Vascular reactivity and biomarkers of endothelial function in healthy subjects exposed to acute hypobaric hypoxia

Aims The aim of this study was to evaluate the effects of acute hypobaric hypoxia (HH) on vascular reactivity and biochemical markers associated with endothelial function (EF). Main methods Ten healthy subjects were exposed to a simulated altitude of 4,000 meters above sea level for 4 hours in a hypobaric chamber. Vascular reactivity was measured by the flow-mediated vasodilatation (FMVD) test. Endothelin-1, high sensitive-C reactive protein (hsCRP), vascular cell adhesion molecule 1, interleukin-6 (IL-6), tumor necrosis factor-α (TNF-α), paraoxonase and adiponectin levels, and FMVD were evaluated before and after the exposure. Key findings Subjects were young (age: 32 ± 6 years), lean [body mass index: 23.9 ± 2.0 kg/m2, waist circumference: 77(IQR: 72–80) cm], and presented normal clinical and biochemical parameters. No significant changes were evidenced in FMVD in response to HH (pre: 0.45 (0.20–0.70) vs. during: 0.50 (0.20–1.22) mm; p = 0.594). On the other hand, endothelin-1 (+ 54%, p < 0.05), hsCRP (+ 37%, p < 0.001), IL-6 (+ 75%, p < 0.05), TNF-α (+ 75%, p < 0.05), and adiponectin (− 39%, p < 0.01) levels were significantly altered post-HH. FMVD was increased in 7 subjects, and it was decreased in 3 individuals during HH exposure. Interestingly, when EF biomarkers were compared between these two subgroups of subjects, only post exposure-adiponectin levels were significantly different (49 ± 5 vs. 38 ± 6 μg/ml, respectively, p < 0.05). Significance HH exposure had an effect on endothelin-1, adiponectin, hsCRP, IL-6, and TNF-α concentration. However, adiponectin was the only biomarker associated with an altered vascular reactivity.