The Regulation Of Lipid Metabolism Mediated By FGF21 In Hepatocytes

The access accumulation of triglyceride in hepatocytes may lead to a series of hepatic diseases, such as steatosis, fatty liver, heppatoma. FGF21 is a recently discovered cytokine playing an important role in lipid metabolism. In this study, HepG2 cell line was applied to conduct the research of FGF21 on lipid metabolism in atocytes in vitro. Firstly, the alteration of triglyceride content in hepatocytes after FGF21 overexpression was measured by oil O staining. Then the transcriptional expressions of genes involved in lipid metabolism in hepatocyte were assessed after over-expression FGF21. Further western blotting, immunocytochemistry and Real-time PCR were used to detect the expression, processing and entering into nucleus of SREBP-lc, a key transcriptional factor participated in lipogenesis. At last, we evaluated the regulation of SREBP-1c on FGF21 promoter using dual-luciferase reporter assay system. Our study manifested that FGF21 inhibited the transcriptional expression and processing of SREBPlc, and then reduced the mRNA of SREBPlc target genes, and at the end, reduced TG accumulation in HepG2 cells, In addition, using Meishan pig as a research object, we cloned the procine FGF21 and analysed the profiles of its expressions in various tissues for the first time. And then the FGF21 protein was expressed in E. coli BL21 (DE3) and was roughly purified. The detailed results are as follows:1. Genes participated in fatty acids de novo synthesis and esterification was down-regulated by FGF21. However, it has no significant effect on absorption of fatty acids and VLDL assembling. Oil O staining manifests that cellular triglyceride content was suppressed because of FGF21 over-expression. FGF21 protects hepatocytes from the up-regμlation of FAS and SREBP-1c causing by free fatty acids. FGF21 can inhibit the transcriptional expression, the processing and the entering into nucleus of SREBP-lc, and SREBP-1c in turn suppresses the promoter activity of FGF21, forming a feedback inhibition loop. FGF21 elicits the down-regulation of fatty acids oxidation. Glucose and ChREBP could escalate FGF21 mRNA level depending on dosage and time, and in verse fatty acids and SREBP-1c can suppress the transcription level of FGF21 in hepatocytes, also depending on dosage and time.2. FGF21 has little effect on hepatic glucose metabolism, only inhibiting gluconeogenesis in normal condition to some extent.3. The coding region of porcine FGF21 and partial non-coding sequence of porcine FGF21was amplified and then bioinformatic analysis was conducted. The coding region of porcine FGF21covers 627bp, encoding 208 amino acids. There are three exons and two introns in the genomic sequence of FGF21, and this is similar with human and mice’s FGF21 genomic structure. FGF21 expresses in various tissues of pig, and its expression is abundant in liver and adipose tissue. This implies the possible participation of FGF21 in metabolism.