Beclin-1 circulating levels in middle-aged men with sleep-disordered breathing

Background: Obstructive sleep apnea syndrome (OSA) is responsible for intermittent hypoxia (IH), which participates to OSA-associated systemic dysfunction. Recent studies have suggested a potential role of autophagy in the systemic processes driven by IH in OSA patients. Aims and Objectives: To determine whether OSA causing IH are associated with change in circulating Beclin-1 level, a potential biomarker of autophagy (Schlemmer, F et al., Cell Death Dis. 2018 Feb 5;9(2):156), and if those changes are correlated to the comorbidities associated with this syndrome. Methods: Cross-sectional study in 212 prospectivelly enrolled, middle-aged men free of known cardiovascular events related or unrelated to sleep apnea. Each participant underwent full standard overnight polysomnography. Quantitative evaluation of Beclin-1 protein level by ELISA were performed in the sera of each subject (no OSA n=45, moderate OSA n=104, severe OSA n=61). Results: In univariate analysis, Beclin-1 protein level was correlated to apnea-hyponea index (AHI) (R=0.19; p=0.006), Epworth somnolence scale (R=0.019; p=0.019), oxygen desaturation index (R=0.015; p=0.036), FVC (R=-0.016; p=0.039), glycemia (R=0.19; p=0.007) and creatininemia (R=0.17; p=0.015), but not with age, BMI, abdominal perimeter, arterial stiffness, blood pressure or telomere length. A statistically significant positive trend was found in serum Beclin-1 protein level of non-OSA, moderate-OSA and severe-OSA patients (1.12±0.53, 1.41±0.59 and 1.62±0.69 ng/ml, respectively; p=0.003). Conclusions: Serum Beclin-1 levels are increased in OSA patients and are correlated with OSA severity. IH in OSA patients may induce an adaptative process of autophagy implicating Beclin1.