法尼醇X受体对L02细胞脂肪代谢的调节作用

Effects of farnesoid X receptor on lipid metabolism in L02 cells

目的观察法尼醇X受体（FXR）对人肝细胞株L02细胞脂肪代谢的调节作用。方法油酸钠建立L02细胞脂肪变模型（脂肪变组），油酸钠及鹅去氧胆酸钠建立干预模型（干预组），设对照组（培养基中不加药物），3组均设立24、48、72h时间点。油红O染色，细胞内甘油三酯含量测定，检测肝细胞脂肪变程度；Westernblot和RT—PCR方法检测核受体FXR及固醇调节元件结合蛋白1c（SREBP-c）的表达变化。结果脂肪变组随着肝细胞脂肪变性的发生发展，FXR表达呈逐渐降低趋势，但差异无统计学意义。SREBP—1c mRNA的表达明显升高，24、48、72h图像半定量分析结果分别为0．495±0．062、0．579±0．064、0．612±0．067，SREBP1c蛋白表达分别为0．394±0．044、0．488±0．066、0．543±0．064，均明显高于干预组和对照组，差异有统计学意义。干预组FXRmRNA表达明显上调，24、48、72h分别为0．253±0．041、0．298±0．042、0．334±0．051，FXR蛋白分别为0．221±0．022、0．313±0．041、0．341±0．046，与脂肪变组比较，F值为6．41～50．93，P值均〈0．05或0．01，差异有统计学意义。脂变组甘油三酯含量各时间段均明显增加，干预组甘油三酯含量各时间段均明显降低，差异有统计学意义。结论FXR表达下调与肝细胞脂肪沉积密切相关；刺激FXR表达增加可能通过抑制其靶基因SREBP—1c表达而改善L02细胞脂肪变性。

Objective To investigate the effects offarnesoid X receptor （FXR） on lipid metabolism in human hepatic L02 cells. Methods A steatosis model and an intervention model were established by treating human hepatocyte line L02 cells with sodium oleate or sodium oleate and sodium chenodeoxycholate （a natural agonist of FXR） respectively. Non-treated L02 cells served as controls. At three time points of 24, 48 and 72 hours, the accumulation of lipid droplets in the hepatocytes was observed by optical microscopy after oil red O staining, and the the expression of FXR and SREBP-1c receptors was detected by RT-PCR and Western blot. Results Compared with the controls, expressions of FXR mRNA and protein were down- regulated gradually in the steatosis model at 24, 48 and 72 hours, FXR mRNA/beta-actin mRNA was 0.186 ± 0.02, 0.182±0.028 and0.181 ± 0.022, FXRprotein/beta-tubulin protein was 0.105 ± 0.016, 0.103± 0.012 and 0.103± 0.018, F from 0.01 to 0.14; 24 h vs 48 h, 48 vs72 h： P 〉 0.05. The expressions of SREBP-1 c mRNA and protein were increased gradually. At 24, 48 and 72 hours, SREBP-lc mRNA/beta-actin mRNA was 0.495± 0.062, 0.579 ±0.064 and 0.612 ± 0.067, SREBP-1c protein/beta-tubulin protein was 0.394 ±0.044, 0.488 ±0.066 and 0.543 ± 0.064, F from 0.80 to 4.66, 24 h vs 48 h,48 vs72 h： P 〈 0.05. In the intervention model, expressions of FXR mRNA and protein were increased markedly compared with the steatosis model. At 24, 48 and 72 hours, FXR mRNA/beta-actin mRNA was 0.253± 0.041, 0.298 ±0.042 and 0.334 ± 0.051, and FXR protein/beta-tubulin protein was 0.221±0.022, 0.313 ±0.041 and 0.341 ± 0.046, F from 6.41 to 50.93, intervention models vs steatosis models at the same time points： P 〈 0.05-0.01. Expressions of SREBP- 1 c mRNA and protein were significantly reduced. At 24, 48 and 72 hours, SREBP- 1c mRNA/beta-actin mRNA Was 0.296±0.038, 0.328 ± 0.037 and 0.341±0.055, and FXR protein/beta- tubulin protein was 0.295± 0.038, 0.334 ± 0.047 and 0.355 ± 0.054, F from 8.84 to 48.46; intervention models vs steatosis models at the same time point： P 〈 0.01. Both in the steatosis model and the intervention model, content of TG and lipids accumulations were much more than those in the controls. Compared with the intervention model, levels of TG and lipids accumulation were markedly increased in the steatosis model at 24, 48, 72 hours. At 24, 48 and 72 hours, TG/cellular total protein in μg/mg was 173.0 ± 20.5, 253.4 ±36.1 and 361.2± 50.7 in the steatosis model, while in the intervention model the data was 84.1 ± 17.2, 113.0 ± 14.5 and 127.2 ±20.1, F from 38.70 to 268.13, intervention models vs steatosis models at the same time point： P 〈 0.01. Conclusion Expression of FXR is closely associated with lipid homeostasis in hepatocytes. Up-regulation of the expression of FXR may improve lipidosis in L02 cells. Its possible mechanism involves reduction of SREBP-1c expression and lipogenesis in hepatocytes.