The goal of this study was to identify unknown transcription start sites of the PPARGC1A (PGC-1a) gene in human skeletal muscle and investigate the promoter-specific regulation of PGC-1a gene expression in human skeletal muscle. Ten amateur endurance-trained athletes performed high-and low-intensity exercise sessions (70 min, 70% or 50% _ V o 2max ). High-throughput RNA sequencing and exon-exon junction mapping were applied to analyse muscle samples obtained at rest and after exercise. PGC-1a promoter-specific expression and activation of regulators of PGC-1a gene expression (AMPK, p38 MAPK, CaMKII, PKA and CREB1) after exercise were evaluated using qPCR and western blot. Our study has demonstrated that during post-exercise recovery, human skeletal muscle expresses the PGC-1a gene via two promoters only. As previously described, the additional exon 7a that contains a stop codon was found in all samples. Importantly, only minor levels of other splice site variants were found (and not in all samples). Constitutive expression PGC-1a gene occurs via the canonical promoter, independent of exercise intensity and exercise-induced increase of AMPK Thr172 phosphorylation level. Expression of PGC-1a gene via the alternative promoter is increased of two orders after exercise. This post-exercise expression is highly dependent on the intensity of exercise. There is an apparent association between expression via the alternative promoter and activation of CREB1.

We investigated acute exercise-induced gene expression in skeletal muscle adapted to aerobic training. Vastus lateralis muscle samples were taken in ten endurance-trained males prior to, and just after, 4 h, and 8 h after acute cycling sessions with different intensities, 70% and 50% V˙O2max. High-throughput RNA sequencing was applied in samples from two subjects to evaluate differentially expressed genes after intensive exercise (70% V˙O2max), and then the changes in expression for selected genes were validated by quantitative PCR (qPCR). To define exercise-induced genes, we compared gene expression after acute exercise with different intensities, 70% and 50% V˙O2max, by qPCR. The transcriptome is dynamically changed during the first hours of recovery after intensive exercise (70% V˙O2max). A computational approach revealed that the changes might be related to up- and down-regulation of the activity of transcription activators and repressors, respectively. The exercise increased expression of many genes encoding protein kinases, while genes encoding transcriptional regulators were both up- and down-regulated. Evaluation of the gene expression after exercise with different intensities revealed that some genes changed expression in an intensity-dependent manner, but others did not: the majority of genes encoding protein kinases, oxidative phosphorylation and activator protein (AP)-1-related genes significantly correlated with markers of exercise stress (power, blood lactate during exercise and post-exercise blood cortisol), while transcriptional repressors and circadian-related genes did not. Some of the changes in gene expression after exercise seemingly may be modulated by circadian rhythm.

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Most studies examining the molecular mechanisms underlying adaptation of human skeletal muscles to aerobic exercise focused on the response to acute exercise. Here, we examined the effect of a 2‐month aerobic training program on baseline parameters in human muscle. Ten untrained males performed a one‐legged knee extension exercise for 1 h with the same relative intensity before and after a 2‐month aerobic training program. Biopsy samples were taken from vastus lateralis muscle at rest before and after the 2 month training program (baseline samples). Additionally, biopsy samples were taken from the exercised leg 1 and 4 h after the one‐legged continuous knee extension exercise. Aerobic training decreases baseline phosphorylation of FOXO1Ser256, increases that of CaMKIIT hr286, CREB1Ser133, increases baseline expression of mitochondrial proteins in respiratory complexes I–V, and some regulators of mitochondrial biogenesis (TFAM, NR4A3, and CRTC2). An increase in the baseline content of these proteins was not associated with a change in baseline expression of their genes. The increase in the baseline content of regulators of mitochondrial biogenesis (TFAM and NR4A3) was associated with a transient increase in transcription after acute exercise. Contrariwise, the increase in the baseline content of respiratory proteins does not seem to be regulated at the transcriptional level; rather, it is associated with other mechanisms. Adaptation of human skeletal muscle to regular aerobic exercise is associated not only with transient molecular responses to exercise, but also with changes in baseline phosphorylation and expression of regulatory proteins.