Frequency of Polycythemia and Other Abnormalities in a Tibetan Herdsmen Population Residing in the Kham Area of Sichuan Province, China

Sex differences in genotype frequency and the risk of polycythemia associated with rs13419896 and rs2790859 among Tibetan highlanders living in Tsarang, Mustang, Nepal

BACKGROUND

Tibetan highlanders have adapted to hypoxic environments through genetic mechanisms that avoid hemoglobin concentration increases and prevent polycythemia. Recently, sex differences in hemoglobin dynamics with age have been reported among Tibetan highlanders living in Tsarang. Additionally, concerns have been raised that dietary changes associated with modernization may increase the risk of polycythemia and lifestyle-related diseases among Tibetan highlanders. However, the relationship between genetic polymorphisms and the risk of lifestyle-related diseases in Tibetan highlanders has been investigated in only a few regions. This study aims to elucidate whether polymorphisms in genes related to hypoxic adaptation are associated with the incidence of lifestyle-related diseases and polycythemia and whether these polymorphisms affect hemoglobin dynamics in the residents of Tsarang, Mustang, Nepal.

METHODS

Health checkup data from individuals living in Tsarang in Mustang District, Nepal, collected in 2017, were used to determine the prevalence of obesity, hypertension, diabetes, hypoxemia, and polycythemia. DNA was extracted from whole-blood samples, and data for the single-nucleotide polymorphisms (SNPs) rs13419896 (EPAS1), rs12619696 (EPAS1), and rs2790859 (EGLN1) were obtained using real-time PCR. The health checkup data were statistically analyzed to determine the associations of these diseases with polymorphisms in genes related to hypoxic adaptation.

RESULTS

A total of 168 participants, comprising 78 males and 90 females, were included in the final analysis. In terms of the prevalence of each disease, only the prevalence of polycythemia significantly differed between sexes (p < 0.01). Additionally, among the three analyzed SNPs, significant sex differences in genotype frequency were observed for rs13419896 and rs2790859. For rs2790859 in females, Tibetan highlanders with the adaptive genotype had a significantly lower incidence of polycythemia (p < 0.01) and significantly lower hemoglobin concentrations (p < 0.01).

CONCLUSIONS

This study revealed that there are sex differences in the genotype frequency of gene-related hypoxic adaptations among the residents of Tsarang. The findings also suggested that the rs2790859 polymorphism might be involved in the recent incidence of polycythemia among Tsarang residents. If the frequency of non-Tibetan genotypes increases due to intermixing with other populations in the Mustang District, polycythemia may emerge as a modern disease. It is essential to continue investigating the health status of Mustang residents to elucidate various aspects of hypoxic adaptation and disease susceptibility.

Prevalence and Risk Factors of Hyperuricemia Among Young and Middle-Aged Tibetan Men Living at Ultrahigh Altitudes: A Cross-Sectional Study

He, Ben, Jiayue Feng, Yan Shu, Lichun Yang, Zepin He, Kanxiu Liao, Hui Zhuo, and Hui Li. Prevalence and risk factors of hyperuricemia among young and middle-aged Tibetan men living at ultrahigh altitudes: a cross-sectional study. High Alt Med Biol. 25:42-48, 2024. Background: Few studies have examined the prevalence or risk factors of hyperuricemia among populations living at ultrahigh altitudes. Here we examined the prevalence of hyperuricemia and factors associated with it among young and middle-aged Tibetan men living at ultrahigh altitudes. Methods: This cross-sectional study analyzed 672 Tibetan men 18-60 years old living on the Qinghai-Tibet Plateau (mean altitude 4,014 m) within the county of Litang in the Ganzi Tibetan autonomous prefecture of Sichuan Province, China. Demographic and clinical data were collected from self-administered questionnaires, physical examinations and laboratory tests. Participants whose blood uric acid (UA) contained >420 μmol/l were classified as having hyperuricemia. Results: Of the 672 men analyzed, 332 (49.4%) had hyperuricemia. Multivariate logistic regression showed risk of hyperuricemia to correlate positively with body mass index (per 1 U increase: odds ratio [OR] 1.172, 95% confidence interval [CI] 1.1066-1.243), triglycerides (OR 1.408, 95% CI 1.084-1.828), red blood cell count (OR 1.376, 95% CI 1.009-1.875), and creatinine level (per 1 U increase: OR 1.051, 95% CI 1.033-1.070). Conversely, risk of hyperuricemia correlated negatively with the presence of diabetes mellitus (OR 0.412, 95% CI 0.175-0.968). Subgroup analyses showed that prevalence of hyperuricemia was significantly higher among those with polycythemia than among those without it, and that UA levels correlated positively with hematocrit and hemoglobin levels. Conclusions: Hyperuricemia is an important public health problem among Tibetan men living at ultrahigh altitudes in Ganzi autonomous prefecture. The region urgently requires appropriate prevention and management efforts.

Prevalence of High-Altitude Polycythemia and Hyperuricemia and Risk Factors for Hyperuricemia in High-Altitude Immigrants

Song Zhen, Anxin Zhang, Jie Luo, Guanghai Xiong, Haibo Peng, Rang Zhou, Yuanfeng Li, Hongqiang Xu, Zhen Li, Wei Zhao, and Haoxiang Zhang. Prevalence of high-altitude polycythemia and hyperuricemia and risk factors for hyperuricemia in high-altitude immigrants. High Alt Med Biol. 24:132-138, 2023. Background: Few studies have investigated the epidemiology of chronic mountain sickness (CMS) in high-altitude immigrants. This study evaluated the prevalence of polycythemia and hyperuricemia (HUA) and risk factors for HUA in high-altitude immigrants. Methods: A cross-sectional study was conducted with 7,070 immigrants 15-45 years of age living on the Tibetan Plateau between January and December 2021. Information from routine physical examinations was obtained from each participant. Binary logistic regression analysis was performed to determine the correlation of several risk factors for HUA. Results: The prevalence of high-altitude polycythemia (HAPC) and HUA was 25.8% (28.7% in males and 9.4% in females) and 54.2% (59.9% in males and 22.5% in females), respectively. The highest prevalence of HAPC in males and females was observed in participants 26-30 and 21-25 years of age, respectively. The highest prevalence of HUA in both males and females was observed in participants 26-30 years of age. Binary logistic regression analysis showed that age, sex, and hemoglobin (Hb) concentration were risk factors for HUA, among which age was a negative factor and male sex and Hb concentration were positive factors. Conclusions: Immigrants are more susceptible to HAPC and HUA. The high prevalence of CMS of immigrants may be associated with Hb concentration, age, and sex.

Two a posteriori dietary patterns are associated with risks of hyperuricemia among adults in less-developed multiethnic regions in Southwest China

Diet is a major determinant of hyperuricemia, but little is known about the association between diet and hyperuricemia in less-developed multiethnic regions (LMERs). This study aimed to assess the hypothesis that dietary patterns (including 2 a-priori and 3 a posteriori dietary patterns) are associated with hyperuricemia in LMERs. The 2 a priori dietary patterns were the Dietary Approaches to Stop Hypertension (DASH) and the alternative Mediterranean diet (aMED). We derived 3 a posteriori dietary patterns from the China Multi-Ethnic Cohort study by principal component factor analysis. Given that those dietary patterns had high geographic discrimination, they were named the Sichuan Basin (economically developed industrial region), Yunnan-Guizhou Plateau (agricultural region), and Qinghai-Tibet Plateau (nomadic region) dietary pattern, respectively. We performed a logistic regression model to investigate associations between dietary patterns and hyperuricemia with potential confounders identified by the directed acyclic graph. Comparing the highest with the lowest quintiles, the Sichuan Basin dietary pattern was positively associated with hyperuricemia, whereas the Yunnan-Guizhou Plateau dietary pattern showed an inverse association with hyperuricemia. For the Qinghai-Tibet Plateau dietary pattern, DASH, or aMED, our results did not show a significant association with hyperuricemia. The results were robust among stratified analyses and different analyzing strategies. The dietary patterns showed great diversity in Southwest China. Both DASH and aMED, which many studies widely recommended, did not show expected beneficial effects on preventing hyperuricemia. However, the plant-based protein dietary pattern in the Yunnan-Guizhou Plateau showed a beneficial association with the risk of hyperuricemia, which can provide insights for dietary guidance in LMERs.

Unique hemoglobin dynamics in female Tibetan highlanders

BACKGROUND

Tibetan highlanders have adapted to hypoxic environments through the development of unique mechanisms that suppress an increase in hemoglobin (Hb) concentration even in high-altitude areas. Hb concentrations generally decrease with increasing age. However, in the highlands, chronic altitude sickness is known to occur in the elderly population. To investigate how aging in a hypoxic environment affects Hb levels in Tibetan highlanders, we focused on the Mustang people, who live above 3500 m. We tried to clarify the pure relationship between aging and Hb levels in a hypoxic environment.

RESULTS

We found that the Hb concentration increased with increasing age in females but not in males. Multivariate analysis showed that age, pulse pressure, the poverty index, and vascular diameter were strongly correlated with the Hb concentration.

CONCLUSIONS

We found unique Hb dynamics among female Tibetan highlanders. As seen in these Hb dynamics, there may be sex-based differences in the adaptive mechanism in Tibetan highlanders.

The Genetic Architecture of Chronic Mountain Sickness in Peru

Chronic mountain sickness (CMS) is a pathological condition resulting from chronic exposure to high-altitude hypoxia. While its prevalence is high in native Andeans (>10%), little is known about the genetic architecture of this disease. Here, we performed the largest genome-wide association study (GWAS) of CMS (166 CMS patients and 146 controls living at 4,380 m in Peru) to detect genetic variants associated with CMS. We highlighted four new candidate loci, including the first CMS-associated variant reaching GWAS statistical significance (rs7304081; P = 4.58 × 10⁻⁹). By looking at differentially expressed genes between CMS patients and controls around these four loci, we suggested AEBP2, CAST, and MCTP2 as candidate CMS causal genes. None of the candidate loci were under strong natural selection, consistent with the observation that CMS affects fitness mainly after the reproductive years. Overall, our results reveal new insights on the genetic architecture of CMS and do not provide evidence that CMS-associated variants are linked to a strong ongoing adaptation to high altitude.

Echinococcosis transmission on the Tibetan Plateau

Since the mid-1990s detailed studies and field investigations on the Tibetan Plateau have revealed human echinococcosis to be an under-reported major public health problem, particularly in the dominant pastoral communities in the eastern and central regions. Human prevalence surveys showed that cystic echinococcosis (CE, caused by Echinococcus granulosus) and alveolar echinococcosis (AE, caused by Echinococcus multilocularis) are co-endemic with higher burdens of each disease than other endemic world regions. Epidemiological investigations identified some major risk factors for human CE and AE including dog ownership, husbandry practices and landscape features. Dogs appear to be the major zoonotic reservoir for both E. granulosus and E. multilocularis, but the latter is also transmitted in complex wildlife cycles. Small mammal assemblages especially of vole and pika species thrive on the Plateau and contribute to patterns of E. multilocularis transmission which are influenced by landscape characteristics and anthropogenic factors. Tibetan foxes are a principal definitive host for both E. multilocularis and E. shiquicus. In 2006 a national echinococcosis control programme was initiated in Tibetan communities in northwest Sichuan Province and rolled out to all of western China by 2010, and included improved surveillance (and treatment access) of human disease and regular deworming of dogs with annual copro-testing. Control of echinococcosis in Tibetan pastoral communities poses a difficult challenge for delivery and sustainability.