Journal of Sports Science and Medicine
Journal of Sports Science and Medicine
ISSN: 1303 - 2968   
Ios-APP Journal of Sports Science and Medicine
Androit-APP Journal of Sports Science and Medicine
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©Journal of Sports Science and Medicine (2006) 05, 672 - 681

Research article
Estradiol In Females May Negate Skeletal Muscle Myostatin Mrna Expression And Serum Myostatin Propeptide Levels After Eccentric Muscle Contractions
Darryn S. Willoughby1,2, , Colin D. Wilborn3
Author Information
1 Exercise and Biochemical Nutrition Laboratory, Exercise Nutrition and Resistance Training Research Unit, Department of Health, Human Performance and Recreation,
2 Institute for Biomedical Studies, Baylor University, TX, USA
3 Department of Exercise and Sports Sciences, University of Mary Hardin Baylor, Belton, TX 76513

Darryn S. Willoughby
✉ Department of Health, Human Performance, and Recreation, Baylor University, P.O. Box 97313, Waco, TX 76798, USA.
Email: Darryn_Willoughby@baylor.edu
Publish Date
Received: 22-08-2006
Accepted: 26-10-2006
Published (online): 15-12-2006
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ABSTRACT

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-β 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.

Key words: Estrogen, muscle damage, eccentric contractions, myostatin


           Key Points
  • The pre-exercise levels of myostatin mRNA and propeptide were not significantly different between genders, and even though the total body mass and fat-free mass of males were significantly greater than females, neither was correlated to myostatin mRNA or LAP/propeptide.
  • Myostatin mRNA expression in females is less than in males 24 h after a single bout of eccentric exercise.
  • Myostatin LAP/propeptide levels in females are lower in females than in males 24 h after a single bout of eccentric exercise, thereby suggesting a gender-specific mechanism in which females may be less responsive to eccentric exercise than males.
  • Myostatin mRNA expression in females is attenuated, possibly due to inhibition in myostatin signaling, and appears to be more related to the presence of a higher level of circulating E2 rather than body composition.
  • Due to their higher level of E2, females seem to be less susceptible to the mechanism by which eccentric exercise apparently up-regulates myostatin mRNA expression in males.
 
 
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