Estradiol in females may negate skeletal muscle myostatin mRNA expression and serum myostatin propeptide levels after eccentric muscle contractions

Eccentric contractions produce a significant degree of inflammation and muscle injury that may increase the expression of myostatin. Due to its anti-oxidant and anti-flammatory effects, circulating 17-beta estradiol (E2) may attenuate myostatin expression. Eight males and eight females performed 7 sets of 10 reps of eccentric contractions of the knee extensors at 150% 1-RM. Each female performed the eccentric exercise bout on a day that fell within her mid-luteal phase (d 21- 23 of her 28-d cycle). Blood and muscle samples were obtained before and 6 and 24 h after exercise, while additional blood samples were obtained at 48 and 72 h after exercise. Serum E2 and myostatin LAP/propeptide (LAP/pro) levels were determined with ELISA, and myostatin mRNA expression determined using RT-PCR. Data were analyzed with two-way ANOVA and bivariate correlations ( p < 0.05). Females had greater levels of serum E2 throughout the 72-h sampling period ( p < 0.05). While males had greater body mass and fat-free mass, neither was correlated to the pre-exercise levels of myostatin mRNA and LAP/pro for either gender ( p > 0.05). Compared to pre-exercise, males had significant increases ( p < 0.05) in LAP/propetide and mRNA of 78% and 28%, respectively, at 24 h post-exercise, whereas females underwent respective decreases of 10% and 21%. E2 and LAP/propeptide were correlated at 6 h (r = - 0.804, p = 0.016) and 24 h post-exercise ( r = - 0.841, p = 0.009) in males, whereas in females E2 levels were correlated to myostatin mRNA at 6 h ( r = 0.739, p = 0.036) and 24 h ( r = 0.813, p = 0.014) post-exercise and LAP/ propeptide at 6 h ( r = 0.713, p = 0.047) and 24 h ( r = 0.735, p = 0.038). In females, myostatin mRNA expression and serum LAP/ propeptide levels do not appear to be significantly up-regulated following eccentric exercise, and may be due to higher levels of circulating E2.