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Original Research: SLEEP DISORDERS |

Cysteine: A Potential Biomarker for Obstructive Sleep Apnea

Fatima Cintra, MD; Sergio Tufik, MD, PhD; Vânia D’Almeida, PhD; Bruno F. A. Calegare, MS; Angelo de Paola, MD, PhD; Wercules Oliveira, MD; Camila Rizzi, PT; Suely Roizenblatt, MD, PhD; Dalva Poyares, MD, PhD
Author and Funding Information

From the Department of Psychobiology (Drs Cintra, Tufik, D’Almeida, Oliveira, Roizenblatt, and Poyares and Mr Calegare), the Department of Biosciences (Dr D’Almeida), and the Department of Medicine (Drs de Paola and Oliveira and Ms Rizzi), Universidade Federal de São Paulo, Brazil.

Correspondence to: Fatima Cintra, MD, Rua Napoleão de Barros, 925 Vila Clementino, São Paulo, SP, Brazil 04024-002; e-mail: fatimacintra@interair.com.br


For editorial comment see page 237.

Funding/Support: This work was supported by FAPESP-Fundação de Amparo a Pesquisa do Estado de São Paulo, São Paulo, Brazil, [Grants 98/14303-3] and AFIP-Associação Fundo de Incentivo a Psicofarmacologia, São Paulo, Brazil. Drs Poyares and Tufik are recipient of grants from The National Council for Scientific and Technological Development.

Reproduction of this article is prohibited without written permission from the American College of Chest Physicians (http://www.chestpubs.org/site/misc/reprints.xhtml).


© 2011 American College of Chest Physicians


Chest. 2011;139(2):246-252. doi:10.1378/chest.10-0667
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Objective:  Obstructive sleep apnea (OSA) is a risk factor for a number of cardiovascular conditions. Although homocysteine (Hcy) and cysteine (Cys) are regarded as cardiovascular risk factors, few studies have analyzed Hcy and Cys plasma concentrations in patients with OSA. The aim of this study was to evaluate the role of Hcy 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/m2) 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 μmol/L vs 439.81 ± 76.12 μmol/L, respectively, P < .01); however, the Hcy 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 μmol/L vs 412.01 ± 70.73 μmol/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.

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