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MiRNAs As Possible Predictors For Training Efficacy

Recent research suggests that genes encoding micro RNA (miRNA) molecules are differentially expressed in response to training. PURPOSE: To determine whether specific miRNAs serve as possible predictors for training efficacy. METHODS: Six healthy, sedentary female subjects (mean ± SD: age 23.2 ± 3.1 years, peak oxygen uptake (VO2peak) 31.7 ± 1.6 mL·kg ·min, body mass index 23.0 ± 1.2 kg/m), aged between 20 and 27 years, performed exercise training on a cycle ergometer, three times a week, for 6 weeks. Participants were randomly assigned to either moderate intensity continuous training (MICT, n=3) or high intensity interval training (HIIT, n=3). The MICT group performed 60 min of continuous cycling at the power output (PO) calculated as corresponding to 90% of the first lactate threshold (LT). The HIIT group performed a warm-up for 10 min at the PO calculated as corresponding to 70% of the maximal heart rate (HRmax), followed by four 4-min intervals at the PO calculated as corresponding to 90% of HRmax, with 4-min recovery periods at 30 W in between. Muscle biopsies were taken preand post-training from the vastus lateralis muscle, followed by isolation of total RNA. Samples were then analyzed using a commercial miRNA array. RESULTS: Participants increased their VO2peak after 6 weeks of training by 4.2 mL·kg ·min in mean (SD: 0.9). MICT and HIIT induced significant changes in miRNA expression patterns, part of which were specific for one of the two training regimens. For instance, there was a significant (p<0.006), 5.5-fold upregulation of the anti-apoptotic miRNA 21-5p in both training groups. Furthermore, we could identify distinct shift in miRNA patterns that correlated with exercise-induced changes in physiological parameters, such as changes in VO2peak (delta VO2peak vs delta expression of miRNA 503, r=-0.9, p=0.01) or microvascular properties. CONCLUSIONS: Our data suggest that MICT and HIIT exert distinct, but also overlapping effects on miRNA expression patterns. In addition, basal miRNA expression patterns might be associated with the individual response to training. Furthermore, the data are currently reproduced using semi-quantitative RT-PCR (qPCR). Our results might have important implications for the development of personalized exercise recommendations and therapeutic strategies.