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Citrulline ingestion did not improve the age‐associated reduction in nitric oxide synthesis (698.6)
Author(s) -
Kim IlYoung,
Schutzler Scott,
Deutz Nicolaas,
Wolfe Robert
Publication year - 2014
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.28.1_supplement.698.6
Subject(s) - ingestion , arginine , citrulline , nitric oxide , chemistry , bioavailability , medicine , endocrinology , phenylalanine , biochemistry , amino acid , pharmacology
A reduction in nitric oxide (NO) bioavailability that impairs peripheral blood flow regulation is a natural consequence of aging. Therefore , we investigated the effect of ingestion of citrulline, the precursor of arginine, on de novo arginine and NO synthesis at baseline and during citrulline ingestion. A total of 3g of citrulline was ingested every 15 min for 3 h. A 6‐h stable isotope infusion protocol was performed in young (n=8, 27 ± 1.1 y) and elderly subjects (n=8, 76.6 ± 3.1 y) using primed constant infusions of ring‐ L‐[guanidine‐ 15 N 2 ]arginine, L‐[ureido‐ 13 C,5,5‐ 2 H 2 ]citrulline,and ring‐[ 2 H 5 ]phenylalanine. Basal NO synthesis [0.32 ± 0.03 vs. 0.47 ± 0.05 μmol/kg ffm/h; p < 0.02], but not de novo arginine [12.5 ± 1.60 vs. 16.4 ± 1.47 μmol/kg ffm/h], was significantly lower in the elderly vs. the young. Citrulline ingestion increased de novo arginine synthesis in both the elderly and the young, but to a greater extent in the young [55.4 ± 9.64 vs. 72.3 ± 5.96 μmol/kg ffm/h; p < 0.01]. Citrulline ingestion increased NO synthesis in the young [3.47 ± 0.65 μmol/kg ffm/h; p < 0.01], but not in the elderly [1.26 ± 0.42 μmol/kg ffm/h; p = 0.08]. We conclude that aging reduces NO synthesis. This decrease in NO synthesis cannot be attributed to limited availability of citrulline but to the inability to synthesize NO via NOS. Grant Funding Source : NIH/NIA P30 AG028718