Abstract
Myostatin (MSTN) inhibits skeletal muscle growth and it may also inhibit training-induced muscle growth. MSTN acts by binding to the activin IIb receptor (ActIIb) but its binding can be inhibited by follistatin-related gene (FLRG) protein. Decreased MSTN mRNA expression has been shown in untrained subjects 24h after a single resistance exercise (RE). This molecular response may be important in strength training (ST) mediated hypertrophy together with possible changes in ActIIb and FLRG expression. PURPOSE: To determine MSTN, ActIIb and FLRG responses at mRNA level to a single RE before and after six months of ST. METHODS: Nine (61.0±5.5 yrs) previously untrained healthy men participated in the study. RE was performed one wk before and one wk after ST. The RE included 5 sets of 10RM bilateral leg presses. Muscle biopsies were taken from the vastus lateralis 0.5h before (pre), and 1h (post 1h) as well as 48h (post 48h) after the RE. MSTN, ActIIb and FLRG mRNA expression were determined by Taqman probe-based realtime RT-PCR. RESULTS: The basal (pre) MSTN mRNA levels were significantly increased during the ST (p<0.05) (Fig 1). After ST the MSTN post 48h levels were significantly lower compared to the corresponding pre RE levels (p<0.01). The ActIIb mRNA levels decreased before and after ST due to RE (post 1h p<0.05; post 48h p<0.10). No changes were observed in FLRG mRNA.Fig 1: Resistance exercise-induced myostatin mRNA expression before and after ST.CONCLUSION: The present study showed that ST increased basal MSTN levels, which has been shown previously in some but not all studies. The novel finding was that both MSTN and its receptor ActIIb levels decreased due to RE. However, the decrease in MSTN was observed only in post-training RE. Both of these decreases probably decrease the catabolic action of MSTN. The present study indicates that resistance exercise decreases MSTN and ActIIb expression, at least after training. Both of these anabolic responses may be important in the skeletal muscle hypertrophy process, and they should be examined in the future. Supported by the Finnish Ministry of Education.
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