Increased cortical kynurenate content in schizophrenia

Area of Science:

• Neuroscience
• Biochemistry
• Psychiatry

Background:

• The kynurenine pathway (KP) of tryptophan degradation produces metabolites influencing brain function.
• Key metabolites include kynurenine, kynurenate (a glutamate antagonist), and 3-hydroxykynurenine.
• Alterations in KP metabolism may contribute to brain diseases like schizophrenia, potentially through effects on glutamate signaling.

Purpose of the Study:

• To investigate kynurenine pathway metabolite levels in the brains of individuals with schizophrenia.
• To determine if specific KP metabolites are altered in cortical regions relevant to schizophrenia.

Main Methods:

• Quantified tissue levels of kynurenine, kynurenate, and 3-hydroxykynurenine in post-mortem brain samples.
• Analyzed samples from three cortical regions (Brodmann areas 9, 10, 19) of 30 schizophrenic and 31 control subjects.
• Assessed the impact of chronic haloperidol treatment on kynurenate levels in rat brains.

Main Results:

• Significantly elevated kynurenate levels were found in Brodmann area 9 of schizophrenic brains.
• Kynurenine levels were elevated in Brodmann areas 9 and 19 in schizophrenic cases.
• No significant differences in 3-hydroxykynurenine were observed; haloperidol did not increase kynurenate in rats.

Conclusions:

• Schizophrenia is associated with an impairment in brain kynurenine pathway metabolism.
• Elevated kynurenate levels suggest a potential reduction in glutamate receptor function in schizophrenia.
• These findings highlight the KP as a potential factor in schizophrenia pathophysiology.