Abstract

Dietary NO₃⁻ (nitrate) and NO₂⁻ (nitrite) support ˙NO (nitric oxide) generation and downstream vascular signaling responses. These nitrogen oxides also generate secondary nitrosating and nitrating species that react with low molecular weight thiols, heme centers, proteins, and unsaturated fatty acids. To explore the kinetics of NO₃⁻and NO₂⁻metabolism and the impact of dietary lipid on nitrogen oxide metabolism and cardiovascular responses, the stable isotopes Na¹⁵NO₃ and Na¹⁵NO₂ were orally administered in the presence or absence of conjugated linoleic acid (cLA). The reduction of ¹⁵NO₂⁻ to ¹⁵NO was indicated by electron paramagnetic resonance spectroscopy detection of hyperfine splitting patterns reflecting ¹⁵NO-deoxyhemoglobin complexes. This formation of ¹⁵NO also translated to decreased systolic and mean arterial blood pressures and inhibition of platelet function. Upon concurrent administration of cLA, there was a significant increase in plasma cLA nitration products 9- and 12-¹⁵NO₂-cLA. Coadministration of cLA with ¹⁵NO₂⁻ also impacted the pharmacokinetics and physiological effects of ¹⁵NO₂⁻, with cLA administration suppressing plasma NO₃⁻and NO₂⁻levels, decreasing ¹⁵NO-deoxyhemoglobin formation, NO₂⁻inhibition of platelet activation, and the vasodilatory actions of NO₂⁻, while enhancing the formation of 9- and 12-¹⁵NO₂-cLA. These results indicate that the biochemical reactions and physiological responses to oral ¹⁵NO₃⁻and ¹⁵NO₂⁻are significantly impacted by dietary constituents, such as unsaturated lipids. This can explain the variable responses to NO₃⁻and NO₂⁻supplementation in clinical trials and reveals dietary strategies for promoting the generation of pleiotropic nitrogen oxide-derived lipid signaling mediators.