LOW DENSITY LIPOPROTEIN (LDL) METABOLISM IN PRIMATE ATHEROSCLEROSIS

在上一个供资期间， 脂肪不能防止冠状动脉粥样硬化， 改善LDL/HDL比率。由于这对公众健康的重要性， 观察，我们建议确认和扩大这一观察与 进一步的研究，同时试图确定机制， 结果发生。一群非洲绿色猴子将被喂食四种不同的食物， 膳食脂肪（饱和、单不饱和、n-6和n-3 多不饱和的）以改变LDL颗粒组成。血浆LDL 胆固醇浓度将在膳食脂肪组之间平衡， LDL组分对冠状动脉扩张的影响 可以直接评估动脉粥样硬化。的等离子体的光谱 将在实验中的每只动物中测量脂蛋白应答。 冠状动脉粥样硬化的发展程度 还将测量四年的饮食诱导期， 任何脂蛋白与动脉粥样硬化的关系，以及膳食脂肪酸 影响，可以确定。要检验的主要假设是 该建议是，组成改变的胆固醇油酸酯 富含低密度脂蛋白促进动脉粥样硬化 他们的数量比例通过一种倾向，以促进胆固醇 在冠状动脉中积聚。来研究在构图上 修饰的LDL可促进动脉粥样硬化的形成，各饮食组的LDL 检查其与动脉蛋白聚糖（PG）的结合以及对 动脉平滑肌细胞产生PG。膳食n-3的替代 多不饱和脂肪酸的饮食结果减少胆固醇 肝脏的油酸积累和分泌，以及增加 胆固醇7 α-羟化酶（C7 H）活性和游离胆固醇降低 肝的内容。两种肝脏胆固醇代谢酶，酰基- CoA：胆固醇酰基转移酶（ACAT）和C7 H似乎是关键 用于确定整个肝脏胆固醇平衡的监管位点。 肝脏ACAT（s）和C7 H调节的研究将在 从喂食不同饮食的猴子身上连续取下的肝脏活组织检查， 在与不同脂肪酸类型孵育的分离猴肝细胞中， 胆固醇浓度，并在隔离肝脏灌注期间， 从来自每个不同饮食组的动物分离的肝脏。 越来越多的证据表明，肝脏中存在多种ACAT酶， 我们将识别和表征肝脏ACAT，以确保 相关酶的调节是文档。最后，我们建议 研究一只低密度脂蛋白胆固醇水平非常高的转基因小鼠， 其中测试膳食脂肪酸对LDL组成的影响， 动脉粥样硬化，因为ACAT和/或C7 H的遗传修饰， 最终可以在小鼠中进行测试。

This observation was made in the last funding period that mono-unsaturated fat did not protect against coronary artery atherosclerosis in spite of an improved LDL/HDL ration. Due to the public health significance of this observation, we propose to confirm and extend this observation with further studies, while attempting to define mechanisms through which the outcome occurs. Groups of African green monkeys will be fed four different dietary fats (saturated, mono-unsaturated, and n-6 and n-3 polyunsaturated) to modify LDL particle composition. Plasma LDL cholesterol concentrations will be balanced among dietary fat groups so that the effect of LDL composition on the extend of coronary artery atherosclerosis can be assessed directly. The spectrum of plasma lipoprotein responses will be measured in each of the animals in the study, and the extend of coronary artery atherosclerosis that develops over a four year period of diet-induction will also be measured so that any lipoprotein-atherosclerosis relationship, and dietary fatty acid effect thereon, can be identified. The main hypothesis to be tested in this proposal is that compositionally modified, cholesteryl oleate enriched low density lipoproteins promote atherosclerosis out of proportion of their number through a predisposition to promote cholesterol accumulation in the coronary arteries. To examine how compositionally modified LDL could promote atherogenesis, LDL from each diet group will be examined for their binding to arterial proteoglycans (PG) and effects on PG production by arterial smooth muscle cells. Substitution of dietary n-3 polyunsaturated fatty acids into the diet results in less cholesteryl oleate accumulation and secretion by liver, as well as an increased cholesterol 7alpha-hydroxylase (C7H) activity and reduced free cholesterol content of liver. The two liver cholesterol -metabolizing enzymes, acyl- CoA: cholesterol acyltransferase (ACAT) and C7H appear to be key regulatory sites for determining cholesterol balance across the liver. Study of the regulation of hepatic ACAT(s) and C7H will be carried out in sequential liver biopsies taken from monkeys fed different diets, and that in isolated monkey hepatocytes incubated with varying fatty acid types and cholesterol concentrations, and during isolated liver perfusion with livers isolated from animals from each of the different diet groups. Evidence is accumulating that there are multiple ACAT enzymes in liver, and we will identify and characterize the hepatic ACAT(s) to be sure that regulation of the pertinent enzyme is document. Finally, we propose to examine a transgenic mouse with very high LDL cholesterol levels a model in which to test the dietary fatty acid effects on LDL composition and atherosclerosis, since genetic modifications in ACAT and/or C7H, for example can eventually be tested in mice.