Skeletal Muscle MicroRNA Are Sensitive To Energy But Not Acute Macronutrient Availability During Energy Deficit

PURPOSE: Consumption of essential amino acids (EAA) during exercise recovery alters the expression of microRNA (miRNA) that govern skeletal muscle anabolism during energy balance. Whether consuming high-quality protein with additional energy as EAA or carbohydrate differentially alters miRNA during energy deficit is unclear. Therefore, we examined the effects of an EAA-enriched whey protein with added EAA or added carbohydrate on miRNA expression during exercise recovery in energy balance and energy deficit. METHODS: 16 adults (mean ± SD; age: 26 ± 5y, BMI: 25 ± 3 kg/m2) completed a randomized, double-blind parallel study of two 5d energy conditions (BAL, energy balance; DEF, 30 ± 3% energy requirements) separated by ≥7d. Volunteers consumed either an EAA-enriched whey drink with added EAA (+EAA; 304 kcal, 56 g protein, 48 g EAA, 17 g carbohydrate, 2 g fat, n = 7) or added carbohydrate (+CHO; 311 kcal, 34 g protein, 24 g EAA, 40 g carbohydrate, 2 g fat, n = 9) after 60 min of load carriage (59 ± 4% V̇O2peak) and alternating step ups (9 sets x 16 repetitions). miRNA (microarray RT-qPCR) expressions were determined at rest (PRE) and 4 h into exercise recovery (REC). miRNA fold changes were expressed relative to PRE BAL within treatment. Muscle protein synthesis (MPS; 2H5-phenylalanine) was determined during recovery. miRNA functionality was identified via bioinformatics (miRPath/Kegg) and associations between miRNA and MPS were assessed with Spearman’s correlations. RESULTS: Of 84 miRNA assessed, 3 miRNA decreased and 2 increased during REC vs. PRE (all, P < 0.05, FDR < 0.1), independent of treatment and condition. Three miRNA (miR-194-5p, miR-324-3p, let-7i-5p) increased (P < 0.05, FDR < 0.1) during DEF vs. BAL, regardless of time and treatment. During REC, miR-194-5p was inversely associated with MPS (r = -0.587, P < 0.05) under DEF and identified to target FoxO, p53, PI3k-Akt, and insulin signaling pathways. CONCLUSIONS: These data suggest that following exercise and protein intake, miRNA related to muscle adaptation are sensitive to energy status, independent of consuming additional EAA or carbohydrate. Further, these miRNA are implicated in signaling pathways related to energy homeostasis and protein turnover during energy deficit, with miR-194-5p potentially contributing to MPS regulation. USAMRDC; The opinions or assertions contained herein are the private views of the authors and are not to be construed as official or as reflecting the views of the Army or the Department of Defense