Myeloperoxidase gene expression and cognitive functions in depression

PurposeMost researchers agree that there are multiple factors influencing the development of recurrent depressive disorder (rDD). Previous studies have found that myeloperoxidase (MPO) may be a key inflammatory enzyme involved in this disorder. The purpose of this study was to determine the mRNA and protein levels of MPO in patients with rDD and to define the relationship between serum MPO levels and cognitive performance.Material/methodsThe study comprised 236 subjects: patients with rDD (n = 131) and healthy subjects (n = 105, HS). Assessment of cognitive function was based on performance on the Trail Making Test, the Stroop Test, the Verbal Fluency Test (VFT) and the Auditory–Verbal Learning Test (AVLT).ResultsMPO gene expression at mRNA level and at protein level was significantly higher in the rDD group when compared to the HS (p < 0.01). There were no significant correlations for each group separately, but in the entire group, statistically significant correlations occurred between both mRNA and protein levels and following test: TMT part A and part B (positive correlations), part RCNb and part NCWd of the Stroop Test (positive correlation), the Verbal Fluency Test (negative correlation) and the AVLT (negative correlation).ConclusionsOur study provides evidence that the MPO enzyme coding gene and MPO expression are important for the regulation of cognitive functioning.