Altered Oral Nitrate Reduction and Bacterial Profiles in Hypertensive Women Predict Blood Pressure Lowering Following Acute Dietary Nitrate Supplementation

Background: The efficacy of dietary nitrate supplementation to lower blood pressure (BP) in pregnant women is highly variable. We aimed to investigate whether differences in oral microbiota profiles and oral nitrate-reducing capacity may explain inter-individual differences in BP lowering following nitrate supplementation.

Methods: Participants recruited for this study were both pregnant and non-pregnant women, with or without hypertension (N=55). Following an overnight fast, plasma, saliva and tongue scraping samples were collected for measurement of nitrate/nitrite concentrations, oral nitrate-reductase (NaR) activity and microbiota profiling using 16S rRNA gene sequencing. Baseline BP was measured, followed by the administration of a single dose of dietary nitrate (400mg nitrate in 70mL beetroot juice). Post-nitrate intervention, plasma and salivary nitrate/nitrite concentrations and BP were determined 2.5 hours later.

Results: Women with hypertension had significantly lower salivary nitrite concentrations (p=0.006) and reduced abundance of the nitrate-reducing taxa Veillonella (p=0.007) compared with normotensive women. Oral NaR activity was not significantly different in pregnant versus non-pregnant women (p=0.991) but tended to be lower in hypertensive compared with normotensive women (p=0.099). Oral NaR activity was associated with both baseline diastolic BP (p=0.050) and change in diastolic BP following acute nitrate intake (p=0.01, adjusted for baseline BP).

Conclusions: The abundance and activity of oral nitrate-reducing bacteria impact both baseline BP as well as the ability of dietary nitrate supplementation to lower BP. Strategies to increase oral nitrate-reducing capacity could lower BP and enhance the efficacy of dietary nitrate supplementation, in pregnancy as well as in non-pregnant adults.