Amino acid ingestion improves muscle protein synthesis in the young and elderly

Douglas Paddon-Jones, Melinda Sheffield-Moore, Xiao Jun Zhang, Elena Volpi, Steven Wolf, Asle Aarsland, Arny A. Ferrando, Robert R. Wolfe

Research output: Contribution to journalArticle

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Abstract

We recently demonstrated that muscle protein synthesis was stimulated to a similar extent in young and elderly subjects during a 3-h amino acid infusion. We sought to determine if a more practical bolus oral ingestion would also produce a similar response in young (34 ± 4 yr) and elderly (67 ± 2 yr) individuals. Arteriovenous blood samples and muscle biopsies were obtained during a primed (2.0 μmol/kg) constant infusion (0.05 μmol·kg-1·min-1) of L-[ring- 2H5]phenylalanine. Muscle protein kinetics and mixed muscle fractional synthetic rate (FSR) were calculated before and after the bolus ingestion of 15 g of essential amino acids (EAA) in young (n = 6) and elderly (n = 7) subjects. After EAA ingestion, the rate of increase in femoral artery phenylalanine concentration was slower in elderly subjects but remained elevated for a longer period. EAA ingestion increased FSR in both age groups by ∼0.04%/h (P < 0.05). However, muscle intracellular (IC) phenylalanine concentration remained significantly higher in elderly subjects at the completion of the study (young: 115.6 ± 5.4 nmol/ml; elderly: 150.2 ± 19.4 nmol/ml). Correction for the free phenylalanine retained in the muscle IC pool resulted in similar net phenylalanine uptake values in the young and elderly. EAA ingestion increased plasma insulin levels in young (6.1 ± 1.2 to 21.3 ± 3.1 μIU/ml) but not in elderly subjects (3.0 ± 0.6 to 4.3 ± 0.4 μIU/ml). Despite differences in the time course of plasma phenylalanine kinetics and a greater residual IC phenylalanine concentration, amino acid supplementation acutely stimulated muscle protein synthesis in both young and elderly individuals.

Original languageEnglish (US)
JournalAmerican Journal of Physiology - Endocrinology and Metabolism
Volume286
Issue number3 49-3
StatePublished - Mar 2004

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Muscle Proteins
Phenylalanine
Eating
Essential Amino Acids
Amino Acids
Muscle
Muscles
Plasmas
Kinetics
Biopsy
Femoral Artery
Blood
Insulin
Age Groups

Keywords

  • Aging
  • Nutrition
  • Sarcopenia
  • Supplementation

ASJC Scopus subject areas

  • Physiology
  • Endocrinology
  • Biochemistry

Cite this

Amino acid ingestion improves muscle protein synthesis in the young and elderly. / Paddon-Jones, Douglas; Sheffield-Moore, Melinda; Zhang, Xiao Jun; Volpi, Elena; Wolf, Steven; Aarsland, Asle; Ferrando, Arny A.; Wolfe, Robert R.

In: American Journal of Physiology - Endocrinology and Metabolism, Vol. 286, No. 3 49-3, 03.2004.

Research output: Contribution to journalArticle

Paddon-Jones, Douglas ; Sheffield-Moore, Melinda ; Zhang, Xiao Jun ; Volpi, Elena ; Wolf, Steven ; Aarsland, Asle ; Ferrando, Arny A. ; Wolfe, Robert R. / Amino acid ingestion improves muscle protein synthesis in the young and elderly. In: American Journal of Physiology - Endocrinology and Metabolism. 2004 ; Vol. 286, No. 3 49-3.
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abstract = "We recently demonstrated that muscle protein synthesis was stimulated to a similar extent in young and elderly subjects during a 3-h amino acid infusion. We sought to determine if a more practical bolus oral ingestion would also produce a similar response in young (34 ± 4 yr) and elderly (67 ± 2 yr) individuals. Arteriovenous blood samples and muscle biopsies were obtained during a primed (2.0 μmol/kg) constant infusion (0.05 μmol·kg-1·min-1) of L-[ring- 2H5]phenylalanine. Muscle protein kinetics and mixed muscle fractional synthetic rate (FSR) were calculated before and after the bolus ingestion of 15 g of essential amino acids (EAA) in young (n = 6) and elderly (n = 7) subjects. After EAA ingestion, the rate of increase in femoral artery phenylalanine concentration was slower in elderly subjects but remained elevated for a longer period. EAA ingestion increased FSR in both age groups by ∼0.04{\%}/h (P < 0.05). However, muscle intracellular (IC) phenylalanine concentration remained significantly higher in elderly subjects at the completion of the study (young: 115.6 ± 5.4 nmol/ml; elderly: 150.2 ± 19.4 nmol/ml). Correction for the free phenylalanine retained in the muscle IC pool resulted in similar net phenylalanine uptake values in the young and elderly. EAA ingestion increased plasma insulin levels in young (6.1 ± 1.2 to 21.3 ± 3.1 μIU/ml) but not in elderly subjects (3.0 ± 0.6 to 4.3 ± 0.4 μIU/ml). Despite differences in the time course of plasma phenylalanine kinetics and a greater residual IC phenylalanine concentration, amino acid supplementation acutely stimulated muscle protein synthesis in both young and elderly individuals.",
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