Changes in the structure, perfusion, and function of the hippocampus in type 2 diabetes mellitus

An analysis of brain structural changes in type 2 diabetes using advanced MRI techniques

BACKGROUND

T2DM is associated with neurodegenerative changes that can be detected through advanced magnetic resonance imaging. Brain atrophy in T2DM is linked to cognitive decline, yet the extent and pattern of structural brain changes remain underexplored. This study aims to assess volumetric differences in brain structures between diabetic and non-diabetic individuals using voxel-based morphometry (VBM).

METHODS

A prospective observational study was conducted with 86 participants (43 T2DM case and 43 healthy controls) who underwent high-resolution 3D MRI scans using 3D SPGR and T1-weighted Fast Spin Echo sequences. Image preprocessing and volumetric analysis were performed using Statistical Parametric Mapping (SPM-12) and the Computational Anatomy Toolbox (CAT-12). Brain volumes were analyzed for 24 regions. Statistical analyses were conducted using independent t-tests and linear regression, with p < 0.05 considered significant.

RESULTS

T2DM subjects exhibited significant gray matter (GM) volume reductions compared to controls, particularly in the hippocampus and middle frontal gyrus, as detected in both 3DSPGR and T1 FSE sequences. However, regional differences emerged between imaging modalities: while T1 FSE imaging revealed significant bilateral hippocampal atrophy, 3DSPGR data showed no such difference. Notably, both sequences demonstrated significantly increased volumes in the anterior and posterior temporal lobes in T2DM participants, suggesting possible region-specific hypertrophy.

CONCLUSION

T2DM is associated with significant brain atrophy, particularly in brain regions associated with cognition. Based on these findings, MRI-based volumetric analysis has the potential to detect and monitor T2DM-related neurodegeneration early, emphasizing the need for routine neuroimaging in diabetic populations. Research on longitudinal assessments will be necessary in the future to gain a deeper understanding of the progression of brain atrophy in diabetics.

Sequence of episodic memory-related behavioral and brain-imaging abnormalities in type 2 diabetes

BACKGROUND

Episodic memory decline is a common complication of type 2 diabetes (T2D). To comprehensively explore the neural mechanisms underlying it, we aimed to explore the sequence that episodic memory-related behavioral and brain-imaging biomarkers appear abnormal in the progression of T2D.

METHODS

We enrolled 62 healthy controls and 110 patients with T2D. The California Verbal Learning Test, Montreal cognitive assessment, and Stroop color word test was used to assess the episodic memory, general cognitive function, and executive function. Principal component analysis was applied to extract behavioral biomarkers. Imaging biomarkers included structural and functional MRI features of the entorhinal cortex-hippocampus and hippocampus-anterior cingulate cortex pathways. We used a novel discriminative event-based model to determine the sequence that memory-related biomarkers appear abnormal and estimate the stage of memory decline.

RESULTS

T2D patients exhibited poorer memory, general cognitive function, and executive function compared to healthy controls after controlling age, sex, and education level. In the progression of T2D, functional interaction between brain regions showed abnormalities first, followed by memory tests, the cerebral spontaneous neural activity, and finally the gray matter volume. Besides, abnormalities appeared earlier in the entorhinal cortex than in the anterior cingulate cortex. Later stage of memory decline was distributed in older patients with T2D and was associated with higher systolic blood pressure, postprandial blood glucose, and low-density lipoprotein.

CONCLUSIONS

In T2D, behavioral and brain imaging biomarkers of episodic memory appear abnormal in a specific sequence, and the stage of memory decline was closely associated with old age and vascular risk factors.

CLINICAL TRIAL REGISTRATION

NCT02420470, ClinicalTrials.gov ( https://www.

CLINICALTRIALS

gov/ ).

The Role of Insulin Within the Socio-Psycho-Biological Framework in Type 2 Diabetes-A Perspective from Psychoneuroimmunology

The interplay between socio-psychological factors and biological systems is pivotal in defining human health and disease, particularly in chronic non-communicable diseases. Recent advancements in psychoneuroimmunology and mitochondrial psychobiology have emphasized the significance of psychological factors as critical determinants of disease onset, progression, recurrence, and severity. These insights align with evolutionary biology, psychology, and psychiatry, highlighting the inherent social nature of humans. This study proposes a theory that expands insulin's role beyond traditional metabolic functions, incorporating it into the Mitochondrial Information Processing System (MIPS) and exploring it from an evolutionary medicine perspective to explore its function in processing psychological and social factors into biological responses. This narrative review comprises data from preclinical animal studies, longitudinal cohort studies, cross-sectional studies, machine learning analyses, and randomized controlled trials, and investigates the role of insulin in health and disease. The result is a proposal for a theoretical framework of insulin as a social substance within the socio-psycho-biological framework, emphasizing its extensive roles in health and disease. Type 2 Diabetes Mellitus (T2DM) with musculoskeletal disorders and neurodegeneration exemplifies this narrative. We suggest further research towards a comprehensive treatment protocol meeting evolutionary expectations, where incorporating psychosocial interventions plays an essential role. By supporting the concept of 'insulin resilience' and suggesting the use of heart rate variability to assess insulin resilience, we aim to provide an integrative approach to managing insulin levels and monitoring the effectiveness of interventions. This integrative strategy addresses broader socio-psychological factors, ultimately improving health outcomes for individuals with T2DM and musculoskeletal complications and neurodegeneration while providing new insights into the interplay between socio-psychological factors and biological systems in chronic diseases.

Intranasal insulin effect on cognitive and/or memory impairment: a systematic review and meta-analysis

Background: Cognitive impairment, characterized by deficits in cognitive functions and loss of delayed and immediate recall, disproportionately affects individuals aged 65 years and older, particularly those with comorbid cardiovascular conditions such as hypertension and diabetes mellitus. Objective: This study aimed to investigate the potential association between intranasal insulin and cognitive and/or memory impairment, with a specific focus on delayed and immediate recall, considering the rising prevalence of cognitive disorders in the aging population. Methodology: Employing a rigorous systematic approach, we conducted a thorough search of MEDLINE, Scopus, the Cochrane database, and Web of Science from inception to November 23, 2022, identifying relevant randomized clinical trials. Our analyses encompassed three key aspects: (i) assessing the impact of intranasal insulin on cognitive impairment, (ii) evaluating its effect on delayed recall, and (iii) examining its influence on immediate recall. Results: Five studies meeting the inclusion criteria were included. The results underscored a statistically significant effect of intranasal insulin on delayed memory (effect size: 1.37; 95% CI: 0.65 to 2.09) and overall cognition (effect size: 0.58; 95% CI: 0.08 to 1.08). However, no statistically significant effect was observed for immediate memory (effect size: 0.48; 95% CI: -0.00 to 0.96). Conclusions: This study provides compelling evidence supporting the significance and efficacy of intranasal insulin in enhancing delayed recall and overall cognition. The observed effects hold promise for potential therapeutic interventions in addressing cognitive deficits associated with aging and comorbid conditions. The findings emphasize the need for further research to elucidate the underlying mechanisms and optimize the application of intranasal insulin in cognitive enhancement strategies.

Supplementary Information

The online version contains supplementary material available at 10.1007/s11571-024-10138-5.

Urine Albumin-to-Creatinine Ratio as an Indicator of Brain Activity Changes in Chronic Kidney Disease: A Resting-State fMRI Study

OBJECTIVE

Chronic kidney disease (CKD) is increasingly recognized as a risk factor for alterations in brain function. However, detecting early-stage symptoms and structural changes remains challenging, potentially leading to delayed treatment. In our study, we aimed to investigate spontaneous brain activity changes in CKD patients using resting-state functional magnetic resonance imaging (fMRI). Additionally, we explored the correlation between common biomarkers reflecting CKD severity and brain activity.

METHODS

We recruited a cohort of 22 non-dialysis-dependent CKD patients and 22 controls for resting-state fMRI scans. Amplitude of low-frequency fluctuations (ALFFs) and regional homogeneity (ReHo) were calculated to evaluate brain activity. Regression analysis was conducted to explore the correlations between biomarkers reflecting the severity of CKD and brain activity.

RESULTS

CKD patients exhibited reduced z-scored ALFF (zALFF) and mean ALFF (mALFF) in the bilateral putamen, right caudate nucleus, left anterior cingulate, and right precuneus. Changes in bilateral putamen were also found in smCohe-ReHo and szCohe-ReHo analyses. Urine albumin-to-creatinine ratio (UACR), urine protein-to-creatinine ratio (UPCR), and serum albumin levels were associated with attenuated putamen activity.

CONCLUSION

Non-dialysis-dependent CKD patients had changes in zALFF, mALFF, smCohe-ReHo, and szCohe-ReHo values in specific brain regions, especially bilateral putamen. UACR, UPCR, and serum albumin levels are associated with putamen activity attenuation in rs-fMRI.

Abnormal resting-state functional connectivity of hippocampal subregions in type 2 diabetes mellitus-associated cognitive decline

Objective

Type 2 diabetes mellitus (T2DM) over time predisposes to inflammatory responses and abnormalities in functional brain networks that damage learning, memory, or executive function. The hippocampus is a key region often reporting connectivity abnormalities in memory disorders. Here, we investigated peripheral inflammatory responses and resting-state functional connectivity (RSFC) changes characterized of hippocampal subregions in type 2 diabetes-associated cognitive decline (T2DACD).

Methods

The study included 16 patients with T2DM, 16 patients with T2DACD and 25 healthy controls (HCs). Subjects were assessed for cognitive performance, tested for the expression of inflammatory factors IL-6, IL-10 and TNF-α in peripheral serum, underwent resting-state functional magnetic resonance imaging scans, and analyzed for RSFC using the hippocampal subregions as seeds. We also calculated the correlation between cognitive performance and RSFC of hippocampal subregion, and analyzed the significantly altered RSFC values of T2DACD for Receiver Operating Characteristic (ROC) analysis.

Results

T2DACD patients showed a decline in their ability to complete cognitive assessment scales and experimental paradigms, and T2DM did not show abnormal cognitive performance. IL-6 expression was increased in peripheral serum in both T2DACD and T2DM. Compared with HCs, T2DACD showed abnormalities RSFC of the left anterior hippocampus with left precentral gyrus and left angular gyrus. T2DM showed abnormalities RSFC of the left middle hippocampus with right medial frontal gyrus, right anterior and middle hippocampus with left precuneus, left anterior hippocampus with right precuneus and right posterior middle temporal gyrus. Compared with T2DM, T2DACD showed abnormalities RSFC of the left posterior hippocampus and right middle hippocampus with left precuneus. In addition, RSFC in the left posterior hippocampus with left precuneus of T2DACD was positively correlated with Flanker conflict response time (r=0.766, P=0.001). In the ROC analysis, the significantly altered RSFC values of T2DACD achieved significant performance.

Conclusions

T2DACD showed a significant decrease in attentional inhibition and working memory, peripheral pro-inflammatory response increased, and abnormalities RSFC of the hippocampal subregions with default mode network and sensory-motor network. T2DM did not show a significant cognitive decline, but peripheral pro-inflammatory response increased and abnormalities RSFC of the hippocampus subregions occurred in the brain. In addition, the left precuneus may be a key brain region in the conversion of T2DM to T2DACD. The results of this study may provide a basis for the preliminary diagnosis of T2DACD.

Structural characteristics of amygdala subregions in type 2 diabetes mellitus

Type 2 diabetes mellitus (T2DM) patients often suffer from depressive symptoms, which seriously affect cooperation in treatment and nursing. The amygdala plays a significant role in depression. This study aims to explore the microstructural alterations of the amygdala in T2DM and to investigate the relationship between the alterations and depressive symptoms. Fifty T2DM and 50 healthy controls were included. Firstly, the volumes of subcortical regions and subregions of amygdala were calculated by FreeSurfer. Covariance analysis (ANCOVA) was conducted between the two groups with covariates of age, sex, and estimated total intracranial volume to explore the differences in volume of subcortical regions and subregions of amygdala. Furthermore, the structural covariance within the amygdala subregions was performed. Moreover, we investigate the correlation between depressive symptoms and the volume of subcortical regions and amygdala subregions in T2DM. We observed a reduction in the volume of the bilateral cortico-amygdaloid transition area, left basal nucleus, bilateral accessory basal nucleus, left anterior amygdaloid area of amygdala, the left thalamus and left hippocampus in T2DM. T2DM patients showed decreased structural covariance connectivity between left paralaminar nucleus and the right central nucleus. Moreover, there was a negative correlation between self-rating depression scale scores and the volume of the bilateral cortico-amygdaloid transition area in T2DM. This study reveals extensive structural alterations in the amygdala subregions of T2DM patients. The reduction in the volume of the bilateral cortico-amygdaloid transition area may be a promising imaging marker for early recognition of depressive symptoms in T2DM.

Morphological and regional spontaneous functional aberrations in the brain associated with Crohn's disease: a systematic review and coordinate-based meta-analyses

Crohn's disease is an acknowledged "brain-gut" disorder with unclear physiopathology. This study aims to identify potential neuroimaging biomarkers of Crohn's disease. Gray matter volume, cortical thickness, amplitude of low-frequency fluctuations, and regional homogeneity were selected as indices of interest and subjected to analyses using both activation likelihood estimation and seed-based d mapping with permutation of subject images. In comparison to healthy controls, Crohn's disease patients in remission exhibited decreased gray matter volume in the medial frontal gyrus and concurrently increased regional homogeneity. Furthermore, gray matter volume reduction in the medial superior frontal gyrus and anterior cingulate/paracingulate gyri, decreased regional homogeneity in the median cingulate/paracingulate gyri, superior frontal gyrus, paracentral lobule, and insula were observed. The gray matter changes of medial frontal gyrus were confirmed through both methods: decreased gray matter volume of medial frontal gyrus and medial superior frontal gyrus were identified by activation likelihood estimation and seed-based d mapping with permutation of subject images, respectively. The meta-regression analyses showed a positive correlation between regional homogeneity alterations and patient age in the supplementary motor area and a negative correlation between gray matter volume changes and patients' anxiety scores in the medial superior frontal gyrus. These anomalies may be associated with clinical manifestations including abdominal pain, psychiatric disorders, and possibly reflective of compensatory mechanisms.

White matter microstructure alterations in type 2 diabetes mellitus and its correlation with cerebral small vessel disease and cognitive performance

Microstructural abnormalities of white matter fiber tracts are considered as one of the etiology of diabetes-induced neurological disorders. We explored the cerebral white matter microstructure alteration accurately, and to analyze its correlation between cerebral small vessel disease (CSVD) burden and cognitive performance in type 2 diabetes mellitus (T2DM). The clinical-laboratory data, cognitive scores [including mini-mental state examination (MMSE), Montreal cognitive assessment (MoCA), California verbal learning test (CVLT), and symbol digit modalities test (SDMT)], CSVD burden scores of the T2DM group (n = 34) and healthy control (HC) group (n = 21) were collected prospectively. Automatic fiber quantification (AFQ) was applied to generate bundle profiles along primary white matter fiber tracts. Diffusion tensor images (DTI) metrics and 100 nodes of white matter fiber tracts between groups were compared. Multiple regression analysis was used to analyze the relationship between DTI metrics and cognitive scores and CSVD burden scores. For fiber-wise and node-wise, DTI metrics in some commissural and association fibers were increased in T2DM. Some white matter fiber tracts DTI metrics were independent predictors of cognitive scores and CSVD burden scores. White matter fiber tracts damage in patients with T2DM may be characterized in specific location, especially commissural and association fibers. Aberrational specific white matter fiber tracts are associated with visuospatial function and CSVD burden.