Essential amino acids are primarily responsible for the amino acid stimulation of muscle protein anabolism in healthy elderly adults
Objective: We assessed whether nonessential amino acids are required in a nutritional supplement to stimulate muscle protein anabolism in the elderly.
Design: We compared the response of muscle protein metabolism to either 18 g essential amino acids (EAA group: n = 6, age 69 ± 2 y; x̄ ± SD) or 40 g balanced amino acids (18 g essential amino acids + 22 g nonessential amino acids, BAA group; n = 8, age 71 ± 2 y) given orally in small boluses every 10 min for 3 h to healthy elderly volunteers. Muscle protein metabolism was measured in the basal state and during amino acid administration via L-[ring-2H5]phenylalanine infusion, femoral arterial and venous catheterization, and muscle biopsies.
Results: Phenylalanine net balance (in nmol · min−1 · 100 mL leg volume−1) increased from the basal state (P < 0.01), with no differences between groups (BAA: from −16 ± 5 to 16 ± 4; EAA: from −18 ± 5 to 14 ± 13) because of an increase (P < 0.01) in muscle protein synthesis and no change in breakdown.
Conclusion: Essential amino acids are primarily responsible for the amino acid–induced stimulation of muscle protein anabolism in the elderly.
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Volpi E, Kobayashi H, Sheffield-Moore M, Mittendorfer B, Wolfe RR. Essential amino acids are primarily responsible for the amino acid stimulation of muscle protein anabolism in healthy elderly adults. Am J Clin Nutr. 2003 Aug;78(2):250-8. doi: 10.1093/ajcn/78.2.250. PMID: 12885705; PMCID: PMC3192452.