The Protective Effect And Mechanism Of Selenium On Cardiac Remodeling Induced By High-fat Diet In Mice

Part? Cardiomycyte Injury and Cardiac Remodeling Due to Lipid OverloadObjective Autophagy is a catabolic process involved in maintaining energy and organelle homeostasis.Despite adverse consequences of lipid overload on cardiac structure and function,the contribution of lipid overload on cardiac autophagy remains uncertain.Thus,a study was conducted to investigate the impact of lipid overload on cardiac remodeling and cardiac autophagy in H9C2 cells and in mice.Methods The effects of palmitic acid(PA)on cell proliferation activity were analyzed by CCK-8 and cell cycle,and cell apoptosis were analyzed by Tunnel staining in cultured H9C2 cells.The C57BL/6J mice were randomly divided into the normal diet(ND)group and the high-fat diet(HFD)group,with 15-20 mice in each group.Total cholesterol(TC),total triglyceride(TG),glycosylated hemoglobin A1c(Hb A1c)and brain natriuretic peptide(BNP)in HFD group were analyzed and compared with ND group.The cardiac hypertrophic and fibrotic markers were identified with cross sectional area(CSA),the percent area of myocardial interstitial fibrosis(% area fibrosis),as well as related m RNA expression.Cardiac autophagy protein markers were examined by Western blot in C57BL/6J mice.The effect of PA on autophagy flux was detected in the absence or presence of 3-MA,CQ and Rapa in H9C2 cells.Moreover,the effect of PA on autophagic flux was monitored in H9C2 cells stably expressing stub RFP-sens GFP-LC3 or GFP-p62.Results PA effectively inhibited cell viability,and induced cell injury and cell apoptosis in H9C2 cells.The body mass,levels of blood glucose,TC,TG,insulin,as well as Hb A1 c were significantly increased in HFD group by comparison with that of ND group.The CSA,% area fibrosis,m RNA expression related to cardiac hypotrophy and fibrosis,and BNP level were also increased remarkably in HFD group compared with which of ND group.Importantly,cardiac autophagy degradation was remarkably suppressed in HFD group comparing with the ND group.In the present study,a significant increase in LC3-II and p62 expression was observed in H9C2 cells after exposure to PA treatments by comparison with the control group.After pretrements of 3-MA,CQ and Rapa in PA-induced H9C2 cells,our results indicated that CQ had no significant changes in LC3-II and p62 expression,3-MA dramatically decreased LC3-II and LC3-II/LC3-I expression,and increased p62 expression,whereas Rapa remarkably upregulated LC3-II and LC3-II/LC3-I expression and decreased p62 expression.We found that PA significantly increased the accumulation of autophagosome and suppressed the formation of autophagolysosome in H9C2 cells stably expressing stub RFP-sens GFP-LC3.Moreover,3-MA dramatically decreased autophagosome accumulation without obvious influencing autophagolysosome formation in PA+3-MA group compared with the PA group.Rapa significantly enhanced the accumulated autophagosome and autophagolysosome further after exposure to PA.However,we found no statistically significant difference between the number of autophagosome and autophagolysosome in the PA + CQ group compared with the PA group.In addition,we also found PA significantly increased the accumulation of GFP-p62 puncta in H9C2 cells stably expressing GFP-p62.The enhanced GFP-p62 puncta in PA group was increased further when autophagosomes formation was blocked by 3-MA,inversely,the enhanced GFP-p62 puncta in PA group was declined when autophagy was initiated by Rapa.However,the enhanced GFP-p62 puncta in PA group was not affected in the presence of CQ pretreatment.Conclusion Our data suggest that lipid overload cause H9C2 cell injury,and induce obesity,hyperglycemia,hyperinsulinemia,cardiac remodeling,cardiac dysfunction as well as suppressed cardiac autophagic degradation in C57BL/6J mice.Moreover,lipid-induced accumulation of autophagosomes is due to depressed autophagy degradation in H9C2 cells.Depressed autophagy degradation and cell viability are not restored in the pretreatment with 3-MA and CQ in response to PA in H9C2 cells,whereas,they are improved by the pretreatment with Rapa due to restored autophagy degradation in H9C2 cells.Autophagy regulation may be a new therapeutic target for the improvement of cardiac remodeling.Part II Selenium Administration Ameliorates Cardiac Remodeling Developed from High-Fat Diet in Mice through Regulation of AKT/GSK3? PathwayObjective High-fat diet(HFD)leads to cardiac remodeling and inhibition of autophagic degradation.Accumulated studies have suggested that selenium play roles in anti-oxidation,anti-apoptosis,as well as improvements in metabolic disorders.However,the effect and the underlying mechanisms that selenium administration suppresses or reverses cardiac remodeling induced by HFD are not yet clear.Therefore,the purpose of our research is to investigate the role and the mechanisms of selenium treatment on cardiac remodeling developed from lipid overload.Methods The C57BL/6J mice were randomly divided into four groups: normal diet with addition of selenium treatment(ND+Se)group,normal diet group(ND)group,high-fat diet group(HFD),high-fat diet with selenium treatment(HFD+Se)group,15-20 rats in each group.The indexes of serum TC,TG,Insulin and Hb A1 c of four groups in mice were analyzed and compared.The CSA,% area fibrosis and related m RNA expression of hypertrophic and fibrosis of mice in four groups were detected and compared.The effect of AKT/GSK3? signaling pathway on the autophagy activity were analyzed with Western Blot in H9C2 cells.Moreover,the effects of selenium on cardiac autophagic activity and AKT/GSK3? signaling pathway were analyzed with Western Blot in H9C2 cells and C57BL/6J mice.Results The increased serum TC and TG levels,the increased CSA,% area fibrosis,and m RNA expression related to cardiac hypotrophy and fibrosis in C57BL/6J mice induced by HFD were significantly reduced after the selenium treatment.Autophagy activity was identified to be regulated by AKT/GSK3? signaling pathway in H9C2 cells.It is noteworthy that in the current study,selenium treatment significantly downregulated AKT/GSK3? signaling pathway which was activated in response to lipid overload in H9C2 cells and in the cardiac tissue in C57BL/6J mice.Moreover,selenium treatment dramatically improved cardiac autophagic degradation which was suppressed after exposure to lipid overload in H9C2 cells and in the cardiac tissue in C57BL/6J mice.Counclusion Selenium treatment restored autophagic degradation in cardiac tissue probably through regulation of AKT/GSK3? signaling pathway.Selenium treatment improved metabolic disorders induced by HFD in mice,inhibited myocardial hypertrophy and fibrosis.Selenium administration can be used in the treatment and prevention in cardiac remodeling and heart failure associated with HFD or obesity.