Chest
Volume 139, Issue 2, February 2011, Pages 246-252
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Original Research
Sleep Disorders
Cysteine: A Potential Biomarker for Obstructive Sleep Apnea

https://doi.org/10.1378/chest.10-0667Get rights and content

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.

Section snippets

Study Population

Patients who were submitted to overnight full polysomnography study were selected from the Sleep Clinic of Universidade Federal de São Paulo database between March 2007 and March 2008. Subjects were included if they were > 30 years old, sedentary, and reported no recent hospitalization or change in medication. Exclusion criteria were as follows: BMI > 40 kg/m2; chronic pulmonary disease based on the spirometric classification, defined as an FEV1/FVC < 0.723; history of smoking; New York Heart

General Results

A total of 75 patients with OSA were studied, and the control group was composed of 75 subjects matched for age and sex. The baseline characteristics of the subjects are presented in Table 1. There were no differences in age, sex, baseline heart rate, or frequency of arterial hypertension between patients with OSA and control subjects. Patients with OSA were characterized by higher BMI (31.02 ± 6.67 kg/m2 vs 27.24 ± 4.17 kg/m2, P < .001), higher cervical (37.41 ± 5.15 cm vs 33.54 ± 3.95 cm, P <

Discussion

This study evaluated the role of Cys and Hcy in patients with OSA. We controlled for BMI and demonstrated a significant association between Cys plasma levels and OSA. There was an increased Cys plasma level in patients with OSA compared with control subjects. We also demonstrated that Cys concentrations were reduced after long-term, effective CPAP treatment.

Hcy is a well-studied marker of cardiovascular disease. Schnyder et al13 evaluated the relationship between Hcy plasma levels on admission

References (38)

Cited by (36)

  • A new isothiocyanate-based Golgi-targeting fluorescent probe for Cys and its bioimaging applications during the Golgi stress response

    2022, Bioorganic Chemistry
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    It was found that the cysteine (Cys) content of Golgi increased significantly during oxidative stress, reduced cell damage and protected cell morphology. Cys is a reactive sulfur species, which exists in most proteins and participates in various physiological processes and regulatory functions [6–8], the concentration in cells is 30–200 μM [9]. It is reported that abnormal content of Cys is strongly associated with Huntington's disease (HD), cardiovascular diseases and other diseases [10,11].

  • Advances and challenges in pursuing biomarkers for obstructive sleep apnea: Implications for the cardiovascular risk

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    It has been demonstrated that the effects of hypoxia, and sleep deprivation, alone and in combination in rats cause an increase in cysteine concentration [31]. In humans, previous studies have demonstrated high levels of the precursor homocysteine [32,33] and cysteine [30] in OSA patients independent of body mass index. Interestingly, one study found that cysteine plasma levels increased in parallel with the OSA severity and the levels of cysteine were higher in the OSA lean subgroup when compared with lean control subjects.

  • Isothiocyanate can be used as a highly specific recognition site for fluorescent cysteine probes

    2021, Sensors and Actuators, B: Chemical
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    As an essential sulfhydryl amino acid, cysteine (Cys) plays pivotal roles in lots of physiological and pathological events [1]. Besides the biological importance of Cys, the concentration of Cys has clinical implications as a biomarker for several diseases [2]. For example, lack of Cys can lead to slow growth, lethargy, edema, damage of liver, skin lesions, weakness, etc.

  • Bioanalysis of underivatized amino acids in non-invasive exhaled breath condensate samples using liquid chromatography coupled with tandem mass spectrometry

    2018, Journal of Chromatography A
    Citation Excerpt :

    Similarly, amino acid profiles are different in urine samples from patients with bladder cancer [11] and in CSF samples from patients suffering from preeclampsia [12]. Insofar as amino acids are considered to be biomarkers of obstructive sleep apnea (OSA), plasma samples from people suffering from OSA showed higher concentrations of homocysteine and cysteine [13,14], which are both seen as good biomarkers of cardiovascular risk among those with this condition [15]. Other articles connecting amino acids with OSA suggest that tryptophan metabolism plays a significant role in cardiovascular risk among OSA populations [16].

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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.

© 2011 American College of Chest Physicians Reproduction of this article is prohibited without written permission from the American College of Chest Physicians (http://www.chestpubs.org/site/misc/reprints.xhtml).

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