Serum nitrate and nitrite levels in patients with hypertension and ischemic stroke depend on diet: A multicenter study

• Differences in serum NOx where associated with hypertension in patients on low NOx diet.
• Serum NOx levels are not associated with hypertension in patients on unrestricted diet.
• The highest concentrations of NOx were observed in patients with ischemic stroke.
• NOx can be used as a marker of endothelial dysfunction only in patients on low NOx diet.

ObjectivesNitric oxide, NO, is the key vasorelaxing agent produced by vascular endothelium. Stable end products of NO oxidation, nitrate and nitrite (NOx), are considered as markers of endothelial dysfunction associated with hypertension. Our goal was to compare NOx levels in patients with hypertension on controlled low nitrate diet with NOx levels in general population without dietary restrictions.Patients and methodsThe study included 1005 participants split into 8 groups: healthy subjects (n = 28) and patients with moderate (n = 37) and malignant hypertension (n = 24) on low nitrate diet; healthy subjects (n = 9) and patients with stroke (n = 44) on low nitrate diet; normotensive subjects (n = 354) and patients with elevated blood pressure (n = 430) and severe hypertension (n = 79) without dietary restrictions.ResultsIn groups with controlled low NOx diet, patients with moderate and malignant hypertension had significantly (p < 0.01) higher serum NOx versus healthy subject (66.9 ± 18.8 μM and 75.3 ± 22.7 μM versus 52.8 ± 28.8 μM, respectively). Patients with stroke had significantly (p = 0.02) higher serum NOx levels versus corresponding group of healthy subjects (106.3 ± 58.4 μM versus 71.2 ± 18.1 μM, respectively). In the absence of dietary control, differences in serum NOx levels between normotensive subjects and patients with elevated blood pressure and severe hypertension were not significant (p > 0.1).ConclusionDifferences in serum NOx concentrations are associated with severity of hypertension only in patients on low nitrate diet. The highest concentrations of NOx were observed in patients with stroke. In the absence of dietary control, NOx levels were not associated with presence or severity of hypertension.