Diabetes status associates with entorhinal cortical thinning in Parkinson's disease.

OBJECTIVE: Our study aimed to investigate cortical thickness (CT) alterations in Parkinson's disease (PD) patients with and without diabetes mellitus (DM), and explore the correlation between DM, CT, and cognitive function. METHODS: A total of 135 participants were enrolled, including 16 PD patients with DM (PD-DM), 87 PD patients without DM (PD-nonDM), and 32 healthy controls (NC). All participants underwent 3.0T MRI, and CT was analyzed using Computational Anatomy Toolbox (CAT). Clinical data and blood parameters were also collected. Group differences were assessed with covariate-adjusted t-tests, and correlations between DM, CT, and Mini-Mental State Examination (MMSE) scores were analyzed using partial Spearman correlation and multiple regression. RESULTS: No significant clinical differences between PD-DM and PD-nonDM were observed. Compared with NC, PD-nonDM showed cortical thinning in the left orbitofrontal cortex, and PD-DM group exhibited reduced CT in the right parahippocampal and entorhinal regions, after adjusting for confounding factors. Compared with PD-nonDM, PD-DM patients revealed significant cortical thinning in bilateral entorhinal cortex. DM status was correlated with bilateral entorhinal CT (left: partial r=-0.227, p=0.022; right: partial r=-0.209, p=0.036), but not MMSE, after controlling for age and sex ratio. MMSE scores positively correlated with CT in the left inferior parietal and right parahippocampal gyrus (FWE corrected, k > 100 voxels). INTERPRETATION: DM is associated with cortical thinning in cognitive-related regions (especially the entorhinal cortex) in PD, potentially before significant cognitive decline captured by MMSE. These findings provide insights into PD with DM mechanisms.