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

描述（由申请人提供）：胰岛长期暴露于脂肪酸被认为是通过损害？细胞特别是，脂肪酸也能急剧增加胰岛素分泌。因此，更好地了解胰岛中脂质代谢的调节，特别是从空间和时间方面，对于预防脂质过载的不良影响的有效策略至关重要。脂肪分化相关蛋白（Adipose differentiation-related protein，ADFP）广泛存在于细胞内的脂滴表面，通过与细胞膜、内质网、线粒体等细胞器的相互作用，在细胞内脂质代谢的空间组织中发挥重要作用。Imai博士实验室的初步数据显示，体内和体外暴露于脂肪酸的人类和小鼠胰岛中ADFP增加。此外，胰岛素分泌细胞（MIN 6）中ADFP的减少损害脂肪酸的使用和脂肪酸对胰岛素分泌的急性增强。因此，今井博士假设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，同时防止脂质过载引起的胰岛功能障碍。将按照以下方式检验该假设。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在该过程中的重要性将通过使用表达shRNA的腺病毒减少人胰岛中的ADFP以及使用ADFP缺陷小鼠体内减少ADFP来证实。ADFP调节胰岛素分泌信号产生的机制将在小鼠胰岛中使用ADFP的shRNA进行研究。具体目标2：分析ADFP在肥胖症胰岛功能障碍发展中的作用。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应激。在此，将使用腺病毒在体外和使用转基因方法在体内测试ADFP上调在预防脂质诱导的胰岛功能障碍中的功效。具体目标3：阐明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不仅限于脂肪酸代谢。从ADFP涉及的几个领域，将研究与胰岛功能相关的两种途径。在如上调节MIN 6细胞和小鼠胰岛中的ADFP水平后，将分析胆固醇代谢和类花生酸产生的变化。 该研究将提供有关胰岛脂质代谢空间和动态调节的创新，独特的信息，这将有助于设计预防和治疗肥胖症中常见的胰岛功能障碍的新方法。 公共卫生相关性：本研究探讨了脂肪分化相关蛋白在脂质过负荷导致的胰岛功能障碍中的作用，脂质过负荷导致肥胖症患者发生糖尿病。预期的结果将提供更好地了解胰岛中脂质代谢的调节，并将促进预防和治疗2型糖尿病的新方法。

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. PUBLIC HEALTH RELEVANCE: This study addresses a role of adipose differentiation-related protein in the development of islet dysfunction from lipid overload that contributes to the development of diabetes in obesity. Anticipated results will provide better understanding of the regulation of lipid metabolism in islets and will facilitate new approaches towards the prevention and treatment of type 2 diabetes.