Lipid Metabolism and Beta-cell Function

项目摘要/摘要 美国人饮食中的质变与2型糖尿病的发展有关 (T2 DM)。T2 DM发病过程中的一个重要组成部分是β细胞葡萄糖刺激胰岛素受损 分泌物(GSIS)。饱和长链脂肪酸(FA)可增强GSIS，但这两种饮食都会削弱GSIS 注入ω-6多不饱和脂肪酸(PUFA)。黄腐酸的细胞内代谢始于其硫代酯化 通过酰基辅酶A合成酶(ACSL)和辅酶A(CoA)生成酰基辅酶A。我们假设ω-6 多不饱和脂肪酸通过降低β细胞ACSL亚型4的表达来损害GSI和破坏血糖稳态 以及增加未酯化的环氧二十碳三烯酸(EETs)水平。这一假设得到了强有力的支持。 通过几项观察：i)将INS832/13胰岛素瘤β细胞暴露于ω-6多不饱和脂肪酸(花生四烯酸或亚油酸) 不仅损伤GSIS，而且还降低ACSL4的mRNA和蛋白表达；ii)孵育INS 832/13细胞 未酯化的EETs使GSIS降低30%；iii)ACSL4激活EETs形成EET-COAS，这是 结合到甘油脂中，从而防止未酯化的EET积聚和损害GSIS； 以及iv)缺乏β细胞特异性ACSL4的小鼠会出现低血糖和高血糖。在这 提议，我们将检验未酯化的EET损害GSIS以及ACSL4活性是 对于防止未酯化EETs的积累是必不可少的。在目标1中，我们将通过以下方式确定机制 哪些未酯化的EET通过评估EET如何影响胰岛素胞吐的步骤来损害GSIS。在AIM 2，我们将通过确定ω-6如何增加细胞内未酯化EET来确定膳食ω-6多不饱和脂肪酸是如何增加细胞内未酯化EET的 多不饱和脂肪酸调节ACSL4的表达和活性。在目标3中，我们将确定β-cell ACSL4在 在不同高FA饮食环境下维持全身血糖平衡。使用小鼠胰腺 胰岛、β细胞系和动物模型，这项提案将研究独特的和以前未探索的途径 在调节胰岛素分泌方面。EETs对胰岛素分泌的控制是全新的，应该 从而对T2 DM患者的胰岛素缺乏有了新的认识。此外，我们的β细胞特异性ACSL4基因敲除 小鼠提供了一种新的T2 DM模型，模拟了人类存在的胰岛素分泌缺陷 无序。这项提议的预期结果是更多地了解膳食FA如何影响胰岛素 分泌和全身葡萄糖动态平衡。通过研究EETs在β细胞中的代谢，关键 将获得关于胰岛素分泌途径的数据以及不同膳食FAs对其调节的数据。 了解这些机制将使我们能够开发有针对性的饮食疗法来预防和治疗 T2 DM。

PROJECT SUMMARY/ABSTRACT Qualitative changes in the American diet have been linked to the development of type 2 diabetes mellitus (T2DM). An essential component in the development of T2DM is impaired β-cell glucose-stimulated insulin secretion (GSIS). GSIS is augmented by saturated long-chain fatty acids (FA), but is impaired by both dietary and infused ω-6 polyunsaturated FAs (PUFA). Intracellular metabolism of FA begins with its thioesterification by acyl-CoA synthetase (ACSL) with coenzyme A (CoA) to produce an acyl-CoA. We hypothesize that ω-6 PUFA impairs GSIS and disrupts glucose homeostasis by reducing β-cell ACSL isoform 4 (ACSL4) expression and increasing levels of unesterified epoxyeicosatrienoic acids (EETs). This hypothesis is strongly supported by several observations: i) exposing INS 832/13 insulinoma β-cells to ω-6 PUFAs (arachidonate or linoleate) not only impairs GSIS, but also reduces ACSL4 mRNA and protein expression; ii) incubating INS 832/13 cells with unesterified EETs decreases GSIS by 30%; iii) ACSL4 activates EETs to form EET-CoAs, which are incorporated into glycerolipids, thereby preventing unesterified EETs from accumulating and impairing GSIS; and iv) mice that are deficient in β-cell-specific ACSL4 are hypoinsulinemic and hyperglycemic. In this proposal, we will test the specific hypothesis that unesterified EETs impair GSIS and that ACSL4 activity is essential in preventing the accumulation of unesterified EETs. In Aim 1, we will determine the mechanism by which unesterified EETs impair GSIS by evaluating how EETs affect steps in the exocytosis of insulin. In Aim 2, we will determine how dietary ω-6 PUFA increase intracellular unesterified EETs by determining how ω-6 PUFAs regulate ACSL4 expression and activity. In Aim 3, we will determine the role of β-cell ACSL4 in maintaining whole body glucose homeostasis in the setting of different high FA diets. Using mouse pancreatic islets, β-cell lines, and animal models, this proposal will examine unique and previously unexplored pathways in the regulation in insulin secretion. The control of insulin exocytosis by EETs is entirely novel, and should lead to new understanding of insulin insufficiency in T2DM. Additionally, our β-cell-specific ACSL4 knockout mouse provides a novel model for T2DM that mimics the insulin secretion defect that is present in the human disorder. The expected outcome of this proposal is a greater knowledge of how dietary FA impact insulin secretion and whole body glucose homeostasis. By investigating the metabolism of EETs in β-cells, critical data will be obtained on the insulin secretory pathway and its regulation by different dietary FAs. Understanding these mechanisms will enable us to develop targeted dietary therapies to prevent and treat T2DM.