Elevated levels of kynurenic acid in the cerebrospinal fluid of patients with bipolar disorder.
BACKGROUND
Patients with schizophrenia show elevated brain levels of the neuroactive tryptophan metabolite kynurenic acid (KYNA). This astrocyte-derived mediator acts as a neuroprotectant and modulates sensory gating and cognitive function. We measured the levels of KYNA in the cerebrospinal fluid (CSF) of patients with bipolar disorder and healthy volunteers to investigate the putative involvement of KYNA in bipolar disorder.


METHODS
We obtained CSF by lumbar puncture from 23 healthy men and 31 euthymic men with bipolar disorder. We analyzed the samples using high-performance liquid chromatography.


RESULTS
Patients with bipolar disorder had increased levels of KYNA in their CSF compared with healthy volunteers (1.71 nM, standard error of the mean [SEM] 0.13 v. 1.13 nM, SEM 0.09; p = 0.002. The levels of KYNA were positively correlated with age among bipolar patients but not healthy volunteers.


CONCLUSIONS
The influence of ongoing drug treatment among patients cannot be ruled out. We conducted our study during the euthymic phase of the disease.


CONCLUSIONS
Brain KYNA levels are increased in euthymic men with bipolar disorder. In addition, KYNA levels increased with age in these patients. These findings indicate shared mechanisms between bipolar disorder and schizophrenia. Elevated levels of brain KYNA may provide further insight to the pathophysiology and progression of bipolar disorder.
Olsson
Sara K
SK
Department of Physiology and Pharmacology, Karolinska Institutet, Stockholm, Sweden.
Samuelsson
Martin
M
Saetre
Peter
P
Lindström
Leif
L
Jönsson
Erik G
EG
Nordin
Conny
C
Engberg
Göran
G
Erhardt
Sophie
S
Landén
Mikael
M
D000328:Adult; D000367:Age Factors; D001714:Bipolar Disorder / Q000134:cerebrospinal fluid* / Q000175:diagnosis / Q000523:psychology*; D016022:Case-Control Studies; D002851:Chromatography, High Pressure Liquid; D039721:Diagnostic and Statistical Manual of Mental Disorders; D005260:Female; D006801:Humans; D007736:Kynurenic Acid / Q000134:cerebrospinal fluid*; D008297:Male; D008875:Middle Aged; D012720:Severity of Illness Index
D007736:Kynurenic Acid