ACAT2-Derived LDL Cholesteryl Esters In Atherosclerosis

我们观察到ACAT2的基因缺失和基因敲除对动脉粥样硬化具有保护作用 当血浆中的极低密度脂蛋白和低密度脂蛋白从ACAT2衍生的胆固醇酯中耗尽时。的目标是 项目1的研究是定义ACAT2影响胆固醇代谢和 动脉硬化。AIM1.我们建议确定胆固醇油酸是如何促进低密度脂蛋白的 动脉粥样硬化。我们将监测肠道和肝脏中的胆固醇代谢。ACAT2是已知的 催化合成胆固醇酯，以便在肠道过程中通过乳糜粒转运到体内 胆固醇的吸收。AIM2.ACAT2是一个重要的组成部分，有助于调节 肠道胆固醇吸收和我们设计的研究，以确定具体贡献 ACAT2和ABCG5/G8是一种已知的将胆固醇运回细胞外的转运蛋白 进入。AIM2.我们希望确定ACAT2和ABCG5/G8在促进胆固醇方面的相对作用 吸收的同时限制植物类固醇的吸收。最新吸收的乳胶粒胆固醇的命运 其中被酯化的部分将被有效地输送到肝脏，在那里新吸收的膳食 胆固醇为多种途径的胆固醇动态平衡提供底物。这些包括分泌物 进入胆汁，并入质膜，由ACAT2酯化得到CE 在极低密度脂蛋白中分泌或在肝细胞内的细胞质脂滴中储存。目标。我们希望能确定 肝脏中的ACAT2如何指导胆固醇处理的结果。在喂饲胆固醇的过程中， 肝脏CE的存储和分泌量显著增加，这取决于饮食中脂肪的类型。 矛盾的是，当ACAT2基因缺失时，极低密度脂蛋白的甘油三酯分泌增加，而 肝脏中甘油三酯浓度大大降低，胆固醇和胆固醇酯水平 即使在饮食中摄入胆固醇，肝脏的储存和分泌也保持在较低水平，有效地防止了 肝脏脂肪变性。这种脂类代谢变化的机制将被研究。数据表明 ACAT2活性对胆固醇和甘油三酯的代谢调节是不可或缺的，这两种物质都是 由肝脏储存和分泌。AIM4.ACAT2蛋白结构和活性部位的研究 蛋白质也被提出。我们已经确定了一种可能的催化三元反应机理。 酶，我们已经确定了似乎形成活性部位的特定氨基酸残基。在……里面 此外，我们已经确定了单一氨基酸残基似乎与最高度相互作用 ACAT2特异的抑制剂尚未确定，吡咯烯A的目的是。我们已经提出了一些研究，以确定 人血浆中的油酸胆固醇能否作为冠心病患者ACAT2活性的生物标志物。 最终，我们希望在人类中抑制ACAT2将成为现实，提供 预防冠心病和肝脏脂肪变性。

We have observed that gene deletion and gene knockdown of ACAT2 protects against atherosclerosis when VLDL and LDL in plasma are depleted of ACAT2-derived cholesteryl esters. The goal of the research in project 1 is to define the mechanisms by which ACAT2 affects cholesterol metabolism and atherosclerosis. AIM1. We propose to identify how cholesteryl oleate enrichment of LDL promotes atherogeneisis. We will monitor cholesterol metabolism in the intestine and in the liver. ACAT2 is known to catalyze synthesis of cholesteryl esters for transport into the body in chylomicrons during intestinal cholesterol absorption. AIM2. ACAT2 is an important component helping to regulate the efficiency of intestinal cholesterol absorption and we have designed studies to define the specific contributions of ACAT2 together with ABCG5/G8, a transporter that is known to move cholesterol back out of cells after entry. AIM2. We hope to determine the relative roles of ACAT2 and ABCG5/G8 in facilitating cholesterol absorption while limiting plant sterol absorption. The fate of newly absorbed chylomicron cholesterol, most of which is esterified, is to be efficiently delivered to the liver where the influx of newly absorbed dietary cholesterol provides substrate for many pathways of cholesterol homeostasis. These include secretion into bile, incorporation into the plasma membrane, esterification by ACAT2 resulting in CE that get secreted in VLDL or stored in cytoplasmic lipid droplets within hepatocytes. AIMS. We hope to determine how ACAT2 in the liver directs the outcome of cholesterol handling. During cholesterol feeding, the amount of hepatic CE storage and secretion rises significantly depending on the type of fat in the diet. Paradoxically, when the ACAT2 gene has been deleted, triglyceride secretion in VLDL is increased while triglyceride concentration in the liver is greatly reduced and the levels of cholesterol and cholesteryl ester stored and secreted by the liver remain low, even when dietary cholesterol is fed, effectively preventing hepatic steatosis. The mechanism for this shift in lipid metabolism will be investigated. The data suggest that ACAT2 activity is integral to the metabolic regulation of cholesterol and triglyceride both of which are stored and secreted by the liver. AIM4. Studies on the protein structure and active site of the ACAT2 protein are also proposed. We have identified a putative 'catalytic triad' reaction mechanism for the enzyme and we have identified specific amino acid residues that appear to form the active site. In addition, we have identified the single amino acid residue that appears to interact with the most highly ACAT2-specific inhibitor yet identified, pyripyropene A. AIMS. We have proposed studies to identify whether cholesteryl oleate in human plasma can be a biomarker for ACAT2 activity in patients with CHD. Ultimately we would hope that inhibition of ACAT2 in human beings would become a reality providing prevention of CHD and hepatic steatosis.