[Effects of resistance training on mitochondrial function in skeletal muscle of aging rats]

Objective: To investigate the effects of resistance exercise on mitochondrial function in skeletal muscle of aging rats. Methods: Forty male Sprague-Dawley rats were randomly assigned to 4 groups, 2-month sedentary control group (C1; n=10), 2-month with resistance training group (R1; n=10), 6-month sedentary control group (C2; n=10), 6-month with resistance training group (R2; n =10 ). Rats in R1 and R2 groups were arranged for resistance training for 8 weeks. This program consisted of interval running on a treadmill, speed 15 m·min^-1, 35° incline, duration 15 s, interval 30 s, 4 times/group, 3 groups/cycle, 2 cycles per day, 6 days per week, a total of 8 weeks. The expressions of mitochondrial fusion protein 2(Mfn2) and dynamin-related protein 1(DRP1) in rat quadriceps were detected by Western blot, and the changes of mitochondrial membrane potential (ΔΨm), reactive oxygen species (ROS) and Ca²⁺ concentration were measured by flow cytometry. Results: ①Compared with C1 group, the expression of DRP1 protein in R1 group was increased (P＜0. 01), and the Mfn2 protein in R1 group had no significant difference, both DRP1 and Mfn2 protein in C2 group were decreased (P＜0. 01);compared with C2 group, the DRP1 and Mfn2 protein in R2 group were similarly increased (P＜0. 01, P＜0. 05);compared with R1 group, the DRP1 and Mfn2 protein in R2 group were both decreased (P＜0. 01). ② Compared with C1 group, the Ca²⁺ content of R1 group was decreased (P＜0. 01) and the Ca²⁺ content of C2 group was increased (P＜0. 01);Compared with C2 group, the content of Ca²⁺ in R2 group was decreased (P＜0. 01);compared with R1 group, the Ca²⁺ content in R2 group was increased (P＜0. 01). ③ Compared with C1 group, the ROS content in R1 group was increased, but there was no significant difference, while the ROS content in C2 group was increased (P＜0. 01);compared with C2 group, ROS content in R2 group was decreased (P＜0. 01); compared with R1 group, the ROS content in R2 group was increased (P＜0. 01). ④ Compared with group C1, the levels of ΔΨm in C2 group was decreased (P＜0. 01);Compared with C2 group, The ΔΨm of R2 group was increased(P＜0. 01); Compared with group R1, the ΔΨm of R2 group was decreased, but there was no statistical difference. Conclusion: During the aging process of rats, mitochondria of quadriceps femoral muscle showed Ca²⁺ accumulation, increased reactive oxygen species, decreased mitochondrial membrane potential, decreased fusion protein and other phenomena, and resistance training could effectively improve these changes.