Network efficiency of functional brain connectomes altered in type 2 diabetes patients with and without mild cognitive impairment.

Aim: To explore the topological organization alterations of functional connectomes in type 2 diabetes (T2DM) patients with and without mild cognitive impairment (MCI), and compare these with structural connectomes changes.

Methods: Twenty-six T2DM patients with MCI (DM-MCI), 26 without cognitive impairment (DM-NC), and 28 healthy controls were included. Diffusion tensor imaging (DTI) and resting-state functional MRI images were acquired. Networks were constructed and graph-theory based network measurements were calculated. The global network parameters and nodal efficiencies were compared across the three groups using one-way ANOVA and a false-discovery rate correction was applied for multiple comparisons. Partial correlation analyses were performed to investigate relationships between network parameters, cognitive performance and clinical variables.

Results: In the structural connectome, the DM-MCI group exhibited significantly decreased global efficiency (E_glob) and local efficiency (E_loc) compared to the DM-NC and control groups. In the functional connectome, the DM-MCI group exhibited increased E_loc and clustering coefficient (Cp) compared to the controls. No significant differences were found in E_glob, E_loc, or Cp between the DM-NC and the control group, both in structural and functional connectomes. Nodal efficiencies decreased in some brain regions of structural and functional networks in the DM-MCI and DM-NC groups, but increased in five regions in functional network, some of which were involved in the default-mode network.

Conclusion: Unlike the consistently decreased global properties and nodal efficiencies in the structural connectome of T2DM patients, increases in E_loc, Cp, and nodal efficiencies in the functional connectome may be viewed as a compensatory mechanism due to functional plasticity and reorganization. Altered nodal efficiency can hint at cognitive decrements at an early stage in T2DM patients.