Nitrate and nitrite bioavailability in plasma and saliva: Their association with blood pressure — A systematic review and meta-analysis
Raúl Bescós, Laura Gallardo-Alfaro, Ammar W. Ashor, Lucía Rizzolo-Brime, Mario Siervo, Patricia Casas‐Agustench
Abstract
In this study, we conducted a systematic review and meta-analysis to determine plasma and salivary nitrate (NO 3 - ) and nitrite (NO 2 - ) concentrations under resting and fasting conditions in different type of individuals and their association with blood pressure levels. A total of 77 studies, involving 1,918 individuals aged 19 to 74 years (males= 906; females = 1012), which measured plasma and/or salivary NO 3 - and NO 2 - using the chemiluminescence technique, were included. Mean plasma NO 3 - and NO 2 - concentrations were 33.9 μmol/L and 158.3 nmol/L, respectively. Subgroup analyses revealed lower plasma NO 3 - and NO 2 - concentrations in individuals with cardiometabolic risk (NO 3 - : 21.2 μmol/L; 95% CI, 13.4 – 29.0; NO 2 - : 122.8 nmol/L; 95% CI, 75.3 – 138.9) compared to healthy (NO 3 - : 33.9 μmol/L; 95% CI, 29.9 – 37.9; NO 2 - : 159.5 nmol/L; 95% CI, 131.8 – 187.1; P < 0.01) and trained individuals (NO 3 - : 43.0 μmol/L; 95% CI, 13.2 – 72.9; NO 2 - : 199.3 nmol/L; 95% CI, 117.6 – 281; P < 0.01). Mean salivary NO 3 - and NO 2 - concentrations were 546.2 μmol/L and 197.8 μmol/L, respectively. Salivary NO 3 - , but no NO 2 - , concentrations were higher in individuals with cardiometabolic risk (680.0 μmol/L; 95% CI, 510.2 – 849.8; P = 0.001) compared to healthy individuals (535.9 μmol/L; 95% CI, 384.2 – 687.6). A significant positive association (coefficient, 15.4 [95% CI, 0.255 to 30.5], P = 0.046) was observed between salivary NO 3 - and diastolic blood pressure (DBP). These findings suggest that the health status is positively associated with plasma NO 3 - and NO 2 - concentrations, but the circulatory levels of these anions are not associated with blood pressure. Only salivary NO 3 - showed a significant positive association with DBP. • Plasma nitrate and nitrite concentrations were significantly higher in physically trained individuals compared to healthy active individuals and those with cardiometabolic risk. • No association was found between plasma nitrate and nitrite and blood pressure levels. • Salivary nitrate concentrations were elevated in individuals with cardiometabolic risk compared with healthy active individuals, and positively associated with diastolic blood pressure. Salivary and plasma nitrate levels were positively associated.