Lessons in hypoxic adaptation from high-altitude populations

A comparison of quality of life between older adults living in high and low altitude areas

Background

High altitude is known to have a significant impact on human physiology and health, therefore, understanding its relationship with quality of life is an important research area. This study compared the quality of life (QOL) in older adults living in high and low altitude areas, and examined the independent correlates of QOL in those living in a high altitude area.

Methods

Older adults living in three public nursing homes in Xining (high altitude area) and one public nursing home in Guangzhou (low altitude area) were recruited. The WHOQOL-BREF was used to measure the QOL.

Results

644 older adults (male: 39.1%) were included, with 207 living in high altitude and 437 living in low altitude areas. After controlling for the covariates, older adults living in the high altitude area had higher QOL in terms of physical (P = 0.035) and social domains (P = 0.002), but had lower QOL in psychological (P = 0.009) domain compared to their counterparts living in the low altitude area. For older adults living in the high altitude area, smoking status was associated with higher social QOL (P = 0.021), good financial status was associated with higher physical QOL (P = 0.035), and fair or good health status was associated with higher physical (p < 0.001) and psychological QOL (P = 0.046), while more severe depressive symptoms were associated with lower QOL.

Conclusion

Appropriate interventions and support to improve depressive symptoms and both financial and health status should be developed for older adults living in high altitude areas to improve their QOL.

SNPs, linkage disequilibrium, and chronic mountain sickness in Tibetan Chinese

Chronic mountain sickness (CMS) is estimated at 1.2% in Tibetans living at the Qinghai-Tibetan Plateau. Eighteen single-nucleotide polymorphisms (SNPs) from nine nuclear genes that have an association with CMS in Tibetans have been analyzed by using pairwise linkage disequilibrium (LD). The SNPs included are the angiotensin-converting enzyme (rs4340), the angiotensinogen (rs699), and the angiotensin II type 1 receptor (AGTR1) (rs5186) from the renin-angiotensin system. A low-density lipoprotein apolipoprotein B (rs693) SNP was also included. From the hypoxia-inducible factor oxygen signaling pathway, the endothetal Per-Arnt-Sim domain protein 1 (EPAS1) and the egl nine homolog 1 (ENGL1) (rs480902) SNPs were included in the study. SNPs from the vascular endothelial growth factor (VEGF) signaling pathway included are the v-akt murine thymoma viral oncogene homolog 3 (rs4590656 and rs2291409), the endothelial cell nitric oxide synthase 3 (rs1007311 and rs1799983), and the (VEGFA) (rs699947, rs34357231, rs79469752, rs13207351, rs28357093, rs1570360, rs2010963, and rs3025039). An increase in LD occurred in 40 pairwise comparisons, whereas a decrease in LD was found in 55 pairwise comparisons between the controls and CMS patients. These changes were found to occur within and between signaling pathways, which suggests that there is an interaction between SNP alleles from different areas of the genome that affect CMS.

High-altitude Pulmonary Hypertension: an Update on Disease Pathogenesis and Management

High-altitude pulmonary hypertension (HAPH) affects individuals residing at altitudes of 2,500 meters and higher. Numerous pathogenic variables play a role in disease inception and progression and include low oxygen concentration in inspired air, vasculopathy, and metabolic abnormalities. Since HAPH affects only some people living at high altitude genetic factors play a significant role in its pathogenesis. The clinical presentation of HAPH is nonspecific and includes fatigue, shortness of breath, cognitive deficits, cough, and in advanced cases hepatosplenomegaly and overt right-sided heart failure. A thorough history is important and should include a search for additional risk factors for lung disease and pulmonary hypertension (PH) such as smoking, indoor air pollution, left-sided cardiac disease and sleep disordered breathing. Twelve-lead electrocardiogram, chest X-ray and echocardiography can be used as screening tools. A definitive diagnosis should be made with right-sided heart catheterization using a modified mean pulmonary artery pressure of at least 30 mm Hg, differing from the 25 mm Hg used for other types of PH. Treatment of HAPH includes descent to a lower altitude whenever possible, oxygen therapy and the use of medications such as endothelin receptor antagonists, phosphodiesterase 5 blockers, fasudil and acetazolamide. Some recent evidence suggests that iron supplementation may also be beneficial. However, it is important to note that the scientific literature lacks long-term randomized controlled data on the pharmacologic treatment of HAPH. Thus, an individualized approach to treatment and informing the patients regarding the benefits and risks of the selected treatment regimen are essential.

King of the Mountains: Tibetan and Sherpa Physiological Adaptations for Life at High Altitude

Anecdotal evidence surrounding Tibetans' and Sherpas' exceptional tolerance to hypobaric hypoxia has been recorded since the beginning of high-altitude exploration. These populations have successfully lived and reproduced at high altitude for hundreds of generations with hypoxia as a constant evolutionary pressure. Consequently, they are likely to have undergone natural selection toward a genotype (and phenotype) tending to offer beneficial adaptation to sustained hypoxia. With the advent of translational human hypoxic research, in which genotype/phenotype studies of healthy individuals at high altitude may be of benefit to hypoxemic critically ill patients in a hospital setting, high-altitude natives may provide a valuable and intriguing model. The aim of this review is to provide a comprehensive summary of the scientific literature encompassing Tibetan and Sherpa physiological adaptations to a high-altitude residence. The review demonstrates the extent to which evolutionary pressure has refined the physiology of this high-altitude population. Furthermore, although many physiological differences between highlanders and lowlanders have been found, it also suggests many more potential avenues of investigation.

VEGFA SNPs and transcriptional factor binding sites associated with high altitude sickness in Han and Tibetan Chinese at the Qinghai-Tibetan Plateau

Mountain sickness (MS) occurs among humans visiting or inhabiting high altitude environments. We conducted genetic analyses of seven single nucleotide polymorphisms (SNPs) in the promoter region of VEGFA gene for lowland (Han) and highland (Tibetan) Chinese. The seven SNPs were evaluated in Han and Tibetan patients with acute (A) and chronic (C) MS. We compared 64 patients with AMS with 64 Han unaffected with MS, as well as 48 CMS patients with 32 unaffected Tibetans. The SNPs studied are rs699947, rs34357231, rs79469752, rs13207351, rs28357093, rs1570360, and rs2010963 which are found in the promoter ranging from -2,578 to -634 bp from the transcriptional start site (TSS), respectively. Direct sequencing was used to identify individual genotypes for these SNPs. Arterial oxygen saturation of hemoglobin (SaO2) was found to be significantly associated with the rs699947, rs34357231, rs13207351, and rs1570360 SNPs in Han patients with AMS, while the rs2010963 SNP was found to approach significance in the AMS study group, but found to be significantly associated in the normal Tibetan study group. The Han and Tibetan control groups were found to diverge significantly for the rs28357093 and rs2010963 SNPs, as measured by genetic distances of 0.073 and 0.054, respectively. All the SNPs are found in transcriptional factor binding sites (TFBS), and their possible role in gene regulation was evaluated with regard to MS. MS was found to be significantly associated with these SNPs compared with their Han and Tibetan control groups, indicating that these nucleotide substitutions result in TFBS changes which apparently have a physiological effect on the development of high altitude sickness.

AKT3, ANGPTL4, eNOS3, and VEGFA associations with high altitude sickness in Han and Tibetan Chinese at the Qinghai-Tibetan Plateau

Mountain sickness (MS) occurs among humans visiting or inhabiting high altitude environments. We conducted genetic analyses of the AKT3, ANGPTL4, eNOS3 and VEGFA genes in lowland (Han) and highland (Tibetan) Chinese. Ten single nucleotide polymorphisms (SNPs) were evaluated in Han and Tibetan patients with acute (A) and chronic (C) MS. We compared 74 patients with AMS to 79 Han unaffected with MS, as well as 48 CMS patients to 31 unaffected Tibetans. The ten SNPs studied are AKT3 (rs4590656, rs2291409), ANGPTL4 (rs1044250), eNOS3 (rs1007311, rs1799983) and VEGFA (rs79469752, rs13207351, rs28357093, rs1570360, rs3025039). Direct sequencing was used to identify individual genotypes for these SNPs. Hemoglobin (Hb), hematocrit (Hct), and red blood cell count (RBC) were found to be significantly associated with the AKT3 SNP (rs4590656), Hb was found to be associated with the eNOS3 SNP (rs1007311), and RBC was found to be significantly associated with the VEGFA SNP (rs1570360) in Tibetan patients with CMS. CMS patients were found to diverge significantly for both eNOS3 SNPs as measured by genetic distance (0.042, 0.047) and for the VEGFA SNP (rs28357093) with a genetic distance of 0.078 compared to their Tibetan control group. Heart rate (HR) was found to be significantly associated with the eNOS3 SNP (rs1799983) and arterial oxygen saturation of hemoglobin (SaO2) was found to be significantly associated with the VEGFA SNPs (rs13207351, rs1570360) in Han patients with AMS. The Han and Tibetan control groups were found to diverge significantly for the ANGPTL4 SNP and VEGFA SNP (rs28357093), as measured by genetic distances of 0.049 and 0.073, respectively. Seven of the SNPs from non-coding regions are found in the transcriptional factor response elements and their possible role in gene regulation was evaluated with regard to MS. AMS and CMS were found to be significantly associated with the four genes compared to their Han and Tibetan control groups, respectively, indicating that these nucleotide alterations have a physiological effect for the development of high altitude sickness.

EPAS1 and EGLN1 associations with high altitude sickness in Han and Tibetan Chinese at the Qinghai-Tibetan Plateau

High altitude sickness (HAS) occurs among humans visiting or inhabiting high altitude environments. Genetic differences in the EPAS1 and EGLN1 genes have been found between lowland (Han) and highland (Tibetan) Chinese. Three SNPs within EPAS1 and EGLN1 were evaluated in Han and Tibetan patients with acute mountain sickness (AMS) and chronic mountain sickness (CMS). We compared 85 patients with AMS to 79 Han unaffected with mountain sickness (MS) as well as 45 CMS patients to 34 unaffected Tibetan subjects. The three SNPs studied were EPAS1 [ch2: 46441523 (hg18], EGLN1 (rs480902) and (rs516651). Direct sequencing was used to identify individual genotypes for the three SNPs. Age was found to be significantly associated with the EPAS1 SNP in the CMS patients while heart rate (HR) and oxygen saturation level of hemoglobin (SaO(2)) were found to be significantly associated with the EGLN1 (rs480902) SNP in the Han patients with AMS. The individuals with CMS were found to diverge significantly for the EPAS1 SNP compared to their Tibetan control group as measured by genetic distance (0.123) indicating positive selection of the EPAS-G allele with age and illness. The EGLN1 (rs480902) SNP had a significant correlation with hematocrit (HCT), HR and SaO(2) in AMS patients. AMS and CMS were found to be significantly associated with the EPAS1 and EGLN1 SNPs compared to their Han and Tibetan control groups, respectively, indicating these nucleotide alterations have a physiological effect for the development of high altitude sickness.

Genetic associations with mountain sickness in Han and Tibetan residents at the Qinghai-Tibetan Plateau

BACKGROUND

Acute (AMS) and chronic (CMS) mountain sicknesses are illnesses that occur among humans visiting or inhabiting high-altitude environments, respectively. Some individuals are genetically less fit than others when stressed by an extreme high-altitude environment. Seven blood physiological parameters and five genetic polymorphisms were studied in Han patients with AMS and Tibetan patients with CMS.

METHODS

We compared 98 AMS patients with 60 Han controls as well as 50 CMS patients with 36 Tibetan controls. The genetic loci studied are ACE I/D (rs4340), AGT M235T (rs699), AGTR1 A1166C (rs5186), GNB3 A(-350)G (rs2071057) and APOB A/G (rs693).

RESULTS

All physiological parameters (RBC, HCT, Hb, SaO(2), HR, and BPs/d) studied significantly changed in the CMS patients while SaO(2) and HR changed in the AMS Han patients compared to their controls. The ACE D and AGT 235M alleles were found to be significantly associated with AMS and CMS, respectively, while a significantly high incidence of the G-protein (GNB3) (-350)A allele was found in the AMS patients. ACE (I/D) was significantly associated with HR in CMS patients while the AGT M235T was significantly associated with SaO(2) and BPs/d in AMS patients. APOB A/G was significantly associated with BPs/d in AMS and HR in CMS patients.

CONCLUSION

AMS and CMS share very similar genetic results for the ACE I/D and AGT M235T polymorphisms indicating that these mutations have an effect on both illnesses.