[The changes of p-Akt/MuRF1/FoxO1 proteins expressions in the conditions of training and immobilization in rats' gastrocnemius muscle].

This study was aimed to investigate the changes of muscle protein synthesis and degradation under different movement conditions, so as to provide theoretical basis for muscle atrophy mechanism. Sprague Dawley (SD) rats were randomly divided into control, endurance training (treadmill training), hind limb overhanging and eccentric training (treadmill training, angle -16º) groups. The gastrocnemius muscles of rats were taken and weighed. The muscle was sectioned, and HE staining was employed to determine the cell's cross-sectional area. Protein expression of p-Akt was measured by immunohistochemistry; and the expressions of MuRF1 and FoxO1 were determined by Western blot. The results showed that, compared with control group, hind limb overhanging and eccentric training groups exhibited decreased muscle weight and cross-sectional area, but endurance training group did not show any changes. The expressions of p-Akt in endurance and eccentric training groups, not in hind limb overhanging group, were significantly higher than that in control group. Compared with that of control, MuRF1 protein remained unchanged in endurance training groups, but was increased in eccentric training and hind limb overhanging groups; FoxO1 protein was decreased in endurance training group, but was increased in eccentric training and hind limb overhanging groups. These results indicate that movement (endurance and eccentric training) can activate Akt expression, but does not increase muscle weight, whereas eccentric training and hind limb overhanging can increase the expressions of MuRF1 and FoxO1, and induce amyotrophy, suggesting MuRF1 and FoxO1 are major determinant factors in muscle atrophy.

[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.