Expression of the human apolipoprotein A-I: polymorphisms and drug effects

在载脂蛋白基因分析过程中，我们发现日本高脂血症患者存在载脂蛋白A5基因多态性，c.553G>T。这种多态性导致半胱氨酸对甘氨酸的氨基酸取代的变化。用限制性片段长度多态性方法测定了95例日本高脂血症患者和119例无关的正常血脂受试者的-1131 T>C和c.553 G>T多态性频率。高脂血症组-1131bp的T等位基因频率（0.511）和c.553G>T的t等位基因频率（0.205）分别显著高于血脂正常组（0.315和0.105）（p<0.01和p<0.02）。这两个多态性位点之间存在很强的连锁不平衡。这些结果表明，-1131 T>C和c.553 G>T多态性与日本人群的高血脂症有关。他汀类药物治疗降低了LDL胆固醇和甘油三酯的水平，并增加了抗动脉粥样硬化的HDL的水平。我们研究了它们调节APOA 5基因表达并因此影响血浆甘油三酯水平的能力。通过测量转染入人肝癌HepG 2细胞的具有APOA 5启动子区的质粒的荧光素酶活性来估计APOA 5基因的启动子活性。用匹伐他汀处理显著增加人HepG 2细胞中的APOA 5表达和mRNA水平，并且共转染PPARa处理导致APOA 5表达的显著增加。这些作用被逆转的甲羟戊酸或香叶基香叶基焦磷酸，暗示HMG-CoA还原酶作为这些药物的相关目标。

In course of apolipoprotein genes analysis, we found a polymorphism of APOA5 gene, c.553G>T in Japanese patients with hypertriglyceridemia. This polymorphism causes the change of amino acid substitution of a cysteine for a glycine. The frequencies of -1131T>C and c.553G>T polymoiphisms in 95 Japanese patients with hypertriglyceridemia and 119 unrelated normolipidemic subjects were determined by restriction-fragment-length-polymorphisms. The frequencies of the T allele at -1131bp (0.511) and the t allele at c.553G>T (0.205) in patients with hypertriglyceridemia were significantly higher than those in normolipidemic subjects (0.315 and 0.105), respectively (p<0.01and p<0.02). The two polymorphic sites were in strong linkage disequilibrium. These results suggest that the polymorphisms, -1131T>C and c.553G>T were associated with hypertriglyceridemia in Japanese population. Statin treatment reduces the levels of LDL cholesterol and triglyceride, and increases the levels of the antiatherogenic HDL. We investigated their ability to modulate APOA5 gene expression and consequently influence plasma triglyceride levels. Promoter activity of the APOA5 gene was estimated by measuring luciferase activity of plasmids with a APOA5 promoter region transfected into human hepatoma HepG2 cells. Treatment with pitavastatin significantly increased APOA5 expression and mRNA levels in human HepG2 cells, and cotransfection of a PPARa treatment resulted in a significant increase of APOA5 expression. These effects were reversed by the addition of mevalonate or geranylgeranyl pyrophosphate, implicating HMG-CoA reductase as the relevant target of these drugs.