Abnormality In Hippocampal Connectivity In Type 2 Diabetes:Evidence From Resting State FMRI

Background and Objective:Type 2 diabetes mellitus(T2DM)is not only the risk factors of cardiovascular disease,but also can accelerate the cognition decrements and increase the risk of Alzheimer disease(AD).T2 DM has an extensive impact on the cognitive function,but so far,no studies have elucidated the neural mechanisms underlying the diabetes-related cognitive decline.In our study,granger causality analysis was firstly used to analyze resting state fMRI data in patients with T2 DM to investigate effective connectivity between the bilateral hippocampus and other global regions,then further analyze the relation between T2 DM and cognition impariment from the perspective of functional MRI.Methods:40 patients with T2DM(including 18 female and 22 male,mean age 56.8 ± 10.1 years old)and 40 healthy controls(including 22 female and 18 male,mean age(54.1 ±8.7)were recruited in this study.Demographic data,fasting plasma glucose and HbAl c were obtained in all subjects.General cognition was assessed by MOCA test.T2WI?FLAIR?3DT1 and fMRI were collected from 3.0 T MR scanner in both T2 DM patients and healthy controls.Granger casual analysis was conducted with rs-fMRI data using SPM8 and rest software.Two sample t test of demogaphic and clinical data were conducted with SPSS 20.Two sample t test of Granger causal analysis(GCA)result were conducted with REST 1.8.Results:The results indicated that compared with healthy controls,the causal outflow to right hippocampus from the rest of the brain increased in left inferior temporal gyrus and left inferior frontal gyrus,and decreased in cerebellum and left lingual gyrus,while the casual inflow increased in left calcarine,right middle temporal gyrus and left postcentral gyrus.However,the casual inflow to left hippocampus increased in cerebellum,and decreased in left precuneus,left thalamus,bilateral postcentral gyrus,middle frontal gyrus and bilateral inferior parietal gyrus.Conclusion:The existed abnormal functional connectivity between default mode network(DMN)and other regions may contribute to the cognitive decrement.In contrast to standard cognitive tests,DMN may serve as a potential screening tool for cognitive decline and offer us an opportunity to observe the living brain in a non-invasive way.