HDL Metabolism Influence of Extracellular Phospholipases

细胞外磷脂酶对 HDL 代谢的影响

• 批准号: 7038292
• 负责人: Daniel James Rader
• 金额: $ 34.82万
• 依托单位: UNIVERSITY OF PENNSYLVANIA
• 依托单位国家: 美国
• 财政年份: 1996
• 资助国家: 美国
• 起止时间: 1996-03-01 至 2009-03-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/7038292
• 关键词: atherosclerosis; blood lipoprotein metabolism; body composition; carboxylic ester hydrolases; cholesterol; clinical research; enzyme activity; enzyme linked immunosorbent assay; functional /structural genomics; gene expression; gene interaction; genetically modified animals; high density lipoproteins; human middle age (35-64); human subject; inflammation; laboratory mouse; lipid structure; lipid transport; lipoprotein lipase; liver metabolism; low density lipoprotein; phospholipids; protein quantitation /detection; protein structure function; site directed mutagenesis

DESCRIPTION (provided by applicant): Plasma levels of high-density lipoprotein (HDL) cholesterol and its major HDL apolipoprotein, apoA-I, are inversely associated with atherosclerotic cardiovascular disease. Plasma HDL cholesterol and apoA-I levels are determined in part by the rate at which they are catabolized, but the mechanisms that modulate their catabolism in vivo remain incompletely understood. Both acute inflammatory states, such as sepsis, and chronic inflammatory states, such as the metabolic syndrome, are associated with low levels of HDL cholesterol and apoA-I, primarily due to increased catabolism. A major underlying hypothesis of this project has been that extracellular phospholipases are upregulated in response to inflammation and modulate systemic HDL metabolism through hydrolysis of HDL phospholipids. We cloned and characterized a new member of the lipase gene family that we termed endothelial lipase (EL). In the current cycle of this project, we have demonstrated that overexpression of EL in mice causes markedly reduced HDL due to increased catabolism, and antibody inhibition of EL in mice causes increased HDL due to reduced catabolism. In this competing renewal proposal, we will focus our efforts on EL toward achieving a greater understanding of its structure-function relationships, metabolic interactions with other genes that influence HDL, association with atherosclerosis, and its relationship to human physiology and pathophysiology. Specific Aim 1: To investigate the differences between EL and its highly homologous relatives LPL and HL with regard to the molecular basis of the lipid and lipoprotein preferences of EL compared with LPL and HL. Specific Aim 2: To test the hypothesis that in the liver, EL interacts with HL and SR-BI to influence HDL metabolism, selective uptake of cholesterol, and reverse cholesterol transport. Specific Aim 3: To determine the effects of chronic hepatic-specific EL expression on atherogenesis in mice. To compare these results with the effects of endothelial-specific EL expression on atherosclerosis. To test the hypotheses that endothelial EL expression influences endothelial physiology. Specific Aim 4: To test the hypothesis that EL is increased in inflammatory conditions in humans and may contribute to the reduced HDL-C levels associated with these conditions. A recent editorial stated: "Perhaps the most important questions concerning endothelial lipase are: a) does it play an important role in HDL metabolism in humans, and b) does it play a significant role in atherogenesis?" This proposal addresses both of these issues and also addresses key structure-function questions and potential gene-gene interactions with regard to EL and its effects on HDL metabolism. The results of these studies should provide important new insight into the role of EL in HDL metabolism and atherogenesis.

描述（由申请人提供）：高密度脂蛋白（HDL）胆固醇及其主要HDL载脂蛋白apoA-I的血浆水平与动脉粥样硬化性心血管疾病呈负相关。血浆 HDL 胆固醇和 apoA-I 水平部分取决于它们的分解代谢速率，但调节其体内分解代谢的机制仍不完全清楚。急性炎症状态（例如脓毒症）和慢性炎症状态（例如代谢综合征）都与 HDL 胆固醇和 apoA-I 水平低相关，这主要是由于分解代谢增加所致。该项目的一个主要基本假设是，细胞外磷脂酶因炎症反应而上调，并通过 HDL 磷脂的水解调节全身 HDL 代谢。我们克隆并表征了脂肪酶基因家族的一个新成员，我们将其称为内皮脂肪酶（EL）。在本项目的当前周期中，我们已经证明，小鼠中 EL 的过度表达会因分解代谢增加而导致 HDL 显着减少，而小鼠 EL 的抗体抑制会因分解代谢减少而导致 HDL 增加。在这项竞争性更新提案中，我们将重点关注 EL，以更好地了解其结构功能关系、与影响 HDL 的其他基因的代谢相互作用、与动脉粥样硬化的关联及其与人类生理学和病理生理学的关系。 具体目标 1：研究 EL 与其高度同源的近亲 LPL 和 HL 之间的差异，以及与 LPL 和 HL 相比，EL 的脂质和脂蛋白偏好的分子基础。 具体目标 2：检验以下假设：在肝脏中，EL 与 HL 和 SR-BI 相互作用，影响 HDL 代谢、选择性摄取胆固醇并逆转胆固醇转运。 具体目标 3：确定慢性肝脏特异性 EL 表达对小鼠动脉粥样硬化形成的影响。将这些结果与内皮特异性 EL 表达对动脉粥样硬化的影响进行比较。检验内皮 EL 表达影响内皮生理学的假设。 具体目标 4：检验以下假设：EL 在人类炎症状况下增加，并可能导致与这些状况相关的 HDL-C 水平降低。 最近的一篇社论指出：“也许有关内皮脂肪酶的最重要的问题是：a）它在人类 HDL 代谢中是否发挥重要作用，b）它在动脉粥样硬化形成中是否发挥重要作用？”该提案解决了这两个问题，还解决了有关 EL 及其对 HDL 代谢影响的关键结构功能问题和潜在的基因间相互作用。这些研究的结果应该为 EL 在 HDL 代谢和动脉粥样硬化形成中的作用提供重要的新见解。