EFFECTS OF 2-WEEK DIETARY NITRATE SUPPLEMENTATION AND ANTIBACTERIAL MOUTHWASH TREATMENT ON RESERVOIR-EXCESS PRESSURE PARAMETERS IN HEALTHY OLDER ADULTS

Abstract

Objective: The nitrate-nitrite-nitric oxide pathway contributes to blood pressure (BP) regulation in humans. However, it is unknown if the pathway alters arterial haemodynamic parameters derived from reservoir-excess pressure analysis. We therefore determined whether an enhancement/disruption of nitrate-nitrite-nitric oxide pathway by dietary nitrate and antibacterial mouthwash, respectively, would alter reservoir-excess pressure parameters in older adults. Design and method: Healthy older adults (n = 30, 71.0 ± 2.6 yrs, 19F, 133 ± 11 mmHg for systolic BP and 70 ± 6 mmHg for diastolic BP) participated in this study. Participants were randomised to either a 2-week active nitrate treatment (BR: ∼12.4 mmol beetroot juice daily as a nitrate source) or 2-week placebo treatment (PL: nitrate-depleted beetroot juice) followed by 2-week washout. They then crossed-over to the alternate treatment which was followed by another 2-week washout. Thereafter, they completed a twice-daily antibacterial mouthwash treatment (MW) for two weeks with the aim of disrupting enterosalivary nitrate circulation. Prior to and following each 2-week treatment, reservoir-excess pressure parameters including reservoir pressure integral, excess pressure integral (INTXSP), systolic rate constant (SRC) and diastolic rate constant were obtained through radial artery tonometry along with brachial systolic and diastolic BP. Aortic pulse wave velocity (aPWV) was estimated as previously described (Hughes et al., Front Physiol 2020;11:550). Results: Circulating plasma nitrate [614 (95%CI: 545, 683) microM] and nitrite [0.51 (95%CI: 0.30, 0.72) microM] increased with BR, and decreased with MW [nitrate, -17.1 (95%CI: -28.1, -6.1) microM; nitrite, -0.03 (95%CI:-0.05, -0.01) microM]. Relative to PL, BR reduced brachial systolic BP [-2.0 (95%CI: -3.9, -0.1) mmHg], INTXSP [-0.4 (95%CI: -0.7, -0.1) mmHg·s], and aPWV [-0.2 (95%CI: -0.4, 0.0) m/s]. MW increased brachial systolic [2.0 (95%CI: 0.0, 3.9) mmHg], diastolic [1.2 (95%CI: 0.4, 2.0) mmHg] BP, and decreased SRC [-0.2 (95%CI: -0.3, 0.0) 1/s] relative to PL. Conclusions: Favourable (INTXSP with BR) and unfavourable (SRC with MW) alterations in reservoir-excess pressure parameters were observed with 2-week dietary nitrate and antibacterial mouthwash treatments, which was accompanied by a small change in brachial systolic BP. These observations may suggest a potential link between enhancing/disrupting nitrate-nitrite-nitric oxide pathway and cardiovascular health in older adults.