Post-exercise hypotension and skeletal muscle oxygenation is regulated by nitrate-reducing activity of oral bacteria

Free Radic Biol Med. 2019 Nov 1;143:252-259. doi: 10.1016/j.freeradbiomed.2019.07.035. Epub 2019 Jul 29.

Abstract

Post-exercise hypotension (PEH) is a common physiological phenomenon leading to lower blood pressure after acute exercise, but it is not fully understood how this intriguing response occurs. This study investigated whether the nitrate-reducing activity of oral bacteria is a key mechanism to trigger PEH. Following a randomized, double blind and crossover design, twenty-three healthy individuals (15 males/8 females) completed two treadmill trials at moderate intensity. After exercise, participants rinsed their mouth with antibacterial mouthwash to inhibit the activity of oral bacteria or a placebo mouthwash. Blood pressure was measured before, 1h and 2 h after exercise. The microvascular response to a reactive hyperaemia test, as well as blood and salivary samples were taken before and 2 h after exercise to analyse nitrate and nitrite concentrations and the oral microbiome. As expected, systolic blood pressure (SBP) was lower (1 h: -5.2 ± 1.0 mmHg; P < 0.001); 2 h: -3.8 ± 1.1 mmHg, P = 0.005) after exercise compared to baseline in the placebo condition. This was accompanied by an increase of circulatory nitrite 2 h after exercise (2h: 100 ± 13 nM) compared to baseline (59 ± 9 nM; P = 0.013). Additionally, an increase in the peak of the tissue oxygenation index (TOI) during the reactive hyperaemia response was observed after exercise (86.1 ± 0.6%) compared to baseline levels (84.8 ± 0.5%; P = 0.010) in the placebo condition. On the other hand, the SBP-lowering effect of exercise was attenuated by 61% at 1 h in the recovery period, and it was fully attenuated 2 h after exercise with antibacterial mouthwash. This was associated with a lack of changes in circulatory nitrite (P > 0.05), and impaired microvascular response (peak TOI baseline: 85.1 ± 3.1%; peak TOI post-exercise: 84.6 ± 3.2%; P > 0.05). Diversity of oral bacteria did not change after exercise in any treatment. These findings show that nitrite synthesis by oral commensal bacteria is a key mechanism to induce the vascular response to exercise over the first period of recovery thereby promoting lower blood pressure and greater muscle oxygenation.

Publication types

  • Randomized Controlled Trial
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adult
  • Bacteria / drug effects
  • Bacteria / growth & development*
  • Cross-Over Studies
  • Double-Blind Method
  • Exercise*
  • Female
  • Humans
  • Hyperemia / drug therapy
  • Hyperemia / metabolism
  • Hyperemia / microbiology
  • Hyperemia / physiopathology*
  • Male
  • Mouth / drug effects
  • Mouth / microbiology*
  • Mouthwashes / pharmacology
  • Muscle, Skeletal / drug effects
  • Muscle, Skeletal / metabolism*
  • Nitrates / pharmacology*
  • Post-Exercise Hypotension / drug therapy
  • Post-Exercise Hypotension / metabolism
  • Post-Exercise Hypotension / microbiology
  • Post-Exercise Hypotension / physiopathology*
  • Saliva / drug effects
  • Saliva / microbiology

Substances

  • Mouthwashes
  • Nitrates