Tau Tangle Density Research Articles

Associations of renin-angiotensin system inhibitor use with brain insulin signaling and neuropathology.

To examine the associations of renin-angiotensin system (RAS) inhibitor use with postmortem brain insulin signaling and neuropathology. Among Religious Orders Study participants, 150 deceased and autopsied older individuals (75 with diabetes matched to 75 without by age at death, sex, and education) had measurements of insulin receptor substrate-1 (IRS-1) and RAC-alpha serine/threonine protein kinase (AKT1) collected in the prefrontal cortex using ELISA and immunohistochemistry. Alzheimer's disease (AD), brain infarcts, and cerebral vessel pathology data were assessed by systematic neuropathologic evaluations. RAS inhibitor use was determined based on visual inspection of medication containers during study visits. The associations of RAS inhibitor use with brain insulin signaling measures and neuropathology were examined using adjusted regression analyses. Of the 90 RAS inhibitor users (54 with diabetes), 65 had used only angiotensin-converting enzyme inhibitors, 11 only angiotensin II receptor blockers, and 14 used both. RAS inhibitor use was associated with lower pT308AKT1/total AKT1, but not with pS307IRS-1/total IRS-1 or the density of cells stained positive for pS616 IRS-1. RAS inhibitor use was not associated with the level of global AD pathology or amyloid beta burden, but it was associated with a lower tau-neurofibrillary tangle density. Additionally, we found a significant interaction between diabetes and RAS inhibitors on tangle density. Furthermore, AKT1 phosphorylation partially mediated the association of RAS inhibitor use with tau tangle density. Lastly, RAS inhibitor use was associated with more atherosclerosis, but not with other cerebral blood vessel pathologies or cerebral infarcts. Late-life RAS inhibitor use may be associated with lower brain AKT1 phosphorylation and fewer neurofibrillary tangles.

Proteins linking APOE ɛ4 with Alzheimer's disease.

The ɛ4 allele of the apolipoprotein E gene (APOE ɛ4) is the strongest genetic risk factor for Alzheimer's disease (AD), but the mechanisms connecting APOE ɛ4 to AD are not clear. Participants (n=596) were from two clinical-pathological studies. Tissues from dorsolateral prefrontal cortex were examined to identify 8425 proteins. Post mortem pathological assessment used immunohistochemistry to obtain amyloid beta (Aβ) load and tau tangle density. In separate models, APOE ɛ4 was associated with 18 proteins, which were associated with Aβ and tau tangles. Examining the proteins in a single model identified Netrin-1 and secreted frizzled-related protein 1 (SFRP1) as the two proteins linking APOE ɛ4 with Aβ with the largest effect sizes and Netrin-1 and testican-3 linking APOE ɛ4 with tau tangles. We identified Netrin-1, SFRP1, and testican-3 as the most promising proteins that link APOE ɛ4 with Aβ and tau tangles. Of 8425 proteins extracted from prefrontal cortex, 18 were related to APOE ɛ4. The 18 proteins were also related to amyloid beta (Aβ) and tau. The 18 proteins were more related to APOE ɛ4 than other AD genetic risk variants. Netrin-1 and secreted frizzled-related protein 1 were the two most promising proteins linking APOE ɛ4 with Aβ. Netrin-1 and testican-3 were two most promising proteins linking APOE ɛ4 with tau.

Associations of Serum Insulin and Related Measures With Neuropathology and Cognition in Older Persons With and Without Diabetes.

To examine associations of serum insulin and related measures with neuropathology and cognition in older persons. We studied 192 older persons (96 with diabetes and 96 without, matched by sex and balanced by age-at-death, education, and postmortem interval) from a community-based, clinical-pathologic study of aging, with annual evaluations including neuropsychological testing (summarized into global cognition and 5 cognitive domains) and postmortem autopsy. We assessed serum insulin, glucose, leptin, adiponectin, hemoglobin A1C, advanced glycation-end products (AGEs), and receptors for advanced glycation-end products, and calculated the Homeostasis Model Assessment of Insulin Resistance (HOMA-IR) and adiponectin-to-leptin ratio. Using adjusted regression analyses, we examined the associations of serum measures with neuropathology of cerebrovascular disease and Alzheimer's disease, and with the level of cognition proximate-to-death. Higher HOMA-IR was associated with the presence of brain infarcts and specifically microinfarcts, and higher HOMA-IR and leptin were each associated with subcortical infarcts. Further, higher leptin levels and lower adiponectin-to-leptin ratios were associated with the presence of moderate-to-severe atherosclerosis. Serum insulin and related measures were not associated with the level of Alzheimer's disease pathology, as assessed by global, as well as amyloid burden or tau tangle density scores. Regarding cognitive outcomes, higher insulin and leptin levels, and lower adiponectin and receptors for advanced glycation-end products levels, respectively, were each associated with lower levels of global cognition. Peripheral insulin resistance indicated by HOMA-IR and related serum measures was associated with a greater burden of cerebrovascular neuropathology and lower cognition. ANN NEUROL 2024;95:665-676.

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.

Age-related and amyloid-beta-independent tau deposition and its downstream effects.

Amyloid-β (Aβ) is hypothesized to facilitate the spread of tau pathology beyond the medial temporal lobe. However, there is evidence that, independently of Aβ, age-related tau pathology might be present outside of the medial temporal lobe. We therefore aimed to study age-related Aβ-independent tau deposition outside the medial temporal lobe in two large cohorts and to investigate potential downstream effects of this on cognition and structural measures. We included 545 cognitively unimpaired adults (40-92 years) from the BioFINDER-2 study (in vivo) and 639 (64-108 years) from the Rush Alzheimer's Disease Center cohorts (ex vivo). 18F-RO948- and 18F-flutemetamol-PET standardized uptake value ratios were calculated for regional tau and global/regional Aβ in vivo. Immunohistochemistry was used to estimate Aβ load and tangle density ex vivo. In vivo medial temporal lobe volumes (subiculum, cornu ammonis 1) and cortical thickness (entorhinal cortex, Brodmann area 35) were obtained using Automated Segmentation for Hippocampal Subfields packages. Thickness of early and late neocortical Alzheimer's disease regions was determined using FreeSurfer. Global cognition and episodic memory were estimated to quantify cognitive functioning. In vivo age-related tau deposition was observed in the medial temporal lobe and in frontal and parietal cortical regions, which was statistically significant when adjusting for Aβ. This was also observed in individuals with low Aβ load. Tau deposition was negatively associated with cortical volumes and thickness in temporal and parietal regions independently of Aβ. The associations between age and cortical volume or thickness were partially mediated via tau in regions with early Alzheimer's disease pathology, i.e. early tau and/or Aβ pathology (subiculum/Brodmann area 35/precuneus/posterior cingulate). Finally, the associations between age and cognition were partially mediated via tau in Brodmann area 35, even when including Aβ-PET as covariate. Results were validated in the ex vivo cohort showing age-related and Aβ-independent increases in tau aggregates in and outside the medial temporal lobe. Ex vivo age-cognition associations were mediated by medial and inferior temporal tau tangle density, while correcting for Aβ density. Taken together, our study provides support for primary age-related tauopathy even outside the medial temporal lobe in vivo and ex vivo, with downstream effects on structure and cognition. These results have implications for our understanding of the spreading of tau outside the medial temporal lobe, also in the context of Alzheimer's disease. Moreover, this study suggests the potential utility of tau-targeting treatments in primary age-related tauopathy, likely already in preclinical stages in individuals with low Aβ pathology.

Estrogen Receptor Genes, Cognitive Decline, and Alzheimer Disease.

Lifetime risk of Alzheimer's disease (AD) dementia is two-fold higher in women compared with men, and low estrogen levels in post menopause have been suggested as a possible contributor. We examined 3 ERs (GPER1, ER2, ER1) variants in association with AD traits as an indirect method to test the association between estrogen and AD in women. While the study focus was on women, in a comparison we separately examined ER molecular variants in men. Participants were followed for an average 10 years in one of two longitudinal clinical pathological studies of aging. Global cognition was assessed using a composite score derived from 19 neuropsychological tests' scores. Postmortem pathological assessment included examination of 3 AD (amyloid-β and tau tangles determined by immunohistochemistry, and a global AD pathology score derived from diffuse and neurotic plaques and neurofibrillary tangles count) and 8 non-AD pathology indices. ER molecular genomic variants included genotyping and examining ER DNA methylation and RNA expression in brain regions including dorsolateral prefrontal cortex (DLPFC) that are major players in cognition and often have AD pathology. Mean age of women (N=1711) at baseline was 78.0 (SD=7.7) years. In women, GPER1 molecular variants had the most consistent associations with AD traits. GPER1 DNA methylation was associated with cognitive decline, tau tangles density, and global AD pathology score. GPER1 RNA expression in DLPFC was related to cognitive decline and tau tangles density. Other associations included associations of ER2 and ER1 SNPs and DNA methylation with cognition. RNA expressions in DLPFC of genes involved in signaling mechanisms of activated ERs were also associated with cognitive decline and tau tangles density in women. In men (N=651, average age at baseline: 77.4 (SD=7.3)), there were less robust associations between ER molecular genomic variants and AD cognitive and pathological traits. No consistent association was seen between ER molecular genomic variations and non-AD pathologies in either of sexes. ER DNA methylation and RNA expression, and to some extent ER polymorphisms, were associated with AD cognitive and pathologic traits in women, and to a lower extent in men.

Uncovering single‐nucleus RNA velocity variations in neuropathologic Alzheimer’s disease

AbstractBackgroundDifferential single‐nucleus (snRNA‐seq) gene expression analyses in Alzheimer’s disease (AD) provide fixed snapshots of cellular alterations, failing to detect the temporal dynamics of genes at individual cells. To overcome this limitation, here we analyze single‐nucleus RNA velocities (RNA‐vel) from the prefrontal cortex to characterize dynamic genetic and cellular differences in neuropathological AD progression. RNA‐vel is the rate of change of gene expression obtained by comparing intronic and exonic sequence counts. Comparison of AD pathology associated gene expression with parallel RNA‐vel differences reveals sets of genes and molecular pathways that underlie the static and putative dynamic regimes of cell type‐specific dysregulations underlying the disease.MethodWe used snRNA‐seq data from the prefrontal cortex of 48 subjects1 with varied levels of AD pathology from ROSMAP2. We then calculated both the expression and RNA‐vel differences between low AD‐pathology and mild‐to‐severe AD‐pathology. These differences were cell‐specific across six major cell types: excitatory neurons, inhibitory neurons, astrocytes, microglia, oligodendrocytes, and oligodendrocyte progenitor cells.1. We characterized RNA‐vel differences associated with four AD neuropathology traits: neuritic plaque, neuronal neurofibrillary tangle, overall β‐amyloid load, and PHF tau tangle density.2. We demonstrated the reproducibility of the RNA‐vel differences in two independent datasets: dorsolateral prefrontal cortex (N = 24) from ROSMAP3 and superior frontal gyrus (N = 6) from GEO4.ResultOnly 10 of 843 (1.2%) genes overlap between the differential RNA expression and velocity analyses, suggesting substantial AD‐pathology related differences between these two RNA descriptors. The genes with only velocity differences relate to cell developmental and synaptic processes. Conversely, the genes with only differential expression are majorly associated with mitochondrial activity and ribosomal processes. Many genes were reproduced in the independent datasets; these overlapping genes are again associated with neural development and synaptic activities across many cell types, as well as vascular‐ and immune‐related processes in astrocytes and microglia, respectivelyConclusionWe use RNA velocity to characterize, for the first time to our knowledge, the dynamical multicellular processes underlying neuropathological AD progression. The results support the validity of the novel RNA‐vel concept for achieving a complementary molecular characterization of AD, which may be obscured by typical analysis of RNA abundance alone.

The association of epigenetic clocks in brain tissue with brain pathologies and common aging phenotypes

Epigenetic clocks are calculated by combining DNA methylation states across select CpG sites to estimate biologic age, and have been noted as the most successful markers of biologic aging to date. Yet, limited research has considered epigenetic clocks calculated in brain tissue. We used DNA methylation states in dorsolateral prefrontal cortex specimens from 721 older participants of the Religious Orders Study and Rush Memory and Aging Project, to calculate DNA methylation age using four established epigenetic clocks: Hannum, Horvath, PhenoAge, GrimAge, and a new Cortical clock. The four established clocks were trained in blood samples (Hannum, PhenoAge, GrimAge) or using 51 human tissue and cell types (Horvath); the recent Cortical clock is the first trained in postmortem cortical tissue. Participants were recruited beginning in 1994 (Religious Orders Study) and 1997 (Memory and Aging Project), and followed annually with questionnaires and clinical evaluations; brain specimens were obtained for 80–90% of participants. Mean age at death was 88.0 (SD 6.7) years. We used linear regression, logistic regression, and linear mixed models, to examine relations of epigenetic clock ages to neuropathologic and clinical aging phenotypes, controlling for chronologic age, sex, education, and depressive symptomatology.Hannum, Horvath, PhenoAge and Cortical clock ages were related to pathologic diagnosis of Alzheimer's disease (AD), as well as to Aβ load (a hallmark pathology of Alzheimer's disease). However, associations were substantially stronger for the Cortical than other clocks; for example, each standard deviation (SD) increase in Hannum, Horvath, and PhenoAge clock age was related to approximately 30% greater likelihood of pathologic AD (all p < 0.05), while each SD increase in Cortical age was related to 90% greater likelihood of pathologic AD (odds ratio = 1.91, 95% confidence interval 1.38, 2.62). Moreover, Cortical age was significantly related to other AD pathology (eg, mean tau tangle density, p = 0.003), and to odds of neocortical Lewy body pathology (for each SD increase in Cortical age, odds ratio = 2.00, 95% confidence 1.27, 3.17), although no clocks were related to cerebrovascular neuropathology. Cortical age was the only epigenetic clock significantly associated with the clinical phenotypes examined, from dementia to cognitive decline (5 specific cognitive systems, and a global cognitive measure averaging 17 tasks) to Parkinsonian signs. Overall, our findings provide evidence of the critical necessity for bespoke clocks of brain aging for advancing research to understand, and eventually prevent, neurodegenerative diseases of aging.

Brain Insulin Signaling, Alzheimer Disease Pathology, and Cognitive Function

To examine associations of molecular markers of brain insulin signaling with Alzheimer disease (AD) and cognition among older persons with or without diabetes. This clinical-pathologic study was derived from a community-based cohort study, the Religious Orders Study. We studied 150 individuals (mean age at death =87 years, 48% women): 75 with and 75 without diabetes (matched by sex on age at death and education). Using enzyme-linked immunosorbent assay, immunohistochemistry, and ex vivo stimulation of brain tissue with insulin, we assessed insulin signaling in the postmortem middle frontal gyrus cortex. Postmortem data documented AD neuropathology. Clinical evaluations documented cognitive function proximate to death, based on 17 neuropsychological tests. In adjusted regression analyses, we examined associations of brain insulin signaling with diabetes, AD, and level of cognition. Brain insulin receptor substrate-1 (IRS1) phosphorylation (pS307 IRS1/total IRS1) and serine/threonine-protein kinase (AKT) phosphorylation (pT308 AKT1/total AKT1) were similar in persons with or without diabetes. AKT phosphorylation was associated with the global AD pathology score (p = 0.001). In contrast, IRS1 phosphorylation was not associated with AD (p = 0.536). No other associations of insulin signaling were found with the global AD score, including when using the ex vivo brain insulin stimulation method. In secondary analyses, normalized pT308 AKT1 was positively correlated with both the amyloid burden and tau tangle density, and no other associations of brain insulin signaling with neuropathology were observed. Moreover, normalized pT308 AKT1 was associated with a lower level of global cognitive function (estimate = -0.212, standard error = 0.097; p = 0.031). Brain AKT phosphorylation, a critical node in the signaling of insulin and other growth factors, is associated with AD neuropathology and lower cognitive function. ANN NEUROL 2020;88:513-525.

Hospitalization, Alzheimer's Disease and Related Neuropathologies, and Cognitive Decline

ObjectiveTo test the hypothesis that Alzheimer's disease and related neuropathologies contribute to the association between hospitalization and cognitive decline in old age.MethodsAs part of a longitudinal clinical–pathologic cohort study, 526 older persons (mean age at death = 90.9 years, 71% female) without dementia at baseline completed annual cognitive testing and were autopsied at death. Hospitalization information was obtained from linked Medicare claims records. Neuropathologic examination assessed β‐amyloid burden, tau tangle density, neocortical Lewy bodies, hippocampal sclerosis, chronic gross and microscopic cerebral infarcts, and transactive response DNA binding protein 43 kDa.ResultsOver a mean of 5.1 years, a total of 1,383 hospitalizations occurred, and the mean annual rate of hospitalization was 0.5 (standard deviation = 0.6, median = 0.4). Higher rate of hospitalization was not directly related to higher burden for any of the neuropathologic markers. Higher rate of hospitalization was associated with more rapid cognitive decline (estimate = −0.042, standard error [SE] = 0.012, p < 0.001), and after controlling for all 7 neuropathologic markers, the association was essentially the same (estimate = −0.040, SE = 0.013, p = 0.002). In a multivariable model with 3‐way interactions of neuropathologic markers with hospitalization rate and time, the association between hospitalization rate and faster cognitive decline was greater in persons with more tangle pathology (estimate for interaction = −0.007, SE = 0.002, p = 0.002) and in persons with neocortical Lewy bodies (estimate for interaction = −0.117, SE = 0.042, p = 0.005).InterpretationOlder persons with more hospitalizations experienced faster rates of cognitive decline, and this association was more pronounced in persons with more tau tangle density and with neocortical Lewy body pathologies. ANN NEUROL 2019;86:844–852

Genetic risk for Alzheimer\u2019s dementia predicts motor deficits through multi-omic systems in older adults

Alzheimer’s disease manifests with both cognitive and motor deficits. However, the degree to which genetic risk of Alzheimer’s dementia contributes to late-life motor impairment, and the specific molecular systems underlying these associations, are uncertain. Here, we adopted an integrative multi-omic approach to assess genetic influence on motor impairment in older adults and identified key molecular pathways that may mediate this risk. We built a polygenic risk score for clinical diagnosis of Alzheimer’s dementia (AD-PRS) and examined its relationship to several motor phenotypes in 1885 older individuals from two longitudinal aging cohorts. We found that AD-PRS was associated with a previously validated composite motor scores and their components. The major genetic risk factor for sporadic Alzheimer’s dementia, the APOE/TOMM40 locus, was not a major driver of these associations. To identify specific molecular features that potentially medicate the genetic risk into motor dysfunction, we examined brain multi-omics, including transcriptome, DNA methylation, histone acetylation (H3K9AC), and targeted proteomics, as well as diverse neuropathologies. We found that a small number of factors account for the majority of the influence of AD-PRS on motor function, which comprises paired helical filament tau-tangle density, H3K9AC in specific chromosomal regions encoding genes involved in neuromuscular process. These multi-omic factors have the potential to elucidate key molecular mechanisms developing motor impairment in the context of Alzheimer’s dementia.

Association of Cortical β-Amyloid Protein in the Absence of Insoluble Deposits With Alzheimer Disease

β-Amyloid deposits are a pathologic hallmark of Alzheimer disease (AD). However, the extent to which cortical β-amyloid protein in the absence of insoluble deposits is associated with classic features of AD appear to be unknown. To examine the associations of cortical β-amyloid protein in the absence of insoluble deposits with cognitive decline, neurofibrillary tangles, other age-associated neuropathologic conditions, and APOE. This analysis combines data from 2 community-based clinicopathologic cohort studies of aging. The Religious Orders Study started in 1994, and the Rush Memory and Aging Project started in 1997. Both studies are ongoing. Participants without known dementia were enrolled and agreed to annual clinical evaluations and brain donation after death. Primary analyses focused on individuals without β-amyloid deposits. Data analyses occurred in mid-September 2018. β-Amyloid protein abundance was measured by targeted proteomics using selected reaction monitoring. β-Amyloid deposits were detected using immunohistochemistry. Other neuropathologic indices were quantified via uniform structured evaluation. Linear mixed models were used to examine the association of β-amyloid protein with cognitive decline. Regression models examined the protein associations with neuropathologic outcomes and the APOE genotype. By mid-September 2018, 3575 older persons were enrolled, and 1559 had died and undergone brain autopsy. Proteomic data were collected in 1208 individuals, and 5 with missing cognitive scores were excluded. Of the remaining 1203, primary analyses focused on 148 individuals (12.3%) without β-amyloid deposits. In this group, the mean (SD) age at death was 87.0 (7.0) years, and 84 individuals (56.8%) were women. In the absence of β-amyloid deposits, we did not observe an association of β-amyloid protein with decline in episodic memory, but the protein was associated with faster rates of decline in processing speed (mean [SE] change, -0.014 [0.005]; P = .008) and visuospatial abilities (mean [SE] change, -0.013 [0.005]; P = .006). We did not observe protein association with paired helical filament tau tangle density. The protein was associated with amyloid angiopathy (odds ratio, 1.38 [95% CI, 1.15-1.67]; P < .001) but no other brain pathology. The associations with cognitive decline were unchanged after controlling for amyloid angiopathy. Neither APOE ε4 nor a polygenic Alzheimer risk score was associated with β-amyloid protein. Cortical β-amyloid protein was associated with faster cognitive decline in the absence of β-amyloid deposits, which supports the role of cortical soluble β-amyloid as a neurotoxic agent in aging. The lack of protein association with paired helical filament tau tangles, episodic memory decline, or strong genetic drivers of deposited β-amyloid suggests an underlying neuropathologic change that may differ from that of AD.

Sex differences in Alzheimer's disease and common neuropathologies of aging.

Alzheimer's dementia is significantly more common in women than in men. However, few pathological studies have addressed sex difference in Alzheimer's disease (AD) and other brain pathologies. We leveraged postmortem data from 1453 persons who participated in one of two longitudinal community-based studies of older adults, the Religious Orders Study and the Rush Memory and Aging Project. Postmortem examination identified AD pathologies, neocortical Lewy bodies, DNA-binding protein 43 (TDP-43), hippocampal sclerosis, gross and micro infarcts, atherosclerosis, arteriolosclerosis, and cerebral amyloid angiopathy. Linear and logistic regressions examined the association of sex with each of the pathologic measures. Two-thirds of subjects were women (n = 971; 67%), with a mean age at death of 89.8 (SD = 6.6) years in women and 87.3 (SD = 6.6) in men. Adjusted for age and education, women had higher levels on a global measure of AD pathology (estimate = 0.102, SE = 0.022, p < 0.001), and tau tangle density in particular (estimate = 0.334, SE = 0.074, p < 0.001), and there was a borderline difference between women and men in amyloid-β load (estimate = 0.124, SE = 0.065, p = 0.056). In addition, compared to men, women were more likely to have more severe arteriolosclerosis (OR = 1.28, 95% CI:1.04-1.58, p = 0.018), and less likely to have gross infarcts (OR = 0.78, 95% CI:0.61-0.98, p = 0.037), although the association with gross infarct was attenuated after controlling for vascular risk factors. These data help elucidate the neuropathologic footprint of sex difference in AD and other common brain pathologies of aging.

Changes in the detergent-insoluble brain proteome linked to amyloid and tau in Alzheimer's Disease progression.

Despite a key role of amyloid-beta (Aβ) in Alzheimer's disease (AD), mechanisms that link Aβ plaques to tau neurofibrillary tangles and cognitive decline still remain poorly understood. The purpose of this study was to quantify proteins in the sarkosyl-insoluble brain proteome correlated with Aβ and tau insolubility in the asymptomatic phase of AD (AsymAD) and through mild cognitive impairment (MCI) and symptomatic AD. Employing label-free mass spectrometry-based proteomics, we quantified 2711 sarkosyl-insoluble proteins across the prefrontal cortex from 35 individual cases representing control, AsymAD, MCI and AD. Significant enrichment of Aβ and tau in AD was observed, which correlated with neuropathological measurements of plaque and tau tangle density, respectively. Pairwise correlation coefficients were also determined for all quantified proteins to Aβ and tau, across the 35 cases. Notably, six of the ten most correlated proteins to Aβ were U1 small nuclear ribonucleoproteins (U1 snRNPs). Three of these U1 snRNPs (U1A, SmD and U1-70K) also correlated with tau consistent with their association with tangle pathology in AD. Thus, proteins that cross-correlate with both Aβ and tau, including specific U1 snRNPs, may have potential mechanistic roles in linking Aβ plaques to tau tangle pathology during AD progression.

A TREM1 variant alters the accumulation of Alzheimer-related amyloid pathology.

Genome-wide association studies have linked variants in TREM2 (triggering receptor expressed on myeloid cells 2) and TREML2 with Alzheimer disease (AD) and AD endophenotypes. Here, we pursue a targeted analysis of the TREM locus in relation to cognitive decline and pathological features of AD. Clinical, cognitive, and neuropathological phenotypes were collected in 3 prospective cohorts on aging (n = 3,421 subjects). Our primary analysis was an association with neuritic plaque pathology. To functionally characterize the associated variants, we used flow cytometry to measure TREM1 expression on monocytes. We provide evidence that an intronic variant, rs6910730(G) , in TREM1, is associated with an increased burden of neuritic plaques (p = 3.7 × 10(-4) ), diffuse plaques (p = 4.1 × 10(-3) ), and Aβ density (p = 2.6 × 10(-3) ) as well as an increased rate of cognitive decline (p = 5.3 × 10(-3) ). A variant upstream of TREM2, rs7759295(C) , is independently associated with an increased tau tangle density (p = 4.9 × 10(-4) ), an increased burden of neurofibrillary tangles (p = 9.1 × 10(-3) ), and an increased rate of cognitive decline (p = 2.3 × 10(-3) ). Finally, a cytometric analysis shows that the TREM1 rs6910730(G) allele is associated with decreased TREM1 expression on the surface of myeloid cells (p = 1.7 × 10(-3) ). We provide evidence that 2 common variants within the TREM locus are associated with pathological features of AD and aging-related cognitive decline. Our evidence suggests that these variants are likely to be independent of known AD variants and that they may work through an alteration of myeloid cell function.

Association of Brain DNA methylation in SORL1, ABCA7, HLA-DRB5, SLC24A4, and BIN1 with pathological diagnosis of Alzheimer disease.

Recent large-scale genome-wide association studies have discovered several genetic variants associated with Alzheimer disease (AD); however, the extent to which DNA methylation in these AD loci contributes to the disease susceptibility remains unknown. To examine the association of brain DNA methylation in 28 reported AD loci with AD pathologies. Ongoing community-based clinical pathological cohort studies of aging and dementia (the Religious Orders Study and the Rush Memory and Aging Project) among 740 autopsied participants 66.0 to 108.3 years old. DNA methylation levels at individual CpG sites generated from dorsolateral prefrontal cortex tissue using a bead assay. Pathological diagnosis of AD by National Institute on Aging-Reagan criteria following a standard postmortem examination. Overall, 447 participants (60.4%) met the criteria for pathological diagnosis of AD. Brain DNA methylation in SORL1, ABCA7, HLA-DRB5, SLC24A4, and BIN1 was associated with pathological AD. The association was robustly retained after replacing the binary trait of pathological AD with 2 quantitative and molecular specific hallmarks of AD, namely, Aβ load and paired helical filament tau tangle density. Furthermore, RNA expression of transcripts of SORL1 and ABCA7 was associated with paired helical filament tau tangle density, and the expression of BIN1 was associated with Aβ load. Brain DNA methylation in multiple AD loci is associated with AD pathologies. The results provide further evidence that disruption of DNA methylation is involved in the pathological process of AD.

Clinical-pathologic study of depressive symptoms and cognitive decline in old age.

To clarify the relationship between depressive symptoms and the clinical and neuropathologic manifestations of dementia. In a clinical-pathologic cohort study, 1,764 older persons without cognitive impairment at enrollment completed annual clinical evaluations for a mean of 7.8 years. The evaluations included assessment of depressive symptoms (10-item Center for Epidemiological Studies Depression Scale) and cognitive function (battery of 17 performance tests). A total of 582 individuals died during follow-up and underwent a uniform neuropathologic examination to quantify β-amyloid plaques and tau tangle density in multiple brain regions and identify neocortical Lewy bodies, hippocampal sclerosis, and gross and microscopic cerebral infarcts. Level of depressive symptoms slightly increased during follow-up. Incident mild cognitive impairment (52.2%) was associated with higher level of depressive symptoms before the diagnosis but not with change in symptoms after the diagnosis; incident dementia (17.9%) was associated with higher symptom level before dementia onset and with more rapid decline in symptoms after dementia onset. None of the neuropathologic markers was related to level of depressive symptoms or change in symptoms over time. In a mixed-effects model adjusted for the neuropathologic markers, higher level of depressive symptoms averaged over evaluations was associated with more rapid global cognitive decline, accounting for 4.4% of the variability in decline not attributable to the neuropathologic markers. Depressive symptoms did not modify the association of the neuropathologic markers with cognitive decline. In old age, depressive symptoms have an association with cognitive decline that is independent of the neuropathologic hallmarks of dementia.

Molecular and Cellular Mechanism of Okadaic Acid (OKA)-Induced Neurotoxicity: A Novel Tool for Alzheimer’s Disease Therapeutic Application

Okadaic acid (OKA), a polyether C38 fatty acid toxin extracted from a black sponge Hallichondria okadaii, is a potent and selective inhibitor of protein phosphatase, PP1 and PP2A. OKA has been proved to be a powerful probe for studying the various regulatory mechanisms and neurotoxicity. Because of its property to inhibit phosphatase activity, OKA is associated with protein phosphorylation; it is implicated in hyperphosphorylation of tau and in later stages causes Alzhiemer's disease (AD)-like pathology. AD is a progressive neurodegenerative disorder, pathologically characterized by extracellular amyloid beta (Aβ) plaques and intracellular neurofibrillary tangles (NFTs). The density of tau tangles in AD pathology is associated with cognitive dysfunction. Recent studies have highlighted the importance of serine/threonine protein phosphatases in many processes including apoptosis and neurotoxicity. Although OKA causes neurotoxicity by various pathways, the exact mechanism is still not clear. The activation of major kinases, such as Ser/Thr, MAPK, ERK, PKA, JNK, PKC, CaMKII, Calpain, and GSK3β, in neurons is associated with AD pathology. These kinases, associated with abnormal hyperphosphorylation of tau, suggest that the cascade of these kinases could exclusively be involved in the pathogenesis of AD. The activity of serine/threonine protein phosphatases needs extensive study as these enzymes are potential targets for novel therapeutics with applications in many diseases including cancer, inflammatory diseases, and neurodegeneration. There is a need to pay ample attention on MAPK kinase pathways in AD, and OKA can be a better tool to study cellular and molecular mechanism for AD pathology. This review elucidates the regulatory mechanism of PP2A and MAPK kinase and their possible mechanisms involved in OKA-induced apoptosis, neurotoxicity, and AD-like pathology.