Evaluating blood-brain barrier permeability in a rat model of type 2 diabetes

Vulnerability of the Hippocampus to Insults: Links to Blood-Brain Barrier Dysfunction

The hippocampus is a critical brain substrate for learning and memory; events that harm the hippocampus can seriously impair mental and behavioral functioning. Hippocampal pathophysiologies have been identified as potential causes and effects of a remarkably diverse array of medical diseases, psychological disorders, and environmental sources of damage. It may be that the hippocampus is more vulnerable than other brain areas to insults that are related to these conditions. One purpose of this review is to assess the vulnerability of the hippocampus to the most prevalent types of insults in multiple biomedical domains (i.e., neuroactive pathogens, neurotoxins, neurological conditions, trauma, aging, neurodegenerative disease, acquired brain injury, mental health conditions, endocrine disorders, developmental disabilities, nutrition) and to evaluate whether these insults affect the hippocampus first and more prominently compared to other brain loci. A second purpose is to consider the role of hippocampal blood-brain barrier (BBB) breakdown in either causing or worsening the harmful effects of each insult. Recent research suggests that the hippocampal BBB is more fragile compared to other brain areas and may also be more prone to the disruption of the transport mechanisms that act to maintain the internal milieu. Moreover, a compromised BBB could be a factor that is common to many different types of insults. Our analysis indicates that the hippocampus is more vulnerable to insults compared to other parts of the brain, and that developing interventions that protect the hippocampal BBB may help to prevent or ameliorate the harmful effects of many insults on memory and cognition.

Region-specific transcriptomic responses to obesity and diabetes in macaque hypothalamus

The hypothalamus plays a crucial role in the progression of obesity and diabetes; however, its structural complexity and cellular heterogeneity impede targeted treatments. Here, we profiled the single-cell and spatial transcriptome of the hypothalamus in obese and sporadic type 2 diabetic macaques, revealing primate-specific distributions of clusters and genes as well as spatial region, cell-type-, and gene-feature-specific changes. The infundibular (INF) and paraventricular nuclei (PVN) are most susceptible to metabolic disruption, with the PVN being more sensitive to diabetes. In the INF, obesity results in reduced synaptic plasticity and energy sensing capability, whereas diabetes involves molecular reprogramming associated with impaired tanycytic barriers, activated microglia, and neuronal inflammatory response. In the PVN, cellular metabolism and neural activity are suppressed in diabetic macaques. Spatial transcriptomic data reveal microglia's preference for the parenchyma over the third ventricle in diabetes. Our findings provide a comprehensive view of molecular changes associated with obesity and diabetes.

Causal relationship between psoriasis vulgaris and dementia: Insights from Mendelian randomization analysis

Many clinical studies have demonstrated a correlation between psoriasis vulgaris and dementia, yet this correlation remains controversial. Our study employed the Mendelian randomization (MR) method to investigate the causal relationship between psoriasis vulgaris and dementia. Data were obtained from the summary statistics of the genome-wide association studies from IEU-OpenGWAS project database. In univariate Mendelian randomization (UVMR) analysis, psoriasis vulgaris was used as exposure. Alzheimer disease (AD), vascular dementia (VaD), dementia with Lewy bodies (DLB), Parkinson's disease with dementia (PDD) and frontotemporal dementia (FTD) served as the outcomes. In multivariate Mendelian randomization (MVMR) analysis, VaD served as the outcome. The first MVMR analysis used psoriasis vulgaris, mean platelet volume (MPV), platelet distribution width (PDW) and platelet count (PLT) as exposures. The second MVMR analysis used psoriasis vulgaris, vitamin D level and 25 hydroxyvitamin D level as exposures. The main analysis employed the inverse variance weighted method, and the outcomes were evaluated by odds ratio (OR) and 95% confidence interval (95% CI). In UVMR analysis, the results depicted that psoriasis vulgaris was associated with VaD (OR: 0.903, 95% CI: 0.818-0.996, p = 0.041). The results revealed insignificant associations between psoriasis vulgaris and other dementia types. After adjusting the effects of MPV, PDW and PLT in MVMR analysis, the association between psoriasis vulgaris and VaD was no longer significant (p = 0.164). Similarly, after adjusting the effects of vitamin D level and 25 hydroxyvitamin D level in MVMR analysis, the association between psoriasis vulgaris and VaD was also no longer significant (p = 0.533). Our study suggests that psoriasis vulgaris may potentially decrease VaD incidence. However, the causal association between psoriasis vulgaris and VaD may be impeded by platelet-related indices, vitamin D level and 25 hydroxyvitamin D level.

Protective effects of GuanXinNing tablet (GXNT) on diabetic encephalopathy in zucker diabetic obesity (ZDF) rats

BACKGROUND

Diabetic encephalopathy (DE) is a complication of diabetes that leads to cognitive and behavioral decline. Utilizing safe and effective complementary and alternative medications for its management is a wise choice. Previous studies have shown that GuanXinNing Tablet (GXNT), an oral preparation primarily derived from two Chinese herbs, Salvia miltiorrhiza Bge. and Ligusticum chuanxiong Hort., exerts a beneficial neuroprotective effect. In this study, we explored the protective effects of GXNT on DE in male Zucker diabetic fatty (ZDF) rats induced by a high-fat diet, aiming to ascertain its significance and potential mechanisms.

METHODS

ZDF rats were induced to develop type 2 diabetes (T2DM) with DE by a high-fat diet and treated with GXNT for 8 weeks until they were 20 weeks old. Throughout the experiment, the animals' vital parameters, such as body weight, were continuously monitored. Cognitive function was evaluated using the Y maze test. Biochemical kits were employed to analyze blood glucose, lipids, and vascular endothelial-related factors. Cerebrovascular lesions were assessed using magnetic resonance angiography (MRA) imaging. Brain lesions were evaluated using hematoxylin and eosin (H&E) staining and ultrastructure observation. IgG and albumin (ALB) leakage were detected using immunofluorescence.

RESULTS

GXNT demonstrated an enhancement in the overall well-being of the animals. It notably improved cognitive and behavioral abilities, as demonstrated by extended retention time in the novel heterogeneous arm during the Y-maze test. GXNT effectively regulated glucose and lipid metabolism, reducing fasting and postprandial blood glucose, glycated hemoglobin (HbA1c), and total cholesterol (TC) levels. Additionally, it exhibited a protective effect on the vascular endothelium by reducing the serum TXB2/PGI2 ratio while elevating NO and PGI2 levels. Moreover, GXNT ameliorated stenosis and occlusion in cerebral vessel branches, increased the number of microvessels and neurons around the hippocampus, and improved microvascular occlusion in the cerebral cortex, along with addressing perivascular cell abnormalities. Immunofluorescence staining showed a decrease in the fluorescence intensity of IgG and ALB in the cerebral cortex.

CONCLUSIONS

GXNT demonstrated a highly satisfactory protective effect on DE in ZDF rats. Its mechanism of action could be based on the regulation of glucolipid metabolism and its protective effect on the vascular endothelium.

The gut microbiota-astrocyte axis: Implications for type 2 diabetic cognitive dysfunction

BACKGROUND

Diabetic cognitive dysfunction (DCD) is one of the most insidious complications of type 2 diabetes mellitus, which can seriously affect the ability to self-monitoring of blood glucose and the quality of life in the elderly. Previous pathological studies of cognitive dysfunction have focused on neuronal dysfunction, characterized by extracellular beta-amyloid deposition and intracellular tau hyperphosphorylation. In recent years, astrocytes have been recognized as a potential therapeutic target for cognitive dysfunction and important participants in the central control of metabolism. The disorder of gut microbiota and their metabolites have been linked to a series of metabolic diseases such as diabetes mellitus. The imbalance of intestinal flora has the effect of promoting the occurrence and deterioration of several diabetes-related complications. Gut microbes and their metabolites can drive astrocyte activation.

AIMS

We reviewed the pathological progress of DCD related to the "gut microbiota-astrocyte" axis in terms of peripheral and central inflammation, intestinal and blood-brain barrier (BBB) dysfunction, systemic and brain energy metabolism disorders to deepen the pathological research progress of DCD and explore the potential therapeutic targets.

CONCLUSION

"Gut microbiota-astrocyte" axis, unique bidirectional crosstalk in the brain-gut axis, mediates the intermediate pathological process of neurocognitive dysfunction secondary to metabolic disorders in diabetes mellitus.

Voxel-based morphometry reveals the correlation between gray matter volume and serum P-tau-181 in type 2 diabetes mellitus patients with different HbA1c levels

Introduction

Emerging evidence suggested widespread decreased gray matter volume (GMV) and tau hyperphosphorylation were associated with type 2 diabetes mellitus (T2DM). Insulin resistance is one of the mechanisms of neuron degeneration in T2DM; it can decrease the activity of protein kinase B and increase the activity of glycogen synthesis kinase-3β, thus promoting the hyperphosphorylation of tau protein and finally leading to neuronal degeneration. However, the association between GMV and serum tau protein phosphorylated at threonine 181 (P-tau-181) in T2DM patients lacks neuroimaging evidence. We aimed to investigate the difference in brain GMV between T2DM patients with different glycated hemoglobin A1c (HbA1c) levels and healthy control (HC) subjects and the correlation between serum P-tau-181 and GMV in T2DM patients.

Methods

Clinical parameters, biochemical indicators, and MRI data were collected for 41 T2DM patients with high glycosylated hemoglobin level (HGL), 17 T2DM patients with normal glycosylated hemoglobin level (NGL), and 42 HC subjects. Voxel-based morphometry (VBM) method was applied to investigate GMV differences among groups, and multiple regression analysis was used to examine the correlation between serum P-tau-181 and GMV.

Results

Compared with HC subjects, the T2DM patients with HGL or NGL all showed significantly decreased GMV. Briefly, the GMV decreased in T2DM patients with HGL was mainly in the bilateral parahippocampal gyrus (PHG), right middle temporal gyrus (MTG), temporal pole (TPOmid), hippocampus (HIP), and left lingual gyrus. The GMV reduction in T2DM patients with NGL was in the right superior temporal gyrus (STG), and there was no significant difference in GMV between the two diabetic groups. The GMV values of bilateral PHG, right MTG, TPOmid, HIP, and STG can significantly (p < 0.0001) distinguish T2DM patients from HC subjects in ROC curve analysis. In addition, we found that serum P-tau-181 levels were positively correlated with GMV in the right superior and middle occipital gyrus and cuneus, and negatively correlated with GMV in the right inferior temporal gyrus in T2DM patients.

Conclusion

Our study shows that GMV atrophy can be used as a potential biological indicator of T2DM and also emphasizes the important role of P-tau-181 in diabetic brain injury, providing new insights into the neuropathological mechanism of diabetic encephalopathy.

Caffeine protects against hippocampal alterations in type 2 diabetic rats via modulation of gliosis, inflammation and apoptosis

Type 2 diabetes (T2D) is implicated in the injury of several organs, including the brain resulting in neuronal damage, which may lead to cognitive impairment and dementia. Additionally, it is linked to inflammation, cytokine release, apoptosis and various degenerative conditions. Astrocytes and microglia might have a role in mediating these processes. Caffeine, a psychoactive beverage, has been shown to reduce the risk of cognitive and memory impairment. This study proposes anti-inflammatory and anti-apoptotic role of caffeine, which can be mediated via microglia/astrocyte activation and overexpression of pro-inflammatory molecules. T2D was induced in rats by feeding with high fat high sugar diet and injecting a single low dose streptozotocin (STZ) intraperitoneally. Other diabetic rats were given caffeine orally (in two doses) for 5 weeks, starting 1 week before STZ injection. Measurement of plasma cytokines, TNFα and IL6, was performed using enzyme-linked immunosorbent assay (ELISA) technique. After sacrificing animals, brains were obtained and processed for histological evaluation. Immunohistochemistry was also performed using the following primary antibodies, anti-astrocyte marker GFAP, anti-microglia marker CD11b and apoptotic marker (anti-cleaved caspase-3). There was upregulation of IL6 and TNF-α in diabetic rats. Additionally, histological evaluation of the hippocampus of diabetic rats revealed cellular degeneration. There was increased immunostaining of GFAP, CD11b and cleaved caspase-3 in diabetic rats. Pretreatment with caffeine to diabetic rats, resulted in improvement of structural changes and decrease in cytokine levels and immuno-markers, expression, and this was in a dose-dependent manner. In conclusion, caffeine had an ameliorative role in enhancing hippocampal degenerative changes in T2D.

Cognitive decline and diabetes: a systematic review of the neuropathological correlates accounting for cognition at death

Given conflicting findings in epidemiologic studies, we determined the relative contributions of different neuropathologies to the excess risk of cognitive decline in diabetes mellitus (DM) through a systematic review of the literature. Included studies compared subjects with and without DM and reported neuropathological outcomes accounting for cognition at death. Data on Alzheimer's disease (AD) pathology, cerebrovascular disease and non-vascular, non-AD pathology were extracted from each study. Eleven studies (n=6 prospective cohorts, n=5 retrospective post-mortem series, total n=6330) met inclusion criteria. All 11 studies quantified AD changes and 10/11 measured cerebrovascular disease: macroscopic lesions (n=9), microinfarcts (n=8), cerebral amyloid angiopathy (CAA, n=7), lacunes (n=6), white matter disease (n=5), haemorrhages (n=4), microbleeds (n=1), hippocampal microvasculature (n=1). Other pathology was infrequently examined. No study reported increased AD pathology in DM, three studies showed a decrease (n=872) and four (n= 4018) showed no difference, after adjustment for cognition at death. No study reported reduced cerebrovascular pathology in DM. Three studies (n=2345) reported an increase in large infarcts, lacunes and microinfarcts. One study found lower cognitive scores in DM compared to non-DM subjects despite similar cerebrovascular and AD-pathology load suggesting contributions from other neuropathological processes. In conclusion, lack of an association between DM and AD-related neuropathology was consistent across studies, irrespective of methodology. In contrast to AD, DM was associated with increased large and small vessel disease. Data on other pathologies such as non-AD neurodegeneration, and blood-brain-barrier breakdown were lacking. Further studies evaluating relative contributions of different neuropathologies to the excess risk of DM are needed.

Glial and Vascular Cell Regulation of the Blood-Brain Barrier in Diabetes

As a structural barrier, the blood-brain barrier (BBB) is located at the interface between the brain parenchyma and blood, and modulates communication between the brain and blood microenvironment to maintain homeostasis. The BBB is composed of endothelial cells, basement membrane, pericytes, and astrocytic end feet. BBB impairment is a distinguishing and pathogenic factor in diabetic encephalopathy. Diabetes causes leakage of the BBB through downregulation of tight junction proteins, resulting in impaired functioning of endothelial cells, pericytes, astrocytes, microglia, nerve/glial antigen 2-glia, and oligodendrocytes. However, the temporal regulation, mechanisms of molecular and signaling pathways, and consequences of BBB impairment in diabetes are not well understood. Consequently, the efficacy of therapies diabetes targeting BBB leakage still lags behind the requirements. This review summarizes the recent research on the effects of diabetes on BBB composition and the potential roles of glial and vascular cells as therapeutic targets for BBB disruption in diabetic encephalopathy.

Blood-Brain Barrier Transporters: Opportunities for Therapeutic Development in Ischemic Stroke

Globally, stroke is a leading cause of death and long-term disability. Over the past decades, several efforts have attempted to discover new drugs or repurpose existing therapeutics to promote post-stroke neurological recovery. Preclinical stroke studies have reported successes in identifying novel neuroprotective agents; however, none of these compounds have advanced beyond a phase III clinical trial. One reason for these failures is the lack of consideration of blood-brain barrier (BBB) transport mechanisms that can enable these drugs to achieve efficacious concentrations in ischemic brain tissue. Despite the knowledge that drugs with neuroprotective properties (i.e., statins, memantine, metformin) are substrates for endogenous BBB transporters, preclinical stroke research has not extensively studied the role of transporters in central nervous system (CNS) drug delivery. Here, we review current knowledge on specific BBB uptake transporters (i.e., organic anion transporting polypeptides (OATPs in humans; Oatps in rodents); organic cation transporters (OCTs in humans; Octs in rodents) that can be targeted for improved neuroprotective drug delivery. Additionally, we provide state-of-the-art perspectives on how transporter pharmacology can be integrated into preclinical stroke research. Specifically, we discuss the utility of in vivo stroke models to transporter studies and considerations (i.e., species selection, co-morbid conditions) that will optimize the translational success of stroke pharmacotherapeutic experiments.

Imaging in experimental models of diabetes

Translational medicine, experimental medicine and experimental animal models, in particular mice and rats, represent a multidisciplinary field that has made it possible to achieve, in the last decades, important scientific progress. In this review, we have summarized the most frequently used imaging animal models, such as ultrasound (US), micro-CT, MRI and the optical imaging methods, and their main implications in diagnostic and therapeutic fields, with a particular focus on diabetes mellitus, a multifactorial disease extremely widespread among the general population.

Shared metabolic and neuroimmune mechanisms underlying Type 2 Diabetes Mellitus and Major Depressive Disorder

Type 2 Diabetes Mellitus (T2DM) is a chronic metabolic disease with symptoms that go beyond the domain of glucose metabolism. In fact, research has shown that T2DM is accompanied by neurodegeneration and neuroinflammation. Interestingly, Major Depressive Disorder (MDD), a mood disorder characterized mainly by depressed mood and anhedonia is a key feature of T2DM. A body of evidence demonstrates that there are many shared neuroimmune mechanisms underlying the pathophysiology of T2DM and MDD. Therefore, here we review the state-of-art regarding the underlying factors common to both T2DM and MDD. Furthermore, we briefly discuss how depressive symptoms in diabetic patients could be tackled by using novel therapeutic approaches uncovered by these shared mechanisms. Understanding the comorbidity of depression in diabetic patients is essential to fully address T2DM pathophysiology and treatment.

Quantitative Imaging of Blood-Brain Barrier Permeability Following Repetitive Mild Head Impacts

This was an exploratory study designed to evaluate the feasibility of a recently established imaging modality, quantitative ultrashort time-to-echo contrast enhanced (QUTE-CE), to follow the early pathology and vulnerability of the blood brain barrier in response to single and repetitive mild head impacts. A closed-head, momentum exchange model was used to produce three consecutive mild head impacts aimed at the forebrain separated by 24 h each. Animals were measured at baseline and within 1 h of impact. Anatomical images were collected to assess the extent of structural damage. QUTE-CE biomarkers for BBB permeability were calculated on 420,000 voxels in the brain and were registered to a bilateral 3D brain atlas providing site-specific information on 118 anatomical regions. Blood brain barrier permeability was confirmed by extravasation of labeled dextran. All head impacts occurred in the absence of any structural brain damage. A single mild head impact had measurable effects on blood brain barrier permeability and was more significant after the second and third impacts. Affected regions included the prefrontal ctx, basal ganglia, hippocampus, amygdala, and brainstem. Our findings support the concerns raised by the healthcare community regarding mild head injuries in participants in organized contact sports and military personnel in basic training and combat.

Neurovascular imaging with QUTE-CE MRI in APOE4 rats reveals early vascular abnormalities

Cerebrovascular abnormality is linked to Alzheimer's disease and related dementias (ADRDs). ApoE-Ɛ4 (APOE4) is known to play a critical role in neurovascular dysfunction, however current medical imaging technologies are limited in quantification. This cross-sectional study tested the feasibility of a recently established imaging modality, quantitative ultra-short time-to-echo contrast-enhanced magnetic resonance imaging (QUTE-CE MRI), to identify small vessel abnormality early in development of human APOE4 knock-in female rat (TGRA8960) animal model. At 8 months, 48.3% of the brain volume was found to have significant signal increase (75/173 anatomically segmented regions; q<0.05 for multiple comparisons). Notably, vascular abnormality was detected in the tri-synaptic circuit, cerebellum, and amygdala, all of which are known to functionally decline throughout AD pathology and have implications in learning and memory. The detected abnormality quantified with QUTE-CE MRI is likely a result of hyper-vascularization, but may also be partly, or wholly, due to contributions from blood-brain-barrier leakage. Further exploration with histological validation is warranted to verify the pathological cause. Regardless, these results indicate that QUTE-CE MRI can detect neurovascular dysfunction with high sensitivity with APOE4 and may be helpful to provide new insights into health and disease.

Advances in Exosomes Derived from Different Cell Sources and Cardiovascular Diseases

Exosomes can reach distant tissues through blood circulation to communicate directly with target cells and rapidly regulate intracellular signals. Exosomes play an important role in cardiovascular pathophysiology. Different exosomes derived from different sources, and their cargos have different mechanisms of action. In addition to being biomarkers, exosomes also have a certain significance in the diagnosis, treatment, and even prevention of cardiovascular diseases. Here, we provide a review of the up-to-date applications of exosomes, derived from various sources, in the prognosis and diagnosis of cardiovascular diseases.