Increased plasma YKL-40/chitinase-3-like-protein-1 is associated with endothelial dysfunction in obstructive sleep apnea

Obstructive sleep apnea (OSA) is a common disorder affecting 15-24% of the adults and is associated with increased risk of hypertension and atherosclerosis. The exact mechanisms underlying hypertension in OSA are not entirely clear. YKL-40/Chitinase-3-like protein-1 is a circulating moiety with roles in injury, repair and angiogenesis that is dysregulated in atherosclerosis and a number of other diseases. We sought to determine the role of YKL-40 in endothelial dysfunction and hypertension in OSA. We studies 23 normotensive OSA (N-OSA) and 14 hypertensive OSA (H-OSA) without diabetes and apparent cardiovascular disease. Endothelial-dependent nitric oxide-mediated vasodilatory capacity was assessed by flow-mediated vasodilation (FMD). YKL-40, vascular endothelial growth factor (VEGF) and the soluble form of VEGF receptor-1 or sFlt-1 were measured in plasma using ELISA methodology. N-OSA subjects aged 49.1 ± 2.3 years and H-OSA aged 51.3 ± 1.9 years with BMI 36.1 ± 1.6 and 37.6 ± 1.9 kg/m(2), respectively. The apnea-hypopnea index (AHI) was 41 ± 5 events/hr in N-OSA and 46 ± 6 in H-OSA with comparable degree of oxygen desaturations during sleep. FMD was markedly impaired in H-OSA (8.3% ± 0.8) compared to N-OSA (13.2% ± 0.6, P