Decreased prefrontal Myo-inositol in major depressive disorder

Background: Postmortem studies have shown robust prefrontal cortex glial losses and more subtle neuronal changes in major depressive disorder (MDD). Earlier proton magnetic resonance spectroscopy (H-1-MRS) studies of the glial marker myo-inositol in MDD were subject to potential confounds. The primary hypothesis of this study was that MDD patients would show reduced prefrontal/anterior cingulate cortex levels of myo-inositol. Methods: Thirteen nonmedicated moderate-severe MDD patients and 13 matched control subjects were studied (six male, seven female per group). Proton magnetic resonance spectroscopy stimulated echo acquisition mode spectra (3.0 T, echo time = 168 msec: mixing time = 28 msec; repetition time = 3000 msec) were obtained from prefrontal anterior cingulate cortex. Metabolite data were adjusted for tissue composition. Results: Patients with MDD showed significantly lower myo-inositol creatine rations (.94 +/- .23) than control subjects (1.32 +/- .31) [F(1.23) = 6.9: p = .016]. Conclusions: These data suggest a reduction of myo-inositol in prefrontal anterior cingulate cortex in MDD, which could be a consequence of glial loss or altered glial metabolism. Additional in vivo studies of glial markers could add to the understanding of the pathophysiology of MDD.