Role of GPR40 in the regulation of insulin secretion

描述（申请人提供）：脂肪酸急性刺激胰岛素分泌，但慢性损害胰腺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，一种特异性表达于β细胞表面的g蛋白偶联受体被认为是一种长链脂肪酸受体。这挑战了目前脂肪酸对胰岛素分泌的影响是通过其跨膜转运和细胞内代谢介导的教条。本提案中描述的工作的总体目标是确定g蛋白偶联受体GPR40在胰腺β细胞功能中的作用。我们已经获得的初步数据表明，gpr40 -/-小鼠出现葡萄糖耐受不良，从这些小鼠中分离出的胰岛有缺陷的脂肪酸增强胰岛素分泌。基于这些初步发现，我们假设GPR40在长链脂肪酸调节胰岛素分泌中发挥重要作用。具体目的1是评估gpr40的靶向缺失是否会影响小鼠葡萄糖稳态和胰岛素分泌，并促进高脂肪喂养后糖尿病的发生。我们假设缺乏GPR40会损害体内葡萄糖稳态。我们的初步研究结果支持这一假设，但需要通过测量不同年龄体内胰岛素分泌对各种促分泌剂的反应以及胰岛素敏感性来进一步证实。我们进一步假设，在高脂肪饮食诱导的胰岛素抵抗的情况下，GPR40的缺失会加速糖尿病的发生。具体目的2是确定GPR40功能丧失是否会损害离体小鼠胰岛的燃料代谢和胰岛素分泌。我们假设从gpr40 KO小鼠中分离的胰岛在对FA的反应中会有胰岛素分泌缺陷。我们的初步数据显示，FA诱导的胰岛素释放受损支持了这一假设，但需要通过测量各种营养和非营养刺激下的胰岛素分泌，以及对gpr40 -/-小鼠胰岛中葡萄糖和FA代谢的综合评估来进一步证实。作为一种替代方法，我们将利用腺病毒技术通过RNA沉默来降低离体成年小鼠胰岛中GPR40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.