Sir2 Regulates AMPK and Lipid Metabolism in Diabetes

描述(申请人提供)：肥胖、胰岛素抵抗、糖尿病和高脂血症是心血管疾病和死亡的主要原因。SIRT1是哺乳动物沉默信息调节因子2(Sir2)的同源基因，是一种依赖NAD的脱乙酰酶，介导热量限制延长寿命的效应。能量感受器AMP激活的蛋白激酶(AMPK)及其上游的LKB1与世界范围内使用的抗糖尿病药物二甲双胍的疗效有关。我最近的研究和其他研究表明，包括红葡萄酒中存在的白藜芦醇在内的多酚都能激活SIRT1和AMP激活的蛋白激酶(AMPK)这两种主要代谢调节因子。然而，SIRT1是否以及如何与AMPK信号有关，脂代谢和动脉粥样硬化仍然难以捉摸。我建立了1型和2型糖尿病低密度脂蛋白受体缺陷(LDLR-/-)小鼠的体外肝细胞模型和体内模型，为1)多酚类化合物强烈阻止AMPK的抑制，上调AMPK的两个关键下游效应因子--乙酰辅酶A羧化酶(ACC)和调节元件结合蛋白(SREBP)，减少肝脂沉积，从而延缓糖尿病高脂血症和动脉粥样硬化提供新的证据；2)在体外，SIRT1或AMPK抑制AMPK的刺激和多酚的降脂作用；3)SIRT1在体内外的肝细胞过度表达刺激AMPK，下调SREBP的功能，降低血脂。本研究的中心假设是多酚激活SIRT1作为LKB1/AMPK信号的上游调节因子，调节肝细胞的脂质代谢，对糖尿病引起的高脂血症和动脉粥样硬化具有潜在的治疗意义。在我的三个特定目标中，我将检验这样的假设：1)多酚激活SIRT1通过LKB1去乙酰化调节AMPK活性；2)多酚和SIRT1通过LKB1/AMPK信号控制体外肝细胞ACC和SREBP及其脂代谢结果；3)SIRT1和LKB1/AMPK在体内的整合功能参与糖尿病高脂血症和动脉粥样硬化的发生以及多酚对代谢性疾病的保护作用。该应用的创新方面包括：对SIRT1作为LKB1/AMPK途径的一种新的上游信号以控制脂代谢的作用的分子机制的新见解，以及SIRT1通过LKB1/AMPK/SREBP信号调节糖尿病的脂代谢和动脉粥样硬化的新概念。因此，建议的研究将侧重于将SIRT1/LKB1/AMPK作为一种新的治疗途径，以利于糖尿病和年龄相关性代谢紊乱的高脂血症和动脉粥样硬化。与公共卫生相关：虽然限制卡路里(CR)可以延长寿命，延缓糖尿病等与年龄相关的疾病的发生，但目前的趋势是，肥胖和糖尿病患者不太可能愿意或能够维持卡路里限制饮食。这就引出了一个重要的问题：“什么样的制剂可以模仿CR的有益效果？”SIRT1/AMPK信号通路的激活将为糖尿病及其血管并发症的干预提供新的治疗靶点。

DESCRIPTION (provided by applicant): Obesity, insulin resistance, diabetes and hyperlipidemia are leading causes of cardiovascular pathology and mortality. SIRT1, a mammalian ortholog of silent information regulator 2 (Sir2), is an NAD-dependent deacetylase mediates the effects of caloric restriction to expend lifespan. The energy sensor AMP-activated protein kinase (AMPK) and its upstream kinase, LKB1, have been implicated in the therapeutic effect of metformin, an anti-diabetic drug used worldwide. My recent studies and others indicate that both master metabolic regulators, SIRT1 and AMP-activated protein kinase (AMPK), are activated by polyphenols including resveratrol present in red wine. However, If and how SIRT1 is linked to AMPK signaling, lipid metabolism and atherosclerosis remains elusive. I have established in vitro hepatocyte models and in vivo models of type 1 and type 2 diabetic LDL receptor-deficient (LDLR-/-) mice to provide new evidence that 1) polyphenols strongly prevent the inhibition of AMPK, and upregulation of acetyl-CoA carboxylase (ACC) and regulatory element binding protein (SREBP), two key downstream effectors of AMPK, and reduce hepatic lipid accumulation, thereby attenuating diabetic hyperlipidemia and atherosclerosis; 2) the stimulation of AMPK and lipid-lowering action of polyphenols are abrogated by inhibition of SIRT1 or AMPK in vitro; 3) hepatocyte overexpression of SIRT1 stimulates AMPK, downregulates SREBP function and lowers lipids in vitro and in vivo. The CENTRAL HYPOTHESIS of this proposal is that SIRT1 activation by polyphenols functions as a novel upstream regulator of LKB1/AMPK signaling to modulate hepatocyte lipid metabolism and has potential therapeutic implications in the hyperlipidemia and atherosclerosis caused by diabetes. In my three SPECIFIC AIMS, I will test the hypothesis that 1) SIRT1 activation by polyphenols regulates AMPK activity via a mechanism underlying deacetylation of LKB1; 2) polyphenols and SIRT1, via LKB1/AMPK signaling, control ACC and SREBP and their lipid metabolic consequences in hepatocytes in vitro; and 3) the in vivo integrated function of SIRT1 and LKB1/AMPK has been implicated in the development of hyperlipidemia and atherosclerosis in diabetes and in the protective effect of polyphenols against metabolic disease. Innovative aspects of the application include: new insights into the molecular mechanism for the function of SIRT1 as a novel upstream signaling of LKB1/AMPK pathway to control lipid metabolism, and the new concept that SIRT1, via LKB1/AMPK/SREBP signaling, regulates lipid metabolism and atherosclerosis in diabetes. Thus, the proposed studies will emphasize targeting SIRT1/LKB1/AMPK as a new therapeutic avenue to benefit hyperlipidemia and atherosclerosis in diabetes and age-related metabolic disorder. PUBLIC HEALTH RELEVANCE: Although caloric restriction (CR) extends the lifespan and delays the onset of age-related diseases such as diabetes, current trends in unlikelihood that patient with obesity and diabetes would be willing or able to maintain a calorie-restricted diet. This situation gives rise to an important question: "what agents can mimic the beneficial effect of CR?". Ongoing work will employ both in vitro hepatocyte model and in vivo type 2 diabetic mouse models to determine how polyphenols including resveratrol, which is present in red wine and polyphenol-rich fruits, and mimics the beneficial effect of CR, protects against hyperlipidemia and accelerated atherosclerosis in diabetes through activation of the longevity factor SIRT1 and the energy sensor AMPK signaling. Activation of SIRT1/AMPK signaling will provide new therapeutic targets for intervention of diabetes and its vascular complications.