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Leucine supplementation improves muscle protein synthesis in elderly men independently of hyperaminoacidaemia
Author(s) -
Rieu Isabelle,
Balage Michèle,
Sornet Claire,
Giraudet Christophe,
Pujos Estelle,
Grizard Jean,
Mosoni Laurent,
Dardevet Dominique
Publication year - 2006
Publication title -
the journal of physiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.802
H-Index - 240
eISSN - 1469-7793
pISSN - 0022-3751
DOI - 10.1113/jphysiol.2006.110742
Subject(s) - leucine , phenylalanine , medicine , endocrinology , ingestion , myofibril , amino acid , muscle protein , chemistry , biology , skeletal muscle , biochemistry
The present study was designed to assess the effects of dietary leucine supplementation on muscle protein synthesis and whole body protein kinetics in elderly individuals. Twenty healthy male subjects (70 ± 1 years) were studied before and after continuous ingestion of a complete balanced diet supplemented or not with leucine. A primed (3.6 μmol kg −1 ) constant infusion (0.06 μmol kg −1 min −1 ) of l ‐[1‐ 13 C]phenylalanine was used to determine whole body phenylalanine kinetics as well as fractional synthesis rate (FSR) in the myofibrillar fraction of muscle proteins from vastus lateralis biopsies. Whole body protein kinetics were not affected by leucine supplementation. In contrast, muscle FSR, measured over the 5‐h period of feeding, was significantly greater in the volunteers given the leucine‐supplemented meals compared with the control group (0.083 ± 0.008 versus 0.053 ± 0.009% h −1 , respectively, P < 0.05). This effect was due only to increased leucine availability because only plasma free leucine concentration significantly differed between the control and leucine‐supplemented groups. We conclude that leucine supplementation during feeding improves muscle protein synthesis in the elderly independently of an overall increase of other amino acids. Whether increasing leucine intake in old people may limit muscle protein loss during ageing remains to be determined.