Prefrontal myo-inositol concentration and visuospatial functioning among diabetic depressed patients

Patients with diabetes mellitus are reported to be at higher risk for developing neuropsychiatric disorders such as dementia and depression. Myo-inositol (mI), a neuronal/glial metabolite associated with multiple functions in the brain, has been shown to be increased in cognitive disorders, depression and diabetes. This study examined whether elevations in dorsolateral (DL) mI of diabetic patients with depression were associated with visuospatial deficits. Diabetic and depressed patients (n=18) were matched with patients with diabetes but without depression (n=20) and control subjects (n=19). Subjects were scored on both the recall and recognition tasks of the Rey-Osterreith Complex Figure (ROCF). Proton magnetic spectroscopy spectra from bilateral prefrontal white matter voxels were used to obtain concentrations of mI. Controls showed negative correlations between mI in right DL white matter and recall and recognition subtests. No correlation was observed for depressed diabetic patients. Correlations for diabetic controls fell midway between the comparison and depressed diabetic groups. The expected pattern of association between mI and visuospatial impairment in the right DL prefrontal region was seen among healthy controls. Progressive weakening of this association across both diabetic groups might be related to progressive changes in neural activity that underlies visuospatial function.