Kynurenic acid levels increased in bipolar patients with psychotic features

By Mark Cowen, Senior medwireNews Reporter

Bipolar disorder patients with a history of psychotic features have higher cerebrospinal fluid concentrations of kynurenic acid (KYNA) than those without such features, research shows.

Mikael Landén (University of Gothenburg, Sweden) and team found that cerebrospinal fluid KYNA levels were around 30% higher in bipolar disorder patients with psychotic features than in their nonpsychotic counterparts.

"Although the causality needs to be determined, the ability of KYNA to influence dopamine transmission and behavior, along with previous reports showing increased brain levels of the compound in patients with schizophrenia and bipolar disorder, may indicate a possible pathophysiological role of KYNA in the development of manic or psychotic symptoms," they say.

The findings come from a study of 55 euthymic bipolar I disorder patients (21 men), of whom 43 had a history of psychotic features.

High-performance liquid chromatography (HPLC) was used to assess KYNA levels in cerebrospinal fluid collected from the participants after a night of fasting and bed rest.

The team found that patients with a history of psychotic features had higher mean cerebrospinal fluid levels of KYNA (2.0 nm) than those without (1.3 nm).

Indeed, logistic regression analysis revealed that patients with a history of psychotic features were 4.9 times more likely to have higher KYNA levels than those without.

The researchers also found that increased KYNA levels were significantly associated with a recent manic episode within the previous year, even after adjustment for a lifetime history of psychotic features (odds ratio=4.1).

"The present results show that KYNA is associated with a lifetime history of psychotic features and the recent occurrence of a manic episode in euthymic patients with bipolar I disorder," Landén et al conclude in Bipolar Disorders.

They add that if a pathophysiologic role of KYNA in psychotic features and mania is established, it may "give rise to novel therapeutic targets in the treatment of the disease."

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