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ESTRADIOL IN FEMALES MAY NEGATE SKELETAL MUSCLE MYOSTATIN
MRNA EXPRESSION AND SERUM MYOSTATIN PROPEPTIDE LEVELS AFTER ECCENTRIC
MUSCLE CONTRACTIONS
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| Darryn
S. Willoughby1,2 and Colin D. Wilborn3 |
1Exercise and Biochemical Nutrition Laboratory, Exercise Nutrition
and Resistance Training Research Unit, Department of Health, Human Performance,
and Recreation; 2Institute for Biomedical Studies, Baylor University, TX,
USA, 3Department of Exercise and Sports Sciences, University of Mary Hardin
Baylor, Belton, TX 76513.
| Received |
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22 August 2006 |
| Accepted |
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26
October 2006 |
| Published |
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15
December 2006 |
©
Journal of Sports Science and Medicine (2006) 5, 672 - 681
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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.
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