Serum lipocalin-2 and myeloperoxidase, serum 8-hydroxy-2'-deoxyguanosine (8-OHdG), serum endocan, and YKL-40 (chitinase3-like protein 1): Novel inflammatory markers of endothelial dysfunction in children with sleep-disordered breathing

Background: Paediatric sleep-disordered breathing (SDB) ranges from primary snoring to obstructive sleep apnea (OSA) and is associated with endothelial dysfunction and cardiovascular risk. Novel biomarkers reflecting inflammation, oxidative stress, and endothelial activation may improve early detection. To assess the level of LCN2, MPO, 8-OHdG, endocan, and YKL-40 in serum samples from children suffering from SDB in comparison to healthy control subjects, and their relationship with SDB severity. Methods: The study design included a cross-sectional trial comprising 120 children aged 3–12 years: 60 patients with sleep-disordered breathing diagnosed by polysomnography (20 mild, 20 moderate, and 20 severe) and 60 control participants of similar age and sex. Serum levels of LCN2, MPO, 8-OHdG, endocan, and YKL-40 were measured by ELISA. Endothelial dysfunction was evaluated using flow-mediated dilation (FMD). Results: All five biomarkers were significantly elevated in children with SDB compared to controls (p<0.001 for all). Biomarker levels increased with SDB severity. Significant negative correlations were observed between FMD and LCN2 (r=-0.72), MPO (r=-0.68), 8-OHdG (r=-0.65), endocan (r=-0.70), and YKL-40 (r=-0.66) (all p<0.001). The combined biomarker panel showed excellent diagnostic accuracy for SDB (AUC=0.94). Conclusion: LCN2, MPO, 8-OHdG, endocan, and YKL- 40 are new markers of serum that are indicative of the presence of endothelial dysfunction in SDB in children and can be used as markers of the severity of the disorder. The proposed biomarker panel demonstrated good diagnostic performance in this tertiary care centre population; however, it remains to be validated in other settings.