Citrulline ingestion did not improve the ageassociated reduction in nitric oxide synthesis (698.6)

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 6h 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[guanidine15N2]arginine, L[ureido13C,5,52H2]citrulline,and ring[2H5]phenylalanine. Basal NO synthesis [0.32 0.03 vs. 0.47 0.05 mol/kg ffm/h; p < 0.02], but not de novo arginine [12.5 1.60 vs. 16.4 1.47 mol/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 mol/kg ffm/h; p < 0.01]. Citrulline ingestion increased NO synthesis in the young [3.47 0.65 mol/kg ffm/h; p < 0.01], but not in the elderly [1.26 0.42 mol/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

Citrulline ingestion did not improve the ageassociated reduction in nitric oxide synthesis (698.6) Academic Article