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（由适用提供）：肝脏在一定程度上通过糖原生成过程在维持血糖水平方面起着至关重要的作用。糖生成是一个能量代价高昂的过程，它通过肝脏线粒体中的脂肪氧化得到了支持。 TCA循环用作枢纽，其中脂肪酸和碳水合物分解的乙酰辅酶A会氧化二氧化碳，并产生3 NADH和1 FADH2。 TCA循环不仅通过形成减少电子传输链的等效物来支持麸质生成，而且还通过脱氧过程提供了麸质底物。底物浓度和氧化还原状态的变化调节TCA循环通量和变性/脱囊过程。但是，调节这种代谢反应的机制仍有待阐明。在肥胖症和胰岛素抵抗等病理状况下，TCA循环通量和甘机发生升高，导致在胰岛素耐药性个体中经常观察到的不适当的内源性葡萄糖产生不适当。尽管如此，尚不清楚如何在这种差异状态下调节TCA周期。许多代谢过程对能量状态很敏感，并且能量传感器（例如AMPK和SIRTUIN 3（SIRT3））可能负责协调这些代谢过程对能源电荷变化的响应。 AMPK是一种能够根据高AMP：ATP比率激活的能量传感器。作为响应，AMPK刺激分解代谢过程，例如脂肪酸氧化以复制ATP。具体目标1将使用离体和体内实验，并且有或没有AMPK的调节能力来确定AMPK是否负责TCA循环通量和催化性/疾病的变化，以应对底物浓度变化（EX VIVO）（EX VIVO），或者在肥胖症中，胰岛素抵抗状态（INVIVO）。假设AMPK对于增加底物浓度的响应而需要增加TCA循环通量，并且TCA循环通量和Anaperotic/Anaperotic/artaplerotic过程将在AMPK-KO小鼠中升高，响应于16周的HFD，但是强制性的活动AMPK将恢复这些过程的磁通量。 SIRT3是一种线粒体脱纤酶，通过氧化还原态（高NAD+/NADH）的变化激活，并通过脱乙酰基线粒体蛋白参与代谢过程而反应。具体的目标2将检查SIRT3是否调节了TCA循环通量和脱链状细菌/静电性过程对氧化还原状态（EX VIVO）变化和肥胖胰岛素抵抗状态（体内）的响应。我假设正常的TCA循环通量和变性/催化过程需要SIRT3。这项研究的发现将扩大我们对能量传感器的作用的了解，以及在健康和失常状态下TCA循环通量和厌氧/催化过程的功能。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。