Hepatic Cholesteryl Ester Metabolism and Cholesterol Elimination

肝脏胆固醇酯代谢和胆固醇消除

• 批准号: 7995051
• 负责人: SHOBHA GHOSH
• 金额: $ 37.38万
• 依托单位: VIRGINIA COMMONWEALTH UNIVERSITY
• 依托单位国家: 美国
• 财政年份: 2010
• 资助国家: 美国
• 起止时间: 2010-07-01 至 2014-04-30
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/7995051
• 关键词: Adenoviruses; Affect; Albumins; Arterial Fatty Streak; Arteries; Atherosclerosis; Attenuated; Bile Acid Biosynthesis Pathway; Bile Acids; Bile fluid; Biliary; Blood; CYP7A1 gene; Cell Culture System; Cells; Characteristics; Chenodeoxycholic Acid; Cholesterol; Cholesterol Esters; Cholesterol Homeostasis; Cholic Acids; Cloning; Coronary Arteriosclerosis; Diet; Endocytosis; Enzymes; Esters; Event; Excision; Excretory function; Feces; Foam Cells; Foundations; Gallbladder; Generations; HDL cholesteryl ester; HDL receptor; Hepatic; Hepatocyte; High Density Lipoproteins; Human; Hydrolysis; Knockout Mice; Laboratories; Lesion; Link; Lipid-Laden Macrophage; Lipoproteins; Liver; Low Density Lipoprotein Receptor; Low-Density Lipoproteins; Mediating; Metabolism; Mixed Function Oxygenases; Modeling; Monitor; Movement; Mus; Organ; Output; Oxidoreductase; Pathway interactions; Peripheral; Phosphatidylcholine-Sterol O-Acyltransferase; Plasma; Play; Prevalence; Prevention; Process; Proteins; Reaction; Regulation; Reporting; Research Project Grants; Role; Route; SR-BI receptor; Serum; Stream; Testing; Tissues; Tracer; Transgenic Mice; Transgenic Organisms; adenoviral-mediated; clinically relevant; esterase; in vivo; lipoprotein cholesterol; macrophage; muricholic acid; operation; public health relevance; recombinase; reverse cholesterol transport; sterol O-acyltransferase 2; uptake; vitamin D3 25-hydroxylase

DESCRIPTION (provided by applicant): Reverse cholesterol transport (RCT) is the major mechanism by which cholesterol is transported from the peripheral tissues including macrophages associated with the artery wall, to liver for the ultimate conversion into bile acids or direct secretion into the bile. Within the cells or while being transported in the blood stream associated with the lipoproteins, cholesterol is mainly present as cholesteryl esters (CE). Thus, the obligatory first and rate-limiting step of RCT is the intracellular hydrolysis of the stored intracellular CE in the peripheral tissues, e.g., macrophage foam cells, and this reaction is catalyzed by a neutral cholesteryl ester hydrolase (CEH). Free or unesterified cholesterol (FC) that is removed by extra-cellular cholesterol acceptors such as HDL is re-esterified by serum LCAT and carried as CE to the liver where it is delivered by selective uptake via scavenger receptor BI (SR-BI). Hydrolysis of CE once again is obligatory to subsequent conversion of released FC to bile acids or direct secretion into bile. Having established the role of human macrophage CEH in regulating the efflux of FC, RCT and thus attenuating diet-induced atherosclerosis in LDLR-/- mice, the PI has recently reported the cloning and characterization of human liver CEH. Over-expression of this enzyme results in intracellular CE mobilization and an increase in bile acid synthesis. Adenovirus- mediated over-expression of CEH in mice led to significant increase in in vivo RCT and increased elimination of cholesterol as secreted bile acids, and this process required the presence of HDL- receptor SR-BI. CEH-mediated CE hydrolysis, therefore, represents a key event regulating the first step in RCT (generation of free cholesterol in macrophage for efflux) as well as the final step (generating free cholesterol for bile acid synthesis or biliary cholesterol secretion). The central hypothesis of this research project is: Hepatic CEH affects RCT by regulating the hydrolysis of intracellular cholesterol esters (endogenously synthesized or delivered via selective uptake from HDL through SR-BI) thereby providing free cholesterol for elimination as bile acids or direct secretion into the bile and is, therefore, potentially anti-atherosclerotic. This hypothesis will be tested by the following four specific aims: Aim 1: To establish the anti-atherosclerotic role of hepatic CEH by developing liver specific CEH transgenic mice. Aim 2: To delineate the mechanism(s) underlying hepatic CEH-mediated regulation of RCT: role of CEH in hydrolyzing CE delivered to liver by scavenger receptor BI (SR-BI) or SR-BII mediated uptake of HDL-associated CE. Aim 3: To determine the role of hepatic CEH in regulating FC availability for neutral or acidic pathways for bile acid synthesis. Aim 4: To obtain in vivo "proof of concept" by liver-specific targeted disruption of CEH in mice and to determine its effect on intracellular CE metabolism and atherosclerosis. PUBLIC HEALTH RELEVANCE: Liver is the only organ responsible for the ultimate elimination of cholesterol from the body as free cholesterol (FC) or bile acids that are excreted in the feces. Cholesterol associated with excess unmodified LDL as well as the cholesterol removed from the peripheral organs including artery wall- associated macrophage foam cells by HDL is taken up by the liver. Both these lipoproteins deliver cholesterol in the form of cholesterol esters (CE) and within liver hydrolysis of these CEs is essential to provide FC for bile acid synthesis or for direct elimination into the bile. This hydrolysis is carried out in the extra-lysosomal compartment by a neutral cholesteryl ester hydrolase (CEH). We have identified the human hepatic CEH and demonstrated its role in increasing bile acid secretion as well as in enhancing the flux of cholesterol from macrophages to bile suggesting an anti-atherosclerotic function of hepatic CEH. The proposed studies will build on this foundation and establish the role of hepatic CEH in not only increasing cholesterol elimination from the body as bile acids but also in attenuating diet-induced atherosclerosis. Given the prevalence of atherosclerosis and coronary artery disease, the current findings are likely to have important clinical relevance.

描述(申请人提供)：胆固醇逆向转运(RCT)是胆固醇从周围组织(包括与动脉壁相关的巨噬细胞)转运到肝脏，最终转化为胆汁酸或直接分泌到胆汁中的主要机制。在细胞内或在与脂蛋白相关的血流中运输时，胆固醇主要以胆固醇酯(CE)的形式存在。因此，RCT必须的第一步也是限速步骤是储存在周围组织(如巨噬细胞泡沫细胞)中的细胞内CE的细胞内水解，该反应由中性胆固醇酯水解酶(CEH)催化。被细胞外胆固醇受体如高密度脂蛋白去除的游离或未酯化的胆固醇(FC)被血清LCAT重新酯化，以CE的形式携带到肝脏，在那里通过清道夫受体BI(SR-BI)选择性地摄取。CE的水解再次是随后将释放的FC转化为胆汁酸或直接分泌到胆汁中所必需的。在证实了人巨噬细胞CEH在调节Fc、RCT外流从而减轻饮食诱导的LDLR-/-小鼠动脉粥样硬化中的作用后，PI最近报道了人肝CEH的克隆和特性。这种酶的过度表达导致细胞内CE的动员和胆汁酸合成的增加。腺病毒介导的CEH在小鼠体内的过表达导致体内RCT显著增加，并增加了胆固醇作为胆汁酸的排泄，这一过程需要高密度脂蛋白受体SR-BI的存在。因此，CEH介导的CE水解是调节RCT(巨噬细胞产生游离胆固醇外流的第一步)和最后一步(产生用于胆汁酸合成或胆汁胆固醇分泌的游离胆固醇)的关键事件。该研究项目的中心假设是：肝脏CEH通过调节细胞内胆固醇酯(内源性合成或通过SR-BI选择性地从高密度脂蛋白中摄取)的水解来影响RCT，从而提供游离胆固醇作为胆汁酸或直接分泌到胆汁中，因此具有潜在的抗动脉粥样硬化作用。这一假说将通过以下四个具体目标来验证：目的1：通过建立肝脏特异的CEH转基因小鼠，建立肝脏CEH的抗动脉粥样硬化作用。目的：阐明CEH调节RCT的机制(S)：CEH在清道夫受体BI(SR-BI)或SR-BII介导的高密度脂蛋白相关CE的摄取中的作用。目的3：确定肝脏CEH在调节胆汁酸合成的中性或酸性途径的FC利用率中的作用。目的：在小鼠体内通过肝脏特异性靶向干扰CEH获得“概念证明”，并确定其对细胞内CE代谢和动脉粥样硬化的影响。 与公共健康相关：肝脏是唯一负责将胆固醇作为游离胆固醇(FC)或胆汁酸从体内最终消除的器官，这些胆汁酸是从粪便中排出的。与过量的未经修饰的低密度脂蛋白相关的胆固醇以及由高密度脂蛋白从包括动脉壁相关的巨噬细胞泡沫细胞在内的外周器官中去除的胆固醇被肝脏吸收。这两种脂蛋白都以胆固醇酯(CE)的形式提供胆固醇，而在肝脏内，这些CE的水解对于提供FC以合成胆汁酸或直接消除到胆汁中是必不可少的。这种水解是在溶酶体外的隔室中由中性胆固醇酯水解酶(CEH)进行的。我们已经鉴定了人的肝脏CEH，并证明了它在增加胆汁酸分泌以及增加胆固醇从巨噬细胞到胆汁的流量方面的作用，表明肝脏CEH具有抗动脉粥样硬化的功能。拟议的研究将建立在此基础上，并确定肝脏CEH不仅作为胆汁酸增加体内胆固醇的清除，而且在减轻饮食诱导的动脉粥样硬化方面的作用。鉴于动脉粥样硬化和冠状动脉疾病的患病率，目前的研究结果可能具有重要的临床意义。