Islet Beta-Cell Dysfunction Under Metabolic Stress

众所周知，胰岛β细胞长期暴露于代谢应激(例如，高 葡萄糖、棕榈酸酯和神经酰胺)会导致代谢功能障碍和功能性β细胞质量的丧失。原创 我们实验室正在进行的研究已经确定了rac1，一种小G蛋白，在 糖毒性条件下胰岛β细胞功能障碍的发病机制。基于已出版的、引人注目的 初步证据，我们现在建议测试代谢应激促进功能的总体假设 和转录激活rac1以促进细胞内氧化应激、线粒体损伤和 衰弱的β细胞最终消亡。我们建议进行系统的研究，以确定关键信号 Rac1激活-失活循环中可能对代谢和功能起作用的蛋白质/因子 胰腺β细胞存在缺陷。本文设计的研究将展示监管作用和相互作用 新型鸟嘌呤核苷酸解离抑制剂GDI1(RhoGDI)和GDI2(LyGDI)(目标1) 和支架蛋白/鸟嘌呤核苷酸交换因子(α4/β-PIX；Aim 2)在功能激活中的作用 胰岛β中的Rac1-暴露在代谢应激下的细胞。目标3中概述的研究将调查推定的(核因子-kB- 介导)胁迫下胰岛β-细胞中Rac1转录激活的机制 代谢压力。我们在目标4的研究中的目标是证明异常转录和功能 在饮食诱导的动物模型中，rac1的激活导致线粒体损伤和胰岛功能障碍 肥胖(DIO)。补充性研究将肯定细胞内产生的神经酰胺在 在我们的体外(AIMS 1-3)和体内(AIM 4)模型系统中诱导胰岛功能障碍。声明的目标是 通过药理学、分子生物学、显微和脂质组学方法在克隆中完成 β-(INS-1832/13)细胞、啮齿动物和人胰岛。我们项目的翻译相关性通过以下方面得到加强 我们的假设在来自T2 DM人类捐赠者的胰岛中得到验证。建议的研究具有创新性。 并具有翻译影响，因为他们将确定导致胰岛β细胞功能障碍的可能机制 在人类糖尿病中。PI和他的合作者在这一领域的长期专业知识将提供独特的 有机会解决胰岛功能在健康和糖尿病方面的这些重要方面。这些数据是从 预计这些调查还将提供可操作的见解，这些见解将影响预防和 包括退伍军人在内的人类2型糖尿病的治疗。

It is well established that chronic exposure of the pancreatic islet β-cells to metabolic stress (e.g., high glucose, palmitate and ceramide) induces metabolic dysfunction and loss of functional β-cell mass. Original and ongoing investigations from our laboratory have defined novel roles for Rac1, a small G-protein, in the pathogenesis of islet β-cell dysfunction under glucolipotoxic conditions. Based on published and compelling preliminary evidence, we now propose to test the overall hypothesis that metabolic stress promotes functional and transcriptional activation of Rac1 to promote intracellular oxidative stress, mitochondrial damage and eventual demise of the effete β-cell. We propose methodical investigations to identify key signaling proteins/factors in the Rac1 activation-deactivation cycle that might contribute to the metabolic and functional defects in the pancreatic β-cell. Studies designed herein will demonstrate regulatory roles and cross-talk between novel of guanine nucleotide dissociation inhibitors, namely GDI1 (RhoGDI) and GDI2 (LyGDI) (Aim 1) and scaffolding proteins/guanine nucleotide exchange factors (α4/β-PIX; Aim 2) in the functional activation of Rac1 in islet β-cells exposed to metabolic stress. Studies outlined in Aim 3 will investigate putative (NF-kB- mediated) mechanisms underlying transcriptional activation of Rac1 in islet β-cells under the duress of metabolic stress. Our goal in studies under Aim 4 is to demonstrate that aberrant transcriptional and functional activation of Rac1 leads to mitochondrial damage and islet dysfunction in an animal model of diet-induced obesity (DIO). Complementary studies will affirm contributory roles for intracellularly generated ceramide in the induction of islet dysfunction in our in vitro (Aims 1-3) and in vivo (Aim 4) model systems. Stated goals are accomplished via pharmacological, molecular biological, microscopic and lipidomics approaches in clonal β- (INS-1 832/13) cells, rodent, and human islets. Translational relevance of our project is enhanced by validation of our hypothesis in islets derived from T2DM human donors. The proposed studies are innovative and carry translational impact since they will identify putative mechanisms that dictate islet β-cell dysfunction in human diabetes. The long-standing expertise of the PI and his collaborators in this field will provide a unique opportunity to address these important aspects of islet function in health and diabetes. The data accrued from these investigations are also expected to provide actionable insights that will impact the prevention and treatment of T2DM in humans including our Veterans.