Age-related changes of superoxide dismutase activity in patients with schizophrenia.

Background/Aim: Superoxide dismutase (SOD) is the critical enzyme in the detoxification of superoxide radicals because those are the first species produced in the majority of biological free radical producing reactions. Inconsistent data are present about SOD activity in patients with schizophrenia. Numerous studies have shown that SOD has been elevated in chronic schizophrenic patients. However, decreased SOD activity was found in neuroleptic naïve, first episode schizophrenic patients, in chronic-medicated patients and in chronic-unmedicated patients. The aim of this study was to examine which of the following factors including age, gender, the onset of the disease, the duration, the number of episodes, heredity, psychopathologic symptoms and drug treatment could affect erythrocyte SOD activity in patients with schizophrenia.

Methods: This study included 68 consecutive patients with schizophrenia (29 males and 39 females) ranging in age from 18 to 61 years, divided into two age groups (<34 years and >34 years). SOD activity was measured in erythrocyte hemolyzates by Ransod commercially available test.

Results: In the group of patients younger than 34 years SOD levels were significantly higher (1381±273 U/gHb, p=0.038) compared to the levels of the older group (1231±206 U/gHb). Gender and heredity did not induce any significant difference in SOD activity between younger and older subgroups. A significant difference in enzyme activity was found between the younger and older subgroups having the onset of the disease after 24 years of age (1408±217 U/gHb vs. 1252±213 U/gHb, p=0.031). The patients of the younger group who had more than one psychotic episode had significantly higher SOD activity (1492±298 U/gHb; p=0.009) than those who had only one episode (1256±177 U/gHb), as well as than the older subgroup with more than one episode (1253±231 U/gHb; p=0.014). Although the duration of the disease did not induce any significant difference in enzyme activity between younger and older subgroups, a significant negative correlation was obtained between SOD activity and the duration of the disease (r=-0.511, p<0.01). No significant differences were found in SOD activity between the subgroups with different PANSS scores. First generation antipsychotics were associated with elevated enzyme activity in both groups. Simultaneous treatment of patients with first generation antipsychotics and second generation antipsychotics induced a significant decrease in SOD activity in the younger group.

Conclusion: Our results show that erythrocyte SOD activity is increased in the early phase of schizophrenia and that depends on age of onset of the disease, the number of psychotic episodes, the duration of the disease and medical treatment.