Pathogenesis of Dyslipidemia and Atherosclerosis in the Diabetic State

描述（由申请人提供）：糖尿病患者死亡的主要原因是心血管疾病（CVD）。我们的长期目标是确定预防糖尿病患者CVD的新的药理学和饮食策略。LDL受体在胆固醇稳态中起着重要作用。使用肝脏胰岛素受体敲除小鼠，我们先前表明，在高脂肪、高胆固醇饮食的存在下，胰岛素产生LDL受体蛋白的五倍增加，这与改善的LDL清除和防止动脉粥样硬化相关（Biddinger等人，细胞代谢，2008年）。胰岛素能对LDL受体蛋白产生如此深远的保护作用是出乎意料的。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剂出现，并发现其泛素化和降解LDL受体。本提案的总体目标是确定Mylip在产生与糖尿病状态相关的血脂异常和动脉粥样硬化中的作用。我们提出了强有力的初步数据，胰岛素抑制Mylip mRNA在多个体外和体内模型，糖尿病小鼠显示增加Mylip表达，降低LDL受体蛋白和高胆固醇血症。基于此，我们假设胰岛素抑制Mylip的转录，并且在糖尿病状态下Mylip的增加导致LDL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）使用荧光素酶试验确定胰岛素调节Mylip转录的机制;（2）确定Mylip在体外介导胰岛素对LDL受体泛素化和半衰期的作用;（3）确定糖尿病小鼠中Mylip敲低可预防血脂异常和动脉粥样硬化的程度。Mylip可能代表胰岛素和LDL受体之间的关键调节节点，可用于治疗干预。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.