Serum matrix metalloproteinase-2 as a predictor of level of hypoxemia and severity of obstructive sleep apnea

Purpose Intermittent hypoxia in obstructive sleep apnea (OSA) resembles ischemia/reperfusion. Oxidative stress during ischemia/reperfusion increases matrix metalloproteinase-2 (MMP-2) activity and leads to adverse cardiovascular consequences in animal models, but there is scarce information about MMP-2 in humans with OSA. The aim of this study was to determine if serum MMP-2 levels of patients with OSA differ from controls and if MMP-2 activity correlates with the severity of OSA and level of hypoxemia. Methods Patients with OSA (n= 124) were recruited from the Sleep Disorders Center (Saskatoon City Hospital, Canada) after in-lab polysomnography (PSG). Controls (n= 26) were subjects referred for PSG who did not have OSA. Severity of OSA was categorized according to American Academy of Sleep Medicine criteria. Level of hypoxemia was expressed as oxygen desaturation index (ODI; 3% desaturation). Gelatin zymography was performed to measure serum MMP-2 activity. Results Serum MMP-2 activity was significantly higher in patients with OSA than in controls (p= 0.029). MMP-2 activity in patients with severe OSA was significantly higher than in those with mild/moderate OSA and controls (p= 0.002). Linear regression showed positive associations with MMP-2 activity in serum for AHI (p< 0.001) and ODI (p= 0.003). The associations persisted after adjustment for multiple confounders, including age, sex, BMI, and cardiovascular disease. Conclusions Serum MMP-2 activity was associated with OSA severity, and level of hypoxemia in patients with OSA, suggesting MMP-2 is worth considering as a potential biomarker to be included in future studies on sets of biomarkers for hypoxemic insult in OSA.