The effects of two different doses of ultraviolet-A light exposure on nitric oxide metabolites and cardiorespiratory outcomes

Abstract

PurposeThe present study investigated different doses of ultraviolet-A (UV-A) light on plasma nitric oxide metabolites and cardiorespiratory variables.MethodsTen 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 (), resting metabolic rate (RMR) and skin temperature were recorded continuously.ResultsNone of the measured parameters changed significantly during CON (all P > 0.05). 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 and RMR tended to be lower compared to baseline (P = 0.06). There were no differences in [NO2−] or 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).ConclusionsThis 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 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.

Systematic Review of the Effects of Ultraviolet Radiation on Markers of Metabolic Dysfunction

“…Other UVR Phototherapies Five studies were identified in which treatments with UVA and/or UVB were administered for varying lengths of time (between 1 and 12 weeks) and doses (both erythemal and suberythemal were tested) to mainly 'healthy' populations of adults [32][33][34][35] (except for those who were individuals with psoriasis 36 ) ( Table 4). In three studies, mean BMI was ≥25 kg/m 2 , [33][34][35] with BMI not reported in the other papers. 32,36 Skin type was reported in three (of the five) studies, two of which reported findings from individuals who were mainly Fitzpatrick skin types II-III.…”

“…36 Finally, in healthy young adults, reduced oxygen utilisation and metabolic rate were observed along with increases in blood nitrite, immediately (early, short-term, ≤30 min) after exposure to UVA. 35…”

Effect of Short-Term Sunlight Exposure on Blood Pressure and Pulse Rate in Vitamin D₃-Insufficient, Prehypertensive Patients: A Pilot Study

“…Considering these findings, it is plausible to assume an inverse relationship between synthesis of NO and its metabolites via sunlight exposure and plasma aldosterone levels, although we could not suggest the exact amount of NO and its metabolites synthesized via sunlight exposure. However, the evidence of NO on BP reduction is still weak, although there is a plausible impact on metabolic function [42].…”

The vitamin D-folate hypothesis in human vascular health

“…Exposure of human skin to UV-A radiation has also been proposed to acutely increase NO production (50,54,58), but it may (50,58) or may not (54) reduce blood pressure. The NO-producing effect of UV-A appears to be mediated by liberation of NO via photolysis of cutaneous nitrite stores (58) and is independent of NOS (50).…”