Dynamic regulation of circulating microRNA during acute exhaustive exercise and sustained aerobic exercise training

Abstract

MicroRNAs (miRNAs) are intracellular mediators of essential biological functions. Recently, plasma-based 'circulating' miRNAs (c-miRNAs) have been shown to control cellular processes, but the c-miRNA response to human exercise remains unknown. We sought to determine whether c-miRNAs are dynamically regulated in response to acute exhaustive cycling exercise and sustained rowing exercise training using a longitudinal, repeated measures study design. Specifically, c-miRNAs involved in angiogenesis (miR-20a, miR-210, miR-221, miR-222, miR-328), inflammation (miR-21, miR-146a), skeletal and cardiac muscle contractility (miR-21, miR-133a), and hypoxia/ischaemia adaptation (miR-21, miR-146a, and miR-210) were measured at rest and immediately following acute exhaustive cycling exercise in competitive male rowers (n = 10, age = 19.1 ± 0.6 years) before and after a 90 day period of rowing training. Distinct patterns of c-miRNA response to exercise were observed and adhered to four major profiles: (1) c-miRNA up-regulated by acute exercise before and after sustained training (miR-146a and miR-222), (2) c-miRNA responsive to acute exercise before but not after sustained training (miR-21 and miR-221), (3) c-miRNA responsive only to sustained training (miR-20a), and (4) non-responsive c-miRNA (miR-133a, miR-210, miR-328). Linear correlations were observed between peak exercise levels of miR-146a and VO2max (r = 0.63, P = 0.003) and between changes in resting miR-20a and changes in VO2max (pre-training vs. post-training, r = 0.73; P = 0.02). Although future work is required, these results suggest the potential value of c-miRNAs as exercise biomarkers and their possible roles as physiological mediators of exercise-induced cardiovascular adaptation.

Figure 1

Candidate miRNAs that regulate cellular processes integral to exercise training and cardiovascular adaptation

Figure 3. Distinct regulatory profiles of specific c-miRNA after acute exhaustive exercise and sustained exercise training

A–H, for each athlete, baseline c-miRNA levels under resting condition are assigned a fold change of 1, to which measurements obtained during subsequent study time points are compared (i.e. rest vs. 1 min after exhaustive exercise (post-ex) during baseline and post-training stages). In all panels, bar and whisker plots are utilized where horizontal lines denote statistical mean, grey boxes denote 25% and 75% percentile confidence intervals, and error bars reflect maximum and minimum values. Profile 1 denotes c-miRNA that respond to acute exhaustive exercise both before and after sustained training (A and B). Profile 2 denotes c-miRNAs that respond to acute exhaustive exercise before but not after sustained aerobic training (C and D). Profile 3 denotes c-miRNAs that respond to sustained aerobic training but not acute exhaustive exercise (E). Profile 4 denotes c-miRNAs that do not respond to acute or sustained aerobic training (F, G and H). *P < 0.05 compared to baseline resting value, †P < 0.05 compared to post-training resting value, **P marginally greater than 0.05 compared to baseline resting value; NS signifies P > 0.05 compared to baseline resting value.

Figure 2. Baseline expression levels of c-miRNAs in plasma

At baseline resting conditions prior to initiation of the controlled study period, c-miRNA levels in plasma were measured in 10 athletes (n = 10) by RT-QPCR and are displayed as relative levels based on the formula (2^−ΔC_t× 10⁴). All c-miRNAs chosen for analysis are detectable and display low (miR-133a and miR-328), medium (miR-146a, miR-221, miR-222 and miR-210), or high (miR-20a and miR-21) expression at baseline. Data are presented as statistical means, and error bars show SEM.

Figure 4. Alterations in specific c-miRNAs directly correlate with changes in peak oxygen consumption

For each athlete, baseline c-miRNA levels under resting condition are assigned a fold change of 1, to which measurements obtained during subsequent study time points are compared. Scatter plots display circulating levels of miR-146a (A) and miR-20a (C) for each participant at 4 study time points (i.e. rest vs. 1 min post-exercise (post-ex) during baseline and post-training stages). A direct correlation (r = correlation coefficient) is observed between peak exercise levels of miR-146a (baseline and post-training) and peak oxygen consumption, (baseline and post-training) (B). A direct correlation is also observed between changes in resting levels of miR-20a (baseline vs. post-training, %Δ in miR-20a) and changes in peak oxygen consumption (baseline vs. post-training, %Δ in ) (D).