Neuritic Plaque Density Research Articles

Human Alzheimer's Disease ATN/ABC Staging Applied to Aging Rhesus Macaque Brains: Association With Cognition and MRI-Based Regional Gray Matter Volume.

The brain changes of Alzheimer's disease (AD) include Abeta (Aβ)amyloid plaques ("A"), abnormally phosphorylated tau tangles ("T"), and neurodegeneration ("N"). These have been used to construct in vivo and postmortem diagnostic and staging classifications for evaluating the spectrum of AD in the "ATN" and "ABC" ("B" for Braak tau stage, "C" for Consortium to Establish a Registry for Alzheimer's Disease [CERAD] neuritic plaque density) systems. Another common AD feature involves cerebral amyloid angiopathy (CAA). We report the first experiment to examine relationships among cognition, brain distribution of amyloid plaques, CAA, tau/tangles, and magnetic resonance imaging (MRI)-determined volume changes (as a measure of "N") in the same group of behaviorally characterized nonhuman primates. Both ATN and ABC systems were applied to a group of 32 rhesus macaques aged between 7 and 33 years. When an immunohistochemical method for "T" and "B" was used, some monkeys were "triple positive" on ATN, with a maximum ABC status of A1B2C3. With silver or thioflavin S methods, however, all monkeys were classified as T-negative and B0, indicating the absence of mature neurofibrillary tangles (NFTs) and hence neuropathologically defined AD. Although monkeys at extremes of the ATN and ABC classifications, or with frequent CAA, had significantly lower scores on some cognitive tests, the lack of fully mature NFTs or dementia-consistent cognitive impairment indicates that fully developed AD may not occur in rhesus macaques. There were sex differences noted in the types of histopathology present, and only CAA was significantly related to gray matter volume.

Ante‐mortem magnetic resonance imaging grey‐white matter contrast regional signatures of Alzheimer’s disease neuropathology

AbstractBackgroundGrey matter (GM), white matter (WM) contrast (GWC) in T1‐weighted MRI has been shown to decrease with age in healthy populations and cognitive impairment in clinical Alzheimer’s Disease (AD). However, the neuropathological determinants of this signal remain unknown. Here, we aimed to study whether GWC is associated with AD neuropathology and longitudinal hippocampal atrophy.Method157 patients with neuropathological, clinical data and ante‐mortem MRI were selected from the National Alzheimer’s Coordinating Center database. Cortical volume and GWC (WM/GM intensity) in T1/MRI were obtained with Freesurfer 6.0. Hippocampal volume was divided into anterior, intermediate and posterior regions using a lab‐based algorithm. Correlational analysis was conducted for GWC with age, and GWC residuals after linear regression with age for volume, BRAAK stage (neurofibrillary tangles), CERAD score (neuritic plaque density) and Cognitive Dementia Rating Sum‐of‐Boxes (CDR‐SB). APOE genotypes were compared using one‐way‐ANOVA.ResultGWC was negatively correlated with age in widespread brain areas (p < 0.05, FDR), but only the entorhinal cortex showed a positive correlation between volume and GWC. There were no significant correlations between GWC and BRAAK stage, CERAD score, CDR‐SB or differences according to APOE genotype. Entorhinal GWC correlated positively only with the posterior hippocampal volume in BRAAK III‐IV.ConclusionGWC is highly modulated by age, but not by classical AD neuropathology, APOE genotype or dementia severity in this cohort. Entorhinal GWC correlates with entorhinal and posterior hippocampal volume, suggesting it might reflect an early pathophysiological process distinct from classical AD neuropathology.

Association between military service and Alzheimer's disease neuropathology at autopsy.

Anti-amyloid therapies are at the forefront of efforts to treat Alzheimer's disease (AD). Identifying amyloid risk factors may aid screening and intervention strategies. While veterans face increased exposure to risk factors, whether they face a greater neuropathologic amyloid burden is not well understood. Male decedents donating to two Alzheimer's Disease Research Center (ADRC) brain banks from 1986 to 2018 with categorized neuritic plaque density and neurofibrillary tangles (n=597) were included. Using generalized ordered logistic regression we modeled each outcome's association with military history adjusting for age and death year. Having served in the military (60% of sample) is associated with post mortem neuritic amyloid plaque (for each comparison of higher to lower C scores OR=1.26; 95% confidence interval [CI]=1.06-1.49) and tau pathology (B score OR=1.10; 95% CI=1.08-1.12). This is the first study, to our knowledge, finding increased levels of verified AD neuropathology in those with military service. Targeted veteran AD therapies is a pressing need.

Amyloid PET across the cognitive spectrum in former professional and college American football players: findings from the DIAGNOSE CTE Research Project

BackgroundExposure to repetitive head impacts (RHI) in American football players can lead to cognitive impairment and dementia due to neurodegenerative disease, particularly chronic traumatic encephalopathy (CTE). The pathognomonic lesion of CTE consists of perivascular aggregates of hyper-phosphorylated tau in neurons at the depths of cortical sulci. However, it is unclear whether exposure to RHI accelerates amyloid-β (Aβ) plaque formation and increases the risk for Alzheimer’s disease (AD). Although the Aβ neuritic plaques characteristic of AD are observed in a minority of later-stage CTE cases, diffuse plaques are more common. This study examined whether former professional and college American football players, including those with cognitive impairment and dementia, have elevated neuritic Aβ plaque density, as measured by florbetapir PET. Regardless of cognitive and functional status, elevated levels of florbetapir uptake were not expected.MethodsWe examined 237 men ages 45–74, including 119 former professional (PRO) and 60 former college (COL) football players, with and without cognitive impairment and dementia, and 58 same-age men without a history of contact sports or TBI (unexposed; UE) and who denied cognitive or behavioral symptoms at telephone screening. Former players were categorized into four diagnostic groups: normal cognition, subjective memory impairment, mild cognitive impairment, and dementia. Positive florbetapir PET was defined by cortical-cerebellar average SUVR of ≥ 1.10. Multivariable linear regression and analysis of covariance (ANCOVA) compared florbetapir average SUVR across diagnostic and exposure groups. Multivariable logistic regression compared florbetapir positivity. Race, education, age, and APOE4 were covariates.ResultsThere were no diagnostic group differences either in florbetapir average SUVR or the proportion of elevated florbetapir uptake. Average SUVR means also did not differ between exposure groups: PRO-COL (p = 0.94, 95% C.I. = [− 0.033, 0.025]), PRO-UE (p = 0.40, 95% C.I. = [− 0.010, 0.029]), COL-UE (p = 0.36, 95% CI = [0.0004, 0.039]). Florbetapir was not significantly associated with years of football exposure, cognition, or daily functioning.ConclusionsCognitive impairment in former American football players is not associated with PET imaging of neuritic Aβ plaque deposition. These findings are inconsistent with a neuropathological diagnosis of AD in individuals with substantial RHI exposure and have both clinical and medico-legal implications.Trial registrationNCT02798185.

Age-related hearing loss and dementia-related neuropathology: An analysis of the United Kingdom brains for dementia research cohort.

Age-related hearing loss frequently precedes or coexists with mild cognitive impairment and dementia. The role specific neuropathologies play in this association, as either a cause or a consequence, is unclear. We therefore aimed to investigate whether specific dementia related neuropathologies were associated with hearing impairment in later life. We analysed data on ante-mortem hearing impairment with post-mortem neuropathological data for 442 participants from the Brains for Dementia Research Cohort. Binary logistic regression models were used to estimate the association of hearing impairment with the presence of each dementia-related neuropathology overall, and with specific staged changes. All analyses adjusted for age and sex, and several sensitivity analyses were conducted to test the robustness of findings. Presence and density of neuritic plaques were associated with higher odds of hearing impairment ante-mortem (OR = 3.65, 95% CI 1.78-7.46 for frequent density of plaques). Presence of any LB disease was likewise associated with hearing impairment (OR = 2.10, 95% CI 1.27-3.48), but this did not increase with higher cortical pathology (OR = 1.53, 95% CI 0.75-3.11). Nonspecific amyloid deposition, neurofibrillary tangle staging, overall AD neuropathology level, and cerebrovascular disease were not clearly associated with increased risks of hearing impairment. Our results provide some support for an association between dementia-related neuropathology and hearing loss and suggest that hearing loss may be associated with a high neuritic plaque burden and more common in Lewy body disease.

Inflammation and the pathological progression of Alzheimer's disease are associated with low circulating choline levels.

Deficiency of dietary choline, an essential nutrient, is observed worldwide, with ~ 90% of Americans beingdeficient. Previous work highlights a relationship between decreased choline intake and an increased risk for cognitive decline and Alzheimer's disease (AD). The associations between blood circulating choline and the pathological progression in both mild cognitive impairment (MCI) and AD remain unknown. Here, we examined these associations ina cohort of patients with MCI with presence of either sparse or high neuritic plaque density and Braak stage and a second cohortwith either moderate AD (moderate to frequent neuritic plaques, Braak stage = IV) or severe AD (frequent neuritic plaques, Braak stage = VI), compared to age-matched controls. Metabolomic analysis was performed on serum from the AD cohort. We then assessed the effects of dietary choline deficiency (Ch-) in 3xTg-AD mice and choline supplementation (Ch+) in APP/PS1 mice, tworodent models of AD. The levels of circulating choline were reduced while pro-inflammatory cytokine TNFαwas elevated in serum of both MCI sparse and high pathology cases. Reduced choline and elevated TNFα correlated with higher neuritic plaque density and Braak stage. In AD patients, we found reductions in choline, its derivative acetylcholine (ACh), and elevated TNFα. Choline and ACh levelswere negatively correlated with neuritic plaqueload, Braak stage, and TNFα, but positively correlated with MMSE, and brain weight. Metabolites L-Valine, 4-Hydroxyphenylpyruvic, Methylmalonic, and Ferulic acids were significantly associated with circuiting choline levels. In 3xTg-AD mice, the Ch- diet increased amyloid-β levels and tau phosphorylation in cortical tissue, and TNFαin both blood and cortical tissue, paralleling the severe human-AD profile. Conversely, the Ch+ diet increased choline and ACh while reducing amyloid-βand TNFαlevels in brains of APP/PS1 mice. Collectively, low circulating choline is associated with AD-neuropathological progression, illustrating the importance of adequate dietary choline intake to offset disease.

Neuropathological features of antemortem atrophy‐based subtypes of Alzheimer’s disease

AbstractBackgroundPure Alzheimer’s disease (AD), characterized by combined amyloid and tau pathology, is not the most prevalent form of the disease as non‐AD pathologies (e.g., alpha‐synuclein and TDP‐43) are commonly observed postmortem. The role of AD and non‐AD pathologies is unclear in relation to disease heterogeneity. Therefore, we investigated whether antemortem MRI‐based atrophy subtypes of AD differ in postmortem neuropathological features and comorbid non‐AD pathologies.MethodsWe selected individuals from the ADNI with antemortem MRI evaluating brain atrophy within 2 years before death; antemortem diagnosis of AD dementia/mild cognitive impairment; and a postmortem‐confirmed AD neuropathologic change. Antemortem atrophy subtypes were modeled as continuous phenomena using a recent conceptual framework: typicality (spanning limbic predominant AD to hippocampal sparing AD) and severity (spanning typical AD to minimal atrophy AD). Postmortem neuropathological evaluation included AD hallmarks (amyloid‐beta, tau), non‐AD pathologies (alpha‐synuclein, TDP‐43) and concomitant pathological burden. Partial correlations assessed the associations between antemortem atrophy subtype dimensions and postmortem neuropathological outcomes.ResultsIn 31 individuals (mean age = 80y, 26% females), antemortem typicality was significantly associated with neuropathological features: amyloid‐beta (rho = ‐0.39 overall), tau (rho = ‐0.38 regionally), neuritic plaque density (rho = ‐0.4 overall), alpha‐synuclein (rho = ‐0.39 regionally), TDP‐43 (rho = ‐0.49 overall), and concomitance pathological burden (rho = ‐0.59 regionally). This suggests that limbic predominant AD was associated with higher burden of these pathologies compared to hippocampal sparing AD. Antemortem severity was significantly associated with concomitant pathological burden (rho = ‐0.43 regionally), such that typical AD showed higher burden than minimal atrophy AD.ConclusionsBased on our direct antemortem‐to‐postmortem validation, we hypothesize that: (a) typicality and severity in atrophy reflect differential aspects of susceptibility of the brain to AD and non‐AD pathologies; (b) limbic predominant AD and typical AD subtypes may share similar biological pathways, making them more vulnerable to the investigated AD and non‐AD pathologies compared to hippocampal sparing AD, which may follow a different biological pathway. Our findings provide a deeper understanding of associations of atrophy subtypes in AD with different pathologies, enhancing prevailing knowledge of biological heterogeneity in AD.

Association of Traumatic Brain Injury with Late Life Neuropathological Outcomes in a Community-Based Cohort.

Prior studies into the association of head trauma with neuropathology have been limited by incomplete lifetime neurotrauma exposure characterization. To investigate the neuropathological sequelae of traumatic brain injury (TBI) in an autopsy sample using three sources of TBI ascertainment, weighting findings to reflect associations in the larger, community-based cohort. Self-reported head trauma with loss of consciousness (LOC) exposure was collected in biennial clinic visits from 780 older adults from the Adult Changes in Thought study who later died and donated their brain for research. Self-report data were supplemented with medical record abstraction, and, for 244 people, structured interviews on lifetime head trauma. Neuropathology outcomes included Braak stage, CERAD neuritic plaque density, Lewy body distribution, vascular pathology, hippocampal sclerosis, and cerebral/cortical atrophy. Exposures were TBI with or without LOC. Modified Poisson regressions adjusting for age, sex, education, and APOE ɛ4 genotype were weighted back to the full cohort of 5,546 participants. TBI with LOC was associated with the presence of cerebral cortical atrophy (Relative Risk 1.22, 95% CI 1.02, 1.42). None of the other outcomes was associated with TBI with or without LOC. TBI with LOC was associated with increased risk of cerebral cortical atrophy. Despite our enhanced TBI ascertainment, we found no association with the Alzheimer's disease-related neuropathologic outcomes among people who survived to at least age 65 without dementia. This suggests the pathophysiological processes underlying post-traumatic neurodegeneration are distinct from the hallmark pathologies of Alzheimer's disease.

Characteristics and Predictors of Alzheimer's Disease Resilience Phenotype.

Alzheimer's disease (AD) is characterized by cognitive impairment in the presence of cerebral amyloid plaques and neurofibrillary tangles. Less is known about the characteristics and predictors of resilience to cognitive impairment in the presence of neuropathological evidence of AD, the focus of this study. Of 3170 adults age ≥65 years in the National Alzheimer's Coordinating Center (NACC) brain autopsy cohort, 1373 had evidence of CERAD level moderate to frequent neuritic plaque density and Braak stage V-VI neurofibrillary tangles. Resilience was defined by CDR-SOB and CDR-Global scores of 0-2.5 and 0-0.5, respectively, and non-resilience, CDR-SOB and CDR-Global scores >2.5 and >0.5, respectively. Multivariable logistic regression models were used to examine the independent associations of patient characteristics with resilience. There were 62 participants (4.8%) with resilience. Those with resilience were older (mean age, 88.3 vs. 82.4 years), more likely to be women (61.3% vs. 47.3%) and had a lower prevalence of the APOE-e4 carrier (41.9% vs. 56.2%). They also had a higher prevalence of hypertension, heart failure, atrial fibrillation, diuretic use, beta-blocker use, and APOE-e2 carrier status. Greater age at death, diuretic use, and APOE-e2 were the only characteristics independently associated with higher odds of the AD resilience phenotype (adjusted OR, 1.09; 95% CI, 1.05-1.13; p < 0.01; 2.00 (1.04-3.87), p = 0.04, 2.71 (1.31-5.64), p < 0.01, respectively). The phenotype of resilience to cognitive impairment is uncommon in older adults who have neuropathological evidence of AD.

Protective Association of HLA-DRB1*04 Subtypes in Neurodegenerative Diseases Implicates Acetylated Tau PHF6 Sequences

Objective To explore genetic association between human leukocyte antigen (HLA) and neurodegenerative diseases and investigate mechanisms behind the association. Background Pathophysiology of Alzheimer's disease (AD), Parkinson's disease (PD) and amyotrophic lateral sclerosis (ALS) involves accumulation of tau (neurofibrillary tangles) and amyloid-ß-rich (amyloid plaques) aggregates in AD, a-synuclein-rich aggregates (Lewy bodies) in PD and TDP-43 aggregates in ALS, although these aggregates may also co-occur. Likewise, consensus is growing that tau may play a key role in PD and ALS as well. Design/Methods We analyzed HLA associations in ∼176,000 individuals with PD or AD versus controls across ancestry groups. Pursuing this, we also compared postmortem brain density of neurofibrillary tangles and amyloid plaques in brain, tau and Aß42 levels in cerebrospinal fluid (CSF) of ∼8,000 individuals (controls and AD), and examined association of HLA in ∼2,500 patient with pathologically demonstrated Lewy Body Dementia. This was followed by HLA binding and tetramer T cell studies. Results A shared genetic association was observed across AD and PD at rs601945 (PD: odds ratio (OR) = 0.84; 95% confidence interval, [0.80; 0.88]; p = 2.2 x 10-13; AD: OR = 0.91[0.89; 0.93]; p = 1.8 x 10-22) and with a protective HLA association recently reported in ALS. Hierarchical protective effects of HLA-DRB1*04 subtypes best accounted for the association, strongest with HLA-DRB1*04:04 and HLA-DRB1*04:07, intermediary with HLA-DRB1*04:01 and HLA-DRB1*04:03 and absent for HLA-DRB1*04:05. The same signal was associated with decreased neurofibrillary tangle (but not neuritic plaque) density postmortem and was more associated with lower tau levels than Aß42 level changes in CSF. Furthermore, protective HLA-DRB1*04 subtypes strongly bound the aggregation-prone tau PHF6 sequence, but only when acetylated at K311, a modification central to aggregation. T cells recognizing this epitope were identified, showing relevance of this immune response in patients with neurodegenerative disorders. Conclusions An HLA-DRB1*04-mediated adaptive immune response, potentially against tau, decreases PD, AD and ALS risk, offering the possibility of new therapeutic avenues.

Protective association of HLA‐DRB1*04 subtypes in neurodegenerative diseases implicates acetylated tau PHF6 sequences

AbstractBackgroundAlzheimer’s disease (AD), Parkinson’s disease (PD), Amyotrophic Lateral Sclerosis (ALS) and other neurodegenerative diseases are responsible for considerable morbidity and mortality. With incidence rising with aging, these also represent a growing societal challenge. Pathophysiology involves accumulation of tau (neurofibrillary tangles) and Amyloid‐β‐rich (amyloid plaques) aggregates in AD, α‐synuclein‐rich aggregates (Lewy bodies) in PD and TDP‐43 aggregates in ALS, although co‐presence of these aggregates may occur. Consensus is also growing that tau may also play a key role in PD and ALS.MethodUsing genome‐wide association data, we analyzed Human Leukocyte Antigen (HLA) associations in over 176,000 individuals with PD or Alzheimer’s AD disease versus controls across ancestry groups.ResultA shared genetic association was observed across diseases at rs601945 (PD: odds ratio (OR)=0.84; 95% confidence interval, [0.80; 0.88]; p=2.2x10‐13; AD: OR=0.91[0.89; 0.93]; p=1.8x10‐22), and with a protective HLA association recently reported in ALS. Hierarchical protective effects of HLA‐DRB1*04 subtypes best accounted for the association, strongest with HLA‐DRB1*04:04 and HLA‐DRB1*04:07, intermediary with HLA‐DRB1*04:01 and HLA‐DRB1*04:03, and absent for HLA‐DRB1*04:05. The same signal was associated with decreased neurofibrillary tangles (but not neuritic plaque density) in postmortem brains and was more strongly associated with tau levels than Aβ42 levels in the cerebrospinal fluid. Finally, protective HLA‐DRB1*04 subtypes strongly bound the aggregation‐prone tau PHF6 sequence, but only when acetylated at K311, a modification central to aggregation.ConclusionAn HLA‐DRB1*04‐mediated adaptive immune response, potentially against tau, decreases PD, AD and ALS risk, offering the possibility of new therapeutic avenues.

A blood‐based diagnostic for Alzheimer’s disease using spectral microscopy of immuno‐enriched Aβ from frozen PBMCs

AbstractBackgroundIn Alzheimer’s disease (AD), toxic Aβ peptides aggregate into higher molecular weight assemblies and accumulate not only in the extracellular space, but also in the walls of blood vessels in the brain, increasing their permeability, and promoting immune cell migration and activation. As immune cells contact these pathological brain materials, they may act as “sentinels” that are detectable once they return to the circulation. Previously, we have demonstrated that leukocytes, when stained with an amyloid sensitive probe, K114 (Tocris Bioscience), display distinct spectral changes in subjects with AD and mild cognitive impairment (MCI) (Black et al. 2022). Here we extend this work by introducing an enhanced method that combines the specificity of immunocapture of Aβ peptides together with spectral interrogation to reveal their amyloid character from easily obtainable frozen peripheral blood mononuclear cells (PBMCs).Methods30 frozen PBMC samples were obtained from the National Centralized Repository for Alzheimer’s Disease and Related Dementias (NCRAD) with 15 clinically‐ and histologically‐confirmed MCI/AD and 15 cognitively normal subjects based on the National Alzheimer’s Coordinating Center (NACC) database. To adapt our method to frozen samples, we used immunoprecipitation to purify target amyloid proteins by anti‐Aβ antibody (4G8)‐coated magnetic beads (Protein G SureBeads™, BioRad Laboratories), which were then labelled with K114, and imaged with a spectral confocal microscope.ResultsComparing subjects with neuropathologically‐confirmed AD (n=6), Braak stage for neurofibrillary degeneration (B score) &gt;5 and density of neocortical neuritic plaques (C score) &gt;2 to cognitively normal controls (n=6), our technique detected highly significant differences between groups (P&lt;0.005, Fig. 1). Correlation between our AD Score and B scores was R = 0.824, and with cognitive status was R = 0.735 (Fig. 2).ConclusionsThese observations indicate that our method is capable of detecting AD from circulating human PBMCs, potentially mirroring the “Aβ load” in the brain. Our technique could constitute a reliable and inexpensive biomarker for early AD and AD‐related MCI.

Neuropathological validation of plasma GFAP

AbstractBackgroundGlial fibrillary acidic protein (GFAP) is an astrocytic marker that has been recently associated with fluid and imaging biomarkers of amyloid and tau pathologies in the Alzheimer’s disease (AD) spectrum. Plasma GFAP has also shown to be a strong indicator of early brain amyloidosis in preclinical AD. However, it remains to be confirmed how plasma GFAP associates with neuropathological hallmarks of AD and which pathological entities are being reflected by this plasmatic marker.MethodPlasma GFAP concentrations were measured using a commercial Simoa assay on participants of the UCSD Shiley‐Marcos Alzheimer’s Disease Research Center (ADRC), consisting of 271 participants with brain autopsy data. Amyloid and tau pathologies were assessed following the CERAD, Braak and NIA‐Reagan criteria, as well as with tangle and plaque counts (147 participants). Cerebral amyloid angiopathy (CAA) was graded as recommended by NACC Neuropathology Working Group. Non‐AD pathologies were also assessed: Lewy body disease, hippocampal sclerosis, TDP‐43 and vascular pathology. The distribution of GFAP concentration was compared across groups using ANCOVA models adjusting for age and sex, followed by post‐hoc Tukey’s HSD test. The association between GFAP and the pathological indexes was tested using linear models and adjusted by covariates.ResultConcentrations of plasma GFAP were higher in females as compared to males (P=0.008) and no age effect was observed. GFAP also increased with severity of AD pathological stages (P&lt;0.001), with increased neuritic (P&lt;0.001) and diffuse plaque density or counts (P=0.001), as well as with Braak stages and tangle counts (P&lt;0.05). We found no association between tangle counts and GFAP when accounting for the effect of plaque counts. The presence of co‐pathologies did not affect average GFAP levels. We found no association between GFAP and CAA.ConclusionPlasma GFAP showed again here to highly reflect amyloid deposition. Results indicate, however, that this association is due to the accumulation of extra‐cellular amyloid in the form of plaques rather than its deposition in blood vessels. Abnormal accumulation of non‐AD proteins did not show any marked effect on GFAP levels. More detailed analysis, including longitudinal retrospective data, is ongoing.

An Epigenome‐wide association study of psychosis in Alzheimer's disease dorsolateral prefrontal cortex

AbstractBackgroundPsychosis is a debilitating syndrome occurring in 40‐60% of people with Alzheimer’s disease (AD) and corresponds with a more severe disease course. Evidence suggests that psychosis in AD (AD+P) is associated with a distinct profile of neurobiological changes, but little is known about the molecular processes driving etiology. In this study we performed an epigenome‐wide association study (EWAS) to investigate DNA methylation associated with AD+P in the dorsolateral prefrontal cortex of 192 post‐mortem brain samples.MethodBrain samples with corresponding in life neuropsychiatric assessments were obtained from the University of Pittsburgh Alzheimer’s disease Research Center (PITT‐ADRC). AD pathology was assessed and classified using CERAD neuritic plaque density score, Braak neurofibrillary tangle stages and NIA‐RI criteria. The presence or absence of delusions and hallucinations was scored on the CERAD Behavioral Rating Scale. DNA was extracted, bisulfite treated and then profiled on the Illumina Methylation EPIC Array.ResultAfter data processing and quality control we used linear regression models to compare 152 AD+P samples to 40 AD samples without psychosis (AD‐P). A regional analysis of spatially correlated p‐values highlighted four differentially methylated regions (DMRs) associated with psychosis, which are being replicated in other data sets and validated for cell specificity using fluorescence activated nuclei sorting (FANS).ConclusionThe development of effective therapies for AD+P is an urgent priority. To address this we have collated a well powered study cohort to interrogate the epigenetic basis of AD+P, finding significant methylomic variation. This variation provides an insight into potential mechanisms and biomarkers which will help to identify drug targets and enable better treatment with existing medications.

Neuropathologic Features of Antemortem Atrophy-Based Subtypes of Alzheimer Disease.

Background and ObjectivesTo investigate whether antemortem MRI-based atrophy subtypes of Alzheimer disease (AD) differ in neuropathologic features and comorbid non-AD pathologies at postmortem.MethodsFrom the Alzheimer's Disease Neuroimaging Initiative cohort, we included individuals with antemortem MRI evaluating brain atrophy within 2 years before death, antemortem diagnosis of AD dementia/mild cognitive impairment, and postmortem-confirmed AD neuropathologic change. Antemortem atrophy subtypes were modeled as continuous phenomena based on a recent conceptual framework: typicality (spanning limbic-predominant AD to hippocampal-sparing AD) and severity (spanning typical AD to minimal atrophy AD). Postmortem neuropathologic evaluation included AD hallmarks, β-amyloid, and tau as well as non-AD pathologies, alpha-synuclein and TAR DNA-binding protein 43 (TDP-43). We also investigated the overall concomitance across these pathologies. Partial correlations assessed the associations between antemortem atrophy subtypes and postmortem neuropathologic outcomes.ResultsIn 31 individuals (26 AD dementia/5 mild cognitive impairment, mean age = 80 years, 26% females), antemortem typicality was significantly negatively associated with neuropathologic features, including β-amyloid (rho = −0.39 overall), tau (rho = −0.38 regionally), alpha-synuclein (rho = −0.39 regionally), TDP-43 (rho = −0.49 overall), and concomitance of pathologies (rho = −0.59 regionally). Limbic-predominant AD was associated with higher Thal phase, neuritic plaque density, and presence of TDP-43 compared with hippocampal-sparing AD. Regionally, limbic-predominant AD showed a higher presence of tau and alpha-synuclein pathologies in medial temporal structures, a higher presence of TDP-43, and concomitance of pathologies subcortically/cortically compared with hippocampal-sparing AD. Antemortem severity was significantly negatively associated with concomitance of pathologies (rho = −0.43 regionally), such that typical AD showed higher concomitance of pathologies than minimal atrophy AD.DiscussionWe provide a direct antemortem-to-postmortem validation, highlighting the importance of understanding atrophy-based heterogeneity in AD relative to AD and non-AD pathologies. We suggest that (1) typicality and severity in atrophy reflect differential aspects of susceptibility of the brain to AD and non-AD pathologies; and (2) limbic-predominant AD and typical AD subtypes share similar biological pathways, making them more vulnerable to AD and non-AD pathologies compared with hippocampal-sparing AD, which may follow a different biological pathway. Our findings provide a deeper understanding of associations of atrophy subtypes in AD with different pathologies, enhancing the prevailing knowledge of biological heterogeneity in AD and could contribute toward tracking disease progression and designing clinical trials in the future.

Classification of 18F-Flutemetamol scans in cognitively normal older adults using machine learning trained with neuropathology as ground truth

PurposeEnd-of-life studies have validated the binary visual reads of 18F-labeled amyloid PET tracers as an accurate tool for the presence or absence of increased neuritic amyloid plaque density. In this study, the performance of a support vector machine (SVM)-based classifier will be tested against pathological ground truths and its performance determined in cognitively healthy older adults.MethodsWe applied SVM with a linear kernel to an 18F-Flutemetamol end-of-life dataset to determine the regions with the highest feature weights in a data-driven manner and to compare between two different pathological ground truths: based on neuritic amyloid plaque density or on amyloid phases, respectively. We also trained and tested classifiers based on the 10% voxels with the highest amplitudes of feature weights for each of the two neuropathological ground truths. Next, we tested the classifiers’ diagnostic performance in the asymptomatic Alzheimer’s disease (AD) phase, a phase of interest for future drug development, in an independent dataset of cognitively intact older adults, the Flemish Prevent AD Cohort-KU Leuven (F-PACK). A regression analysis was conducted between the Centiloid (CL) value in a composite volume of interest (VOI), as index for amyloid load, and the distance to the hyperplane for each of the two classifiers, based on the two pathological ground truths. A receiver operating characteristic analysis was also performed to determine the CL threshold that optimally discriminates between neuritic amyloid plaque positivity versus negativity, or amyloid phase positivity versus negativity, within F-PACK.ResultsThe classifiers yielded adequate specificity and sensitivity within the end-of-life dataset (neuritic amyloid plaque density classifier: specificity of 90.2% and sensitivity of 83.7%; amyloid phase classifier: specificity of 98.4% and sensitivity of 84.0%). The regions with the highest feature weights corresponded to precuneus, caudate, anteromedial prefrontal, and also posterior inferior temporal and inferior parietal cortex. In the cognitively normal cohort, the correlation coefficient between CL and distance to the hyperplane was −0.66 for the classifier trained with neuritic amyloid plaque density, and −0.88 for the classifier trained with amyloid phases. This difference was significant. The optimal CL cut-off for discriminating positive versus negative scans was CL = 48–51 for the different classifiers (area under the curve (AUC) = 99.9%), except for the classifier trained with amyloid phases and based on the 10% voxels with highest feature weights. There the cut-off was CL = 26 (AUC = 99.5%), which closely matched the CL threshold for discriminating phases 0–2 from 3–5 based on the end-of-life dataset and the neuropathological ground truth.DiscussionAmong a set of neuropathologically validated classifiers trained with end-of-life cases, transfer to a cognitively normal population works best for a classifier trained with amyloid phases and using only voxels with the highest amplitudes of feature weights.

APOE \u03b54, Alzheimer\u2019s disease neuropathology and sleep disturbance, in individuals with and without dementia

BackgroundApolipoprotein E epsilon 4 (APOE-ε4) carrier status is an established risk factor for Alzheimer’s disease (AD) dementia. It has also been linked with sleep disturbance in healthy older adults and increased insomnia risk. This association may be driven by the effect of APOE-ε4 on AD pathological change, itself associated with sleep abnormalities. To assess this relationship, we have evaluated post-mortem neuropathological findings in patients with and without cognitive impairment and AD pathology, who had extensive clinical assessment within 12 months of death.MethodsThis retrospective cohort study used UK Brain Banks Network data. Eligible subjects were aged over 50, with pre-mortem neuropsychiatry inventory scores of sleep disturbance (NPI-K), neurocognitive testing and functional cognitive status assessment (Clinical Dementia Rating scale). Neuropathological data included Thal phase, Braak stage and CERAD scores (measures of Aβ plaque distribution, tangle distribution and neuritic plaque density, respectively) combined to form the National Institute on Aging Alzheimer’s Association (NIA-AA) ABC score reflecting AD neuropathology. Participants with other significant intracerebral pathology or pathological features of non-AD dementia were excluded.Multivariate linear regression was performed with NPIK Global Score (NPIK frequency score multiplied by severity score) as the dependent variable and APOE-ε4 heterozygosity or homozygosity as independent variables. Covariates included age, gender, APOE-ε2 status and ABC NPI measures reflecting depression and anxiety. Further models stratified by ABC score and functional cognitive status were also produced.ResultsSeven hundred twenty-eight records were identified. Two hundred two participants were included in the final analysis: mean (SD) age 84.0 (9.2) and MMSE 14.0 (11.8). Mean sleep disturbance scores were highest in ε4 homozygosity (n=11), 4.55 (5.4); intermediate in ε4 heterozygosity (n=95), 2.03 (4.0); and lowest in non-ε4 carriers (n=96), 1.36 (3.3). Within the full sample, controlling for pathological status, age, gender, depression, anxiety and CDR-SOB status, APOE-ε4 homozygosity was associated with sleep disturbance (β 2.53, p=0.034). APOE-ε4 heterozygosity was similarly associated in individuals without dementia (β 1.21, p=0.048).ConclusionThese findings lend weight to the hypothesis that APOE-ε4 affects sleep by mechanisms independent of AD pathological change. Evaluation of those mechanisms would enhance understanding of sleep disturbance pathways and potentially provide treatment targets.

Neuropathology of late life depression: Clinical predictors of amyloid and tau neuropathology in non-demented older adults with depression.

Previous studies regarding the relationship between depression and amyloid and tau neuropathology have reported conflicting findings. We examined whether depression is associated with higher Alzheimer's disease neuropathologic changes and whether sex moderates their relationships. Using the National Alzheimer's Coordinating Center database (2005-2020), we conducted a cross-sectional study of non-demented older adults (age 50+; CDR ≤ 0.5) who had autopsy within 1 year of their last clinic visit. Multivariable cumulative logit models were fitted to determine if recent and/or remote depression were associated with Thal phase score (a measure of spread of amyloid plaques) modified according to National Institute on Aging-Alzheimer's Association (NIA-AA) guidelines, modified Braak stage for neurofibrillary degeneration according to NIA-AA guidelines, density of neuritic plaques [CERAD score] and if any of their associations were moderated by sex. All regression models were adjusted for covariates associated with both depression and Alzheimer's disease, including selective serotonin or serotonin norepinephrine reuptake inhibitor use, sex, age, years of education, the presence of apolipoprotein E e4 allele, and history of diabetes, hypertension, hypercholesteremia, and traumatic brain injury. We included 395 participants (94 Thal, 393 Braak, and 394 CERAD). Those who had recent (within previous 2 years) but not remote depression were more likely to have higher Thal phase compared to those without a history of depression (Odds Ratio = 13.3; 95% CI, 1.5-116.3, p = 0.019). Sex did not moderate the association between recent depression and Thal phase. No significant associations between depression and Braak or CERAD scores were observed. Our findings suggest that recently active late-life depression is associated with spread of amyloid pathology beyond cortical regions to include subcortical regions but not with density of neuritic plaques or neurofibrillary tangles.

Cluster analysis of neuropathologic features in the National Alzheimer's Coordinating Center data set.

Presence of multiple pathologies associated with neurodegenerative disease at autopsy is common. We investigated whether unsupervised cluster analysis of neuropathologic features resulted in distinct neuropathologic profiles, and compared demographic and clinical features between clusters. We included autopsied participants from the National Alzheimer's Coordinating Center Uniform Data Set whose last visit was within two years of death. Participants were excluded if they had rare neuropathologic diseases or were not evaluated for each neuropathology variable used for clustering. We applied a hierarchical clustering algorithm using amyloid plaques (Thal phase, neuritic plaque density), tau neurofibrillary tangles (Braak stage, frontotemporal lobar degeneration (FTLD) tau presence), vascular pathology (infarcts, microinfarcts, arteriosclerosis, atherosclerosis, cerebral amyloid angiopathy), Lewy bodies (LB), and transactive response DNA-binding protein 43 (TDP-43) inclusions. We compared neuropathologic, demographic, and clinical features of the resulting clusters. The algorithm identified seven distinct clusters (Figure 1) of the 1,156 participants that met inclusion criteria. Four clusters included high levels of Alzheimer's disease neuropathologic change (ADNC), characterized as ADNC+TDP, ADNC+LB, ADNC+FTLD-tau, and ADNC alone. Two clusters were characterized by high levels of TDP-43 or FTLD-tau, but mild burden of other pathologies, and the remaining cluster had mild burden of all pathologies. Vascular pathologies were prevalent across all clusters. In general, primary etiologic diagnosis among those who were cognitively impaired at their last visit corresponded well with the defining neuropathologies of each cluster (Figure 2). In the ADNC+LB cluster, primary clinical diagnosis was rarely Lewy body dementia (LBD). Even in clusters with mild ADNC, Alzheimer's disease was commonly the primary diagnosis. Overall, ADNC+TDP and ADNC+LB clusters had the most impairment at their last visit, with the highest prevalence of cognitive symptoms and lowest scores on cognitive tests. The cluster with mild pathologic burden, while having the highest proportion of participants with normal cognition, also had the highest proportions with mild cognitive impairment. Despite the diverse combinations of pathologies present at autopsy, unsupervised cluster analysis revealed distinct pathologic profiles of neurodegenerative disease. Clusters with mixed pathologies had higher cognitive impairment. Primary clinical diagnoses largely reflected neuropathologic burden, although Alzheimer's disease was commonly diagnosed in clusters with low ADNC burden.

Presence of co‐pathology in sporadic early‐onset Alzheimer disease versus dominantly inherited Alzheimer disease

A small proportion of Alzheimer disease (AD), known as early onset AD (EOAD), has symptomatic age at onset (AAO) before age 65. About 5-10% of EOAD is dominantly inherited (DIAD); the rest is termed to be sporadic (sEOAD). Although DIAD and sEOAD share the hallmark plaques and tangles that define AD neuropathologic change (ADNC), the relative burdens of these lesions and the frequencies of non-AD co-pathologies in sEOAD relative to DIAD remain unknown.We compared the neuropathological burden of AD and the frequency of AD and non-AD pathologies in 363 sEOAD cases from the National Alzheimer's Coordinating Center (NACC) and in 62 DIAD cases (45 from the Dominantly Inherited Alzheimer Network (DIAN); 17 from NACC). Operational criteria for the classification of AD and other co-pathologies followed accepted NACC guidelines. Only cases with AAO under 65 and a primary pathological diagnosis of 'high ADNC' were included.DIAD participants [mean AAO = 42.9 ± 8.1 years] had higher CERAD scores than sEOAD cases [mean AAO = 57.1 ±7.2 years] [p=0.03]. Braak stages were similar for both cohorts. The frequency and severity of cerebral amyloid angiopathy (CAA) was higher in DIAD versus sEOAD [CAA: 100% vs 83.7%, p=0.001; severe CAA: 40.3% versus 20.1%, p<0.001, respectively]. The frequency of at least one non-AD/non-CAA pathology was similar between DIAD and sEOAD [63.9% vs 59.7%, p=0.61], but the frequency of multiple pathologies (two or more) was lower in DIAD [3.2%] than in sEOAD [21.0%, p<0.001]. Lewy body disease (LBD) was the most prevalent non-AD/non-CAA pathology in both cohorts [58.1% in DIAD, 51.2% in sEOAD; p=0.39]. Hippocampal sclerosis [14.5%] and argyrophilic grain disease [2.5%], were observed in sEOAD, but were absent from DIAD.DIAD cases show greater neuritic plaque density and more severe CAA than sEOAD cases, but comparable Braak NFT stages. The similar frequencies of LBD in both cohorts may be linked to severe AD neuropathological change, rather than co-incident age-related pathologies. Future studies should include methodologically uniform assessments of both cohorts to explore age-related and non-age-related mechanisms that may account for differences in the burdens of ADNC lesions and non-AD co-pathologies.