Subcortical gray matter structural alterations in prediabetes and type 2 diabetes

Type 2 diabetes (T2D) is a risk factor for cognitive impairment and potentially Alzheimer's disease. However, the precise mechanism underlying the effects of glucose on brain abnormalities is not fully understood. The differential effects of glucose alteration on brain changes in patients with T2D and those with prediabetes are also unclear. MRI data were collected from 21 patients with T2D (male/female, 7/14); 21 patients with prediabetes (male/female, 8/13); and 21 age-matched, sex-matched, and education-matched normal controls (male/female, 7/14). MRI data were analyzed using the Freesurfer software to obtain subcortical gray matter (GM) structural volumes. Spearman correlation analysis was performed between GM structural volume and clinical data. Reduced subcortical GM volumes were found in patients with prediabetes and those with T2D in the bilateral lateral hippocampus, left amygdala, and right putamen compared with healthy controls. In addition, postprandial blood sugar remained significantly associated with GM volume in the left hippocampus of patients with T2D. Our results indicate that prediabetes is not the harmless condition that it was previously thought to be, that impaired glycemia negatively affects the structures of the brain, and that long-lasting hyperglycemia accelerates brain atrophy in patients with T2D.