IADR Abstract Archives
Oral Nitrate Metabolism and Cardiometabolic Health
Objectives: Commensal oral bacteria reduce exogenous (dietary) and endogenous nitrate to nitrite, which is converted to nitric oxide (NO), a signaling molecule involved in endothelial function, blood pressure regulation, and insulin sensitivity. Nitrite can also be further reduced by oral bacteria into ammonia via the Dissimilatory Nitrate Reduction to Ammonia (DNRA) pathway, which could impact systemic NO bioavailability. This pilot study aimed to assess the nitrate reducing capacity of the salivary microbiome with respect to systemic NO bioavailability and cardiometabolic health.
Methods: Twenty participants from the San Juan Overweight Adults Longitudinal Study (SOALS) were randomly sampled within strata defined by mouthwash use (never vs. >twice/day) and metabolic syndrome. We sampled five participants in each of the four strata, and measured bacterial enzymatic activities related to oral nitrate reduction in their saliva. Nitrate reductase (nmolesNO2/min/mg) and DNRA (nmolesNH3/min/mg) activities in saliva were assessed by measuring nitrite and ammonia generation from nitrate. Nitrite and nitrate were measured by HPLC-coupled to the Griess reaction (Eicom). Clinical oral and cardiometabolic health data were collected earlier in SOALS.
Results: DNRA (0.89 vs. 0.13, p=0.07) and nitrate reductase activities (0.95 vs. 0.31, p=0.08) were lower in participants with metabolic syndrome compared to without. Both enzymatic activities correlated significantly with the amount of plaque (DNRA r=0.49 and nitrate reductase r=0.65 ). Serum nitrite-to-nitrate ratio was significantly lower among metabolic syndrome positive participants who used mouthwash >twice/day compared to people who did not use mouthwash (0.06 vs. 0.15). The ratio of ammonia to nitrite showed a mean of 1.07 ± 1.67 (SD), and a high range (min:0, max:6.02 ), indicating considerable variability among participants with respect to the proportion of the orally reduced nitrate that can become systemic NO.
Conclusions: The nitrate metabolizing pathways of oral bacteria need to be better characterized, as they could significantly impact NO bioavailability and cardiometabolic health.
Methods: Twenty participants from the San Juan Overweight Adults Longitudinal Study (SOALS) were randomly sampled within strata defined by mouthwash use (never vs. >twice/day) and metabolic syndrome. We sampled five participants in each of the four strata, and measured bacterial enzymatic activities related to oral nitrate reduction in their saliva. Nitrate reductase (nmolesNO2/min/mg) and DNRA (nmolesNH3/min/mg) activities in saliva were assessed by measuring nitrite and ammonia generation from nitrate. Nitrite and nitrate were measured by HPLC-coupled to the Griess reaction (Eicom). Clinical oral and cardiometabolic health data were collected earlier in SOALS.
Results: DNRA (0.89 vs. 0.13, p=0.07) and nitrate reductase activities (0.95 vs. 0.31, p=0.08) were lower in participants with metabolic syndrome compared to without. Both enzymatic activities correlated significantly with the amount of plaque (DNRA r=0.49 and nitrate reductase r=0.65 ). Serum nitrite-to-nitrate ratio was significantly lower among metabolic syndrome positive participants who used mouthwash >twice/day compared to people who did not use mouthwash (0.06 vs. 0.15). The ratio of ammonia to nitrite showed a mean of 1.07 ± 1.67 (SD), and a high range (min:0, max:6.02 ), indicating considerable variability among participants with respect to the proportion of the orally reduced nitrate that can become systemic NO.
Conclusions: The nitrate metabolizing pathways of oral bacteria need to be better characterized, as they could significantly impact NO bioavailability and cardiometabolic health.