Role of Nitric Oxide in Type 2 Diabetes

Mirmiran et al.

in rat jejunum in vivo. Gut 1996; 39(4): 539-44. [http://dx.doi.org/10.1136/gut.39.4.539] [PMID: 8944562] [69]

Castillo L, Chapman TE, Yu YM, Ajami A, Burke JF, Young VR. Dietary arginine uptake by the splanchnic region in adult humans. Am J Physiol 1993; 265(4 Pt 1): E532-9. [PMID: 8238326]

[70]

Deferrari G, Garibotto G, Robaudo C, Sala M, Tizianello A. Splanchnic exchange of amino acids after amino acid ingestion in patients with chronic renal insufficiency. Am J Clin Nutr 1988; 48(1): 72-83. [http://dx.doi.org/10.1093/ajcn/48.1.72] [PMID: 3291599]

[71]

Tangphao O, Grossmann M, Chalon S, Hoffman BB, Blaschke TF. Pharmacokinetics of intravenous and oral L-arginine in normal volunteers. Br J Clin Pharmacol 1999; 47(3): 261-6. [http://dx.doi.org/10.1046/j.1365-2125.1999.00883.x] [PMID: 10215749]

[72]

Bode-Böger SM, Böger RH, Galland A, Tsikas D, Frölich JC. L-arginine-induced vasodilation in healthy humans:pharmacokinetic–pharmacodynamic relationship. Br J Clin Pharmacol 1998; 46(5): 489-97. [http://dx.doi.org/10.1046/j.1365-2125.1998.00803.x] [PMID: 9833603]

[73]

Bahadoran Z, Mirmiran P, Kashfi K, Ghasemi A. Endogenous flux of nitric oxide: Citrulline is preferred to Arginine. Acta Physiol (Oxf) 2021; 231(3): e13572. [http://dx.doi.org/10.1111/apha.13572] [PMID: 33089645]

[74]

Barış N, Erdoğan M, Sezer E, et al. Alterations in l-arginine and inflammatory markers in type 2 diabetic patients with and without microalbuminuria. Acta Diabetol 2009; 46(4): 309-16. [http://dx.doi.org/10.1007/s00592-008-0089-9] [PMID: 19183843]

[75]

Drabkova P, Sanderova J, Kovarik J. An Assay of Selected Serum Amino Acids in Patients with Type 2 Diabetes Mellitus. Advances in clinical and experimental medicine: official organ Wroclaw Medical University 2015; 24(3): 447-51.

[76]

Zhou Y, Qiu L, Xiao Q, et al. Obesity and diabetes related plasma amino acid alterations. Clin Biochem 2013; 46(15): 1447-52. [http://dx.doi.org/10.1016/j.clinbiochem.2013.05.045] [PMID: 23697717]

[77]

Tripolt NJ, Meinitzer A, Eder M, Wascher TC, Pieber TR, Sourij H. Multifactorial risk factor intervention in patients with Type 2 diabetes improves arginine bioavailability ratios. Diabet Med 2012; 29(10): e365-8. [http://dx.doi.org/10.1111/j.1464-5491.2012.03743.x] [PMID: 22803961]

[78]

Tang WHW, Wang Z, Cho L, Brennan DM, Hazen SL. Diminished global arginine bioavailability and increased arginine catabolism as metabolic profile of increased cardiovascular risk. J Am Coll Cardiol 2009; 53(22): 2061-7. [http://dx.doi.org/10.1016/j.jacc.2009.02.036] [PMID: 19477356]

[79]

Ramírez-Zamora S, Méndez-Rodríguez ML, Olguín-Martínez M, et al. Increased erythrocytes byproducts of arginine catabolism are associated with hyperglycemia and could be involved in the pathogenesis of type 2 diabetes mellitus. PLoS One 2013; 8(6): e66823. [http://dx.doi.org/10.1371/journal.pone.0066823] [PMID: 23826148]

[80]

Contreras-Zentella ML, Sánchez-Sevilla L, Suárez-Cuenca JA, Olguín-Martínez M, AlatristeContreras MG, García-García N, et al. The role of oxidant stress and gender in the erythrocyte arginine metabolism and ammonia management in patients with type 2 diabetes. PloS one 2019; 14(7): e0219481. [http://dx.doi.org/10.1371/journal.pone.0219481]

[81]

Savu O, Iosif L, Bradescu OM, Serafinceanu C, Papacocea R, Stoian I. L-arginine catabolism is driven mainly towards nitric oxide synthesis in the erythrocytes of patients with type 2 diabetes at first clinical onset. Ann Clin Biochem 2015; 52(1): 135-43. [http://dx.doi.org/10.1177/0004563214531739] [PMID: 24675988]

Arginine, NO and T2D

The Role of Nitric Oxide in Type 2 Diabetes 281

[82]

MacKellar M, Vigerust DJ. Role of Haptoglobin in Health and Disease: A Focus on Diabetes. Clin Diabetes 2016; 34(3): 148-57. [http://dx.doi.org/10.2337/diaclin.34.3.148] [PMID: 27621532]

[83]

Abraham NG, Junge JM, Drummond GS. Translational Significance of Heme Oxygenase in Obesity and Metabolic Syndrome. Trends Pharmacol Sci 2016; 37(1): 17-36. [http://dx.doi.org/10.1016/j.tips.2015.09.003] [PMID: 26515032]

[84]

Meerarani P, Levy A, Purushothaman K. Down-regulation of hemoxygenase-1 gene expression is associated with decreased ferritin and increased iron deposition in diabetic atherosclerotic plaques. Diabetes 2008; 57: A179.

[85]

Omodeo-Salè F, Cortelezzi L, Vommaro Z, Scaccabarozzi D, Dondorp AM. Dysregulation of L arginine metabolism and bioavailability associated to free plasma heme. Am J Physiol Cell Physiol 2010; 299(1): C148-54. [http://dx.doi.org/10.1152/ajpcell.00405.2009] [PMID: 20357184]

[86]

Bahadoran Z, Mirmiran P, Ghasemi A. Role of Nitric Oxide in Insulin Secretion and Glucose Metabolism. Trends Endocrinol Metab 2020; 31(2): 118-30. [http://dx.doi.org/10.1016/j.tem.2019.10.001] [PMID: 31690508]

[87]

Kashyap SR, Roman LJ, Lamont J, et al. Insulin resistance is associated with impaired nitric oxide synthase activity in skeletal muscle of type 2 diabetic subjects. J Clin Endocrinol Metab 2005; 90(2): 1100-5. [http://dx.doi.org/10.1210/jc.2004-0745] [PMID: 15562034]

[88]

Lucotti P, Setola E, Monti LD, et al. Beneficial effects of a long-term oral L -arginine treatment added to a hypocaloric diet and exercise training program in obese, insulin-resistant type 2 diabetic patients. Am J Physiol Endocrinol Metab 2006; 291(5): E906-12. [http://dx.doi.org/10.1152/ajpendo.00002.2006] [PMID: 16772327]

[89]

Newsholme P, Brennan L, Bender K. Amino Acid Metabolism, β-Cell Function, and Diabetes. Diabetes 2006; 55 (Suppl. 2): S39-47. [http://dx.doi.org/10.2337/db06-S006]

[90]

Miczke A, Suliburska J, Pupek-Musialik D, et al. Effect of L-arginine supplementation on insulin resistance and serum adiponectin concentration in rats with fat diet. Int J Clin Exp Med 2015; 8(7): 10358-66. [PMID: 26379826]

[91]

Míguez L, Mariño G, Rodríguez B, Taboada C. Effects of dietary L-arginine supplementation on serum lipids and intestinal enzyme activities in diabetic rats. J Physiol Biochem 2004; 60(1): 31-7. [http://dx.doi.org/10.1007/BF03168218] [PMID: 15352382]

[92]

Claybaugh T, Decker S, McCall K, et al. L-Arginine Supplementation in Type II Diabetic Rats Preserves Renal Function and Improves Insulin Sensitivity by Altering the Nitric Oxide Pathway. Int J Endocrinol 2014; 2014: 1-7. [http://dx.doi.org/10.1155/2014/171546] [PMID: 24523733]

[93]

Bogdanski P, Szulinska M, Suliburska J, Pupek-Musialik D, Jablecka A, Witmanowski H. Supplementation with L-arginine favorably influences plasminogen activator inhibitor type 1 concentration in obese patients. A randomized, double blind trial. J Endocrinol Invest 2013; 36(4): 221-6. [PMID: 22732180]

[94]

Bogdanski P, Suliburska J, Grabanska K, et al. Effect of 3-month L-arginine supplementation on insulin resistance and tumor necrosis factor activity in patients with visceral obesity. Eur Rev Med Pharmacol Sci 2012; 16(6): 816-23. [PMID: 22913215]

[95]

Regensteiner JG, Popylisen S, Bauer TA, Lindenfeld J, Gill E, Smith S, et al. Oral L-arginine and

282 The Role of Nitric Oxide in Type 2 Diabetes

Mirmiran et al.

vitamins E and C improve endothelial function in women with type 2 diabetes. Vascular medicine (London, England) 2003; 8(3): 169-75. [96]

Jabłecka A, Bogdański P, Balcer N, Cieślewicz A, Skołuda A, Musialik K. The effect of oral Larginine supplementation on fasting glucose, HbA1c, nitric oxide and total antioxidant status in diabetic patients with atherosclerotic peripheral arterial disease of lower extremities. Eur Rev Med Pharmacol Sci 2012; 16(3): 342-50. [PMID: 22530351]

[97]

Jude EB, Dang C, Boulton AJM. Effect of l-arginine on the microcirculation in the neuropathic diabetic foot in Type 2 diabetes mellitus: a double-blind, placebo-controlled study. Diabet Med 2010; 27(1): 113-6. [http://dx.doi.org/10.1111/j.1464-5491.2009.02876.x] [PMID: 20121898]

[98]

Monti LD, Casiraghi MC, Setola E, et al. l-Arginine enriched biscuits improve endothelial function and glucose metabolism: A pilot study in healthy subjects and a cross-over study in subjects with impaired glucose tolerance and metabolic syndrome. Metabolism 2013; 62(2): 255-64. [http://dx.doi.org/10.1016/j.metabol.2012.08.004] [PMID: 23040413]

[99]

Monti LD, Galluccio E, Villa V, Fontana B, Spadoni S, Piatti PM. Decreased diabetes risk over 9 year after 18-month oral l-arginine treatment in middle-aged subjects with impaired glucose tolerance and metabolic syndrome (extension evaluation of l-arginine study). Eur J Nutr 2018; 57(8): 2805-17. [http://dx.doi.org/10.1007/s00394-017-1548-2] [PMID: 29052766]

[100] Lin SL, Lin M, Wang KL, Kuo HW, Tak T. l -Arginine Can Enhance the Beneficial Effect of Losartan in Patients with Chronic Aortic Regurgitation and Isolated Systolic Hypertension. The International journal of angiology: official publication of the International College of Angiology. Inc 2021; 30(2): 122-31. [101] Reule CA, Goyvaerts B, Schoen C. Effects of an L-arginine-based multi ingredient product on endothelial function in subjects with mild to moderate hypertension and hyperhomocysteinemia - a randomized, double-blind, placebo-controlled, cross-over trial. BMC Complement Altern Med 2017; 17(1): 92. [http://dx.doi.org/10.1186/s12906-017-1603-9] [PMID: 28153005] [102] Hadi A, Arab A, Moradi S, Pantovic A, Clark CCT, Ghaedi E. The effect of L -arginine supplementation on lipid profile: a systematic review and meta-analysis of randomised controlled trials. Br J Nutr 2019; 122(9): 1021-32. [http://dx.doi.org/10.1017/S0007114519001855] [PMID: 31922465] [103] Sepandi M, Abbaszadeh S, qobady S, Taghdir M. Effect of L-Arginine supplementation on lipid profiles and inflammatory markers: A systematic review and meta-analysis of randomized controlled trials. Pharmacol Res 2019; 148: 104407. [http://dx.doi.org/10.1016/j.phrs.2019.104407] [PMID: 31442577] [104] Grimble GK. Adverse gastrointestinal effects of arginine and related amino acids. J Nutr 2007; 137(6) (Suppl. 2): 1693S-701S. [http://dx.doi.org/10.1093/jn/137.6.1693S] [PMID: 17513449] [105] Rashid J, Kumar SS, Job KM, Liu X, Fike CD, Sherwin CMT. Therapeutic Potential of Citrulline as an Arginine Supplement: A Clinical Pharmacology Review. Paediatr Drugs 2020; 22(3): 279-93. [http://dx.doi.org/10.1007/s40272-020-00384-5] [PMID: 32140997] [106] Evans RW, Fernstrom JD, Thompson J, Morris SM Jr, Kuller LH. Biochemical responses of healthy subjects during dietary supplementation with L-arginine. J Nutr Biochem 2004; 15(9): 534-9. [http://dx.doi.org/10.1016/j.jnutbio.2004.03.005] [PMID: 15350985] [107] Chen J, Kuhlencordt P, Urano F, Ichinose H, Astern J, Huang PL. Effects of chronic treatment with Larginine on atherosclerosis in apoE knockout and apoE/inducible NO synthase double-knockout mice. Arterioscler Thromb Vasc Biol 2003; 23(1): 97-103. [http://dx.doi.org/10.1161/01.ATV.0000040223.74255.5A] [PMID: 12524231]

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[108] Adams MR, Forsyth CJ, Jessup W, Robinson J, Celermajer DS. Oral l-arginine inhibits platelet aggregation but does not enhance endothelium-dependent dilation in healthy young men. J Am Coll Cardiol 1995; 26(4): 1054-61. [http://dx.doi.org/10.1016/0735-1097(95)00257-9] [PMID: 7560599] [109] Morris SM Jr. Regulation of enzymes of urea and arginine synthesis. Annu Rev Nutr 1992; 12(1): 81101. [http://dx.doi.org/10.1146/annurev.nu.12.070192.000501] [PMID: 1503815]

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CHAPTER 13

Citrulline, Nitric Oxide, and Type 2 Diabetes Parvin Mirmiran1,2, Zahra Bahadoran1, Khosrow Kashfi3 and Asghar Ghasemi4,* Nutrition and Endocrine Research Center, Research Institute for Endocrine Sciences, Shahid Beheshti University of Medical Sciences, Tehran, Iran 2 Department of Clinical Nutrition and Human Dietetics, National Nutrition and Food Technology Research Institute, Shahid Beheshti University of Medical Sciences, Tehran, Iran 3 Department of Molecular, Cellular and Biomedical Sciences, Sophie Davis School of Biomedical Education, City University of New York School of Medicine, New York, NY10031, USA 4 Endocrine Physiology Research Center, Research Institute for Endocrine Sciences, Shahid Beheshti University of Medical Sciences, Tehran, Iran 1

Abstract: L-citrulline (Cit), a neutral, non-essential, and non-protein amino acid, is a precursor of L-arginine (Arg) and is involved in nitric oxide (NO) synthesis. Since oral ingestion of Cit can effectively elevate total Arg flux in the entire body and promote NO production, its supplementation has recently received much attention in the realm of cardio-metabolic diseases where NO metabolism is disrupted. Although preliminary data obtained from in vitro and in vivo animal experiments indicates that Cit improves glucose and insulin homeostasis and can effectively prevent hyperglycemia-induced complications such as inflammation, oxidative stress, renal dysfunction, and endothelial dysfunction, these findings are yet to be realized in well-designed longterm clinical studies in patients with type 2 diabetes (T2D). If Cit is shown to be an effective anti-diabetic agent with a good safety profile, its supplementation will be superior to that of Arg because it effectively increases systemic Arg availability more than Arg itself, and hence NO production.

Keywords: Arginine, Arginase, Argininosuccinate Synthase, Argininosuccinate Lyase, Carbamoyl Phosphate Synthetase I, Citrulline, Glutamine, Nitric Oxide, Ornithine Decarboxylase, Ornithine Transcarbamylase, Type 2 Diabetes. Corresponding author Asghar Ghasemi: Endocrine Physiology Research Center, Research Institute for Endocrine Sciences, Shahid Beheshti University of Medical Sciences, Tehran, Iran; No. 24, Erabi Street, Velenjak, Tehran, Iran; Phone: +98 21 22409309; Fax: +98 21 22416264, Email: [email protected]

*

Asghar Ghasemi, Khosrow Kashfi, Zahra Bahadoran (Eds.) All rights reserved-© 2022 Bentham Science Publishers

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INTRODUCTION L-Citrulline (Cit) is a neutral, non-essential, non-protein amino acid, which is best known as an intermediate in the urea cycle but has also garnered interest as a precursor of L-arginine (Arg) synthesis and nitric oxide (NO) production [1]. The name of this amino acid originated from the Citrullus vulgaris (watermelon); it was first isolated in 1914 from watermelon juice, but it was not until 1930 when Mitsunori Wada elucidated its structure and named it ‘citrulline’ [2]. Due to its relatively rare food sources (fresh watermelon containing about 1.6-3.5 g/kg), the amount of Cit provided through usual dietary intakes is somewhat limited. For example, one has to consume about 1-1.5 kg of fresh watermelon to achieve the minimum effective dose of Cit, which is about 3 g [3]. Watermelon rind contains more Cit than flesh watermelon, approximately 24.7 versus 16.7 mg/g dry weight [4]. There is no recommended dietary allowance for Cit [1]. The mean plasma concentration of Cit has been reported to be about 20-47 µM [5 - 10], and whole body Cit flux is estimated to be ~ 8.9 μmol/kg/h (~ 6-10 μmol/kg/h), in healthy human adults in the fasted state [5]. More quantitatively, whole body Cit flux has been estimated to be about 4g/day [11]. The mean concentration of Cit in red blood cells (RBC) was reported as approximately 31±13 μM [10]. Cit is the only precursor of Arg de novo synthesis in the body; the conversion of Cit into Arg occurs in the kidneys, endothelial, and immune cells, as exemplified by activated macrophages [12]. Several studies indicate that Cit raises plasma Arg concentrations and effectively promotes whole-body NO production [3, 12, 13]. Cit augments NO-dependent signaling pathways and exerts beneficial effects in pathologic conditions relating to reductions in NO availability, such as cardiovascular disease and hypertension [3, 12, 13]. Cit appears much more effective than Arg for NO production [14]. Furthermore, oral doses of Arg impose some negative effects, including induction of arginase activity [15, 16] and urea production [17], inhibition of cellular uptake of Cit [18] and recycling of Arg form Cit [16], suppression of endothelial NO synthase (eNOS) expression and activity [19], and induction of cellar oxidative stress [19]. On the other hand, there is evidence indicating the existence of cellular “Arg tolerance” with long-term Arg exposure, a phenomenon that reduces the expected beneficial effects of long-term Arg supplementation [19]. For such reasons, Cit has recently received more attention than Arg as a NO-boosting supplement. This chapter provides an overview of Cit metabolism in the body and its role in whole-body NO production. Then we discuss the efficacy and safety of oral doses of Cit in type 2 diabetes (T2D), a pathological condition of NO-disrupted metabolism.

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CIT BIOSYNTHESIS PATHWAYS Cit biosynthesis is a complex process and involves multiple precursors, enzymes and intracellular, and interorgan substrates transfer. Cit biosynthesis occurs in both the intestine and intra-intestine organs; intestinal biosynthesis is estimated to be responsible for 60-90% of whole plasma Cit flux, whereas extra-intestinal biosynthesis provides a fraction of Cit flux estimated to be as low as 10-30% [20]. Intestinal Biosynthesis of Cit The intestine is the principal site of Cit biosynthesis, and it is the organ that supplies the entire body with Cit [20]. Enteral or plasma amino acids such as Arg, glutamine, glutamate, and proline are responsible for supplying the ornithine used for Cit biosynthesis in the enterocytes [21, 22]. The enzymes involved in the synthesis of ornithine are glutaminase, pyrroline-5-carboxylate synthase, proline oxidase, arginase, and ornithine aminotransferase (OAT), the latter being the key enzyme [21]. The ornithine is finally converted into the Cit by the action of ornithine transcarbamylase (OTC), one of the key enzymes in the urea cycle, which in humans is mainly present in the liver and intestinal mucosa [9]. The presence of the urea cycle enzymes, which are carbamoyl phosphate synthetase I (CPS-I), ornithine decarboxylase (ODC), arginase, argininosuccinate synthase (ASS), and argininosuccinate lyase (ASL) in the enterocytes, provides a biochemical basis for synthesizing Cit and Arg from glutamine [23, 24]. The kinetic properties of the intestinal urea cycle enzymes, optimizing the net synthesis of Cit from glutamine, can explain the large amounts of Cit that are released by the intestine. First, compared to the liver, the intestinal urea cycle enzymes are likely to synthesize Cit rather than urea; second, co-localization of CPS-I and OCT, along with a high activity of OCT in the mitochondria, enables the enterocytes to synthesize Cit from ammonia, HCO3− and ornithine; and third, low activities of the cytosolic ASS and ASL minimize the Cit-Arg conversion and the recycling of Cit into ornithine via arginase in the enterocytes [25]. The extent of contribution of each of the amino acids glutamine, Arg, and proline to the intestinal biosynthesis of Cit is under debate. Initial investigations suggested glutamine as an important precursor (60-80%) for plasma Cit in humans [26, 27]. In healthy adults in the fed state, more than 70% of the 15N label glutamine was found on the α-nitrogen of Cit [5]. About 13-26% of glutamine taken up by the intestines is converted to Cit [27], and the conversion rate has been estimated to be about 5.1±0.7 μmol/kg/h [27]. A significant association is observed between Cit flux and plasma glutamine concentration (r = 0.78) [5].

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Evidence showing increased plasma levels of Cit and Arg after providing glutamine also supports the significant precursor relationship between glutamine, Cit, and Arg [28, 29]. In sepsis, there is reduced production and hence lower plasma concentrations of Cit, the values being 9.9 vs. 28.8 µM, for septic and healthy adults, respectively. Under these toxic conditions, there is also impaired metabolic conversion of glutamine to Cit within the enterocyte, which could be due to decreased glutamine uptake by the enterocyte, increased uptake by the liver, or diverting glutamine to other metabolic pathways [5]. However, some findings [30 - 32] contradict and challenge the conventional view that glutamine is the carbon precursor for synthesizing Arg via the intermediate Cit [33]. In healthy adults in the fed state and using l-[1-13C]glutamine tracer, glutamine contributed to 50% of the carbons in the newly synthesized Arg [30]. In mice, dietary glutamine is a poor carbon skeleton precursor (~0.4%) for the synthesis of Cit [31], and its plasma contribution has been estimated to be about 2.3% and 4.6% in the fed state and fasted-state, respectively [21]. In rats, only 28% of the glutamine nitrogen contributed to the intestinal-released Cit [34]. On the other hand, there is a close direct relationship between glutamine supplementation or depletion and plasma Cit levels [28, 35]. This observation is often used as evidence to support the notion that glutamine is the primary precursor of Cit, further suggesting that glutamine is involved in the overall function and metabolism of enterocytes [36]. Arg is also another important precursor of Cit in the enterocytes, as it is degraded into ornithine through the actions of arginase II and then converted into Cit by the OCT (Fig.(1). Arg is the main precursor for Cit synthesis in mice, providing about 40% of the circulating amounts [31]. In arginase II knockout mice, the rate of Cit appearance in the plasma is reduced, 121 vs. 137 μmol/kg/h, due to the lower availability of ornithine [37]. Accordingly, the contribution of dietary Arg into Cit synthesis was reduced from 45 to 10 μmol/kg/h [37]. In humans, whole body Cit flux and plasma concentrations do not seem to be affected by Arg. The mean flux values of Cit ranged between 10.4 to 13.6 μmol/kg/h in fed and fasted states, respectively, which was similar in both periods of Arg-rich and Arg-free diets [38]. Plasm Cit concentrations remained essentially unchanged, perhaps with a mild decrease trend, following a 6-day Arg-rich diet compared to an Arg-free diet (28.4 vs. 32.0 µM in the fasted state, and 19.0 vs. 25.0 µM in the fed state) [38].

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Fig. (1). Endogenous biosynthesis of Cit, its interorgan exchange, and contribution to nitric oxide production. Cit biosynthesis occurs in both the intestine and intra-intestine organs; intestinal biosynthesis is estimated to be responsible for about 60-90% of whole plasma Cit flux, whereas extra-intestinal biosynthesis provides a fraction of Cit flux, which is as low as 10-30%. The NO-producing cells, such as the macrophages and the endothelial cells, can take up Cit and use it as a substrate to form L-arginine through argininosuccinate synthase (ASS) and argininosuccinate lyase (ASL) and nitric oxide (NO). NOS, NO synthase; OAT, ornithine aminotransferase; OCT, ornithine carbamoyltransferase; ODC, ornithine decarboxylase; P5CR, pyrroline-5-carboxylate reductase. Created with BioRender.com.

The fractional synthesis rate of ornithine and Cit from dietary proline has been estimated to be 22% and 38% in healthy adults human [22]. The estimated conversion rate of proline into Cit is 3.95 μmol/kg/h [22]. The contribution of dietary proline to plasma Cit in mice is quite small, about 3.4% [31]; however, proline has been suggested to be the main precursor of Cit in mammals during the neonatal period [39, 40]. The direct contribution of plasma ornithine to plasma Cit in humans was reported to be as low as 16% (~1.7 μmol/kg/h), which was significantly decreased to 7% (1.2 μmol/kg/h) following an Arg-free diet [38]. Exogenous ornithine administered intravenously or orally could not serve as an effective precursor of plasma Cit [41, 42]. In mice, the contribution of plasma ornithine to plasma Cit has been estimated to be about 33.7% and 43.3% in the fed and fasted states [21].

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Extra-Intestinal Biosynthesis of Cit Another potential source of both intracellular and circulatory Cit is the Arg-NO pathway that is active in the endothelial cells and activated macrophages, in which Cit is recycled through NOS activity; this pathway is known as the Cit-NO cycle. The enzymes NOS, ASL, and ASS are involved in the Cit-NO cycle. NOS activity accounts for the release of Cit into the systemic circulation at a rate of 1 µmol/kg/h [43], which can be compared to splanchnic Cit release of about 1.1 µmol/kg/h [44]. Therefore, systemic NOS activity has been proposed as equally as important as the intestine for systemic Cit supply [44]. DDAH metabolizes about 80-90% of ADMA into Cit and dimethylamine, and a small part (10-20%) is metabolized by aminotransferases and excreted by the kidneys. Since about 250 μmol ADMA is degraded daily by DDAH, this pathway can provide a substantial amount of Cit to the cells. However, in healthy adults, a minor fraction of plasma Cit has been suggested to be supported by this pathway [45]. ADMA is constitutively synthesized during the turnover of methylated Arg residues in proteins [46, 47]. Plasma levels of ADMA in healthy adults have been reported to be less than 0.5 μM [48], but because of its active transport into the cells (via CAT transporters family), cellular levels of ADMA can be as high as 520-fold of that of plasma levels, that is in a range that could tonically inhibit the NOSs [49]. Physiological intracellular concentrations of ADMA (~3.6 μM) exert a modest effect (~10%) on endothelial NO production; however, its elevated levels ranging from 3-9-fold higher could inhibit eNOS-derived NO by about 3070% [50]. As reviewed elsewhere, ADMA has a higher affinity than Arg for both the CAT-1 and CAT-2 transporters and a similar affinity as Arg for other CAT isoforms, e.g., CAT-2B [51]. Both intra- and extracellular levels of ADMA may be substantially elevated upon increased protein methylation or proteolysis, decreased DDAH activity, or decreased CAT activity [49]. Gut-Liver Metabolism of Cit In contrast to ingested Arg, which is subject to relatively high splanchnic uptake (~40-60%) [52] and first-pass metabolism (FPM) within the gut-liver vascular bed, Cit effectively bypasses the FPM and arginase activity [20, 27], facilitating down-stream Cit-Arg recycling and NO production [37]. In the fasted state, the net splanchnic exchange of Cit (differences in the arterial-hepatic venous concentrations of the amino acid × hepatic blood flow) is a negative value (-12 to -13 µmol/min) in healthy subjects [53, 54], which represents a net release of the amino acid into hepatic veins rather than its uptake from the arterial blood and extraction by the splanchnic organs (i.e., gut-liver) [53]. Although it was initially assumed that the liver was totally inert toward Cit passing through its vascular bed

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[20], further studies have suggested that the liver can take up Cit [27]; however, the net hepatic balance of Cit remains close to zero due to similar rates of the active uptake and release [27]. The influx of Cit to the liver (hepatic portal+arterial influx) is estimated at 14.0±0.8 µmol/kg/h, and the absolute rate of Cit uptake by the liver is about 1.3±0.3 µmol/kg/h [27]. These data indicate an exchange between the hepatocyte Cit pool and the hepatic portal pool (Fig. 1). In humans in the fasted state, the liver was found to extract Cit (~ 8.4%) that was released by the intestines [27]; this was dependent on the rate of intestinal Cit release and hepatic Cit influx [44]. Cit is completely targeted to the urea cycle in the liver, and although a substantial amount of Arg may be synthesized within the urea cycle in the hepatocytes, this is hydrolyzed to ornithine and urea with little to no being available as systemic Arg [45]. INTERORGAN EXCHANGE OF CIT AND ARG PRODUCTION The only metabolic fate of Cit in vivo is its conversion to Arg [20]. The kidneys are the major sites of Cit uptake. About 50-80% of Cit released by the intestine is taken up by the kidneys [26, 55] and converted into Arg within the proximal tubule via ASS and ASL. About 75% [20]- 100% [26] of the plasma Cit that is taken up by the kidney has been estimated to be back into the circulation as Arg (Fig. 1). In rats, more than 90% of the renal ASL is located in the cortex, and its activity is 40.6 µmol/h/g of tissue; minor activities were reported within the medulla and papilla, 5.0 and 5.9 µmol/h/g of tissue, respectively [56]. Regardless of the presence of arginase in the kidney, only about 6% of the Cit-derived Arg in the kidney is metabolized by the arginase [56]. The mean renal arterial concentration of Cit was determined as 28.7-35.3 µM, and its net renal uptake and urinary excretion were reported as 5.7-6.9 and 6.0%) compared with those who had normal HbA1C (≤ 6.0%) had a higher plasma Cit levels (35±2.1 vs. 26±1.4 μM) [74]. In a targeted metabolomics study of adult males with self-reported diabetes and healthy controls, a 73.9% increase in plasma levels of Cit was observed in diabetic patients [75]. In contrast, using an untargeted metabolomics approach in a large cohort of females [including 1897 controls, 115 patients with T2D, and 192

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individuals with impaired fasting glucose (IFG)], reduced plasma Cit concentrations were observed in the diabetic patients; higher plasma Cit concentrations were also associated with significantly decreased risk of both diabetes and IFG (OR=0.54, 95% CI=0.42-0.71 and OR=0.83, 95% CI= 0.790.99) [76]. Such inconsistent findings may be related to sex differences in Cit metabolism, the stage of T2D, or renal function status in diabetic patients (the ability of the kidneys to convert Cit to Arg). Evidence indicates that treatment of patients with T2D with the insulin-sensitizing agents, either metformin or pioglitazone, may result in reductions in serum Cit concentrations [77]; a negative association between serum Cit levels and metformin treatment was observed in both human cross-sectional (β= -0.79, 95% CI= -1.15, -0.43) and 7-year follow-up (β= -0.61, 95% CI= -0.94, -0.28) metabolomics studies [77]. Metformin treatment of T2D mice also resulted in reduced concentrations of plasma Cit and Cit levels in the skeletal muscle and epididymal adipose tissue, but not in the liver [77]. In humans, three months of treatment with pioglitazone (45 mg daily) plus metformin (1000 mg twice daily) significantly decreased plasma Cit concentrations (95% CI= -12.2, -7.1) [78]. The decreased Cit levels in the plasma and metabolically active organs following metformin treatment are attributed to AMPK-induced eNOS activation by metformin, promoting Cit utilization in the Cit-Arg-NO pathway [77]. Injections of insulin similarly reduced plasma Cit levels by 56% (95% CI= -45%, -37%) [78]; the underlying mechanism for this effect has yet to be determined. To sum up, available data suggests that Cit metabolism is changed in T2D; it depends on the stage of the disease, the status of glycemic control, and renal function. In addition, plasma levels of Cit may be decreased or increased compared to normal. Treatment of diabetic patients with insulin-sensitizing drugs and insulin itself decreases plasma Cit levels, probably through inducing NOS activity. Together, these findings support the notion that Cit might be a promising complementary addition in the treatment of T2D. Cit Supplementation, T2D, and its Complications Although preliminary data from in vitro and in vivo animal studies indicates that Cit improves glucose and insulin homeostasis and can effectively prevent hyperglycemia-induced complications, such as inflammation, oxidative stress, and endothelial dysfunction, these findings remain to be addressed by long-term clinical human studies. In diabetes, Cit can effectively regulate NO synthesis and cytokine production in the macrophages [79]. In the absence of Arg, treatment of peritoneal macrophages obtained from Zucker diabetic obese rats with Cit completely restored NO

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synthesis (disrupted in the diabetic animals), decreased TNF-α, and increased IL-6 production [79]. These observations suggest that in diabetes, Cit may improve macrophage activity since IL-6 has a critical role in insulin regulation and glucose homeostasis; furthermore, it improves insulin sensitivity by decreasing the diabetes-induced low-grade pro-inflammatory state [80, 81]. Cit seems to promote cellular NO synthesis in a controlled manner since NO production in the macrophages does not increase further at higher Cit concentrations (> 0.1 mM) [79]. Treatment of high-glucose-incubated endothelial cells (human umbilical vein endothelial cells, HUVECs) with Cit (at a concentration of 300 µM) restored cellular NO production by inhibiting the effect of high-glucose on eNOS expression, eNOS phosphorylation at serine 1177, and arginase II expression [82]. Cit also normalized telomerase activity levels, prevented glucose-induced reactive oxygen species (ROS) generation and DNA damage, and reversed glucoseinduced senescence of the endothelial cells [82]. Similarly, in dyslipidemic T2D rats (induced by high-fat diet), 4-week oral ingestion of Cit effectively restored plasma NO levels and prevented aortic senescence, which is a widely used marker of cellular senescence, senescence-associated β-galactosidase, SA-β-gal [82]. These findings suggest that Cit administration can successfully retard endothelial senescence and reduces endothelial dysfunction induced by high-glucose conditions [82]. Cit supplementation through drinking water at 0.5 g/kg/day to obese-diabetic KKAy mice and rats on a high-fat diet decreased body weight and fat mass and decreased circulating levels of free fatty acid insulin [83]. In these models, Cit also decreased food intake by increasing hypothalamic levels of proopiomelanocortin (POMC), a food intake suppression peptide [83]. Beyond providing available substrate for the NOS enzymes, Cit can also potentiate the Arg-NO pathway by inhibiting arginase, which acts as a potent competitor of NOSs for the substrate and limiting the antagonizing effects of ADMA on the NOSs. T2D is related to a pathological elevated arginase activity, which decreases Arg availability for eNOS, and impairs endothelial cell NO production and the whole body NO levels [84]. Therefore, the potential effects of treatments at targeting arginase activity in patients with T2D have received much attention [85, 86]. Both experimental and clinical studies indicate that Cit effectively reduces plasma arginase activity in high-glucose concentrations. Cit (100 µM) completely prevented arginase overactivity induced under high-glucose conditions in bovine aortic endothelial cells (BAECs); in this experiment, incubation of BAECs with 25 mM glucose for 72

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hours caused a 2-fold increase in arginase activity and decreased NO production by 40% [87]. Supplementation with a dose of 2 g/day Cit for 1 month also decreased arginase activity by 30% in patients with T2D [87]. Cit can also offset the antagonized effects of ADMA on eNOS activity [88]; treatment of ADMAincubated porcine coronary artery endothelium with Cit (at a concentration of 100 µM) effectively preserved eNOS activity and restored NO production by 86% [89]. CONCLUDING REMARKS The potential ability of Cit to promote Arg bioavailability without harmful side effects highlights the importance of Cit as a precursor of Arg and NO. The priority of Cit in supplying Arg to the NOSs and NO synthesis is attributed to its capability to bypass the gut-liver metabolism. Compared to Arg, ingested doses of Cit are absorbed more efficiently, with a low FPM and high renal reabsorption that enable Cit to be more efficient than Arg itself for increasing Arg flux. Furthermore, the elevated arginase activity in T2D limits Arg therapy in patients and may even further induce and/or enhance arginase activity. In contrast, Cit supplementation can be suggested as a promising alternative treatment because of its capability to bypass the arginase activity. CONSENT FOR PUBLICATION Not applicable. CONFLICT OF INTEREST The author declares no conflict of interest, financial or otherwise. ACKNOWLEDGEMENT Declared none. REFERENCES [1]

Luiking YC, Castillo L, Deutz NE. Arginine, citrulline, and nitric oxide. Modern Nutrition in Health and Disease: Eleventh Edition: Wolters Kluwer Health Adis (ESP) 2012; 477-86.

[2]

Fragkos KC, Forbes A. Was citrulline first a laxative substance? The truth about modern citrulline and its isolation. Nippon Ishigaku Zasshi 2011; 57(3): 275-92. [PMID: 22397107]

[3]

Allerton T, Proctor D, Stephens J, Dugas T, Spielmann G, Irving B. l-Citrulline Supplementation: Impact on Cardiometabolic Health. Nutrients 2018; 10(7): 921. [http://dx.doi.org/10.3390/nu10070921] [PMID: 30029482]

[4]

Rimando AM, Perkins-Veazie PM. Determination of citrulline in watermelon rind. J Chromatogr A 2005; 1078(1-2): 196-200. [http://dx.doi.org/10.1016/j.chroma.2005.05.009] [PMID: 16007998]

Citrulline, NO and T2D

The Role of Nitric Oxide in Type 2 Diabetes 297

[5]

Kao C, Hsu J, Bandi V, Jahoor F. Alterations in glutamine metabolism and its conversion to citrulline in sepsis. Am J Physiol Endocrinol Metab 2013; 304(12): E1359-64. [http://dx.doi.org/10.1152/ajpendo.00628.2012] [PMID: 23612995]

[6]

Crenn P, Coudray-Lucas C, Thuillier F, Cynober L, Messing B. Postabsorptive plasma citrulline concentration is a marker of absorptive enterocyte mass and intestinal failure in humans. Gastroenterology 2000; 119(6): 1496-505. [http://dx.doi.org/10.1053/gast.2000.20227] [PMID: 11113071]

[7]

El-Hattab AW, Hsu JW, Emrick LT, et al. Restoration of impaired nitric oxide production in MELAS syndrome with citrulline and arginine supplementation. Mol Genet Metab 2012; 105(4): 607-14. [http://dx.doi.org/10.1016/j.ymgme.2012.01.016] [PMID: 22325939]

[8]

Nagasaka H, Yorifuji T, Egawa H, et al. Characteristics of NO cycle coupling with urea cycle in nonhyperammonemic carriers of ornithine transcarbamylase deficiency. Mol Genet Metab 2013; 109(3): 251-4. [http://dx.doi.org/10.1016/j.ymgme.2013.04.013] [PMID: 23669167]

[9]

Curis E, Nicolis I, Moinard C, et al. Almost all about citrulline in mammals. Amino Acids 2005; 29(3): 177-205. [http://dx.doi.org/10.1007/s00726-005-0235-4] [PMID: 16082501]

[10]

Rougé C, Des Robert C, Robins A, Le Bacquer O, De La Cochetière MF, Darmaun D. Determination of citrulline in human plasma, red blood cells and urine by electron impact (EI) ionization gas chromatography–mass spectrometry. J Chromatogr B Analyt Technol Biomed Life Sci 2008; 865(12): 40-7. [http://dx.doi.org/10.1016/j.jchromb.2008.01.055] [PMID: 18329346]

[11]

van de Poll MCG, Soeters PB, Deutz NEP, Fearon KCH, Dejong CHC. Renal metabolism of amino acids: its role in interorgan amino acid exchange. Am J Clin Nutr 2004; 79(2): 185-97. [http://dx.doi.org/10.1093/ajcn/79.2.185] [PMID: 14749222]

[12]

Bahri S, Zerrouk N, Aussel C, et al. Citrulline: From metabolism to therapeutic use. Nutrition 2013; 29(3): 479-84. [http://dx.doi.org/10.1016/j.nut.2012.07.002] [PMID: 23022123]

[13]

Papadia C, Osowska S, Cynober L, Forbes A. Citrulline in health and disease. Review on human studies. Clin Nutr 2017. [PMID: 29107336]

[14]

Schwedhelm E, Maas R, Freese R, et al. Pharmacokinetic and pharmacodynamic properties of oral Lcitrulline and L-arginine: impact on nitric oxide metabolism. Br J Clin Pharmacol 2008; 65(1): 51-9. [http://dx.doi.org/10.1111/j.1365-2125.2007.02990.x] [PMID: 17662090]

[15]

Morris SM Jr. Regulation of enzymes of urea and arginine synthesis. Annu Rev Nutr 1992; 12(1): 81101. [http://dx.doi.org/10.1146/annurev.nu.12.070192.000501] [PMID: 1503815]

[16]

Cynober L, Boucher JL, Vasson MP. Arginine metabolism in mammals. J Nutr Biochem 1995; 6(8): 402-13. [http://dx.doi.org/10.1016/0955-2863(95)00066-9]

[17]

Adams MR, Forsyth CJ, Jessup W, Robinson J, Celermajer DS. Oral l-arginine inhibits platelet aggregation but does not enhance endothelium-dependent dilation in healthy young men. J Am Coll Cardiol 1995; 26(4): 1054-61. [http://dx.doi.org/10.1016/0735-1097(95)00257-9] [PMID: 7560599]

[18]

Bahri S, Curis E, El Wafi FZ, et al. Mechanisms and kinetics of citrulline uptake in a model of human intestinal epithelial cells. Clin Nutr 2008; 27(6): 872-80. [http://dx.doi.org/10.1016/j.clnu.2008.08.003] [PMID: 18834650]

[19]

Mohan S, Wu CC, Shin S, Fung HL. Continuous exposure to l-arginine induces oxidative stress and

298 The Role of Nitric Oxide in Type 2 Diabetes

Mirmiran et al.

physiological tolerance in cultured human endothelial cells. Amino Acids 2012; 43(3): 1179-88. [http://dx.doi.org/10.1007/s00726-011-1173-y] [PMID: 22130739] [20]

Windmueller HG, Spaeth AE. Source and fate of circulating citrulline. Am J Physiol 1981; 241(6): E473-80. [PMID: 7325229]

[21]

Marini JC. Arginine and ornithine are the main precursors for citrulline synthesis in mice. J Nutr 2012; 142(3): 572-80. [http://dx.doi.org/10.3945/jn.111.153825] [PMID: 22323761]

[22]

Tomlinson C, Rafii M, Ball RO, Pencharz PB. Arginine can be synthesized from enteral proline in healthy adult humans. J Nutr 2011; 141(8): 1432-6. [http://dx.doi.org/10.3945/jn.110.137224] [PMID: 21677074]

[23]

Wu G, Knabe DA. Arginine synthesis in enterocytes of neonatal pigs. Am J Physiol 1995; 269(3 Pt 2): R621-9. [PMID: 7573565]

[24]

Wu G, Knabe DA, Flynn NE. Synthesis of citrulline from glutamine in pig enterocytes. Biochem J 1994; 299(1): 115-21. [http://dx.doi.org/10.1042/bj2990115] [PMID: 8166628]

[25]

Davis PK, Wu G. Compartmentation and kinetics of urea cycle enzymes in porcine enterocytes. Comp Biochem Physiol B Biochem Mol Biol 1998; 119(3): 527-37. [http://dx.doi.org/10.1016/S0305-0491(98)00014-5] [PMID: 9734336]

[26]

Ligthart-Melis GC, van de Poll MCG, Boelens PG, Dejong CHC, Deutz NEP, van Leeuwen PAM. Glutamine is an important precursor for de novo synthesis of arginine in humans. Am J Clin Nutr 2008; 87(5): 1282-9. [http://dx.doi.org/10.1093/ajcn/87.5.1282] [PMID: 18469251]

[27]

Van De Poll MCG, Ligthart-Melis GC, Boelens PG, Deutz NEP, Van Leeuwen PAM, Dejong CHC. Intestinal and hepatic metabolism of glutamine and citrulline in humans. J Physiol 2007; 581(2): 81927. [http://dx.doi.org/10.1113/jphysiol.2006.126029] [PMID: 17347276]

[28]

Rougé C, Des Robert C, Robins A, et al. Manipulation of citrulline availability in humans. Am J Physiol Gastrointest Liver Physiol 2007; 293(5): G1061-7. [http://dx.doi.org/10.1152/ajpgi.00289.2007] [PMID: 17901164]

[29]

Rutten EP, Engelen MP, Wouters EF, Schols AM, Deutz NE. Metabolic effects of glutamine and glutamate ingestion in healthy subjects and in persons with chronic obstructive pulmonary disease. Am J Clin Nutr 2006; 83(1): 115-23. [PMID: 16400059]

[30]

Tomlinson C, Rafii M, Ball RO, Pencharz P. Arginine synthesis from enteral glutamine in healthy adults in the fed state. Am J Physiol Endocrinol Metab 2011; 301(2): E267-73. [http://dx.doi.org/10.1152/ajpendo.00006.2011] [PMID: 21540446]

[31]

Marini JC, Didelija IC, Castillo L, Lee B. Glutamine: precursor or nitrogen donor for citrulline synthesis? Am J Physiol Endocrinol Metab 2010; 299(1): E69-79. [http://dx.doi.org/10.1152/ajpendo.00080.2010] [PMID: 20407005]

[32]

Marini JC. Interrelationships between glutamine and citrulline metabolism. Curr Opin Clin Nutr Metab Care 2016; 19(1): 62-6. [http://dx.doi.org/10.1097/MCO.0000000000000233] [PMID: 26560519]

[33]

Ligthart-Melis GC, Deutz NEP. Is glutamine still an important precursor of citrulline? Am J Physiol Endocrinol Metab 2011; 301(2): E264-6. [http://dx.doi.org/10.1152/ajpendo.00223.2011] [PMID: 21558548]

[34]

Windmueller HG, Spaeth AE. Respiratory fuels and nitrogen metabolism in vivo in small intestine of

Citrulline, NO and T2D

The Role of Nitric Oxide in Type 2 Diabetes 299

fed rats. Quantitative importance of glutamine, glutamate, and aspartate. J Biol Chem 1980; 255(1): 107-12. [http://dx.doi.org/10.1016/S0021-9258(19)86270-1] [PMID: 7350142] [35]

Ziegler TR, Benfell K, Smith RJ, et al. Safety and metabolic effects of L-glutamine administration in humans. JPEN J Parenter Enteral Nutr 1990; 14(4_suppl) (Suppl.): 137S-46S. [http://dx.doi.org/10.1177/0148607190014004201] [PMID: 2119459]

[36]

Kim MH, Kim H. The Roles of Glutamine in the Intestine and Its Implication in Intestinal Diseases. Int J Mol Sci 2017; 18(5): 1051. [http://dx.doi.org/10.3390/ijms18051051] [PMID: 28498331]

[37]

Agarwal U, Didelija IC, Yuan Y, Wang X, Marini JC. Supplemental Citrulline Is More Efficient Than Arginine in Increasing Systemic Arginine Availability in Mice. J Nutr 2017; 147(4): 596-602. [http://dx.doi.org/10.3945/jn.116.240382] [PMID: 28179487]

[38]

Castillo L, Sánchez M, Vogt J, et al. Plasma arginine, citrulline, and ornithine kinetics in adults, with observations on nitric oxide synthesis. Am J Physiol 1995; 268(2 Pt 1): E360-7. [PMID: 7864114]

[39]

Dillon EL, Knabe DA, Wu G. Lactate inhibits citrulline and arginine synthesis from proline in pig enterocytes. Am J Physiol 1999; 276(5): G1079-86. [PMID: 10329997]

[40]

Tomlinson C, Rafii M, Sgro M, Ball RO, Pencharz P. Arginine is synthesized from proline, not glutamate, in enterally fed human preterm neonates. Pediatr Res 2011; 69(1): 46-50. [http://dx.doi.org/10.1203/PDR.0b013e3181fc6ab7] [PMID: 20856169]

[41]

Eriksson LS, Reihnér E, Wahren J. Infusion of ornithine-alpha-ketoglutarate in healthy subjects: Effects on protein metabolism. Clin Nutr 1985; 4(2): 73-6. [http://dx.doi.org/10.1016/0261-5614(85)90045-7] [PMID: 16831709]

[42]

Cynober L, Coudray-Lucas C, de Bandt JP, et al. Action of ornithine alpha-ketoglutarate, ornithine hydrochloride, and calcium alpha-ketoglutarate on plasma amino acid and hormonal patterns in healthy subjects. J Am Coll Nutr 1990; 9(1): 2-12. [http://dx.doi.org/10.1080/07315724.1990.10720343] [PMID: 2407764]

[43]

Castillo L, Beaumier L, Ajami AM, Young VR. Whole body nitric oxide synthesis in healthy men determined from [15N] arginine-to-[15N]citrulline labeling. Proc Natl Acad Sci USA 1996; 93(21): 11460-5. [http://dx.doi.org/10.1073/pnas.93.21.11460] [PMID: 8876157]

[44]

van de Poll MCG, Siroen MPC, van Leeuwen PAM, et al. Interorgan amino acid exchange in humans: consequences for arginine and citrulline metabolism. Am J Clin Nutr 2007; 85(1): 167-72. [http://dx.doi.org/10.1093/ajcn/85.1.167] [PMID: 17209193]

[45]

Morris SM Jr. Arginine metabolism in vascular biology and disease. Vasc Med 2005; 10(1_suppl) (Suppl. 1): S83-7. [http://dx.doi.org/10.1177/1358836X0501000112] [PMID: 16444873]

[46]

Kielstein JT, Fliser D, Veldink H. Asymmetric dimethylarginine and symmetric dimethylarginine: axis of evil or useful alliance? Semin Dial 2009; 22(4): 346-50. [http://dx.doi.org/10.1111/j.1525-139X.2009.00578.x] [PMID: 19708979]

[47]

Fulton MD, Brown T, Zheng YG. The Biological Axis of Protein Arginine Methylation and Asymmetric Dimethylarginine. Int J Mol Sci 2019; 20(13): 3322. [http://dx.doi.org/10.3390/ijms20133322] [PMID: 31284549]

[48]

Fleszar MG, Wiśniewski J, Krzystek-Korpacka M, et al. Quantitative Analysis of l-Arginine, Dimethylated Arginine Derivatives, l-Citrulline, and Dimethylamine in Human Serum Using Liquid Chromatography–Mass Spectrometric Method. Chromatographia 2018; 81(6): 911-21. [http://dx.doi.org/10.1007/s10337-018-3520-6] [PMID: 29887621]

300 The Role of Nitric Oxide in Type 2 Diabetes

Mirmiran et al.

[49]

Teerlink T, Luo Z, Palm F, Wilcox CS. Cellular ADMA: Regulation and action. Pharmacol Res 2009; 60(6): 448-60. [http://dx.doi.org/10.1016/j.phrs.2009.08.002] [PMID: 19682580]

[50]

Cardounel AJ, Cui H, Samouilov A, et al. Evidence for the pathophysiological role of endogenous methylarginines in regulation of endothelial NO production and vascular function. J Biol Chem 2007; 282(2): 879-87. [http://dx.doi.org/10.1074/jbc.M603606200] [PMID: 17082183]

[51]

Arrigoni F, Ahmetaj B, Leiper J. The biology and therapeutic potential of the DDAH/ADMA pathway. Curr Pharm Des 2010; 16(37): 4089-102. [http://dx.doi.org/10.2174/138161210794519246] [PMID: 21247398]

[52]

Castillo L, Chapman TE, Yu YM, Ajami A, Burke JF, Young VR. Dietary arginine uptake by the splanchnic region in adult humans. Am J Physiol 1993; 265(4 Pt 1): E532-9. [PMID: 8238326]

[53]

Deferrari G, Garibotto G, Robaudo C, Sala M, Tizianello A. Splanchnic exchange of amino acids after amino acid ingestion in patients with chronic renal insufficiency. Am J Clin Nutr 1988; 48(1): 72-83. [http://dx.doi.org/10.1093/ajcn/48.1.72] [PMID: 3291599]

[54]

Clemmesen JO, Kondrup J, Ott P. Splanchnic and leg exchange of amino acids and ammonia in acute liver failure. Gastroenterology 2000; 118(6): 1131-9. [http://dx.doi.org/10.1016/S0016-5085(00)70366-0] [PMID: 10833488]

[55]

Barbul A. Arginine: biochemistry, physiology, and therapeutic implications. JPEN J Parenter Enteral Nutr 1986; 10(2): 227-38. [http://dx.doi.org/10.1177/0148607186010002227] [PMID: 3514981]

[56]

Dhanakoti SN, Brosnan JT, Herzberg GR, Brosnan ME. Renal arginine synthesis: studies in vitro and in vivo. Am J Physiol 1990; 259(3 Pt 1): E437-42. [PMID: 1975989]

[57]

Tizianello A, Deferrari G, Garibotto G, Robaudo C, Salvidio G, Saffioti S. Renal ammoniagenesis in the postprandial period. Contrib Nephrol 1985; 47: 44-57. [http://dx.doi.org/10.1159/000411208] [PMID: 4064700]

[58]

Tizianello A, De Ferrari G, Garibotto G, Gurreri G, Robaudo C. Renal metabolism of amino acids and ammonia in subjects with normal renal function and in patients with chronic renal insufficiency. J Clin Invest 1980; 65(5): 1162-73. [http://dx.doi.org/10.1172/JCI109771] [PMID: 7364943]

[59]

Lau T, Owen W, Yu YM, et al. Arginine, citrulline, and nitric oxide metabolism in end-stage renal disease patients. J Clin Invest 2000; 105(9): 1217-25. [http://dx.doi.org/10.1172/JCI7199] [PMID: 10791996]

[60]

Wu G, Morris SM Jr. Arginine metabolism: nitric oxide and beyond. 1998. [http://dx.doi.org/10.1042/bj3360001]

[61]

Kim IY, Schutzler SE, Schrader A, et al. Acute ingestion of citrulline stimulates nitric oxide synthesis but does not increase blood flow in healthy young and older adults with heart failure. Am J Physiol Endocrinol Metab 2015; 309(11): E915-24. [http://dx.doi.org/10.1152/ajpendo.00339.2015] [PMID: 26442881]

[62]

Oyadomari S, Gotoh T, Aoyagi K, Araki E, Shichiri M, Mori M. Coinduction of endothelial nitric oxide synthase and arginine recycling enzymes in aorta of diabetic rats. 2001. [http://dx.doi.org/10.1006/niox.2001.0344]

[63]

Mori M, Gotoh T. Regulation of nitric oxide production by arginine metabolic enzymes. Biochem Biophys Res Commun 2000; 275(3): 715-9. [http://dx.doi.org/10.1006/bbrc.2000.3169] [PMID: 10973788]

Citrulline, NO and T2D

The Role of Nitric Oxide in Type 2 Diabetes 301

[64]

Flam BR, Eichler DC, Solomonson LP. Endothelial nitric oxide production is tightly coupled to the citrulline-NO cycle. 2007. [http://dx.doi.org/10.1016/j.niox.2007.07.001]

[65]

Wileman SM, Mann GE, Pearson JD, Baydoun AR. Role of L -citrulline transport in nitric oxide synthesis in rat aortic smooth muscle cells activated with LPS and interferon- γ. Br J Pharmacol 2003; 140(1): 179-85. [http://dx.doi.org/10.1038/sj.bjp.0705407] [PMID: 12967947]

[66]

Nussler AK, Billiar TR, Liu ZZ, Morris SM Jr. Coinduction of nitric oxide synthase and argininosuccinate synthetase in a murine macrophage cell line. Implications for regulation of nitric oxide production. J Biol Chem 1994; 269(2): 1257-61. [http://dx.doi.org/10.1016/S0021-9258(17)42251-4] [PMID: 7507106]

[67]

Bryk J, Ochoa JB, Correia MITD, Munera-Seeley V, Popovic PJ. Effect of citrulline and glutamine on nitric oxide production in RAW 264.7 cells in an arginine-depleted environment. JPEN J Parenter Enteral Nutr 2008; 32(4): 377-83. [http://dx.doi.org/10.1177/0148607108319807] [PMID: 18596308]

[68]

Erez A, Nagamani SCS, Shchelochkov OA, et al. Requirement of argininosuccinate lyase for systemic nitric oxide production. Nat Med 2011; 17(12): 1619-26. [http://dx.doi.org/10.1038/nm.2544] [PMID: 22081021]

[69]

Simon A, Plies L, Habermeier A, Martiné U, Reining M, Closs EI. Role of neutral amino acid transport and protein breakdown for substrate supply of nitric oxide synthase in human endothelial cells. Circ Res 2003; 93(9): 813-20. [http://dx.doi.org/10.1161/01.RES.0000097761.19223.0D] [PMID: 14512444]

[70]

Baydoun AR, Bogle RG, Pearson JD, Mann GE. Discrimination between citrulline and arginine transport in activated murine macrophages: inefficient synthesis of NO from recycling of citrulline to arginine. Br J Pharmacol 1994; 112(2): 487-92. [http://dx.doi.org/10.1111/j.1476-5381.1994.tb13099.x] [PMID: 8075867]

[71]

Vadgama JV, Evered DF. Characteristics of L-citrulline transport across rat small intestine in vitro. Pediatr Res 1992; 32(4): 472-8. [http://dx.doi.org/10.1203/00006450-199210000-00019] [PMID: 1437402]

[72]

Moinard C, Nicolis I, Neveux N, Darquy S, Bénazeth S, Cynober L. Dose-ranging effects of citrulline administration on plasma amino acids and hormonal patterns in healthy subjects: the Citrudose pharmacokinetic study. Br J Nutr 2008; 99(4): 855-62. [http://dx.doi.org/10.1017/S0007114507841110] [PMID: 17953788]

[73]

Sailer M, Dahlhoff C, Giesbertz P, Eidens MK, de Wit N, Rubio-Aliaga I, et al. Increased plasma citrulline in mice marks diet-induced obesity and may predict the development of the metabolic syndrome. 2013. [http://dx.doi.org/10.1371/journal.pone.0063950]

[74]

Verdam FJ, Greve JWM, Roosta S, et al. Small intestinal alterations in severely obese hyperglycemic subjects. J Clin Endocrinol Metab 2011; 96(2): E379-83. [http://dx.doi.org/10.1210/jc.2010-1333] [PMID: 21084402]

[75]

Suhre K, Meisinger C, Döring A, Altmaier E, Belcredi P, Gieger C, et al. Metabolic footprint of diabetes: a multiplatform metabolomics study in an epidemiological setting. 2010. [http://dx.doi.org/10.1371/journal.pone.0013953]

[76]

Menni C, Fauman E, Erte I, et al. Biomarkers for type 2 diabetes and impaired fasting glucose using a nontargeted metabolomics approach. Diabetes 2013; 62(12): 4270-6. [http://dx.doi.org/10.2337/db13-0570] [PMID: 23884885]

[77]

Adam J, Brandmaier S, Troll M, et al. Metformin effect on nontargeted metabolite profiles in patients with type 2 diabetes and in multiple murine tissues. Diabetes 2016; 65: 3776-3785. Diabetes 2017;

302 The Role of Nitric Oxide in Type 2 Diabetes

Mirmiran et al.

66(5): e3-4. [http://dx.doi.org/10.2337/dbi17-0010] [PMID: 28507216] [78]

Irving BA, Carter RE, Soop M, et al. Effect of insulin sensitizer therapy on amino acids and their metabolites. Metabolism 2015; 64(6): 720-8. [http://dx.doi.org/10.1016/j.metabol.2015.01.008] [PMID: 25733201]

[79]

Breuillard C, Bonhomme S, Couderc R, Cynober L, De Bandt JP. In vitro anti-inflammatory effects of citrulline on peritoneal macrophages in Zucker diabetic fatty rats. Br J Nutr 2015; 113(1): 120-4. [http://dx.doi.org/10.1017/S0007114514002086] [PMID: 25391524]

[80]

Matthews VB, Allen TL, Risis S, et al. Interleukin-6-deficient mice develop hepatic inflammation and systemic insulin resistance. Diabetologia 2010; 53(11): 2431-41. [http://dx.doi.org/10.1007/s00125-010-1865-y] [PMID: 20697689]

[81]

Sadagurski M, Norquay L, Farhang J, D’Aquino K, Copps K, White MF. Human IL6 enhances leptin action in mice. Diabetologia 2010; 53(3): 525-35. [http://dx.doi.org/10.1007/s00125-009-1580-8] [PMID: 19902173]

[82]

Tsuboi T, Maeda M, Hayashi T. Administration of L-arginine plus L-citrulline or L-citrulline alone successfully retarded endothelial senescence. 2018. [http://dx.doi.org/10.1371/journal.pone.0192252]

[83]

Kudo M, Yoshitomi H, Momoo M, Suguro S, Yamagishi Y, Gao M. Evaluation of the Effects and Mechanism of L-Citrulline on Anti-obesity by Appetite Suppression in Obese/Diabetic KK-Ay Mice and High-Fat Diet Fed SD Rats. Biol Pharm Bull 2017; 40(4): 524-30. [http://dx.doi.org/10.1248/bpb.b16-01002] [PMID: 28381807]

[84]

Shatanawi A, Momani MS. Plasma arginase activity is elevated in type 2 diabetic patients. Biomed Res 2017; 28(9): 4102-6.

[85]

Shemyakin A, Kövamees O, Rafnsson A, et al. Arginase inhibition improves endothelial function in patients with coronary artery disease and type 2 diabetes mellitus. Circulation 2012; 126(25): 2943-50. [http://dx.doi.org/10.1161/CIRCULATIONAHA.112.140335] [PMID: 23183942]

[86]

Kövamees O, Shemyakin A, Checa A, et al. Arginase Inhibition Improves Microvascular Endothelial Function in Patients With Type 2 Diabetes Mellitus. J Clin Endocrinol Metab 2016; 101(11): 3952-8. [http://dx.doi.org/10.1210/jc.2016-2007] [PMID: 27399350]

[87]

Shatanawi A, Momani MS, Aqtash R, Hamdan MH, Caldwell RB, Caldwell RW. Abstract 15199: LCitrulline Supplementation Reduces Plasma Arginase Activity in Type 2 Diabetes Patients. Circulation. 2015; 132(suppl_3): A15199-A.

[88]

McCarty M. Asymmetric Dimethylarginine Is a Well Established Mediating Risk Factor for Cardiovascular Morbidity and Mortality—Should Patients with Elevated Levels Be Supplemented with Citrulline? Healthcare (Basel) 2016; 4(3): 40. [http://dx.doi.org/10.3390/healthcare4030040] [PMID: 27417628]

[89]

Xuan C, Lun LM, Zhao JX, et al. L-citrulline for protection of endothelial function from ADMA–induced injury in porcine coronary artery. Sci Rep 2015; 5(1): 10987. [http://dx.doi.org/10.1038/srep10987] [PMID: 26046576]

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CHAPTER 14

Nitrate, Nitrite and Type 2 Diabetes Zahra Bahadoran1, Parvin Mirmiran1,2, Khosrow Kashfi3 and Asghar Ghasemi4 Nutrition and Endocrine Research Center, Research Institute for Endocrine Sciences, Shahid Beheshti University of Medical Sciences, Tehran, Iran 2 Department of Clinical Nutrition and Human Dietetics, National Nutrition and Food Technology Research Institute, Shahid Beheshti University of Medical Sciences, Tehran, Iran 3 Department of Molecular, Cellular, and Biomedical Sciences, Sophie Davis School of Biomedical Education, City University of New York School of Medicine, New York, NY10031, USA 4 Endocrine Physiology Research Center, Research Institute for Endocrine Sciences, Shahid Beheshti University of Medical Sciences, Tehran, Iran 1

Abstract: Recent research punctuates that the nitrate (NO3)-nitrite (NO2)-nitric oxide (NO) pathway may be a potential therapeutic target in type 2 diabetes (T2D), a NOdisrupted metabolic disorder. Nutritional aspects of the NO3-NO2-NO pathway has been highlighted by focusing on the protective effects of some traditional high-NO3 diet, such as Mediterranean and DASH (Dietary Approaches to Stop Hypertension) diets and their NO3-rich components, i.e., fruits, vegetables, legumes, and green leafy vegetables, against the development of T2D. Both acute and long-term administration of inorganic NO3 and NO2 in animal experiments display anti-diabetic properties; inorganic NO3 decreases fasting blood glucose, glycosylated hemoglobin, and proinsulin to insulin ratio and improves glucose tolerance. In contrast to animal experiments, NO3/NO2 therapy has failed to show anti-diabetic properties and beneficial effects on glucose and insulin homeostasis in humans. This lost-i-translation remains an open question, and long-term clinical trials are needed to confirm the salutary effects of inorganic NO3 and NO2 as the natural NO boosters in patients with T2D.

Keywords: Acceptable Daily Intake, Insulin Resistance, Hypertension, Metabolic Syndrome, Nitric Oxide, Nitric Oxide Synthase, Nitrate, Nitrite, Type 2 Diabetes.

Corresponding author Asghar Ghasemi: Endocrine Physiology Research Center, Research Institute for Endocrine Sciences, Shahid Beheshti University of Medical Sciences, Tehran, Iran; No. 24, Erabi Street, Velenjak, Tehran, Iran; Phone: +98 21 22409309; Fax: +98 21 22416264, Email: [email protected]

*

Asghar Ghasemi, Khosrow Kashfi, Zahra Bahadoran (Eds.) All rights reserved-© 2022 Bentham Science Publishers

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INTRODUCTION Inorganic nitrate (NO3) and nitrite (NO2) can act as a substrate or backup system for non-enzymatic endogenous generation of nitric oxide (NO), and current data indicate that both NO3 and NO2 display NO-like bioactivity [1, 2]. The ability of inorganic NO3-NO2 to convert to NO highlights the physiological importance and novel aspects of the pathway in health and disease [3]. Boosting the NO3-NO2-NO pathway, where the classic L-arginine-NO pathway is compromised, has therefore become an attractive approach for potential prevention and treatment of cardiometabolic diseases, including hypertension (HTN), metabolic syndrome (MetS), and T2D [4, 5]. Both in vitro and in vivo animal experiments greatly support the hypothesis that the NO3-NO2-NO pathway plays a critical role in regulating glucose and insulin metabolism and insulin signaling [6 - 8]. Supplementation with inorganic NO3NO2 in animal models of T2D resulted in improved hyperglycemia, insulin sensitivity, and glucose tolerance; their supplementation was also accompanied by elevated pancreatic islet insulin content and insulin secretion, improved inflammation, dyslipidemia, liver steatosis, and oxidative stress [9 - 11]. Favorable effects of NO3 therapy on glucose and insulin homeostasis have been reported to be head-to-head with metformin, the first-line anti-diabetic agent [12]. In animal experiments, NO3 had equipotent anti-diabetic effects compared to metformin, while it was superior to protecting against diabetes-induced cardiovascular dysfunction and liver steatosis [12]. Although the beneficial effects of inorganic NO3-NO2 supplementation have received increasing appreciation in animal experiments, their efficacy on glucose and insulin homeostasis has remained unproven in humans. Supplementation with inorganic NO3 and NO2 (as KNO3, NaNO3, NaNO2, or NO3-rich food products) in acute [13], mid-term [14, 15], and long-term [16 - 18] experiments, have failed to show beneficial effects on glucose and insulin parameters including fasting and postprandial plasma glucose and insulin, insulin resistance indices, and HbA1c levels in patients with T2D. This chapter reviews available data, animal experiments and human clinical trials, addressing the potential effects of inorganic NO3/NO2 on glucose and insulin homeostasis in T2D. We also try to provide some plausible reasons to address the challenge of lost-in-translation of beneficial effects of inorganic NO3 and NO2 from bench-to-bedside.

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INORGANIC NITRATE PERSPECTIVE

AND

NITRITE:

A

NUTRITIONAL

Due to the historical background about potential hazardous effects of inorganic NO3 and NO2 [19, 20], strict regulations and limitations have been legislated for exogenous exposure of NO3-NO2 from both dietary intake and drinking water [21]. In 1975, US Environmental Protection Agency (EPA) established the maximum contaminant level for NO3 at 10 mg/L, and in 1993, the world health organization (WHO) established the maximum concentration limit as 11.3 mg/L nitrate-nitrogen in drinking water; the permissible NO3 level in drinking water is now 50 mg/L in the European Union and 44 mg/L in the US [22]. The acceptable daily intake (ADI) values are 3.7 and 0.06 mg/kg body weight for NO3 and NO2, respectively [22]. The acute oral LD50 values of sodium nitrate (NaNO3) in rats, mice, and rabbits were reported in a range of 2480-9000 mg/kg; for sodium nitrite (NaNO2), these values range 180-214 mg/kg in rats, rabbits, and mice [23]. Food and Dietary Sources of Inorganic NO3 and NO2 The main dietary sources of inorganic NO3 are vegetables, especially green leafy vegetables, beetroot, and celery [24]. The NO3 levels of vegetables are commonly categorized as low (1000 mg/kg) [25, 26]. Celery, mint, lettuce, tarragon, beetroot, and radish are considered very-high NO3-containing vegetables, while scallion, cauliflower, zucchini, eggplant, parsley, leek, dill, spinach, cabbage, turnip, cress, and basil are classified as high NO3-containing vegetables [27]. Other vegetables, including carrots, onions, mushrooms, fenugreek, cucumber, and green pea, contain a medium level of NO3, whereas corn, garlic, potato, green beans, and tomato are categorized as low- and very low-NO3 vegetables [27]. A recent systematic search reviewed 255 published documents (1980-2016) on NO3 content of vegetables database, reported that NO3 content of vegetables ranged from Chinese flat cabbage (median=4240, range= 3004-6310 mg/kg of fresh weight) to corn (median=12; 5-1091 mg/kg of fresh weight) [24]. The NO2 content of vegetables has been reported in a range of less than 1 mg/kg, however in some Asian countries (e.g., Iran, Japan, Turkey, and South Korea), NO2 contents of vegetables were reported to be in a wide range of 1.7-7.4 mg/kg [27 - 30]. European countries usually report a lower range of NO2 content in vegetables to be 0.1-2.5 mg/kg [30]; however, some countries, e.g., Denmark and Germany, reported a maximum level of 11.0 and 19.6 mg/kg, respectively [30]. In some reports, NO2 concentrations ranged between 1.1-54 mg/kg [31]; a wide range of NO2 levels were reported in vegetables especially in lettuce (2.9-8.8 mg/kg), spinach (3.8-12.7 mg/kg), and radish (2.4-14.2 mg/kg) [32]. Several

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factors, including environmental factors (i.e., soil conditions, temperature, NO3 content of water, geographical location), food processing methods, cooking, and condition of storage, affect the NO3 content of vegetables [25]. Increased use of nitrogen-containing fertilizers and groundwater NO3 pollution may explain reports indicating higher concentrations of NO2 and NO3 in vegetables [33]. Although the primary sources of inorganic NO3 and NO2 from the usual diet are natural vegetables and fruits rather than food additives, there is a great concern for high amounts of NO2 residing in processed foods. The NO3 and NO2 contents (as KNO3 and NaNO2) of cured meats were reported to be 55.6-194 mg/kg and 33.9 to 139 mg/kg, respectively [27]. Generally, a wide range of NO2 and NO3 residues (0.2-195 and 3.7 to 1.4-445 mg/kg) in processed meat products has been reported by previous studies [34, 35]. The different maximum permitted levels of NO2 and NO3 residues in processed meat products were defined by countries; the United States Food and Drug Administration (FDA) defined a maximum level of 500 and 200 ppm for NaNO3 and NaNO2 [36], while Australia and New Zealand food standard, permits a maximum level of 500 and 125 mg/kg for NO2 and NO3 for processed meat products [37]. Although the ADI of NO3 intake is defined as ~260 mg/day, a wide range of usual dietary intake of inorganic NO3, from 30-1200 mg/day, has been estimated among the different populations. A recent systematic review of 43 studies (mainly from US and EU countries), used a food frequency questionnaire (FFQ) for estimation of dietary NO3 intake, indicates that the median daily intake of inorganic NO3 in healthy and patient populations was 108 mg/day (87-145 mg/day) and 110 (89153 mg/day), respectively; however, the authors concluded that due to considerable heterogeneity in using food-composition tables, the accuracy of estimated daily NO3 intake remains disputable [38]. A significant inverse association between usual dietary intake of inorganic NO3 and Gross Domestic Product (GDP) index and KOF Globalization Index was reported; low- or middleincome countries (e.g., Mexico, China, or Thailand) reported a higher intake of inorganic NO3 compared to countries who had a higher per capita income (e.g., the United States or the Netherlands) [38]. Dietary Intake of NO3 and NO2 and Risk of Diseases The effects of usual dietary intake of inorganic NO2 and NO3 on health outcomes remain under debate. Due to their capacity to form deleterious species such as Nnitroso compounds, dietary NO3 and NO2 have been accused of developing cancer and thyroid disorders [39]. A meta-analysis of population-based studies reported no significant association between NO3 exposure and the risk of thyroid cancer and hyper- and hypothyroidism; however, higher exposure to inorganic NO2

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increased the risk of thyroid cancer (HR= 1.48, 95% CI= 1.09-2.02) [19]. The highest compared to the lowest dietary NO2 intake (≥ 12.7 vs. < 6.04 mg/day) was related to a significant reduced risk of HTN (OR=0.58, 95% CI=0.33-0.98) and chronic kidney disease (CKD) (OR=0.50, 95% CI=0.24-0.89) [40]. Higher intake of NO3 (≥ 430 mg/day) increased the risk of cardiovascular diseases (CVD) in subjects who had a low-TAC (total antioxidant capacity) (HR=3.28, 95% CI=1.54-6.99), while dietary NO2 was not related to CVD events during 6.7 years of follow-up [41]. Findings of a meta-analysis of 62 epidemiologic studies showed that higher intake of NO3 from the usual diet was inversely associated with gastric cancer risk (RR= 0.78, 95% CI= 0.67-0.91), while dietary NO2 intake was positively associated with adult glioma and thyroid cancer (RR=1.21, 95% CI= 1.03-1.42, and RR=1.52, 95%CI = 1.12-2.05) [42]; no significant association was observed between dietary NO3-NO2 and the risk of breast, bladder, colorectal, esophagus, renal, non-Hodgkin lymphoma, ovarian, and pancreatic cancers [42]. A metaanalysis of 2,573,524 participants (aged 20-85 years) with 38,848 cases of colorectal cancer reported that higher intake of NO3 from the diet was associated with a risk of colorectal cancer (pooled HR=1.13, 95% CI=1.04-1.23), whereas dietary NO2 was not significantly associated with risk of colorectal cancer (pooled HR=1.07, 95% CI=0.95-1.21) [43]. Considering the potential endogenous conversion of NO2 to nitrosamine compounds and adverse effects of nitrosamines on insulin/insulin-like growth factor (IGF) signaling pathways and pancreatic β-cell function, higher NO3 and NO2 exposure, from either diet or drinking water, has also been considered as a risk factor for the development of diabetes [44, 45]. Current data regarding dietary exposure of NO3 and NO2 and the development of type 1 diabetes (T1D) is inconsistent; a mean NO3 levels < 25 mg/L in drinking water was not related to the risk of T1DM, whereas an increased risk was observed in geographic regions with a maximum NO3 level > 40-80 mg/L [46]. In the case of T2D, limited data is available; a 6-year follow-up among an Asian population showed that the incidence of T2D was increased in subjects who had a high-NO2-low-vitamin C diet (HR=1.88, 95% CI=1.12-3.15, total NO2 ≥8.77 mg/d, vitamin C