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This Article Full Text Full Text (PDF) All Versions of this Article: 294/1/E43    most recent 00504.2007v1 Alert me when this article is cited Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Similar articles in ISI Web of Science Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via Google Scholar Google Scholar Articles by Mascher, H. Articles by Blomstrand, E. Search for Related Content PubMed PubMed Citation Articles by Mascher, H. Articles by Blomstrand, E.

Repeated resistance exercise training induces different changes in mRNA expression of MAFbx and MuRF-1 in human skeletal muscle

¹Åstrand Laboratory, Swedish School of Sport and Health Sciences; ²Department of Physiology and Pharmacology; and ³Department of Laboratory Medicine, Division of Clinical Physiology, Karolinska University Hospital, Karolinska Institutet, Stockholm, Sweden

Submitted 1 August 2007 ; accepted in final form 18 October 2007

The gain in muscle mass as a result of resistance training is dependent on changes in both anabolic and catabolic reactions. A frequency of two to three exercise sessions per week is considered optimal for muscle gain in untrained individuals. Our hypothesis was that a second exercise session would enlarge the anabolic response and/or decrease the catabolic response. Eight male subjects performed resistance exercise on two occasions separated by 2 days. Muscle biopsies were taken from the vastus lateralis before and 15 min, 1 h, and 2 h after exercise. Exercise led to severalfold increases in phosphorylation of mTOR at Ser²⁴⁴⁸, p70 S6 kinase (p70^S6k) at Ser⁴²⁴/Thr⁴²¹ and Thr³⁸⁹, and ribosomal protein S6, which persisted for up to 2 h of recovery on both occasions. There was a tendency toward a larger effect of the second exercise on p70^S6k and S6, but the difference did not reach statistical significance. The mRNA expression of MuRF-1, which increased after exercise, was 30% lower after the second exercise session than after the first one. MAFbx expression was not altered after exercise but downregulated 30% 48 h later, whereas myostatin expression was reduced by 45% after the first exercise and remained low until after the second exercise session. The results indicate that 1) changes in expression of genes involved in protein degradation are attenuated as a response to repetitive resistance training with minor additional increases in enzymes regulating protein synthesis and 2) the two ubiquitin ligases, MuRF-1 and MAFbx, are differently affected by the exercise as well as by repeated exercise.

atrogin-1; protein translation; p70 S6 kinase