Role of SIRT3 in Modulation of Lipotoxicity in Liver

描述(由申请人提供)：sirtuins是一种依赖NAD+的蛋白质去乙酰基酶，可调节对各种压力的适应性反应，包括卡路里限制和代谢压力。Sirtuin 3(SIRT3)定位于线粒体基质中，调节多种代谢酶的乙酰化水平。虽然在卡路里限制的模型中有很好的特征，但对sirtuins和乙酰基在卡路里过剩条件下的作用知之甚少。我们最近的结果表明，当正常小鼠喂食高脂饮食时，它们表现出SIRT3活性降低，线粒体功能受损，以及肝脏中一系列蛋白质的超乙酰化，包括糖异生酶。此外，SIRT3基因敲除小鼠有加速衰老和癌症的迹象。了解SIRT3的S在热量过多条件下肝脏中的生化功能和调节，可能有助于解释线粒体功能降低与脂糖代谢紊乱之间的联系，如2型糖尿病和非酒精性脂肪性肝病。这项建议的直接目的有两个：1)确定在高脂喂养期间恢复肝脏SIRT3活性是否可以减缓肥胖相关脂肪变性或肝脏胰岛素抵抗的进展，以及2)确定增加肝脏NAD+-SIRT3活性的主要决定因素是否会减弱肥胖相关的线粒体ROS和蛋白质乙酰化。该项目的长期目标是剖析过量营养如何导致关键蛋白质的超乙酰化的机制，并确定SIRT3在NAFLD和2型糖尿病易感性中的调节作用。

DESCRIPTION (provided by applicant): Sirtuins are NAD+-dependent protein deacetylases that mediate adaptive responses to a variety of stresses, including calorie restriction and metabolic stress. Sirtuin 3 (SIRT3) is localized within the mitochondrial matrix, where it regulates acetylation levels of a diverse set of metabolic enzymes. Although well characterized in models of caloric restriction, relatively little is known about the role of Sirtuins and acetylaion under conditions of caloric excess. Our recent results show that when normal mice are fed a high fat diet they demonstrate reduced SIRT3 activity, impaired mitochondrial function, and hyperacetylation of a diverse set of proteins, including gluconeogenic enzymes, in their livers. Furthermore, SIRT3 knockout mice have signs of accelerated aging and cancer. Understanding SIRT3's biochemical function and regulation in the liver under conditions of caloric excess may potentially help explain the connection between reduced mitochondrial function and disorders of lipid and glucose metabolism, such as type 2 diabetes and nonalcoholic fatty liver disease (NAFLD). The immediate purpose of this proposal is two-fold: 1) determine if restoration of hepatic SIRT3 activity during high fat feeding can attenuate the progression of obesity- related steatosis or hepatic insulin resistance, and 2) Determine whether increasing hepatic NAD+, the major determinant of SIRT3 activity, will attenuate obesity-linked mitochondrial ROS and protein acetylation. The long-term goal of this project is to dissect the mechanisms surrounding how excess nutrients lead to hyperacetylation of key proteins and to identify a regulatory role for SIRT3 in NAFLD and susceptibility to type 2 diabetes.