HEPATIC AND LIPOPROTEIN LIPASE INDUCED REMNANT CLEARANCE

脂蛋白脂肪酶(LPL)和肝甘油三酯脂肪酶两种脂肪酶 (HTGL)，在乳糜粒的分解代谢中起中心作用。 低密度脂蛋白(VLDL)。目前的提案将建立 根据我们实验室的体外研究结果，表明1)LPL 通过与低密度脂蛋白直接相互作用促进极低密度脂蛋白的清除 受体与低密度脂蛋白受体相关蛋白(LRP)和2)HTGL 通过LRP内化和降解。这两个受体介导 乳胶粒和极低密度脂蛋白体内残留清除。我们将测试 HTGL和LPL受体结合功能的重要性 乳糜米隆和极低密度脂蛋白在体内的清除以及它们的作用 脂肪酶在激活apoE与LRP结合中起作用。目标1将测试 假设HTGL促进乳糜粒的清除和 通过低密度脂蛋白受体和LRP直接与这些受体相互作用的极低密度脂蛋白 体外受体。研究将在正常细胞和突变细胞中进行 既表达LRP受体又表达低密度脂蛋白受体的品系，或者缺乏一个或 其他受体和在固相分析中使用部分纯化的 LRP或低密度脂蛋白受体、酶活性和脂蛋白结合。 目标2将检验HTGL和LPL~激活~apoE的假设 体外结合LRP。在没有脂肪酶的情况下，LRP不结合 来自胆固醇喂养动物的极低密度脂蛋白或β-极低密度脂蛋白 这两种脂蛋白都通过载脂蛋白E与低密度脂蛋白受体结合。在AIM 3中 LPL和HTGL受体结合在细胞周期中的作用 LRP和LDL受体对乳糜粒和极低密度脂蛋白的清除作用 将通过腺病毒基因转移在体内进行测试。的效果 人LPL、HTGL及其变异体的腺病毒表达 缺乏受体结合或酶活性的脂肪酶将是 在载脂蛋白E基因敲除(KO)小鼠中进行了研究。APOE KO小鼠缺乏 低密度脂蛋白受体或正常的LRP功能将被研究 评估这两个受体通路对 清除甘油三酯脂蛋白。甘油三酯的残留物- 富含的脂蛋白和衍生的低密度脂蛋白一样会导致动脉粥样硬化。 来自极低密度脂蛋白。拟议的研究将增加我们对 LPL和HTGL在防止 这些致动脉粥样硬化的脂蛋白在血浆中的积聚。研究 用腺病毒载体可能支持未来基因的可行性 调剂疗法在高脂血症治疗中的应用。

Two lipases, lipoprotein lipase (LPL) and hepatic triglyceride lipase (HTGL), play central roles in catabolism of chylomicrons and very low-density lipoproteins (VLDL). The current proposal will build on in vitro findings from our laboratory which indicate that 1) LPL promotes clearance of VLDL by direct interation with LDL receptors and the LDL receptor-related protein (LRP) and 2) HTGL is internalized and degraded via LRP. These two receptors mediate chylomicron and VLDL remnant clearance in vivo. We will test the importance of the receptor-binding functions of HTGL and LPL for chylomicron and VLDL clearance in vivo and the role that these lipases play in activating apoE to bind LRP. Aim 1 will test the hypothesis that HTGL promotes clearance of chylomicrons and VLDL via LDL receptors and LRP by direct interaction with these receptors in vitro. Studies will be done in normal and mutant cell lines that express both LRP and LDL receptors or lack one or the other receptor and in solid-phase assays using paretically purified LRP or LDL receptors, enzymatic activity, and lipoprotein binding. Aim 2 will test the hypothesis that HTGL and LPL ~activate~ apoE to bind LRP in vitro. In the absence of lipases, LRP does not bind VLDL or beta-VLDL from cholesterol-fed animals despite the fact that both lipoproteins bind to LDL receptors via apoE. In Aim 3 the contribution of receptor binding by LPL and HTGL to the clearance of chylomicrons and VLDL via LRP and LDL receptors will be tested in vivo using adenoviral gene transfer. Effects of adenoviral expression of human LPL, HTGL, or variants of these lipases that lack receptor binding or enzymatic activity will be studied in apoE knockout (KO) mice. Apoe KO mice that lack either LDL receptors or normal LRP function will be studied to assess the relative contributions of these two receptor pathways to clearance of triglyceriderich lipoproteins. Remnants of triglyceride- rich lipoproteins are atherogenic as are LDL, which are derived from VLDL. The proposed studies will increase our understanding of the roles that LPL and HTGL play in preventing the accumulation in plasma of these atherogenic lipoproteins. Studies with adenoviral vectors may support the feasibility of future gene transfer therapy in the treatment of hyperlipidemia.