Serum and mucosal brain derived neurotrophic factor (BDNF) in severe obstructive sleep apnea syndrome (OSAS). Effects of CPAP treatment on BDNF serum levels

Abstract

Background: OSAS is characterized by a chronic intermittent hypoxia (CIH) and sleep fragmentation. PSG is the gold standard for diagnosis. New biomarkers have been proposed. BDNF is a key mediator of cognitive functions. Changes of BDNF serum levels follow CIH. OSAS patients have mucosal upper airways inflammation. BDNF has been identified in various chronic inflammatory airways diseases. Objectives: BDNF serum levels and mucosal expression in severe OSAS patients compared to controls. Relationship of serum BDNF with neurocognitive function. Changes in serum BDNF after CPAP. Methods: Serum BDNF, upper airways mucosal biopsy and Montreal Cognitive Assestment (MoCA) are performed in 12 naive severe OSAS patients and in 8 controls. In OSAS patients serum BDNF and MoCA were reassessed after 45 days of CPAP treatment. Results: BDNF in OSAS was significantly higher than controls (p=0.01) and showed a positive correlation with ODI (p=0.01, r=0.6). Serum BDNF had a decreasing trend after CPAP treatment. Before the treatment, MoCA scores were lower in OSAS than controls and are positively correlated with serum BDNF levels (p=0.02, r=0.57). MoCA is normalized by CPAP therapy. Immunohistochemistry of mucosal biopsy in OSAS patients showed higher inflammatory infiltrate CD3+ CD79a+ (BDNF positive) than controls. Conclusions: OSAS patients showed higher serum BDNF levels and lower MoCA scores than controls. The positive correlation between BDNF values and MoCA might reveal a peculiar BDNF-mediated neuroprotective mechanism against neuroinflammation induced by hypoxia. OSAS have mucosal upper airway lymphocytic inflammation BDNF positive.