Cell-biological and molecular biological analyzes of reverse cholesterol transport as a protective system against atherosclerosis

胆固醇酯转运蛋白(CETP)缺乏症患者脂蛋白功能异常的分析CETP缺乏症患者的脂蛋白异常表现为大而富含胆固醇酯(CE)的高密度脂蛋白和小的多分散的高密度脂蛋白。CETP缺乏纯合子受试者获得的高密度脂蛋白大而富含CE的高密度脂蛋白对降低高脂巨噬细胞胆固醇含量的效果不如对照组。患者的小而分散的低密度脂蛋白与正常人成纤维细胞的低密度脂蛋白受体亲和力降低。CETP缺陷的分子基础我们发现在日本普通人群中CETP基因内含子14的5‘剪接供体片段G-to-A突变的频率约为1%。我们还在显著高脂蛋白血症患者中发现了一种新的外显子15(D442；G)错义突变。这种新的突变是…CETP缺乏症的致病性高脂蛋白血症合并冠心病和青少年角膜混浊(动脉粥样硬化53；207-212,1984)被证实为外显子15错义突变的纯合子。我们还发现，CETP缺陷、HTGL低的患者可能对CHD易感。我们发现了一个独特的区域，由内含子14剪接缺陷引起的显著高脂蛋白血症(HLP)明显聚集。在该区域，高龄存活的受试者中明显的HALP和内含子14 CETP基因突变的发生率低于年轻受试者。这些结果提示CETP缺乏可能不是一种长寿综合征。IV.原发性胆汁性肝硬变(PBC)的脂蛋白异常通常与HALP和黄色瘤有关。我们发现，与CETP缺乏相比，高脂蛋白血症PBC患者血浆CETP水平显著升高，HTGL活性降低。V.高密度脂蛋白与肝细胞的相互作用，肝细胞是胆固醇逆转转运的终端。我们发现，与肝外外周细胞相比，高密度脂蛋白被人肝癌细胞系Mahavu摄取和降解，而肝外周细胞不发生高密度脂蛋白的降解。结果表明，高密度脂蛋白相关的胆固醇可能通过一种不同于低密度脂蛋白代谢的途径被处理。较少

I.Analysis of abnormal function of lipoproteins in cholesteryl ester transfer protein (CETP) deficiencyLipoprotein abnormalities in CETP deficiency were characterized by the presence of large and cholesteryl-ester(CE)-rich HDL and small polydisperse LDL.Large and CE-rich HDL_2 obtained from homozygous CETP-deficient subjects was less effective for reducing cholesterol content in lipid-laden macrophages than that from control subjects. The small polydisperse LDL of patients had reduced affinity for the LDL receptor of normal human fibroblasts. These abnormal in vitro function of plasma lipoproteins from CETP deficiency may be associated with athrosclerosis.II.Molecular basis of CETP deficiencyWe found that the frequency of the G-to-A mutation at the 5' splice donor slite of intron 14 in the CETP gene was approximately 1% in the Japanese general population. We also found a novel missense mutation in exon 15(D442 ; G) in markedly hyperalphalipoproteinemic patients. This novel mutation was … More revealed to be as common as the intron 14 splicing defect in Japan.III.Atherogenicity in CETP deficiencyThe hyperalphalipoproteinemic subjects with coronary heart disease (CHD) and juvenile corneal opacification (Atherosclerosis 53 ; 207-212, 1984), were identified to be homozygous for the exon 15 missense mutation. We also found that CETP-deficient patients with low HTGL may be susceptible to CHD.We found a unique area where a marked hyperalphalipoproteinemia (HALP) caused by the intron 14 splicing defect was markedly accumulated. In this area, a marked HALP and the intron 14 CETP gene mutation were less frequentry observed in the eiderly survived subjects than in the younger subjects. These results suggested that CETP deficiency may not be a longevity syndrome.IV.Lipoprotein abnormalities in primary biliary cirrhosis (PBC)PBC was known to be often associated with HALP and xanthomas.We found that plasma levels of CETP were markedly increased and HTGL activities were reduced in hyperalphalipoproteinemic patients with PBC, in contrast to CETP deficincy.V.Interaction between HDL and hepatocytes, a terminal of reverce cholesterol transportWe found that HDL is taken up and degraded by a human hepatoma cell line, Mahlavu, in contrast to extrahepatic peripheral cells, in which the degradation of HDL does not occur. The results indicated that HDL-associated cholesterol may be processed via a pathway different from that of LDL metabolism. Less