The Effect Of Endurance Exercise On Antioxidant Capacity And Mitochondrial Biogenesis In Skeletal Muscle Of Aged Mice

Skeletal muscle is the power organ of movement, the maintenance of skeletal muscle mass and strength is the premise for people in various physical activities. Studies indicates that skeletal muscle mass and strength constantly decline in the aging process,this age-associated degenerative syndrome characterized by decline of skeletal muscle mass and strength is also called as "Sarcopenia", and it widely happens on older persons, increases the risk of falls and fractures, has a dramatic impact on the ability of daily lives and mobility of the elderly, and places a huge economic burden on family and society. As skeletal muscle is post-mitotic tissue, the reduced antioxidative capacity and the accumulation of oxidative damage are correlated with the age-associated decline of skeletal muscle mass and strength, especially mitochondria is the energy source of skeletal muscle contraction, the maintaince of mitochondria number and function is the premise of skeletal muscle constant contraction, the accumulation of oxidative damage and the reduced number of mitochondria during aging, seriously affect the skeletal muscle contractile function, however,long-term regular exercise can increase the activity of antioxidant enzymes, slowing the oxidative damage, is a effective intervention to attenuate the age-related skeletal degenerative syndrome. Objective:We choose3months old P6strain senescence accelerated mice as the aging model,8weeks treadmill exercise as the intervention measure,to investigate the effects of endurance training with different intensities on gene expression associated with antioxidant and mitochondrion biogenesis in aged skeletal muscle. Methods:54SAMP6mice randomly divided into senescence accelerated control group(P6),high intensity group(H),moderate intensity group(M),low intensity group(L), killed by cervical and dissected from gastrocnemius muscle.The authors measured the content of8-OH-dG through the Elisa kit,the activities of T-SOD、Cu-ZnSOD、MnSOD and catalase through Xanthine oxidase and visible spectrometry, the mRNA expression level of antioxidative gene Cu-ZnSOD、MnSOD、 PRDX1-6and mitochondrial biogenesis associated gene PGC-a/NRF-1/T-fam in gastrocnemius muscle by Real-Time PCR.and the protein content of mitochondrial biogenesis associated gene PGC-a/NRF-1/T-fam through western blotting. Results:(1) Compared with the Rl group,there was no significant difference in body weight, skeletal muscle mass and skeletal muscle mass index of P6male mice, female mice body weight increase significantly, skeletal muscle mass and skeletal muscle mass index reduced; Compared with the P6group,there was signicant decrease in body weight and skeletal muscle of high,medium and low intensity group male mice,while there was no significant difference in skeletal muscle mass index;there was no significance in female mice body weight,there was significant increase in skeletal muscle mass and skeletal muscle mass index.(2) Compared with the R1group, there was upward trend in8-OH-dG levels,but no significant difference,T-SOD activity was significantly decreased, in P6group male and female mouse;Cu-ZnSOD, MnSOD and CAT activity showed a downward trend, but no significant difference, Cu-ZnSOD, MnSOD mRNA significantly increased; compared with the P6group,there was a downward trend in8-OH-dG levels in female and male mice of high, medium, low-intensity exercise group, but no significant difference,T-SOD, Cu-ZnSOD, MnSOD and CAT activity were intended to increase in high, medium and low intensity group,but there was no significant difference, and except for catalase,Cu-ZnOD, MnSOD mRNA expression levels showed varying degrees of decline, with high-intensity exercise group optimal; compared with the R1group, male and female mice PRDX2, PRDX6and male mice PRDX3, PRDX5mRNA was significantly increased, while the female, male mice PRDX1, PRDX4and female mice PRDX3, PRDX5mRNA was no significant change; compared with P6group, high, medium and low intensity groups female mice PRDX1, male mice PRDX2and male and female mice PRDX6mRNA was significantly decline, high, medium intensity significantly decreased in male mice PRDX3, PRDX4,PRDX5and female mice PRDX1mRNA expression levels,especially in high-intensity group.(3)Compared with R1, P6group female and male mice PGC-1α and male mice NRF-1, T-fam mRNA expression levels were significantly increased,NRF-1,T-fam mRNA expression levels of female mice although there is an increasing tendency, but no significant difference, there was no difference in protein levels in female, male mice PGC-la/NRF-1/T-fam; compared with P6group, and8weeks high, medium and low intensity endurance training have no significant effects on PGC-la/NRF-1/T-fam protein levels, and high-intensity endurance training significantly reduces the NRF-1, T-fam mRNA expression levels of PGC-la in female mice and male mice movement, only a low intensity of the female mice reduces the expression level of PGC-1αmRNA.Conclusion:(1) In the aging process, skeletal muscle suffered different degrees attenuation;8weeks endurance training effectively delayed skeletal muscle attenuation in female mice, but the effect is not obvious in male mice, the mechanism of different responses to endurance training between male and female mice needs further study.(2) In the aging process, oxidative stress increases, ROS stimulates adaptation of the body’s antioxidant defense system and mitochondrial biogenesis-related genes at the transcriptional level; endurance exercise increases skeletal muscle oxidative stress, oxygen signal stimulates the expression of antioxidant enzymes and mitochondrial biogenesis, and8weeks of different intensity endurance training produced adaptive changes, oxidative stress caused by exercise adapted to can not enough make antioxidant enzymes and mitochondrial biogenesis-related genes upregulated at the transcriptional level,but occurs the downregulated phenomenon, which is a kind of adaptive changes produced by skeletal muscle to endurance training.(3) As to PGC-1α/NRF-1/T-fam mRNA and protein levels incompatibility may be related to mitochondrial biogenesis controlled through a variety of ways.