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.

项目总结 高密度脂蛋白对心血管疾病风险有益作用的一个主要机制是它能够 通过一种称为反向胆固醇转运(RCT)的过程来促进胆固醇的排泄。高密度脂蛋白 胆固醇水平通常与疾病风险的降低相关。然而，最近关于提高高密度脂蛋白的试验 药物未能观察到临床益处。这导致了一个修订的高密度脂蛋白假说，其中功能 高密度脂蛋白促进外周胆固醇流出和RCT的能力被认为是最大的，而不是高密度脂蛋白浓度 因为它的保护作用很重要。胆固醇酯转运蛋白(CETP)促进细胞的净运动 血浆脂蛋白之间的胆固醇酯(CE)。在人类中，在组织来源的转化之后 胆固醇在高密度脂蛋白上，70%的高密度脂蛋白在被去除之前被CETP转移到极低密度脂蛋白和低密度脂蛋白 通过肝脏。因此，CETP是高密度脂蛋白介导的胆固醇排泄途径中的核心角色。我们有 体外研究表明，载脂蛋白F(APOF)通过抑制涉及低密度脂蛋白的脂质转移来调节CETP活性 而是刺激高密度脂蛋白和极低密度脂蛋白之间的脂质转移。我们假设APOF作为一种新陈代谢来运作 通过将高密度脂蛋白衍生的CE重定向到极低密度脂蛋白而不是低密度脂蛋白，这可以降低血浆低密度脂蛋白胆固醇 提高和刺激RCT。在这里，我们检验了这一假说，并研究了APOF的控制机制 活动。目标1-确定载脂蛋白F在决定高密度脂蛋白衍生的CE命运中的作用-具有既定的 在仓鼠中siRNA介导的APOF基因敲除模型中，我们将量化这一关键蛋白的损失 将高密度脂蛋白CE的外流修饰为低密度脂蛋白和极低密度脂蛋白，测定肝脏对极低密度脂蛋白和低密度脂蛋白的清除。 确定载脂蛋白对饲喂和饲喂脂肪的动物的高密度脂蛋白功能和RCT的影响。目标2-定义 APOF转化为活性形式的机制及高脂血症对APOF影响的量化 浓度及其激活状态-血浆载脂蛋白有活性和非活性两种形式；活性载脂蛋白是 与低密度脂蛋白结合。高胆固醇血症的低密度脂蛋白富含载脂蛋白。我们假设，分子堆积 低密度脂蛋白表面脂类控制APOF结合。我们将确定与低密度脂蛋白相关的分子特性 增强的APOF结合，并严格测试它们在这一过程中的作用。总载脂蛋白和活性载脂蛋白浓度 将在高脂血症受试者中进行量化，以确定他们对异常的可能贡献 脂蛋白水平。目标3-确定控制血浆载脂蛋白水平的因素-在脂肪喂养的动物中，血浆 APOF水平升高，但肝脏APOF基因表达水平降低。为了理解这些不一致的观察结果- 因此，我们将研究APOF基因表达下降的分子机制，并探讨APOF基因的转移率。 我们将比较正常血脂和高胆固醇血症仓鼠的血浆载脂蛋白水平。我们期待着找到- 增加载脂蛋白与低密度脂蛋白的相关性可延长其血浆停留时间。总体而言，这些研究将 为APOF如何调节CETP活性和增强高密度脂蛋白的功能特性提供了新的见解。