Cerebral circulation - cognition and behavior最新文献

Introduction

Vascular cognitive impairment (VCI) is heterogeneous in brain atrophy patterns, clinical symptoms, and possibly in the factors affecting resilience to symptoms. The objective of this study was to investigate the heterogeneity of VCI by estimating different atrophy-driven subtypes and use those for identifying resilience factors in each subtype.

Methods

We used cross-sectional data from the Trace-VCI cohort comprising of memory-clinic patients with vascular brain injury on MRI (n=361 all-cause dementia, n=190 MCI, and n=188 SCD). White matter hyper-intensities (WMH) were segmented, and SLF toolbox was used to refill them on the MRIs for accurate parcellation. Freesurfer volumes were used for identifying subtypes with non-negative matrix factorization. Subtype-specific pseudo-timelines of progression were estimated using a previously validated discriminative event-based model. Severity of atrophy (SA) in patients was estimated using cross-validation based on their position on the pseudo-timeline. Using linear-regression, cognition and disability (MMSE, Global deterioration scale, disability assessment for dementia) were modelled to be dependent on SA and its interactions with genetic factors, vascular markers and risk-factors, and co-pathology independently (variables in Figure-3). Resilience factors were identified by testing if the model with the interaction explains the symptoms significantly more than the one without.

Results

The algorithm identified three atrophy-based VCI subtypes: Frontal, Subcortical/Temporal, and Parietal subtype. Their prevalence, vascular and clinical presentations are summarized in Figure-1. The pseudo-timelines of atrophy are shown in Figure-2. SA's interaction with education positively influenced cognition in all subtypes, but negatively influenced disability in subcortical/temporal subtype. In frontal and parietal subtypes, APOE ε4, AD co-pathology resulted in more SA without worsening symptoms. SA's interaction with smoking and microbleeds negatively influenced disability. In the subcortical/temporal subtype, SA's interaction with WMH, lacunes, infarcts negatively impacted disability. In parietal subtype, men have more cognitive resilience than women. SA's interaction with hypercholesterolemia, and smoking were significantly negative for cognition. Lacunes were associated with more SA without affecting cognition. Figure-3 summarizes the interactions for all subtypes.

Discussion

We identified three atrophy-based VCI subtypes where the risk-factors have different influence on atrophy and symptoms highlighting differences in resilience. These results could aid in prognosis and in personalizing patients’ intervention strategy.

Introduction

Cardiovascular and metabolic disorders rarely occur alone in old age but often cluster together in the so-called metabolic syndrome (MetS). While individual components of MetS, such as obesity, hypertension, and diabetes, have been linked to dementia and brain atrophy, their combined impact on cognitive and brain aging remains poorly explored. Our current study aims to investigate the relationship between MetS and markers of neurodegenerative and cerebrovascular pathologies while also considering potential differences between sexes.

Methods

We included 741 cognitively intact septuagenarians from the Gothenburg H70-Birth cohort 1944 with available brain MRI (286 had cerebrospinal fluid [CSF] sampling). MetS was defined by standard criteria (at least three among adiposity, raised blood pressure, blood glucose, reduced HDL-cholesterol, elevated triglycerides). MRI markers of brain pathology included overall (mean cortical thickness) and Alzheimer's disease (AD; average cortical thickness in signature areas) neurodegeneration, cerebral small vessel disease (SVD; markers such as white matter hyperintensity, lacunes, microbleeds, and perivascular spaces, and SVD score) and DTI's white- matter microstructural changes (fractional anisotropy). CSF biomarkers included t-tau, neurofilament light, neurogranin (overall neurodegeneration), Aβ42 and p-tau (AD), and CSF/serum albumin ratio (blood-brain barrier integrity). Analyses included regression models and stratification by sex.

Results

Overall, 410 participants (53%, n=196 women) had MetS. MetS was associated with increased odds of overall (OR=2.0, 95%CI 1.4–2.9) and AD-related (OR=1.8, 95%CI 1.4–2.6) neurodegeneration, high SVD burden (presence of ≥3 SVD compared to none: OR=2.1, 95%CI 1.1–4.3), and white-matter microstructural changes. Within the SVD markers, MetS was particularly related to white matter hyperintensities, lacunes, and perivascular spaces in basal ganglia. Furthermore, MetS was associated with alterations of blood-brain barrier integrity in the CSF subsample. Sex differences showed increased SVD burden in men with MetS, especially enlarged perivascular spaces (OR=2.9, 95%CI 1.7–5.0), while no differences were observed in women. No associations were detected with amyloid and tau.

Discussion

MetS in late life is linked to neurodegenerative and cerebrovascular pathologies, with SVD more prominent in men with MetS, but not in women.

Introduction

Visceral fat gain and the progressive onset of metabolic disorders in middle-aged mice induce alteration of the cerebral vascular tree in association with mild cognitive impairment. This precipitates stroke risk and might prompt the middle-aged population to cognitive decline. In this context, an endogenous peptide named apelin-13 and its receptor APJ are suspected to link metabolic disorders at middle age to the consequences of ischemic stroke on brain tissue, as well as vasomotor and cognitive functions. Apelin-13 induces neuroprotection after experimental ischemic stroke, but this action has not been examined under metabolic disturbances. The aim of our study is to evaluate the role of apelin-13 as a new therapeutic target in ischemic stroke under high-fat diet-induced metabolic disturbances at middle-age.

Methods

C57Bl/6 mice were fed for 6 months with normal diet (ND) or high-fat diet (HFD) before 30-minute middle cerebral artery occlusion (MCAO). Metabolic parameters, as well as circulating apelin-13 levels were evaluated every 3 months before MCAO. APJ brain expression and plasmatic apelin rate were assess at acute phase (24h post-stroke) and after behavioral (motor and cognitive) evaluation at chronic phase (10 days after MCAO).

Results

Mice under HFD developed overweight, hyperglycemia and hypercholesterolemia. Plasmatic apelin slowly decreased with age and was different between overweight and lean mice, but not between HFD and ND. The onset of MCAO under HFD induced 49% higher mortality than under ND. At acute phase, mice under HFD had a 25% decreased plasmatic apelin rate whereas mice under ND had a 2.5% of reduction. APJ brain expression in HFD mice was 59% reduced compared to ND. After 10 days, worsened behavioral impairment was observed in HFD mice compared to ND mice. Plasmatic apelin levels were reduced whatever the diet.

Discussion

These first results highlight the contribution of the apelinergic system to the influence of metabolic disturbances on stroke severity, that should be considered in therapeutic studies.

The number of people living with dementia, such as Alzheimer's disease, is increasing worldwide. Persons with dementia often have a high risk of atherosclerotic cardiovascular disease and they are therefore theoretically eligible for treatment of hypertension and hyperlipidemia. However, in this population, beneficial and harmful effects of cardiovascular risk management (CVRM) may be different compared to older persons without cognitive impairment. Current CVRM guidelines are based on trials from which persons with dementia were excluded. In this narrative review, we will discuss how current guidelines can be translated to persons with dementia and which aspects should be taken into account when treating hypertension and hyperlipidemia to prevent major adverse cardiovascular events (MACE). Survival time is significantly shorter in persons with dementia. We therefore suggest that since the main goal of CVRM is prevention of MACE, first of all, the patient's life expectancy and treatment wishes should be evaluated. Risk assessment tools are to be used with care, as they tend to overestimate the 5- and 10-year risk of MACE and benefit from CVRM in the prevention of MACE in persons with dementia. When the clinician and patient have decided that treatment is initiated or intensified, patients should be closely monitored since they are at high risk for adverse drugs events and overtreatment due to the natural course of blood pressure in persons with dementia. In the event of intolerance or side effects, medication should be switched or withdrawn. For persons with dementia and limited life expectancy, deprescribing should be part of usual care.

Introduction

The subcortical small vessel type of dementia (SSVD) is a common form of vascular dementia. There is a lack of disease-specific cerebrospinal fluid (CSF) biomarkers. We investigated whether CSF concentrations of neurofilament light chain (NFL), soluble amyloid precursor protein-α (sAPP-α), sAPP-β, and CSF/serum albumin ratio could separate SSVD from healthy controls, Alzheimer's disease (AD) and mixed dementia (combined AD and SSVD).

Methods

Patients with SSVD (n = 38), AD (n = 121), mixed dementia (n = 62), and healthy controls (n = 96) were included. The CSF biomarkers were measured using immunoassays, and their independent contribution to the separation between groups were evaluated using the Wald test. Then, the area under the receiver operating characteristics curve (AUROC) and 95% confidence intervals (CIs) were calculated.

Results

Elevated NFL concentrations and decreased sAPP-β concentrations independently separated SSVD from controls, and sAPP-β also distinguished SSVD from AD and mixed dementia. Furthermore, the combination of NFL and sAPP-β discriminated SSVD from controls with high accuracy (AUROC 0.903, 95% CI: 0.834 – 0.972). Additionally, sAPP-β combined with the core AD biomarkers (β-amyloid1-42, total tau, and phosphorylated tau181) had a high ability to separate SSVD from AD (AUROC 0.886, 95% CI: 0.830 – 0.942) and mixed dementia (AUROC 0.903, 95% CI: 0.838 – 0.968).

Discussion

The high accuracy of NFL and sAPP-β to separate SSVD from controls supports that SSVD is a specific diagnostic entity. Moreover, sAPP-β in combination with the core AD biomarkers distinguished SSVD from AD and mixed dementia.

A total number of 2498 individuals 70 years old were randomly elicited in Gothenburg, n=966 in 1971, n=1028 in 1976 and n=504 in 2000. Blood glucose levels in the 3 cohorts were 5.53 mmol/l for 1971 cohort, 5.30 mmol/l for 1976 and 5.83 mmol/l for 2000. Blood glucose levels declined when the cohorts were examined again with 75 years and 79 years. Looking at DM individuals, blood glucose levels at age 70 for the cohort 1971 was 8,90 mmol/l (n=54), for cohort 1976 of 8,91 mmol/l (n=64) and for cohort 1930 of 8,45 mmol/l (n=57). A strong correlation between Diabetes mellitus (DM) and body mass index (BMI) existed: BMI <25 had a frequency of DM in 6,0%, for BMI =25<30 had 6,4% DM, for BMI =30<35 had 10,6% and BMI >=35 had 23,1% DM. HbA1c mean was 40,68 (median 38,0) for all participants and 53,12 (median 51,0) in DM. The correlation of HbA1c with BMI did not reach statistical significance (p=0,09). In 2009 in DM individuals HbA1c was considerably higher in cerebrovascular dementia (62,3 mmol/l) than in DM with Alzheimer dementia (52,3 mmol/l) or in non-dementia (52,5 mmol/l) but numbers were too small for significance (rank test pooled 0,14; Satterthwaite 0,22). The proportion of DM was higher in the cerebrovascular group (8 of 18; 44%) than in the Alzheimer dementia (9 of 38; 27%) or in non-dementia (83 of 600; 13,8%). This prospective study showed an association between DM with cerebrovascular dementia, whereas the association with Alzheimer dementia was weaker.

Cerebrovascular disease is a major contributor to subcortical white matter pathology, vascular cognitive impairment (VCI) and dementia. Although the precise pathophysiological mechanisms remain unclear, it is increasingly evident that microglial responses may be critical to the development and progression of cerebrovascular disease and its cognitive consequences. To investigate this further, we assessed microglial reactivity in white matter regions of human post- mortem tissue with pathologically confirmed cerebrovascular injury. In parallel, we implemented a mouse model of VCI induced by bilateral carotid artery stenosis (BCAS) and determined the impact of genetically deleting the microglial immunoreceptor triggering receptor expressed on myeloid cells 2 (TREM2), a key regulator of microglial homeostatic and reactive functions. Using immunohistochemistry (IHC) and quantitative polymerase chain reaction (QPCR) we observed increased microglial reactivity and TREM2 expression in our human cohort implicating TREM2 signalling in microglial responses to cerebrovascular. In mice, IHC and flow cytometric analysis revealed Trem2 deficiency blunted microglial reactivity following BCAS (1 month). Transcriptomic analysis of Trem2-/- microglia also demonstrated attenuated induction of gene expression modules associated with inflammation, lysosomal function, lipid processing and metabolic reprogramming following BCAS (data not shown). Importantly, this was associated with greater white matter injury compared to wildtype (WT) counterparts in the absence of overt cognitive changes. Following longer durations of BCAS (6 months), Trem2-/- mice exhibited additional parenchymal and vascular pathologies associated with impairments in spatial learning and memory whilst such changes were largely absent in WT mice. Interestingly, assessment of microglia by IHC demonstrated reduced interaction with white matter cerebrovasculature in Trem2-/- mice. Taken together, these data support a role for microglia in cerebrovascular contributions to cognitive decline and dementia. Therefore, targeting regulators of microglia reactivity may provide means to influence cerebrovascular disease trajectory and associated cognitive changes. While further work is required to delineate the precise function of microglia in this context, our preclinical data suggest TREM2-regulated microglial responses to cerebrovascular insult are important for maintenance of brain health and cognitive resilience. Future work will continue to decipher how TREM2 mediates such resilience with particular focus on interaction with other cell types within the neurogliovascular unit.

Introduction

Angiogenic mediators like placental growth factor (PlGF) and vascular endothelial growth factors (VEFG-C and VEFG-A) in cerebrospinal fluid (CSF) are suggested markers of cerebral small vessel disease (SVD). SVD is a cause of vascular cognitive impairment and dementia (VCID), but studies have shown that both non-amyloid SVD related to vascular risk factors and cerebral amyloid angiopathy (CAA) often exist in patients with Alzheimer's Disease (AD). CSF amyloid beta (Abeta) 42 is reduced in AD due to trapping in parenchymal plaques. Abeta40 is mainly deposited in the vasculature, and low CSF concentrations are seen in CAA. In this cross-sectional study, we examine the associations between these angiogenic factors, vascular risk and white matter hyperintensities (WMH) on MRI, as well as Abeta peptides in CSF.

Methods

We recruited non-demented participants from the Norwegian Dementia Disease Initiation cohort. We measured PlGF, VEGF-C and VEGF-A in CSF. Vascular risk was assessed with the Framingham Risk Score (FRS) for cardiovascular disease. WMH volumes were calculated by an automated algorithm. We used linear regression to examine associations between angiogenic markers and FRS, CSF levels of Abeta42 and Abeta40. Associations with WMH load were assessed in models without (Model 1) and with (Model 2) correction for amyloid status. Continuous variables were standardized. Age and sex were covariates.

Results

In total, 240 individuals (mean age 63.4 years, 128 female/112 male, 124 cognitively normal/116 cognitively impaired) were included. Reduced VEGF-C was associated with higher FRS (B=-0.292, p<0.001) and reduced Abeta42 (B=0.261, p<0.001) and Abeta40 (B=0.574, p<0.001). We also found a negative association between WMH load and VEGF-C (B=-0.233, p<0.001), that remained significant after correction for amyloid status. Increased PlGF was associated with higher FRS (B=0.186, p<0.001), lower Abeta40 (B=-0.111, p=0.029) and increased WMH load (B=0.188, p=0.026), the latter remaining significant after correction for amyloid status.

Discussion

Both angiogenic factors VEGF-C and PlGF are associated with vascular risk, Abeta40 and WMH load, suggesting a role in both SVD and AD pathogenesis. These factors should be included in longitudinal studies to further confirm their impact on disease processes and elucidate mechanisms involved in the interaction between SVD and AD.

Introduction

The brain renin-angiotensin system (RAS) is dysregulated in dementia. We have previously shown that ACE-2, a central regulator of the protective counter-regulatory arm of RAS, is inversely associated with disease pathology in Alzheimer's disease (AD). We have investigated whether ACE-2 is similarly deficient in Vascular dementia (VaD) and mixed dementia (AD-VaD), in addition to AD. We also investigated whether ACE-2 is related to vascular pathology including CAA and SVD and explored whether ACE-2 varies according to gender, hypertension status, and ACE-2 genotype.

Methods

We studied brain tissue (frontal cortex) from 147 dementia cases (AD (n=94), VaD (n=20) and AD-VaD (n=33)) and 104 age-matched non-demented controls from the South West Dementia Brain Bank, University of Bristol. Amyloid β (Aβ) and tau pathology and levels, had previously been measured by IHC and ELISA, respectively. ACE-2 protein levels were measured by ELISA, and ACE-2 enzyme activity was measured using a fluorometric sensolyte kit (Anaspec). ACE-1 activity was measured using a fluorogenic assay; Ang-II and Ang-(1-7) were measured by in-house direct ELISA. ACE-2 genotypes (rs2285666 and rs4240157) were obtained by PCR.

Results

ACE-2 enzyme activity was significantly reduced in AD and AD-VaD cases (p<0.0001 and p=0.0039, respectively) but not VaD. ACE-2 protein levels were unchanged between dementia groups. ACE-2 activity correlated inversely with parenchymal Aβ (r=-0.223, p=0.0005) and tau load (r=-0.294, p<0.0001) and with insoluble Aβ40 and Aβ42 levels (r=-0.267 and r=-0.289, both p<0.0001). ACE-2 activity correlated inversely with ACE-1 activity (r=−0.227, p=0.0004), and the ratio of ACE-1 to ACE-2 was significantly increased in AD and AD-VaD cases (p<0.0001 and p=0.0029, respectively) but not in VaD. ACE-2 activity was lower in females with AD (p=0.0015). There is no relationship with CAA/SVD. ACE-2 activity was higher in people with late-stage hypertension (p=0.044), and females with hypertension have lower enzyme activity than males (p=0.041). ACE-2 levels and activity werenot associated with ACE-2 genotypes.

Discussion

These findings indicate that, despite strong vascular properties, changes in ACE-2 function are AD-related and not altered in VaD. The reduction in ACE-2 in females in AD warrants further investigation. We did not find any association with ACE-2 genotypes.

Introduction

The Gothenburg Mild Cognitive Impairment (MCI) study is a longitudinal mono-center study of patients seeking help for cognitive complaints at the memory clinic in Gothenburg, Sweden. The study includes both pre-clinical diagnoses, e.g. subjective cognitive impairment (SCI) and mild cognitive impairment (MCI), as well as patients with manifest dementia, including Alzheimer's disease (AD), subcortical small-vessel disease (SSVD) and mixed AD/SSVD. The International Working Group (IWG) for New Research Criteria for the Diagnosis of AD has proposed a conceptual framework for guiding diagnosis by biomarker analysis. In short, patients with typical AD and mixed AD/SSVD should display decreased amyloid-β (Aβ) 1-42 together with increased total tau or phosphorylated tau in cerebrospinal fluid (CSF).

Methods

In this project, we used the IWG-2 criteria to help the exploration of preclinical CSF biomarkers for SSVD. To this end, we investigated the odds of SCI and MCI patients with and without AD pathology converting to SSVD. Moreover, we investigated how CSF biomarker levels at baseline affected risk of converting to SSVD. The applied cut-offs for AD pathology were Aβ-42 < 530 ng/L, t-tau>350 ng/L and p-tau181>59 ng/L. The study cohort consisted of 29 SCI with AD pathology and 173 SCI without AD pathology, and 98 MCI with AD pathology and 203 MCI without AD pathology. CSF biomarkers Aβ-38, Aβ-40 and Aβ-42, and soluble amyloid precursor protein (sAPP) alpha and beta were analyzed at baseline.

Results

While SCI and MCI patients with pathological AD biomarkers were 30 times more likely to convert to AD and 15 times more likely to convert to mixed AD/SSVD, pathological AD biomarkers did not predict conversion to SSVD. Using Cox regression analysis, we found that higher levels of sAPP-α and sAPP-β at baseline were associated with lower risk of converting to SSVD. Moreover, Kaplan- Meier estimations showed that when preclinical subjects were stratified according to baseline levels of sAPP-α or Aβ-40, those with the lower levels of the proteins had increased probability of converting to SSVD. No other biomarkers were associated with conversion to SSVD.

Discussion

sAPP-α/-β and Aβ-40 could be used as potential biomarkers to evaluate progression to SSVD.