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Repeated resistance exercise training induces different changes in mRNA expression of MAFbx and MuRF-1 in human skeletal muscle.
Swedish School of Sport and Health Sciences, GIH, Department of Sport and Health Sciences, Eva Blomstrand's research group.
Swedish School of Sport and Health Sciences, GIH, Department of Sport and Health Sciences, Eva Blomstrand's research group.
Swedish School of Sport and Health Sciences, GIH, Department of Sport and Health Sciences.
Swedish School of Sport and Health Sciences, GIH, Department of Sport and Health Sciences, Björn Ekblom's research group.ORCID iD: 0000-0002-4030-5437
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2008 (English)In: American Journal of Physiology. Endocrinology and Metabolism, ISSN 0193-1849, E-ISSN 1522-1555, Vol. 294, no 1, E43-51 p.Article in journal (Refereed) Published
Abstract [en]

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.

Place, publisher, year, edition, pages
2008. Vol. 294, no 1, E43-51 p.
National Category
Medical and Health Sciences
Identifiers
URN: urn:nbn:se:gih:diva-960DOI: 10.1152/ajpendo.00504.2007PubMedID: 17971512OAI: oai:DiVA.org:gih-960DiVA: diva2:236642
Available from: 2009-09-24 Created: 2009-09-21 Last updated: 2017-03-31Bibliographically approved
In thesis
1. Intracellular signaling in human skeletal muscle following different modes of exercise
Open this publication in new window or tab >>Intracellular signaling in human skeletal muscle following different modes of exercise
2010 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Resistance and endurance exercise when performed regularly will cause specific adaptations in human skeletal muscle. Resistance exercise is known to increase strength and muscle mass while endurance training increases vascularisation and mitochondrial density which results in enhanced oxidative capacity. To understand how these adaptations occur, it is important to examine the molecular signaling events in muscle. The Akt-mTOR pathway has been shown to have an important function in the stimulation of protein synthesis. This pathway is stimulated following resistance exercise in human muscle. During the work included in this thesis it has become clear that endurance exercise also stimulates Akt-mTOR signaling in human skeletal muscle. Study (I) revealed an increased phosphorylation of mTOR, Akt and GSK3 and a marked decrease in eEF2 phosphorylation indicating a stimulatory response on elongation and initiation of protein synthesis in the early recovery phase. Furthermore, as shown in study (II), this stimulatory response is followed by an increase in the fractional synthetic rate (FSR), which was progressively increased when measured up to 3 h following endurance exercise. It is usually recommended that resistance exercise is performed 2-3 times per week. In study (III), markers for anabolic (Akt, mTOR, p70S6k, rpS6, eEF2 and GSK-3β) as well as catabolic (MAFbx and MuRF-1) processes were investigated following two sessions of resistance exercise separated by 48 hours. From this study it appears that anabolic signaling is slightly enhanced following the second exercise session, and furthermore, the changes in gene expression related to muscle protein degradation (MAFbx and MuRF-1) is attenuated during the second exercise session. Endurance exercise can compromise the adaptive response of strength training. On the other hand, there is some evidence suggesting that combining endurance training with resistance exercise may have beneficial effects on endurance exercise performance. The final study was designed to evaluate whether resistance exercise can enhance the muscle adaptive response to endurance exercise with respect to molecular signaling related to increased protein synthesis and specific markers for mitochondrial biogenesis. An enhanced signaling response was actually found in the combined exercise protocol. Specifically, expression of genes related to increased mitochondrial biogenesis and oxidative metabolism (PGC-1α, PRC and PDK-4 mRNA) as well markers for anabolic signaling (mTOR, p70S6k), was enhanced when endurance exercise was followed by a session of heavy resistance exercise. This data support the notion that including resistance exercise in endurance training may be beneficial. In summary, mixed muscle FSR is gradually increased following endurance exercise when measured during the first 3 h of recovery and this increase is accompanied by stimulation of mTOR signaling. Resistance exercise enhances effects on anabolic signaling and attenuates expression of genes involved in muscle protein breakdown and inhibition of muscle growth during a second exercise session performed two days after the first. Finally, combining endurance and heavy resistance exercise can enhance acute adaptive responses and indicates that combined exercise may be superior to endurance exercise alone.

Place, publisher, year, edition, pages
Stockholm: Karolinska institutet, 2010
National Category
Medical and Health Sciences
Research subject
Medicine/Technology
Identifiers
urn:nbn:se:gih:diva-2459 (URN)978-91-7457-144-8 (ISBN)
Public defence
2010-12-03, Aulan, GIH, Lidingövägen 1, Stockholm, 09:00
Opponent
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Available from: 2012-11-01 Created: 2012-11-01 Last updated: 2012-12-18Bibliographically approved

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Mascher, HenrikTannerstedt, JörgenEkblom, BjörnBlomstrand, Eva
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