High Altitude Adaptation in Tibetans

Abstract

Since the beginning of the Himalayan climbing era, the anecdotal extraordinary physical performance at high altitude of Sherpas and Tibetans has intrigued scientists interested in altitude adaptation. These ethnic groups may have been living at high altitude for longer than any other population, and the hypothesis of a possible evolutionary genetic adaptation to altitude makes sense. Reviewed here is the evidence as to whether Tibetans are indeed better adapted for life and work at high altitude as compared to other populations and, if so, whether this better adaptation might be inborn. Tibetans, compared to lowlanders, maintain higher arterial oxygen saturation at rest and during exercise and show less loss of aerobic performance with increasing altitude. Tibetans have greater hypoxic and hypercapnic ventilatory responsiveness, larger lungs, better lung function, and greater lung diffusing capacity than lowlanders. Blood hemoglobin concentration is lower in Tibetans than in lowlanders or Andeans living at similar altitudes. Tibetans develop only minimal hypoxic pulmonary hypertension and have higher levels of exhaled nitric oxide than lowlanders or Andeans. Tibetans' sleep quality at altitude is better and they desaturate less at night. Several of these findings are also found in Tibetans born at low altitude when exposed for the first time to high altitude once adult. In conclusion, Tibetans indeed seem better adapted to life and work at high altitude, and this superior adaptation may very well be inborn, even though its exact genetic basis remains to be elucidated.

Correlation between single nucleotide polymorphisms in hypoxia-related genes and susceptibility to acute high-altitude pulmonary edema

“…Tibetans show greater adaptability to the hypoxic environment of high-altitude regions compared to people belonging to the Han ethnicity; the incidence of HAPE was significantly less in Tibetans compared to that observed in people belonging the Han ethnicity (Cheng et al, 1997;Basu et al, 2007). Genetic factors accounted for approximately 50% of the factors influencing the adaptation of the human body to highaltitude hypoxic environments (Wu et al, 2005;Wu and Kayser, 2006). In this study, 10 susceptibility genes related to HAPE were identified/screened from the NCBI database; these genes coded for aldosterone synthase 2 (CYP11B2), ACE, heat-shock protein-70 (HSP70), nuclear factor-kappa B (NF-κB), SP-A2, NOS,VEGF,prolyl hydroxylase (EGLN1), and the zinc finger protein A20.…”

Phenotypic plasticity and genetic adaptation to high-altitude hypoxia in vertebrates

“…Populations at high altitude could therefore benefit from enhancing the facilitatory mechanisms or suppressing the inhibitory ones. Some highland species or populations are characterized by a heightened acute hypoxic ventilatory response, a more effective breathing pattern, a maintained acclimatization response, and/or a prevention of hypoxic desensitization (Black and Tenney, 1980;Beall et al, 1997;Wu and Kayser, 2006;Brutsaert, 2007;Scott and Milsom, 2007;Pichon et al, 2009). The underlying chemoreceptive mechanisms are not necessarily convergent at the cellular level.…”

“…However, pulmonary O 2 diffusion capacity can be enhanced further in some high-altitude adapted groups that have larger lungs than lowlanders (Brutsaert et al, 1999;Wu and Kayser, 2006;Brutsaert, 2007;Scott et al, 2010). This is particularly true in birds because their lungs are rigid and are ventilated by air sacs.…”

Prostate stem cell antigen rs2294008 polymorphism differentially contributes to Helicobacter pylori-negative gastric cancer among various populations in China

“…The rs2294008 CT and TT genotypes were similar in the Tibet (39.51%, 6.64, respectively) and Han (40.86%, 7.14, respectively) populations, but were significantly lower than those of the Hui population (46.03%, 13.02, respectively). The Han nationality constitutes the majority population, while Tibetans are a minority in the Qinghai area in China, with both groups having resided in a high-altitude area for a long period of time, thus their physical and physiological functions have altered to adapt to hypoxic environments (38). A recent study has identified that advantageous gene variations are associated with human adaptation at high altitudes (39), thus, genetic susceptibility of the Tibet and Han populations may yield different results from Han populations only.…”