Irisin and FNDC5: effects of 12-week strength training, and relations to muscle phenotype and body mass composition in untrained women
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- Ellefsen, S., Vikmoen, O., Slettaløkken, G. et al. Eur J Appl Physiol (2014) 114: 1875. doi:10.1007/s00421-014-2922-x
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To investigate the effects of strength training on abundances of irisin-related biomarkers in skeletal muscle and blood of untrained young women, and their associations with body mass composition, muscle phenotype and levels of thyroid hormones.
Eighteen untrained women performed 12 weeks of progressive whole-body heavy strength training, with measurement of strength, body composition, expression of irisin-related genes (FNDC5 and PGC1α) in two different skeletal muscles, and levels of serum-irisin and -thyroid hormones, before and after the training intervention.
The strength training intervention did not result in changes in serum-irisin or muscle FNDC5 expression, despite considerable effects on strength, lean body mass (LBM) and skeletal muscle phenotype. Our data indicate that training affects irisin biology in a LBM-dependent manner. However, no association was found between steady-state serum-irisin or training-associated changes in serum-irisin and alterations in body composition. FNDC5 expression was higher in m.Biceps brachii than in m.Vastus lateralis, with individual expression levels being closely correlated, suggesting a systemic mode of transcriptional regulation. In pre-biopsies, FNDC5 expression was correlated with proportions of aerobic muscle fibers, a relationship that disappeared in post-biopsies. No association was found between serum-thyroid hormones and FNDC5 expression or serum-irisin.
No evidence was found for an effect of strength training on irisin biology in untrained women, though indications were found for a complex interrelationship between irisin, body mass composition and muscle phenotype. FNDC5 expression was closely associated with muscle fiber composition in untrained muscle.
KeywordsIrisin FNDC5 Lean body mass Fat mass Muscle fiber Skeletal muscle Strength training Thyroid hormones Exercise Myosin heavy chain MHC MyHC mRNA Real-time RT-PCR qRT-PCR Metabolism
- 18S rRNA
18S ribosomal RNA
musculus Biceps brachii
Dual-energy X-ray absorptiometry
Fibronectin type III domain-containing protein 5
Lean body mass
Myosin heavy chain
Peroxisome proliferator-activated receptor gamma coactivator 1-alpha
Polymerase (RNA) II (DNA directed) polypeptide A
Peptidylprolyl isomerase A (cyclophilin A)
Quantitative reverse transcriptase-polymerase chain reaction
Ribosomal protein L32 (RPL32)
Serum concentrations of irisin
TATA box binding protein
musculus Vastus lateralis