Proceedings of The Physiological Society

Europhysiology 2018 (London, UK) (2018) Proc Physiol Soc 41, C092

Oral Communications

Nitrate-independent components of beetroot juice reduce blood pressure and improve vascular function in pregnant eNOS-/- mice

T. Tropea1, M. Wareing1, S. Greenwood1, C. Sibley1, E. Cottrell1

1. Division of Developmental Biology & Medicine, School of Medical Sciences, Faculty of Biology, Medicine and Health, University of Manchester, Manchester, United Kingdom.

Hypertension and uteroplacental insufficiency remain unsolved problems of pregnancy pathologies, such as fetal growth restriction (FGR). Nitric oxide (NO) is the main mediator of vascular adaptation to pregnancy, maintaining a high flow-low resistance system that favours oxygen and nutrient delivery to the fetus. Beetroot and green leafy vegetables, rich in nitrate, can provide an alternative source of NO. Dietary nitrate supplementation has been shown to lower blood pressure and enhance endothelial function in the non-pregnant state. We hypothesized that maternal dietary nitrate administration, via beetroot juice (BR), reduces blood pressure (BP) and improves vascular function and fetal growth in the endothelial nitric oxide synthase knockout mouse (eNOS-/-), an established model of fetal growth restriction, associated with chronic hypertension and uteroplacental vascular dysfunction. Pregnant C57Bl/6J (WT) and eNOS-/- mice were supplemented with nitrate-containing beetroot juice (BR+, ~1mmol/kg/day nitrate) in the drinking water from embryonic day (E)12.5. Control mice received either an equivalent dose of nitrate-depleted beetroot juice (BR-) or normal drinking water. Systolic BP was measured at E12.5 and E17.5 by tail cuff. Placentas and fetuses were weighed following delivery at E18.5. Endothelium-dependent relaxation to acetylcholine (Ach) was assessed in isolated maternal uterine (UtA) and mesenteric arteries (MesA) at E18.5 using wire myography. Supplementation with either BR+ or BR- decreased systolic BP (P<0.05) in eNOS-/- mice and enhanced UtA relaxation to Ach (P<0.01) in both strains, compared to water controls. Endothelial function was unaffected by treatments in MesA of eNOS-/- or WT mice. Fetuses from eNOS-/- mice were significantly smaller compared with WT dams (P<0.001) and this difference was not affected by BR+ or BR- supplementation. These data suggest that nitrate-independent components of beetroot juice lower BP and improve endothelial relaxation within the reproductive vascular system in pregnancies associated with hypertension and reduced NO bioavailability, however, these beneficial outcomes were not associated with an increase in fetal weight.

Where applicable, experiments conform with Society ethical requirements