BackgroundHypoxia-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.MethodsA 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.ResultsThe 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.ConclusionIn 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.

BackgroundChronic mountain sickness (CMS), is a common disease occurred to people who migrate to plateau. Current CMS studies in different periods or areas have poor comparability due to the inconsistent diagnosis methods. Here we carried out a comparative study of the CMS prevalence in the year 2019 and 2009, to provide evidence for the prevention and diagnosis of CMS. Methods The Qinghai CMS Scoring System (Qinghai standard) was used to investigate the subjects who lived for at least months in the 3300-5400 m altitude area in 2019 and 2009, respectively. Their prevalence and symptom scores were also analyzed and statistically compared.ResultsThe prevalence of CMS in 2019 survey subjects (15.60%) was significantly lower than that in 2009 (31.18%). The prevalence of dyspnea, venous dilatation, paresthesia, headache, tinnitus, and hemoglobin concentration reached 21g/dL or above decreased significantly among the survey subjects in 2019. The scores of cyanosis, venous dilatation, paresthesia, and headache significantly decreased in the 2019 survey subjects. But among the CMS patients, the sleep disturbance scores of the 2019 survey subjects increased significantly. ConclusionCompared to 2009, the health level of high altitude living population in 2019 has been significantly improved, indicating that the sleep research on high-altitude living population and the application of high altitude oxygen therapy has been effective in the past ten years. Among the CMS associated symptoms, sleep disturbance is an important indicator for the prevention and diagnosis of CMS, which deserves special attention.