UBC-Nepal expedition: The use of oral antioxidants does not alter cerebrovascular function at sea level or high altitude.
Alexander B HansenDwain L EckbergNia C S LewisMichael M TymkoJoshua C TremblayMichael StembridgeDaniela Nowak-FlückHoward H CarterJacqueline K LimbergPhilip N AinsliePublished in: Experimental physiology (2018)
Hypoxia is associated with an increase in systemic and cerebral formation of free radicals and associated reactants that may be linked to impaired cerebral vascular function and neurological sequelae. To what extent oral antioxidant prophylaxis impacts cerebrovascular function in humans throughout the course of acclimatization to the hypoxia of terrestrial high altitude has not been examined. Thus, the purpose of the present study was to examine the influence of orally ingested antioxidants at clinically relevant doses (vitamins C and E and α-lipoic acid) on cerebrovascular regulation at sea level (344 m; n = 12; female n = 2 participants) and at high altitude (5050 m; n = 9; female n = 2) in a randomized, placebo-controlled and double-blinded crossover design. Hypercapnic and hypoxic cerebrovascular reactivity tests of the internal carotid artery (ICA) were conducted at sea level, and global and regional cerebral blood flow (CBF; i.e. ICA and vertebral artery) were assessed 10-12 days after arrival at 5050 m. At sea level, acute administration of antioxidants did not alter cerebral hypoxic cerebrovascular reactivity (pre versus post: 1.5 ± 0.7 versus 1.2 ± 0.8%∆CBF/-%∆SpO2; P = 0.96) or cerebral hypercapnic cerebrovascular reactivity (pre versus post: 5.7 ± 2.0 versus 5.8 ± 1.9%∆CBF/∆mmHg; P = 0.33). Furthermore, global CBF (P = 0.43) and cerebral vascular conductance (ICA P = 0.08; vertebral artery P = 0.32) were unaltered at 5050 m after antioxidant administration. In conclusion, these data show that an oral antioxidant cocktail known to attenuate systemic oxidative stress failed to alter cerebrovascular function at sea level and CBF during acclimatization to high altitude.
Keyphrases
- oxidative stress
- cerebral blood flow
- subarachnoid hemorrhage
- internal carotid artery
- cerebral ischemia
- respiratory failure
- placebo controlled
- bone mineral density
- brain injury
- anti inflammatory
- radiation therapy
- squamous cell carcinoma
- ischemia reperfusion injury
- liver failure
- hepatitis b virus
- electronic health record
- clinical trial
- deep learning
- body composition
- artificial intelligence
- postmenopausal women
- rectal cancer
- phase ii study