Structural connectivity of hippocampus is not altered in patients with type 2 diabetes and without peripheral microangiopathy.

Functional hyper-connectivity in hippocampus has been recently observed in patients with an early stage of type 2 diabetes, however, the structural connectivity between hippocampus and other regions of the brain and its effects on neuropsychological performance are still unknown. Participants (82 patients with type 2 diabetes and without peripheral microvascular complications; 75 healthy controls) underwent detailed cognitive assessment and diffusion MRI. Probabilistic tractography based on a multifiber model was performed to investigate the fiber connections between hippocampus and other regions of the brain. The differences in hippocampal connectivity between groups were compared with age, sex, body mass index and education as covariates. The association between hippocampal connectivity and cognitive performances in patients with diabetes were further investigated. Patients had lower Stroop Accuracy and longer Stroop Reaction Time compared with age-, sex-, education-matched controls. Although lower hippocampal connectivities to widespread brain regions were observed in diabetic group, there were no statistical differences after FDR adjustment. Moreover, the strength of fiber connections was not associated with any cognitive performance in patients with diabetes. Taken together, worse executive function was observed in patients with an early stage of type 2 diabetes. However, it might not be related to hippocampal fiber connectivity. These findings suggested that structural connectivity in hippocampus was not an early predictor for diabetes-associated cognitive decrements.