Exhaled nitric oxide in ethnically diverse highâ altitude native populations: A comparative study

Abstract

ObjectivesAndean and Tibetan highâ altitude natives exhibit a high concentration of nitric oxide (NO) in the lungs, suggesting that NO plays an adaptive role in offsetting hypobaric hypoxia. We examined the exhaled NO concentration as well as partial pressure of several additional highâ altitude native populations in order to examine the possibility that this putative adaptive trait, that is, high exhaled NO, is universal.MethodsWe recruited two geographically diverse highland native populations, Tawang Monpa (TM), a Tibetan derived population in Northâ Eastern India (n = 95, sampled at an altitude of ~3,200â m), and Peruvian Quechua from the highland Andes (n = 412). The latter included three distinct subgroups defined as those residing at altitude (Qâ HAR, n = 110, sampled at 4,338â m), those born and residing at seaâ level (Qâ BSL, n = 152), and those born at altitude but migrant to seaâ level (Qâ M, n = 150). In addition, we recruited a referent sample of lowland natives of European ancestry from Syracuse, New York. Fraction of exhaled NO concentrations were measured using a NIOX NIMO following the protocol of the manufacturer.ResultsPartial pressure of exhaled nitric oxide (PENO) was significantly lower (pâ <â .05) in both highâ altitude resident groups (TM = 6.2â ±â 0.5 nmHg and Qâ HAR = 5.8â ±â 0.5 nmHg), as compared to the groups measured at sea level (USA = 14.6â ±â 0.7 nmHg, Qâ BSL = 18.9â ±â 1.6 nmHg, and Qâ M = 19.2â ±â 1.7 nmHg). PENO was not significantly different between TM and Qâ HAR (pâ <â .05).ConclusionIn contrast to previous work, we found lower PENO in populations at altitude (compared to seaâ level) and no difference in PENO between Tibetan and Andean highland native populations. These results do not support the hypothesis that high nitric oxide in human lungs is a universal adaptive mechanism of highland native populations to offset hypobaric hypoxia.