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

• 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
• 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

 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起着至关重要的作用，部分是通过生血管过程。葡萄糖异生是一个消耗能量的过程，它通过肝线粒体中的脂肪氧化来支持。TCA循环作为一个枢纽，其中来自脂肪酸和碳水化合物分解的乙酰辅酶A相遇氧化为CO2并产生3 NADH和1 FADH 2。TCA循环不仅通过形成为电子传递链提供燃料的还原当量来支持再生，而且还通过分解过程提供再生底物。底物浓度和氧化还原状态的变化调节TCA循环通量和回补/分解过程。然而，调节这种代谢反应的机制仍有待阐明。在诸如肥胖和胰岛素抵抗的病理状况下，TCA循环通量和胰岛素生成升高，导致通常在胰岛素抵抗个体中观察到的不适当的高内源性葡萄糖产生。尽管如此，它是不知道如何在这种疾病状态下调节TCA循环。许多代谢过程对能量状态敏感，能量传感器，如AMPK和Sirtuin 3（SIRT 3）可能负责协调这些代谢过程对能量电荷变化的响应。AMPK是一种能量传感器，响应于高AMP：ATP比率而被激活。作为回应，AMPK刺激分解代谢过程，如脂肪酸氧化以补充ATP。具体目标1将使用离体和体内实验，有和没有AMPK的调节能力，以确定AMPK是否负责响应底物浓度变化（离体）或肥胖、胰岛素抵抗状态（体内）的TCA循环通量和分解/回补过程的变化。假设AMPK对于响应于底物浓度增加的TCA循环通量的增加是必需的，并且响应于16周HFD，AMPK-KO小鼠中的TCA循环通量和厌氧/分解过程将升高，但是组成性活性AMPK将恢复这些过程的通量。SIRT 3是一种线粒体脱乙酰酶，通过氧化还原状态（高NAD+/NADH）的变化激活，并通过脱乙酰化参与代谢过程的线粒体蛋白质进行响应。具体目标2将检查SIRT 3是否调节TCA循环通量和分解/回补过程对氧化还原状态（离体）和肥胖胰岛素抵抗状态（体内）变化的响应。我假设SIRT 3将需要正常的TCA循环流量和回补/cataplerotic过程。这项研究的结果将扩大我们对能量传感器的作用，以及健康和疾病状态下TCA循环通量和回补/cataplerotic过程的功能的了解。这些结果可能为制药公司提供治疗或预防NAFLD和/或胰岛素抵抗的未来目标。