Clinical subtyping reveals significant differences in calcium-dependent phospholipase A(2) activity in schizophrenia

Background: Inconsistent results in the study of phospholipid metabolism in schizophrenia may reflect the heterogeneous nature of the illness(es). Dif ferences in patients' responses to niacin, a compound causing vasodilation via stimulation of phospholipid dependent signaling cascades, defines more homogeneous patient subgroups in which the rare limiting enzyme of this sig naling pathway, phospholipase A(2) (PLA(2)), can be studied. Methods: Subjects were categorized as niacin-insensitive (10 schizophrenic patients and 1 control) or niacin-sensitive (13 schizophrenic patients and 29 controls). Comparisons of serum calcium-dependent PLA(2) were undertaken with and without consideration of niacin sensitivity. Results: Significantly more schizophrenic patients were niacin-insensitive than controls (chi(2)(1) = 12.8, p < .001). Comparison of mean serum calciu m-dependent PLA(2) level of all schizophrenic subjects with all healthy con trols revealed no statistical difference (t(51) = .79, NS). Sub-typing the schizophrenia group by niacin sensitivity/insensitivity, however, allowed s ignificant differences to emerge (F(2,49) = 4.40, p = .018). Post-hoc tests showed the mean PLA, activity level of niacin-sensitive subjects was lower than that of healthy subjects, Conclusions: Treatment strategies which increase calcium-dependent PLA(2) a ctivity may aid in reducing states of excess dopaminergic activity by activ ating second messenger systems rather than receptor blockade. Biol Psychiat ry 1999;46:401-405 (C) 1999 Society of Biological Psychiatry.