Regulation of Insulin sensitivity by Glucocorticoid-Angiopoietin-like 4-Ceramide Axis

糖皮质激素-血管生成素样 4-神经酰胺轴调节胰岛素敏感性

基本信息

批准号：
10064621
负责人：
Jen-Chywan Wang
金额：
$ 36.27万
依托单位：
UNIVERSITY OF CALIFORNIA BERKELEY
依托单位国家：
美国
项目类别：
财政年份：
2017
资助国家：
美国
起止时间：
2017-12-07 至 2022-11-30
项目状态：
已结题

来源：
https://reporter.nih.gov/project-details/10064621
关键词：
ANGPTL4 gene Adipocytes Adipose tissue Attenuated Biology Cardiovascular Diseases Ceramides Chronic Data Disease Dyslipidemias Exposure to Fasting Fatty Acids Fatty Liver Fibrinogen Functional disorder Genes Genetic Transcription Glucocorticoids Glucose Glucose Clamp Goals Hepatic Hypertriglyceridemia Impairment Insulin Insulin Resistance Knockout Mice Knowledge Lipid Mobilization Lipolysis Liver Mediating Metabolic Metabolic Diseases Modeling Molecular Molecular Target Mus Non-Insulin-Dependent Diabetes Mellitus Nonesterified Fatty Acids Outcome Study PPAR alpha Pathway interactions Peripheral Play Process Production Protein Phosphatase 2A Regulatory Subunit PR53 Proteins Risk Role Signal Transduction Stress Synthetic Genes Testing Therapeutic Intervention Time Tissues base dihydroceramide desaturase expectation extracellular fatty acid transport glucose production improved insight insulin regulation insulin sensitivity lipoprotein lipase novel overexpression response thermozymocidin transcriptome sequencing uptake

项目摘要

Abstract Glucocorticoids (GC) play a key role in metabolic adaptation during stress. However, chronic exposure to GC, is harmful and results in disorders such as insulin resistance. We previously identified angiopoietin-like 4 (Angptl4) as a GC-regulated gene encoding a secreted protein that promotes adipocyte lipolysis and inhibits extracellular lipoprotein lipase (LPL). We showed that Angptl4 is required for GC-promoted lipolysis in white adipose tissue (WAT) and in Angptl4 null mice (Angptl4-/-), excess GC-induced fatty liver and hypertriglyceridemia are diminished. Our recent preliminary studies further demonstrated that GC-induced insulin resistance was compromised in Angptl4-/- mice. Intriguingly, GC treatment increased hepatic ceramide levels, but such GC effect was attenuated in the absence of Angptl4. Indeed, myriocin, which inhibits ceramide synthesis, decreased GC-induced insulin resistance in wild type (WT) but not Angptl4-/- mice. We additionally found that GC exposure elevated the activity of PP2A and PKCζ (two downstream effectors of ceramides) as well as the expression of a list of ceramide synthetic genes in liver. In Angptl4-/- mice, the activity of PP2A and PKCζ was mitigated and the expression of ceramide synthase 3-6 (Cers3-6) was specifically impaired. Based on these preliminary data, we hypothesize that GC augment the expression of Angptl4, which promotes WAT lipolysis mobilizing fatty acids (FA) to liver to serve as substrates and signals required for GC to increase Cers3-6 expression. This elevates the production of specific ceramide species to activate PP2A and PKCζ to suppress insulin action. In this proposal, we will examine this model. In Aim 1, our preliminary study found that the fibrinogen-like domain (FLD) of Angptl4 promotes adipocyte lipolysis without inhibiting LPL. We will test whether FLD restores GC-induced insulin resistance in Angptl4-/- mice. We will also examine the role of FA mobilization to the liver in GC-induced insulin resistance using mice with reduced expression of two major hepatic FA transporters, Fatp5 and Cd36. Moreover, hyperinsulinemic- euglycemic clamps will be used to determine the role of Angptl4 in GC-augmented hepatic glucose production, a hallmark of hepatic insulin resistance. In Aim 2, we will determine which ceramide synthase(s), Cers3-6, are involved in GC-induced insulin resistance. PPARα can be activated by FA and has been shown to increase ceramide synthesis in certain tissues. Thus, its role in GC-induced hepatic Cers3-6 expression and ceramide production will be examined. In Aim 3, we will analyze the role of PP2A and PKCζ in GC- induced insulin resistance and will identify ceramide synthase(s) that activate PP2A and PKCζ to cause insulin resistance. Overall, this study will be the first to establish the FLD of Angptl4 as a lipid mobilization factor participating in GC-induced insulin resistance and for the first time, specific ceramide synthases that activate PKCζ and PP2A will be identified. These findings will advance our understanding of the mechanism of insulin resistance and will provide novel molecular targets for improving insulin sensitivity. ! !

抽象的糖皮质激素（GC）在压力期间在代谢适应中起关键作用。但是，长期暴露于 GC是有害的，会导致胰岛素抵抗等疾病。我们以前确定了类似血管素的4 （ANGPTL4）作为编码GC调节的基因，该基因编码促进脂肪细胞脂肪并抑制的秘密蛋白细胞外脂蛋白脂肪酶（LPL）。我们表明，白色GC促进脂解需要ANGPTL4 脂肪组织（WAT）和Angptl4 null小鼠（Angptl4 - / - ）超过GC诱导的脂肪肝和高甘油三酯血症减少。我们最近的初步研究进一步证明了GC诱导的胰岛素抵抗在Angptl4 - / - 小鼠中受到损害。有趣的是，GC处理增加了肝神经酰胺水平，但是在没有ANGPTL4的情况下，这种GC效应受到了衰减。确实，肉霉素，抑制神经酰胺的合成，野生型（WT）中GC诱导的胰岛素耐药性降低，而不是ANGPTL4 - / - 小鼠。我们另外发现GC暴露升高了PP2A和PKCζ的活性（两个下游效应神经酰胺）以及肝脏中神经酰胺合成基因列表的表达。在Angptl4 - / - 小鼠中 PP2A和PKCζ的活性得到减轻，神经酰胺合酶3-6的表达（CERS3-6）为特别受损。基于这些初步数据，我们假设GC增强了表达 Angptl4，促进脂解动员脂肪酸（FA）至肝脏作为底物和信号 GC需要增加CERS3-6表达所需。这将特定的神经酰胺规格的产生提升到激活PP2A和PKCζ以抑制胰岛素作用。在此提案中，我们将研究该模型。在AIM 1中，我们的初步研究发现，ANGPTL4的纤维蛋白原样结构域（FLD）促进脂肪细胞脂解不抑制LPL。我们将测试FLD是否恢复了ANGPTL4 - / - 小鼠中GC诱导的胰岛素抵抗。我们还将检查使用与与降低了两个主要的肝FA转运蛋白FATP5和CD36的表达。此外，高胰岛素 - Eugpymemic夹具将用于确定Angptl4在GC增强的肝葡萄糖中的作用生产，是肝胰岛素抵抗的标志。在AIM 2中，我们将确定哪种神经酰胺合酶， CERS3-6参与GC诱导的胰岛素抵抗。 PPARα可以通过FA激活，已显示增加某些组织中的神经酰胺合成。这是它在GC诱导的肝脏CERS3-6表达中的作用将检查神经酰胺的生产。在AIM 3中，我们将分析PP2A和PKCζ在GC-中的作用诱导胰岛素抵抗，并将鉴定激活PP2A和PKCζ的神经酰胺合酶胰岛素抵抗。总体而言，这项研究将是第一个建立Angptl4的FLD作为脂质动员的研究参与GC诱导的胰岛素抵抗的因素，并且首次参与了特定的神经酰胺合酶将确定激活的PKCζ和PP2A。这些发现将提高我们对机制的理解胰岛素抵抗，并将提供新的分子靶标，以提高胰岛素敏感性。呢呢