Muscle protein metabolism responds similarly to exogenous amino acids in healthy younger and older adults during NO-induced hyperemia

E. Lichar Dillon, Shanon L. Casperson, William J. Durham, Kathleen M. Randolph, Randall J. Urban, Elena Volpi, Masood Ahmad, Michael P. Kinsky, Melinda Sheffield-Moore

Research output: Contribution to journalArticle

24 Scopus citations

Abstract

The combination of increasing blood flow and amino acid (AA) availability provides an anabolic stimulus to the skeletal muscle of healthy young adults by optimizing both AA delivery and utilization. However, aging is associated with a blunted response to anabolic stimuli and may involve impairments in endothelial function. We investigated whether age-related differences exist in the muscle protein anabolic response to AAs between younger (30 ± 2 yr) and older (67 ± 2 yr) adults when macrovascular and microvascular leg blood flow were similarly increased with the nitric oxide (NO) donor, sodium nitroprusside (SNP). Regardless of age, SNP+AA induced similar increases above baseline (P ≤ 0.05) in macrovascular flow (4.3 vs. 4.4 ml·min -1·100 ml leg -1 measured using indocyanine green dye dilution), microvascular flow (1.4 vs. 0.8 video intensity/s measured using contrast-enhanced ultrasound), phenylalanine net balance (59 vs. 68 nmol·min -1·100 ml·leg -1), fractional synthetic rate (0.02 vs. 0.02%/h), and model-derived muscle protein synthesis (62 vs. 49 nmol·min -1·100 ml·leg -1) in both younger vs. older individuals, respectively. Provision of AAs during NO-induced local skeletal muscle hyperemia stimulates skeletal muscle protein metabolism in older adults to a similar extent as in younger adults. Our results suggest that the aging vasculature is responsive to exogenous NO and that there is no age-related difference per se in AA-induced anabolism under such hyperemic conditions.

Original languageEnglish (US)
Pages (from-to)R1408-R1417
JournalAmerican Journal of Physiology - Regulatory Integrative and Comparative Physiology
Volume301
Issue number5
DOIs
StatePublished - Nov 1 2011

Keywords

  • Aging
  • Microvascular blood flow
  • Nitric oxide

ASJC Scopus subject areas

  • Physiology
  • Physiology (medical)

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