Resistance Exercise-Induced Hormonal Response Promotes Satellite Cell Proliferation in Untrained Men

Abstract

Evidence suggests that resistance exercise (RE)-induced transient release of anabolic hormones can be beneficial for muscle adaptation (e.g. muscle size, strength); however, no prior research appears to have investigated the effect of the RE-induced hormonal response on satellite cell (SC) proliferation and differentiation, an important step in any such muscle adaptations. PURPOSE: To determine the effect of transient resistance exercise (RE)-induced hormonal changes on satellite cell myogenic state following eccentric exercise. METHODS: Untrained men (n=10, 22±3y) and women (n=9, 21±4y) completed 2 sessions of 80 unilateral maximal eccentric knee extensions followed by either an upper body RE protocol (EXE) or a 20-min rest (CON). Muscle samples were collected and analyzed for protein content of Pax7, MyoD, myogenin, cyclin D1, and p21 before exercise (PRE), and 12 hours (+12h) and 24 hours after the session (+24h). Serum testosterone, growth hormone, cortisol, and myoglobin concentrations were measured at PRE, immediately after eccentric knee extension (IMD), immediately after (IP), 15, 30, and 60 min after the session. RESULTS: Testosterone was significantly (p<0.05) higher immediately after the session in EXE (6.34 ± 0.48 ng·ml-1) than CON (4.87 ± 0.26 ng·ml-1) for men. A significant time x gender x condition interaction was found for MyoD with 20.1 ± 10.8-fold increase for EXE in men and 21.9 ± 7.6-fold increase for CON in women at +12h compared to PRE. A significant time x condition interaction was found for Pax7 with 0.8 ± 0.1-fold decrease for EXE and 1.6 ± 0.3-fold increase for CON at +24h compared to PRE. A significant time effect was found for myogenin, p21, and cyclin D1. Myogenin (+12h: 5.9 ± 1.5-fold; +24h: 5.0 ± 1.1-fold) and p21 (+12h: 25.4 ± 4.5-fold; +24h: 12.4 ± 1.9-fold) were increased at +12h and +24h and Cyclin D1 was 6.6 ± 1.9-fold increased at +12h compared to PRE. CONCLUSION: These results suggest that the RE-induced hormonal response can be important to promote SC proliferation for men but not women. In addition, markers of SC differentiation appeared to be unaffected by the hormonal response but were increased in response to the knee eccentric exercise protocol. Supported in part by a grant from the National Strength and Conditioning Association Foundation