Apolipoprotein F enhances HDL function

载脂蛋白F增强HDL功能

• 批准号: 9236396
• 负责人: RICHARD E MORTON
• 金额: $ 39.63万
• 依托单位: CLEVELAND CLINIC LERNER COM-CWRU
• 依托单位国家: 美国
• 财政年份: 2016
• 资助国家: 美国
• 起止时间: 2016-12-09 至 2020-11-30
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/9236396
• 关键词: Activities of Daily Living; Address; Affect; Agonist; Animals; Apolipoproteins; Binding; Blood; Blood Proteins; Cholesterol; Cholesterol Esters; Clinical; Complex; Disease; Effectiveness; Excision; Excretory function; F Factor; Fatty acid glycerol esters; Gene Expression; HDL cholesteryl ester; Hamsters; Hepatic; Hepatocyte; High Density Lipoprotein Cholesterol; High Density Lipoproteins; Human; Hyperlipidemia; In Vitro; Intervention; Knowledge; LDL Cholesterol Lipoproteins; Lipids; Lipoproteins; Liver; Low-Density Lipoproteins; Measures; Mediating; Messenger RNA; Metabolic; Metabolic Control; Metabolism; Modeling; Molecular; Movement; Pathway interactions; Peripheral; Pharmaceutical Preparations; Phosphatidylcholine-Sterol O-Acyltransferase; Plasma; Plasma Proteins; Process; Property; Proteins; Reaction; Role; Small Interfering RNA; Surface; Testing; Text; Therapeutic Intervention; Time; Tissues; Triglycerides; Very low density lipoprotein; cardiovascular disorder risk; disorder risk; fighting; human subject; hypercholesterolemia; in vivo; inhibitor/antagonist; insight; knock-down; lipid metabolism; lipoprotein triglyceride; novel; residence; reverse cholesterol transport

PROJECT SUMMARY A major mechanism proposed for HDL's beneficial effect on cardiovascular disease risk is its capacity to promote cholesterol excretion through a process called reverse cholesterol transport (RCT). Elevated HDL cholesterol levels are generally correlated with reduced disease risk. However, recent trials of HDL-raising drugs failed to observe a clinical benefit. This has led to a revised HDL hypothesis where the functional capacity of HDL to promote peripheral cholesterol efflux and RCT, not HDL concentration, is deemed most important for its protective role. Cholesteryl ester transfer protein (CETP) facilitates the net movement of cholesteryl ester (CE) between plasma lipoproteins. In humans, following the conversion of tissue-derived cholesterol to CE on HDL, 70% of HDL CE is transferred by CETP to VLDL and LDL prior to being removal by the liver. Thus, CETP is a central player in the HDL-mediated cholesterol excretion pathway. We have shown in vitro that apolipoprotein F (ApoF) modulates CETP activity by inhibiting lipid transfers involving LDL but stimulating lipid transfer between HDL and VLDL. We hypothesize that ApoF operates as a metabolic switch by redirecting HDL-derived CE to VLDL instead of LDL, and that this reduces plasma LDL cholesterol levels and stimulates RCT. Here, we test this hypothesis and investigate mechanisms controlling ApoF activity. Aim 1 – Determine the role of ApoF in defining the fate of HDL-derived CE – With an established model of siRNA-mediated ApoF knockdown in hamsters, we will quantify how the loss of this key protein modifies the efflux of HDL CE to LDL and VLDL, measure the hepatic clearance of VLDL and LDL CE, and determine the impact of ApoF on HDL function and RCT in chow-fed and fat-fed animals. Aim 2 – Define the mechanism that converts ApoF to its active form and quantify the effect of hyperlipidemia on ApoF concentration and its activation status – Plasma ApoF exists in both active and inactive forms; active ApoF is bound to LDL. Hypercholesterolemic LDL is enriched in ApoF. We hypothesize that the molecular packing of LDL surface lipids controls ApoF binding. We will identify the molecular properties of LDL that correlate with enhanced ApoF binding and rigorously test their role in this process. Total and active ApoF concentrations will be quantified in hyperlipidemic human subjects to determine their possible contribution to aberrant lipoprotein levels. Aim 3 – Determine the factors that control plasma ApoF levels – In fat-fed animals, plasma ApoF is increased but hepatic APOF mRNA levels are decreased. To understand these discordant observa- tions, the molecular mechanisms causing this decrease in APOF mRNA will be determined, and the turnover of plasma ApoF in normolipidemic and hypercholesterolemic hamsters will be compared. We anticipate find- ing that greater association of ApoF with LDL lengthens its plasma residence time. Overall, these studies will provide novel insight into how ApoF regulates CETP activity and enhances the functional properties of HDL.

项目概要 HDL 对心血管疾病风险有益的一个主要机制是它能够 通过称为反向胆固醇转运 (RCT) 的过程促进胆固醇排泄。 胆固醇水平通常与降低疾病风险相关，但最近的试验表明高密度脂蛋白升高。 未能观察到药物的临床益处，这导致了对 HDL 功能假设的修改。 HDL 促进外周胆固醇流出和 RCT 的能力，而不是 HDL 浓度，被认为是最重要的 胆固醇酯转移蛋白 (CETP) 具有重要的保护作用，可促进蛋白质的净移动。 人体血浆脂蛋白之间的胆固醇酯（CE），经过组织衍生的转化。 HDL 上的胆固醇转化为 CE，70% 的 HDL CE 在被去除之前通过 CETP 转移为 VLDL 和 LDL 因此，CETP 是 HDL 介导的胆固醇排泄途径的核心参与者。 体外显示载脂蛋白 F (ApoF) 通过抑制涉及 LDL 的脂质转移来调节 CETP 活性 但刺激 HDL 和 VLDL 之间的脂质转移，我们对 ApoF 作为代谢的作用感到困惑。 通过将 HDL 衍生的 CE 重定向为 VLDL 而不是 LDL 来进行转换，这会降低血浆 LDL 胆固醇 水平并刺激 RCT 在这里，我们测试了这一假设并研究了控制 ApoF 的机制。 目标 1 – 确定 ApoF 在定义 HDL 衍生 CE 的命运中的作用 – 具有既定的目标。 在仓鼠中 siRNA 介导的 ApoF 敲除模型中，我们将量化这种关键蛋白的丢失是如何发生的 改变 HDL CE 向 LDL 和 VLDL 的流出，测量 VLDL 和 LDL CE 的肝脏清除率，以及 确定 ApoF 对饲料喂养和脂肪喂养动物的 HDL 功能和 RCT 的影响 目标 2 – 定义 将 ApoF 转化为其活性形式的机制并量化高脂血症对 ApoF 的影响 浓度及其激活状态 – 血浆 ApoF 存在活性和非活性两种形式； 与 LDL 结合。我们研究了 ApoF 的分子堆积。 LDL 表面脂质控制 ApoF 结合 我们将确定与 LDL 相关的分子特性。 增强 ApoF 结合并严格测试其在此过程中的总 ApoF 浓度和活性 ApoF 浓度。 将在高脂血症人类受试者中进行量化，以确定其对异常的可能贡献 目标 3 – 确定控制血浆 ApoF 水平的因素 – 在脂肪喂养的动物中，血浆 ApoF 增加，但肝脏 APOF mRNA 水平降低。 系统，导致 APOF mRNA 减少的分子机制将被确定，并且周转率 我们预计将比较正常血脂仓鼠和高胆固醇仓鼠的血浆 ApoF。 总的来说，这些研究表明 ApoF 与 ​​LDL 的关联性越大，其血浆停留时间就越长。 为 ApoF 如何调节 CETP 活性和增强 HDL 的功能特性提供了新的见解。