Research Of The Effect And Mechanism Of FGF21 On Type 1 Diabetic Cardiomyopathy

Objective: To study the pathophysiological role of FGF21 in DCM and elucidate the mechanism of this process.Thus,providing a new way for clinical treatment.Methods: We did our study in vitro and in vivo to find out the effect of FGF21 on cardiomyocytes cultivated in high glucose solution and mechanisms behind the effect,as well as the role of FGF21 plays in progression of diabetic cardiomyopathy and mechanisms behing this role.Neonatal cardiomyocates were cultured by glucose media in different concentration,5mmol/L for normal group,33mmol/L for high density glucose group,both of them were then treated with FGF21 siNA.Four groups were set as follows: control group,high glucose group,FGF21 siRNA group and high glucose+FGF21 group.The effectiveness of FGF21 siRNA was detected by Elisa,morphological changes of cardiomyocytes were checked by lightning microscope,ultrastructural changes were observed by transmission electron microscope,expression levels of β-MHC,α-MHC,ANP were detected by Real-time PCR.Male mice with C57/BL6 J background were used in animal experiment.38 eight weeks old mice were divided into five groups: normal group(n=6),negative control group(n=6),FGF21 siRNA group(n=10),type 1 diabes group(n=6),type 1 diabetes + FGF21 siRNA group(n=10).Type 1 diabetes mellitus was induced to mice in DCM and DCM + FGF21 siRNA group while FGF21 expression was inhibited by FGF21 siRNA in mice of normal + FGF21 siRNA group and DCM + FGF21 siRNA group.Type 1 diabetes mellitus models,with blood glucose levels over 16.9mmol/L,were successfully constructed 72 hours after intraperitoneal injection of streptozotocin(Sigma-Aldrich,St.Louis,MO,USA)at the dose of 150 mg/kg.FGF21 expression was inhibited by FGF21siRNA(Genepharma,Shanghai,China)at twelfth week since diabetic models have been established,FGF21 siRNA,which has been dissolved in Diethylpyrocarbonate and glucose solution,was administrated through tail vein at a dose of 5 mg/Kg.One week later,expression of plasma FGF21 was detected by Elisa,FGF21 expression in heart and liver was detected by Real-time PCR.Cardiac function was measured by echocardiography,morphological changes and cardiac fibrosis were detected by HE staining and Masson staining respectively.Real-time PCR was used to determine expression level of ANF,α-SKA,TGF-β,Col I,Col III,TEM was used to quantify the lipid droplets,Elisa kit was apllied to analyze cardiac triglyceride concentration,plasma triglyceride and cholesterol were also analized,western blot was used to check the expression of PGC-1α and CD36.Result: Cardiomyocytes treated with FGF21 siRNA expressed less FGF21 than those cultured in glucose of normal density.Cardiomyocytes in high glucose group showed marked hypertrophy,accompanied with elevated expression of β-MHC,α-MHC,ANP,after FGF21 inhibition,both of the extent of cardiomyocyte hypertrophy and expression level of the hypertrophy markers increased.Cardiomyocytes cultured in high concentration glucose accumulated more Lipid droplets than in normal concentration glucose,which became more significant after FGF21 inhibition.Type 1 diabetic mice showed lowered cardiac function,FGF21 inhibition induced by FGF21 siRNA decreased it further.Expression level of FGF21 in FGF21 siRNA group and type 1diabetes + FGF21 siRNA group were respectively lesser than control group and type 1 diabetes group.Mophology of mice Cardiomyocytes in control group were normal,FGF21 siRA treatment did not affect it,negative control group showed no significant change when compared with normal group,while type 1 diabetes mice showed cardiomyocyte hypertrophy,which was exacerbated after FGF21 inhibition.There was no difference between control group,negative control group and FGF21 siRNA group in terms of cardiac fibrosis,while type 1 diabetes showed significant fibrosis and it became aggrevated after FGF21 siRNA treatment.ANF,α-SKA,TGF-β,Col I,Col III expressed in type 1 diabetes group were much more elevated after FGF21 inhibition,as well as the quantity of lipid droplets,triglyceride concentration in heart and plasma and plasma choleaterol,accomoanied by further downregulated expression of PGC-1 α and upregulated expression of CD36.Conclusion: FGF21 inhibition promoted high concentration glucose induced cardiomyocyte hypertrophy,along with elevated lipid concentration.FGF21 inhibition exacerbated cardiac hypertrophy and cardiac fibrosis in type 1 diabetic mice,accompanying with lowered cardiac function,which is associated with lipid accumulation resulted from abnormal expression of PGC-1α and CD36.