Tetrahydrobiopterin supplementation enhances carotid artery compliance in healthy older men: A pilot study

Background We performed a pilot study to test the hypothesis that acute oral ingestion of tetrahydrobiopterin (BH 4), a key cofactor modulating vascular nitric oxide (NO) synthase activity, improves large elastic artery stiffness with aging in men.MethodsHealthy older (63 2 years; n = 8) and young (agE ₂5 1 years; n = 6) men were studied 3 h after ingestion of BH 4 (10 mgkg 1 body weight) or placebo on separate days in a randomized, placebo-controlled, double-blind study.ResultsBaseline carotid artery compliance was 37% lower (0.17 0.02 vs. 0.22 0.02 mm/mm Hg10 1) and Β-stiffness was 42% higher (7.3 1.1 vs. 4.2 0.5 AU) in the older men (both P 0.05). BH 4 ingestion markedly increased circulating BH 4 concentrations in both groups (17-19-fold, P 0.05), but increased compliance (39% to 0.23 0.02 mm/mm Hg. 10 1, P 0.01) and decreased Β-stiffness index (-27% to 5.3 0.7 AU, P 0.01) only in the older men. BH 4 also reduced carotid systolic blood pressure (SBP) in the older men (P 0.05).ConclusionsThese preliminary results support the possibility that limited BH 4 bioavailability contributes to impaired carotid artery compliance in healthy older men. Further studies are needed to determine if increasing BH 4 bioavailability though oral BH 4 supplementation may have therapeutic efficacy for improving large elastic artery compliance and reducing central SBP with aging.