Abstract
Dietary nitrate (NIT) supplementation consistently results in reduced blood pressure (BP) and improved endothelial function due to an increase in nitric oxide (NO) bioavailability. Recent studies show that exposure to UVA light also increases NO metabolites that are associated with decreased BP; however no study has yet examined the effects of combined UVA light and NIT on BP and endothelial function.
PURPOSE: To determine the effects of UVA light and NIT supplementation, alone and in combination, on aortic and brachial BP and endothelial function.
METHODS: Ten healthy males completed baseline measurements and four trials preceded by a NIT dose (~8 mmol nitrate) or a NIT depleted placebo (PLA) 2.75 h prior to exposure to either a UVA light source (UVA) or a sham light condition (SHAM) in a randomised crossover design (PLA + SHAM, PLA + UVA, NIT + SHAM, NIT + UVA). Brachial BP was measured by the auscultatory method prior to light exposure and, following 20 min of UVA or SHAM irradiation, endothelial function was assessed by flow mediated dilation (FMD) (n=6), brachial BP measured and aortic BP estimated using aortic pulse wave analysis (~3.25 h post supplementation). Differences between conditions were established by two-way ANOVA and paired t-tests. The magnitude of the difference was assessed by Cohen’s effect size.
RESULTS: There was no difference in brachial or aortic systolic BP (SBP) between baseline (122 ± 10 mmHg; 106 ± 14 mmHg) and PLA + SHAM (121 ± 8 mmHg; 105 ± 8 mmHg). Brachial SBP was lower in the three other trials (PLA + UVA, 116 ± 5 mmHg; P=0.009 d=0.59; NIT + Sham, 116 ± 8 mmHg, P=0.022 d=0.58; Nit + UVA, 114 ± 6 mmHg, P<0.001 d=0.72) and aortic SBP tended to be lower (PLA + UVA, 100 ± 9 mmHg; d=0.39; NIT + Sham, 99 ± 10 mmHg, d=0.47; NIT + UVA, 100 ± 7 mmHg, d=0.39). Diastolic pressure was not changed in any trial, however, brachial mean arterial pressure (MAP) was reduced following NIT + UVA (P=0.026, d=0.70). There was no difference in FMD response between conditions (P=0.455).
CONCLUSION: Acute exposure to UVA light or ingestion of NIT results in a physiologically significant reduction in brachial and aortic SBP despite no effect on FMD derived endothelial function. For the first time, we demonstrate that combining ingestion of NIT with exposure to UVA light results in a larger reduction in brachial SBP and MAP than either method alone.
PURPOSE: To determine the effects of UVA light and NIT supplementation, alone and in combination, on aortic and brachial BP and endothelial function.
METHODS: Ten healthy males completed baseline measurements and four trials preceded by a NIT dose (~8 mmol nitrate) or a NIT depleted placebo (PLA) 2.75 h prior to exposure to either a UVA light source (UVA) or a sham light condition (SHAM) in a randomised crossover design (PLA + SHAM, PLA + UVA, NIT + SHAM, NIT + UVA). Brachial BP was measured by the auscultatory method prior to light exposure and, following 20 min of UVA or SHAM irradiation, endothelial function was assessed by flow mediated dilation (FMD) (n=6), brachial BP measured and aortic BP estimated using aortic pulse wave analysis (~3.25 h post supplementation). Differences between conditions were established by two-way ANOVA and paired t-tests. The magnitude of the difference was assessed by Cohen’s effect size.
RESULTS: There was no difference in brachial or aortic systolic BP (SBP) between baseline (122 ± 10 mmHg; 106 ± 14 mmHg) and PLA + SHAM (121 ± 8 mmHg; 105 ± 8 mmHg). Brachial SBP was lower in the three other trials (PLA + UVA, 116 ± 5 mmHg; P=0.009 d=0.59; NIT + Sham, 116 ± 8 mmHg, P=0.022 d=0.58; Nit + UVA, 114 ± 6 mmHg, P<0.001 d=0.72) and aortic SBP tended to be lower (PLA + UVA, 100 ± 9 mmHg; d=0.39; NIT + Sham, 99 ± 10 mmHg, d=0.47; NIT + UVA, 100 ± 7 mmHg, d=0.39). Diastolic pressure was not changed in any trial, however, brachial mean arterial pressure (MAP) was reduced following NIT + UVA (P=0.026, d=0.70). There was no difference in FMD response between conditions (P=0.455).
CONCLUSION: Acute exposure to UVA light or ingestion of NIT results in a physiologically significant reduction in brachial and aortic SBP despite no effect on FMD derived endothelial function. For the first time, we demonstrate that combining ingestion of NIT with exposure to UVA light results in a larger reduction in brachial SBP and MAP than either method alone.
| Original language | English |
|---|---|
| Pages (from-to) | 751 |
| Number of pages | 1 |
| Journal | Medicine and Science in Sports and Exercise |
| Volume | 46 |
| Issue number | 5s |
| DOIs | |
| Publication status | Published - May 2014 |