Molecular Clock Control of Oxidative Metabolism in Metabolic Disease

描述(申请人提供)：过去十年的研究揭示了生物钟和代谢动态平衡之间的联系。缺乏分子时钟组件的小鼠会出现戏剧性的代谢异常，包括肥胖、糖调节中断、游离脂肪酸升高和代谢性肌病。尽管这些表型背后的分子机制仍不清楚，但这些缺陷中的许多都指向线粒体氧化代谢途径的中断，包括脂肪酸氧化和呼吸作用。关于昼夜节律突变中线粒体功能障碍的一个主要线索源于最近的发现，即时钟转录因子环调节细胞内NAD+的水平，进而控制依赖NAD+的Sirtuin家族脱乙酰酶的活性，这是氧化代谢的关键因素。在令人振奋的新结果中，我们现在还表明，昼夜节律突变的小鼠表现出几种线粒体酶的超乙酰化，这些酶在尿素循环、酮产生、脂肪酸氧化和ATP合成中起限速作用。因此，我的研究计划将建立在我之前对代谢转录因子途径的氧依赖控制的研究基础上，并具体检验这样的假设，即昼夜节律基因的破坏会由于NAD+合成和线粒体定位的sirtuin酶的活性失调而导致氧化代谢受损。拟议中的实验将利用实验遗传学、生物化学和细胞生理学方法，并将成为我作为新陈代谢研究的独立研究员发展的宝贵工具。

DESCRIPTION (provided by applicant): Research over the past decade has uncovered a connection between circadian clocks and metabolic homeostasis. Mice lacking components of the molecular clock develop dramatic metabolic abnormalities, including obesity, disrupted glucoregulation, elevated free fatty acids and metabolic myopathy. Although the molecular mechanisms underlying these phenotypes remain poorly understood, many of these defects point to disruptions in mitochondrial oxidative metabolic pathways, including fatty acid oxidation and respiration. A major clue concerning the cause of mitochondrial dysfunction in circadian mutants stems from the recent discovery that the clock transcription factor loop regulates cellular levels of NAD+, and in turn, controls activity of the sirtuin family of NAD+-dependent deacetylases, key factors in oxidative metabolism. In exciting new results, we also now show that circadian mutant mice exhibit hyperacetylation of several mitochondrial enzymes that are rate-limiting in the urea cycle, ketone production, fatty acid oxidation and ATP synthesis. My research proposal will thus build upon my previous studies of oxygen-dependent control of metabolic transcription factor pathways and specifically test the hypothesis that circadian gene disruption leads to impaired oxidative metabolism due to dysregulation of NAD+ synthesis and activity of mitochondrial-localized sirtuin enzymes. The proposed experiments will exploit experimental genetic, biochemical and cell physiological approaches and will serve as an invaluable vehicle in my development as an independent investigator in metabolism research.