Schizophrenia (SCZ) is a chronic mental disorder that affects around 1 in 300 people. The exact cause of SCZ remains to be elucidated; however, it is likely a combination of events that contributes to the pathogenesis of this disease. Some genetic risk factors for SCZ are pro-inflammatory factors. In fact, research has demonstrated an increased inflammatory state in individuals with SCZ. Additionally, schizophrenia has been associated with a reduction in gray matter volume.
Inflammatory states can alter kynurenine pathway (KP) activity. Therefore, in a recent study published by Dr. Sumiao Zhou and colleagues in Frontiers in Psychiatry, they investigated KP metabolite levels and gray matter volume. In this study, 41 SCZ patients and 60 controls were recruited from Guangzhou, China. Plasma kynurenic acid levels were significantly increased in SCZ patients, as well as the kynurenic acid/ kynurenine ratio. Interestingly, these KP metabolites were negatively correlated with gray matter volume in schizophrenia patients. High kynurenine levels were correlated with decreased gray matter volume in the left anterior cingulate gyrus which has been previously associated with psychosis (Morgan et al., 2018). Low gray matter volume in bilateral insula was negatively correlated with kynurenine/tryptophan ratio. This relationship between gray matter volume and KP metabolites should be further investigated in a larger cohort study.