Pathogenesis of Dyslipidemia and Atherosclerosis in the Diabetic State

描述(申请人提供)：糖尿病患者的主要死因是心血管疾病(CVD)。我们的长期目标是确定预防糖尿病患者心血管疾病的新的药物和饮食策略。低密度脂蛋白受体在胆固醇动态平衡中起着核心作用。利用肝脏胰岛素受体基因敲除小鼠，我们以前发现，在高脂肪、高胆固醇饮食存在的情况下，胰岛素产生的低密度脂蛋白受体蛋白增加了五倍，这与改善低密度脂蛋白清除和防止动脉粥样硬化有关(Biddinger等人，Cell Metab.，2008)。胰岛素能够对低密度脂蛋白受体蛋白起到如此深远的保护作用，这是意想不到的。MyLIP是一种E3泛素连接酶，最近从GWAs研究中作为脂蛋白代谢的重要调节因子出现，并被发现泛素化和降解低密度脂蛋白受体。这项建议的总体目标是确定Mylip在糖尿病状态相关的血脂异常和动脉粥样硬化产生中的作用。我们提供了强有力的初步数据，在多种体外和体内模型中，胰岛素抑制Mylip mRNA，糖尿病小鼠表现出Mylip表达增加，低密度脂蛋白受体蛋白减少和高胆固醇血症。在此基础上，我们假设胰岛素抑制Mylip转录，糖尿病状态下Mylip增加导致低密度脂蛋白受体蛋白减少、血脂异常和动脉粥样硬化。我们的目标如下：(1)使用荧光素酶分析来确定胰岛素调节Mylip转录的机制；(2)确定Mylip在介导胰岛素在体外对低密度脂蛋白受体泛素化和半衰期的影响中的作用；以及(3)确定在糖尿病小鼠中敲除Mylip可以在多大程度上预防血脂异常和动脉粥样硬化。Mylip可能是胰岛素和低密度脂蛋白受体之间的一个关键调控节点，可用于治疗干预。这些拟议的研究将为Mylip的调节及其在糖尿病状态中的作用提供重要的见解。

DESCRIPTION (provided by applicant): The leading cause of death in diabetic patients is cardiovascular disease (CVD). Our long-term goal is to identify new pharmacological and dietary strategies for the prevention of CVD in diabetic patients. LDL receptors play a central role in cholesterol homeostasis. Using liver insulin receptor knockout mice, we previously showed that insulin, in the presence of a high-fat, high-cholesterol diet, produces a five-fold increase in LDL receptor protein which correlates with improved LDL clearance and protection from atherosclerosis (Biddinger et al., Cell Metab., 2008). That insulin can exert such a profound, protective effect upon LDL receptor protein was unexpected. Mylip is an E3 ubiquitin ligase that has recently emerged from GWAS studies as an important regulator of lipoprotein metabolism and found to ubiquitinate and degrade the LDL receptor. The overall goal of this proposal is to determine the role of Mylip in producing the dyslipidemia and atherosclerosis associated with the diabetic state. We present strong preliminary data that insulin suppresses Mylip mRNA in multiple in vitro and in vivo models and that diabetic mice show increased Mylip expression, reduced LDL receptor protein and hypercholesterolemia. Based on this, we hypothesize that insulin suppresses Mylip transcription and that increased Mylip in the diabetic state leads to decreased LDL receptor protein, dyslipidemia and atherosclerosis. Our aims are as follows: (1) use luciferase assays to determine the mechanisms by which insulin regulates Mylip transcription; (2) determine the role of Mylip in mediating the effects of insulin on LDL receptor ubiquitination and half-life in vitro; and (3) determine the extent to which knockdown of Mylip in diabetic mice can prevent dyslipidemia and atherosclerosis. Mylip potentially represents a key regulatory node between insulin and the LDL receptor that could be exploited for therapeutic intervention. The proposed studies will provide important insights into the regulation of Mylip and its role in the diabetic state.