title: Increased serum levels of cysteine in patients with schizophrenia: A potential marker of cognitive function preservation.
abstract: Oxidative stress has been implicated in the psychopathology of schizophrenia. Cysteine, a semi-essential amino acid, is the precursor of the antioxidant glutathione. The aim of this study was to investigate the differences in serum levels of cysteine between patients with schizophrenia and healthy controls. The relationships between levels of cysteine, psychopathology and cognitive function were also explored.
  
  
  
  We recruited 65 patients with schizophrenia and 65 age- and gender-matched healthy controls. Blood samples were collected to determine the serum levels of cysteine and plasma levels of metabolic parameters. The cognitive function of participants was assessed using the Brief Assessment of Cognition in Schizophrenia (BACS). The psychopathology of schizophrenic patients was evaluated using the Positive and Negative Syndrome Scale.
  
  
  
  Serum cysteine levels were significantly higher in schizophrenic patients than in controls (P<0.001). In patients with schizophrenia, serum levels of cysteine were positively correlated with cognitive function in terms of verbal memory (P=0.013), working memory (P=0.004), verbal fluency (P=0.027), attention and processing speed (P=0.025), executive function (P=0.024) and the composite score on the BACS (P=0.013). In healthy controls, no significant correlation was observed between cysteine level and cognitive function.
  
  
  
  These findings suggest that oxidative stress may be involved in the pathogenesis of schizophrenia, and compensatory elevated levels of cysteine may serve as an indicator of cognition preservation. Further prospective studies are warranted to investigate the dynamic alterations in cysteine and the underlying pathophysiology of schizophrenia.
authors.affiliation: Department of Child and Adolescent Psychiatry, Kaohsiung Chang Gung Memorial Hospital and Chang Gung University College of Medicine, Kaohsiung, Taiwan.
authors.forename: Liang-Jen
authors.initials: LJ
authors.lastname: Wang
authors.affiliation: Department of Psychiatry, Kaohsiung Chang Gung Memorial Hospital and Chang Gung University College of Medicine, Kaohsiung, Taiwan; Institute for Translational Research in Biomedical Sciences, Kaohsiung Chang Gung Memorial Hospital, Kaohsiung, Taiwan.
authors.forename: Pao-Yen
authors.initials: PY
authors.lastname: Lin
authors.affiliation: Department of Psychiatry, Kaohsiung Chang Gung Memorial Hospital and Chang Gung University College of Medicine, Kaohsiung, Taiwan.
authors.forename: Yu
authors.initials: Y
authors.lastname: Lee
authors.affiliation: Department of Psychiatry, Kaohsiung Chang Gung Memorial Hospital and Chang Gung University College of Medicine, Kaohsiung, Taiwan.
authors.forename: Yu-Chi
authors.initials: YC
authors.lastname: Huang
authors.affiliation: Department of Otolaryngology-Head & Neck Surgery, Linkuo Chang Gung Memorial Hospital, Taoyuan, Taiwan; Department of Medical Biotechnology and Laboratory Science, Chang Gung University, Tao-Yuan, Taiwan.
authors.forename: Chih-Ching
authors.initials: CC
authors.lastname: Wu
authors.affiliation: Kaohsiung Municipal Kai-Syuan Psychiatric Hospital, Taiwan.
authors.forename: Su-Ting
authors.initials: ST
authors.lastname: Hsu
authors.affiliation: Department of Psychiatry, Kaohsiung Chang Gung Memorial Hospital and Chang Gung University College of Medicine, Kaohsiung, Taiwan.
authors.forename: Chien-Chih
authors.initials: CC
authors.lastname: Chen
authors.affiliation: Department of Psychiatry, Kaohsiung Chang Gung Memorial Hospital and Chang Gung University College of Medicine, Kaohsiung, Taiwan.
authors.forename: Mian-Yoon
authors.initials: MY
authors.lastname: Chong
authors.affiliation: Department of Psychiatry, Kaohsiung Chang Gung Memorial Hospital and Chang Gung University College of Medicine, Kaohsiung, Taiwan.
authors.forename: Chieh-Hsin
authors.initials: CH
authors.lastname: Lin
authors.affiliation: Department of Psychiatry, Kaohsiung Chang Gung Memorial Hospital and Chang Gung University College of Medicine, Kaohsiung, Taiwan. Electronic address: chifa@cgmh.org.tw.
authors.forename: Chi-Fa
authors.initials: CF
authors.lastname: Hung
mesh_terms: D000328:Adult; D000368:Aged; D001786:Blood Glucose / Q000378:metabolism; D016022:Case-Control Studies; D003072:Cognition Disorders / Q000209:etiology*; D003430:Cross-Sectional Studies; D003545:Cysteine / Q000097:blood*; D056344:Executive Function / Q000502:physiology; D005215:Fasting / Q000097:blood; D005260:Female; D006801:Humans; D008297:Male; D008568:Memory / Q000502:physiology; D008875:Middle Aged; D009483:Neuropsychological Tests; D011569:Psychiatric Status Rating Scales; D012559:Schizophrenia / Q000097:blood* / Q000175:diagnosis*; D012565:Schizophrenic Psychology; D014706:Verbal Learning / Q000502:physiology
chemical_list: D001786:Blood Glucose; D003545:Cysteine
keywords: Amino acid; Antioxidant; Cognition; Cysteine; Metabolite; Schizophrenia