Hormone Replacement Therapy and Messenger RNA Expression of Estrogen Receptor Coregulators after Exercise in Postmenopausal Women

Abstract

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. 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. 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 degrees .s 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. mRNA expression of SRC-1 significantly increased (P < or = 0.01; 2.4- to 5.2-fold change) and mRNA expression of SMRT significantly decreased (P < or = 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 < or = 0.01) in the HRT group compared with controls after exercise. A single bout of maximal eccentric exercise enhances ER transcriptional activity with a greater response present in postmenopausal women using HRT.