Determination of endogenous and dietary-derived nitric oxide production in exhaled air of adult humans
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Date
2022
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Publisher
University of Namibia
Abstract
The production of nitric oxide (NO) has been demonstrated in the human body. Studies have elucidated that NO can either be produced endogenously via enzymatic action or through exogenous factors from dietary nitrate reduction. Exhaled nitric oxide (eNO) levels were also observed to be increased in inflammatory conditions, such as asthma and rhinitis, compared to normal physiological conditions. The aim of this study was to observe the production of NO in the body, the influence of dietary nitrate on eNO and factors affecting NO production. In this cross-sectional study, eNO in healthy, control participants (n=25) and compared to exhaled NO in participants with asthma (n=6) and participants with seasonal rhinitis (n=7). Exhaled NO in 20 healthy controls was also after supplementation with dietary nitrate. Asthmatic participant’s eNO concentrations (41±25 ppb) were higher compared to eNO in the control participants (12±12 ppb; p=0.04). There was no difference between eNO concentrations in participants with rhinitis (30±31 ppb) compared to control participants (12±12 ppb; p=0.21). There was also no dose-response relationship between the amount of dietary nitrate (nitrate-rich beetroot juice) and eNO concentration where eNO concentrations of 31±16 ppb, 34±31 ppb and 38±30 ppb; p=0.42 were measured for 35 mL, 70 mL and 140 mL of beetroot juice, respectively. A transient increase in eNO was observed after 30 minutes post-nitrate ingestion (20±8 ppb) compared to baseline eNO concentrations (6±5 ppb; p=0.03). The use of antibacterial mouthwash also reduced eNO concentrations post nitrate-ingestion (18±15 ppb) compared to beetroot ingestion without prior use of mouthwash (34±31 ppb; p=0.02). Exhaled NO levels were not reduced after antacid administration (p=0.791). The results of this study may indicate that the transient impact of dietary nitrate on eNO could account for the variations demonstrated in literature.
Description
A thesis submitted in full fulfilment of the requirements for the degree of Master of Science (Physiology)
Keywords
Exhaled nitric oxide, Asthma, Rhinitis, Beetroot juice, Mouthwash