Effects of dietary nitrate supplementation on microvascular physiology at 4559 m altitude - A randomised controlled trial (Xtreme Alps).
Altitude
Hypoxia
Microcirculation
Nitrate
Nitric oxide
Nitrite
Journal
Nitric oxide : biology and chemistry
ISSN: 1089-8611
Titre abrégé: Nitric Oxide
Pays: United States
ID NLM: 9709307
Informations de publication
Date de publication:
01 01 2020
01 01 2020
Historique:
received:
04
07
2019
revised:
28
08
2019
accepted:
07
10
2019
pubmed:
12
10
2019
medline:
22
12
2020
entrez:
12
10
2019
Statut:
ppublish
Résumé
Native highlanders (e.g. Sherpa) demonstrate remarkable hypoxic tolerance, possibly secondary to higher levels of circulating nitric oxide (NO) and increased microcirculatory blood flow. As part of the Xtreme Alps study (a randomised placebo-controlled trial of dietary nitrate supplementation under field conditions of hypobaric hypoxia), we investigated whether dietary supplementation with nitrate could improve NO availability and microvascular blood flow in lowlanders. Plasma measurements of nitrate, nitrite and nitroso species were performed together with measurements of sublingual (sidestream dark-field camera) and forearm blood flow (venous occlusion plethysmography) in 28 healthy adult volunteers resident at 4559 m for 1 week; half receiving a beetroot-based high-nitrate supplement and half receiving an identically-tasting low nitrate 'placebo'. Dietary supplementation increased plasma nitrate concentrations 4-fold compared to the placebo group, both at sea level (SL; 19.2 vs 76.9 μM) and at day 5 (D5) of high altitude (22.9 vs 84.3 μM, p < 0.001). Dietary nitrate supplementation also significantly increased both plasma nitrite (0.78 vs. 0.86 μM SL, 0.31 vs. 0.41 μM D5, p = 0.03) and total nitroso product (11.3 vs. 19.7 nM SL, 9.7 vs. 12.3 nM D5, p < 0.001) levels both at sea level and at 4559 m. However, plasma nitrite concentrations were more than 50% lower at 4559 m compared to sea level in both treatment groups. Despite these significant changes, dietary nitrate supplementation had no effect on any measured read-outs of sublingual or forearm blood flow, even when environmental hypoxia was experimentally reversed using supplemental oxygen. In conclusion, dietary nitrate supplementation does not improve microcirculatory function at 4559 m.
Identifiants
pubmed: 31604146
pii: S1089-8603(19)30207-1
doi: 10.1016/j.niox.2019.10.004
pmc: PMC6970220
pii:
doi:
Substances chimiques
Nitrates
0
Nitrites
0
Nitroso Compounds
0
Types de publication
Journal Article
Randomized Controlled Trial
Research Support, Non-U.S. Gov't
Langues
eng
Sous-ensembles de citation
IM
Pagination
27-35Subventions
Organisme : Medical Research Council
ID : G0701115
Pays : United Kingdom
Organisme : Medical Research Council
ID : MR/P008887/1
Pays : United Kingdom
Informations de copyright
Copyright © 2019 The Authors. Published by Elsevier Inc. All rights reserved.
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