Patients with obstructive sleep apnea present with chronic upregulation of serum HIF-1α protein

Study Objectives: Obstructive sleep apnea (OSA) is a chronic condition that is characterized by recurrent pauses in breathing during sleep causing intermittent hypoxia. The main factor responsible for oxygen metabolism homeostasis is hypoxia-inducible factor 1 (HIF-1), comprised of 2 subunits: alpha (oxygen sensitive) and beta. The aim of the study was to investigate the HIF-1 alpha serum protein level and mRNA HIF-1 alpha expression in patients with OSA and a healthy control group and determine their evening-morning variation and association with polysomnography parameters. Methods: Eighty-four individuals were enrolled in the study. All patients underwent polysomnography examination and based on the results were divided into 2 groups: OSA group (n = 60) and control group (n = 24). Peripheral blood was collected in the evening before and in the morning after the polysomnography. HIF-1 alpha expression was evaluated on protein in blood serum and mRNA level in peripheral blood leukocytes. Results: HIF-1 alpha serum protein concentration was higher in patients with OSA compared with control patients in both the evening (1,490.1 vs. 727.0 pg/mL; P <.001) and the morning (1,368.9 vs. 702.1 pg/mL; P <.001) samples. There was no difference between evening and morning HIF-1 alpha serum protein level in either group. No differences were observed in HIF-1 alpha mRNA expression between the OSA and control group. Additionally, evening and morning HIF-1 alpha serum protein level correlated with number of desaturations during sleep (r = .384, P < .001 and r = .433, P < .001, respectively). Conclusions: Observed differences in HIF-1 alpha serum protein level between the OSA and the control groups without difference between evening and morning measurements suggest chronic increase in this protein concentration by intermittent nocturnal hypoxia in OSA.