Abstract
Skeletal muscle microRNAs (myomiR) expression is modulated by exercise, however, the influence of endurance exercise mode, combined with essential amino acid and carbohydrate (EAA+CHO) supplementation are not well defined. This study determined the effects of weighted versus non-weighted endurance exercise, with or without EAA+CHO ingestion on myomiR expression and their association with muscle protein synthesis (MPS). Twenty five adults performed 90 min of metabolically-matched (2.2 VO2 L·m−1) load carriage (LC; performed on a treadmill wearing a vest equal to 30% of individual body mass) or cycle ergometry (CE) exercise, during which EAA+CHO (10 g EAA and 46 g CHO) or non-nutritive control (CON) drinks were consumed. Expression of myomiR (RT-qPCR) were determined at rest (PRE), immediately post-exercise (POST), and 3 h into recovery (REC). Muscle protein synthesis (2H5-phenylalanine) was measured during exercise and recovery. Relative to PRE, POST, and REC expression of miR-1-3p, miR-206, miR-208a-5, and miR-499 was lower (P < 0.05) for LC compared to CE, regardless of dietary treatment. Independent of exercise mode, miR-1-3p and miR-208a-5p expression were lower (P < 0.05) after ingesting EAA+CHO compared to CON. Expression of miR-206 was highest for CE-CON than any other treatment (exercise-by-drink, P < 0.05). Common targets of differing myomiR were identified as markers within mTORC1 signaling, and miR-206 and miR-499 were inversely associated with MPS rates immediately post-exercise. These findings suggest the alterations in myomiR expression between exercise mode and EAA+CHO intake may in part be due to differing MPS modulation immediately post-exercise.
Highlights
Exercise, essential amino acids (EAA), and insulin modulate anabolic signaling networks that regulate skeletal muscle protein synthesis (MPS) (Margolis and Rivas, 2015)
Expressions of miR-1-3p (P = 0.02), miR-206 (P < 0.01), miR208a-5 (P = 0.01) and miR-499 (P < 0.01) were lower for load carriage (LC) compared to cycle ergometry (CE), regardless of dietary treatment (Figures 1A–D). miR-1-3p (P < 0.01) and miR-208a-5p (P = 0.03) expressions were lower after ingesting EAA+CHO compared to CON, FIGURE 1 | Data are mean ± SD
Independent of exercise mode and dietary treatment, phosphorylation of p70S6KThr389 and rpS6Ser235/236 was 337 ± 262% and 457 ± 357%, respectively, higher at POST compared to performed at rest (PRE) (Figures 3C, D, P < 0.01)
Summary
Essential amino acids (EAA), and insulin modulate anabolic signaling networks that regulate skeletal muscle protein synthesis (MPS) (Margolis and Rivas, 2015) These anabolic stimuli converge on the mechanistic target of rapamycin complex 1 (mTORC1), which when activated increases MPS (Drummond et al, 2009a; Pasiakos, 2012; Laplante and Sabatini, 2013). Combining the contractile forces of resistance-type exercise with EAA ingestion downregulates miR-1 expression in young men (Drummond et al, 2008) These acute findings support long-term data by Mccarthy and Esser (2007) showing that, in a functional overload model (rodents), miR-1 and miR133a expression is diminished during long-term periods of muscle hypertrophy. The divergent myomiR responses to exercise mode and EAA intake may in part be triggered by altered MPS rates, no study has directly tested this theory
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