Role of GPR40 in the regulation of insulin secretion

描述（由申请方提供）：脂肪酸急性刺激胰岛素分泌，但慢性损害胰腺β细胞功能，这种现象可能在2型糖尿病的发病机制中发挥作用。最近，已经提出了在β细胞表面特异性表达的G蛋白偶联受体作为长链脂肪酸受体。这挑战了目前的教条，即脂肪酸对胰岛素分泌的影响是由其跨膜转运和细胞内代谢介导的。本提案中描述的工作的总体目标是确定G蛋白偶联受体GPR 40在胰腺β细胞功能中的作用。我们获得的初步数据显示，gpr 40-/-小鼠发生葡萄糖耐受不良，从这些小鼠分离的胰岛具有缺陷的脂肪酸增强胰岛素分泌。基于这些初步发现，我们的假设是GPR 40在长链脂肪酸调节胰岛素分泌中起着重要作用。具体目标1是评估gpr 40的靶向缺失是否影响小鼠的葡萄糖稳态和胰岛素分泌，并在高脂喂养时加速糖尿病的发作。我们假设GPR 40的缺乏将损害体内葡萄糖稳态。我们的初步研究结果支持这一假设，但需要进一步证实，通过测量胰岛素分泌的各种促分泌素，以及在体内不同年龄的胰岛素敏感性。我们进一步假设，在高脂饮食诱导的胰岛素抵抗的背景下，GPR 40的缺乏将促使糖尿病的发作。具体目标2是确定GPR 40功能的丧失是否损害分离的小鼠胰岛中的燃料代谢和胰岛素分泌。我们假设从gpr 40 KO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诱导的胰岛素释放受损支持这一假设，但需要进一步证实，通过测量胰岛素分泌的各种营养和非营养刺激，并进行全面评估葡萄糖和FA代谢的胰岛gpr 40-/-小鼠。作为一种替代方法，我们将使用腺病毒技术通过RNA沉默来敲低分离的成年小鼠胰岛中的GPR 40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.