Paper_Bergamasco_et_al_B

Several studies have examined the association between resistance training (RT)-induced muscle hypertrophy and androgen signaling in men. However, only one recent study has reported that estrogen receptor alpha (ERα) protein content positively associates with myofiber hypertrophy following RT. Thus, we investigated the acute and chronic effects of RT on skeletal muscle ERα markers in women and men, and whether these outcomes predicted hypertrophic responses. Given the role of ERα in satellite cell (SC) regulation, we also examined fiber type-specific SC content and SC-related proteins (MyoD, myogenin [Myog], cyclin D1 [CycD1]). Thirty-eight young individuals (19 women) completed 10 weeks of RT. Vastus lateralis biopsies and ultrasound-derived muscle cross-sectional area (mCSA) were obtained at baseline, 24h after first session (acute, biopsy only), and post-intervention. Total ERα, cytoplasmic ERα (cERα), and nuclear ERα (nERα) protein contents were assessed via Western blotting, ERα-DNA binding activity by an oligo-ELISA kit, and myofiber characteristics using immunohistochemistry. Men showed higher baseline total ERα than women. Both sexes showed acute reductions in cERα, nERα, MyoD, Myog, and CycD1. RT increased type I and II SC content and decreased cERα and CycD1, with no changes in ERα-DNA binding. No correlations were observed between ERα markers and hypertrophy in women, whereas in men, an acute reduction in cERα was negatively correlated with chronic mCSA changes. Although we provide further evidence of skeletal muscle ERα markers being responsive to RT, our data suggest that ERα signaling markers may not be a primary driver in RT-induced muscle growth.