| Background and Purpose: Skeletal muscle is a highly malleable organ.The deterioration of the musculoskeletal system causes muscle atrophy and bone mass loss,which in turn leads to reduced motor performance.Previous studies have shown that young rats have strong plasticity of skeletal muscle fiber types during endurance exercise,and that PGC-1? and PGC-1? are believed to affect skeletal muscle fiber types.This study aims to investigate the differences in fiber type transitions between different types of skeletal muscles during endurance exercise in young rats and aging rats,and whether there is a difference in PGC-1?/PGC-1?.Methods: 12 young male SD rats aged 8weeks old were randomly divided into young control group(Y group)and youth exercise group(YE group);12 male SD senile rats aged 22 months were randomly divided into elderly control group(O group)and elderly exercise group(OE group).Rats in the exercise group were trained on the treadmill with a gradient of 0° using tail-stimulation and manual drive.The endurance exercise program of the young rat exercise group was 20m/min for 30 minutes in the first week,25m/min for 30 minutes in the second week,30m/min for40 min in the third week,and 35m/min for 40 min in the 4-12 week,training six days a week,closed on Sunday.The endurance exercise program of the aged rat exercise group: speed 10-15m/min,time 40-50min/day,training six days per week,and Sunday rest for a total of 12 weeks.The rats stopped fasting 24 hours after training were taken by intrape-ritoneal injection of 20% urethane(5ml/ kg)anesthesia,and the extensor digitorum longus(EDL)and soleus muscle(SOL)of both legs of the rat's legs were quickly separated and removed.Succinic dehydrogenase(SDH)activity was measured by colorimetry.The fiber type was determined by MHC SDS-PAGE electrophoresis.The protein content and gene expression of PGC-1? and PGC-1?were detected by western blot and real-time PCR respectively.All data was processed using SPSS16.0 software.Results: 1.The SDH activity of SOL and EDL of old rats decrease(P<0.05).Endurance exercise increased the SDH activity of SOL(P<0.01)and EDL(P<0.05)in young rats and aged rats.2.Compared with the young rats,the proportion of MHCIIa protein in the SOL of aged rats decreased(P<0.01);the proportion of MHC I protein increased(P<0.01);the proportion of MHCIIb protein in EDL decreased(P<0.01),and the proportion of MHCIIa protein increased(P<0.01).3.After theendurance exercise,the MHC of the SOL changed: the proportion of MHC I protein in the young exercise group was higher than that in the young control group(P<0.01),while the proportion of MHCIIa protein in the old exercise group was higher than that in the old control group(P<0.05).Changes in MHC of EDL after Endurance Exercise:The proportion of MHC I protein(P<0.01)and MHC II a protein(P<0.05)in young exercise group rats was higher than that in young control group,and MHC II b protein was decreased(P<0.01),while there was no difference among older rats(P>0.05).4.Compared with the young rats,the expression of PGC-1? mRNA and PGC-1? mRNA in the SOL and EDL significantly decreased in aged rats(P<0.01).After endurance exercise,the expression of PGC-1? mRNA in the SOL of young rats and aged rats was significantly lower(P<0.05).5.The expression of PGC-1? protein in the SOL and EDL in the youth exercise group was significantly higher than that in the youth control group(P<0.01),but there was no statistical significance among the other groups(P>0.05).The PGC-1? protein content also did not differ among all groups(P>0.05).Conclusion: 1.Endurance exercise promotes the conversion of skeletal muscles from fast to slow muscles in young rats.2.Endurance exercise helps to slow down the loss of slow muscle IIa muscle fibers in aged rats,but does not affect fast muscle fiber types.3.Endurance exercise increased PGC-1? protein expression in both slow and fast muscles of young rats,but it did not affect older rats. |
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