A Study On The Parasympathetic Regulation Mechanism Of Aerobic Exercise In Improving Myocardial Hypertrophy Induced By Coarctation Of The Aorta

Objectives:Background:After myocardial hypertrophy,parasympathetic nerve function weakens,autonomic nerve imbalance,excessive proliferation of collagen fibers,significant decline of cardiac function,resulting in heart failure,while myocardial hypertrophy induces mitochondrial damage,endoplasmic reticulum stress and inflammatory reticulum.It is an important factor leading to myocardial pathological changes and heart failure.Therefore,it is necessary to improve parasympathetic nerve function and reduce mitochondrial injury,endoplasmic reticulum stress and inflammation in the prevention and treatment of myocardial hypertrophy.It is reported that aerobic exercise and choline can activate parasympathetic nerve,improve cardiac function,and improve mitochondrial and endoplasmic reticulum dysfunction,which is a safe and effective intervention to protect cardiac hypertrophy.The purpose of this thesis is to explore the molecular mechanism ofaerobic exercise and choline intervention to activate parasympathetic nerve to regulate mitochondrial quality control,endoplasmic reticulum stress and inflammation,and reduce cardiac hypertrophy induced by coarctation of aorta.To provide theoretical and experimental basis for exercise and choline intervention to prevent and reduce myocardial hypertrophy.Methods:Male 8-week-old C57 mice,weighing 18-22 g[SPF grade,purchased from Beijing Vital River Laboratory Animal Technology Co.,Ltd.,Animal Certification No:SCXK(Jing)2016-0006].They were randomly divided into sham-operated control 1 week group(SHAM1wk),sham-operated control 3 week group(SHAM3wk),sham-operated control 5 week group(SHAM5wk),sham-operated control 9 week group(SHAM9wk),transverse aortic constriction 1 week group(TAC1wk),transverse aortic constriction 3 week group(TAC3wk),transverse aortic constriction 5 week group(TAC5wk),transverse aortic constriction 9 week group(TAC9wk),transverse aortic constriction+exercise 3 week group(TE3wk)(intervention 2wk),transverse aortic constriction+exercise 5 weeks group(TE5wk)(intervention 4wk),transverse aortic constriction+exercise 9 weeks group(TE9wk)(intervention 8wk),transverse aortic constriction+choline 3 weeks group(TC3wk)(intervention 2wk),transverse aortic constriction+choline 5 weeks group(TC5wk)(intervention 4wk),transverse aortic constriction+choline 9 weeks group(TC9wk)(intervention 8wk),transverse aortic constriction+exercise+choline 3 weeks group(TEC3wk)(intervention 2wk),transverse aortic constriction+exercise+choline 5week group(TEC5wk)(intervention 4wk),transverse aortic constriction+exercise+choline 9week group(TEC9wk)(intervention 8wk),3in each group.Another 50 mice were randomly divided into 5 groups:sham-operated control group(SHAM),transverse aortic constriction group(TAC),transverse aortic constriction+exercise group(TE),transverse aortic constriction+choline group(TC),transverse aortic constriction+exercise+choline group(TEC),10 in each group.Mice were fed with national standard feed and fed freely.The model of cardiac hypertrophy was made by transverse aortic constriction.After the model was successfully established,the mice were fed with 1wk and received aerobic exercise training and choline injection intervention.TE group and TEC group were given aerobic treadmill training for 8wk.At the beginning of the training,the adaptive training of 5min was carried out at the speed of 3m/min,then increased to the speed of 8m/min for 5 minutes,and finally moved at the speed of 12m/min for 50 minutes,1h/d,5d/wk×8wk.The TC group and the TEC group were injected with choline for 8 weeks.The injection dose of choline was14mg/kg/d,7d/wk×8wk.The SHAM group was reared quietly for 8wk without treadmill exercise.After 2wk,4wk,8wk treadmill exercise and choline injection,the mice were anesthetized with isoflurane after fasting for 12 hours the day before.Electrocardiogram and echocardiogram were collected to evaluate parasympathetic nerve and cardiac function.After that,the blood was quickly taken from the eyes and the heart was removed for later experiments.The myocardial mitochondrial function of mice was detected by O2K mitochondrial function test system.the percentage of myocardial collagen volume(Collagen volumefraction,CVF)was observed by Sirius red staining.The size of cardiomyocytes was observed by HE staining.CK and LDH kits measure the degree of cardiac damage.The mitochondrial morphology of myocardial cells was observed by transmission electron microscope.M2AChR,Parkin,PINK 1,LC 3,MFN2,MFN1,OPA1,Drp1,BNIP3,NLRP3,IL-1?,Caspase-1,CHOP,GRP78,eIF2?,p-eIF2?,PERK,p-PERK and ATF4 were detected by Western blotting test.Results:(1)Aerobic exercise and choline intervention inhibit cardiac dysfunction in the process of cardiac hypertrophy induced by transverse aortic constriction.After three weeks of TAC,the myocardial systolic function decreased significantly and the left ventricle dilated.Four-week aerobic exercise and choline intervention significantly decreased the values of LVEDD and LVESD,and significantly increased the values of EF%and FS%.The results showed that TAC for three weeks could be used as the zero point for the evaluation of myocardial hypertrophy,and the cardiac function was seriously disordered after five weeks and tended to failure at nine weeks,while aerobic exercise and choline intervention significantly inhibited left ventricular dilatation and maintained cardiac contractile function.The effect was more significant after eight weeks of intervention,and the effect of combined intervention was better.(2)Aerobic exercise and choline intervention can reduce the damage of mitochondrial structure in the process of cardiac hypertrophy induced by TAC.After five weeks of TAC,the arrangement of mitochondria was disordered,fragmented,cristae dissolved,sarcomere dissolved and broken,Z line blurred,and mitochondria seriously damaged.After four-week aerobic exercise and choline intervention,the arrangement of mitochondrial fibers and sarcomere tended to be normal,the fragmentation of mitochondria decreased,the crest was dense and orderly,the structure of intercalated disc was clear and the connection was complete.After eight weeks of aerobic exercise and choline intervention,the Z line was obvious,the number of mitochondria increased,the swelling relieved slowly,the arrangement was regular,and the structure of mitochondria was significantly improved.The results showed that aerobic exercise and choline intervention reduced the structural damage of mitochondria in the process of myocardial hypertrophy induced by coarctation of aorta.(3)Aerobic exercise and choline intervention regulate mitochondrial division and autophagy at different time points after aortic coarctation,and enhance mitochondrial quality control.After 5 and 9 weeks of TAC,the mitogen protein Drp1 increased significantly,while the expression of Drpl in aortic coarctation myocardium decreased significantly after aerobic exercise and choline intervention for four weeks and eight weeks.Nine weeks after TAC,the autophagy protein BNIP3 increased significantly,while the expression of BNIP3 in aortic coarctation myocardium decreased significantly after aerobic exercise and choline intervention for eight weeks.The combined intervention effect of aerobic exercise and choline is better.There were no regular and significant differences among the groups of OPA1.The results showed that aerobic exercise and choline intervention regulated mitochondrial division and autophagy at different time points after TAC,and strengthened the quality control of mitochondria.(4)Eight-week aerobic exercise and choline intervention significantly inhibited the decrease of cardiac parasympathetic nerve function after TAC.Aerobic exercise and choline intervention can significantly increase the value of HFn and significantly reduce the value of LFn and LFIHF.The results showed that eight-week aerobic exercise and choline intervention significantly inhibited the decrease of cardiac parasympathetic nerve function after TAC,increased HRV,and improved autonomic nervous disorders induced by TAC.The combined intervention effect of aerobic exercise and choline is better.(5)Eight-week aerobic exercise and choline intervention significantly inhibited cardiac injury in mice after TAC.Eight-week aerobic exercise and choline intervention could significantly inhibit the increase of myocardial collagen volume percentage,cardiomyocyte size,CK and LDH after TAC.The combined intervention effect of aerobic exercise and choline is better.The results showed that eight-week aerobic exercise and choline intervention significantly inhibited cardiomyocyte swelling,fibrosis and myocardial damage in mice after TAC,and improved cardiac function.(6)Eight-week aerobic exercise and choline intervention significantly improved the mitochondrial function of cardiac hypertrophy induced by TAC.After cardiac hypertrophy,the maximum oxidative phosphorylation ability of mitochondrial complex? and ? and the electron transport ability of mitochondrial complex ? decreased significantly,while the maximum oxidative phosphorylation ability of mitochondrial complex ? and ? and the electron transport ability of mitochondrial complex ?increased significantly after aerobic exercise and choline intervention.The results showed that eight-week aerobic exercise and choline intervention significantly improved the mitochondrial function of the heart after TAC.(7)Eight-week aerobic exercise and choline intervention significantly improved the parasympathetic function of the heart after TAC.The expression of parasympathetic nerveM2AChR decreased significantly after myocardial hypertrophy,while the expression of M2AChR increased significantly after aerobic exercise and choline intervention.The expression of M2AChR protein in TEC group was significantly higher than that in TE and TC group.The results showed that eight-week aerobic exercise and choline intervention significantly improved cardiac parasympathetic nerve function after TAC.And the combined intervention of the two can improve the parasympathetic nerve better.(8)Eight-week aerobic exercise and choline intervention regulate myocardial mitochondrial fusion,division and autophagy after TAC,and improve mitochondrial quality control.Compared with SHAMgroup,Drp1,MFN2,MFN1,BNIP3,LC3II,Parkin in TAC group was significantly higher,Drp1,MFN2,MFN1,BNIP3,LC3II,Parkin in TE and TEC groups was significantly lower than that in TAC group,Drpl,MFN2,MFN1,BNIP3,LC3II in TC group was significantly lower than that in TAC group,but Parkin was not decreased,PINK1 in TAC group was significantly lower than that in SHAM group,PINK1 in TE,TC and TEC groups was significantly higher than that in TAC group,and there was no significant difference among OPA1 groups.The results showed that eight-week aerobic exercise and choline intervention regulated myocardial mitochondrial fusion,division and autophagy after TAC,and improved mitochondrial quality control.(9)Eight-week aerobic exercise and choline intervention significantly reduced myocardial endoplasmic reticulum stress and inflammatory response,inhibitedmyocardial hypertrophy and improved cardiac function after TAC.Compared with SHAM,the expression of endoplasmic reticulum stress-related proteins p-eIF2a,eIF2a,GRP78,CHOP,p-PERK,ATF4 and inflammation-related protein NLRP3,Caspase-1,IL-1? increased significantly in TAC group,while the expression of p-eIF2a,eIF2a,GRP78,CHOP,p-PERK,ATF4 and NLRP3,Caspase-1,IL-1? decreased significantly in TE,TC and TEC groups compared with TAC group.Compared with TE and TC,each index of TEC group was slightly lower,and there was no significant difference in PERK protein expression among groups.The effect of combined intervention of exercise and choline is better.The results showed that eight-week aerobic exercise and choline intervention significantly reduced myocardial endoplasmic reticulum stress and inflammation,inhibited myocardial hypertrophy and improved cardiac function after TAC.Conclusions:(1)Aerobic exercise and choline intervention regulate mitochondrial quality control and improve mitochondrial and cardiac function in the time window of cardiac hypertrophy induced by TAC.Four-week intervention could significantly improve myocardial mitochondria and cardiac function after TAC,but the improvement of cardiac function after eight-week intervention was better.And the combined intervention effect of aerobic exercise and choline is better.(2)Eight-week aerobic exercise and choline intervention can inhibit myocardial hypertrophy and improve cardiac function by activating parasympathetic nerve to regulate mitochondrial quality control.The combined effect of aerobic exercise and choline intervention is better.(3)Eight-week aerobic exercise and choline intervention can activate parasympathetic nerves to regulate PERK/eIF2?/ATF4 endoplasmic reticulum stress pathway and NLRP3/Caspase-1/IL-1? inflammatory pathway,and then reduce endoplasmic reticulum stress and inflammatory response,inhibit myocardial hypertrophy and improve cardiac function.The combined effect of aerobic exercise and choline intervention is better.In summary,aerobic exercise and choline intervention can activate parasympathetic nerves to regulate mitochondrial quality control,endoplasmic reticulum stress and inflammatory response,inhibit myocardial hypertrophy induced by TAC,and improve cardiac function.And the combined intervention is better.