Reduced clinical and postmortem measures of cardiac pathology in subjects with advanced Alzheimer's Disease

Interactions between vascular burden and amyloid-β pathology on trajectories of tau accumulation

Cerebrovascular pathology often co-exists with Alzheimer's disease pathology and can contribute to Alzheimer's disease-related clinical progression. However, the degree to which vascular burden contributes to Alzheimer's disease pathological progression is still unclear. This study aimed to investigate interactions between vascular burden and amyloid-β pathology on both baseline tau tangle load and longitudinal tau accumulation. We included 1229 participants from the Swedish BioFINDER-2 Study, including cognitively unimpaired and impaired participants with and without biomarker-confirmed amyloid-β pathology. All underwent baseline tau-PET (18F-RO948), and a subset (n = 677) underwent longitudinal tau-PET after 2.5 ± 1.0 years. Tau-PET uptake was computed for a temporal meta-region-of-interest. We focused on four main vascular imaging features and risk factors: microbleeds; white matter lesion volume; stroke-related events (infarcts, lacunes and haemorrhages); and the Framingham Heart Study Cardiovascular Disease risk score. To validate our in vivo results, we examined 1610 autopsy cases from an Arizona-based neuropathology cohort on three main vascular pathological features: cerebral amyloid angiopathy; white matter rarefaction; and infarcts. For the in vivo cohort, primary analyses included age-, sex- and APOE ɛ4-corrected linear mixed models between tau-PET (outcome) and interactions between time, amyloid-β and each vascular feature (predictors). For the neuropathology cohort, age-, sex- and APOE ɛ4-corrected linear models between tau tangle density (outcome) and an interaction between plaque density and each vascular feature (predictors) were performed. In cognitively unimpaired individuals, we observed a significant interaction between microbleeds and amyloid-β pathology on greater baseline tau load (β = 0.68, P < 0.001) and longitudinal tau accumulation (β = 0.11, P < 0.001). For white matter lesion volume, we did not observe a significant independent interaction effect with amyloid-β on tau after accounting for microbleeds. In cognitively unimpaired individuals, we further found that stroke-related events showed a significant negative interaction with amyloid-β on longitudinal tau (β = -0.08, P < 0.001). In cognitively impaired individuals, there were no significant interaction effects between cerebrovascular and amyloid-β pathology at all. In the neuropathology dataset, the in vivo observed interaction effects between cerebral amyloid angiopathy and plaque density (β = 0.38, P < 0.001) and between infarcts and plaque density (β = -0.11, P = 0.005) on tau tangle density were replicated. To conclude, we demonstrated that cerebrovascular pathology-in the presence of amyloid-β pathology-modifies tau accumulation in early stages of Alzheimer's disease. More specifically, the co-occurrence of microbleeds and amyloid-β pathology was associated with greater accumulation of tau aggregates during early disease stages. This opens the possibility that interventions targeting microbleeds may attenuate the rate of tau accumulation in Alzheimer's disease.

Cerebral white matter rarefaction has both neurodegenerative and vascular causes and may primarily be a distal axonopathy

Cerebral white matter rarefaction (CWMR) was considered by Binswanger and Alzheimer to be due to cerebral arteriolosclerosis. Renewed attention came with CT and MR brain imaging, and neuropathological studies finding a high rate of CWMR in Alzheimer disease (AD). The relative contributions of cerebrovascular disease and AD to CWMR are still uncertain. In 1181 autopsies by the Arizona Study of Aging and Neurodegenerative Disorders (AZSAND), large-format brain sections were used to grade CWMR and determine its vascular and neurodegenerative correlates. Almost all neurodegenerative diseases had more severe CWMR than the normal control group. Multivariable logistic regression models indicated that Braak neurofibrillary stage was the strongest predictor of CWMR, with additional independently significant predictors including age, cortical and diencephalic lacunar and microinfarcts, body mass index, and female sex. It appears that while AD and cerebrovascular pathology may be additive in causing CWMR, both may be solely capable of this. The typical periventricular pattern suggests that CWMR is primarily a distal axonopathy caused by dysfunction of the cell bodies of long-association corticocortical projection neurons. A consequence of these findings is that CWMR should not be viewed simply as "small vessel disease" or as a pathognomonic indicator of vascular cognitive impairment or vascular dementia.

Spectral Decomposition of the Flow and Characterization of the Sound Signals through Stenoses with Different Levels of Severity

Treatments of atherosclerosis depend on the severity of the disease at the diagnosis time. Non-invasive diagnosis techniques, capable of detecting stenosis at early stages, are essential to reduce associated costs and mortality rates. We used computational fluid dynamics and acoustics analysis to extensively investigate the sound sources arising from high-turbulent fluctuating flow through stenosis. The frequency spectral analysis and proper orthogonal decomposition unveiled the frequency contents of the fluctuations for different severities and decomposed the flow into several frequency bandwidths. Results showed that high-intensity turbulent pressure fluctuations appeared inside the stenosis for severities above 70%, concentrated at plaque surface, and immediately in the post-stenotic region. Analysis of these fluctuations with the progression of the stenosis indicated that (a) there was a distinct break frequency for each severity level, ranging from 40 to 230 Hz, (b) acoustic spatial-frequency maps demonstrated the variation of the frequency content with respect to the distance from the stenosis, and (c) high-energy, high-frequency fluctuations existed inside the stenosis only for severe cases. This information can be essential for predicting the severity level of progressive stenosis, comprehending the nature of the sound sources, and determining the location of the stenosis with respect to the point of measurements.

Spectral Decomposition and Sound Source Localization of Highly Disturbed Flow through a Severe Arterial Stenosis

For the early detection of atherosclerosis, it is imperative to explore the capabilities of new, effective noninvasive diagnosis techniques to significantly reduce the associated treatment costs and mortality rates. In this study, a multifaceted comprehensive approach involving advanced computational fluid dynamics combined with signal processing techniques was exploited to investigate the highly turbulent fluctuating flow through arterial stenosis. The focus was on localizing high-energy mechano-acoustic source potential to transmit to the epidermal surface. The flow analysis results showed the existence of turbulent pressure fluctuations inside the stenosis and in the post-stenotic region. After analyzing the turbulent kinetic energy and pressure fluctuations on the flow centerline and the vessel wall, the point of maximum excitation in the flow was observed around two diameters downstream of the stenosis within the fluctuating zone. It was also found that the concentration of pressure fluctuation closer to the wall was higher inside the stenosis compared to the post-stenotic region. Additionally, the visualization of the most energetic proper orthogonal decomposition (POD) mode and spectral decomposition of the flow indicated that the break frequencies ranged from 80 to 220 Hz and were correlated to the eddies generated within these regions.

Increased Risk of Autopsy-Proven Pneumonia with Sex, Season and Neurodegenerative Disease

There has been a markedly renewed interest in factors associated with pneumonia, a leading cause of death worldwide, due to its frequent concurrence with pandemics of influenza and Covid-19 disease. Reported predisposing factors to both bacterial pneumonia and pandemic viral lower respiratory infections are wintertime occurrence, older age, obesity, pre-existing cardiopulmonary conditions and diabetes. Also implicated are age-related neurodegenerative diseases that cause parkinsonism and dementia. We investigated the prevalence of autopsy-proven pneumonia in the Arizona Study of Aging and Neurodegenerative Disorders (AZSAND), a longitudinal clinicopathological study, between the years 2006 and 2019 and before the beginning of the Covid-19 pandemic. Of 691 subjects dying at advanced ages (mean 83.4), pneumonia was diagnosed postmortem in 343 (49.6%). There were 185 subjects without dementia or parkinsonism while clinicopathological diagnoses for the other subjects included 319 with Alzheimer's disease dementia, 127 with idiopathic Parkinson's disease, 72 with dementia with Lewy bodies, 49 with progressive supranuclear palsy and 78 with vascular dementia. Subjects with one or more of these neurodegenerative diseases all had higher pneumonia rates, ranging between 50 and 61%, as compared to those without dementia or parkinsonism (40%). In multivariable logistic regression models, male sex and a non-summer death both had independent contributions (ORs of 1.67 and 1.53) towards the presence of pneumonia at autopsy while the absence of parkinsonism or dementia was a significant negative predictor of pneumonia (OR 0.54). Male sex, dementia and parkinsonism may also be risk factors for Covid-19 pneumonia. The apolipoprotein E4 allele, as well as obesity, chronic obstructive pulmonary disease, diabetes, hypertension, congestive heart failure, cardiomegaly and cigarette smoking history, were not significantly associated with pneumonia, in contradistinction to what has been reported for Covid-19 disease.

Cardiovascular Disease, Diabetes Mellitus, and Hypertension in Lewy Body Disease: A Comparison with Other Dementia Disorders

Background:

Research concerning the potential roles of cardiovascular disease (CaVD) and diabetes mellitus (DM) as risk factors for Lewy body disease (LBD) is limited. These disorders are, however, established risk factors for vascular dementia (VaD) and have been proposed as risk factors for Alzheimer’s disease (AD).

Objective:

The aim of this study was to investigate the prevalence of CaVD and DM in LBD and compare the results with previous findings in cases with AD, VaD, and mixed AD-VaD (MD).

Methods:

Autopsy reports at the Clinical Department of Pathology in Lund from 2001–2018 were analyzed. All cases with a complete neuropathological diagnosis of LBD were selected, not distinguishing between subjects with clinical Parkinson disease dementia and dementia with Lewy bodies, on the condition of a clinical diagnosis of dementia. Clinical data were retrieved through the patients’ medical records and the Swedish National Diabetes Register (NDR) and compared with those of the AD, VaD, and MD cases.

Results:

In LBD, there was less CaVD, significantly less DM (p = 0.002) and likewise significantly less hypertension (p < 0.001) than in VaD. The results of the LBD group were consistent with the results of the AD group.

Conclusion:

Our findings of a low prevalence of CaVD and CaVD risk factors in LBD and in AD argue against the association between these risk factors and their contribution to the development of neurodegenerative diseases.

A High-Cholesterol Diet Increases 27-Hydroxycholesterol and Modifies Estrogen Receptor Expression and Neurodegeneration in Rabbit Hippocampus

Hypercholesterolemia has been implicated in numerous health problems from cardiovascular disease to neurodegeneration. High serum cholesterol levels in midlife have been associated with an increased risk of developing Alzheimer's disease (AD) later in life which suggests that the pathways leading to AD pathology might be activated decades before the symptoms of the disease are detected. Cholesterol-fed animals, particularly cholesterol-fed rabbits, exhibit brain pathology similar to the changes found in brains of AD patients. Dietary cholesterol, which cannot pass the blood-brain barrier, is thought to influence central nervous system homeostasis by increased transport of its circulatory breakdown product, 27-hydroxycholesterol (27-OHC), into the brain. 27-OHC is an endogenous selective estrogen receptor modulator. Estrogen-mediated non-reproductive functions require estrogen receptors (ERs) and include modulation of mitochondrial function and structure, as well as regulation of synaptogenesis in the brain. ERs are located in brain areas affected early in AD pathogenesis, including the hippocampus. Here we report that increase in serum cholesterol, induced by feeding rabbits a high-cholesterol diet, is associated with higher levels of 27-OHC in the brain as well as increased levels of neurodegeneration in the hippocampus. Furthermore, these results are accompanied by changes in expression of ERs in the hippocampus as well as a decrease in hippocampal mitochondria. These findings provide an important insight into one of the possible mechanisms involved in the development of AD, and shed light on the processes that may antedate amyloid-β and tau phosphorylation changes currently hypothesized to cause AD symptomology and pathology.

A Cross-Sectional Analysis of Late-Life Cardiovascular Factors and Their Relation to Clinically Defined Neurodegenerative Diseases

Studies have demonstrated associations between cardiovascular factors and Alzheimer disease (AD) with minimal focus on other neurodegenerative diseases. Utilizing cross-sectional data from 17,532 individuals in the National Alzheimer's Coordinating Center, Uniform Data Set, we compared the presence of cardiovascular factors [body mass index (BMI), atrial fibrillation, hypertension, hyperlipidemia, and diabetes] in individuals carrying a diagnosis of Probable AD (ProbAD), Possible AD, vascular dementia, dementia with Lewy bodies (DLB), frontotemporal dementia, Parkinson disease, progressive supranuclear palsy, or corticobasal degeneration, with that of normals. Generalized linear mixed models were fitted with age at visit, gender, and cardiovascular factors as fixed effects and Alzheimer's Disease Centers as random effects. In late life, only BMI of ProbAD and DLB patients was statistically significantly lower than that in normals (P-values <0.001). When accounting for colinearity within cardiovascular factors, a low BMI was a comorbidity of certain dementia etiologies as compared with normals. These data support a concept of disease-specific associations with certain cardiovascular factors.

Numerical analysis of blood flow through an elliptic stenosis using large eddy simulation

The presence of a stenosis caused by the abnormal narrowing of the lumen in the artery tree can cause significant variations in flow parameters of blood. The original flow, which is believed to be laminar in most situations, may turn out to turbulent by the geometric perturbation created by the stenosis. Flow may evolve to fully turbulent or it may relaminarise back according to the intensity of the perturbation. This article reports the numerical simulation of flow through an eccentrically located asymmetric stenosis having elliptical cross section using computational fluid dynamics. Large eddy simulation technique using dynamic Smagorinsky sub-grid scale model is applied to capture the turbulent features of flow. Analysis is carried out for two situations: steady inflow as ideal condition and pulsatile inflow corresponding to the actual physiological condition in common carotid artery. The spatially varying pulsatile inflow waveforms are mathematically derived from instantaneous mass flow measurements available in the literature. Carreau viscosity model is used to estimate the effect of non-Newtonian nature of blood. The present simulations for steady and pulsatile conditions show that post-stenotic flow field undergoes transition to turbulence in all cases. The characteristics of mean and turbulent flow fields have been presented and discussed in detail.

Feasibility Study: Comparison of Frontal Cortex Needle Core Versus Open Biopsy for Detection of Characteristic Proteinopathies of Neurodegenerative Diseases

The clinical diagnosis and classification of neurodegenerative diseases based on clinical examination or available biomarkers are currently insufficiently accurate. Although histologic examination is considered the gold standard for diagnosis, brain biopsies have been avoided because of the high risk-benefit ratio. However, brain biopsies have previously been performed with a craniotomy and excision of approximately 1 cm of cerebral cortex tissue, and it is possible that needle core brain biopsies would have a lower morbidity and mortality risk. Here, we compared the ability of simulated needle core biopsy versus simulated open biopsy to detect the frontal cortex histopathology associated with common neurodegenerative diseases in the elderly using 144 autopsy-proven cases. Simulated needle core biopsy, as compared with simulated open biopsy, gave close to 90% sensitivity and specificity for identifying graded densities of β-amyloid and neuritic plaques, neurofibrillary tangles, phosphorylated α-synuclein, and phosphorylated TDP-43 pathology. This study shows that the presence and densities of the most common molecular pathologies may be histopathologically assessed in simulated frontal cortex needle biopsies, with accuracy very close to that obtained by open cortical biopsy. An accurate estimation of the morbidity and mortality risk associated with cortical needle core biopsy will require specifically designed clinical trials in appropriate subjects.

Antemortem Prediction of Braak Stage

We examined the extent to which tauopathy distribution, as determined by Braak staging, might be predicted by various risk factors in older individuals. The Swedish Twin Registry provided extensive information on neuropsychological function, lifestyle, and cardiovascular risk factors of 128 patients for whom autopsy data including Braak staging were available. Logistic regression was used to develop a prognostic model that targeted discrimination between Braak stages 0 to II and III to VI. The analysis showed that Braak stages III to VI were significantly predicted by having 1 or more APOE ε4 alleles, older age, high total cholesterol, absence of diabetes and cardiovascular disease, and poorer scores on the Wechsler Adult Intelligence Score Information test, verbal fluency, and recognition memory but better verbal recall. The algorithm predicted Braak stages III to VI well (receiver-operating characteristic area under curve, 0.897; 95% confidence interval, 0.842-0.951). Using a cutoff of 50% risk or more, the sensitivity was 85%, the specificity was 70%, and the negative predictive value was 69%. This study demonstrates that tauopathy distribution can be accurately predicted using a combination of antemortem patient data. These results provide further insight into tauopathy development and AD-related disease mechanisms and suggest a prognostic model that predicts the spread of neurofibrillary tangles above the transentorhinal stage.

Arizona Study of Aging and Neurodegenerative Disorders and Brain and Body Donation Program

The Brain and Body Donation Program (BBDP) at Banner Sun Health Research Institute (http://www.brainandbodydonationprogram.org) started in 1987 with brain-only donations and currently has banked more than 1600 brains. More than 430 whole-body donations have been received since this service was commenced in 2005. The collective academic output of the BBDP is now described as the Arizona Study of Aging and Neurodegenerative Disorders (AZSAND). Most BBDP subjects are enrolled as cognitively normal volunteers residing in the retirement communities of metropolitan Phoenix, Arizona. Specific recruitment efforts are also directed at subjects with Alzheimer's disease, Parkinson's disease and cancer. The median age at death is 82. Subjects receive standardized general medical, neurological, neuropsychological and movement disorders assessments during life and more than 90% receive full pathological examinations by medically licensed pathologists after death. The Program has been funded through a combination of internal, federal and state of Arizona grants as well as user fees and pharmaceutical industry collaborations. Subsets of the Program are utilized by the US National Institute on Aging Arizona Alzheimer's Disease Core Center and the US National Institute of Neurological Disorders and Stroke National Brain and Tissue Resource for Parkinson's Disease and Related Disorders. Substantial funding has also been received from the Michael J. Fox Foundation for Parkinson's Research. The Program has made rapid autopsy a priority, with a 3.0-hour median post-mortem interval for the entire collection. The median RNA Integrity Number (RIN) for frozen brain and body tissue is 8.9 and 7.4, respectively. More than 2500 tissue requests have been served and currently about 200 are served annually. These requests have been made by more than 400 investigators located in 32 US states and 15 countries. Tissue from the BBDP has contributed to more than 350 publications and more than 200 grant-funded projects.

Increased Alzheimer's disease neuropathology is associated with type 2 diabetes and ApoE ε.4 carrier status

BACKGROUND

Past studies investigating the association between Alzheimer's disease (AD) pathology and diabetes mellitus type 2 (DM2) have provided conflicting results. While several studies indicate that subjects with comorbid AD and DM2 have less AD pathology, others have found no significant differences in AD pathology between the two groups. Other studies have indicated that individuals with AD and DM2 have significantly greater neuropathology than AD individuals who do not have DM2. Additional research has demonstrated that ApoE ε4 carriers with AD and DM2 have significantly greater pathology than ApoE ε4 non-carriers.

METHODS

Data on clinically and pathologically diagnosed Alzheimer's disease cases (NINDS-ADRDA clinically and NIA Reagan intermediate or high pathologically) with DM2 (n= 40) and those without DM2 (n= 322) from the Banner Sun Health Research Institute Brain and Body Donation Program were obtained for this study. Plaque and tangle scores from the frontal, parietal, temporal, entorhinal and hippocampal regions were compared between the DM2+ and DM2 - groups. In addition, total plaque count, total tangle count, and Braak scores were also compared between groups. Similar analyses were conducted to determine the effect of ApoE ε4 carrier status on the neuropathological variables while also accounting for and DM2 status.

RESULTS

The DM2+ and DM2 - groups showed no significant differences on plaque and tangle pathology. Logistic regression analyses, which accounted for the effects of ApoE .ε4 carrier status and age at death, found no association between total plaque [OR 1.05 (0.87, 1.27), p = 0.60] or total tangle [OR 0.97 (0.89, 1.07) p = 0.58] counts and DM2 status. ApoE ε4 carrier status was not significantly associated with DM2 status [.Χ2 = 0.30 (df = 1), p = 0.58]. Within the DM2+ group, significantly greater plaque and tangle pathology was found for ApoE ε4 carriers in relation to DM2+ ApoE ε4 non-carriers.

CONCLUSION

Overall, the presence of DM2 does not affect plaque and tangle burden in a sample of clinically and pathologically confirmed AD cases. Among AD individuals with DM2, those who are ApoE ε4 carriers had significantly greater neuropathology than those who do not carry an ApoE ε4 allele. Positive DM2 status appears to exacerbate AD neuropathology in the presence of ApoE ε4.

[Chronic inflammation and biomarkers. Is ageing an expression of chronic inflammation?]

Ageing shows a high interindividual and intraindividual variability. Subclinical and clinical cardiovascular diseases accelerate the ageing process in part and in total. This leads to the idea that ageing is a result of a chronic inflammation process and to the term "inflammageing". A variety of biomarkers (e.g. C-reactive protein, interleukin-6, tumor necrosis factor alpha, fibrinogen, albumin and serum amyloid A) are described in this context. Furthermore there is a relationship to changes in the immune system across the lifespan (immunosenescence), viral infections, the occurrence of markers of oxidative stress and genetic changes. At this point in time the role for determining ageing and its use as a prognostic tool seems to be impossible. Whether inflammageing is a valid model for describing the ageing process or is the consequence of other mechanisms needs further discussion.