SERUM MIDKINE LEVELS IN PATIENTS WITH OBSTRUCTIVE SLEEP APNOEA

HAKAN TANRIVERDI¹, FIRAT UYGUR¹, MURAT CAN², FATMA ERBOY¹, BÜLENT ALTINSOY¹, TACETTIN ÖRNEK¹, FÜRUZAN KÖKTÜRK³, MÜGE MELTEM TOR¹, FIGEN ATALAY¹

¹Bülent Ecevit University Faculty of Medicine Department of Chest Diseases and Tuberculosis, Zonguldak - ²Bülent Ecevit University Faculty of Medicine Department of Biochemistry - ³Bülent Ecevit University Faculty of Medicine Department of Biostatiscal Sciences, Turkey

Introduction: Obstructive sleep apnoea (OSA) is a highly prevalent disease characterised by obstruction of the airway resulting in reduced oxygen saturation. Hypoxia and blood re-oxygenation episodes called “intermittent hypoxia” (IH) initiates the inflammatory response. Midkine (MK), is a heparin-binding protein and plays a key role in angiogenesis and inflammation. Expression of MK increases under hypoxic conditions. Thus, we hypothesised that serum MK levels would in increase in patients with OSA.

Materials and methods: Patients who underwent full polysomnography with suspicion of OSA were eligible for the study. Serum MK and C-reactive protein (CRP) levels were compared between OSA and control groups.

Results: Twenty-four control and 53 patients with OSA were enrolled in the study. Median serum MK level was significantly lower in the OSA group than that in the control group (85.93 vs. 131.86 pg/mL, respectively; p = 0.001). No significant correlation was detected between OSA severity and serum MK level. Median serum CRP level tended to be higher in the OSA than that in the control group (2.8 vs. 2.05 mg/L, respectively; p = 0.075), but the difference was significant only in patients with severe OSA compared with those in the control group (4.3 vs. 2.05 mg/L, respectively; p < 0.01).

Conclusion: Unexpectedly lower serum MK levels were found in patients with OSA than those in the control group, but the mechanism underlying this condition is unclear. Rapid endocytosis, internalisation of serum MK or a different inflammatory response to IH may be responsible for these results.