R01DK127637

Mitochondrial ADP Privation: A Unifying Model for Glucose-Induced Insulin Secretion.

The most widely-accepted description of the β-cell glucose sensing mechanism involves the mitochondrial oxidation of glucose carbons to raise the ATP/ADP ratio, close KATP channels, and activate Ca2+ influx, which triggers insulin exocytosis. While there is no dispute that oxidative phosphorylation (OXPHOS) contributes to function and increased ATP biosynthetic capacity in β-cells, several lines of genetic, biophysical, and experimental evidence challenge one key component of the canonical mechanism – the exclusivity of coupling OXPHOS to KATP channel closure.

Importantly, the expansion of mitochondrial metabolites (anaplerosis) through pyruvate carboxylase (PC) is more strongly correlated with insulin secretion than oxidative flux through pyruvate dehydrogenase (PDH). Glucose carbons that transit PC generate 40% of the cytosolic phosphoenolpyruvate (PEP) through the cataplerotic mitochondrial PEP carboxykinase (PCK2) reaction. This 'PEP cycle' provides a mechanism distinct from OXPHOS for cytosolic ATP/ADP generation via pyruvate kinase (PK).

Here, we propose a unified model that reconciles canonical OXPHOS with anaplerosis by invoking an oscillatory, two-state model where PK itself initiates KATP channel closure. In the first phase, termed 'mitosynth,' cytosolic ADP lowering by PK deprives mitochondria of ADP (termed 'ADP privation') that 1) turns off OXPHOS to accelerate the PEP cycle, 2) PEP then leaves the mitochondria where 3) its hydrolysis by PK locally triggers KATP channel closure. Following depolarization, the second phase, termed 'mitoox,' sustains membrane depolarization and insulin secretion via OXPHOS.

This revised model has profound implications for β-cell function, pharmacotherapy, and health. This proposal will determine if PK can outcompete mitochondria for ADP, if such ADP privation turns off OXPHOS and induces mitochondrial PEP synthesis, and if targeting mitosynth can improve islet function and health in vivo.

Aim 1: To assess how PK-mediated ADP privation induces the high-voltage, low-current mitosynth state. This aim asks the question, can PK steal ADP from mitochondria as part of the signal to stimulate insulin secretion? Such ADP privation induces KATP triggering and mitochondrial hyperpolarization at the end of the electrically-silent phase.

Aim 2: To determine the regulation of anaplerotic and cataplerotic metabolism by mitochondrial ADP privation during mitosynth. The hypothesis is that mitochondrial ADP privation activates PEP cycling through the generation of allosteric intermediates. This aim assesses the mechanistic, functional, and biochemical characterization of the mitosynth state.

Aim 3: To determine the physiological and pharmacological significance of mitosynth and mitoox phases of β-cell glucose sensing in vivo. In the two-state model, there are at least two targetable mechanisms to augment insulin secretion: lengthening mitoox or shortening the time for mitosynth to trigger depolarization. We will determine if mitoox lengthening injures islets while mitosynth shortening promotes human islet health.

Yale Univ

(1) TO PROMOTE EXTRAMURAL BASIC AND CLINICAL BIOMEDICAL RESEARCH THAT IMPROVES THE UNDERSTANDING OF THE MECHANISMS UNDERLYING DISEASE AND LEADS TO IMPROVED PREVENTIONS, DIAGNOSIS, AND TREATMENT OF DIABETES, DIGESTIVE, AND KIDNEY DISEASES. PROGRAMMATIC AREAS WITHIN THE NATIONAL INSTITUTE OF DIABETES AND DIGESTIVE AND KIDNEY DISEASES INCLUDE DIABETES, DIGESTIVE, ENDOCRINE, HEMATOLOGIC, LIVER, METABOLIC, NEPHROLOGIC, NUTRITION, OBESITY, AND UROLOGIC DISEASES. SPECIFIC PROGRAMS AREAS OF INTEREST INCLUDE THE FOLLOWING: (A) FOR DIABETES, ENDOCRINE, AND METABOLIC DISEASES AREAS: FUNDAMENTAL AND CLINICAL STUDIES INCLUDING THE ETIOLOGY, PATHOGENESIS, PREVENTION, DIAGNOSIS, TREATMENT AND CURE OF DIABETES MELLITUS AND ITS COMPLICATIONS; NORMAL AND ABNORMAL FUNCTION OF THE PITUITARY, THYROID, PARATHYROID, ADRENAL, AND OTHER HORMONE SECRETING GLANDS; HORMONAL REGULATION OF BONE, ADIPOSE TISSUE, AND LIVER; ON FUNDAMENTAL ASPECTS OF SIGNAL TRANSDUCTION, INCLUDING THE ACTION OF HORMONES, COREGULATORS, AND CHROMATIN REMODELING PROTEINS; HORMONE BIOSYNTHESIS, SECRETION, METABOLISM, AND BINDING; AND ON HORMONAL REGULATION OF GENE EXPRESSION AND THE ROLE(S) OF SELECTIVE RECEPTOR MODULATORS AS PARTIAL AGONISTS OR ANTAGONISTS OF HORMONE ACTION; AND FUNDAMENTAL STUDIES RELEVANT TO METABOLIC DISORDERS INCLUDING MEMBRANE STRUCTURE, FUNCTION, AND TRANSPORT PHENOMENA AND ENZYME BIOSYNTHESIS; AND BASIC AND CLINICAL STUDIES ON THE ETIOLOGY, PATHOGENESIS, PREVENTION, AND TREATMENT OF INHERITED METABOLIC DISORDERS (SUCH AS CYSTIC FIBROSIS). (B) FOR DIGESTIVE DISEASE AND NUTRITION AREAS: GENETICS AND GENOMICS OF THE GI TRACT AND ITS DISEASES; GENETICS AND GENOMICS OF LIVER/PANCREAS AND DISEASES; GENETICS AND GENOMICS OF NUTRITION; GENETICS AND GENOMICS OF OBESITY; BARIATRIC SURGERY; CLINICAL NUTRITION RESEARCH; CLINICAL OBESITY RESEARCH; COMPLICATIONS OF CHRONIC LIVER DISEASE; FATTY LIVER DISEASE; GENETIC LIVER DISEASE; HIV AND LIVER; CELL INJURY, REPAIR, FIBROSIS AND INFLAMMATION IN THE LIVER; LIVER CANCER; LIVER TRANSPLANTATION; PEDIATRIC LIVER DISEASE; VIRAL HEPATITIS AND INFECTIOUS DISEASES; GASTROINTESTINAL AND NUTRITION EFFECTS OF AIDS; GASTROINTESTINAL MUCOSAL AND IMMUNOLOGY; GASTROINTESTINAL MOTILITY; BASIC NEUROGASTROENTEROLOGY; GASTROINTESTINAL DEVELOPMENT; GASTROINTESTINAL EPITHELIAL BIOLOGY; GASTROINTESTINAL INFLAMMATION; DIGESTIVE DISEASES EPIDEMIOLOGY AND DATA SYSTEMS; NUTRITIONAL EPIDEMIOLOGY AND DATA SYSTEMS; AUTOIMMUNE LIVER DISEASE; BILE, BILIRUBIN AND CHOLESTASIS; BIOENGINEERING AND BIOTECHNOLOGY RELATED TO DIGESTIVE DISEASES, LIVER, NUTRITION AND OBESITY; CELL AND MOLECULAR BIOLOGY OF THE LIVER; DEVELOPMENTAL BIOLOGY AND REGENERATION; DRUG-INDUCED LIVER DISEASE; GALLBLADDER DISEASE AND BILIARY DISEASES; EXOCRINE PANCREAS BIOLOGY AND DISEASES; GASTROINTESTINAL NEUROENDOCRINOLOGY; GASTROINTESTINAL TRANSPORT AND ABSORPTION; NUTRIENT METABOLISM; PEDIATRIC CLINICAL OBESITY; CLINICAL TRIALS IN DIGESTIVE DISEASES; LIVER CLINICAL TRIALS; OBESITY PREVENTION AND TREATMENT; AND OBESITY AND EATING DISORDERS. (C) FOR KIDNEY, UROLOGIC AND HEMATOLOGIC DISEASES AREAS: STUDIES OF THE DEVELOPMENT, PHYSIOLOGY, AND CELL BIOLOGY OF THE KIDNEY; PATHOPHYSIOLOGY OF THE KIDNEY; GENETICS OF KIDNEY DISORDERS; IMMUNE MECHANISMS OF KIDNEY DISEASE; KIDNEY DISEASE AS A COMPLICATION OF DIABETES; EFFECTS OF DRUGS, NEPHROTOXINS AND ENVIRONMENTAL TOXINS ON THE KIDNEY; MECHANISMS OF KIDNEY INJURY REPAIR; IMPROVED DIAGNOSIS, PREVENTION AND TREATMENT OF CHRONIC KIDNEY DISEASE AND END-STAGE RENAL DISEASE; IMPROVED APPROACHES TO MAINTENANCE DIALYSIS THERAPIES; BASIC STUDIES OF LOWER URINARY TRACT CELL BIOLOGY, DEVELOPMENT, PHYSIOLOGY, AND PATHOPHYSIOLOGY; CLINICAL STUDIES OF BLADDER DYSFUNCTION, INCONTINENCE, PYELONEPHRITIS, INTERSTITIAL CYSTITIS, BENIGN PROSTATIC HYPERPLASIA, UROLITHIASIS, AND VESICOURETERAL REFLUX; DEVELOPMENT OF NOVEL DIAGNOSTIC TOOLS AND IMPROVED THERAPIES, INCLUDING TISSUE ENGINEERING STRATEGIES, FOR UROLOGIC DISORDERS;RESEARCH ON HEMATOPOIETIC CELL DIFFERENTIATION; METABOLISM OF IRON OVERLOAD AND DEFICIENCY; STRUCTURE, BIOSYNTHESIS AND GENETIC REGULATION OF HEMOGLOBIN; AS WELL AS RESEARCH ON THE ETIOLOGY, PATHOGENESIS, AND THERAPEUTIC MODALITIES FOR THE ANEMIA OF INFLAMMATION AND CHRONIC DISEASES.(2) TO ENCOURAGE BASIC AND CLINICAL RESEARCH TRAINING AND CAREER DEVELOPMENT OF SCIENTISTS DURING THE EARLY STAGES OF THEIR CAREERS. THE RUTH L. KIRSCHSTEIN NATIONAL RESEARCH SERVICE AWARD (NRSA) FUNDS BASIC AND CLINICAL RESEARCH TRAINING, SUPPORT FOR CAREER DEVELOPMENT, AND THE TRANSITION FROM POSTDOCTORAL BIOMEDICAL RESEARCH TRAINING TO INDEPENDENT RESEARCH RELATED TO DIABETES, DIGESTIVE, ENDOCRINE, HEMATOLOGIC, LIVER, METABOLIC, NEPHROLOGIC, NUTRITION, OBESITY, AND UROLOGIC DISEASES. (3) TO EXPAND AND IMPROVE THE SMALL BUSINESS INNOVATION RESEARCH (SBIR) PROGRAM. THE SBIR PROGRAM AIMS TO INCREASE AND FACILITATE PRIVATE SECTOR COMMERCIALIZATION OF INNOVATIONS DERIVED FROM FEDERAL RESEARCH AND DEVELOPMENT; TO ENHANCE SMALL BUSINESS PARTICIPATION IN FEDERAL RESEARCH AND DEVELOPMENT; AND TO FOSTER AND ENCOURAGE PARTICIPATION OF SOCIALLY AND ECONOMICALLY DISADVANTAGED SMALL BUSINESS CONCERNS AND WOMEN-OWNED SMALL BUSINESS CONCERNS IN TECHNOLOGICAL INNOVATION. (4) TO UTILIZE THE SMALL BUSINESS TECHNOLOGY TRANSFER (STTR) PROGRAM. THE STTR PROGRAM INTENDS TO STIMULATE AND FOSTER SCIENTIFIC AND TECHNOLOGICAL INNOVATION THROUGH COOPERATIVE RESEARCH AND DEVELOPMENT CARRIED OUT BETWEEN SMALL BUSINESS CONCERNS AND RESEARCH INSTITUTIONS; TO FOSTER TECHNOLOGY TRANSFER BETWEEN SMALL BUSINESS CONCERNS AND RESEARCH INSTITUTIONS; TO INCREASE PRIVATE SECTOR COMMERCIALIZATION OF INNOVATIONS DERIVED FROM FEDERAL RESEARCH AND DEVELOPMENT; AND TO FOSTER AND ENCOURAGE PARTICIPATION OF SOCIALLY AND ECONOMICALLY DISADVANTAGED SMALL BUSINESS CONCERNS AND WOMEN-OWNED SMALL BUSINESS CONCERNS IN TECHNOLOGICAL INNOVATION.

93.847 - Diabetes, Digestive, and Kidney Diseases Extramural Research

National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK) [HHS - NIH]

New Haven, Connecticut 065191612 United States

Single Zip Code

NIH Research Project Grant (Parent R01 Clinical Trial Not Allowed) (PA-20-185)

Amendment Since initial award the End Date has been extended from 03/31/26 to 03/31/27 and the total obligations have increased 386% from $701,583 to $3,413,027.