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Enhanced rates of muscle protein synthesis and elevated mTOR signalling following endurance exercise in human subjects.
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, Björn Ekblom's research group.ORCID iD: 0000-0002-4030-5437
Swedish School of Sport and Health Sciences, GIH, Department of Sport and Health Sciences, Eva Blomstrand's research group.ORCID iD: 0000-0002-6537-042X
2011 (English)In: Acta Physiologica, ISSN 1748-1708, E-ISSN 1748-1716, Vol. 202, no 2, 175-84 p.Article in journal (Refereed) Published
Abstract [en]

AIM: The major aim of this study was to determine the fractional rate of protein synthesis (FSR) during the early period of recovery after intensive aerobic exercise in the absence of nutritional supplementation.

METHODS: Sixteen male subjects performed one-legged cycling exercise for 1 h at approx. 65-70% of their one-legged maximal oxygen uptake. Using the stable isotope technique, the FSR in the vastus lateralis of both legs were determined during two periods, 0-90 min (n = 8) and 90-180 min (n = 8) after exercise. Biopsies were taken from both exercising and resting muscle before exercise, immediately after and following 90 or 180 min of recovery.

RESULTS: During the initial 90 min of recovery, FSR in the exercising muscle tended to be higher than in the resting muscle (1.57 ± 0.12 vs. 1.44 ± 0.07% 24 h(-1); P = 0.1) and was significantly higher during the period 90-180 min after exercise (1.74 ± 0.14 vs. 1.43 ± 0.12% 24 h(-1) ; P < 0.05). Exercise induced a 60% increase (P < 0.05) in phosphorylation of mTOR and a fivefold increase (P < 0.05) in Thr(389) phosphorylation of p70S6 kinase as well as a 30% reduction (P < 0.05) in phosphorylation of eEF2. Phosphorylation of AMP-activated protein kinase was enhanced by 40% (P < 0.05) after exercise, but no significant effect on phosphorylation of Akt, or eIF2Bε was observed immediately after exercise.

CONCLUSION: These findings indicate that during the first 3 h of recovery after intensive endurance exercise FSR gradually increases. Moreover, a stimulation of the mTOR-signalling pathway may be at least partially responsible for this elevated protein synthesis.

Place, publisher, year, edition, pages
2011. Vol. 202, no 2, 175-84 p.
National Category
Medical and Health Sciences
Research subject
Medicine/Technology
Identifiers
URN: urn:nbn:se:gih:diva-1916DOI: 10.1111/j.1748-1716.2011.02274.xPubMedID: 21385328OAI: oai:DiVA.org:gih-1916DiVA: diva2:448176
Note

At the time of Henrik Mascher's dissertation the article was submitted.

Available from: 2011-10-14 Created: 2011-10-14 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
Supervisors
Available from: 2012-11-01 Created: 2012-11-01 Last updated: 2012-12-18Bibliographically approved

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