The Regulation Of FGF21 To Autophagy In HepG2 Cells

Fibroblast growth factor 21(fibroblast growth factor 21,FGF21),a member of FGF family,can resist obesity,enhance insulin sensitivity and improve various metabolic diseases.Previous studies in hepatocyte revealed that FGF21 plays important roles in regulating lipid accumulation,lipid-induced ER stress,mitochondrial dysfunction and metabolism-related inflammation.Simultaneously we found that FGF21 transcription is regulated by transcription factors NF?B,CEBPs and PPAR?,while microRNA26 can control FGF21 translation.Autophagy is a self-protection mechanism which is extensively studied in lipid metabolism and lipid-related diseases,and currently lipophagy is thought as a new branch of autophagy.Therefore,in this study,we hypothesized that there exists some relationship between FGF21 and autophagy.Thus,based on confirming this relationship,we explored the potential molecular mechanism that FGF21 influenced autophage in HepG2 cells.In the present studies,to detect the mechanism of FGF21-regulating autophagy,we overexpressed or knocked down FGF21 in HepG2 cells,or treated cells with AKT inhibitor LY294002 or AMPK activator AICAR or FGF21 recombinant protein,then detected the mRNA and protein levels of the biomarker genes and observed the change of autophagy morphology though real-time PCR,Western Blot and MDC dyeing etc.methods The acquired detail results are as follows:1.PA significantly up-regulated the mRNA and protein levels of autophagy key genes and changed the morphology of autophagosome,and simultaneously remarkably enhanced the level of FGF21 mRNA.2.Overexpressed FGF21 can significantly enhanced the mRNA and protein levels of autophagy key genes,and the stronger autophagy was observed by MDC dyeing in FGF21-overexpressed HepG2 cells compared to control.3.By contrast,FGF21 knockdown conspicuously reduced the mRNA and protein levels of autophagy key genes,and the cell autophagy also became weaker by MDC dyeing compared to control.4.In HepG2 cells treated with AMPK activator AICARor PI3K/AKT phosphorylation inhibitor LY294002 or FGF21 recombinant protein,we found that the mRNA and protein levels of autophagy key genes and morphological level were increased in all the treated groups accompanied by the remarkable decreases of FGF21 and total AKT protein levels.5.By contrast,In HepG2 cells with AICAR,LY294002 or FGF21 recombinant protein treatment,FGF21 knockdown returned the effect of LY294002 and FGF21 recombinant protein but not AICAR in autophagy morphological level.Therefore,we deduced that FGF21 regulates autophagy through PI3K/AKT pathway.6.Our previous study found NFkB/p65 can directly bind to FGF21 promoter DNA and regulate FGF21 transcription.Here,p65 overexpression significant enhanced the protein levels of autophagy key genes and the level of total AKT protein.Therefore,autophagy possibly is regulated via p65-FGF21-PI3K/AKT pathway in HepG2 cells.In summary,the conclusions of this study are:PA can up-regulate autophagy and autophagy possibly is regulated via p65-FGF21-PI3K/AKT pathway in HepG2 cells.