Effects Of Four-week Aerobic Exercise On AMPK Signaling Pathway And Apoptosis-related Protein Expression In Doxorubicin-induced Skeletal Muscle Damage

Objective The aim of this study was to establish a doxorubicin-induced skeletal muscle damage model and observe the changes of skeletal muscle morphology and molecular biology in mice,and conducted four-week of swimming training before DOX administration to explore the regulatory mechanism of aerobic exercise on doxorubicin-induced skeletal muscle damage,provides a theoretical basis for the prevention of skeletal muscle damage caused by the clinical anti-tumor drug DOX.Methods 30 male C57BL/6 mice aged 12-16 weeks were selected and divided into sedentary normal saline group（SED-NS,n=6）,sedentary doxorubicin group（SED-DOX,n=8）,exercise normal saline group（EX-NS,n=8）,exercise doxorubicin group（EX-DOX,n=8）,Mice in the exercise group underwent four-week swimming training（aerobic exercise）,and mice in the sedentary group were routinely fed for four weeks.Two weeks of exercise preconditioning was performed before the start of the experiment,after the last exercise,the mice in the administration group were intraperitoneally injected with DOX(20 mg·kg^-1),and the equal volume of normal saline was injected into the control group.After 24 hours,all the mice were used to test the grip before and after DOX administration,and the changes of the grip strength were analyzed.WGA and TUNEL staining were used to detect the size of gastrocnemius muscle cells and the percentage of positive cells separately.Western blotting analysis was performed to determine the expression of the gastrocnemius muscle protein in mice.Results（1）The body weight of mice in the SED-DOX group was significantly decreased after doxorubicin administration compared with that before doxorubicin administration（P<0.01）,and that of mice in the EX-DOX group was significantly reduced also（P<0.05）.And the body weight of EX-DOX mice was significantly lower than that of EX-NS group（P<0.01）.SED-DOX group showed significantly lower grasping strength after the drug than before（P<0.05）.There was no statistical difference in grasping strength between each group（P>0.05）.After this drug administration,there was no statistical difference in GAS/TL ratio between the groups（P>0.05）.（2）The cross-sectional area of the gastrocnemius muscle cells in the SED-DOX group was significantly smaller than that in the SED-NS group in WGA staining（P<0.01）,and the mean diameter of skeletal muscle cells was the same（P<0.01）.The percentage of positive cells increased in SED-DOX and EX-DOX groups after DOX administration.（3）AMPKαphosphorylation levels in SED-DOX group and EX-DOX group were significantly reduced as compared with SED-NS group and EX-DOX group separately after doxorubicin administration（P<0.05）.While the phosphorylation level of AMPKαin EX-NS group and EX-DOX group was significantly increased as compared with SED-NS group and SED-DOX group separately after four-week aerobic exercise（P<0.01）.SIRT1 protein expression was significantly increased in EX-NS group and EX-DOX group compared with SED-NS group and SED-DOX group separately（P<0.05）.Compared with the SED-NS group,the expression of PGC-1αprotein in SED-DOX group was significantly decreased（P<0.05）,and the protein in EX-NS group was significantly increased（P<0.05）.The expression of PGC-1αprotein in EX-DOX group was significantly increased compared with SED-DOX group（P<0.01）.（4）Compared with the SED-NS group,the expression of Bax protein in the EX-NS group was significantly decreased（P<0.05）,and the protein in the EX-DOX group was significantly increased than that in the EX-NS group（P<0.001）.The expression of Bcl-2 protein in the EX-DOX group was significantly increased compared with the SED-DOX group（P<0.01）.And the ratio of Bax/Bcl-2 in the EX-NS group was significantly decreased compared with the SED-NS group（P<0.01）,in the EX-DOX group was also significantly decreased compared with the SED-DOX group（P<0.05）.Conclusion（1）DOX administration significantly reduced the body weight and grasping strength of mice,caused atrophy of skeletal muscle cells,increased the percentage of positive nuclei,and induced skeletal muscle damage.（3）Four-week aerobic exercise may improve the mitochondrial energy metabolism disorder caused by DOX administration by activating AMPK signaling pathway,and have a certain degree of protection against doxorubicin-induced skeletal muscle damage.（4）Four-week aerobic exercise may improve the imbalance of proapoptotic and anti-apoptotic protein levels in skeletal muscle cells by promoting the expression of Bcl-2 protein and inhibiting the expression of Bax protein.