Direct effect of cholesterol on glucose-stimulated insulin secretion

胆固醇对葡萄糖刺激的胰岛素分泌的直接影响

• 批准号: 7635857
• 负责人: Mingming Hao
• 金额: $ 12.06万
• 依托单位: YALE UNIVERSITY
• 依托单位国家: 美国
• 财政年份: 2007
• 资助国家: 美国
• 起止时间: 2007-07-10 至 2010-06-30
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/7635857
• 关键词: Animal Model; Apolipoprotein E; Cell physiology; Cells; Cholesterol; Cytoplasm; Data; Diabetes Mellitus; Diet; Dietary Cholesterol; Dimerization; Fatty acid glycerol esters; Functional disorder; Genetic; Glucokinase; Glucose; Goals; Hyperlipidemia; In Vitro; Insulin; Link; Membrane Microdomains; Metabolism; Molecular; Mus; Nitric Oxide Synthase Type I; Non-Insulin-Dependent Diabetes Mellitus; Nonesterified Fatty Acids; Obesity; Pancreas; Pathogenesis; Patients; Plasma; Proteins; Reagent; Regulation; Role; Serum; System; Transgenic Animals; diabetic; feeding; in vivo; insight; insulin granule; insulin secretion; islet; novel; research study; response

DESCRIPTION (provided by applicant): The overall goal of the proposed study is to investigate the role of cholesterol, including serum and islet cholesterol, in pancreatic (-cell dysfunction that characterizes the progression of type 2 diabetes. Alteration of pancreatic (-cell function leading to an impaired insulin secretory response to glucose is a hallmark of the transition from the prediabetic to the diabetic state. Among the many contributing factors, lipotoxicity, which refers to the diabetogenic effect of elevated circulating free fatty acids (FFAs) or cellular fat content, has been studied extensively. Despite the fact that cholesterol is often elevated in obese patients along with FFAs, the role of cholesterol in glucose-stimulated insulin secretion (GSIS) from pancreatic (-cells is not well documented. Unlike studies using mice fed on high-fat diets in which a rise in plasma cholesterol is accompanied by increased plasma FFAs, we established systems of isolated islets where cholesterol levels were altered, both in vivo using apoE-deficient mice and in vitro using pharmacological reagents, without changing cellular FFA levels. My preliminary data show a direct link between elevated serum cholesterol, elevated islet cholesterol and reduced GSIS, and that normal secretion can be restored by cholesterol depletion. I also show that the function of two proteins critically involved in GSIS, neuronal nitric oxide synthase (nNOS) and glucokinase (GK), depends on cholesterol-enriched membrane microdomains on the insulin granules. Through performing the proposed study I hope to solidify the conclusions from my preliminary data and provide a detailed molecular mechanism for cholesterol-dependent GSIS. The specific aims are: 1) Determine the role of cholesterol (dietary, plasma, and islet) in GSIS from pancreatic (-cells. 2) Identify the effect of cholesterol on GK regulation in pancreatic (-cells. 3) Investigate the role of membrane microdomains in nNOS regulation of GK in pancreatic (-cells. These studies will provide insights to a more complete understanding of obesity-induced type 2 diabetes and indicate the existence of a novel mechanism linking hyperlipidemia and pathogenesis of type 2 diabetes that is independent of FFAs. Relevance: (-cell dysfunction leading to decreased GSIS is considered the earliest and most relevant sign of type 2 diabetes mellitus. Studies on the link between hyperlipidemia and GSIS have focused mostly on FFAs. The direct effect of cholesterol on (-cell metabolism proposed in this study would open a novel set of mechanisms that may contribute to (-cell dysfunction and the onset of diabetes in obese patients.

描述（由申请人提供）： 这项研究的总体目标是研究胆固醇（包括血清和胰岛胆固醇）在2型糖尿病进展的胰腺β细胞功能障碍中的作用。胰腺β-细胞功能的改变导致对葡萄糖的胰岛素分泌反应受损，这是糖尿病前期向糖尿病状态转变的标志。在许多促成因素中，脂毒性，其指的是升高的循环游离脂肪酸（FFA）或细胞脂肪含量的致糖尿病效应，已被广泛研究。尽管事实上，胆固醇通常在肥胖患者中随着FFA而沿着升高，但胆固醇在葡萄糖刺激的胰腺β细胞胰岛素分泌（GSIS）中的作用没有得到很好的记录。与使用高脂饮食喂养的小鼠的研究不同，在高脂饮食中，血浆胆固醇的升高伴随着血浆FFA的增加，我们建立了分离的胰岛系统，其中胆固醇水平发生了改变，无论是在体内使用apoE缺陷小鼠，还是在体外使用药理学试剂，而不改变细胞FFA水平。我的初步数据显示，血清胆固醇升高、胰岛胆固醇升高和GSIS减少之间存在直接联系，并且胆固醇消耗可以恢复正常分泌。我还表明，关键参与GSIS，神经元型一氧化氮合酶（nNOS）和葡萄糖激酶（GK）的两种蛋白质的功能，取决于胆固醇富集膜微区的胰岛素颗粒。通过进行拟议的研究，我希望巩固我的初步数据的结论，并提供一个详细的胆固醇依赖性GSIS的分子机制。具体目的是：1）确定胆固醇（膳食、血浆和胰岛）在胰腺β细胞GSIS中的作用。2)确定胆固醇对胰腺β细胞GK调节的影响。3)探讨胰腺β细胞膜微区在nNOS调控GK中的作用。这些研究将为更全面地了解肥胖诱导的2型糖尿病提供见解，并表明存在一种新的机制，将高脂血症与2型糖尿病的发病机制联系起来，而这种机制不依赖于FFA。 相关性：导致GSIS降低的β-细胞功能障碍被认为是2型糖尿病最早和最相关的体征。关于高脂血症和GSIS之间联系的研究主要集中在FFA上。本研究中提出的胆固醇对β-细胞代谢的直接影响将开启一套新的机制，可能有助于肥胖患者的β-细胞功能障碍和糖尿病的发病。