Role of GPR40 in the regulation of insulin secretion

描述(申请人提供)：脂肪酸强烈刺激胰岛素分泌，但慢性损害胰岛β细胞功能，这一现象可能在2型糖尿病的发病机制中发挥作用。最近，一种在β细胞表面特异表达的G蛋白偶联受体被认为是一种长链脂肪酸受体。这挑战了当前的教条，即脂肪酸对胰岛素分泌的影响是通过它们的跨膜运输和细胞内代谢来调节的。这项研究的总体目标是确定G蛋白偶联受体GPR40在胰岛β细胞功能中的作用。我们已经获得的初步数据显示，GPR40-/-小鼠患上了葡萄糖耐受，并且从这些小鼠分离出来的胰岛对胰岛素分泌的脂肪酸增强作用存在缺陷。基于这些初步发现，我们的假设是GPR40在长链脂肪酸调节胰岛素分泌中起着重要作用。具体目的1是评估GPR40的靶向缺失是否影响小鼠的葡萄糖稳态和胰岛素分泌，并加速高脂饮食导致糖尿病的发生。我们假设GPR40的缺失将破坏体内的葡萄糖稳态。我们的初步发现支持这一假说，但需要通过测量不同年龄段体内对不同促分泌剂的胰岛素分泌以及胰岛素敏感性来进一步证实。我们进一步假设，在高脂饮食诱导的胰岛素抵抗的背景下，GPR40的缺失将加速糖尿病的发生。具体目的2是确定GPR40功能丧失是否会损害分离的小鼠胰岛的燃料代谢和胰岛素分泌。我们假设从GPR40KO小鼠分离的胰岛对FA的反应是胰岛素分泌缺陷。我们的初步数据显示FA诱导的胰岛素释放障碍支持这一假说，但需要通过测量对各种营养和非营养刺激的胰岛素分泌以及对GPR40-/-小鼠胰岛中葡萄糖和FA代谢的全面评估来进一步证实。作为另一种方法，我们将利用腺病毒技术通过RNA沉默来下调GPR40在分离的成年小鼠胰岛中的表达。

DESCRIPTION (provided by applicant): Fatty acids acutely stimulate insulin secretion, but chronically impair pancreatic beta-cell function, a phenomenon likely to play a role in the pathogenesis of type 2 diabetes mellitus. Recently, a G-protein-coupled receptor specifically expressed on the surface of beta cells has been proposed as a long-chain fatty acid receptor. This challenges the current dogma that the effects of fatty acids on insulin secretion are mediated by their transmembrane transport and intracellular metabolism. The overall objective of the work described in this proposal is to define the role of the G-protein coupled receptor GPR40 in pancreatic beta-cell function. We have obtained preliminary data showing that gpr40 -/- mice develop glucose intolerance, and that islets isolated from these mice have defective fatty-acid potentiation of insulin secretion. Based on these preliminary findings, our hypothesis is that GPR40 plays an essential role in the regulation of insulin secretion by long-chain fatty acids. Specific aim 1 is to assess whether targeted deletion of gpr40 affects glucose homeostasis and insulin secretion in mice and precipitates the onset of diabetes upon high-fat feeding. We hypothesize that the lack of GPR40 will impair glucose homeostasis in vivo. Our preliminary findings support this hypothesis, but need to be further substantiated by measuring insulin secretion in response to various secretagogues as well as insulin sensitivity in vivo at different ages. We further hypothesize that the absence of GPR40 will precipitate the onset of diabetes in the context of high-fat diet-induced insulin resistance. Specific aim 2 is to determine whether loss of function of GPR40 impairs fuel metabolism and insulin secretion in isolated mouse islets. We hypothesize that islets isolated from gpr40 KO mice will have defective insulin secretion in response to FA. Our preliminary data showing impairment of FA-induced insulin release support this hypothesis, but need to be further substantiated by measuring insulin secretion in response to a variety of nutrient and non-nutrient stimuli and performing a comprehensive assessment of glucose and FA metabolism in islets from gpr40 -/- mice. As an alternative approach, we will knock down GPR40 expression in isolated adult mouse islets by RNA silencing using adenoviral technology.