[Could we use a serum level of glycine as a prognostic factor of its efficacy in schizophrenic patients?].
Glutamatergic system--the main excitatory brain system is involved in the pathophysiology of schizophrenia. The ionotropic glutamatergic NMDAreceptor participates in mechanisms of controlling neurotransmitter systems such as the dopaminergic, noradrenergic, serotoninergic ones and plays an important role in cognitive functioning. Glycine is a natural coagonist of the NMDA receptor and according to the hypoNMDA hypothesis treatment with its high doses (max. 60g orally per day) can improve symptomatology of schizophrenia, e.g., negative symptoms and cognitive functions.


OBJECTIVE
If there is a correlation between plasma levels (before and after using glycine) and severity of symptoms (at the first and last assessment), then low baseline plasma concentrations could be an indication for choosing glycine in treatment, moreover a useful prognosing tool and finally a support of glutamatergic hypothesis of schizophrenia.


METHODS
28 patients with a diagnosis of schizophrenia according to ICD-10 diagnostic criteria (Table 1) in stable clinical condition and antipsychotic medication (typical and atypical agents) for min. 3 months, had completed a 6 week, prospective and open label study (32 patients enrolled). Between 2 visits patients received glycine in high oral doses (0.8 g/kg/day). Before and afterwards the glycine treatment, psychiatric and cognitive function examination was performed based on PANSS, Trail making test (TMT), Stroop test and Wisconsin card sorting test (WCST). In parallel glycine plasma levels were assessed.


RESULTS
There was a significant reduction in positive, negative, general psychopathology and total PANSS score during the study (Table 2). Also cognitive parameters significantly improved during 6 weeks of glycine use. Serum levels of glycine were markedly higher at the end of our project, but only improvement in part 2 of TMT correlates with changes in aminoacid serum concentrations (p = 0.02).


CONCLUSIONS
Our results suggest that augmentation of antipsychotic treatment (typical and atypical neuroleptics) with glycine can have a positive influence on schizophrenic symptoms there in cognitive dysfunction, but glycine plasma levels were not a useful predictor of recovery in our patients. Correlation between improvement in performance of TMT and serum level increase suggests that glycine and NMDA receptor can be involved in psychopathology of schizophrenia and cognitive functioning, e.g., working memory
Strzelecki
Dominik
D
Klinika Zaburzeńi Afektywnych i Psychotycznych Centralnego Szpitala Klinicznego UM w Łodzi.
Rabe-Jabłońska
Jolanta
J
D000328:Adult; D000596:Amino Acids / Q000097:blood; D014150:Antipsychotic Agents / Q000008:administration & dosage*; D003071:Cognition / Q000187:drug effects*; D004305:Dose-Response Relationship, Drug; D004334:Drug Administration Schedule; D005260:Female; D005998:Glycine / Q000008:administration & dosage*; D006801:Humans; D008297:Male; D011446:Prospective Studies; D011569:Psychiatric Status Rating Scales; D012559:Schizophrenia / Q000097:blood / Q000188:drug therapy*; D012565:Schizophrenic Psychology; D012720:Severity of Illness Index; D016896:Treatment Outcome
D000596:Amino Acids; D014150:Antipsychotic Agents; D005998:Glycine