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

Abstract

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 interindividual differences in BP lowering following nitrate supplementation. METHODS: Participants recruited for this study were both pregnant and nonpregnant 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 NaR (nitrate reductase) activity, and microbiota profiling using 16S rRNA gene sequencing. Baseline BP was measured, followed by the administration of a single dose of dietary nitrate (400 mg nitrate in 70 mL 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 nonpregnant 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 nonpregnant adults. REGISTRATION: URL: https://www.clinicaltrials.gov ; Unique identifier: NCT03930693.