title: Muscle protein metabolism responds similarly to exogenous amino acids in healthy younger and older adults during NO-induced hyperemia.
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.
authors: Divisions of Endocrinology and Metabolism, Department of Internal Medicine, University of Texas Medical Branch, Galveston, Texas 77555, USA.
authors: E Lichar
authors: EL
authors: Dillon
authors: Shanon L
authors: SL
authors: Casperson
authors: William J
authors: WJ
authors: Durham
authors: Kathleen M
authors: KM
authors: Randolph
authors: Randall J
authors: RJ
authors: Urban
authors: Elena
authors: E
authors: Volpi
authors: Masood
authors: M
authors: Ahmad
authors: Michael P
authors: MP
authors: Kinsky
authors: Melinda
authors: M
authors: Sheffield-Moore
mesh_terms: D000328:Adult; D000367:Age Factors; D000368:Aged; D000375:Aging / Q000378:metabolism*; D000596:Amino Acids / Q000008:administration & dosage / Q000378:metabolism*; D001706:Biopsy; D001783:Blood Flow Velocity; D001786:Blood Glucose / Q000378:metabolism; D005260:Female; D006801:Humans; D006940:Hyperemia / Q000139:chemically induced / Q000378:metabolism* / Q000503:physiopathology; D007261:Infusions, Intra-Arterial; D007262:Infusions, Intravenous; D007328:Insulin / Q000097:blood; D035002:Lower Extremity; D008297:Male; D008833:Microcirculation; D017551:Microdialysis; D009124:Muscle Proteins / Q000378:metabolism*; D018482:Muscle, Skeletal / Q000098:blood supply / Q000187:drug effects / Q000378:metabolism*; D009569:Nitric Oxide / Q000378:metabolism*; D020030:Nitric Oxide Donors / Q000008:administration & dosage; D009599:Nitroprusside / Q000008:administration & dosage; D010649:Phenylalanine / Q000378:metabolism; D012039:Regional Blood Flow; D013997:Time Factors
chemical_list: D000596:Amino Acids; D001786:Blood Glucose; D007328:Insulin; D009124:Muscle Proteins; D020030:Nitric Oxide Donors; D009599:Nitroprusside; D009569:Nitric Oxide; D010649:Phenylalanine