The effects of fibroblast growth factor-21 knockdown and over-expression on its signaling pathway and glucose-lipid metabolism in vitro.

OBJECTIVE: The aim of this study was to examine the effects of FGF-21 over- and underexpression on glucose and lipid metabolism in hepatocytes and adipocytes.
METHODS: FGF-21 over-expressive vectors (pcDNA-FGF-21) and FGF-21 shRNA-expressing vectors (pGenesil-FGF-21) were transfected into Hepa1-6 hepatocyte and 3T3-L1 adipocyte. The levels of FGF-21 in the incubation medium were measured by ELISA. FGF-21 protein levels by Western blot analysis, and glucose uptake rates (GUR) by measuring 2-deoxy-d-glucose uptake. The mRNA expression of transcription factors were determined by real-time quantitative PCR.
RESULTS: Transfection of pcDNA-FGF-21 significantly increased FGF-21 expression in both Hepa1-6 hepatocytes and 3T3-L1 adipocytes (4.8- and 4.2-fold, respectively p<0.05), while transfection of pGenesil-FGF-21 significantly decreased FGF-21 expressions by 86% and 78%, respectively (p<0.05). In 3T3-L1 adipocytes, the up-regulation of FGF-21markedly increased GUR, decreased intracellular triglyceride (TG) content, up-regulated β-klotho, FGFR1, GLUT-1, IRS-1, ATGL, HSL, and ap2 mRNA expressions (p<0.05). Opposite changes occurred in FGF-21 knockdown adipocytes, except for IRS-1. In hepatocyte, FGF-21 up-regulation reduced HMGR and PEPCK mRNA expression and increased β-klotho, FGFR4 and LDLr expression (p<0.05), whereas down-regulation had the opposite effects.
CONCLUSION: These data suggest that both FGF-21 knockdown and over-expression led to changes in lipid levels, GUR and transcription factors involved in glucose and lipid metabolism, but that the mechanisms of FGF-21 actions in adipocytes and hepatocytes might be different.