Association between MnSOD Activity and Cognitive Impairment in Unmedicated First-Episode Schizophrenia: Regulated by MnSOD Ala-9Val Gene Polymorphism

Abstract

The imbalance between pro-oxidants and antioxidants is thought to be responsible for aging and cognitive impairment in many degenerative diseases, including schizophrenia (SZ). As the first antioxidant enzyme to detoxify superoxide radicals in mitochondria, manganese superoxide dismutase (MnSOD) activity and its functional polymorphism of Ala-9Val have been found to be associated with SZ. In this study, we explored the association between MnSOD activity, MnSOD Ala-9Val polymorphism and cognitive dysfunction in unmedicated first-episode (UMFE) SZ patients, which has not been examined. We recruited 234 UMFE SZ patients and 232 healthy controls (HC) and evaluated them with Repeated Battery for the Assessment of Neuropsychological Status (RBANS), plasma MnSOD activity and MnSOD Ala-9Val (rs4880) polymorphism. In addition, we used the Positive and Negative Syndrome Scale (PANSS) to assess the severity of patients’ psychopathological symptoms. Compared with HC, UMFE patients showed extensive cognitive impairment on RBANS, and had higher MnSOD activity. MnSOD Ala-9Val polymorphism was not associated with SZ susceptibility and cognitive impairment, but only affected MnSOD activity in patients. Moreover, only in SZ patients with Val homozygotes, MnSOD activity was significantly correlated with cognitive impairment, especially in RBANS total score, visuospatial/constructional and attention index scores. Our results suggest that cognitive impairment is associated with MnSOD activity in patients with first-episode SZ, which may be regulated by MnSOD Ala-9Val polymorphism.