ACAT2-Derived LDL Cholesteryl Esters In Atherosclerosis

我们已经观察到ACAT 2的基因缺失和基因敲低可以防止动脉粥样硬化 当血浆中的VLDL和LDL耗尽ACAT 2衍生的胆固醇酯时。的目标 项目1的研究是确定ACAT 2影响胆固醇代谢的机制， 动脉粥样硬化AIM 1.我们建议确定胆固醇油酸酯富集LDL如何促进 动脉粥样硬化我们将监测肠道和肝脏中的胆固醇代谢。ACAT 2已知 催化胆固醇酯的合成，以便在肠内消化过程中在乳糜微粒中转运到体内 胆固醇吸收目标2. ACAT 2是一个重要的组成部分，有助于调节 肠道胆固醇吸收，我们设计了研究，以确定具体的贡献， ACAT 2与ABCG 5/G8一起，ABCG 5/G8是一种转运蛋白，已知在胆固醇释放后将胆固醇从细胞中移回。 入境目标2.我们希望确定ACAT 2和ABCG 5/G8在促进胆固醇代谢中的相对作用。 吸收，同时限制植物甾醇的吸收。新吸收的乳糜微粒胆固醇的命运， 被酯化的食物，被有效地输送到肝脏， 胆固醇为胆固醇稳态的许多途径提供底物。其中包括分泌物 进入胆汁，掺入质膜，通过ACAT 2酯化，产生CE， 在VLDL中分泌或储存在肝细胞内的细胞质脂滴中。目标。我们希望能确定 肝脏中的ACAT 2如何指导胆固醇处理的结果。在胆固醇喂养期间， 肝脏CE储存和分泌的量根据饮食中脂肪的类型显著升高。 特别地，当ACAT 2基因缺失时，VLDL中的甘油三酯分泌增加， 肝脏中的甘油三酯浓度大大降低， 肝脏储存和分泌的胆固醇仍然很低，即使在饮食胆固醇被喂养时， 肝脂肪变性将研究脂质代谢中这种转变的机制。数据表明 ACAT 2活性是胆固醇和甘油三酯代谢调节的组成部分， 由肝脏储存和分泌。AIM4. ACAT 2蛋白结构及活性部位的研究 蛋白质也被提出。我们已经确定了一个假定的“催化三元组”反应机制， 我们已经确定了似乎形成活性位点的特定氨基酸残基。在 此外，我们已经确定了一个氨基酸残基，似乎与最高度相互作用， ACAT 2特异性抑制剂尚未确定，啶南平A。目标。我们建议进行研究， 人血浆中的胆固醇油酸酯是否可以作为CHD患者ACAT 2活性的生物标志物。 最终，我们希望人类ACAT 2的抑制能够成为现实， 预防CHD和肝脂肪变性。

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.