Energy Sensors and the Regulation of the TCA Cycle in the Liver

能量传感器和肝脏 TCA 循环的调节

基本信息

批准号：
9122043
负责人：
Justin Fletcher
金额：
$ 5.43万
依托单位：
UT SOUTHWESTERN MEDICAL CENTER
依托单位国家：
美国
项目类别：
财政年份：
2016
资助国家：
美国
起止时间：
2016-02-11 至 2019-02-10
项目状态：
已结题

来源：
https://reporter.nih.gov/project-details/9122043
关键词：
ATP Synthesis Pathway Accounting Acetyl Coenzyme A Acetylation Acute Affect Anabolism Biochemical Biological Blood Glucose Carbohydrates Carbon Dioxide Catabolic Process Charge Citric Acid Cycle Deacetylase Diet Disease Disease Resistance Electron Transport Enzymes Equipment Design FADH2 Fasting Fatty Acids Fatty acid glycerol esters Future Gene Expression Gluconeogenesis Glucose Hepatic Individual Inflammation Insulin Resistance Isotopes Knockout Mice Knowledge Lead Lipids Liver Liver Mitochondria Liver diseases Metabolic Metabolism Mitochondria Mitochondrial Proteins Modeling Molecular Mus NADH Nonesterified Fatty Acids Nutrient Obesity Oxaloacetates Oxidation-Reduction Oxidative Regulation Oxidative Stress Pathologic Processes Pathology Pathway interactions Pharmacologic Substance Phosphoenolpyruvate Phosphoenolpyruvate Carboxylase Phosphotransferases Play Process Production Regulation Research Role Thermodynamics Tracer Training Work blood lipid enzyme activity ex vivo perfusion fatty acid oxidation feeding glucose production in vivo liver function loss of function meetings mitochondrial dysfunction non-alcoholic fatty liver oxidation prevent public health relevance research study response sensor stable isotope

项目摘要

DESCRIPTION (provided by applicant): The liver plays a vital role in maintaining blood glucose levels, in part, through gluconeogenic processes. Gluconeogenesis is an energy costly process that is supported through fat oxidation in hepatic mitochondria. The TCA cycle serves as a hub where acetyl-CoA from the break down of fatty acids and carbohydrates meet for oxidation to CO2 and the production of 3 NADH and 1 FADH2. Not only does the TCA cycle support gluconeogenesis through the formation of reducing equivalents that fuel the electron transport chain, but it also provides gluconeogenic substrates through cataplerotic processes. Changes in substrate concentration and redox state modulate TCA cycle flux and anaplerotic/cataplerotic processes. However, the mechanisms regulating this metabolic response remain to be elucidated. In pathological conditions such as obesity and insulin resistance, TCA cycle flux and gluconeogenesis are elevated, contributing to the inappropriately high endogenous glucose production often observed in insulin resistant individuals. Still, it is no known how the TCA cycle is regulated in this diseased state. Many metabolic processes are sensitive to the energy state, and energy sensors, such as AMPK and Sirtuin 3 (SIRT3) may be responsible for coordinating the response of these metabolic processes to changes in energy charge. AMPK is an energy sensor that is activated in response to high AMP:ATP ratios. In response, AMPK stimulates catabolic processes, such as fatty acid oxidation to replenish ATP. Specific Aim 1 will use ex vivo and in vivo experiments, with and without the regulatory capacity of AMPK to determine whether AMPK is responsible for changes in TCA cycle flux and cataplerotic/anaplerotic processes in response to changes in substrate concentration (ex vivo), or in an obese, insulin resistant state (in vivo). It is hypothesized that AMPK will be necessary for increases in TCA cycle flux in response to increases in substrate concentrations and that TCA cycle flux and anaperotic/cataplerotic processes will be elevated in AMPK-KO mice in response to 16 week HFD, but that constitutively active AMPK will restore the flux of these processes. SIRT3 is a mitochondrial deactylase that is activated by changes in the redox state (high NAD+/NADH) and responds by deacetylating mitochondrial proteins involved in metabolic processes. Specific Aim 2 will examine whether SIRT3 regulates the response of TCA cycle flux and cataplerotic/anaplerotic processes to changes in redox state (ex vivo) and in the obese insulin resistant state (in vivo). I hypothesize that SIRT3 will be required for normal TCA cycle flux and anaplerotic/cataplerotic processes. The findings from this research will expand our knowledge of the role of energy sensors, and the function of TCA cycle flux and anaplerotic/cataplerotic processes in both healthy and diseased states. These results may provide future targets for pharmaceutical companies to treat or prevent NAFLD and/or insulin resistance.

描述（由申请人提供）：肝脏在维持血糖水平方面发挥着至关重要的作用，部分是通过糖异生过程来实现的，糖异生是一个消耗能量的过程，通过肝线粒体中的脂肪氧化来支持。脂肪酸和碳水化合物分解产生的乙酰辅酶 A 会氧化成 CO2 并产生 3 NADH 和 1 FADH2 不仅支持 TCA 循环。通过形成为电子传递链提供燃料的还原当量来进行糖异生，但它还通过折返过程提供糖异生底物。底物浓度和氧化还原状态的变化调节 TCA 循环通量和回补/折补过程。然而，调节这种代谢反应的机制仍然存在。在肥胖和胰岛素抵抗等病理条件下，TCA 循环通量和糖异生升高，导致胰岛素抵抗中常见的不适当的高内源性葡萄糖产生。尽管如此，目前尚不清楚在这种疾病状态下 TCA 循环是如何调节的，许多代谢过程对能量状态敏感，而能量传感器，如 AMPK 和 Sirtuin 3 (SIRT3) 可能负责协调反应。这些代谢过程会导致能量电荷的变化，AMPK 是一种能量传感器，可响应高 AMP:ATP 比例而激活。作为响应，AMPK 会刺激分解代谢过程，例如补充脂肪酸氧化。 ATP。具体目标 1 将使用离体和体内实验，无论是否具有 AMPK 的调节能力，以确定 AMPK 是否负责响应底物浓度变化而导致的 TCA 循环通量和折返/回补过程的变化（离体）。，或在肥胖、胰岛素抵抗状态（体内），人们发现 AMPK 对于响应底物浓度的增加而增加 TCA 循环通量以及 TCA 循环通量和开胃/猝倒是必要的。 AMPK-KO 小鼠中的这些过程会因 16 周 HFD 而升高，但持续活跃的 AMPK 将恢复这些过程的通量。SIRT3 是一种线粒体脱乙酰酶，可通过氧化还原状态（高 NAD+/NADH）的变化而激活。具体目标 2 将检查 SIRT3 是否调节 TCA 循环通量和解体/回补过程的反应。氧化还原状态（离体）和肥胖胰岛素抵抗状态（体内）的变化我认为正常的 TCA 循环通量和回补/回补过程需要 SIRT3。这项研究的结果将扩展我们对其作用的认识。这些结果可能为制药公司治疗或预防 NAFLD 和/或胰岛素抵抗提供未来目标。