Normal metabolite levels in the left dorsolateral prefrontal cortex of unmedicated major depressive disorder patients: A single voxel ¹H spectroscopy study

Abstract 

Few proton magnetic resonance spectroscopy (¹H spectroscopy) studies have investigated the dorsolateral prefrontal cortex (DLPFC), a key region in the pathophysiology of major depressive disorder (MDD). We used ¹H spectroscopy to verify whether MDD patients differ from healthy controls (HC) in metabolite levels in this brain area. Thirty-seven unmedicated DSM-IV MDD patients were compared with 40 HC. Subjects underwent a short echo-time ¹H spectroscopy examination at 1.5 T, with an 8-cm³ single voxel placed in the left DLPFC. Reliable absolute metabolite levels of N-acetyl aspartate (NAA), phosphocreatine plus creatine (PCr+Cr), choline-containing compounds (GPC+PC), myo-inositol, glutamate plus glutamine (Glu+Gln), and glutamate were obtained using the unsuppressed water signal as an internal reference. Metabolite levels in the left DLPFC did not statistically differ between MDD patients and HC. We found an interaction between gender and diagnosis on PCr+Cr levels. Male MDD patients presented lower levels of PCr+Cr than male HC, and female MDD patients presented higher levels of PCr+Cr than female HC. Moreover, length of illness was inversely correlated with NAA levels. These findings suggest that there is not an effect of diagnosis on the left DLPFC neurochemistry. Possible effects of gender on PCr+Cr levels of MDD patients need to be further investigated.

Keywords: Major depressive disorder, Magnetic resonance spectroscopy, Prefrontal cortex, Pathophysiology, N-acetyl aspartate, Choline-containing compounds, Glutamate, Phosphocreatine/creatine