Sir2 Regulates AMPK and Lipid Metabolism in Diabetes

描述（由申请人提供）：肥胖、胰岛素抵抗、糖尿病和高脂血症是导致心血管疾病和死亡的主要原因。SIRT1是沉默信息调节因子2 （Sir2）的哺乳动物同源基因，是一种依赖于nad的去乙酰化酶，通过调节热量限制来延长寿命。能量传感器amp活化蛋白激酶（AMPK）及其上游激酶LKB1与二甲双胍的治疗效果有关，二甲双胍是一种世界范围内使用的抗糖尿病药物。我最近的研究和其他研究表明，主要的代谢调节因子SIRT1和amp激活的蛋白激酶（AMPK）都被红酒中的多酚（包括白藜芦醇）激活。然而，SIRT1是否以及如何与AMPK信号、脂质代谢和动脉粥样硬化相关联仍然是未知的。我建立了1型和2型糖尿病LDL受体缺陷（LDLR-/-）小鼠的体外肝细胞模型和体内模型，提供了新的证据：1)多酚能强烈抑制AMPK，上调AMPK的两个关键下游效应物乙酰辅酶a羧化酶（ACC）和调节元件结合蛋白（SREBP），减少肝脏脂质积累，从而减轻糖尿病高脂血症和动脉粥样硬化；2)体外抑制SIRT1或AMPK可消除对AMPK的刺激和多酚的降脂作用；3)肝细胞过表达SIRT1刺激AMPK，下调SREBP功能，降低体内外脂质。该建议的中心假设是，多酚激活SIRT1作为LKB1/AMPK信号的新型上游调节剂，调节肝细胞脂质代谢，并在糖尿病引起的高脂血症和动脉粥样硬化中具有潜在的治疗意义。在我的三个SPECIFIC AIMS中，我将测试以下假设：1)多酚激活SIRT1通过LKB1去乙酰化的机制调节AMPK活性；2)体外肝细胞中多酚和SIRT1通过LKB1/AMPK信号传导控制ACC和SREBP及其脂质代谢后果；3) SIRT1和LKB1/AMPK的体内整合功能与糖尿病的高脂血症和动脉粥样硬化的发展以及多酚对代谢性疾病的保护作用有关。该应用的创新方面包括：SIRT1作为LKB1/AMPK通路上游信号控制脂质代谢的分子机制的新见解，以及SIRT1通过LKB1/AMPK/SREBP信号调节糖尿病脂质代谢和动脉粥样硬化的新概念。因此，拟议的研究将强调靶向SIRT1/LKB1/AMPK作为一种新的治疗途径，使高脂血症和动脉粥样硬化在糖尿病和年龄相关代谢障碍中受益。公共卫生相关性：虽然热量限制（CR）可以延长寿命并延缓年龄相关疾病（如糖尿病）的发病，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热量限制饮食。这种情况引发了一个重要的问题：“什么药物可以模拟CR的有益效果？”正在进行的工作将采用体外肝细胞模型和体内2型糖尿病小鼠模型来确定包括白藜芦醇在内的多酚是如何通过激活长寿因子SIRT1和能量传感器AMPK信号来防止高血脂和加速糖尿病动脉粥样硬化的。白藜芦醇存在于红酒和富含多酚的水果中，并模拟CR的有益作用。SIRT1/AMPK信号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.