Elevated levels of interleukin-35 and interleukin-37 in adult patients with obstructive sleep apnea

Background Systemic inflammation has a critical role in the pathogenesis of obstructive sleep apnea (OSA). Interleukin (IL)-35 and IL-37 have been identified as novel immune-modulating cytokines with anti-inflammatory activities in numerous types of inflammatory disease. The present study aimed to examine the serum levels of IL-35 and IL-37 in patients with OSA, and to investigate their associations with the severity of OSA. Methods A total of 97 patients, including 67 cases of OSA and 30 age- and gender-matched healthy control subjects, were enrolled in the present study. All subjects were evaluated by overnight polysomnography. Serum IL-35, IL-37, and pro-inflammatory cytokine IL-1 beta levels were examined by ELISA. Results Compared with those in the control subjects, serum IL-35, IL-37, and IL-1 beta levels were significantly elevated in patients with mild, moderate, or severe OSA. Furthermore, a severity-dependent increase in serum IL-35 and IL-37 levels was observed in patients with OSA. IL-35 and IL-37 levels were positively correlated with the apnea-hypopnea index (r = 0.742 and 0.578, respectively; both p < 0.001), while they were negatively correlated with the mean oxygen saturation (r = -0.461 and -0.339, respectively; both p < 0.001) and lowest oxyhaemoglobin saturation (r = -0.616 and -0.463, respectively; both p < 0.001) in patients with OSA. In addition, a positive correlation was observed between IL-35 or IL-37 and IL-1 beta levels (all p < 0.001). Conclusion The serum levels of IL-35 and IL-37 were significantly increased in patients with OSA and associated with the severity of OSA, implying that IL-35 and IL-37 may have a protective role in OSA by counteracting inflammatory responses.