| Summary: | Aging and menopause are associated with decreased nitric oxide bioavailability due to reduced L-arginine (L-ARG) levels contributing to endothelial dysfunction (ED). ED precedes arterial stiffness and hypertension development, a major risk factor for cardiovascular disease. This study investigated the effects of L-citrulline (L-CIT) on endothelial function, aortic stiffness, and resting brachial and aortic blood pressures (BP) in hypertensive postmenopausal women. Twenty-five postmenopausal women were randomized to 4 weeks of L-CIT (10 g) or placebo (PL). Serum L-ARG, brachial artery flow-mediated dilation (FMD), aortic stiffness (carotid-femoral pulse wave velocity, cfPWV), and resting brachial and aortic BP were assessed at 0 and 4 weeks. L-CIT supplementation increased L-ARG levels (Δ13 ± 2 vs. Δ−2 ± 2 µmol/L, <i>p</i> < 0.01) and FMD (Δ1.4 ± 2.0% vs. Δ−0.5 ± 1.7%, <i>p</i> = 0.03) compared to PL. Resting aortic diastolic BP (Δ−2 ± 4 vs. Δ2 ± 5 mmHg, <i>p</i> = 0.01) and mean arterial pressure (Δ−2 ± 4 vs. Δ2 ± 6 mmHg, <i>p</i> = 0.04) were significantly decreased after 4 weeks of L-CIT compared to PL. Although not statistically significant (<i>p</i> = 0.07), cfPWV decreased after L-CIT supplementation by ~0.66 m/s. These findings suggest that L-CIT supplementation improves endothelial function and aortic BP via increased L-ARG availability.
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