Role of lipid droplet protein in obesity and diabetes

细胞内的脂质储存在称为脂滴（LD）的细胞器中，脂滴由中性脂质组成， 甘油二酯、甘油三酯和胆固醇酯被单层磷脂覆盖。最近 有证据表明LD在细胞内脂质代谢的空间和时间调节中起关键作用。 我们的项目旨在通过研究LD在细胞内的作用来了解细胞内脂质代谢的调节。 考虑到脂质在β细胞中的关键作用。脂肪分解产生的代谢产物增加胰岛素 在某些情况下，脂质的不受调节的积累损害β细胞的健康并导致糖尿病。的 脂周蛋白（PLIN 1 -5）家族蛋白存在于LD的表面上，并且在LD的形成和 动员LD。我们的目标是了解PLIN影响胰岛素分泌的机制， 阐明PLIN在2型糖尿病β细胞脂质代谢异常发病机制中的作用 （T2D）。我们已经证明PLIN 2和PLIN 5都在人和小鼠胰岛中表达，但 它们的表达受到不同的调节。我们已经表明，PLIN 5在增加 胰岛素分泌可能通过急性调节脂质代谢，特别是β细胞中的脂解作用。 PLIN 2可以帮助β细胞适应营养应激。因此，我们假设PLIN 2和PLIN 5， 具有独特的分子特征，协调实现胰岛素分泌的有效调节， 在营养压力下保护β细胞。该假设将通过两个目标进行检验。 具体目标1：确定PLIN 5增强GSIS和脂解的机制。PLIN 5垫块 GSIS在体外和体内，我们假设这是由脂解介导的。在这里，我们将描述 连接PLIN 5和GSIS的通路。β细胞中PLIN 5缺乏对葡萄糖稳态的影响 将在β细胞特异性PLIN 5敲除小鼠中进行测试。PLIN 5磷酸化在脂质中的作用 将使用在培养的大肠杆菌中表达的磷酸化抗性突变体PLIN 5来测试代谢和GSIS。 细胞和小鼠的β细胞中。最后，介导PLIN 5增强的分子靶标将是 通过通过突变体PLIN 5增加脂解和脂解的药理学调节来确定。 具体目标2：确定围脂蛋白如何在营养应激下保护β细胞。酵母研究， 果蝇和小鼠肝脏暗示LD保护营养应激下的细胞。在β细胞中，PLIN 2是 高表达并被脂肪酸增加。我们已经获得了初步的数据，PLIN 2的损失， β细胞损害GSIS和胰岛对高脂肪喂养的适应。我们将确定 PLIN 2在营养应激下保护β细胞。此外，我们还将分析胰岛PLIN和脂质体是如何被 在受T2 D影响的人类胰岛中改变。 我们的研究有望确定一个新的目标，支持GSIS和保护β细胞营养不良 与T2 D相关的压力。

Lipids within cells are stored in an organelle termed lipid droplets (LDs) that consist of neutral lipids core of diacylglycerides, triglycerides, and cholesterol ester covered by a single layer of phospholipids. Recent evidence indicates a pivotal role of LD in the spatial and temporal regulation of intracellular lipid metabolism. Our project aims to understand the regulation of intracellular lipid metabolism through the study of LD in beta cells considering the critical role of lipids in beta cell. Metabolites produced by lipolysis augment insulin secretion, while unregulated accumulation of lipids impair beta cell health and leads to diabetes. The perilipin (PLIN1-5) family of proteins resides on the surface of LD and plays a key role in the formation and mobilization of LD. Our goal is to understand the mechanisms by which PLIN affects insulin secretion and to clarify the role of PLIN in the pathogenesis of abnormal lipid metabolism in beta cells under type 2 diabetes (T2D). We have demonstrated that both PLIN2 and PLIN5 are expressed in human and mouse islets, but their expression is differentially regulated. We have shown that PLIN5 plays a significant role in increasing insulin secretion likely through the regulation of lipid metabolism acutely, especially lipolysis in beta cells. PLIN2 may aid adaptation of beta cells to nutritional stress. Thus, we hypothesize that PLIN2 and 5, each with unique molecular characteristics coordinately achieve the efficient regulation of insulin secretion and protect beta cells under nutritional stress. The hypothesis will be tested by 2 aims. Specific Aim 1: Determine the mechanism by which PLIN5 augments GSIS and lipolysis. PLIN5 augments GSIS both in vitro and in vivo, which we hypothesize is mediated by lipolysis. Here, we will delineate the pathway connecting PLIN5 and GSIS. The impact of PLIN5 deficiency in beta cells on glucose homeostasis will be tested in beta cell specific PLIN5 knockout mice. The contribution of PLIN5 phosphorylation in lipid metabolism and GSIS will be tested using phosphorylation resistant mutant PLIN5 expressed in cultured cell and in beta cells of mice. Lastly, the molecular target that mediates the augmentation of PLIN5 will be determined by increase lipolysis through mutant PLIN5 and pharmacological modulation of lipolysis. Specific Aim 2: Determine how perilipins protect beta cells under nutritional stress. Studies in yeast, drosophila, and mouse liver implicate that LDs protect cells under nutritional stress. In beta cells, PLIN2 is highly expressed and increased by fatty acids. We have obtained preliminary data that the loss of PLIN2 in beta cells impair GSIS and islet adaptation to high fat feeding. We will determine the mechanism by which PLIN2 protect beta cells under nutritional stress. Also, we will analyze how islet PLINs and lipidome are altered in human islets affected by T2D. Our study holds promise to identify a new target that supports GSIS and protects beta cells under nutritional stress associated with T2D.