A role and regulation of glucose responsive lipolysis in pancreatic beta cells

胰腺β细胞中葡萄糖反应性脂肪分解的作用和调节

• 批准号: 10553130
• 负责人: Yumi Imai
• 金额: --
• 依托单位: IOWA CITY VA MEDICAL CENTER
• 依托单位国家: 美国
• 财政年份: 2021
• 资助国家: 美国
• 起止时间: 2021-01-01 至 2024-12-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/10553130
• 关键词: Acceleration; Affect; Beta Cell; Cell physiology; Cells; Data; Defect; Development; Emotional; Event; Exhibits; Exocytosis; Failure; Fatty Acids; Functional disorder; Glucose; Goals; Health; High Prevalence; Human; Impairment; Inflammation; Lipase; Lipid Mobilization; Lipids; Lipolysis; Mental Depression; Modeling; Molecular; Nature; Non-Insulin-Dependent Diabetes Mellitus; Overnutrition; Oxidative Stress; Pathogenesis; Pathway interactions; Phenotype; Physiological; Population; Post-Traumatic Stress Disorders; Prevalence; Process; Protein S; Regulation; Reporting; Role; SNAP receptor; Shiga-Like Toxin I; Signal Transduction; Stress; Structure of beta Cell of islet; Testing; Triglycerides; Type 2 diabetic; Veterans; blood glucose regulation; endocrine pancreas development; endoplasmic reticulum stress; functional decline; functional loss; improved; insulin granule; insulin secretion; insulin sensitivity; islet; knock-down; mitochondrial dysfunction; non-diabetic; novel; palmitoylation; perilipin; pharmacologic; preservation; prevent; protein complex; response; syntaxin 1A

T2D is a major health problem for US veterans that imposes significant physical, financial, and emotional tolls. Thus, there is a strong and urgent need for an effective and widely applicable therapy. Excessive accumulation of lipids in beta cells is considered to contribute to the development of T2D. Experimental data supports that lipid overload activates multiple stress pathways including inflammation, ER stress, oxidative stress, and mitochondrial dysfunction ultimately leading to the loss of functional beta cell mass. We have found evidence that the accumulation of triglycerides (TG) in human islets from T2D donors is associated with dysregulation of lipolysis, a previously unrecognized defect in T2D islets that accelerates TG accumulation in T2D islets. Glucose activates lipolysis in non-diabetic human islets but not in T2D islets. Furthermore, our preliminary data indicates that the dysregulation of lipolysis impairs insulin secretion by reducing the stability of syntaxin1a (Stx1a), one of the SNARE complex proteins important for exocytosis. When we tested the impact of dysregulation of lipolysis using human pseudoislets in which the expression of the principal TG lipase (ATGL) is down-regulated, ATGL deficient human pseudoislets showed excessive lipid droplet (LD) accumulation and impaired insulin secretion along with proteasomal degradation of Stx1a. Importantly, the reduction of Stx1a is a defect reported in human T2D islets. Thus, we hypothesize that the dysregulation of lipolysis in response to glucose reduces the stability of Stx1a and impairs insulin secretion in T2D islets. To understand molecular mechanism behind the defects in T2D islets, it will be imperative to determine how glucose upregulates lipolysis in beta cells, why glucose fails to upregulate lipolysis in T2D islets, and how the impairment in lipolysis reduces Stx1a. We will approach our questions using human pseudoislets and INS1 cells as models since they exhibit similarity with human islets in LD formation, the regulation of lipolysis, and phenotypes of ATGL deficiency. We expect to obtain novel information regarding how dysregulation of lipid mobilization causes beta cell dysfunction in T2D through the following aims. Specific aim 1: Determine a mechanism by which ATGL increases lipolysis in response to glucose in non-diabetic beta cells We will systematically test potential targets by which glucose increases lipolysis in INS1 cells and non-diabetic human beta cells. Aim 1a will test which glucose generated signals regulates lipolysis in beta cells. Aim 1b-d will test whether glucose increases lipolysis by modifying ATGL, co-lipases, or perilipins. Specific aim 2: Determine a mechanism by which lipolysis is dysregulated in type 2 diabetic beta cells Aim 1 dissects a mechanism by which glucose regulates lipolysis in beta cells. Leveraging on the information from Aim 1, we will determine why T2D islets are unable to increase lipolysis in response to glucose and how we can restore lipolysis in T2D islets. Specific Aim 3: Test the hypothesis that defective lipolysis destabilizes stx1a in T2D islets Stx1a is proposed to contribute to the impairment of insulin secretion in T2D as Stx1a is reduced in islets of T2D models and human islets affected by T2D. However, it has been unknown why Stx1a is reduced in T2D islets. Our preliminary data implicates that the impairment of lipolysis may cause the reduction of Stx1a in T2D islets. Thus, we will test the hypothesis that reduced lipolysis contributes to the reduction of Stx1a in T2D islets through accelerating degradation of Stx1a due to reduced palmitoylation. Our study combines pharmacological and molecular approaches to increase our understanding of the pathogenesis of beta cell dysfunction in T2D. The information obtained will potentially lead us to a novel target that improves beta cell function in T2D by restoring LD mobilization in beta cells.

T2D 是美国退伍军人的一个主要健康问题，给他们带来了巨大的身体、经济和情感损失。 因此，迫切需要一种有效且广泛适用的疗法。 β细胞中脂质的过度积累被认为有助于T2D的发展。 实验数据支持脂质超负荷激活多种应激途径，包括炎症、ER 应激、氧化应激和线粒体功能障碍最终导致功能性β细胞丧失 大量的。我们发现证据表明，来自 T2D 捐献者的人类胰岛中甘油三酯 (TG) 的积累是 与脂肪分解失调相关，脂肪分解是 T2D 胰岛中一种先前未被识别的缺陷，可加速 TG T2D 胰岛中的积累。葡萄糖会激活非糖尿病人胰岛中的脂肪分解作用，但不会激活 T2D 胰岛中的脂肪分解作用。 此外，我们的初步数据表明，脂肪分解失调会通过以下方式损害胰岛素分泌： 降低突触蛋白 1a (Stx1a) 的稳定性，突触蛋白 1a 是对胞吐作用很重要的 SNARE 复合蛋白之一。 当我们使用人类伪胰岛测试脂肪分解失调的影响时，其中表达 主要TG脂肪酶（ATGL）下调，ATGL缺陷的人伪胰岛表现出脂质过多 液滴（LD）积累和胰岛素分泌受损以及 Stx1a 的蛋白酶体降解。 重要的是，Stx1a 的减少是人类 T2D 胰岛中报道的一种缺陷。因此，我们假设 葡萄糖引起的脂肪分解失调会降低 Stx1a 的稳定性并损害胰岛素分泌 T2D 胰岛。为了了解 T2D 胰岛缺陷背后的分子机制，必须 确定葡萄糖如何上调 β 细胞中的脂肪分解，为什么葡萄糖不能上调 T2D 中的脂肪分解 胰岛，以及脂肪分解受损如何减少 Stx1a。我们将使用人类来解决我们的问题 伪胰岛和 INS1 细胞作为模型，因为它们在 LD 形成方面与人类胰岛相似， 脂肪分解的调节和 ATGL 缺乏的表型。我们期望获得有关以下方面的新颖信息 脂质动员失调如何通过以下目标导致 T2D 中的 β 细胞功能障碍。 具体目标 1：确定 ATGL 响应葡萄糖而增加脂肪分解的机制 非糖尿病β细胞 我们将系统地测试葡萄糖增加 INS1 细胞和非糖尿病细胞中脂肪分解的潜在目标 人类β细胞。目标 1a 将测试哪些葡萄糖产生的信号调节 β 细胞中的脂肪分解。目标 1b-d 将测试葡萄糖是否通过修饰 ATGL、辅脂肪酶或周脂质来增加脂肪分解。 具体目标 2：确定 2 型糖尿病 β 细胞中脂肪分解失调的机制 目标 1 剖析了葡萄糖调节 β 细胞脂肪分解的机制。充分利用信息 从目标 1，我们将确定为什么 T2D 胰岛不能响应葡萄糖而增加脂肪分解，以及如何 我们可以恢复 T2D 胰岛的脂肪分解作用。 具体目标 3：检验脂肪分解缺陷导致 T2D 胰岛中 stx1a 不稳定的假设 Stx1a 被认为会导致 T2D 中胰岛素分泌受损，因为 Stx1a 在胰岛中减少 T2D 模型和受 T2D 影响的人类胰岛。然而，尚不清楚为何 Stx1a 在 T2D 中减少 胰岛。我们的初步数据表明，脂肪分解受损可能导致 T2D 中 Stx1a 的减少 胰岛。因此，我们将检验脂肪分解减少导致 T2D 胰岛中 Stx1a 减少的假设 由于棕榈酰化减少，加速 Stx1a 的降解。 我们的研究结合了药理学和分子方法，以增加我们对 T2D β 细胞功能障碍的发病机制。获得的信息可能会引导我们找到一个新的目标 通过恢复 LD 在 β 细胞中的动员来改善 T2D 中的 β 细胞功能。