Effect Of GCN2 Gene Deficiency On Exercise-induced Cardiac Hypertrophy

Objective Athletes' hearts have received much attention in the field of medicine and sports science for many years.So far,the molecular mechanism of exercise-induced cardiac hypertrophy has not been fully elucidated.Studies have shown that GCN2 has cardiac protective effect.Therefore,we established the model of exercise-induced cardiac hypertrophy by 7-week treadmill training in mice,and discussed the role and regulation mechanism of GCN2 in exercise-induced cardiac hypertrophy by GCN2 gene knockout.In order to further explain and understand the mechanism of exerciseinduced cardiac hypertrophy.Methods 8-week-old male wild(WT)mice and GCN2 gene knockout(KO)mice were randomly divided into WT+Ctr group,WT+Ex group,KO+Ctr and KO+Ex group.WT+Ex and KO+Ex trained for 7 weeks of treadmill training to establish a model of exercise induced cardiac hypertrophy.Cardiac histomorphology analysis and cardiac function test were used to evaluate the occurrence of exercise induced cardiac hypertrophy and the effect of GCN2 knockout on exercise exercise induced cardiac hypertrophy.Cardiac histomorphology analysis mainly includes: heart weight,the ratio of the left ventricular weight to body weight,and the ratio of the left5 ventricular weight to tibia length;the measurement of myocardial cell cross-sectional area by WGA fluorescence staining;the detection of myocardial fibrosis by Sirius Red staining;the evaluation of cardiac morphology by Echocardiography.The evaluation of cardiac function was mainly measured by echocardiography.Effects of exercise on expression of GCN2 signaling pathway,C/EBP? signaling pathway,AMPK signaling pathway related proteins and effects of GCN2 knockout on downstream signaling pathway related proteins expression were detected by Western blotting.Results(1)Cardiac Indexes of mice in WT+Ctr and KO+Ctr groups under basic conditionThere was no significant difference in the heart weight(HW/BW?HW/TL),left ventricular weight(LVW/BW?LVW/TL),echocardiographic parameters(LVID'd?LVID's?IVS'd?IVS's?LVPW'd?LVPW's?LV mass?EF?FS),and the myocardial cell cross-sectional area(CSA).(2)Cardiac Indexes of mice in WT+Ex and KO+Ex groups after seven weeks of treadmill trainingCompared with WT Ctr group,the heart weight,left ventricular weight and CSA of,WT Ex group were significantly increased(P<0.05);among the echocardiographic index,only LVID's ?IVS's had no significant difference(P>0.05),while the other indexes increased significantly(P<0.05).There was no significant difference in the above indexes between KO+Ex group and KO+Ctr group(P>0.05).The heart weight,left ventricular weight?CSA?and LVID'd?LVPW's?LV mass in KO+Ex group were significantly lower than those in WT+Ex group(P<0.05).(3)Degree of myocardial fibrosis of mice in all groupsThere was no change of myocardial fibrosis in WT+Ctr,KO+Ctr,WT+Ex and KO+Ex groups,and there was no significant difference between each group(P>0.05).(4)Protein expression level of GCN2 signaling pathway in the heart of mice in all groupsThe expression of GCN2 protein in WT+Ex group was significantly lower than that in WT+Ctr group(P<0.05),and no expression of GCN2 protein in heart of KO+Ctr and KO+Ex groups.There was no significant difference in eIF2?phosphorylation level and ATF4 protein expression level between WT+Ctr group and KO+Ctr group(P>0.05);after 7 weeks of treadmill training,the level of eIF2?phosphorylation and the expression of ATF4 protein in WT+Ex were significantly lower than those in WT+Ctr group(P<0.05),there was no significant difference between KO+Ex and KO+Ctr group(P<0.05);In addition,the phosphorylation level of eIF2? and the expression of ATF4 protein in KO+Ex group were significantly higher than those in WT+Ex group.(P<0.05).(5)Protein expression levels of C / EBP ? and CITED4 in the hearts of mice in each groupThere was no significant difference in the expression of C/EBP? and CITED4 protein between WT+Ctr group and KO+Ctr group(P>0.05);After 7 weeks of treadmill training,the expression of C/EBP? protein in WT+Ex group was significantly lower(P<0.05)and the expression of CITED4 protein in WT+Ex groupwas significantly higher(P<0.05)than those in WT+Ctr group,however,there was no significant difference between KO+Ex and KO+Ctr group(P>0.05);In addition,the expression level of C/EBP? protein in KO+Ex group was significantly higher than that in WT+Ex group,while the expression level of CITED4 protein was significantly decreased in KO+Ex group.(P<0.05).(6)Protein expression level of AMPK signaling pathway in the heart of mice in all groupsThere were no significant difference in the level of AMPK? phosphorylation and the expression of PGC1? and SIRT1 protein between WT+Ctr group and KO+Ctr group(P>0.05);After 7 weeks of treadmill training,the level of AMPK?phosphorylation and the expression of PGC1? and SIRT1 protein in WT+Ex were significantly higher than those in WT+Ctr group(P<0.05),but there was no significant difference between KO+Ex and KO +Ctr group(P>0.05);moreover,the expression level of SIRT1,PGC1? protein in KO+Ex group was significantly lower than that in WT+Ex group.(P<0.05).Conclusion(1)After 7 weeks of treadmill training,wild-type mice could induce exerciseinduced cardiac hypertrophy,which showed adaptive changes in heart size,shape and function.(2)7-week treadmill exercise could reduce the protein expression of the CGN2 signaling pathway,reduce the protein expression of the C/EBP?,and increase the protein expression of the AMPK signal pathway.(3)GCN2 signaling pathway may be involved in the regulation of exercise-induced cardiac hypertrophy by affecting C/EBP? signaling pathway and AMPK signaling pathway.(4)GCN2 gene deficiency can inhibit exercise-induced cardiac hypertrophy.It is suggested that GCN2 may play an important role in the occurrence and development of exercise-induced cardiac hypertrophy.