The use of hormone replacement therapy (HRT) is a potential treatment to relieve symptoms of menopause in postmenopausal women; however, the effects on skeletal muscle are unclear. Specifically, it is unknown if HRT enhances estrogen receptor (ER) transcriptional activation in skeletal muscle at rest and after resistance exercise.
Purpose: To evaluate changes in the messenger RNA (mRNA) expression of ER coregulators (steroid receptor coactivator-1 (SRC-1) and silencing mediator of retinoid and thyroid receptors (SMRT)) in postmenopausal women after a maximal eccentric exercise bout.
Methods: Fourteen postmenopausal women were divided into two groups: Control, women not using HRT (n = 6, 59.2 ± 4.2 yr, 63.1 ± 17.4 kg); or HRT, women using traditional HRT (n = 8, 58.5 ± 3.7 yr, 89.5 ± 23.7 kg). Participants performed 10 sets of 10 maximal eccentric repetitions of single-leg extension on the Cybex dynamometer at 60°·s−1 with 20-s rest periods between sets. Muscle biopsies of the vastus lateralis were obtained from the exercised leg at baseline and 4 h after the exercise bout. mRNA expression was determined using real-time polymerase chain reaction for SRC-1 and SMRT.
Results: mRNA expression of SRC-1 significantly increased (P ≤ 0.01; 2.4- to 5.2-fold change) and mRNA expression of SMRT significantly decreased (P ≤ 0.01; −1.3- to −4.3-fold change) after the exercise bout in both groups. We observed significantly greater changes in mRNA expression of SRC-1 and SMRT (P ≤ 0.01) in the HRT group compared with controls after exercise.
Conclusions: A single bout of maximal eccentric exercise enhances ER transcriptional activity with a greater response present in postmenopausal women using HRT.
1Division of Biokinesiology and Physical Therapy, Clinical Exercise Research Center, University of Southern California, Los Angeles, CA; and 2Department of Biochemistry and Molecular Biology, USC/Norris Comprehensive Cancer Center, University of Southern California, Los Angeles, CA; 3Keck School of Medicine, University of Southern California, Los Angeles, CA
Address for correspondence: E. Todd Schroeder, Ph.D., 1540 E Alcazar St CHP-155, Los Angeles, CA 90033; E-mail: firstname.lastname@example.org.
Submitted for publication March 2009.
Accepted for publication July 2009.