Plasma glutathione suggests oxidative stress is equally present in early- and late- onset bipolar disorder

Abstract

We previously demonstrated oxidative stress in bipolar patients and a relationship between the age of illness onset and total glutathione, a principal antioxi- dant. In this study, we sought to replicate these findings in a new cohort of patients. Methods: We recruited bipolar patients from Warneford Hospital, Oxford, UK, of similar age and grouped them according to age of onset of illness. The early- onset group comprised patients with onset at <23 years, and the late group comprised pa- tients with onset at >30 years. A third group, comprising age- matched healthy volun- teers, was also included. Reduced and oxidized glutathione, cysteine, and cystine were determined in plasma, using high- performance liquid chromatography. Mitochondrial DNA copy number, measured in whole blood, was also compared be- tween patients and healthy controls. Results: Significant increases in oxidative stress were observed in the patient groups, compared with the control group; however, no differences in glutathione- related oxi- dative stress measures were detected between the early- and late- onset bipolar pa- tient groups. No differences were observed in the amount of mitochondrial DNA, and there was no correlation with mood state. Conclusion: Using a more accurate method to quantify oxidative stress than in our previous study, we show that oxidative stress is a consistent feature of bipolar disor- der. Although we did not reproduce our finding correlating age of onset of illness to oxidative stress, we have shown, once again, that oxidative stress is a consistent fea- ture of bipolar disorder