| Objective: in naturally-aged SPF Wistar rats,the protective mechanisms of different exercise interventions(such as endurance exercise and resistance exercise)on senescent cardiomyocytes was explored to provide a reference for the prevention and rehabilitation of age-related diseases through exercise intervention.Methods:thirty 6-month-old male Wistar rats after fed to 21 months old,were randomly divided into old control group(OC group),old endurance exercise group(OE group)and old resistance exercise group(OR group),with 10 rats in each group.The duration of all exercise interventions was 12 weeks.For OE group the rats were provided with treadmill running with a gradient of 10° for endurance exercise training,5 days/week,and 45 min/ day(15 m/min);For OR group the rats were subjected to resistance training for ladder climbing with tail loaded burden,5 days/week,2 sets/time,3 repetitions for each set,with the rest interval of1 minute between repetitions,and 2 minute between sets.Myocardial tissue samples were harvested after the last exercise intervention for 24 hours.The HE staining and TUNEL staining were used to observe structure changes and cell apoptosis of rats myocardium.Western Blot was used to detect the expression levels of some proteins associated with autophagy,apoptosis and cell cycle in cardiac myocytes.In addition,eight 6-month-old rats were selected as the youth control group(YC group).Results : 1.HE staining: compared with YC group,cardiomyocytes in OC group revealed irregular arrangement and unclear cell boundaries.Meanwhile,significantly increased myocardial interstitial cells were observed.Compared with OC group,the myocardial cells in OE group and OR group were arranged in a relatively orderly manner with obvious cell boundaries,and the myocardial interstitial cells were significantly decreased.2.TUNEL staining: compared with YC group,the number of the Cells with positive staining in OC group was significantly increased(p < 0.001),but compared with OC group,the number of the cells with positive staining in OE and OR groups was significantly reduced(p < 0.001);and compared with OE group,the number of the cells with positive staining in OR group was significantly reduced(p < 0.05).3.Western Blot of the proteins associated with IGF-1/PI3K/Akt/mTOR signaling pathway:compared with YC group,the expression levels of IGF-1R,PI3 K and p-Akt/Akt inrat myocardium from OC group were significantly decreased(p < 0.001),indicating that IGF-1R/PI3K/Akt/mTOR signaling pathway was activated in the myocardium of aging rats.However,compared with OC group,IGF-1R and PI3 K expression were significantly up-regulated(p < 0.001),p-Akt/Akt and p-mTOR/mTOR expression were significantly down-regulated(p < 0.05)in rat myocardium from OE group;meanwhile,IGF-1R,PI3 K and p-Akt/Akt expression were significantly up-regulated(p < 0.001)in rat myocardium from OR group(p < 0.001).Finally,compared with the OE group,IGF-1R expression was significantly down-regulated(p < 0.01),PI3 K and p-Akt/Akt expression were significantly up-regulated(p < 0.05)in rat myocardium from OR group(p < 0.001).These results showed that both endurance exercise and resistance exercise could improve the elderly rat myocardial IGF-1/PI3K/Akt/mTOR signaling pathway.4.Western Blot of autophagy-related proteins: compared with YC group,the ratio of LC3-II/LC3-I in the rat myocardium from OC group was significantly decreased(p < 0.001),and p62 expression in the rat myocardium from OC group was significantly increased(p <0.001),suggesting that the functional status of autophagy in the aged rats myocardium was lower than that of the young group.In addition,compared with OC group,the ratio of LC3-II/LC3-I in the rat myocardium from OE group was significantly increased(p < 0.001),and p62 expression was significantly increased(p < 0.05).And compared with OC group,the ratio of LC3-II/LC3-I in the rat myocardium from OR group was significantly increased(p <0.01).Compared with the OE group,the ratio of LC3-II/LC3-I in the rats myocardium of OR group was significantly decreased(p < 0.01),and p62 expression was significantly increased(p < 0.01).These results indicated that both endurance exercise and resistance exercise could improve the functional status of autophagy,or rescue the deficient autophagy in the myocardium of aged rats.5.Western Blot of apoptosis-related protein: compared with YC group,Bcl-2 expression was significantly decreased(p < 0.001),and Bax,caspase-9,FasL,caspase-8,Cleaved caspase-3 expression were significantly increased(p < 0.05)in the rat myocardium from OC group,which showed the elderly rats myocardial apoptosis resistance was lower than the young,and elderly rats myocardial endogenous and exogenous apoptosis level obviously is higher than the youth.In addition,compared with OC group,Bcl-2 expression was significantly increased(p < 0.001),and Bax,FasL,caspase-8 and Cleaved caspase-3expression were significantly decreased(p < 0.05)in the rat myocardium from OE group;Bcl-2 expression was significantly increased(p < 0.05),FasL,caspase-8,caspase-9 andCleaved-caspase-3 expression were decreased significantly(p < 0.001)in the rat myocardium from OR group.Lastly,compared with OR group,Bcl-2 expression was significantly increased(p < 0.05),caspase-9 and caspase-8 were significantly increased(p < 0.001)in the rat myocardium from OE group.These results displayed that both endurance exercise and resistance exercise could reduce the elderly rats myocardial apoptosis level,enhance the anti-apoptosis ability.And that,combined with TUNEL staining,the anti-apoptotic ability of resistance exercise was better than that of endurance exercise.6.Western Blot of the proteins associated with the cell cycle: compared with YC group,CyclinD1,CDK4 and p-Rb/Rb expression myocardium were significantly decreased(p <0.001),while p21 expression was significantly increased(p < 0.001)in the rat myocardium from OC group,suggesting that the cell cycle regulation ability of the elderly rats was lower than that in the youth group.Compared with OC group,CyclinD1,CDK4 and p-Rb/Rb expression were significantly up-regulated(p < 0.01),and p21 expression was significantly down-regulated(p < 0.001)in the rat myocardium from OE group;simultaneously,CDK4 and p-Rb/Rb expression were significantly up-regulated(p < 0.001),p21 expression was significantly up-regulated(p < 0.001)in the rat myocardium from OR group.In the finally,compared with OE group,CyclinD1 expression was significantly down-regulated(p < 0.001),p21 and p-Rb/Rb expression were significantly up-regulated(p < 0.001)in the rat myocardium from OR group(p < 0.001).These results showed that both endurance exercise and resistance exercise could improve the ability of cell cycle regulation.What’s more,cell cycle regulation ability of resistance exercise is better than the endurance exercise.Conclusion:exercise could activate autophagy and cell cycle processes,as well as inhibit apoptosis by promoting the IGF-1/PI3K/Akt/mTOR signaling pathway to revealed irregular arrangement and unclear cell boundaries of cardiomyocytes in elderly rats. |
