[Association between serum levels of osteopontin and systolic pulmonary artery pressure among healthy adults post acute high altitude exposure]

Objective: To explore the association between serum levels of osteopontin (OPN) and systolic pulmonary artery pressure (sPAP) in healthy men following acute high altitude exposure. Methods: According to the inclusion and exclusion criteria, this observational study included 94 male subjects (aged from 18 to 30 years, dwelling in lowland<500 m) who ascended to Litang (4 100 m) from Chongqing (400 m) by bus with a stair-like journey within 7 days in June 2013. Data including basic information, OPN, superoxide dismutase (SOD), and malondialdehyde (MDA) and echocardiographic derived sPAP were collected within 48 hours before ascent and within 2-7 hours after arrival. Accordingly, subjects were divided into 3 groups based on the tertiles of sPAP after acute high altitude exposure: low sPAP group (26.8-32.3 mmHg (1 mmHg=0.133 kPa)) (n=31), middle sPAP group (32.4-37.4 mmHg) (n=32) and high sPAP group (37.5-55.6 mmHg) (n=31). Associations of serum OPN and SOD levels with sPAP were analysed by univariate and multivariate linear regression analysis. Results: After acute high altitude exposure, the levels of sPAP were significantly increased (P<0.001). There were no differences in age, height, weight, body mass index, percent of Han nationality and smoking among 3 subgroups. However, following acute high altitude exposure, the levels of heart rate, systolic and diastolic blood pressure elevated (all P<0.05), whereas the levels of oxygen saturation were reduced in the total subjects and all subgroups (all P<0.05). Moreover, systolic blood pressure of subjects in the high sPAP group was higher than that in low and middle sPAP groups (both P<0.05), and diastolic blood pressure of subjects in high sPAP group was higher than that in low sPAP group (P<0.05). The serum levels of OPN were increased in total cohort(27.9 (22.5,34.0) μg/L vs. 25.6 (18.4, 33.1) μg/L, P<0.05)， and high sPAP group (P<0.05), whereas no differences were found in serum SOD and MDA levels among groups. Furthermore, the serum level of OPN in high sPAP group was higher than that in low sPAP group at high altitude (P<0.05), and there was a trend for decline in SOD level with increasing sPAP (P>0.05). Results from univariable linear regression analysis showed that the serum levels of OPN (r=0.32, P=0.002) and SOD (r=-0.22，P=0.032) were linearly correlated with sPAP in total cohort after high altitude exposure. Multivariate regression analysis showed that the serum levels of OPN(β=0.310，P=0.002) and SOD (β=-0.199，P=0.043) were independently associated with the levels of sPAP at high altitude. Conclusion: After acute high altitude exposure, the serum level of OPN is positively associated with sPAP, suggesting that OPN may be a novel bio-marker for predicting the increase of pulmonary pressure in response to acute high altitude exposure.