期刊
AMERICAN JOURNAL OF CLINICAL NUTRITION
卷 78, 期 2, 页码 250-258出版社
OXFORD UNIV PRESS
DOI: 10.1093/ajcn/78.2.250
关键词
sarcopenia; aging; protein synthesis; proteolysis; nutritional supplements
资金
- NCRR NIH HHS [M01 RR00073, M01 RR000073] Funding Source: Medline
- NIA NIH HHS [R01 AG015780, R01 AG018311, R01 AG15780, P30 AG024832, R01 AG018311-03, P60 AG17231, R01 AG18311, P60 AG017231] Funding Source: Medline
Background: Nutritional supplementation may be used to treat muscle loss with aging (sarcopenia). However, if physical activity does not increase, the elderly tend to compensate for the increased energy delivered by the supplements with reduced food intake, which results in a calorie substitution rather than supplementation. Thus, an effective supplement should stimulate muscle anabolism more efficiently than food or common protein supplements. We have shown that balanced amino acids stimulate muscle protein anabolism in the elderly, but it is unknown whether all amino acids are necessary to achieve this effect. 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; (x) over bar +/- 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-H-2(5)]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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