Oral amino acids stimulate muscle protein anabolism in the elderly despite higher first-pass splanchnic extraction

Elena Volpi, Bettina Mittendorfer, Steven Wolf, Robert R. Wolfe

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301 Citations (Scopus)

Abstract

Muscle protein synthesis and breakdown and amino acid transport were measured in 7 healthy young (30 ± 2 yr) and 8 healthy elderly (71 ± 2 yr) volunteers in the postabsorptive state and during the oral administration of an amino acid mixture with L-[ring-2H5]phenylalanine infusion, femoral artery and vein catheterization, and muscle biopsies. Phenylalanine first- pass splanchnic extraction was measured by adding L-[ring- 13C6]phenylalanine to the mixture. In the postabsorptive state, no differences in muscle amino acid kinetics were detected between young and elderly volunteers. Phenylalanine first-pass splanchnic extraction was significantly higher in the elderly (P < 0.003) during ingestion of amino acids, but the delivery to the leg increased to the same extent in both groups. Phenylalanine transport into the muscle, muscle protein synthesis, and net balance increased significantly (P < 0.01) and similarly in both the young and the elderly. We conclude that, despite an increased splanchnic first-pass extraction, muscle protein anabolism can be stimulated by oral amino acids in the elderly as well as in the young.

Original languageEnglish (US)
JournalAmerican Journal of Physiology - Endocrinology and Metabolism
Volume277
Issue number3 40-3
StatePublished - Sep 1999

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Viscera
Muscle Proteins
Phenylalanine
Amino Acids
Muscle
Muscles
Volunteers
Femoral Vein
Biopsy
Femoral Artery
Catheterization
Oral Administration
Leg
Eating
Kinetics

Keywords

  • Aging
  • Amino acid metabolism
  • Amino acid transport
  • Protein synthesis
  • Stable isotopes

ASJC Scopus subject areas

  • Physiology
  • Endocrinology
  • Biochemistry
  • Physiology (medical)

Cite this

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abstract = "Muscle protein synthesis and breakdown and amino acid transport were measured in 7 healthy young (30 ± 2 yr) and 8 healthy elderly (71 ± 2 yr) volunteers in the postabsorptive state and during the oral administration of an amino acid mixture with L-[ring-2H5]phenylalanine infusion, femoral artery and vein catheterization, and muscle biopsies. Phenylalanine first- pass splanchnic extraction was measured by adding L-[ring- 13C6]phenylalanine to the mixture. In the postabsorptive state, no differences in muscle amino acid kinetics were detected between young and elderly volunteers. Phenylalanine first-pass splanchnic extraction was significantly higher in the elderly (P < 0.003) during ingestion of amino acids, but the delivery to the leg increased to the same extent in both groups. Phenylalanine transport into the muscle, muscle protein synthesis, and net balance increased significantly (P < 0.01) and similarly in both the young and the elderly. We conclude that, despite an increased splanchnic first-pass extraction, muscle protein anabolism can be stimulated by oral amino acids in the elderly as well as in the young.",
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AU - Mittendorfer, Bettina

AU - Wolf, Steven

AU - Wolfe, Robert R.

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N2 - Muscle protein synthesis and breakdown and amino acid transport were measured in 7 healthy young (30 ± 2 yr) and 8 healthy elderly (71 ± 2 yr) volunteers in the postabsorptive state and during the oral administration of an amino acid mixture with L-[ring-2H5]phenylalanine infusion, femoral artery and vein catheterization, and muscle biopsies. Phenylalanine first- pass splanchnic extraction was measured by adding L-[ring- 13C6]phenylalanine to the mixture. In the postabsorptive state, no differences in muscle amino acid kinetics were detected between young and elderly volunteers. Phenylalanine first-pass splanchnic extraction was significantly higher in the elderly (P < 0.003) during ingestion of amino acids, but the delivery to the leg increased to the same extent in both groups. Phenylalanine transport into the muscle, muscle protein synthesis, and net balance increased significantly (P < 0.01) and similarly in both the young and the elderly. We conclude that, despite an increased splanchnic first-pass extraction, muscle protein anabolism can be stimulated by oral amino acids in the elderly as well as in the young.

AB - Muscle protein synthesis and breakdown and amino acid transport were measured in 7 healthy young (30 ± 2 yr) and 8 healthy elderly (71 ± 2 yr) volunteers in the postabsorptive state and during the oral administration of an amino acid mixture with L-[ring-2H5]phenylalanine infusion, femoral artery and vein catheterization, and muscle biopsies. Phenylalanine first- pass splanchnic extraction was measured by adding L-[ring- 13C6]phenylalanine to the mixture. In the postabsorptive state, no differences in muscle amino acid kinetics were detected between young and elderly volunteers. Phenylalanine first-pass splanchnic extraction was significantly higher in the elderly (P < 0.003) during ingestion of amino acids, but the delivery to the leg increased to the same extent in both groups. Phenylalanine transport into the muscle, muscle protein synthesis, and net balance increased significantly (P < 0.01) and similarly in both the young and the elderly. We conclude that, despite an increased splanchnic first-pass extraction, muscle protein anabolism can be stimulated by oral amino acids in the elderly as well as in the young.

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KW - Stable isotopes

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