Chocolate Milk Consumption During Recovery from Endurance Exercise Affects Intracellular Events of Skeletal Muscle Protein Synthesis and Proteolysis

Abstract

PURPOSEThe aim was to determine effects of fat‐free chocolate milk consumption during recovery from endurance exercise on intracellular proteins (ICP) influencing skeletal muscle synthesis and proteolysis.METHODS8 active males (23.7 ± 1.6 y, 76.0 ± 3.8 kg, BMI = 24±1, 14.4 ± 2.0% body fat, VO2peak = 53.1 ± 1.6) participated in a randomized, crossover‐design study during which they consumed a eucaloric diet for 2wks. Protein intake was 1.5 g·kg−1. After each week, participants consumed 16 oz. of either fat‐free chocolate milk (MILK) or a non‐nitrogenous, isocaloric control beverage (CON) after a 45‐min run at 65% of VO2peak. Protein expression of PI3K and relative phosphorylation of eEF2, mTOR, eIF4E‐BP1, and rpS6and relative phosphorylation of Akt and FOXO3a, total protein expression of ubiquitin and PSMA2, and activity of caspase‐3 and the 26S proteasome were quantified for protein synthesis and proteolysis, respectively, from muscle biopsied during 3 h of recovery.RESULTSSignificant results for 0 to 3 h recovery (p<0.05): FOXO3a (Ser253) decreased (1.39 ± 0.14 to 0.98 ± 0.10 AU) and proteasome core activity increased (1.79 ± 0.22 to 2.30 ± 0.19 RFU) for CON vs MILK. Caspase‐3 activity decreased for MILK (3.71 ± 0.61 to 1.68 ± 0.37 AU). Akt (Ser473) was reduced for MILK and CON (0.76 ± 0.13 to 0.27 ± 0.08 AU and 0.72 ± 0.21 to 0.29 ± 0.12 AU, respectively). eIF4E‐BP1 (Thr37/46) increased for MILK (0.63 ± 0.03 to 0.88 ± 0.08 AU).CONCLUSIONFindings suggest that drinking fat‐free chocolate milk after endurance exercise attenuates ICP activity specific to proteolysis and enhances that of protein synthesis during recovery.