Is oxidative stress in the brain correlated with plasma markers of oxidative stress?

Oxidative stress in the brain may contribute to the onset and progression of mental health disorders. Markers of oxidative stress in serum or blood plasma have been used to predict cognitive decline or identify subjects at risk of developing neurodegenerative disease. However, plasma markers of oxidative stress are rarely directly linked to patterns of oxidative stress in the brain in the same study. Here, we assessed whether peripheral markers of oxidative stress were positively linked to oxidative stress measurements from several macrodissected brain divisions in a highly social cichlid fish, Astatotilapia burtoni. We generated composite measures of brain oxidative stress marker variation by performing principal component analysis on brain markers including oxidative DNA damage (8-OHdG), total antioxidant capacity (TAC), and glutathione levels measured across four brain divisions in dominant and subordinate males. We found that plasma oxidative damage, measured as derivatives of reactive oxygen metabolites (d-ROMs), was not significantly associated with the first two principal components representing brain oxidative stress marker patterns. The link between plasma total antioxidant capacity and brain oxidative stress patterns (PC1 and PC2) varied between dominant and subordinate individuals, but within these social states there were no significant associations between plasma TAC and brain oxidative stress marker patterns. Our study suggests that plasma markers of oxidative stress are poor predictors of individual oxidative stress levels in specific brain divisions.