Abstract
The aim of this study was to investigate differences in skeletal muscle gene expression of highly trained endurance and strength athletes in comparison to untrained individuals at rest and in response to either an acute bout of endurance or strength exercise. Endurance (ET, n = 8, VO2max 67 ± 9 mL/kg/min) and strength athletes (ST, n = 8, 5.8 ± 3.0 training years) as well as untrained controls (E-UT and S-UT, each n = 8) performed an acute endurance or strength exercise test. One day before testing (Pre), 30 min (30′Post) and 3 h (180′Post) afterwards, a skeletal muscle biopsy was obtained from the m. vastus lateralis. Skeletal muscle mRNA was isolated and analyzed by Affymetrix-microarray technology. Pathway analyses were performed to evaluate the effects of training status (trained vs. untrained) and exercise mode-specific (ET vs. ST) transcriptional responses. Differences in global skeletal muscle gene expression between trained and untrained were smaller compared to differences in exercise mode. Maximum differences between ET and ST were found between Pre and 180′Post. Pathway analyses showed increased expression of exercise-related genes, such as nuclear transcription factors (NR4A family), metabolism and vascularization (PGC1-α and VEGF-A), and muscle growth/structure (myostatin, IRS1/2 and HIF1-α. The most upregulated genes in response to acute endurance or strength exercise were the NR4A genes (NR4A1, NR4A2, NR4A3). The mode of acute exercise had a significant effect on transcriptional regulation Pre vs. 180′Post. In contrast, the effect of training status on human skeletal muscle gene expression profiles was negligible compared to strength or endurance specialization. The highest variability in gene expression, especially for the NR4A-family, was observed in trained individuals at 180′Post. Assessment of these receptors might be suitable to obtain a deeper understanding of skeletal muscle adaptive processes to develop optimized training strategies.
Highlights
What makes the ‘perfect’ athlete? The chance of an individual possessing a ‘perfect’ genotype for either endurance or strength sports is lower than 1 in 20 million
Lortie et al showed that the individual differences in the response to a standardized 20-week aerobic training ranged from 5–88% [4], suggesting that particular genotypes might be more responsive to training than others
We examined highly endurance- and strength-trained athletes and compared them to untrained individuals to investigate skeletal muscle gene expression (1) at rest prior to exercise, (Pre) representing the basal expression level; and (2) 30 min (30 Post) and 180 min (180 Post) after an acute bout of either endurance or strength exercise to determine exercise mode-specific transcriptional regulation processes
Summary
The chance of an individual possessing a ‘perfect’ genotype for either endurance or strength sports is lower than 1 in 20 million. The genotype dependency of the adaptive response to exercise training and the associated exercise performance is well documented. A twin study with mono- and dizygotic twins, for example, reported an heritability contribution to VO2max of 80–90% [2]. This finding was confirmed by the HERITAGE family study, determining the role of genotype for cardiovascular, metabolic, and hormonal responses to aerobic exercise training [3]. A considerable variability of individual responses to a standardized endurance or strength training program has been reported [4,5,6]. Lortie et al showed that the individual differences in the response to a standardized 20-week aerobic training ranged from 5–88% [4], suggesting that particular genotypes might be more responsive to training than others
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