Postexercise net protein synthesis in human muscle from orally administered amino acids

Abstract

We examined the response of net muscle protein synthesis to ingestion of amino acids after a bout of resistance exercise. A primed, constant infusion ofl-[ ring-2H5]phenylalanine was used to measure net muscle protein balance in three male and three female volunteers on three occasions. Subjects consumed in random order 1 liter of 1) a mixed amino acid (40 g) solution (MAA), 2) an essential amino acid (40 g) solution (EAA), and 3) a placebo solution (PLA). Arterial amino acid concentrations increased ∼150–640% above baseline during ingestion of MAA and EAA. Net muscle protein balance was significantly increased from negative during PLA ingestion (−50 ± 23 nmol ⋅ min−1 ⋅ 100 ml leg volume−1) to positive during MAA ingestion (17 ± 13 nmol ⋅ min−1 ⋅ 100 ml leg volume−1) and EAA (29 ± 14 nmol ⋅ min−1 ⋅ 100 ml leg volume−1; P < 0.05). Because net balance was similar for MAA and EAA, it does not appear necessary to include nonessential amino acids in a formulation designed to elicit an anabolic response from muscle after exercise. We concluded that ingestion of oral essential amino acids results in a change from net muscle protein degradation to net muscle protein synthesis after heavy resistance exercise in humans similar to that seen when the amino acids were infused.

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].…”

Oral branched-chain amino acid supplements that reduce brain serotonin during exercise in rats also lower brain catecholamines

“…As the outcome confirmed the hypothesis, we also examined if the inclusion of TYR with BCAA would block the BCAA effect on catecholamines. Finally, since essential amino acid mixtures, which contain BCAA, are used to increase muscle protein synthesis without consideration of possible effects on brain (Tipton et al 1999), we examined how such essential amino acid supplements modify 5HT and catecholamines in brain. We focused on hypothalamus in this study, as this region shows clear effects of each precursor on the production rate of the respective transmitter (Fernstrom and Fernstrom 1995b, c).…”

“…TYR was added to the BCAA mixture in some groups at a dose of 100 mg/kg. The amino acid pattern employed by Tipton et al (1999) in an oral drink given to humans was used to construct the amino acid solution of one essential amino acid (EAA) mixture employed in our studies. This pattern approximates the essential amino acid composition of muscle protein (Tipton et al 1999).…”

“…The amino acid pattern employed by Tipton et al (1999) in an oral drink given to humans was used to construct the amino acid solution of one essential amino acid (EAA) mixture employed in our studies. This pattern approximates the essential amino acid composition of muscle protein (Tipton et al 1999). We again performed a preliminary study using the dose listed in the table, and one-half of this dose, administered by stomach tube in 10 ml/kg water.…”

“…Tyrosine was added to the BCAA mixture in some experimental groups at a dose of 100 mg/kg. The EAA1 mixture is derived from that of Tipton et al (1999). The EAA2 mixture is derived from the EAA pattern of non-fat dried milk (US Department of Agriculture, Agricultural Research Service 2006), as described in "Materials and methods".…”