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Lower body endurance exercise acutely affects resistance exercise induced transcriptional and translational signalling in the tricpes brachii muscle
Swedish School of Sport and Health Sciences, GIH, Department of Sport and Health Sciences, Åstrand Laboratory of Work Physiology, Eva Blomstrand's research group.ORCID iD: 0000-0003-3747-0148
Swedish School of Sport and Health Sciences, GIH, Department of Sport and Health Sciences, Åstrand Laboratory of Work Physiology, Eva Blomstrand's research group.
Swedish School of Sport and Health Sciences, GIH, Department of Sport and Health Sciences, Åstrand Laboratory of Work Physiology, Björn Ekblom's and Mats Börjesson's research group.
Show others and affiliations
(English)Manuscript (preprint) (Other academic)
Keyword [en]
Concurrent exercise, S6K1 kinase activity, MuRF-1, mTORC1 signaling, muscle protein synthesis
National Category
Medical and Health Sciences
Research subject
Medicine/Technology
Identifiers
URN: urn:nbn:se:gih:diva-4370OAI: oai:DiVA.org:gih-4370DiVA: diva2:908098
Funder
Swedish National Centre for Research in Sports
Note

At the time of Marcus Moberg's dissertation this was a manuscript.

Available from: 2016-03-01 Created: 2016-03-01 Last updated: 2016-04-13Bibliographically approved
In thesis
1. Effects of exercise and amino acid intake on mechanisms regulating protein synthesis and breakdown in human muscle
Open this publication in new window or tab >>Effects of exercise and amino acid intake on mechanisms regulating protein synthesis and breakdown in human muscle
2016 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Skeletal muscle adapts differently to specific modes of exercise, where resistance training results in muscle growth and endurance training induces mitochondrial biogenesis. These are results of molecular events that occur after each exercise session, increasing the expression of specific genes and the rate of both synthesis and breakdown of protein. The rate of protein synthesis is controlled by the mTORC1 signaling pathway, which is potently stimulated by resistance exercise and amino acid, and their combined effect is needed for muscle growth. The essential amino acids (EAA) are responsible for the stimulation of protein synthesis and here leucine has been attributed specific attention, but its particular role among the EAA, and the involvement of the other branched-chain amino acids (BCAA) is unclear. Endurance exercise activates the protein AMPK which, in animal models, has been shown to inhibit mTORC1 signaling and protein synthesis.  Suggesting that concurrent endurance and resistance exercise could restrain muscle growth, but it is unknown if this mechanism is relevant in exercising human muscle. Little is known about the regulation of protein breakdown and although much attention has been given the proteins MuRF-1 and MAFbx which target proteins for degradation, their role requires further investigation. The aim of thesis was to address the mentioned uncertainties by examining how different modes of exercise and amino acids affect mTORC1 signaling, protein synthesis and markers of protein breakdown in human muscle.

In study I, the influence of high intensity endurance exercise on subsequent resistance exercised induced mTORC1 signaling was examined. Despite robust activation of AMPK by the endurance exercise there was no inhibition of mTORC1 signaling or protein synthesis during recovery from resistance exercise. Study II utilized a similar set up, but with the difference that resistance exercise was performed with the triceps. The cycling exercise reduced the resistance exercise stimulated mTORC1 signaling immediately after the exercise, but during the recovery period mTORC1 signaling and protein synthesis was similar between trials. Concurrent exercise induced the mRNA expression of MuRF-1 and that of PGC-1α, the master regulator of mitochondrial biogenesis, in both studies, despite that the exercise modes in study II were separated between legs and arms. In study III, the effect of an EAA supplement with or without leucine, in the stimulation of mTORC1 signaling in connection with resistance exercise was examined. Intake of EAA robustly stimulated mTORC1 signaling after exercise, but this was only minor when leucine was excluded from the supplement. In study IV, subjects were supplied with leucine, BCAA, EAA or placebo in a randomized fashion during four sessions of resistance exercise. Leucine alone stimulated mTORC1 signaling after the exercise, but both the amplitude and extent of stimulation was substantially greater with EAA, an effect that was largely mediated by the BCAA as a group.

In conclusion, endurance exercise prior to resistance exercise using the leg or arm muscles does not affect mTORC1 signaling or protein synthesis during the three hour recovery period from exercise, supporting compatibility between resistance- and endurance exercise induced signaling. Concurrent exercise increases the expression of the proteolytic marker MuRF-1 compared to resistance exercise only, which could indicate both and increased demand of cellular adaptive remodeling or a more direct detrimental proteolytic effect. Leucine is crucial among the EAA in the stimulation of mTORC1 signaling after exercise, its effect is however potentiated by intake of the remaining EAA. As a supplement a mixture of EAA must be regarded preferable, although the effect is largely mediated by the BCAA as a group.  

 

Place, publisher, year, edition, pages
Stockholm: Gymnastik- och idrottshögskolan, 2016. 109 p.
Series
Avhandlingsserie för Gymnastik- och idrottshögskolan, 07
Keyword
Resistance exercise, concurrent exericse, leucine, BCAA, mTORC1 signaling, protein synthesis, MuRF-1, PGC-1alpha
National Category
Sport and Fitness Sciences Cell and Molecular Biology
Research subject
Medicine/Technology
Identifiers
urn:nbn:se:gih:diva-4371 (URN)978-91-980862-6-3 (ISBN)
Public defence
2016-04-01, Aulan, Lidingövägen 1, Stockholm, 09:00 (English)
Opponent
Supervisors
Funder
Swedish National Centre for Research in Sports
Available from: 2016-03-01 Created: 2016-03-01 Last updated: 2016-03-08Bibliographically approved

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