| Part Ⅰ.Effects of glycemic variability on cognitive function and brain structure in type 2 diabetic patientsObjective To investigate the effects of glycemic variability on cognitive function and brain structure in patients with type 2 diabetes mellitus（T2DM）.Methods A total of 71 T2 DM patients treated in our hospital from November 2019 to December 2020 were involved,and 70 healthy controls（HC）were recruited during the same period.All participants completed magnetic resonance scans and cognitive function tests.Among them,36 of the T2 DM patients completed the collection of glycemic variability data through the continuous glucose monitoring.3.0 T MRI was used to obtain 3D-T1 images,and Voxel-Based Morphological Analysis（VBM）was used for data analysis.Gray matter volumes in both groups were compared based on the cluster level,and the value of gray matter volumes in different brain regions was extracted,and the partial correlation analysis was used to analyze the gray matter volume values and glycemic variability indicators and cognitive test scores,in which gender,age and education level was used as covariates.Results Compared with the control group,the volume of gray matter in the right cerebellum 4/5 area,caudate,thalamus,middle frontal gyrus and medial superior frontal gyrus were decreased and multiple cognitive test scores were decreased in the T2 DM group（P < 0.05）.Correlation between brain gray matter volume and cognitive test scores in group of T2DM: the gray matter volume of the left caudate was negatively correlated with Trail Making Test-A（TMT-A）（pr =-0.276,P = 0.023）.The gray matter volume of the left thalamus was positively correlated with Auditory Verbal Learning Test（delay）[AVLT（delay）]（pr = 0.251,P = 0.039）.The gray matter volume of the left medial superior frontal gyrus was positively correlated with Digit Span Test-forward（DST-forward）（pr = 0.258,P = 0.034）.Correlation between brain gray matter volume and glycemic variability index: Standard Deviation of Blood Glucose（SDBG）was negatively correlated with the left caudate and the left medial superior frontal gyrus（pr=-0.449,P = 0.009;pr =-0.376,P = 0.031）.Correlation between glycemic variability index and cognitive test scores: Mean Blood Glucose（MBG）was negatively correlated with Symbol Digital Modalities Test（SDMT）and Verbal Fluency Test（VFT）（pr =-0.357,P = 0.042;pr =-0.374,P = 0.032）.SDBG was negatively correlated with DST-forward（pr =-0.465,P = 0.006）.Coefficient of Variation（CV）was negatively correlated with DST-forward（pr =-0.383,P = 0.028）.Absolute Mean of Daily Difference（MODD）was negatively correlated with SDMT（pr =-0.562,P = 0.002）.Time in Range（TIR）was positively correlated with DST-forward（pr = 0.406,P =0.032）.Conclusion Both cognitive function and gray matter volume in related brain regions were decreased in patients with T2 DM.We also found that the glycemic variability is positively associated with the gray atrophy and the cognitive decrease in T2 DM patients.Part Ⅱ.The change of olfactory identification in type 2 diabetic patients and its correlation with cognitive function and brain structureObjective To investigate the change of olfactory identification（OI）in T2 DM patients and its relationship with cognitive function and brain structure.Methods Sixty eight T2 DM patients and 68 healthy controls were recruited at the same period.The Chinese Smell Identification Test（CSIT）was used to test the olfactory identification ability of all subjects.All participants were successfully completed 3.0 T MRI scans and multiple cognitive function tests.3D-T1 images were acquired.And surface-based morphometry analysis（SBM）was used for data analysis.The cortical thickness of the olfactory-related brain regions in both groups was compared,and then the cortical thickness values ??of the olfactory-related brain regions were extracted,and the Pearson correlation analysis was performed with the olfactory identification scores and cognitive test scores.Results Compared with the HC group,T2 DM patients had lower CSIT-OI score（t =-2.360,P = 0.020）,AVLT（delay）（t =-2.274,P = 0.025）,Montreal Cognitive Assessment（Mo CA）（t =-3.336,P = 0.001）,SDMT（t =-3.406,P = 0.001）,DST-forward（t =-2.395,P = 0.018）,Digit Span Test-backward（DST-backward）（t =-2.201,P = 0.029）,VFT（t =-2.887,P = 0.005）.Correlation between CSIT-OI score and cortical thickness in olfactory-related brain regions in patients with T2DM: After FDR correction,CSIT-OI score was positively correlated with cortical thickness of the left parahippocampal gyrus,left insula and right insula（r = 0.340,P = 0.030;r = 0.303,P = 0.040;r = 0.328,P = 0.030）.Correlation between CSIT-OI score and cognitive test scores: After FDR correction,CSIT-OI score in T2 DM patients was positively correlated with Mini-Mental State Examination（MMSE）,Mo CA,SDMT,DST-forward,DST-backward and VFT（r = 0.257,P = 0.049;r = 0.478,P < 0.001;r = 0.323,P =0.018;r = 0.376,P = 0.007;r = 0.264,P = 0.049;r = 0.265,P = 0.049）,which was negatively correlated with TMT-A（r =-0.414,P < 0.001）.Correlation between cognitive test scores and cortical thickness in olfactory-related brain regions: After correction by FDR,the cortical thickness of the left parahippocampal gyrus in T2DM patients was positively correlated with Auditory Verbal Learning Test（immediate）[AVLT（immediate）],AVLT（delay）,Mo CA,SDMT,DST-backward and VFT（r =0.370,P = 0.010;r = 0.325,P = 0.018;r = 0.299,P = 0.026;r = 0.392,P = 0.010;r =0.322,P = 0.018;r = 0.268,P = 0.039）,which was negatively correlated with TMT-A（r =-0.285,P = 0.032）.The cortical thickness of the left insula was positively correlated with Mo CA and DST-backward（r = 0.391,P = 0.010;r = 0.366,P = 0.010）.There was no significant correlation between CSIT-OI score and the cortical thickness of the right insula（P > 0.05）.Conclusions the olfactory identification function and multiple cognitive function in T2 DM patients were decreased.We also found that the olfactory recognition ability was positively correlated with the cortical atrophy in some brain regions and the cognitive function decrease in T2 DM patients. |
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