Role of the Renin-Angiotensin System in Glucose Homeostasis

项目总结/摘要 在治疗2型糖尿病（T2 D）时，缺乏同时靶向两种缺陷的药物。 β细胞功能和质量。血管紧张素（1-7），肾素-血管紧张素系统的代谢产物，可能填补这一空白; 然而，其潜在的作用机制尚未完全了解。我们的数据显示， 血管紧张素（1-7）的促胰岛素作用依赖于其水解为二肽血管紧张素（1-2）， 后者还在β细胞中传递促存活和增殖作用。血管紧张素（1-2）激活G蛋白- 偶联受体家族C组6成员A（GPRC 6A），我们显示其在胰岛a细胞中表达。此外，本发明还 血管紧张素（1-2）增加细胞源性胰高血糖素样肽-1（GLP-1）的释放，表明其通过 GPRC 6A在α细胞上以旁分泌方式促进胰岛素分泌。事实上，在GLP-1受体缺陷的情况下， 我们发现，血管紧张素（1-2）不能增强胰岛素分泌，但其增强胰岛β细胞分泌的能力， 存活和增殖得以保留。后者表明血管紧张素（1-2）的作用部分是GLP-1受体， 独立的基于这些新数据，我们假设血管紧张素（1-2）通过细胞内增强β细胞功能 胰岛旁分泌信号传导，并通过新的GLP-1非依赖性机制促进β细胞存活/增殖。 以下具体目标解决了这一假设，目的是改善T2 D的治疗选择： 具体目标1。确定血管紧张素（1-2）增加胰岛源性GLP-1的机制 和胰岛素分泌。小鼠（体内）和胰岛（体外）与白喉毒素诱导的a细胞破坏或a 将使用细胞特异性GPRC 6A敲除来确定血管紧张素（1-2）介导的GPRC 6A表达增加是否与血管紧张素（1-2）介导的GPRC 6A表达增加有关。 胰岛素释放分别需要α细胞或α-细胞GPRC 6A。我们将探索GLP-1增加的机制， 释放，并确认在有和没有GLP-1受体或GPRC 6A阻断的人胰岛中的关键发现。 具体目标2。鉴定介导β细胞存活和增殖的信号通路/蛋白质 Ang（1-2）在人胰岛中的作用血管紧张素（1-2）抑制细胞凋亡、减少细胞凋亡的能力， 将在非糖尿病条件下的人胰岛中检查β细胞的去分化和增强增殖， 糖尿病状况。将确定独立于GLP-1或GPRC 6A的机制的贡献。 血管紧张素（1-2）作用的效应物将使用无偏倚磷酸蛋白质组学鉴定，然后使用磷酸化蛋白质组学的缺失/获得来鉴定。 胰岛功能研究将作为治疗靶向效应物的初步筛选。 具体目标3。确定Ang（1-2）是否在体内改善人胰岛功能/存活， Ang（1-7）的水解是否是其抗糖尿病作用所必需的。我们将利用人类的胰岛 移植模型，以确定血管紧张素（1-2）改善β细胞功能/存活和血管紧张素（1 - 2） 糖尿病小鼠此外，我们将测试血管紧张素（1-7）的促胰岛素作用是否需要其水解， 如在体外的情况。后者对于T2 D的临床管理非常重要，因为它将告知 目前正在开发的抗水解血管紧张素（1-7）药物的效用。

PROJECT SUMMARY/ABSTRACT In treating type 2 diabetes (T2D), there is a paucity of medications simultaneously targeting deficits in both β-cell function and mass. Angiotensin(1-7), a metabolite of the renin-angiotensin system, may fill this gap; however, its underlying mechanisms of action are incompletely understood. Our data reveal that the insulinotropic action of angiotensin(1-7) is dependent on its hydrolysis to the dipeptide, angiotensin(1-2), the latter also conveying pro-survival and proliferative effects in β cells. Angiotensin(1-2) activates G-protein- coupled receptor family C group 6 member A (GPRC6A), which we show is expressed in islet a cells. Further, angiotensin(1-2) increases a cell-derived glucagon-like peptide-1 (GLP-1) release, suggesting it acts via GPRC6A on the a cell to promote insulin secretion in a paracrine fashion. Indeed, in GLP-1 receptor deficient islets, we find that angiotensin(1-2) fails to potentiate insulin secretion; however, its ability to enhance β-cell survival and proliferation is retained. The latter suggests angiotensin(1-2)’s action is, in part, GLP-1 receptor- independent. Based on these novel data, we hypothesize angiotensin(1-2) enhances β-cell function via intra- islet paracrine signaling, and promotes β-cell survival/proliferation via a novel GLP-1-independent mechanism. The following specific aims address this hypothesis, with the goal of improving treatment options in T2D: Specific Aim 1. To determine the mechanism by which angiotensin(1-2) increases islet-derived GLP-1 and insulin secretion. Mice (in vivo) and islets (in vitro) with diphtheria toxin-induced a-cell destruction or a cell-specific GPRC6A knockout will be used to determine whether angiotensin(1-2)-mediated increases in insulin release require a cells or a-cell GPRC6A, respectively. We will probe mechanisms for increased GLP-1 release, and confirm key findings in human islets with and without GLP-1 receptor or GPRC6A blockade. Specific Aim 2. To identify signaling pathways/proteins mediating the β-cell survival and proliferative effects of Ang(1-2) in human islets. The ability of angiotensin(1-2) to inhibit apoptosis, reduce dedifferentiation and enhance proliferation of β cells will be examined in human islets under non-diabetic and diabetic conditions. The contribution of mechanisms independent of GLP-1 or GPRC6A will be determined. Effectors of angiotensin(1-2) action will be identified using non-biased phosphoproteomics, then loss-/gain-of- function studies in islets will serve as a preliminary screen for effectors that could be targeted therapeutically. Specific Aim 3. To determine whether Ang(1-2) improves human islet function/survival in vivo, and whether hydrolysis of Ang(1-7) is required for its anti-diabetic effects. We will utilize a human islet transplant model to determine the ability of angiotensin(1-2) to improve β-cell function/survival and glycemia in diabetic mice. Further, we will test whether the insulinotropic action of angiotensin(1-7) requires its hydrolysis, as is the case in vitro. The latter is highly significant for clinical management of T2D because it will inform on the utility of hydrolysis-resistant angiotensin(1-7)-based medications currently in development.