Mitochondrial ADP privation: A unifying model for glucose-induced insulin secretion.

线粒体 ADP 缺乏：葡萄糖诱导的胰岛素分泌的统一模型。

• 批准号: 10366083
• 负责人: Richard G Kibbey
• 金额: $ 68.47万
• 依托单位: YALE UNIVERSITY
• 依托单位国家: 美国
• 财政年份: 2021
• 资助国家: 美国
• 起止时间: 2021-04-01 至 2026-03-31
• 项目状态: 未结题
• 来源: https://reporter.nih.gov/project-details/10366083
• 关键词: Acetyl Coenzyme A; Agonist; Animal Model; Beta Cell; Biochemical; Biophysics; Carbon; Cell Line; Cell membrane; Cell physiology; Cells; Cellular Metabolic Process; Characteristics; Citric Acid Cycle; Conflict (Psychology); Coupling; Diet; Disputes; Electrophysiology (science); Exocytosis; Failure; Fructose; G-Protein-Coupled Receptors; Generations; Genetic; Glucokinase; Glucose; Health; Human; Hydrolysis; Imaging Techniques; Insulin; Islet Cell; Link; Mediating; Membrane; Metabolic; Metabolism; Mitochondria; Modeling; Mus; Oxidative Phosphorylation; Pharmacology; Pharmacotherapy; Phase; Phosphoenolpyruvate; Physiological; Privatization; Proton-Motive Force; Pyruvate Carboxylase; Pyruvate Kinase; Reaction; Regulation; Reporter; Rodent; Signal Transduction; Structure of beta Cell of islet; Testing; Theft; Therapeutic; Time; Translational Research; base; blood glucose regulation; clinical efficacy; detection of nutrient; diabetogenic; improved; in vivo; insulin secretion; islet; metabolomics; mitochondrial metabolism; oxidation; phenomics; pre-clinical; pyruvate dehydrogenase; stable isotope; tool; voltage

The most widely-accepted description of the β-cells 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 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 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.

对β细胞葡萄糖感应机制的最广泛接受的描述涉及葡萄糖碳的线粒体氧化以提高ATP/ADP比，关闭KATP通道并激活Ca2+影响，并激活Ca2+影响，这会触发胰岛素胞毒素。尽管毫无争议的是，氧化磷酸化（OXPHOS）有助于β细胞中ATP生物合成能力的功能，但几条遗传，生物物理和实验证据挑战了规范机制的一个关键组成部分 - 将Oxphos耦合到KATP通道封口的排除。重要的是，通过丙酮酸羧化酶（PC）的膨胀线粒体代谢产物（无腐败）与胰岛素分泌更密切相关，而不是通过丙酮酸氧化通量 脱氢酶（PDH）。传输PC的葡萄糖碳通过催化的线粒体PEP羧基酶（PCK2）反应产生40％的胞质磷酸烯醇丙酮酸（PEP）。这种“ PEP循环”提供了一种与Oxphos通过丙酮酸激酶（PK）产生胞质ATP/ADP生成的机制。在这里，我们提出了一个统一的模型，该模型通过调用振荡性的两态模型来调和典型的Oxphos与斜方张，其中PK本身会启动KATP通道闭合。在第一阶段中，PK被称为“ mitosynth”，胞质ADP降低，剥夺了线粒体的ADP（称为“ ADP PRIVICATION”），即1）关闭Oxphos以加速PEP周期，2）PEP，2）PEP，然后离开线粒体，然后离开线粒体，在其中3）PK局部triggerally Triggers triggers triggers trggers katp kater katp katpure katp katpure katp katpure。去极化后，第二阶段称为“ mitoox”，通过Oxphos维持膜沉积和胰岛素分泌。该修订的模型对β细胞功能，药物治疗和健康具有深远的影响。该建议将确定PK是否可以胜过ADP的线粒体，该ADP隐私是否会关闭Oxphos并诱导线粒体PEP合成，并且是否靶向线粒体可以改善胰岛功能和体内胰岛功能和健康。目标1：评估PK介导的ADP隐私如何诱导高压，低电流的丝裂状态。这个目标提出了一个问题，PK可以从线粒体中窃取ADP，作为刺激胰岛素的信号的一部分 分泌？这样的ADP隐私在电相阶段结束时引起KATP触发和线粒体超极化。目标2：确定线粒体ADP隐私在mitosynth期间对旋律和催化代谢的调节。假设是线粒体ADP隐私通过变构中间体的产生激活了PEP循环。此目的评估了线粒体状态的机械，功能和生化表征。目标3：确定体内β细胞葡萄糖敏感性的物理和药物意义的细分和mitoox阶段。在两国模型中，至少有两种可靶向的机制来增加胰岛素分泌：延长mitoox或缩短mitosynth触发沉积的时间。我们将确定Mitoox是否延长了胰岛，而Mitosynth缩短了促进人类胰岛的健康。