Role of the Oral Microbiome in Blood Pressure Regulation in Pregnancy
Research type
Research Study
Full title
Investigation of the oral microbiome in pregnancy - do differences in oral bacterial profiles and nitrate metabolism contribute to blood pressure regulation in pregnant women?
IRAS ID
246813
Contact name
Jenny Myers
Contact email
Sponsor organisation
The University of Manchester
Clinicaltrials.gov Identifier
Duration of Study in the UK
1 years, 9 months, 31 days
Research summary
Summary of Research
High blood pressure in pregnancy is associated with poor outcomes for both mum and baby, increasing the risk of pregnancy complications including pre-eclampsia, fetal growth restriction and preterm birth. The development of new blood pressure lowering interventions suitable for use in pregnancy is a key research priority.
Inorganic nitrate is a compound found in certain types of food, particularly green leafy vegetables and beetroot. Nitrate provides an important source of nitric oxide (NO), a molecule involved in keeping blood vessels healthy and regulating blood pressure. Supplementation with nitrate in the diet, using interventions such as beetroot juice, has been shown to reduce blood pressure and improve blood vessel function. Importantly, in order for dietary nitrate to have these beneficial effects, it needs to be converted in the body to nitrite, via bacteria that live in the mouth (oral bacteria). Differences in oral bacteria, and how they metabolise nitrate, are thought to influence blood pressure regulation and potentially response to dietary nitrate supplementation.
This study aims to understand (1) whether pregnant women with high blood pressure have a different composition of oral bacteria compared to healthy pregnant women and women who are not pregnant, and (2) how differences in oral bacteria affect blood pressure responses to a dose of dietary nitrate (in the form of beetroot juice).
The study will be carried out at the Maternal and Fetal Health Research Centre (MFHRC) at St Mary's Hospital, Manchester. It is funded by Tommy’s, the Baby Charity. Women will attend a single research visit, during which blood pressure will be measured, and samples of blood, saliva and tongue swabs will be taken, before and after consumption of a nitrate-rich beetroot juice drink. We will be investigating the profile of oral bacteria from all women, and relating this to their blood pressure and nitrate metabolism.
Summary of Results
High blood pressure (hypertension) in pregnancy is common, affecting up to 10% of all pregnant women. Hypertension in pregnancy is associated with significant adverse outcomes for both mother and baby, increasing the risk of pre-eclampsia, poor growth of the baby in the womb, and stillbirth. Previous studies have identified that dietary patterns associated with a high intake of green leafy vegetables reduces blood pressure, and in pregnancy this dietary pattern has been associated with a lower risk of pre-eclampsia and improved growth of the baby. This project is exploring the link between diet and blood pressure, with a focus on the role of a compound called nitrate, which is abundant in green leafy vegetables and beetroot.
In non-pregnant adults, many studies have shown that supplementation with nitrate-rich beetroot juice lowers blood pressure. Our previous feasibility study found that supplementation with beetroot juice may also lower blood pressure in pregnant women, however different women showed very variable blood pressure responses to the same dose of nitrate. It was hypothesised that this may be related to the way different women can metabolise and use nitrate in the body. Certain bacteria that live in the mouth (oral bacteria) play an important role in nitrate metabolism, and therefore the aim of the present study was to investigate the link between oral bacteria, nitrate metabolism and blood pressure regulation in women. To do this, we profiled the oral bacteria in women with both normal and high blood pressure, measured their ability to metabolise nitrate, and related these factors to their blood pressure regulation. Through this work, we aimed to determine whether differences in oral bacteria are associated with blood pressure in women, and ultimately whether we can use dietary supplementation strategies to improve blood pressure regulation in pregnant women in the future.
Our results have shown evidence of altered nitrate metabolism in hypertensive women. Women with high blood pressure had reduced levels of nitrate-reducing bacteria on the surface of the tongue, and we found that the activity of nitrate-reducing bacteria in the mouth was associated with the resting blood pressure of study participants. We also explored the links between habitual intake of dietary nitrate and nitrate-reducing activity, which suggested that higher a woman's intake of nitrate-containing vegetables, the higher her oral nitrate reducing bacteria. Overall, this study provides evidence that the oral bacterial profile is different in women with hypertension, and that supplementation with dietary nitrate may be able to beneficially alter oral bacteria. These data will pave the way for a larger clinical trial aiming to find out whether daily supplementation with beetroot juice may lower the burden of high blood pressure during pregnancy and the role of oral bacteria in this treatment approach.
REC name
North West - Greater Manchester East Research Ethics Committee
REC reference
19/NW/0069
Date of REC Opinion
16 Apr 2019
REC opinion
Further Information Favourable Opinion