FGF21 Presents Its Anti-atherosclerotic Effect By Regulating The Synthesis Of Cholesterol And Adiponectin Production

Fibroblast growth factor 21(FGF21),a metabolic hormone with pleiotropic effects on glucose and lipid metabolism,energy balance and insulin sensitivity,plays an important role in the pathogenesis of metabolic syndrome.FGF21 acts as a key downstream target of both peroxisome proliferator-activated receptor?and?,which have been used for lipid lowering and insulin sensitization,respectively.Atherosclerosis,as a chronic inflammatory disease closely related to abnormal lipid metabolism,involves multiple cell types at various stages of plaque formation such as endothelial cells,lymphocytes,monocytes/macrophages and smooth muscle cells.However,the role of FGF21 in the progression of atherosclerosis remained unknown.Therefore,this study was aimed to further investigate the role and mechanism of FGF21 in the pathogenesis of atherosclerosis.In this study,loss-of-function(deletion of FGF21 gene in Apo E^-/-mice)and gain-of-function(replenishment with recombination FGF21 protein)techniques were used to investigate the role of FGF21 in atherosclerosis.On one hand,we constructed FGF21gene and apolipoprotein E gene double knockout mice(DKO mice).The FGF21 and adiponectin concentration,lipid profile and inflammatory factors in blood and liver were detected by biochemical methods,insulin and glucose tolerance were analyzed respectively.Meanwhile,infiltration of macrophages and accumulation of fat in blood vessels detected by immunohistochemical technique and oil-red staining respectively were used to explore the effect of FGF21 deletion on pathogenesis of atherosclerosis in apoE knockout(apoE^-/-)mice.On the other hand,replenishment with recombinant FGF21 in DKO mice was used to determine the effect of FGF21 on inflammatory cell infiltration,circulating lipid profile and smooth muscle cell proliferation and migration.In this paper,the fecal and liver tissues of DKO mice supplemented with FGF21 and adiponectin respectively were collected to detect the content of cholesterol and bile acids content,and the expression level of cholesterol metabolism related genes in liver tissue were determined by QPCR and Western blotting;sterol-regulatory element-binding protein-2(SREBP-2)gene knockout/overexpression adenovirus vector were constructed to find out the effect of FGF21 on cholesterol metabolism and its mechanism in atherosclerotic process.The study indicated that,1.Loss of FGF21 led to a significant exacerbation of atherosclerotic plaque formation in apoE-/-mice.Compared to apoE-/-mice,DKO mice had more atherosclerotic plaques detected by oil-red staining.Immunohistochemical results showed that vascular macrophage infiltration and vascular smooth muscle fibrosis were more serious in DKO mice.Serum level of cholesterol ester in brachiocephalic artery was higher in DKO mice determined by biochemical assays.2.DKO mice illustrated exacerbated hyperlipidemia and augmented inflammation.Bio-assays results showed that DKO mice had higher serum levels of total triglyceride(TG),total cholesterol(TC),low density lipoprotein(LDL),very low density lipoprotein(VLDL)and lower levels of high density lipoprotein(HDL)than apoE-/-mice.Real-time quantitative PCR results showed that compared to apoE-/-mice,DKO mice had higher expression levels of ICAM-1,VCAM-1,VCAM-1,MCP-1 and TNF-?m RNA in aortic tissue.The results obtained in Bio-assays also showed that DKO mice had higher serum level of ICAM-1,VCAM-1,MCP-1 and TNF-?than apoE-/-mice.3.Compared to apoE-/-mice,DKO mice had lower adiponectin level and lower m RNA expression level of adiponectin in the adipose tissue.FGF21 exerted its anti-atherosclerotic effects via both adiponectin-dependent and–independent mechanisms.Compared to apoE-/-mice,DKO mice had lower serum adiponectin level and lower adiponectin m RNA expression level in the adipose tissue.Studies of replenishment of recombinant FGF21 protein and adiponectin showed that exogenous replenishment of FGF21 prevented atherosclerosis in apoE-/-mice via two independent mechanisms–one was inducing the adipocyte production of adiponectin which in turn acted on the blood vessels to inhibit neointima formation and macrophage inflammation,the other was suppressing the hepatic expression of the transcription factor sterol regulatory element-binding protein-2,thereby leading to reduced cholesterol synthesis and attenuation of hypercholesterolemia.Chronic treatment with adiponectin partially reversed atherosclerosis without obvious effects on hypercholesterolemia in FGF21-deficient apoE-/-mice.In conclusion,FGF21 deletion promoted the process of atherosclerosis in apoE-/-mice by increasing inflammation and hyperlipidemia.The anti-atherosclerotic effect of FGF21 was mediated by fine tuning the multi-organ crosstalk among liver,adipose tissue,and blood vessels via both adiponectin-dependent and–independent mechanisms.