Role of Lipid Droplet Proteins in Islet Function in Diabetes and Obesity

描述(申请人提供)：胰岛长期暴露于脂肪酸被认为是通过损害？细胞。矛盾的是，脂肪酸还能显著增加胰岛素的分泌。因此，更好地了解胰岛脂质代谢的调节，特别是从空间和时间角度，对于有效预防脂质超载的不利影响是至关重要的。脂肪分化相关蛋白(ADFP)广泛存在于多种细胞的脂滴表面，通过与细胞膜、内质网、线粒体等细胞内其他细胞器的相互作用，在细胞内脂代谢的空间组织中发挥重要作用。来自Imai博士实验室的初步数据显示，在体内和体外，暴露于脂肪酸的人和小鼠的胰岛中ADFP增加。此外，胰岛素分泌细胞(MIN6)中ADFP的减少损害了脂肪酸的利用和脂肪酸对胰岛素分泌的急性增强。因此Imai博士假设ADFP包被的脂滴在？细胞对于脂肪酸的有效利用至关重要。它们促进脂肪酸衍生的胰岛素分泌信号的产生，同时防止因脂质过载而导致的胰岛功能障碍。这一假设将被检验如下。具体目的1：分析ADFP在脂肪酸急性增加胰岛素分泌中的作用。ADFP在这一过程中的重要性将通过使用表达shRNA的腺病毒来减少人胰岛中的ADFP以及在体内使用ADFP缺陷的小鼠来证实。ADFP调节胰岛素分泌信号产生的机制将利用ADFP的shRNA在小鼠胰岛中进行研究。具体目标2：分析ADFP在肥胖症患者胰岛功能障碍发生中的作用。由于ADFP可以促进脂肪酸的利用？细胞，它潜在地保护胰岛免受脂肪酸过载的压力。在这里，ADFP上调预防脂质诱导的胰岛功能障碍的有效性将在体外用腺病毒进行测试，并在体内使用转基因方法。具体目标3：解决胰岛脂滴在调节脂肪酸-甘油三酯代谢之外的作用。最近在各种细胞中的研究表明，脂滴所起的调节作用并不局限于脂肪酸代谢。从涉及ADFP的几个方面，我们将研究与胰岛功能相关的两条途径。如上所述，在调节MIN6细胞和小鼠胰岛的ADFP水平后，将分析胆固醇代谢和二十烷类化合物产生的变化。这项研究将提供关于胰岛脂肪代谢的空间和动态调节的创新的、独特的信息，这将有助于设计新的方法来预防和治疗肥胖常见的胰岛功能障碍。

DESCRIPTION (provided by applicant): The chronic exposure of islets to fatty acids is believed to promote the development of diabetes in obesity by damaging ? cells. Paradoxically, fatty acids also augment insulin secretion acutely. Therefore a better understanding of the regulation of lipid metabolism in islets, especially from spatial and chronological aspects, is critical for the effective strategy to prevent adverse effects of lipid overload. Adipose differentiation-related protein (ADFP), found on the surface of lipid droplets in wide range of cells, is proposed to play a critical role in spatial organization of intracellular lipid metabolism through the interaction with other intracellular organelles such as cell membrane, ER, and mitochondria. The preliminary data from Dr. Imai's laboratory showed that ADFP is increased in human and mouse islets exposed to fatty acids in vivo and ex vivo. Furthermore the reduction of ADFP in insulin secreting cells (MIN6) impairs fatty acid usage and acute augmentation of insulin secretion by fatty acids. Therefore Dr. Imai hypothesizes that ADFP coated lipid droplets in ? cells are critical for the efficient use of fatty acids. They facilitate the generation of fatty acid derived signaling for insulin secretion, while preventing islet dysfunction from lipid overload. The hypothesis will be tested as below. Specific aim 1: Analyze the role of ADFP in the acute augmentation of insulin secretion by fatty acids. The importance of ADFP in this process will be confirmed by reducing ADFP in human islets using adenovirus expressing shRNA, and in vivo using ADFP deficient mice. The mechanisms by which ADFP regulates the generation of signals for insulin secretion will be studied in mouse islets using shRNA for ADFP. Specific aim 2: Analyze the role of ADFP in the development of islet dysfunction in obesity. Since ADFP may promote fatty acid utilization in ? cells, it potentially protects islet from stress of fatty acid overload. Here the efficacy of ADFP upregulation in the prevention of lipid-induced islet dysfunction will be tested using adenovirus in vitro, and using the transgenic approach in vivo. Specific aim 3: Address the roles of islet lipid droplets beyond the regulation of fatty acids-triglycerides metabolism. Recent studies in various cells indicate that the regulatory role played by lipid droplets is not limited to fatty acid metabolism. From several areas where ADFP is implicated, two pathways relevant to islet function will be studied. The change in cholesterol metabolism and eicosanoids production will be analyzed after modulating ADFP levels in MIN6 cells and mouse islets as above. The study will provide innovative, unique information about the spatial and dynamic regulation of lipid metabolism in islets, which will aid the designing of new approaches towards the prevention and treatment of islet dysfunction commonly seen in obesity.