The role of hepatic insulin resistance on SR-BI dependant HDL cholesterol uptake

肝脏胰岛素抵抗对 SR-BI 依赖性 HDL 胆固醇摄取的作用

• 批准号: 8613990
• 负责人: Gregory A Graf
• 金额: $ 38.11万
• 依托单位: UNIVERSITY OF KENTUCKY
• 依托单位国家: 美国
• 财政年份: 2013
• 资助国家: 美国
• 起止时间: 2013-09-20 至 2017-08-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/8613990
• 关键词: 1-Phosphatidylinositol 3-Kinase; Affect; Back; Bile fluid; Biliary; Cardiovascular Diseases; Cell membrane; Cell surface; Cholesterol; Cholesterol Esters; Cholesterol Homeostasis; Data; Dependence; Dominant-Negative Mutation; Elements; Excretory function; Feces; Functional disorder; Future; HDL cholesteryl ester; HDL receptor; Hepatic; Hepatocyte; High Density Lipoprotein Cholesterol; High Density Lipoproteins; Hypertriglyceridemia; Insulin; Insulin Receptor; Insulin Resistance; Liver; Low Density Lipoprotein Receptor; Mediating; Metabolic syndrome; Metabolism; Molecular; Mus; Mutagenesis; Obesity; Outcome; Pathway interactions; Peripheral; Plasma; Play; Process; Publishing; Regulation; Role; Signal Pathway; Signal Transduction; Sterols; Testing; Therapeutic; Tissues; Very low density lipoprotein; cardiovascular disorder risk; cardiovascular risk factor; design; insulin signaling; lipoprotein cholesterol; loss of function; macrophage; mouse model; novel; particle; public health relevance; reverse cholesterol transport; trafficking; translational approach; treatment strategy; uptake

DESCRIPTION (provided by applicant): The overall objective of this proposal is to examine the extent to which impaired insulin signaling alters HDL- mediated reverse cholesterol transport (RCT). A key cardioprotective function of HDL is the delivery of excess cholesterol from plasma and tissues to the liver for elimination from the body via RCT. SR-BI is the major hepatic HDL receptor and mediates the selective uptake of HDL cholesterol esters (HDL-CE). Compared to other circulating lipoproteins, cholesterol carried on HDL particles is preferentially secreted int bile in an SR-BI dependent manner. In addition to SR-BI's role in trans-hepatic sterol transport, both gain and loss-of-function studies have established that SR-BI is a determinant of hepatic cholesterol metabolism including cholesterol synthesis, biliary cholesterol secretion rates and the incorporation of cholesterol into VLDL. Both HDL-CE uptake and biliary cholesterol secretion have been shown to be negatively affected by impaired insulin signaling, a key contributing element to the Metabolic Syndrome (MetS) and the increased risk for cardiovascular disease. Our published and preliminary data indicate that insulin signaling regulates SR-BI by a novel post-translational mechanism that promotes SR-BI expression on the plasma membrane. We hypothesize that insulin resistance reduces HDL-CE uptake and alters SR-BI-dependent delivery of cholesterol to hepatic regulatory and secretory pools through mechanisms that include the redistribution of SR-BI to an intracellular compartment. Specific Aim 1 will determine the effect of hepatic insulin signaling and insulin resistance on SR-BI mediated sterol trafficking to secretory and regulatory hepatic cholesterol pools. Hepatic insulin signaling will be disrupted by selective depletion of insulin receptors or by expression of a dominant negative phosphatidylinositol-3 kinase (AdnilPI3K) and the extent to which hepatic insulin resistance reduces SR-BI mediated HDL-C selective cholesterol ester uptake determined. Studies will also determine how reduced SR-BI function alters steady-state hepatic cholesterol synthesis and secretion in the setting of impaired insulin signaling? Specific Aim 2 will test the hypothesis tha transhepatic (THCE) elimination of HDL cholesterol in bile is reduced in the setting of hepatic insulin resistance and hypertriglyceridemia. This will be accomplished by a) determining whether reduced SR-BI function diminishes THCE of HDL-C, b) determining whether hepatic IR decreases macrophage to feces RCT in an SR-BI dependent manner, and c) examining whether changes in HDL particle composition disrupt THCE of HDL-C and synergize with SR-BI dysfunction to reduce HDL RCT function. Specific Aim 3 will determine the molecular mechanisms by which insulin signaling regulates SR-BI cell surface localization in hepatocytes. The effect of insulin-dependent PI3K signaling on SR- BI subcellular distribution will be examined in cultured hepatocytes, together with the identity of the intracellular compartment(s) in which SR-BI accumulates as a result of impaired insulin signaling. The responsible insulin- dependent signaling pathways will be defined and studies will be performed to identify the determinants on SR- BI necessary for its regulation by insulin signaling.

描述（由申请人提供）：该提案的总体目标是检查受损的胰岛素信号传导改变HDL介导的反向胆固醇转运（RCT）的程度。 HDL 的一个关键心脏保护功能是将血浆和组织中的过量胆固醇输送到肝脏，然后通过 RCT 从体内消除。 SR-BI 是主要的肝脏 HDL 受体，介导 HDL 胆固醇酯 (HDL-CE) 的选择性摄取。与其他循环脂蛋白相比，HDL颗粒上携带的胆固醇优先以SR-BI依赖性方式分泌到胆汁中。除了 SR-BI 在跨肝甾醇转运中的作用外，功能获得和丧失的研究都已证实 SR-BI 是肝脏胆固醇代谢的决定因素，包括胆固醇合成、胆汁胆固醇分泌率和胆固醇掺入到胆固醇中。极低密度脂蛋白。 HDL-CE 摄取和胆汁胆固醇分泌均已被证明会受到胰岛素信号传导受损的负面影响，胰岛素信号传导受损是导致代谢综合征 (MetS) 和心血管疾病风险增加的关键因素。我们发表的初步数据表明，胰岛素信号传导通过一种新的翻译后机制调节 SR-BI，该机制促进 SR-BI 在质膜上的表达。我们假设胰岛素抵抗会减少 HDL-CE 的摄取，并通过将 SR-BI 重新分配到细胞内区室等机制，改变 SR-BI 依赖性胆固醇向肝脏调节和分泌库的传递。具体目标 1 将确定肝脏胰岛素信号传导和胰岛素抵抗对 SR-BI 介导的甾醇运输的影响 分泌和调节肝胆固醇库。选择性耗尽胰岛素受体或显性负性磷脂酰肌醇-3 激酶 (AdnilPI3K) 的表达会破坏肝脏胰岛素信号传导，并确定肝脏胰岛素抵抗降低 SR-BI 介导的 HDL-C 选择性胆固醇酯摄取的程度。研究还将确定在胰岛素信号传导受损的情况下，SR-BI 功能降低如何改变稳态肝脏胆固醇合成和分泌？具体目标 2 将检验以下假设：在肝脏胰岛素抵抗和高甘油三酯血症的情况下，胆汁中 HDL 胆固醇的经肝 (THCE) 消除会减少。这将通过 a) 确定 SR-BI 功能降低是否会减少 HDL-C 的 THCE，b) 确定肝脏 IR 是否以 SR-BI 依赖性方式减少巨噬细胞到粪便的 RCT，以及 c) 检查 HDL 颗粒组成是否发生变化来实现破坏 HDL-C 的 THCE 并与 SR-BI 功能障碍协同作用，降低 HDL RCT 功能。具体目标 3 将确定胰岛素信号传导调节肝细胞中 SR-BI 细胞表面定位的分子机制。将在培养的肝细胞中检查胰岛素依赖性PI3K信号转导对SR-BI亚细胞分布的影响，以及由于胰岛素信号转导受损而导致SR-BI积聚的细胞内区室的身份。将定义负责的胰岛素依赖性信号传导途径，并进行研究以确定胰岛素信号传导调节 SR-BI 所必需的决定因素。