Lipid Metabolism and Beta-cell Function

项目总结/摘要 美国人饮食的质的变化与2型糖尿病的发生有关 （T2DM）。2型糖尿病发展的一个重要组成部分是受损的β细胞葡萄糖刺激胰岛素 分泌（GSIS）。饱和长链脂肪酸（FA）可增强GSIS，但饮食中的 并输注ω-6多不饱和脂肪酸（PUFA）。FA的细胞内代谢始于其硫代酯化反应 通过酰基辅酶A合成酶（ACSL）与辅酶A（CoA）反应以产生酰基辅酶A。我们假设ω-6 PUFA通过降低β细胞ACSL亚型4（ACSL 4）表达损害GSIS并破坏葡萄糖稳态 和增加未酯化的环氧二十碳三烯酸（ECO 2）的水平。这一假设得到了有力的支持 通过几项观察：i）将INS 832/13胰岛素瘤β细胞暴露于ω-6 PUFA（花生四烯酸或亚油酸） 不仅损害GSIS，而且降低ACSL 4 mRNA和蛋白质表达; ii）孵育INS 832/13细胞 使用未酯化的EET 4使GSIS降低30%; iii）ACSL 4活化EET 4以形成EET-CoA， 掺入甘油脂中，从而防止未酯化的雌二醇积累和损害GSIS; 和iv）β-细胞特异性ACSL 4缺陷的小鼠是低胰岛素血症和高血糖。在这 我们将检验未酯化的Escherichia coli损害GSIS和ACSL 4活性是 在防止未酯化的雌二醇的积累方面至关重要。在目标1中，我们将通过以下方式确定机制： 其中未酯化的雌二醇通过评估雌二醇如何影响胰岛素胞吐作用中的步骤来损害GSIS。在Aim中 2、我们将通过测定ω-6 PUFA如何增加细胞内未酯化的E2来确定膳食ω-6 PUFA如何增加细胞内未酯化的E2。 PUFA调节ACSL 4的表达和活性。在目标3中，我们将确定β细胞ACSL 4在 在不同高FA饮食的设置中维持全身葡萄糖稳态。使用小鼠胰腺 胰岛，β细胞系和动物模型，这项建议将检查独特的和以前未探索的途径 在调节胰岛素分泌方面的作用。通过雌二醇控制胰岛素胞吐作用是完全新颖的， 导致对T2 DM胰岛素不足的新认识。此外，我们的β细胞特异性ACSL 4敲除 小鼠为T2 DM提供了一种新的模型，其模拟了人中存在的胰岛素分泌缺陷 disorder.该提案的预期结果是更好地了解膳食FA如何影响胰岛素 分泌和全身葡萄糖稳态。通过研究β-细胞中的E2代谢， 将获得关于胰岛素分泌途径及其由不同膳食FA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 2型糖尿病。

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.