脂肪变性对肝细胞胆固醇代谢的影响

Cholesterol metabolism in cultured steatotic hepatocytes

目的:探讨非酒精性脂肪性肝病中肝细胞胆固醇(TC)代谢的相关变化.方法:正常成人肝细胞株HL-02,以油酸软脂酸诱导肝细胞产生脂肪变性,建立肝细胞脂肪变性模型.分别于实验12、24、48h收集细胞,同期设不含脂肪酸培养的细胞作对照.油红O染色观察细胞内脂滴变化;试剂盒检测细胞内三酯酰甘油(TG)和TC含量的变化情况,RT-PCR分别检测表达固醇调节元件结合蛋白2(SREBP-2),其靶基因羟甲基戊二酸单酰辅酶A还原酶(HMGCR)、低密度脂蛋白受体(LDLR)及TC7α羟化酶(CYP7α1)的基因mRNA变化.结果:油酸软脂酸诱导12h即可产生肝细胞脂肪变性,24h及48h脂肪变性逐渐加重.随造模时间延长,模型组细胞内TG、TC含量逐渐增多,且均显著高于对照组(TG:16.93±1.57mg/g,23.67±2.4mg/g,51.1±11.76mg/gvs8.43±5.65mg/g;TC:14.9±0.6,23.7±1.1mg/g,38.4±4.5mg/gvs8.5±1.6mg/g;均P<0.01);SREBP-2,HMGCRmRNA表达逐渐升高(SREBP-2mRNA:1.2972±0.16,1.6141±0.21,2.0368±0.27vs1.0±0.11;HMGCRmRNA:1.0311±0.15,1.2706±0.28,1.3954±0.32vs1.0±0.12;均P<0.05),而LDLR、CYP7α1mRNA表达逐渐下降(LDLRmRNA:0.8901±0.22,0.7846±0.18,0.6912±0.09vs1.0±0.24;CYP7α1mRNA:0.9726±0.27,0.6707±0.18,0.5659±0.16vs1.0±0.19;均P<0.05).结论:肝细胞脂变后细胞内TC含量增加,其合成基因表达升高及代谢基因表达降低可能是其机制;LDLRmRNA表达降低.

AIM： To investigate the changes of cholesterol metabolism in nonalcoholic fatty liver disease. METHODS： Steatosis model of hepatocytes was established by adding palmic acid and oleic acid to HL-02 cells. Cells were collected at 12, 24 and 48 h. HL-02 cells without adding palmic acid served as controls. Oil red O staining was used to observe the intracellular changes of lipid drops. The intracellular triglyceride （TG） and total cholesterol were detected using analysis kit. The expression changes of sterol regulatory element-binding protein 2 （SREBP-2）, hydroxy- methylglutaryl-CoA reductase （HMGCR）, low density lipoprotein receptor （LDLR） and cholesterol 7alpha-hydroxylase （CYP7A1） were measured by reverse transcription-polymerase chain reaction （RT-PCR）. RESULTS： Hepatocyte steatosis was observedat 12 h, and became more serious at 24 and 48 h. The contents of intracellular TG and TC in- creased, significantly higher than those in con- trois （TG： 16.93 ＋ 1.57 mg/g, 23.67 ＋ 2.4 mg/g, 51.1 ＋ 11.76 mg/g vs 8.43 ＋ 5.65 mg/g; TC： 14.9 ＋ 0.6 mg/g, 23.7 ＋ 1.1 mg/g, 38.4 ＋ 4.5 mg/g vs 8.5 ＋ 1.6 mg/g, all P 〈 0.01）. The expression lev- els of SREBP-2 and HMGCR were up-regulated （SREBP-2 mRNA： 1.2972 ＋ 0.16, 1.6141 ＋ 0.21, 2.0368 ＋ 0.27 vs 1.0 ＋ 0.11; HMGCR mRNA： 1.0311 ＋ 0.15, 1.2706 ＋ 0.28, 1.3954 ＋ 0.32 vs 1.0 ＋ 0.12; all P 〈 0.05） while those of LDLR and CYP7A1 （LDLR n^d~qA： 0.8901 ＋ 0.22, 0.7846 ＋ 0.18, 0.6912 ＋ 0.09 vs 1.0 ＋ 0.24; CYP7al mRNA： 0.9726 ＋ 0.27, 0.6707 ＋ 0.18, 0.5659 ＋ 0.16 vs 1.0 ＋ 0.19; all P 〈 0.05） were down-regulated in a time-dependent manner in model group. CONCLUSION： Cholesterol contents increase in steatotic hepatocytes, which may be caused by elevated gene expression of SREBP-2 and HMGCR as well as reduced expression of LDLR and CYP7A1.