Effects Of Different Load Training On Mitochondrial Fusion Function And Energy Metabolism Of Skeletal Muscle In Mice

Purposes:To explore the effects of 6-week different load training on skeletal muscle mitochondrial fusion function and energy metabolism and their correlations,and to explain the adaptability of skeletal muscle to exercise and the degree of mitochondrial fusion function and energy metabolism at the molecular level,provide targeted exercise programs,and provide suggestions for reducing body damage and disease treatment.Methods: C57BL/6J healthy male mice were randomly divided into 4 groups,the quiet control group(C group,n = 8),the low-load exercise group(L group,n = 8),the moderate load exercise group(M group,n = 8),Load exercise group(H group,n = 8).After training in the training group for 1 week,the mice were immediately trained on the running platform,and a low-load,medium-load,and heavy-load training platform was established.The training program is: 5 days/week,1 time/day for 6 weeks.In the first week,the L,M,and H groups ran for 30 minutes at 3 m/min,10 m /min,and 18 m/min,respectively.In the second week,the third week,and the fourth week,the treadmill speed increased by 2 m/min per week,but the time of the L group and the M group was extended by 10 minutes per week,while the time of the H group was extended by 20 minutes per week.Six weeks maintain the speed and time of the fourth week.The final speed and time of the L,M,and H groups were: 9 m/min for 60 min,16 m/min for 60 min,and 24 m/min for 90 min.Twenty-four hours after the last training,the mice were sacrificed,and quadriceps and gastrocnemius tissue samples were taken.HE staining was used to observe cell morphological changes,biochemical methods were used to detect changes in energy metabolism indicators,and Western-blot method was used to detect mitochondrial fusion-related protein expression levels.Results: 1)After 6 weeks of different load exercise in mice,compared with group C,the ATP content of mitochondria of the quadriceps femoris in group M and H was significantly increased(p < 0.05).There was an upward trend but no significant change(p > 0.05).The activity of mitochondrial respiratory chain complex V in group H was significantly increased(p < 0.05),while the activity of complex V in medium and low load exercise group was increased but not significantly changed(p > 0.05).The citrate synthase activity of each training group was significantly reduced(p < 0.01),and the L group was significantly lower than that of the M and H groups(p < 0.05).(2)Among the skeletal muscle mitochondrial fusion proteins of mice,compared with group C,the expression of OPA1 in each group was not significantly changed(p > 0.05);the expression of MFN1 protein in the skeletal muscle of mice in the L,M,and H groups was significantly increased(p < 0.05);MFN2 levels increased significantly only in the M and H groups(p < 0.05),and at the same time significantly higher than the L group(p < 0.05).Among mitochondrial mitotic proteins,the expression level of DRP1 protein in group L and M was significantly higher than that in group C(p < 0.05).The expression of MFF protein in group H was significantly higher than that in group C(p < 0.05).There was an increase in L and M groups but there was no significant difference compared with group C(p > 0.05).Regarding the Protein expression content of mitochondrial biosynthetic proteins PGC-1a and TFAM,the three groups of training groups all increased to varying degrees,all of them increased significantly in the M group,with significant differences(p < 0.01).Compared with group C,COX IV protein expression in group M was significantly increased(p < 0.01),and group H was significantly reduced(p < 0.05).The CYC protein expression was also increased in the M group and decreased in the H group,with very significant differences(p < 0.01).(3)A comparison of mitochondrial energy metabolism enzyme activity and mitochondrialrelated protein expression in mouse skeletal muscle showed that ATP content was highly positively correlated with MFN1(p < 0.05).There were no significant correlations between cytochrome C oxidase activity and ATP synthase activity and various protein indicators(p > 0.05).CS activity was moderately negatively correlated with MFN1,DRP1,COX IV,and TFAM(p < 0.01)and highly negatively correlated with PGC-1a(p < 0.01).Conclusion:(1)Medium-load exercise can greatly increase mitochondrial energy metabolism level,and skeletal muscle cell energy metabolism level is also more sensitive to high-load exercise training,but not much changed to low-load exercise training.(2)Medium-load exercise training can improve mitochondrial fusion and biosynthetic ability,and high-load exercise training can increase mitochondrial division level more significantly.(3)There was no significant correlation between skeletal muscle energy metabolismrelated indicators and mitochondrial fusion protein expression.