title: Repeated resistance exercise training induces different changes in mRNA expression of MAFbx and MuRF-1 in human skeletal muscle.
abstract: 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 (p70S6k) 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 p70S6k 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.
authors.affiliation: Astrand Laboratory, Swedish School of Sport and Health Sciences, Karolinska University Hospital, Karolinska Institutet, Box 5626, Stockholm, S-114 86, Sweden.
authors.forename: Henrik
authors.initials: H
authors.lastname: Mascher
authors.forename: Jörgen
authors.initials: J
authors.lastname: Tannerstedt
authors.forename: Thibault
authors.initials: T
authors.lastname: Brink-Elfegoun
authors.forename: Björn
authors.initials: B
authors.lastname: Ekblom
authors.forename: Thomas
authors.initials: T
authors.lastname: Gustafsson
authors.forename: Eva
authors.initials: E
authors.lastname: Blomstrand
mesh_terms: D000328:Adult; D001786:Blood Glucose / Q000378:metabolism; D015444:Exercise / Q000502:physiology*; D015870:Gene Expression / Q000502:physiology; D006801:Humans; D019344:Lactic Acid / Q000097:blood; D008297:Male; D009124:Muscle Proteins / Q000235:genetics* / Q000378:metabolism; D053580:Muscle Strength / Q000502:physiology*; D018482:Muscle, Skeletal / Q000502:physiology*; D010766:Phosphorylation; D011494:Protein Kinases / Q000378:metabolism; D051057:Proto-Oncogene Proteins c-akt / Q000378:metabolism; D012333:RNA, Messenger / Q000378:metabolism; D038762:Ribosomal Protein S6 Kinases, 70-kDa / Q000378:metabolism; D044843:SKP Cullin F-Box Protein Ligases / Q000235:genetics* / Q000378:metabolism; D015398:Signal Transduction / Q000502:physiology; D058570:TOR Serine-Threonine Kinases; D000070584:Tripartite Motif Proteins; D044767:Ubiquitin-Protein Ligases / Q000235:genetics* / Q000378:metabolism
chemical_list: D001786:Blood Glucose; D009124:Muscle Proteins; D012333:RNA, Messenger; D000070584:Tripartite Motif Proteins; D019344:Lactic Acid; C440907:FBXO32 protein, human; D044843:SKP Cullin F-Box Protein Ligases; C440908:TRIM63 protein, human; D044767:Ubiquitin-Protein Ligases; D011494:Protein Kinases; C546842:MTOR protein, human; D051057:Proto-Oncogene Proteins c-akt; D038762:Ribosomal Protein S6 Kinases, 70-kDa; D058570:TOR Serine-Threonine Kinases