Plasma kynurenine and related measures in tic disorder patients.
OBJECTIVE
Increased plasma kynurenine has been reported in tic disorder patients, and this observation has been suggested to be indicative of immune dysregulation. In the present study, we examined plasma levels of kynurenine and related molecules in a group of tic disorder patients.


METHODS
Plasma concentrations of tryptophan, kynurenine, cortisol, and neopterin were determined in Dutch tic disorder patients (N = 59), and healthy volunteers (N = 32). Group means were compared and age-controlled intra-individual correlations between tic severity and plasma levels of these molecules were examined.


RESULTS
No significant differences were found between patient and control groups in plasma levels of tryptophan, kynurenine, and cortisol concentrations, nor in the kynurenine/tryptophan ratio. However, neopterin was significantly (p = 0.035) higher in patients (mean = 5.13 nmol/l) than in controls (mean = 3.30 nmol/l). Plasma levels of these molecules did not correlate with tic severity, with the exception of tryptophan (r = -0.289, p = 0.049). In patients, plasma neopterin correlated with kynurenine (r = 0.438, p = 0.002); in healthy subjects, tryptophan correlated with kynurenine (r = 0.670, p < 0.001).


CONCLUSIONS
While the observed elevation in plasma neopterin is consistent with immune activation in a subset of tic disorder patients, metabolism of tryptophan through the kynurenine pathway appears to be unaltered in tic disorder patients.
Department of Psychiatry, University Medical Center Groningen, University of Groningen, P.O. Box 660, 9700 AR, Groningen, The Netherlands. p.hoekstra@accare.nl
Pieter J
PJ
Hoekstra
George M
GM
Anderson
Pieter W
PW
Troost
Cees G M
CG
Kallenberg
Ruud B
RB
Minderaa
D000293:Adolescent; D000328:Adult; D016022:Case-Control Studies; D002648:Child; D002675:Child, Preschool; D005260:Female; D006801:Humans; D006854:Hydrocortisone / Q000097:blood; D007737:Kynurenine / Q000097:blood*; D008297:Male; D008875:Middle Aged; D019798:Neopterin / Q000097:blood*; D013981:Tic Disorders / Q000097:blood* / Q000276:immunology; D014364:Tryptophan / Q000097:blood / Q000378:metabolism
D007737:Kynurenine; D019798:Neopterin; D014364:Tryptophan; D006854:Hydrocortisone