Co-ingestion of cluster dextrin carbohydrate does not increase exogenous protein-derived amino acid release or myofibrillar protein synthesis following a whole-body resistance exercise in moderately trained younger males: a double-blinded randomized controlled crossover trial

PURPOSE: This study investigates if co-ingestion of cluster dextrin (CDX) augments the appearance of intrinsically labeled meat protein hydrolysate-derived amino acid (D(5)-phenylalanine), Akt/mTORC1 signaling, and myofibrillar protein fractional synthetic rate (FSR). METHODS: Ten moderately trained healthy males (age: 21.5 ± 2.1 years, body mass: 75.7 ± 7.6 kg, body mass index (BMI): 22.9 ± 2.1 kg/m(2)) were included for a double-blinded randomized controlled crossover trial. Either 75 g of CDX or glucose (GLC) was given in conjunction with meat protein hydrolysate (0.6 g protein * FFM(−1)) following a whole-body resistance exercise. A primed-continuous intravenous infusion of L-[(15)N]-phenylalanine with serial muscle biopsies and venous blood sampling was performed. RESULTS: A time × group interaction effect was found for serum D(5)-phenylalanine enrichment (P < 0.01). Serum EAA and BCAA concentrations showed a main effect for group (P < 0.05). T(max) serum BCAA was greater in CDX as compared to GLC (P < 0.05). However, iAUC of all serum parameters did not differ between CDX and GLC (P > 0.05). T(max) serum EAA showed a trend towards a statistical significance favoring CDX over GLC. The phosphorylation of p70S6K(Thr389), rpS6(Ser240/244), ERK1/2(Thr202/Tyr204) was greater in CDX compared to GLC (P < 0.05). However, postprandial myofibrillar FSR did not differ between CDX and GLC (P = 0.17). CONCLUSION: In moderately trained younger males, co-ingestion of CDX with meat protein hydrolysate does not augment the postprandial amino acid availability or myofibrillar FSR as compared to co-ingestion of GLC during the recovery from a whole-body resistance exercise despite an increased intramuscular signaling. TRIAL REGISTRATION: ClinicalTrials.gov ID: NCT03303729 (registered on October 3, 2017).