REGULATION OF HEPATIC CHOLESTERYL ESTER METABOLISM

肝脏胆固醇酯代谢的调节

• 批准号: 3345101
• 负责人: SIMEON MARGOLIS
• 金额: $ 13.96万
• 依托单位: JOHNS HOPKINS UNIVERSITY
• 依托单位国家: 美国
• 财政年份: 1985
• 资助国家: 美国
• 起止时间: 1985-09-01 至 1988-08-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/3345101
• 关键词: acetyl coA acetyltransferase; catecholamines; cholesterol; cholesterol esters; cyclic AMP; glucagon; hormone regulation /control mechanism; hydroxycholesterols; liver metabolism; mevalonate; phosphorylation; steroid biosynthesis; steroid metabolism; sterol esterase; vasopressins

Hepatic free cholesterol is secreted directly into the bile, is used to form bile acids, is required for lipoprotein production, and regulates the synthesis of cholesterol and receptors for LDL uptake. Cholesteryl ester formation, by acyl CoA: cholesterol acyl transferase (ACAT) and break down by cholesterol ester hydrolase (CEH) is one mechanism to control the cellular content of free cholesterol. Recent studies suggest that covalent phosphorylation regulates the activities of ACAT and the rate-limiting enzymes for cholesterol and bile acid synthesis in the liver and CEH activity in peripheral tissues. The long term objective of these studies is to understand the role of rapid regulation of these enzymes in the overall economy of liver cholesterol. This project is specifically directed toward studies on the effects of phosphorylation on ACAT and CEH. One specific aim is to obtain direct evidence that phosphorylation activates ACAT. These studies involve purifying ACAT, incorporating 32P into ACAT with protein kinases, and demonstrating that cyclic changes in its phosphate content, produced by alternative treatment with phosphatase and protein kinase, correlate with ACAT activity. A second aim is to determine whether hepatic CEH is also controlled by phosphorylation. In this regard, studies similar to those described for ACAT will be carried out with CEH. A third aim is to identify factors that affect cholesteryl ester synthesis and hydrolysis in freshly isolated hepatocytes and to correlate such changes with the activities and phosphorylation states of ACAT and CEH. Initial studies will utilize dibutyryl cAMP. Other agents will include hormones that stimulate protein kinase activity, such as glucagon, vasopressin, and catecholamines, 25-hydroxycholesterol, and mevalonate. The final aim is to examine the effects of in vivo manipulations, such as cholesterol and cholestyramine feeding and mevalonate administration, on the activities and phosphorylation states of ACAT and CEH. These studies have implications for our understanding of atherosclerosis. The balance between cholesterol and its esters may influence cholesterol excretion and hepatic synthesis and uptake of lipoproteins, thereby affecting plasma lipoprotein concentrations. Better knowledge of the regulation of ACAT and CEH in the liver may provide insights into their control in peripheral tissues where cholesteryl ester hydrolysis is required for cholesterol removal by high density lipoproteins.

肝脏游离胆固醇直接分泌到胆汁中，用于 形成胆汁酸，是脂蛋白产生所必需的，并调节 合成胆固醇和LDL吸收受体。 胆固醇酯 形成，通过酰基辅酶A：胆固醇酰基转移酶（ACAT）和分解 胆固醇酯水解酶（CEH）是控制胆固醇合成的机制之一。 游离胆固醇的细胞含量。 最近的研究表明， 磷酸化调节ACAT的活性， 肝脏和CEH中胆固醇和胆汁酸合成酶 在外周组织中的活性。 这些研究的长期目标是 是为了了解这些酶的快速调节作用， 肝脏胆固醇的整体经济性。 该项目具体为 针对磷酸化对ACAT和CEH的影响的研究。 一个具体的目标是获得直接证据， 激活ACAT。 这些研究涉及纯化ACAT，掺入32 P 转化为ACAT与蛋白激酶，并证明， 它的磷酸盐含量，由磷酸酶交替处理产生 和蛋白激酶与ACAT活性相关。 第二个目标是 确定肝CEH是否也受磷酸化控制。 在 在这方面，将进行类似于ACAT所述的研究 与CEH。 第三个目的是确定影响胆固醇的因素。 在新鲜分离的肝细胞中的酯合成和水解， 将这些变化与以下物质的活性和磷酸化状态相关联： ACAT和CEH。 初步研究将使用二丁酰cAMP。 其它试剂 将包括刺激蛋白激酶活性的激素，例如 胰高血糖素、血管加压素和儿茶酚胺、25-羟基胆固醇，以及 甲羟戊酸 最后的目的是检查在体内的影响， 操作，如胆固醇和消胆胺喂养， 甲羟戊酸给药对 ACAT和CEH。 这些研究对我们理解动脉粥样硬化有意义。 胆固醇和其酯之间的平衡可能会影响胆固醇 排泄和肝脏合成和摄取脂蛋白，从而 影响血浆脂蛋白浓度。 更好地了解 ACAT和CEH在肝脏中的调节可以提供对它们的见解。 胆固醇酯水解的外周组织中的控制 高密度脂蛋白去除胆固醇所需的。