Relationship between plasma nitric oxide concentration and insulin resistance in essential hypertension

Background Plasma nitric oxide (NOx) concentrations in patients with essential hypertension (EH) have been reported to be higher, lower, or no different than in normotensives. This study was initiated to determine whether these inconsistent findings were related to differences in insulin resistance. Methods Fasting plasma NOx and insulin concentrations were measured in 78 patients with EH and the relationship between these variables evaluated by regression analysis. Patients with hypertension were also divided into tertiles based on their fasting plasma insulin concentration: the highest tertile classified as insulin resistant (EH-IR) and the lowest as insulin sensitive (EH-IS). Plasma NOx concentrations were compared among these two groups and a third group of 21 normotensive, insulin resistant (N-IR) individuals by one-way ANOVA. Results Plasma insulin and NOx concentrations were correlated (r = 0.31, P< .01) in patients with hypertension, independently of differences in age, body mass index, waist circumference, and blood pressure. Plasma NOx concentrations were different in the three experimental groups (P< .001), being significantly higher (P< .05) in the EH-IR than in either of the other two groups. Despite being hyperinsulinemic, NOx levels in N-IR individuals were lower than in EH-IR subjects and no different from EH-IS individuals. Conclusions Plasma NOx concentrations are highest in those patients with EH who are also insulin resistant/hyperinsulinemic (EH-IR). Furthermore, because plasma NOx concentrations were as high in the EH-IS as in the N-IR populations, it could be speculated that plasma NOx concentrations are also modulated by EH, per se.