Cysteine A Potential Biomarker for Obstructive Sleep Apnea

Objective: Obstructive sleep apnea (OSA) is a risk factor for a number of cardiovascular conditions. Although homocysteine (Hey) and cysteine (Cys) are regarded as cardiovascular risk factors, few studies have analyzed Hey and Cys plasma concentrations in patients with OSA. The aim of this study was to evaluate the role of Hey and Cys in OSA in comparison with subjects without OSA and to determine the possible influence of obesity on these variables. Methods: Patients who submitted to polysomnography studies were recruited to engage in an 8-h fasting period for blood sample withdrawal, physical examination, ECG, and echocardiogram. A subgroup of lean patients with OSA (BMI <25 kg/m(2)) were analyzed to rule out the influence of obesity. Fifteen patients were randomly assigned to participate in a continuous positive airway pressure (CPAP) protocol to assess the influence of OSA treatment on the obtained measurements. Results: A total of 75 patients and 75 control subjects matched for age and sex were analyzed. The Cys plasma levels were higher in patients with OSA compared with control subjects (490.16 +/- 67.00 mu mol/L vs 439.81 +/- 76.12 mu mol/L, respectively, P < .01); however, the Hey plasma levels did not differ between groups. Cys plasma levels were also higher in the OSA lean subgroup when compared with lean control subjects (484.21 +/- 71.99 mu mol/L vs 412.01 +/- 70.73 mu mol/L, respectively, P = .009). There was a significant decrease of Cys plasma levels after 6 months of CPAP effective therapy. Conclusion: Cys is a potential biomarker of OSA in obese and nonobese patients and is reduced after effective OSA treatment. CHEST 2011; 139(2):246-252