The influence of carbohydrate–protein co‐ingestion following endurance exercise on myofibrillar and mitochondrial protein synthesis

• Published in: The Journal of physiology Vol. 589; no. 16; pp. 4011 - 4025
• Main Authors: Breen, Leigh, Philp, Andrew, Witard, Oliver C., Jackman, Sarah R., Selby, Anna, Smith, Ken, Baar, Keith, Tipton, Kevin D.
• Format: Journal Article
• Language: English
• Published: Oxford, UK Blackwell Publishing Ltd 01.08.2011; Wiley Subscription Services, Inc; Blackwell Science Inc
• Subjects: Adult; Beverages; Cross-Over Studies; Dietary Carbohydrates - administration & dosage; Dietary Proteins - administration & dosage; Humans; Male; Mitochondrial Proteins - biosynthesis; Muscle Proteins - biosynthesis; Muscle Proteins - physiology; Myofibrils - metabolism; Myofibrils - physiology; Physical Endurance - physiology; Single-Blind Method; Skeletal Muscle and Exercise; Young Adult
• ISSN: 0022-3751; 1469-7793; 1469-7793
• DOI: 10.1113/jphysiol.2011.211888

Non‐technical summary  A single bout of exercise stimulates the production of new muscle proteins. Furthermore, ingesting protein in close proximity to exercise enhances the metabolic response. Long‐term exercise training promotes muscle adaptation, and the mode of exercise performed determines the type of proteins that are made. To date, the types of proteins that are made when protein is ingested after endurance exercise are not known. We report that when well‐trained male cyclists ingest protein with a carbohydrate drink after a high‐intensity ride, production of proteins responsible for muscle contraction is increased. Proteins responsible for aerobic energy production are not responsive to protein feeding. Furthermore, specific signals within the muscle that control protein synthesis are responsive to protein ingestion, providing a potential mechanism to underpin our primary findings. These results suggest that protein feeding after intense endurance exercise may be important in maintaining the structural quality and power generating capacity of the muscle.   The aim of the present study was to determine mitochondrial and myofibrillar muscle protein synthesis (MPS) when carbohydrate (CHO) or carbohydrate plus protein (C+P) beverages were ingested following prolonged cycling exercise. The intracellular mechanisms thought to regulate MPS were also investigated. In a single‐blind, cross‐over study, 10 trained cyclists (age 29 ± 6 years, 66.5 ± 5.1 ml kg−1 min−1) completed two trials in a randomized order. Subjects cycled for 90 min at 77 ± 1% before ingesting a CHO (25 g of carbohydrate) or C+P (25 g carbohydrate + 10 g whey protein) beverage immediately and 30 min post‐exercise. A primed constant infusion of l‐[ring‐13C6]phenylalanine began 1.5h prior to exercise and continued until 4h post‐exercise. Muscle biopsy samples were obtained to determine myofibrillar and mitochondrial MPS and the phosphorylation of intracellular signalling proteins. Arterialized blood samples were obtained throughout the protocol. Plasma amino acid and urea concentrations increased following ingestion of C+P only. Serum insulin concentration increased more for C+P than CHO. Myofibrillar MPS was ∼35% greater for C+P compared with CHO (0.087 ± 0.007 and 0.057 ± 0.006%h−1, respectively; P= 0.025). Mitochondrial MPS rates were similar for C+P and CHO (0.082 ± 0.011 and 0.086 ± 0.018%h−1, respectively). mTORSer2448 phosphorylation was greater for C+P compared with CHO at 4h post‐exercise (P < 0.05). p70S6KThr389 phosphorylation increased at 4h post‐exercise for C+P (P < 0.05), whilst eEF2Thr56 phosphorylation increased by ∼40% at 4h post‐exercise for CHO only (P < 0.01). The present study demonstrates that the ingestion of protein in addition to carbohydrate stimulates an increase in myofibrillar, but not mitochondrial, MPS following prolonged cycling. These data indicate that the increase in myofibrillar MPS for C+P could, potentially, be mediated through p70S6K, downstream of mTOR, which in turn may suppress the rise in eEF2 on translation elongation.