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RESEARCH PRODUCT

Postexercise myostatin and activin IIb mRNA levels: effects of strength training.

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ABSTRACTHULMI, J. J., J. P. AHTIAINEN, T. KAASALAINEN, E. PO¨LLA¨NEN, K. HA¨KKINEN, M. ALEN, H. SELA¨NNE, V. KOVANEN,and A. A. MERO. Postexercise Myostatin and Activin IIb mRNA Levels: Effects of Strength Training. Med. Sci. Sports Exerc., Vol.39, No. 2, pp. 289–297, 2007. Purpose: Muscle hypertrophy is likely to result from the cumulative effects of repeated bouts ofresistance exercise (RE) on postexercise molecular responses. Therefore, we determined muscle growth- and regeneration-relatedmRNA expression in response to a single RE bout both before and after a strength-training (ST) period. By means of this novellongitudinal setting, we examined whether postexercise gene expression at the transcriptional level is different in the trained anduntrained state. Methods: Eleven untrained healthy older men and 11 controls (age 62.3 T 6.3 yr) volunteered as subjects. Musclebiopsies from the vastus lateralis muscle were taken at rest and 1 and 48 h after five sets of 10-repetition leg press RE both before andafter 21 wk of supervised ST. Results: Myostatin and myogenin mRNA expression, determined by real-time RT-PCR, increased (P G0.05) after ST. Conversely, the single RE bout decreased myostatin mRNA after ST, with the decrease showing a negative correlation(r = j0.65, P G 0.05) with the long-term increase in myostatin during ST. Furthermore, RE before ST increased myogenin mRNA(P G 0.05) and tended to increase after ST (P = 0.08). Myostatin receptor activin IIb mRNA levels were decreased at 1 h after RE inthe pre-ST condition (P = 0.05) and also tended to decrease in the post-ST condition (P = 0.07). RE-induced downregulation inmyostatin mRNA correlated with the ST-induced increase in total body muscle mass (r = j0.82, P = 0.002). Conclusions: A singlebout of RE in older men can downregulate the expression of myostatin receptor activin IIb mRNA. ST influences the response ofmyostatin to RE, as short-term RE-induced downregulation of myostatin was observed only after ST. The results also indicate thatRE-induced alterations in myostatin mRNA expression may have a role in ST-induced muscle hypertrophy. Key Words: GENEEXPRESSION, RESISTANCE EXERCISE, MUSCLE HYPERTROPHY, MYOGENIN, MYOD