Agmatine is an endogenous substance, synthesized from
l-arginine, and it is proposed to be a new
neurotransmitter. Preclinical studies indicated that
agmatine may have an important role in the pathophysiology of
schizophrenia. This study was organized to investigate plasma
agmatine in patients with
schizophrenia and in healthy controls. Eighteen patients with
schizophrenia and 19 healthy individuals constituted the subjects.
Agmatine levels in the plasma were measured using the HPLC method. The S100B
protein level, which is a peripheral
biomarker for brain damage, was also measured using the ELISA method. While plasma levels of
agmatine in patients with
schizophrenia were significantly increased (p < 0.0001) compared to those of healthy individuals (control), there were no significant changes in the levels of S100B
protein (p = 0.660). An ROC (receiver operating characteristic) curve analysis revealed that measuring plasma
agmatine levels as a clinical diagnostic test would significantly differentiate between patients with
schizophrenia and those in the control group (predictive value: 0.969; p < 0.0001). The predictive value of S100B measurements was not statistically significant (p > 0.05). A multiple regression analysis revealed that the age of the patient and the severity of the illness, as indicated by the PANSS score, significantly contributed the plasma
agmatine levels in patients with
schizophrenia. These results support the hypothesis that an excess
agmatine release is important in the development of
schizophrenia. The findings also imply that the plasma
agmatine level may be a potential
biomarker of
schizophrenia.