Key result
Chronic mountain sickness links to exaggerated iron-catalyzed oxidative-nitrosative stress and vascular impairment.
Why the study?
To better define the underlying mechanisms and vascular consequences of elevated systemic oxidative-nitrosative stress and reduced nitric oxide bioavailability in chronic mountain sickness.
Does chronic mountain sickness and high-altitude exposure increase systemic oxidative-nitrosative stress and impair vascular function?
Observational (n=30)
Does chronic mountain sickness and high-altitude exposure increase systemic oxidative-nitrosative stress and impair vascular function?
p-value: p=<0.001
Chronic mountain sickness is associated with exaggerated iron-catalysed systemic oxidative-nitrosative stress and dietary antioxidant deficiency, which correlate with impaired systemic vascular function and structure.
May link chronic mountain sickness to vascular impairment via oxidative stress; hypothesis-generating and should not yet change practice.
Chronic mountain sickness (CMS) is a high-altitude (HA) maladaptation syndrome characterised by elevated systemic oxidative-nitrosative stress (OXNOS) due to a free radical-mediated reduction in vascular nitric oxide (NO) bioavailability. To better define underlying mechanisms and vascular consequences, this study compared healthy male lowlanders (80 m, n = 10) against age/sex-matched highlanders born and bred in La Paz, Bolivia (3600 m) with (CMS+, n = 10) and without (CMS-, n = 10) CMS. Cephalic venous blood was assayed using electron paramagnetic resonance spectroscopy and reductive ozone-based chemiluminescence. Nutritional intake was assessed via dietary recall. Systemic vascular function and structure were assessed via flow-mediated dilatation, aortic pulse wave velocity and carotid intima-media thickness using duplex ultrasound and applanation tonometry. Basal systemic OXNOS was permanently elevated in highlanders (P = <0.001 vs. lowlanders) and further exaggerated in CMS+, reflected by increased hydroxyl radical spin adduct formation (P = <0.001 vs. CMS-) subsequent to liberation of free 'catalytic' iron consistent with a Fenton and/or nucleophilic addition mechanism(s). This was accompanied by elevated global protein carbonylation (P = 0.046 vs. CMS-) and corresponding reduction in plasma nitrite (P = <0.001 vs. lowlanders). Dietary intake of vitamins C and E, carotene, magnesium and retinol were lower in highlanders and especially deficient in CMS + due to reduced consumption of fruit and vegetables (P = <0.001 to 0.028 vs. lowlanders/CMS-). Systemic vascular function and structure were also impaired in highlanders (P = <0.001 to 0.040 vs. lowlanders) with more marked dysfunction observed in CMS+ (P = 0.035 to 0.043 vs. CMS-) in direct proportion to systemic OXNOS (r = -0.692 to 0.595, P = <0.001 to 0.045). Collectively, these findings suggest that lifelong exposure to iron-catalysed systemic OXNOS, compounded by a dietary deficiency of antioxidant micronutrients, likely contributes to the systemic vascular complications and increased morbidity/mortality in CMS+. TRIAL REGISTRY: ClinicalTrials.gov; No: NCT01182792; URL: www.clinicaltrials.gov.
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Bailey et al. (2022) conducted an observational in Chronic mountain sickness (n=30). High-altitude exposure and chronic mountain sickness vs. Lowlanders and highlanders without chronic mountain sickness was evaluated on Basal systemic oxidative-nitrosative stress (OXNOS) (p=<0.001). Highlanders with chronic mountain sickness exhibited exaggerated iron-catalysed systemic oxidative-nitrosative stress (P<0.001 vs CMS-) and impaired vascular function.
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