Gray matter volume abnormalities in type 2 diabetes mellitus with and without mild cognitive impairment

• Widespread GM atrophy was found in T2DM patients both with and without MCI.
• MTL atrophy was found with the occurrence of the MCI in T2DM patient.
• MTG atrophy might be associated with an increased risk for MCI in T2DM.

This study sought to evaluate the potential brain gray matter (GM) volume changes that occur with the transition from normal cognition to mild cognitive impairment (MCI) in patients with type 2 diabetes mellitus (T2DM) using voxel-based morphometry (VBM). VBM analyses of brain GM based on magnetic resonance imaging (MRI) data were performed on 28 T2DM patients with MCI, 25 T2DM patients without MCI, 28 MCI patients and 29 healthy controls (HC). Compared with the HC, the T2DM patients both with and without MCI showed significantly decreased total GM volume. Furthermore, the VBM results indicated that the T2DM patients without MCI exhibited extensively decreased GM volume compared with the HC in certain brain regions, including the superior and middle temporal gyrus (MTG), the superior and medial frontal gyrus and the middle occipital gyrus. In addition to more extensive GM atrophy in the aforementioned brain regions, the medial temporal lobe also exhibited GM loss in the T2DM patients with MCI. Furthermore, relative to the patients without MCI, only the left MTG exhibited a lower GM volume in the T2DM patients with MCI, which was positively correlated with the total MoCA score (r = 0.699, P < 0.01). Finally, relative to MCI, the left MTG atrophy was also found in the T2DM patients with MCI. Our findings suggest that MTG atrophy was associated with an increased risk for MCI in T2DM patients. The brain structural changes in many brain regions may underlie the transition from normal cognition to MCI in T2DM patients.