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Menopause and hypertension are associated with macro- and microvascular endothelial dysfunction at rest. Arginine deficiency and low nitric oxide (NO) synthesis may contribute to reduced muscle blood flow (BF) and oxygen delivery to exercising muscles. Improving BF to calf muscles may enhance physical activity. L-Citrulline supplementation (CIT) has improved resting macrovascular endothelial function via increased arginine availability for NO synthesis. Thus, the purpose of this study was to examine the effects of CIT on resting microvascular endothelial function and BF responses to plantarflexion exercise (PFE) in hypertensive postmenopausal women. We hypothesized that CIT would improve microvascular function and BF responses to PFE compared to placebo (PL). Twenty-one hypertensive postmenopausal women were randomized to 4 weeks of CIT (10g/day, n=10) or PL ( n=11). Superficial femoral macro- (flow-mediated dilation; FMD) and microvascular function (5s average peak blood velocity and flow during reperfusion) were assessed by ultrasound at 0 and 4 weeks. Femoral artery BF and vascular conductance (VC) were measured via ultrasound at rest and during 3-minute stages of rhythmic PFE at 5%, 15%, and 30% of 1-repetition maximum (1RM) at 0 and 4 weeks. BF and VC responses to PFE were analyzed as the change from rest to the last minute of each stage. There were no differences between groups in FMD, 5s peak velocity and flow during reperfusion, and vascular responses to PFE at 0 weeks. CIT significantly increased FMD (CIT:Δ1.28 ± 0.42 vs PL:Δ0.01 ± 0.40%, p = 0.04) and 5s peak velocity (CIT:Δ17.44 ± 4.21 vs PL:Δ0.09 ± 4.01 cm/s, p = 0.01) and flow (CIT:Δ220 ± 54 vs PL:Δ35 ± 51 mL/min, p = 0.02) during reperfusion compared to PL. CIT had no effect on BF and VC responses to 5% PFE ( p > 0.05). CIT significantly augmented BF responses to 15% PFE (CIT:Δ82 ± 16 vs PL:Δ22 ± 15 mL/min, p 0.05). Improvements in 5s peak velocity were positively correlated with BF responses to 15% PFE ( r = 0.498, p = 0.02) and 30% PFE ( r = 0.532, p = 0.01), and with VC responses to 15% PFE ( r = 0.542, p = 0.01) and 30% PFE ( r = 0.633, p < 0.01). Similarly, augmented 5s flow was positively correlated with BF ( r = 0.461, p = 0.04) and VC ( r = 0.558, p = 0.01) responses to 30% PFE. These findings indicate that CIT improved superficial femoral artery macro- and microvascular endothelial function at rest. However, only improvements in microvascular endothelial function influenced vascular function during leg exercise in hypertensive postmenopausal women. This is the full abstract presented at the American Physiology Summit 2024 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.
Dillon et al. (Wed,) studied this question.