Interpretation of exercise-induced changes in human skeletal muscle mRNA expression depends on the timing of the post-exercise biopsies

Abstract

Background Exercise elicits a range of adaptive responses in skeletal muscle, which include changes in mRNA expression. To better understand the health benefits of exercise training, it is important to investigate the underlying molecular mechanisms of skeletal muscle adaptation to exercise. However, most studies have assessed the molecular events at only a few time-points within a short time frame post-exercise, and the variations of gene expression kinetics have not been addressed systematically. Methods We assessed the mRNA expression of 23 gene isoforms implicated in the adaptive response to exercise at six time-points (0, 3, 9, 24, 48, and 72 h post exercise) over a 3-day period following a single session of high-intensity interval exercise. Results The temporal patterns of target gene expression were highly variable and the expression of mRNA transcripts detected was largely dependent on the timing of muscle sampling. The largest fold change in mRNA expression of each tested target gene was observed between 3 and 72 h post-exercise. Discussion and Conclusions Our findings highlight an important gap in knowledge regarding the molecular response to exercise, where the use of limited time-points within a short period post-exercise has led to an incomplete understanding of the molecular response to exercise. Muscle sampling timing for individual studies needs to be carefully chosen based on existing literature and preliminary analysis of the molecular targets of interest. We propose that a comprehensive time-course analysis on the exercise-induced transcriptional response in humans will significantly benefit the field of exercise molecular biology.

Mechanical loading of bioengineered skeletal muscle in vitro recapitulates gene expression signatures of resistance exercise in vivo

“…These genes were therefore analyzed at 0.5, 3, and 24 h post-loading in bioengineered mouse muscle to enable a direct comparison with humans after acute RE. First, the majority of these genes predominantly increased at 3 h post-loading and returned to basal levels at 24 h. This temporal gene regulatory profile has been observed several times in response to exercise in vivo in which gene expression tends to peak at 3-8 h post-exercise (Barrès et al, 2012;Chen et al, 2002;Drummond et al, 2008;Knuiman et al, 2018;Kuang et al, 2020) and generally returns to basal levels within 24 h Liu et al, 2010;Yang et al, 2005).…”

“…These genes were therefore analyzed at 0.5, 3, and 24 h post‐loading in bioengineered mouse muscle to enable a direct comparison with humans after acute RE. First, the majority of these genes predominantly increased at 3 h post‐loading and returned to basal levels at 24 h. This temporal gene regulatory profile has been observed several times in response to exercise in vivo in which gene expression tends to peak at 3–8 h post‐exercise (Barrès et al, 2012; Chen et al, 2002; Drummond et al, 2008; Knuiman et al, 2018; Kuang et al, 2020) and generally returns to basal levels within 24 h (Egan & Zierath, 2012; Liu et al, 2010; Yang et al, 2005). When comparing the changes in gene expression at 3 h with the human transcriptome data, 83% of these genes (MSN, CTTN, FLNB, TIMP3, ITGB3, LAMA5, COL4A1, CRK, CD63, GSK3β, SMAD3, WNT9A, ITPR, STAT3, RARA, F2LR3, KDR, DOT1L) showed no significant difference in expression between loaded mouse bioengineered muscle and human muscle after acute RE.…”

“…It is also worth noting that analysis of human muscle involved pooling transcriptomic datasets across 110 biopsies (37 pre/57 post after outlier removal) over multiple studies (Turner et al, 2019b), and therefore encompassed all timepoints from immediately post and up to 24 h post‐acute RE. Where, gene expression is typically greatest at 3–8 h post exercise (Barrès et al, 2012; Chen et al, 2002; Drummond et al, 2008; Knuiman et al, 2018; Kuang et al, 2020) and generally returns to basal levels within 24 h (Egan & Zierath, 2012; Liu et al, 2010; Yang et al, 2005). Therefore, the majority of transcriptional alterations detected at 3 h in the bioengineered muscle may also be exemplifying this temporal activation in gene expression post‐loading.…”

Modeling exercise using optogenetically contractible Drosophila larvae

“…Exercise is known to induce robust transcriptional responses within skeletal muscles [7, 52] and proper assessment of such transcriptional changes may depend on the timing or duration after the exercise bouts [53]. To identify gene expression changes that respond immediately to an exercise bout, we chose to assess the transcriptional responses that happen in the body wall muscles in response to our larval acute exercise regimen.…”

Aerobic‐interval exercise with blood flow restriction potentiates early markers of metabolic health in man

“…Compared to the other exercise sessions, BFR‐interval exercise evoked similar responses of the investigated mitochondrial genes, including CS , p53 , COXIV‐1 and COXIV‐2 . The finding that none of the sessions significantly changed the expression of these genes suggests that they are either under post‐transcriptional control, as shown in cell culture experiments for citrate synthase (CS) 54 or alternatively, that the time point of measurement (+3h post exercise) was not optimal for detecting changes at the mRNA level 55 . By contrast, the expression of both PGC‐1α2 and ‐1α3 was selectively increased by the BFR‐session.…”