Effect of acute nitrate and citrulline supplementation on muscle microvascular response to ischemia-reperfusion in healthy humans.

Abstract

Nitric oxide (NO) is implicated in vasomotor control mechanisms altering the diameter of the vessels under various physiological and pathological conditions. There are 2 main NO production pathways, 1 NO synthase (NOS) independent (nitrate-nitrite-NO) and the other is NOS dependent (citrulline-arginine-NO). The objective of the study was to evaluate the effect of acute nitrate and citrulline supplementation on post-ischemic vascular response in healthy subjects. Fourteen subjects performed 2-leg vascular occlusion tests, 3 days apart. They were randomly assigned to consume a drink containing 1200 mg (19.4 mmol) of nitrate and 6 g of citrulline (N+C) or a placebo (Pl). Changes in total hemoglobin (Hbtot) and oxyhemoglobin (HbO2) concentrations were recorded by near-infrared spectroscopy on the thigh and calf muscles. No differences between N+C and Pl were observed during the ischemic period. Hbtot increased to a larger extent during the reperfusion period for the thigh (e.g., area under the curve, 821 ± 324 vs. 627 ± 381 mmol·s-1, p = 0.003) and the calf (515 ± 285 vs. 400 ± 275 mmol·s-1, p = 0.029) in the N+C versus Pl conditions. Similar results were found regarding HbO2 for the thigh (e.g., area under the curve, 842 ± 502 vs. 770 ± 491 mmol·s-1, p = 0.077) and the calf (968 ± 536 vs. 865 ± 275 mmol·s-1, p = 0.075). The larger postocclusive Hbtot and HbO2 responses observed after N+C intake suggests a greater post-ischemic vasodilation, which may be due to increased NO availability, via the activation of the 2 main NO production pathways.