Effects Of Farnesoid X Receptor On Lipid Metabolism In L02 Cell Line And Its Mechanisms

BackgroundNonalcoholic fatty liver disease (NAFLD) is a relevant challenge for gastroenterology and liver units. The disease currently is recognized as the most common form of chronic liver disease in many parts of the world. Nonalcoholic steatohepatitis (NASH) can progress to cirrhosis, leading to liver failure and hepatocellular carcinoma (HCC). Farnesoid X receptor (FXR) and small heterodimer partner (SHP) are members of nuclear receptor. FXR is an important factor in controlling bile acid homeostasis, lipid and glucose metabolism, and considered to be a possible target to treat fatty liver disease and metabolic diseases. SHP has emerged as a key gene involved in the regulation of hepatic lipid metabolism and its potential role in the pathogenesis of NAFLD. Primary bile acid is a natural agonist of FXR. The activation of FXR leads to repression of sterol regulatory element-binding protein-1c (SREBP-1c), a transcription factor that controls genes involved in fatty acid and triglyceride synthesis. SHP is considered to be a target gene of FXR, and SREBP-1c is a genetic target of SHP. In the present study, we examined the effects of FXR on lipid metabolism in human hepatocyte line L02 and its mechanisms.Methods1. Experiment groups: control (group C); steatosis models (induced by sodium oleate, group F); intervention models (induced by sodium oleate and sodium chenodeoxycholate【1】, group F1).2. The optimized concentration and treatment time was selected by MTT assay. Steatosis models and intervention models were induced by adding sodium oleate or sodium oleate and sodium chenodeoxycholate to human hepatocyte line L02.3. The accumulation of lipid droplets in the hepatocytes was observed by optical microscopy after with oil red O staining.4. The levels of TG, AST and ALT were measured by biochemical assays.5. The Expression of FXR, SHP, and SREBP-1c receptors was detected by RT-PCR and Western blot.Results1. Steatosis models in L02 cell were established successfully. Accompanied with extension of time, steatosis hepatocyte was more aggravated.1) Only small lipid droplets were observed in control group. There were much more visible orange lipids accumulations both in steatosis models and intervention models. Integration with lipid drops could be observed along with the prolonging of the culture time in oleic acid groups. While compared with steatosis models, content of lipid droplets decrease significantly in intervention models.2) Both in steatosis models and intervention models, content of TG is much higher than control group (P <0.01). Compared with intervention models, level of TG was markedly increased in steatosis models at 24, 48, 72 hours (P <0.01).2. Level of ALT and AST in cultural medium in each group. Only in steatosis models at 72 hours, level of AST and ALT were increased slightly (P> 0.05).3. Expression of FXR, SHP, SREBP-1c mRNA and protein in each group.Compared with control group, expression of FXR mRNA and protein was downregulated in steatosis models. Expression of SHP and SREBP-1c mRNA and protein was increased gradually (P<0.01). In intervention models, expression of FXR mRNA and protein was increased markedly and accompanied with increased expression of SHP mRNA and protein compared with steatosis models (P<0.01). And expression of SREBP-1 c mRNA and protein was significantly reduced (P<0.01).Conclusions 1. Expression of FXR is closely associated with the lipid homeostasis in hepatocyte.2. Up-regulation expression of FXR may improve lipidosis in L02 cell. Its possible mechanism involves activation of SHP, and thereby, reduction of SREBP-1c expression and lipogenesis in hepatocyte.3. SHP maybe a double-edged sword of regulation on lipid metabolism in hepatocyte.4. FXR maybe a novel therapeutic target in fatty liver disease. As an agonist of FXR, sodium deoxycholate can improve hepatocyte steatosis significantly.