The Role of Oral Nitrate Reducing Bacteria in Cardiovascular Health: Impacts of Diet and Exercise

This thesis investigated the important role of oral bacteria in blood pressure regulation and vascular function through the NO3--NO2--NO pathway following exercise or dietary interventions. Study 1 examined the effect of antibacterial mouthwash on the oral microbiome and nitrate metabolism in vegetarians and omnivores. Notable alterations in bacterial composition were observed after mouthwash administration, including reductions in the Prevotella genus (from 27.7% to 9.6%, P = 0.001) and Actinomyces genus (from 9.5% to 5.7%, P = 0.001), along with decreases in Prevotella melaninogenica (from 18.1% to 6.2%, P = 0.001) and Rothia dentocariosa (from 0.09% to 0.04%, P = 0.001). Conversely, an increase in the genus Rothia mucilaginosa was observed in vegetarians (from 3.8% to 6.8%, P = 0.03), whereas omnivores exhibited an increase in Veillonella parvula (from 0.6% to 0.8%, P = 0.04). Changes in oral nitrate-reducing capacity, salivary pH, and lactate and glucose levels were noted, yet no significant changes in blood pressure were observed. In both dietary groups, antibacterial mouthwash led to decreases in oral nitrate-reducing capacity and salivary pH, while increasing salivary lactate and glucose. However, despite these results, no significant changes in blood pressure were observed. Study 2 explored the impact of the NO3--NO2--NO pathway on post-exercise hypotension using an antibacterial mouthwash after moderate-intensity aerobic exercise. Systolic blood pressure (SBP) decreased significantly at 60 minutes post-exercise in the placebo group (−5.2 ± 1.0 mmHg; P = 0.001), an effect attenuated by 61% with antibacterial mouthwash (−2.0 ± 1.0 mmHg; P = 0.004). This reduction persisted at 120 minutes (−3.8 ± 5.3 mmHg; P = 0.005) but was abolished with mouthwash (+0.3 ± 1.1 mmHg; P = 0.05), revealing a significant between-treatment difference (P = 0.02). Diastolic blood pressure (DBP) also declined post-exercise in the placebo condition (−2.4 ± 0.7 mmHg; P = 0.004) and was modestly attenuated with mouthwash (−1.7 ± 1.0 mmHg; P = 0.07). Reactive hyperaemia testing indicated enhanced tissue oxygenation index (TOI) post-exercise (peak TOI: 84.8% to 86.1%; P = 0.01) in the placebo condition, a response absent with mouthwash. Overall, exercise-induced improvements in rectus femoris oxygenation were significantly blunted by antibacterial mouthwash (P = 0.03). Study 3 examined the effects of exercise on oral nitrate-reducing capacity. No increase was observed post-exercise, while a significant increase occurred after a 2-hour rest (164.44 ± 149.24 µM to 199.91 ± 164.16 µM P = 0.007). Vascular function in the leg improved post-exercise, as evidenced by an increased tissue oxygenation index (75.61% ± 0.5% to 77.68% ± 2.07% P = 0.001). The salivary flow rate and buffering capacity increased after exercise and rest, respectively (P = 0.04). Finally, Study 4 revealed a substantial reduction in salivary NH₃ levels of 73.6% after antibacterial mouthwash use (P = 0.001). In summary, this thesis investigates the potential role of the oral microbiota in cardiovascular health through the NO3--NO2--NO pathway, offering insights that may inform future therapeutic approaches.

Author dc:creator

• Clarke, Craig

Contributors dc:contributor

• Raul Bescos Garcia, Mary Hickson, Desley White

Language dc:language

eng

Repository record dc:identifier

https://pearl.plymouth.ac.uk/hp-theses/30

OAI identifier oai:identifier

oai:pearl.plymouth.ac.uk:hp-theses-1032