Effects of Cholesterol in Pancreatic Islets

项目总结/摘要 他汀类药物是最常用的降胆固醇药物;然而，他汀类药物会增加 新发2型糖尿病（T2 D）。虽然这种增加的风险包括他汀类药物损害胰岛β细胞的直接作用， 细胞功能，潜在的机制仍不清楚。随着他汀类药物在美国成年人中的使用趋势， 迫切需要更好地了解他汀类药物如何导致β细胞死亡-这一知识将为我们提供信息。 旨在减少接受他汀类药物治疗的患者进展为T2 D的策略。为此，我们已经产生了 数据显示他汀类药物促进线粒体胆固醇蓄积的作用以前未被认识 在islets。令人惊讶的是，几乎没有关于线粒体胆固醇调节机制的文献 β细胞含量。这一知识差距将在拟议的研究中加以解决，这些研究将侧重于以下方面的作用： 他汀类药物诱导的β细胞毒性中胆固醇转运至线粒体及其后续代谢。 线粒体是胆固醇贫乏的细胞器，并且因此对胆固醇水平的甚至微小的增加高度敏感。 胆固醇含量类固醇生成急性调节蛋白（星星）和密切相关的STARD 3蛋白 介导胆固醇转运到线粒体。我们发现星星和STARD 3在他汀类药物中均上调， 处理的胰岛。在β细胞中，星星过表达导致线粒体胆固醇积累， 胰岛素释放和细胞活力降低。此外，我们的数据表明β细胞代谢能力有限， 因为它们仅表达已知启动胆固醇的细胞色素P450酶中的两种 新陈代谢.其中，只有CYP 27 A1在暴露于他汀类药物的胰岛中下调， miRNA-204增加，可抑制CYP 27 A1 mRNA。我们发现胰岛细胞CYP 27 A1本身的缺乏 促进线粒体胆固醇积累和受损的胰岛素分泌。此外，我们还展示了 线粒体自噬清除他汀类药物处理的胰岛中负载胆固醇的线粒体可防止β细胞功能障碍。 基于我们的数据，我们假设他汀类药物诱导的胆固醇转运和代谢异常 导致线粒体胆固醇积累、线粒体功能障碍、胰岛素释放受损和β细胞 死亡以下具体目标将解决我们的假设： 目的1：确定胆固醇转运到线粒体的贡献，其随后的代谢， 或清除负载胆固醇的线粒体导致他汀类药物诱导的β细胞功能障碍/死亡。 目的2：确定减少星星和/或增加CYP 27 A1表达是否改善了 他汀类药物对体内β细胞功能和质量的有害影响。 目的3：鉴定减轻他汀类药物诱导的胆固醇转运和代谢失调的miR 人类胰岛中的基因 这项研究是创新和重要的，因为研究线粒体胆固醇积累， 他汀类药物诱导的β细胞功能障碍/死亡中的miRNA将为减轻发展T2 D的风险的策略提供信息。

PROJECT SUMMARY/ABSTRACT Statins are the most commonly used cholesterol-lowering medication; however, statins increase the risk of new-onset type 2 diabetes (T2D). While this increased risk includes a direct effect of statins to impair islet β- cell function, the underlying mechanisms remain unclear. With statin use trending up among U.S. adults, there is an urgent need to better understand how statins lead to demise of the β cell – this knowledge will inform strategies aimed at reducing progression to T2D in patients on statin therapy. To this end, we have generated data that show a previously unrecognized effect of statins to promote mitochondrial cholesterol accumulation within islets. Surprisingly, there is almost no literature on mechanisms regulating mitochondrial cholesterol content in β cells. This knowledge gap will be addressed in the proposed studies, which focus on the role of cholesterol transport to mitochondria and its subsequent metabolism in statin-induced β-cell toxicity. Mitochondria are cholesterol-poor organelles, and thus are highly sensitive to even small increases in cholesterol content. Steroidogenic acute regulatory protein (StAR) and the closely related STARD3 protein mediate cholesterol transport to mitochondria. We show that both StAR and STARD3 are upregulated in statin- treated islets. In β cells, StAR overexpression results in mitochondrial cholesterol accumulation, impaired insulin release and reduced cell viability. Also, our data suggest β cells have limited capacity to metabolize cholesterol since they express only two of the cytochrome P450 enzymes known to initiate cholesterol metabolism. Of these, only CYP27A1 is downregulated in islets exposed to statins, and this is accompanied by an increase in miRNA-204, which can suppress CYP27A1 mRNA. We find that lack of islet CYP27A1 per se promotes mitochondrial cholesterol accumulation and impaired insulin secretion. Also, we show stimulating mitophagy to clear cholesterol-laden mitochondria in statin-treated islets protects against β-cell dysfunction. Based on our data, we hypothesize that statin-induced aberrations in cholesterol transport and metabolism lead to mitochondrial cholesterol accumulation, mitochondrial dysfunction, impaired insulin release and β-cell death. The following specific aims will address our hypothesis: Aim 1: To determine the contributions of transport of cholesterol to mitochondria, its subsequent metabolism, or clearance of cholesterol-laden mitochondria to statin-induced β-cell dysfunction/death. Aim 2: To determine whether reducing StAR and/or increasing CYP27A1 expression ameliorates the detrimental effects of statins on β-cell function and mass in vivo. Aim 3: To identify miRs that mitigate statin-induced dysregulation of cholesterol transport and metabolism genes in human islets. This research is innovative and significant, as investigating mitochondrial cholesterol accumulation and miRNAs in statin-induced β-cell dysfunction/death will inform strategies to mitigate the risk of developing T2D.