Background: 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.
Methods: 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.
Results: 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.
Conclusions: 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.
Keywords: Amino acid; Antioxidant; Cognition; Cysteine; Metabolite; Schizophrenia.
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