AbstractFollowing a single blind, cross-over and non-randomized design we investigated the effect of 7-day use of chlorhexidine (CHX) mouthwash on the salivary microbiome as well as several saliva and plasma biomarkers in 36 healthy individuals. They rinsed their mouth (for 1 min) twice a day for seven days with a placebo mouthwash and then repeated this protocol with CHX mouthwash for a further seven days. Saliva and blood samples were taken at the end of each treatment to analyse the abundance and diversity of oral bacteria, and pH, lactate, glucose, nitrate and nitrite concentrations. CHX significantly increased the abundance of Firmicutes and Proteobacteria, and reduced the content of Bacteroidetes, TM7, SR1 and Fusobacteria. This shift was associated with a significant decrease in saliva pH and buffering capacity, accompanied by an increase in saliva lactate and glucose levels. Lower saliva and plasma nitrite concentrations were found after using CHX, followed by a trend of increased systolic blood pressure. Overall, this study demonstrates that mouthwash containing CHX is associated with a major shift in the salivary microbiome, leading to more acidic conditions and lower nitrite availability in healthy individuals.

Abstract
. Purpose
. The present study investigated different doses of ultraviolet-A (UV-A) light on plasma nitric oxide metabolites and cardiorespiratory variables.
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. Methods
. Ten healthy male participants completed three experimental conditions, 7 days apart. Participants were exposed to no light (CON); 10 J cm2 (15 min) of UV-A light (UVA10) and 20 J cm2 (30 min) of UV-A light (UVA20) in a randomized order. Plasma nitrite [NO2−] and nitrate [NO3−] concentrations, blood pressure (BP), and heart rate (HR) were recorded before, immediately after exposure and 30 min post-exposure. Whole body oxygen utilization ($${{\dot{V}}}{\rm O}_{2}$$
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. ), resting metabolic rate (RMR) and skin temperature were recorded continuously.
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. Results
. None of the measured parameters changed significantly during CON (all P > 0.05). $${{\dot{V}}}{\rm O}_{2}$$
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. and RMR were significantly reduced immediately after UVA10 (P < 0.05) despite no change in plasma [NO2−] (P > 0.05). Immediately after exposure to UVA20, plasma [NO2−] was higher (P = 0.014) and $${{\dot{V}}}{\rm O}_{2}$$
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. and RMR tended to be lower compared to baseline (P = 0.06). There were no differences in [NO2−] or $${{\dot{V}}}{\rm O}_{2}$$
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. at the 30 min time point in any condition. UV-A exposure did not alter systolic BP, diastolic BP or MAP (all P > 0.05). UV-A light did not alter plasma [NO3−] at any time point (all P > 0.05).
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. Conclusions
. This study demonstrates that a UV-A dose of 20 J cm2 is necessary to increase plasma [NO2−] although a smaller dose is capable of reducing $${{\dot{V}}}{\rm O}_{2}$$
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. and RMR at rest. Exposure to UV-A did not significantly reduce BP in this cohort of healthy adults. These data suggest that exposure to sunlight has a meaningful acute impact on metabolic function.
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