Pro: All dwellers at high altitude are persons of impaired physical and mental powers

Higher Circulating miR-199a-5p Indicates Poor Aerobic Exercise Capacity and Associates With Cardiovascular Dysfunction During Chronic Exposure to High Altitude

Background

Hypoxia-induced decline in exercise capacity is ubiquitous among lowlanders who immigrated to high altitudes, which severely reduces their work efficiency and quality of life. Although studies have revealed that hypoxia-induced cardiovascular dysfunction limits exercise capacity at high altitudes, the mechanisms have not been well explored at the molecular level. miR-199a-5p is hypoxia-sensitive and serves as an important regulator in cardiovascular pathophysiology. However, whether miR-199a-5p is involved in cardiovascular dysfunction at high altitudes and contributes to subsequent reductions in exercise capacity remains unknown. Thus, this study aimed at exploring these relationships in a high altitude population.

Methods

A total of 175 lowlanders who had immigrated to an altitude of 3,800 m 2 years previously participated in the present study. The level of plasma miR-199a-5p and the concentration of serum myocardial enzymes were detected by qRT-PCR and ELISA, respectively. Indices of cardiovascular function were examined by echocardiography. The exercise capacity was evaluated by Cooper’s 12-min run test and the Harvard Step Test. Furthermore, we explored the biological functions of miR-199a-5p with silico analysis and a biochemical test.

Results

The level of miR-199a-5p was significantly higher in individuals with poor exercise capacity at 3,800 m, compared with those with good exercise capacity (p < 0.001). miR-199a-5p accurately identified individuals with poor exercise capacity (AUC = 0.752, p < 0.001). The level of miR-199a-5p was positively correlated with cardiovascular dysfunction indices (all, p < 0.001). Furthermore, miR-199a-5p was involved in the oxidative stress process.

Conclusion

In this study, we reported for the first time that the level of circulating miR-199a-5p was positively associated with exercise capacity during chronic hypoxia at high altitudes. Moreover, higher miR-199a-5p was involved in hypoxia-induced cardiovascular dysfunctions, thus contributing to poorer exercise endurance at high altitudes.

Human Genetic Adaptation to High Altitudes: Current Status and Future Prospects

The question of whether human populations have adapted genetically to high altitude has been of interest since studies began there in the early 1900s. Initially there was debate as to whether genetic adaptation to high altitude has taken place based, in part, on disciplinary orientation and the sources of evidence being considered. Studies centered on short-term responses, termed acclimatization, and the developmental changes occurring across lifetimes. A paradigm shift occurred with the advent of single nucleotide polymorphism (SNP) technologies and statistical methods for detecting evidence of natural selection, resulting in an exponential rise in the number of publications reporting genetic adaptation. Reviewed here are the various kinds of evidence by which adaptation to high altitude has been assessed and which have led to widespread acceptance of the idea that genetic adaptation to high altitude has occurred. While methodological and other challenges remain for determining the specific gene or genes involved and the physiological mechanisms by which they are exerting their effects, considerable progress has been realized as shown by recent studies in Tibetans, Andeans and Ethiopians. Further advances are anticipated with the advent of new statistical methods, whole-genome sequencing and other molecular techniques for finer-scale genetic mapping, and greater intradisciplinary and interdisciplinary collaboration to identify the functional consequences of the genes or gene regions implicated and the time scales involved.