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The physiological characteristics of Andean natives living at high altitudes have been investigated extensively, with many studies reporting that Andean highlanders have a higher hemoglobin (Hb) concentration than other highlander populations. It has previously been reported that positive natural selection has acted independently on the egl-9 family hypoxia inducible factor 1 ( EGLN1 ) gene in Tibetan and Andean highlanders and is related to Hb concentration in Tibetans. However, no study has yet revealed the genetic determinants of Hb concentration in Andeans even though several single-nucleotide polymorphisms (SNPs) in EGLN1 have previously been examined. Therefore, we explored the relationship between hematological measurements and tag SNPs designed to cover the whole EGLN1 genomic region in Andean highlanders living in Bolivia. Our findings indicated that haplotype frequencies estimated from the EGLN1 SNPs were significantly correlated with Hb concentration in the Bolivian highlanders. Moreover, we found that an Andean-dominant haplotype related to high Hb level may have expanded rapidly in ancestral Andean highlander populations. Analysis of genotype data in an ~436.3 kb genomic region containing EGLN1 using public databases indicated that the population structure based on EGLN1 genetic markers in Andean highlanders was largely different from that in other human populations. This finding may be related to an intrinsic or adaptive physiological characteristic of Andean highlanders. In conclusion, the high Hb concentrations in Andean highlanders can be partly characterized by EGLN1 genetic variants., Competing Interests: On behalf of all authors, the corresponding author states that there is no conflict of interest., (Copyright © 2020 Yoshiki Yasukochi et al.)

Background: Many studies have reported specific adaptations to high altitude, but few studies have focused on physiological variations in high-altitude adaptation in Andean highlanders. This study aimed to investigate the relationships between SpO 2 and related factors, including individual variations and sex differences, in Andean highlanders., Methods: The participants were community-dwelling people in La Paz, Bolivia, aged 20 years and over (age range 20-34 years). A total of 50 men and 50 women participated in this study. Height, weight, SpO 2 , hemoglobin concentration, finger temperature, heart rate, and blood pressure were measured. Information about lifestyle was also obtained by interview., Results: There were individual variations of SpO 2 both in men (mean 89.9%, range 84.0-95.0%) and women (mean 91.0%, range 84.0-96.0%). On Student's t test, men had significantly lower heart rate (p = 0.046) and SpO 2 (p = 0.030) than women. On the other hand, men had significantly higher SBP (p < 0.001), hemoglobin (p < 0.001), and finger temperature (p = 0.004). In men, multiple stepwise regression analysis showed that a higher SpO 2 was correlated with a lower heart rate (β = - 0.089, p = 0.007) and a higher finger temperature (β = 0.308, p = 0.030) (r 2 for model = 0.18). In women, a higher SpO 2 was significantly correlated with a higher finger temperature (β = 0.391, p = 0.015) (r 2 for model = 0.12). A higher SpO 2 was related to a higher finger temperature (β = 0.286, p = 0.014) and a lower heart rate (β = - 0.052, p = 0.029) in all participants (r 2 for model = 0.21). Residual analysis showed that individual SpO 2 values were randomly plotted., Conclusion: Random plots of SpO 2 on residual analysis indicated that these variations were random error, such as biological variation. A higher SpO 2 was related to a lower heart rate and finger temperature in men, but a higher SpO 2 was related to finger temperature in women. These results suggest that there are individual variations and sex differences in the hemodynamic responses of high-altitude adaptation in Andean highlanders.