PURPOSE. Potential effects of hormone therapy (HT) on skeletal muscle are not well understood. We sought to evaluate changes in gene expression of myostatin-related factors in postmenopausal women taking HT and not taking HT following eccentric resistance exercise.
METHODS. Fourteen postmenopausal women participated including 6 control women not using HT (59 ± 4 yrs, 63 ± 17 kg) and 8 women using HT (59 ± 4 yrs, 89 ± 24 kg). Participants performed 10 sets of 10 maximal eccentric repetitions of single-leg extension on a Cybex dynamometer. Muscle biopsies from the vastus lateralis were obtained from the exercised leg at baseline and 4 hours after the exercise bout. Gene expression was determined using RT-PCR for myostatin, ActRIIb (activin receptor IIb), follistatin, FLRG (follistatin-related gene), FSTL3 (follistatin-like-3) and GASP-1 (GDF-serum associated protein-1).
RESULTS. At rest, the HT group expressed lower levels of myostatin and ActRIIb and higher levels of follistatin, FLRG, FSTL3 and GASP-1 (P < 0.05). In response to eccentric exercise, myostatin and ActRIIb significantly decreased (P < 0.05) and follistatin, FLRG, FSTL3 and GASP-1 significantly increased in both groups (P < 0.05). Significantly greater changes in gene expression of all genes occurred in the HT group than in the control group after exercise (P < 0.05).
CONCLUSIONS. These data suggest that postmenopausal women using HT express greater myostatin-related gene expression, which may reflect a mechanism by which estrogen influences the preservation of muscle mass. Further, postmenopausal women using HT experienced a profoundly greater myostatin-related response to maximal eccentric exercise.
Funding: NCRR GCRC M0I RR000043