Plasma Apolipoprotein Mutants and their Implication on Lipoprotein Metabolism

分析199例心绞痛或心肌梗死患者的血清脂蛋白和载脂蛋白E，以及211例健康人的血清载脂蛋白E。CCU组载脂蛋白E4频率高于对照组，E2频率低于对照组。载脂蛋白E突变体E7和E5在CCU组中也很常见。当我们通过载脂蛋白E表型检测血清脂蛋白时，具有E3/2表型的受试者血清中LDL浓度降低，极低密度脂蛋白（VLDL）浓度升高，而具有e3 /3表型的受试者血清中LDL水平升高。结果表明，E4和E2同工蛋白分别是动脉粥样硬化的阳性和阴性危险因素。动脉粥样硬化的机制之一与载脂蛋白E同工蛋白对血清LDL水平的作用有关。我们之前已经证明了载脂蛋白E的独特同工蛋白（载脂蛋白E5和E7）与血脂症和动脉粥样硬化相关。对E5的基因分析表明，在成熟蛋白的第三位上，G向a的替换导致了更多的Glu向Lys的替换。f7有两个G到A的取代，导致在244和245位上- glu - glu -到- lys - lys -的取代。我们表征了载脂蛋白E5和载脂蛋白E7在人成纤维细胞上与LDL受体结合的活性。载脂蛋白E5的亲和力是野生型载脂蛋白E3的2倍。然而，Apo E7的受体亲和力低于Apo E3。apo E5的高亲和力可能导致肝脏对含apo E5的脂蛋白的高摄取，并导致肝脏中LDL受体的下调。我们可以假设携带载脂蛋白E5的受试者易患高胆固醇血症，从而导致动脉粥样硬化。我们开发了一种快速、准确、灵敏的测定载脂蛋白E分子种类的方法，并利用该方法研究了儿童载脂蛋白E同工蛋白与血清脂蛋白代谢的关系。测定了767名7、10和13岁学龄儿童的载脂蛋白E表型和血清脂蛋白水平。载脂蛋白E表型通过免疫印迹等电聚焦凝胶进行。脱脂前用神经氨酸酶处理血清样本。各年龄组血清胆固醇和低密度脂蛋白胆固醇浓度依次为E3/2 -> 1/2 E3/3 -> E4/3。载脂蛋白E多态性对血清载脂蛋白B的影响趋势与胆固醇水平相同，而对血清载脂蛋白E浓度的影响则相反。值得注意的是，载脂蛋白E同型体对血清脂蛋白的影响甚至在儿童时期就已被发现。我们认为，基于早期载脂蛋白E表型的饮食控制可能会预防高脂蛋白血症和动脉粥样硬化。少

Serum lipoproteins and apo E were analyzed from 199 patients in CCU, having angina pectoris or myocardial infarction, and from 211 healthy subjects. The frequency of apo E4 was higher and that of E2 was lower in the CCU group than in the control group. Apo E mutants, E7 and E5, were also frequent in the CCU group. When we examined serum lipoproteins by the apo E phenotypes, the subjects with an E3/2 phenotype had reduced LDL and increased very low density lipoprotein (VLDL) concentrations, and those with an E4/3 phenotype had increased LDL levels in serum. The results suggested that the E4 and E2 isoproteins were positive and negative risk factors for atherosclerosis, respectively. One of the mechanisms of atherosclerosis is associated with the action of apo E isoproteins on serum LDL levels.We have previously demonstrated unique isoproteins of apo E (apo E5 and E7) associated with liyperlipidemia and atlierosclerosis. Gene analysis of E5 showed that a G to A substitution had resulted … More in a Glu to Lys substitution at the third position of the mature protein. F, 7 had two G to A substitutions, resulting in -Glu-Glu- to -Lys-Lys- substitution at positions 244 and 245. We characterized the activity of apo E5 and apo E7 binding to LDL receptors on human fibroblasts. The affinity of apo E5 was twice that of wild form of apo E3. Apo E7, however, had a lower receptor affinity than apo E3. The high affinity, of apo E5 may result in a high uptake of apo E5-containing lipoproteins by the liver and lead to a down-regulation of LDL receptors in the liver. We can postulate that the subjects with apo E5 are susceptible to hypercholesterolemia and in consequence to atherosclerosis.We developed a rapid, accurate, and sensitive method for determining apo E molecular species, and to utilize this method we investigated the relationship between apo E isoproteins and serum lipoprotein metabolism in children. Apo E phenotypes and serum lipoprotein levels were determined in 767 school children aged 7, 10 and 13 years old. Apo E phenotyping was performed by immunoblotting of an isoelectric focusing gel. Serum samples were treated with neuraminidase before delipidation. Serum cholesterol and LDL-cholesterol concentrations increase'd in the order of E3/2 -> 1/2 E3/3 -> E4/3 in each agegroup. The effect of the apo E polymorphism in serum apo B was the same tendency as cholesterol levels, but the opposite effect on serum apo E concentrations was observed. It was noteworthy that the effect of apo E isoforms on serum lipoproteins had been revealed even in childhood. We suggest the possibility that hyperlipoproteinemia and atherosclerosis miglit be prevent by dietary control based on apo E phenotypes early in life. Less