HEPATIC AND LIPOPROTEIN LIPASE INDUCED REMNANT CLEARANCE

两种脂肪酶，脂蛋白脂肪酶（LPL）和肝甘油三酯脂肪酶 （HTGL），在乳糜微粒的催化中起核心作用， 低密度脂蛋白（VLDL）。 目前的提案将建立 我们实验室的体外研究结果表明：1）LPL 通过与LDL直接相互作用促进VLDL的清除 受体和LDL受体相关蛋白（LRP）和2）HTGL 通过LRP内化和降解。 这两种受体介导 乳糜微粒和VLDL残留清除率。 我们将测试 HTGL和LPL受体结合功能的重要性 乳糜微粒和极低密度脂蛋白的清除率，以及这些 脂肪酶在激活apoE结合LRP中起作用。目标1将测试 假设HTGL促进乳糜微粒的清除， VLDL通过LDL受体和LRP通过直接相互作用， 体外受体。 研究将在正常和突变细胞中进行 表达LRP和LDL受体或缺乏其中一种或两种受体的细胞系， 以及在固相分析中使用经肠胃外纯化的 LRP或LDL受体、酶活性和脂蛋白结合。 目的2验证HTGL和LPL激活apoE的假说 在体外结合LRP。 在没有脂肪酶的情况下，LRP不结合 VLDL或β-VLDL从胆固醇喂养的动物，尽管事实上 这两种脂蛋白通过apoE与LDL受体结合。 在目标3 通过LPL和HTGL的受体结合对 通过LRP和LDL受体清除乳糜微粒和VLDL 将使用腺病毒基因转移进行体内测试。 的影响 人LPL、HTGL或其变体的腺病毒表达 缺乏受体结合或酶活性的脂肪酶将 在apoE敲除（KO）小鼠中研究。 Apoe KO小鼠缺乏 将研究LDL受体或正常LRP功能， 评估这两种受体途径的相对贡献， 脂蛋白的清除。甘油三酯残留- 丰富的脂蛋白和低密度脂蛋白一样是致动脉粥样硬化的， 从VLDL 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脂蛋白在血浆中的积累。 研究 与腺病毒载体结合可能支持未来基因的可行性， 转移疗法治疗高脂血症。

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.