Cholesterol Toxicity as a Promising Target for Diabetes Prevention

胆固醇毒性是预防糖尿病的一个有希望的目标

基本信息

批准号：
9767799
负责人：
JEFFREY S ELMENDORF
金额：
$ 39.35万
依托单位：
INDIANA UNIV-PURDUE UNIV AT INDIANAPOLIS
依托单位国家：
美国
项目类别：
财政年份：
2018
资助国家：
美国
起止时间：
2018-08-22 至 2021-06-30
项目状态：
已结题

来源：
https://reporter.nih.gov/project-details/9767799
关键词：
ATP-Binding Cassette Transporters Actins Adipocytes Affect Anabolism Animals Binding Caveolae Cell Culture Techniques Cell membrane Cells Cellular Assay Characteristics Cholesterol Cholesterol Homeostasis Clinical Complement DNA Data Defect Development Diabetes Mellitus Diabetes prevention Diagnosis Distal Enzymes Epidemic Event F-Actin Family suidae Fatty acid glycerol esters Functional disorder GLUT4 gene Gene Expression Genes Genetic Transcription Glucose Glucose Intolerance Glucose Plasma Concentration Glucose Transporter Health Hexosamines High Fat Diet Human Hydroxymethylglutaryl-CoA reductase Hyperglycemia Imagery Impairment In Vitro Insulin Insulin Resistance Insulin-Dependent Diabetes Mellitus Investigation Knowledge Link Mediating Membrane Membrane Fusion Membrane Microdomains Modification Molecular Profiling Mus Muscle Muscle Cells Non-Insulin-Dependent Diabetes Mellitus Obesity Pathway interactions Pharmacology Phosphatidic Acid Phosphatidylinositol 4,5-Diphosphate Phosphatidylinositols Positioning Attribute Prediabetes syndrome Prevention Process Production Rattus Regulation Research Resistance development Role Secondary to Sp1 Transcription Factor Structure Testing Therapeutic Tissues Toxic effect Transcriptional Activation Uncertainty Vesicle base blood glucose regulation cholesterol biosynthesis cholesterol transporters diabetes risk enzyme pathway experimental study fasting plasma glucose glucose transport glucose uptake improved in vivo inhibitor/antagonist insulin sensitivity knock-down new therapeutic target novel overexpression phospholipase D1 polymerization prevent response stem uptake

项目摘要

There is little doubt that excess glucose flux through the hexosamine biosynthesis pathway (HBP) can cause insulin resistance. Clinical findings support the contention that glucose-induced insulin resistance likely starts years before the onset of type 2 diabetes, even before prediabetes is recognized. Although a mechanism is not known, in vitro data suggest that increased HBP activity increases O-linked N-acetylglucosamine modification of Sp1, leading to transcriptional activation of HMG-CoA reductase, the rate-limiting enzyme in cholesterol synthesis. This HBP-induced response increases plasma membrane (PM) cholesterol that impairs insulin-stimulated glucose transporter GLUT4-mediated glucose transport. Inhibition of HBP activity or blockade of O-GlcNAc-modified Sp1 binding to DNA prevents PM cholesterol accumulation and GLUT4/glucose transport dysregulation. These cell culture data support a novel hypothesis that the breakdown of glucose homeostasis in insulin resistance is secondary to increased HBP-mediated cholesterol biosynthesis. The fact excess PM cholesterol is seen in vivo suggests that regulatory mechanisms that protect against cellular cholesterol accumulation/toxicity may be defective in insulin-resistant fat/muscle. In support of this possibility, the HBP-cholesterolgenic response also impairs ATP-binding cassette transporter A1 (ABCA1)-mediated cholesterol efflux from insulin-resistant 3T3-L1 adipocytes. Collectively, these data are in accord with recent gene expression studies showing that alterations in a network of cholesterol metabolism genes are associated with T2D risk. Data from cells and tissues suggest PM cholesterol accumulation diminishes cortical filamentous actin (F-actin) important for GLUT4 regulation. Despite this loss of F-actin, preliminary mechanistic studies in insulin-resistant 3T3-L1 adipocytes show GLUT4 storage vesicles (GSVs) are mobilized by insulin to a position just beneath the cholesterol-laden PM but then fail to incorporate and transport glucose. Data suggest that this impairment results from defective phospholipase D1 (PLD1)-mediated production of phosphatidic acid (PA), which is known to promote GSV/PM fusion. This project will determine whether the in vivo increase in PM cholesterol in insulin-resistant fat/muscle is due to HBP-driven Sp1 transcriptional events, and if defective ABCA1 and/or ABCG1-mediated protection against PM cholesterol accumulation occurs exacerbating insulin resistance (Aim 1). With both the regulation of F-actin polymerization and PLD1 activation occurring at cholesterol-enriched caveolae PM microdomains, this project will also determine if excess PM cholesterol-driven defects in these cytoskeletal/membrane GLUT4-regulatory steps are causally linked to insulin resistance (Aim 2). A key postulate of this application is that the development of glucose intolerance in vivo involves a HBP-induced cholesterolgenic response that impairs one or more distal membrane-based mechanisms of GLUT4 regulation. Advancement of this understanding will reshape our understanding of insulin resistance development and identify new therapeutic targets for its prevention and/or treatment.

毫无疑问，通过己胺生物合成途径（HBP）过多的葡萄糖通量会引起胰岛素抵抗。临床发现支持了葡萄糖诱导的胰岛素抵抗可能在2型糖尿病发作之前几年开始的争论，甚至在确认糖尿病前期之前也是如此。尽管尚不清楚一种机制，但体外数据表明，HBP活性增加会增加SP1的O连接的N-乙酰葡萄糖修饰，从而导致HMG-COA还原酶的转录激活，这是胆固醇合成中的速率限制酶。这种HBP诱导的反应增加了质膜（PM）胆固醇，从而损害了胰岛素刺激的葡萄糖转运蛋白GLUT4介导的葡萄糖转运。抑制HBP活性或O-GLCNAC修饰的SP1与DNA结合的阻断可防止PM胆固醇的积累和GLUT4/葡萄糖转运失调。这些细胞培养数据支持一个新的假设，即胰岛素抵抗中葡萄糖稳态的分解是HBP介导的胆固醇生物合成的继发性。在体内看到过量的PM胆固醇表明，预防细胞胆固醇积累/毒性的调节机制在胰岛素耐药性脂肪/肌肉中可能有缺陷。为了支持这种可能性，HBP-胆固醇的反应还会损害ATP结合盒转运蛋白A1（ABCA1）介导的胰岛素3T3-L1脂肪细胞中介导的胆固醇外排。总的来说，这些数据与最近的基因表达研究一致，表明胆固醇代谢基因网络的变化与T2D风险有关。来自细胞和组织的数据表明，PM胆固醇的积累减少了皮质丝状肌动蛋白（F-肌动蛋白）对GLUT4调节很重要。尽管失去了F-肌动蛋白，但在胰岛素耐药3T3-L1脂肪细胞中的初步机理研究表明，GLUT4储藏囊泡（GSV）通过胰岛素动员到含胆固醇含有胆固醇的PM下的位置，但随后未能掺入和转运Glucose。数据表明，这种损害是由缺陷的磷脂酶D1（PLD1）介导的磷脂酸（PA）的产生，该磷脂酸（PA）已知可以促进GSV/PM融合。该项目将确定胰岛素耐药性脂肪/肌肉中PM胆固醇的体内升高是否是由于HBP驱动的SP1转录事件以及ABCA1和/或ABCG1介导的PM胆固醇积累的防护性是否会导致胰岛素抵抗加剧（AIM 1）。随着F-肌动聚合的调节和PLD1激活发生在胆固醇含有的小窝PM微域处，该项目还将确定在这些细胞骨架/膜GLUT4 glut4-调节性步骤中是否有效地将过量的PM PM胆固醇驱动的缺陷与胰岛素抗胰岛素抗性（AIM 2）。该应用的一个关键假设是，体内葡萄糖不耐症的发展涉及HBP诱导的胆固醇反应，从而损害了一种或多种基于远端膜的GLUT4调节机制。这种理解的进步将重塑我们对胰岛素抵抗发展的理解，并确定预防和/或治疗的新治疗靶标。