Sex differences in the effects of high fat diet on underlying neuropathology in a mouse model of VCID

BACKGROUND

Damage to the cerebral vasculature can lead to vascular contributions to cognitive impairment and dementia (VCID). A reduction in blood flow to the brain leads to neuropathology, including neuroinflammation and white matter lesions that are a hallmark of VCID. Mid-life metabolic disease (obesity, prediabetes, or diabetes) is a risk factor for VCID which may be sex-dependent (female bias).

METHODS

We compared the effects of mid-life metabolic disease between males and females in a chronic cerebral hypoperfusion mouse model of VCID. C57BL/6J mice were fed a control or high fat (HF) diet starting at ~ 8.5 months of age. Three months after diet initiation, sham or unilateral carotid artery occlusion surgery (VCID model) was performed. Three months later, mice underwent behavior testing and brains were collected to assess pathology.

RESULTS

We have previously shown that in this VCID model, HF diet causes greater metabolic impairment and a wider array of cognitive deficits in females compared to males. Here, we report on sex differences in the underlying neuropathology, specifically white matter changes and neuroinflammation in several areas of the brain. White matter was negatively impacted by VCID in males and HF diet in females, with greater metabolic impairment correlating with less myelin markers in females only. High fat diet led to an increase in microglia activation in males but not in females. Further, HF diet led to a decrease in proinflammatory cytokines and pro-resolving mediator mRNA expression in females but not males.

CONCLUSIONS

The current study adds to our understanding of sex differences in underlying neuropathology of VCID in the presence of a common risk factor (obesity/prediabetes). This information is crucial for the development of effective, sex-specific therapeutic interventions for VCID.

Determination of the role of hippocampal astrocytes in the bilateral common carotid artery stenosis mouse model by RNA sequencing

INTRODUCTION

Bilateral common carotid artery stenosis (BCAS) is used experimentally to model vascular dementia (VaD). Previous studies have primarily focused on the degradation of brain white matter after BCAS. However, hippocampal abnormalities are equally important, and hippocampal astrocytes are specifically involved in neural circuits that regulate learning and memory. Whether hippocampal astrocytes participate in the pathogenesis of BCAS-induced VaD has not been well studied. Therefore, in the present study, we attempted to explore the role of hippocampal astrocytes in BCAS.

METHODS

Two months after BCAS, behavioral experiments were conducted to investigate changes in neurological function in sham and BCAS mice. A ribosome-tagging approach (RiboTag) profiling strategy was used to isolate mRNAs enriched in hippocampal astrocytes, and the RNA was sequenced and analyzed using transcriptomic methods. Quantitative reverse transcription polymerase chain reaction (qRT-PCR) was utilized to validate the results of RNA sequencing. Immunofluorescence analyses were conducted to evaluate the number and morphology of hippocampal astrocytes.

RESULTS

We observed significant short-term working memory impairment in BCAS mice. Moreover, the RNA obtained through RiboTag technology was specific to astrocytes. Transcriptomics approaches and subsequent validation studies revealed that the genes that showed expression changes in hippocampal astrocytes after BCAS were mainly involved in immune system processes, glial cell proliferation, substance transport and metabolism. Furthermore, the number and distribution of astrocytes in the CA1 region of the hippocampus tended to decrease after modeling.

CONCLUSION

In this study, comparisons between sham and BCAS mice showed that the functions of hippocampal astrocytes were impaired in BCAS-induced chronic cerebral hypoperfusion-related VaD.

The Ties That Bind: Glial Transplantation in White Matter Ischemia and Vascular Dementia

White matter injury is a progressive vascular disease that leads to neurological deficits and vascular dementia. It comprises up to 30% of all diagnosed strokes, though up to ten times as many events go undiagnosed in early stages. There are several pathologies that can lead to white matter injury. While some studies suggest that white matter injury starts as small infarcts in deep penetrating blood vessels in the brain, others point to the breakdown of endothelial function or the blood-brain barrier as the primary cause of the disease. Whether due to local endothelial or BBB dysfunction, or to local small infarcts (or a combination), white matter injury progresses, accumulates, and expands from preexisting lesions into adjacent white matter to produce motor and cognitive deficits that present as vascular dementia in the elderly. Vascular dementia is the second leading cause of dementia, and white matter injury-attributed vascular dementia represents 40% of all diagnosed dementias and aggravates Alzheimer's pathology. Despite the advances in the last 15 years, there are few animal models of progressive subcortical white matter injury or vascular dementia. This review will discuss recent progress in animal modeling of white matter injury and the emerging principles to enhance glial function as a means of promoting repair and recovery.

Neurovascular Correlates of Cobalamin, Folate, and Homocysteine in Dementia

BACKGROUND

Cobalamin (Cbl) and folate are common supplements clinicians prescribe as an adjuvant therapy for dementia patients, on the presumption of their neurotrophic and/or homocysteine (Hcy) lowering effect. However, the treatment efficacy has been found mixed and the effects of Cbl/folate/Hcy on the human brain remain to be elucidated.

OBJECTIVE

To explore the neurovascular correlates of Cbl/folate/Hcy in Alzheimer's disease (AD) and subcortical ischemic vascular dementia (SIVD).

METHODS

Sixty-seven AD patients and 57 SIVD patients were prospectively and consecutively recruited from an outpatient clinic. Multimodal 3-Tesla magnetic resonance imaging was performed to quantitatively evaluate cerebral blood flow (CBF) and white matter integrity. The relationship between neuroimaging metrics and the serum levels of Cbl/folate/Hcy was examined by using the Kruskal-Wallis test, partial correlation analysis, and moderation analysis, at a significance level of 0.05.

RESULTS

As a whole, CBF mainly associated with Cbl/folate while white matter hyperintensities exclusively associated with Hcy. As compared with AD, SIVD exhibited more noticeable CBF correlates (spatially widespread with Cbl and focal with folate). In SIVD, a bilateral Cbl-moderated CBF coupling was found between medial prefrontal cortex and ipsilateral basal ganglia, while in the fronto-subcortical white matter tracts, elevated Hcy was associated with imaging metrics indicative of increased injury in both axon and myelin sheath.

CONCLUSIONS

We identified the neurovascular correlates of previously reported neurotrophic effect of Cbl/folate and neurotoxic effect of Hcy in dementia. The correlates exhibited distinct patterns in AD and SIVD. The findings may help improving the formulation of supplemental Cbl/folate treatment for dementia.

Açai Berry Mitigates Vascular Dementia-Induced Neuropathological Alterations Modulating Nrf-2/Beclin1 Pathways

The second-most common cause of dementia is vascular dementia (VaD). The majority of VaD patients experience cognitive impairment, which is brought on by oxidative stress and changes in autophagic function, which ultimately result in neuronal impairment and death. In this study, we examine a novel method for reversing VaD-induced changes brought on by açai berry supplementation in a VaD mouse model. The purpose of this study was to examine the impact of açai berries on the molecular mechanisms underlying VaD in a mouse model of the disease that was created by repeated ischemia-reperfusion (IR) of the whole bilateral carotid artery. Here, we found that açai berry was able to reduce VaD-induced behavioral alteration, as well as hippocampal death, in CA1 and CA3 regions. These effects are probably due to the modulation of nuclear factor erythroid 2-related factor 2 (Nrf-2) and Beclin-1, suggesting a possible crosstalk between these molecular pathways. In conclusion, the protective effects of açai berry could be a good supplementation in the future for the management of vascular dementia.

Detecting the vulnerable carotid plaque: the Carotid Artery Multimodality imaging Prognostic study design

BACKGROUND

Carotid artery disease is highly prevalent and a main cause of ischemic stroke and vascular dementia. There is a paucity of information on predictors of serious vascular events. Besides percentage diameter stenosis, international guidelines also recommend the evaluation of qualitative characteristics of carotid artery disease as a guide to treatment, but with no agreement on which qualitative features to assess. This inadequate knowledge leads to a poor ability to identify patients at risk, dispersion of medical resources, and unproven use of expensive and resource-consuming techniques, such as magnetic resonance imaging, positron emission tomography, and computed tomography.

OBJECTIVES

The Carotid Artery Multimodality imaging Prognostic (CAMP) study will: prospectively determine the best predictors of silent and overt ischemic stroke and vascular dementia in patients with asymptomatic subcritical carotid artery disease by identifying the noninvasive diagnostic features of the 'vulnerable carotid plaque'; assess whether 'smart' use of low-cost diagnostic methods such as ultrasound-based evaluations may yield at least the same level of prospective information as more expensive techniques.

STUDY DESIGN

We will compare the prognostic/predictive value of all proposed techniques with regard to silent or clinically manifest ischemic stroke and vascular dementia. The study will include ≥300 patients with asymptomatic, unilateral, intermediate degree (40-60% diameter) common or internal carotid artery stenosis detected at carotid ultrasound, with a 2-year follow-up. The study design has been registered on Clinicaltrial.gov on December 17, 2020 (ID number NCT04679727).

Neuroinflammation in Vascular Cognitive Impairment and Dementia: Current Evidence, Advances, and Prospects

Vascular cognitive impairment and dementia (VCID) is a major heterogeneous brain disease caused by multiple factors, and it is the second most common type of dementia in the world. It is caused by long-term chronic low perfusion in the whole brain or local brain area, and it eventually develops into severe cognitive dysfunction syndrome. Because of the disease’s ambiguous classification and diagnostic criteria, there is no clear treatment strategy for VCID, and the association between cerebrovascular pathology and cognitive impairment is controversial. Neuroinflammation is an immunological cascade reaction mediated by glial cells in the central nervous system where innate immunity resides. Inflammatory reactions could be triggered by various damaging events, including hypoxia, ischemia, and infection. Long-term chronic hypoperfusion-induced ischemia and hypoxia can overactivate neuroinflammation, causing apoptosis, blood–brain barrier damage and other pathological changes, triggering or aggravating the occurrence and development of VCID. In this review, we will explore the mechanisms of neuroinflammation induced by ischemia and hypoxia caused by chronic hypoperfusion and emphasize the important role of neuroinflammation in the development of VCID from the perspective of immune cells, immune mediators and immune signaling pathways, so as to provide valuable ideas for the prevention and treatment of the disease.

Single-nucleus transcriptome analysis reveals disease- and regeneration-associated endothelial cells in white matter vascular dementia

BACKGROUND

Vascular dementia (VaD) is the accumulation of vascular lesions in the subcortical white matter of the brain. These lesions progress and there is no direct medical therapy.

AIMS

To determine the specific cellular responses in VaD so as to provide molecular targets for therapeutic development.

MATERIALS AND METHODS

Single-nucleus transcriptome analysis was performed in human periventricular white matter (PVWM) samples of VaD and normal control (NC) subjects.

RESULTS

Differential analysis shows that cell type-specific transcriptomic changes in VaD are associated with the disruption of specific biological processes, including angiogenesis, immune activation, axonal injury and myelination. Each cell type in the neurovascular unit within white matter has a specific alteration in gene expression in VaD. In a central cell type for this disease, subcluster analysis of endothelial cells (EC) indicates that VaD contains a disease-associated EC subcluster that expresses genes associated with programmed cell death and a response to protein folding. Two other subpopulations of EC in VaD express molecular systems associated with regenerative processes in angiogenesis, and in axonal sprouting and oligodendrocyte progenitor cell maturation.

CONCLUSION

This comprehensive molecular profiling of brain samples from patients with VaD reveals previously unknown molecular changes in cells of the neurovascular niche, and an attempt at regeneration in injured white matter.

Shared and oppositely regulated transcriptomic signatures in Huntington's disease and brain ischemia confirm known and unveil novel potential neuroprotective genes

Huntington's disease and subcortical vascular dementia display similar dementing features, shaped by different degrees of striatal atrophy, deep white matter degeneration and tau pathology. To investigate the hypothesis that Huntington's disease transcriptomic hallmarks may provide a window into potential protective genes upregulated during brain acute and subacute ischemia, we compared RNA sequencing signatures in the most affected brain areas of 2 widely used experimental mouse models: Huntington's disease, (R6/2, striatum and cortex and Q175, hippocampus) and brain ischemia-subcortical vascular dementia (BCCAS, striatum, cortex and hippocampus). We identified a cluster of 55 shared genes significantly differentially regulated in both models and we screened these in 2 different mouse models of Alzheimer's disease, and 96 early-onset familial and apparently sporadic small vessel ischemic disease patients. Our data support the prevalent role of transcriptional regulation upon genetic coding variability of known neuroprotective genes (Egr2, Fos, Ptgs2, Itga5, Cdkn1a, Gsn, Npas4, Btg2, Cebpb) and provide a list of potential additional ones likely implicated in different dementing disorders and worth further investigation.

Copper as a Collaborative Partner of Zinc-Induced Neurotoxicity in the Pathogenesis of Vascular Dementia

Copper is an essential trace element and possesses critical roles in various brain functions. A considerable amount of copper accumulates in the synapse and is secreted in neuronal firings in a manner similar to zinc. Synaptic copper and zinc modulate neuronal transmission and contribute to information processing. It has been established that excess zinc secreted during transient global ischemia plays central roles in ischemia-induced neuronal death and the pathogenesis of vascular dementia. We found that a low concentration of copper exacerbates zinc-induced neurotoxicity, and we have demonstrated the involvement of the endoplasmic reticulum (ER) stress pathway, the stress-activated protein kinases/c-Jun amino-terminal kinases (SAPK/JNK) signaling pathway, and copper-induced reactive oxygen species (ROS) production. On the basis of our results and other studies, we discuss the collaborative roles of copper in zinc-induced neurotoxicity in the synapse and the contribution of copper to the pathogenesis of vascular dementia.

Possible Neuroprotective Effects of l-Carnitine on White-Matter Microstructural Damage and Cognitive Decline in Hemodialysis Patients

Although l-carnitine alleviated white-matter lesions in an experimental study, the treatment effects of l-carnitine on white-matter microstructural damage and cognitive decline in hemodialysis patients are unknown. Using novel diffusion magnetic resonance imaging (dMRI) techniques, white-matter microstructural changes together with cognitive decline in hemodialysis patients and the effects of l-carnitine on such disorders were investigated. Fourteen hemodialysis patients underwent dMRI and laboratory and neuropsychological tests, which were compared across seven patients each in two groups according to duration of l-carnitine treatment: (1) no or short-term l-carnitine treatment (NSTLC), and (2) long-term l-carnitine treatment (LTLC). Ten age- and sex-matched controls were enrolled. Compared to controls, microstructural disorders of white matter were widely detected on dMRI of patients. An autopsy study of one patient in the NSTLC group showed rarefaction of myelinated fibers in white matter. With LTLC, microstructural damage on dMRI was alleviated along with lower levels of high-sensitivity C-reactive protein and substantial increases in carnitine levels. The LTLC group showed better achievement on trail making test A, which was correlated with amelioration of disorders in some white-matter tracts. Novel dMRI tractography detected abnormalities of white-matter tracts after hemodialysis. Long-term treatment with l-carnitine might alleviate white-matter microstructural damage and cognitive impairment in hemodialysis patients.

Exploring the Oxidative Stress Mechanism of Buyang Huanwu Decoction in Intervention of Vascular Dementia Based on Systems Biology Strategy

OBJECTIVE

To explore the oxidative stress mechanism of modified Buyang Huanwu decoction (MBHD) in intervention of vascular dementia (VD) based on systems biology strategy.

METHODS

In this study, through the reverse virtual target prediction technology and transcriptomics integration strategy, the active ingredients and potential targets of MBHD treatment of VD were analyzed, and the drug-disease protein-protein interaction (PPI) network was constructed. Then, bioinformatics analysis methods are used for Gene Ontology (GO) enrichment analysis and pathway enrichment analysis, and finally find the core biological process. After that, in animal models, low-throughput technology is used to detect gene expression and protein expression of key molecular targets in oxidative stress-mediated inflammation and apoptosis signaling pathways to verify the mechanism of MBHD treatment of VD rats. Finally, the potential interaction relationship between MBHD and VD-related molecules is further explored through molecular docking technology.

RESULTS

There are a total of 54 MBHD components, 252 potential targets, and 360 VD genes. The results of GO enrichment analysis and pathway enrichment analysis showed that MBHD may regulate neuronal apoptosis, nitric oxide synthesis and metabolism, platelet activation, NF-κB signaling pathway-mediated inflammation, oxidative stress, angiogenesis, etc. Among them, SIRT1, NF-κB, BAX, BCL-2, CASP3, and APP may be important targets for MBHD to treat VD. Low-throughput technology (qRT-PCR/WB/immunohistochemical technology) detects oxidative stress-mediated inflammation and apoptosis-related signaling pathway molecules. The molecular docking results showed that 64474-51-7, cycloartenol, ferulic acid, formononetin, kaempferol, liquiritigenin, senkyunone, wallichilide, xanthinin, and other molecules can directly interact with NF-κB p65, BAX, BCL-2, and CASP3.

CONCLUSION

The active compounds of MBHD interact with multiple targets and multiple pathways in a synergistic manner, and have important therapeutic effects on VD mainly by balancing oxidative stress/anti-inflammatory and antiapoptotic, enhancing metabolism, and enhancing the immune system.

Cerebral Small Vessel Disease

Cerebral small vessel disease (CSVD) represents a cluster of various vascular disorders with different pathological backgrounds. The advanced vasculature net of cerebral vessels, including small arteries, capillaries, arterioles and venules, is usually affected. Processes of oxidation underlie the pathology of CSVD, promoting the degenerative status of the epithelial layer. There are several classifications of cerebral small vessel diseases; some of them include diseases such as Binswanger’s disease, leukoaraiosis, cerebral microbleeds (CMBs) and lacunar strokes. This paper presents the characteristics of CSVD and the impact of the current knowledge of this topic on the diagnosis and treatment of patients.

Susceptibility to capillary plugging can predict brain region specific vessel loss with aging

Vessel loss in the aging brain is commonly reported, yet important questions remain concerning whether there are regional vulnerabilities and what mechanisms could account for these regional differences, if they exist. Here we imaged and quantified vessel length, tortuosity and width in 15 brain regions in young adult and aged mice. Our data indicate that vessel loss was most pronounced in white matter followed by cortical, then subcortical grey matter regions, while some regions (visual cortex, amygdala, thalamus) showed no decline with aging. Regions supplied by the anterior cerebral artery were more vulnerable to loss than those supplied by middle or posterior cerebral arteries. Vessel width and tortuosity generally increased with age but neither reliably predicted regional vessel loss. Since capillaries are naturally prone to plugging and prolonged obstructions often lead to vessel pruning, we hypothesized that regional susceptibilities to plugging could help predict vessel loss. By mapping the distribution of microsphere-induced capillary obstructions, we discovered that regions with a higher density of persistent obstructions were more likely to show vessel loss with aging and vice versa. These findings indicate that age-related vessel loss is region specific and can be explained, at least partially, by regional susceptibilities to capillary plugging.

Astaxanthin protects cognitive function of vascular dementia

OBJECTIVE

The purpose of this study was to evaluate the effect of astaxanthin (AST) on cognition function, inflammatory response and oxidative stress in vascular dementia (VD) mice.

METHOD

VD mice model was established by left unilateral common carotid arteries occlusion (LUCCAO). Following LUCCAO, AST was intragastrically administered for 30 days. Object recognition test and morris water maze test were used to evaluate cognitive function. Hematoxylin and eosin staining was performed to observe the hippocampal neuron structure. Enzyme-linked immunosorbent assay kit and bicinchoninic acid kit were respectively adopted to measure IL-1β and IL-4 protein expression and superoxide dismutase (SOD) activity and malondialdehyde (MDA) content in hippocampus and prefrontal cortex.

RESULTS

AST improved the discrimination ability of VD mice. The escape latency and path length of VD mice treated with AST were dramatically reduced. Besides, AST 200 mg/kg enhanced crossing platform time and the number of times crossing the platform quadrant, and alleviated the morphological impairment in VD mice. Moreover, we found that AST inhibited IL-1β expression and MDA content, whereas promoted IL-4 expression and SOD activity in a dose-dependent manner.

CONCLUSION

AST could improve cognitive impairment and hippocampal neurons in VD mice, which may be related to suppression of inflammatory response and oxidative stress.

Small Vessel Disease-Related Dementia: An Invalid Neurovascular Coupling?

The arteriosclerosis-dependent alteration of brain perfusion is one of the major determinants in small vessel disease, since small vessels have a pivotal role in the brain's autoregulation. Nevertheless, as far as we know, endothelium distress can potentiate the flow dysregulation and lead to subcortical vascular dementia that is related to small vessel disease (SVD), also being defined as subcortical vascular dementia (sVAD), as well as microglia activation, chronic hypoxia and hypoperfusion, vessel-tone dysregulation, altered astrocytes, and pericytes functioning blood-brain barrier disruption. The molecular basis of this pathology remains controversial. The apparent consequence (or a first event, too) is the macroscopic alteration of the neurovascular coupling. Here, we examined the possible mechanisms that lead a healthy aging process towards subcortical dementia. We remarked that SVD and white matter abnormalities related to age could be accelerated and potentiated by different vascular risk factors. Vascular function changes can be heavily influenced by genetic and epigenetic factors, which are, to the best of our knowledge, mostly unknown. Metabolic demands, active neurovascular coupling, correct glymphatic process, and adequate oxidative and inflammatory responses could be bulwarks in defense of the correct aging process; their impairments lead to a potentially catastrophic and non-reversible condition.

Bushenhuoxue improves cognitive function and activates brain-derived neurotrophic factor-mediated signaling in a rat model of vascular dementia

OBJECTIVE

To explore the protective mechanisms of the Traditional Chinese Medicine Bushenhuoxue (BSHX) in a rat model of vascular dementia (VD).

METHODS

A rat model of VD was developed using bilateral common carotid artery occlusion (BCCAO). Rats were administered BSHX (10.14 or 5.07 g/kg), nimodipine (11.06 mg/kg; positive control), or saline (control) by gavage daily for 30 d post-surgery. Learning and memory abilities were assessed using the Morris water maze. Morphological changes in the hippocampus were observed using light microscopy (hematoxylin and eosin staining) and transmission electron microscopy (TEM). The mRNA and protein expression levels of brain-derived neurotrophic factor (BDNF), tyrosine receptor kinase B (TrkB), phosphatidyl inositol 3-kinase (PI3K), serine/threonine kinase (AKT), and cAMP response element binding protein (CREB) were measured by real-time polymerase chain reaction (RT-PCR) and Western blot, respectively.

RESULTS

Compared with the sham group, rats with BCCAO exhibited impaired learning and memory abilities (Morris water maze) and showed abnormalities in neuronal morphology (light microscopy) and ultrastructure (TEM) in the hippocampus. They also had decreased mRNA and protein expressions of BDNF, TrkB, PI3K, AKT, and CREB in hippocampal tissue (all P < 0.05). In rats with BCCAO, administration of BSHX attenuated deficits in learning and memory, improved the morphology and ultrastructure of hippocampal neurons, and enhanced mRNA and protein expression levels of BDNF, TrkB, PI3K, AKT, and CREB (all P < 0.05).

CONCLUSION

BSHX may protect hippocampal neurons and improve learning and memory abilities, at least in part via the activation of BDNF/TrkB/PI3K/AKT/CREB signaling.

Paraoxonase 1 decline and lipid peroxidation rise reflect a degree of brain atrophy and vascular impairment in dementia

BACKGROUND

Paraoxonase 1 (PON1) is an enzyme with the capability to protect against lipid oxidation and atherosclerotic lesions formation. Impaired antioxidative capacity and enhanced lipid peroxidation (reflected by malondialdehyde rise) accompany dementias.

OBJECTIVES

The aim of this study was to discern the possible differences in the activity and phenotype distribution of PON1, and lipid peroxidation level in dementias of neurodegenerative and vascular pathology, to assess whether they reflect structural changes in the brain, and to evaluate their potential as dementia markers.

MATERIAL AND METHODS

Paraoxonase 1 arylesterase activity and polymorphisms (dual-substrate method), and malondialdehyde/thiobarbituric acid reactive substances (MDA/TBARS) levels were determined spectrophotometrically in 257 serum samples derived from 136 dementive patients (with Alzheimer's disease (AD; n = 63), vascular dementia (VaD; n = 40) and mixed-type dementia (MD; n = 33), as well as from 121 non-dementive individuals. The results were analyzed with reference to dementia type and severity (assessed with Mini Mental State Examination (MMSE) and Clinical Dementia Rating (CDR) scales), structural brain changes (estimated with magnetic resonance imaging (MRI) - Global Cortical Atrophy (GCA), Medial Temporal lobe Atrophy (MTA) and Fazekas scales)) and brain ischemia (Hachinski Ischemic Scale (HIS) index), and evaluated using receiver operating characteristic (ROC) analysis.

RESULTS

Malondialdehyde/thiobarbituric acid reactive substances were increased in dementia (more in VaD than AD). In patients with vascular involvement, MDA/TBARS elevation reflected a degree of global cortical atrophy. Paraoxonase 1 activity was decreased in patients with dementia, especially in patients with severe cognitive deficits. In VaD, a drop in PON1 reflected a degree of MTA and brain ischemia. MDA/TBARS displayed 75% accuracy as a general dementia marker, but, similarly to PON1, were a poor differential marker.

CONCLUSIONS

Both indices were more associated with vascular involvement and the severity of brain atrophy or ischemia rather than with degree of cognitive decline.

Wuzang Wenyang Huayu decoction regulates differentially expressed transcripts in the rats' hippocampus after cerebral hypoperfusion

The modified Wenyang Huayu decoction has been widely used to treat vascular dementia in China for thousands of years. We have previously proved that a modified version, Wuzang Wenyang Huayu decoction has the potential to be a more effective clinical treatment that can attenuate cerebral ischaemic injury. However, the global transcript profile and signalling conduction pathways regulated by this recipe remains unclear. This study established a two-vessel occlusion rat model by bilateral common carotid artery occlusion. Two groups of rats were intragastrically treated Wuzang Wenyang Huayu 2.5 g/kg vs or Piracetam 0.15 g/kg for 2 weeks. Learning and memory abilities were measured with Morris water maze. Neuronal plasticity was observed by HE staining. Differentially expressed transcripts of rat hippocampus were analysed by transcriptomics with Illumina HiSeq2500 platform. Results showed that Wuzang Wenyang Huayu decoction significantly alleviated learning, memory deficits, coordination dysfunction and prevented hippocampus cellular injury; Results further revealed the increased gene expression in KEGG metabolic pathways (MT-ND2. MT-ND3, MT-ND4, MT-ND4L, MT-ND5 and MT-ATP8) and genes involved in signal transduction, carcinogenesis, immune system, endocrine system, nervous system etc (Results further revealed differential expression of genes involved in various systems, including MT-ND2) Our discovery is likely to provide new insights to molecular mechanisms of Wuzang Wenyang Huayu regarding hippocampal transcripts in a murine vascular dementia model.

Animal Models of Chronic Cerebral Hypoperfusion: From Mouse to Primate

Vascular cognitive impairment (VCI) or vascular dementia occurs as a result of brain ischemia and represents the second most common type of dementia after Alzheimer’s disease. To explore the underlying mechanisms of VCI, several animal models of chronic cerebral hypoperfusion have been developed in rats, mice, and primates. We established a mouse model of chronic cerebral hypoperfusion by narrowing the bilateral common carotid arteries with microcoils, eventually resulting in hippocampal atrophy. In addition, a mouse model of white matter infarct-related damage with cognitive and motor dysfunction has also been established by asymmetric common carotid artery surgery. Although most experiments studying chronic cerebral hypoperfusion have been performed in rodents because of the ease of handling and greater ethical acceptability, non-human primates appear to represent the best model for the study of VCI, due to their similarities in much larger white matter volume and amyloid β depositions like humans. Therefore, we also recently developed a baboon model of VCI through three-vessel occlusion (both the internal carotid arteries and the left vertebral artery). In this review, several animal models of chronic cerebral hypoperfusion, from mouse to primate, are extensively discussed to aid in better understanding of pathophysiology of VCI.

Patient-Specific iPSC Model of a Genetic Vascular Dementia Syndrome Reveals Failure of Mural Cells to Stabilize Capillary Structures

CADASIL (cerebral autosomal dominant arteriopathy with subcortical infarcts and leukoencephalopathy) is the most common form of genetic stroke and vascular dementia syndrome resulting from mutations in NOTCH3. To elucidate molecular mechanisms of the condition and identify drug targets, we established a patient-specific induced pluripotent stem cell (iPSC) model and demonstrated for the first time a failure of the patient iPSC-derived vascular mural cells (iPSC-MCs) in engaging and stabilizing endothelial capillary structures. The patient iPSC-MCs had reduced platelet-derived growth factor receptor β, decreased secretion of the angiogenic factor vascular endothelial growth factor (VEGF), were highly susceptible to apoptotic insults, and could induce apoptosis of adjacent endothelial cells. Supplementation of VEGF significantly rescued the capillary destabilization. Small interfering RNA knockdown of NOTCH3 in iPSC-MCs revealed a gain-of-function mechanism for the mutant NOTCH3. These disease mechanisms likely delay brain repair after stroke in CADASIL, contributing to the brain hypoperfusion and dementia in this condition, and will help to identify potential drug targets.

Possibilities of Dementia Prevention - It is Never Too Early to Start

Dementia represents one of the greatest global challenges for health and social care in this century. More than 50 million people worldwide suffer from dementia, and this number is predicted to triple by 2050. Ageing is often associated with cognitive impairment. Therefore, prevention of cognitive impairment is an imperative. Dementia includes a heterogeneous group of disorders, the most common being Alzheimer's disease and vascular dementia. Most cardiovascular risk factors such as hypertension, diabetes mellitus, hypercholesterolemia, atrial fibrillation and smoking are not exclusive risk factors for vascular dementia but also for Alzheimer's disease. The ApoE4 allele is the single non-modifiable risk factor for Alzheimer's disease. Today we know that an important, modifiable risk factor is education. Better education means better protection against dementia. A large number of dementia cases are potentially preventable by early intervention. Early changes in the blood vessel wall can be detected by early ultrasound methods or early biomarkers. These methods allow us to detect changes before the disease becomes clinically evident. Early disease detection enables timely management, and studies have shown that careful control of vascular risk factors can postpone the onset or even reverse disease progression.

Biomarkers identify the Binswanger type of vascular cognitive impairment

Binswanger's disease is a form of subcortical ischemic vascular disease (SIVD-BD) with extensive white matter changes. To test the hypothesis that biomarkers could improve classification of SIVD-BD, we recruited 62 vascular cognitive impairment and dementia (VCID) patients. Multimodal biomarkers were collected at entry into the study based on clinical and neuropsychological testing, multimodal magnetic resonance imaging (MRI), and cerebrospinal fluid (CSF) analysis. The patients' diagnoses were confirmed by long-term follow-up, and they formed a "training set" to test classification methods, including (1) subcortical ischemic vascular disease score (SIVDS), (2) exploratory factor analysis (EFA), (3) logistic regression (LR), and (4) random forest (RF). A subsequently recruited cohort of 43 VCID patients with provisional diagnoses were used as a "test" set to calculate the probability of SIVD-BD based on biomarkers obtained at entry. We found that N-acetylaspartate (NAA) on proton magnetic resonance spectroscopy (1H-MRS) was the best variable for classification, followed by matrix metalloproteinase-2 in CSF and blood-brain barrier permeability on MRI. Both LR and RF performed better in diagnosing SIVD-BD than either EFA or SIVDS. Two-year follow-up of provisional diagnosis patients confirmed the accuracy of statistically derived classifications. We propose that biomarker-based classification methods could diagnose SIVD-BD patients earlier, facilitating clinical trials.

Cerebral microvascular dysfunction and neurodegeneration in dementia

Maintaining normal learning and memory functions requires a high degree of coordination between neural and vascular cells. Basic and clinical studies have shown that brain microvasculature dysfunction activates inflammatory cells in the brain, leading to progressive neuronal loss and eventually dementia. This review focuses on recent studies aimed at identifying the molecular events that link cerebral microvascular dysfunction to neurodegeneration, including oxidative/nitrosative stress, cellular metabolic dysfunction, inflammatory signalling and abnormal synaptic plasticity. A better understanding of the coupling between vasculature and brain neurons and how this coupling is disrupted under pathological conditions is of great significance in identifying new diagnostic and treatment targets for dementia for which no new drugs have been approved since 2003.

[Effect of Ghrelin on Memory Impairment in a Rat Model of Vascular Dementia]

PURPOSE

The purpose of this study was to identify the effect of ghrelin on memory impairment in a rat model of vascular dementia induced by chronic cerebral hypoperfusion.

METHODS

Randomized controlled groups and the posttest design were used. We established the representative animal model of vascular dementia caused by bilateral common carotid artery occlusion and administered 80 μg/kg ghrelin intraperitoneally for 4 weeks. First, behavioral studies were performed to evaluate spatial memory. Second, we used molecular biology techniques to determine whether ghrelin ameliorates the damage to the structure and function of the white matter and hippocampus, which are crucial to learning and memory.

RESULTS

Ghrelin improved the spatial memory impairment in the Y-maze and Morris water maze test. In the white matter, demyelination and atrophy of the corpus callosum were significantly decreased in the ghrelin-treated group. In the hippocampus, ghrelin increased the length of hippocampal microvessels and reduced the microvessels pathology. Further, we confirmed angiogenesis enhancement through the fact that ghrelin treatment increased vascular endothelial growth factor (VEGF)-related protein levels, which are the most powerful mediators of angiogenesis in the hippocampus.

CONCLUSION

We found that ghrelin affected the damaged myelin sheaths and microvessels by increasing angiogenesis, which then led to neuroprotection and improved memory function. We suggest that further studies continue to accumulate evidence of the effect of ghrelin. Further, we believe that the development of therapeutic interventions that increase ghrelin may contribute to memory improvement in patients with vascular dementia.