Region-specific hippocampal atrophy is correlated with poor glycemic control in type 2 diabetes: a cross-sectional study

To examine the association between prediabetes/type 2 diabetes mellitus (T2DM) and hippocampal subfields and to investigate the effects of glycemic control (HbA1c and FBG)/diabetes duration on the volume of hippocampal subfields in T2DM patients. This cross-sectional study included 268 participants from Tianjin Union Medical Center between August 2019 and July 2022. The participants were divided into three groups: T2DM, prediabetes and no diabetes. All participants underwent brain MRI examination on a 3T MRI scanner. FreeSurfer was performed to segment hippocampus automatically based on T1 MPRAGE images. The relationships between glycemic status/glycemic control/diabetes duration and hippocampal subfield volumes were estimated by multiple linear regression analysis/generalized additive modeling (GAM). Among all participants, 76 (28.36%) had prediabetes, and 96 (35.82%) had T2DM. In multi-adjusted linear regression models, those with prediabetes had a significantly lower volume of bilateral parasubiculum (beta right = -5.540; beta left = -6.497). Those with diabetes had lower volume of parasubiculum (beta left = -7.868), presubiculum-head (beta left = -6.244) and fimbria (beta left = -7.187). We did not find relationship between diabetes duration and hippocampal subfield volumes. In stratified analysis, long duration with high FBG related with lower volume of right fimbria (beta right = -15.583). Long duration with high HbA1c related with lower volume of presubiculum-head (beta right = -19.693), subiculum-head (beta right = -28.303), subiculum-body (beta left = -38.599), CA1-head (beta right = -62.300, beta left = -47.922), CA1-body (beta right = -19.043), CA4-body (beta right = -14.392), GC-ML-DG-head (beta right = -20.521), GC-ML-DG-body (beta right = -16.293, beta left = -12.799), molecular_layer_HP-head (beta right = -44.202, beta left = -26.071) and molecular_layer_HP-body, (beta right = -31.368), hippocampal_tail (beta left = -80.073). Prediabetes related with lower bilateral parasubiculum volume, and T2DM related with lower left parasubiculum, presubiculum-head and fimbria. T2DM with chronic poor glycemic control had lower volume in multiple hippocampal subregions.