Myofibrillar muscle protein synthesis rates subsequent to a meal in response to increasing doses of whey protein at rest and after resistance exercise

Abstract

Background: The intake of whey, compared with casein and soy protein intakes, stimulates a greater acute response of muscle protein synthesis (MPS) to protein ingestion in rested and exercised muscle. Objective: We characterized the dose-response relation of postabsorptive rates of myofibrillar MPS to increasing amounts of whey protein at rest and after exercise in resistance-trained, young men. Design: Volunteers (n = 48) consumed a standardized, high-protein (0.54 g/kg body mass) breakfast. Three hours later, a bout of unilateral exercise (8 3 10 leg presses and leg extensions; 80% onerepetition maximum) was performed. Volunteers ingested 0, 10, 20, or 40 g whey protein isolate immediately (w10 min) after exercise. Postabsorptive rates of myofibrillar MPS and whole-body rates of phenylalanine oxidation and urea production were measured over a 4-h postdrink period by continuous tracer infusion of labeled [ 13 C 6 ] phenylalanine and [ 15 N 2 ] urea. Results: Myofibrillar MPS (mean 6 SD) increased (P , 0.05) above 0 g whey protein (0.041 6 0.015%/h) by 49% and 56% with the ingestion of 20 and 40 g whey protein, respectively, whereas no additional stimulation was observed with 10 g whey protein (P . 0.05). Rates of phenylalanine oxidation and urea production increased with the ingestion of 40 g whey protein.Conclusions: A 20-g dose of whey protein is sufficient for the maximal stimulation of postabsorptive rates of myofibrillar MPS in rested and exercised muscle of w80-kg resistance-trained, young men. A dose of whey protein .20 g stimulates amino acid oxidation and ureagenesis. This trial was registered at http://www.isrctn.org/ as ISRCTN92528122.Am J Clin Nutr 2014;99:86-95.

New strategies in sport nutrition to increase exercise performance

“…Because the mechanically sensitive pathways and the resistance exercise pathways are distinct, consuming essential amino acids following resistance exercise significantly activates mTORC1 above resistance exercise alone [103]. We have known for several decades that consuming essential amino acids in close proximity to resistance exercise can enhance the protein synthetic response in the skeletal muscle [104] and we now know that ~20g of high quality protein in the fasted [105] or fed [106] state is sufficient to saturate the protein synthetic response following resistance exercise in young men. Furthermore supplementation of protein during a program of resistance training is well proven to enhance lean mass/muscle gains [84].…”

“…Several protein dose response studies have demonstrated that ~20g of high quality protein (egg white protein or whey protein) following resistance exercise with a small amount of muscle mass (single leg training) is sufficient to maximally stimulate MPS in the trained leg [105,106]. These studies have gone a long way to optimising post exercise nutrition.…”

Leucine elicits myotube hypertrophy and enhances maximal contractile force in tissue engineered skeletal muscle in vitro

“…Indeed, acute human studies have observed activation of mTORC1 and its downstream targets (e.g., p70S6K, rpS6, and 4EBP‐1) following ingestion of mixed amino acids, and this is coupled with an increase in muscle protein synthesis (MPS) in the ensuing 60–120 min (Atherton, Etheridge et al, 2010; Koopman et al, 2006; Paddon‐Jones et al, 2004; Volpi, Kobayashi, Sheffield‐Moore, Mittendorfer, & Wolfe, 2003). Furthermore, when human skeletal muscle undergoes loading prior to amino acid ingestion this effect on mTORC1 signaling and MPS is potentiated (Moore, Atherton, Rennie, Tarnopolsky, & Phillips, 2011; Witard et al, 2014). The necessity for mTOR activation in mediating the MPS response to both amino acids and muscle loading is evidenced by the fact that in rodents, both stimuli fail to augment the synthetic response when in the presence of the mTOR inhibitor rapamycin (Anthony et al, 2000; Kubica, Bolster, Farrell, Kimball, & Jefferson, 2005).…”

Effects of skeletal muscle energy availability on protein turnover responses to exercise

“…A recent meta-analysis examining the efficacy of protein supplementation to increase lean body mass and strength after REX training revealed that protein supplementation significantly increased muscle mass and strength compared with placebo (Cermak et al, 2012). While the anabolic capacity of protein availability in human skeletal muscle is primarily attributable to the ingestion of essential amino acids (EAAs) and in particular the branched chain amino acid leucine, factors such as the dose (Moore et al, 2009a;Witard et al, 2013), source (Reidy et al, 2013;Tang et al, 2009;Tipton et al, 2004) and the timing/distribution of intake (Areta et al, 2013;Esmarck et al, 2001) also modulate the effectiveness for protein supplementation to augment muscle mass with REX. The 'anabolic' signalling pathways activated by REX and protein ingestion centre on intramuscular mTORC1 signalling (Kimball and Jefferson, 2010).…”