OBJECTIVETo elucidate the volume changes of cortical and subcortical reward circuitry in patients with type 2 diabetes mellitus.

METHODSHigh-resolution three-dimensional T1-weighted fast spoiled gradient recalled echo MRI images were obtained from 16 patients with type 2 diabetes mellitus and 16 normal controls, and 11 type 2 diabetic patients also received the same MRI scans after insulin therapy for 1 year. Volumetric analysis was performed and analysis of covariance and paired t test were applied.

RESULTSA decreased volume was found in the left insular lobe, left nucleus accumbens area, right hippocampus, putamen and amygdala in type 2 diabetic patients compared with normal controls (P<0.05). After insulin therapy for 1 year, an increased volume of bilateral cortical reward structures was observed (left, 33.65∓3.66 ml; right, 33.35∓4.25 ml) compared the baseline level (left, 31.45∓2.90 ml; right, 31.12∓2.97 ml) in diabetic patients (P<0.05). No significant volume change in the bilateral basal ganglia structures was found after insulin therapy for 1 year (P>0.05), and bilateral ventral diencephalon area showed an increased volume after the treatment (left, 3.26∓0.68 ml; right, 3.20∓0.78 ml) compared with the baseline (left, 2.96∓0.76 ml; right, 2.82∓0.90 ml)(P<0.05).

CONCLUSIONType 2 diabetic patients have a decreased volume of the cortical and subcortical reward circuitry, and insulin therapy can reverse such changes and improve the damage of reward circuitry.