P-tau Levels Research Articles

Plasma p‐tau forms as potential diagnostic biomarkers for Alzheimer’s disease

AbstractBackgroundAccumulation of tau aggregates is a pathological hallmark of Alzheimer’s disease (AD) that is closely related to the emergence of neurodegeneration and manifestation of clinical symptoms. Currently, CSF and plasma biomarkers of tau pathology, which would improve the diagnostic process in everyday clinical practice and facilitate the classification of patients for clinical trials, are the focus of research. Biomarkers of tau pathology correlate with post‐mortem AD pathology. Furthermore, they allow for differentiation of AD from other types of dementia, and prediction of future progression from normal cognition and mild cognitive impairment to AD. The availability of The clinical utility of novel assays for the detection of several isoforms of tau pathophysiology in the blood, which are currently available, requires verification. Therefore, the aim of the present study was evaluation of tau proteins in the blood of AD patients and non‐demented controls, and assessment of their diagnostic utility.MethodPlasma concentrations of pTau181 and pTau231 were assessed using a Single molecule array (Simoa). CSF biomarkers, including Aβ‐42, Aβ‐42/Aβ‐40, tau and pTau181 were evaluated in 20 AD patients and 18 elderly subjects without cognitive deficits by ELISA technique.ResultStatistically significantly higher blood levels of pTau181 and pTau231 were observed in AD patients in comparison to cognitively normal individuals. Increased concentration of pTau231 correlated with age and MMSE. Furthermore, the associations between the levels of plasma pTau231 and plasma pTau181, CSF Tau and pTau181, as well as Aβ‐42 were observed in the whole study group.ConclusionThe results indicate that plasma P‐tau181 and P‐tau231 may be diagnostic biomarkers that can help to predict cognitive decline and that they hold promise for use in routine clinical practice.

Plasma biomarkers of Alzheimer’s disease in dementia with Lewy bodies

AbstractBackgroundAlzheimer’s disease (AD) co‐pathology is a common feature in dementia with Lewy bodies (DLB) and associated with a more rapid decline. Here, we aimed to evaluate plasma biomarkers as alternatives for CSF biomarkers for the detection of amyloid pathology, and for their diagnostic and prognostic value in DLB.MethodPlasma Aβ42/40, GFAP, NfL, pTau181 and pTau231, were measured by SIMOA in patients with DLB (n = 342), AD (n = 131), and healthy controls (n = 89) from the E‐DLB consortium cohort. Associations of biomarkers with CSF Aβ42 status were assessed with ANCOVA corrected for age and sex. ROC analyses were performed to assess biomarker’s performance for amyloid detection and differential diagnosis. Associations of biomarkers with cognitive impairment and decline were determined by linear regression and mixed effects models.ResultAltered Aβ42/40 (β = ‐0.0076, 95%CI:‐0.0137 to ‐0.0016, p<.05), pTau181 (β = 0.2503, 95%CI: 0.0555 to 0.4451, p<.05) and pTau231 levels (β = 0.2269, 95%CI:0.0347 to 0.4191, p<.05) were associated with amyloid pathology in DLB, as assessed by CSF Aβ42. The combination of these biomarkers differentiated amyloid normal from abnormal DLB patients with an AUC of 0.728 (sensitivity = 64.6%, specificity = 75.0%). pTau181 best differentiated these groups as a single marker (AUC = 0.700, sensitivity = 62.5%, specificity = 73.1%). The combination of Aβ42/40, NfL and pTau231 differentiated DLB from AD with an AUC of 0.726 (sensitivity = 73.3%, specificity = 68.8%). In DLB, increased GFAP (β = ‐8.9, 95%CI:‐11.7 to ‐6.1, p<.001), NfL (β = ‐7.2, 95%CI:‐10.0 to ‐4.4, p<.001), pTau181 (β = ‐2.6, 95%CI:‐4.0 to ‐1.2, p<.001) and pTau231 (β = ‐2.4, 95%CI:‐3.7 to ‐1.2, p<.001) were associated with lower baseline MMSE scores and increased GFAP (annual change of ‐2.1 MMSE points (95%CI:‐2.9 to ‐1.3, p<.001) and NfL (annual change of ‐2.1 MMSE points (95%CI:‐3.0 to ‐1.3, p<.001) predicted faster cognitive decline.ConclusionPlasma Aβ42/40, pTau181 and pTau231 were associated with amyloid abnormality in DLB. Their utility for differential diagnosis and identifying amyloid pathology in DLB was modest. Our findings suggest a prognostic value of GFAP and NfL for cognitive decline in DLB.

The AppNL‐G‐F/MAPT mouse model of Alzheimer’s Disease demonstrates increased levels of ptau217 in CSF, changes that correlate with increased cerebral p‐tau depositions

AbstractBackgroundCerebrospinal fluid (CSF) biomarkers reflecting the neuropathological hallmarks of Alzheimer’s disease (AD) have during the two last decades been developed and are commonly used to diagnose patients with AD patients. Previous studies have shown that CSF p‐tau217 particularly well can separate AD patients from healthy controls and that CSF levels of ptau217 correlate significantly with the amyloid burden and tau pathology in the brain (determined by PET). However, more studies are needed to fully understand the temporal relationship between CSF p‐tau217 changes and the accumulation tau in the brain. In this current study, we aim to investigate these temporal associations by the use of a novel knock‐in mouse model, AppNL‐G‐F expressing all six isoforms of human MAPT.MethodCerebrospinal fluid (CSF) and brain tissue will be collected from 3‐22 months old AppNL‐G‐F /MAPT and MAPT knock‐in mice. A pilot study of a subset of mice at different ages has been performed where levels of CSF ptau217 were analyzed using Mesoscale Discovery developed by Eli Lilly and Company. Mouse brain sections were immunostained against Aß and ptau181/217/231 to determine the cerebral p‐tau distribution.ResultIn CSF from our AppNL‐G‐F /MAPT double knock‐in (dKi) mouse model, we found age‐related increases in ptau217 levels compared to MAPT Ki mice. These changes in CSF ptau217 were associated with an increase of cerebral accumulation of p‐tau positive inclusions in the cortex and hippocampus of these mice. Additionally, we also found temporal differences in co‐localization between Aß plaques and the investigated phosphorylation sites of tau.ConclusionOur preliminary results from the AppNL‐G‐F/MAPT double knock‐in model, show early alterations in CSF ptau217 levels, changes that correlate in time with cerebral p‐tau positive accumulation as well as formation of Aß plaques. These findings indicate that alterations in CSF and cerebral p‐tau occurs early in the disease, when Aß pathology is widespread but no tau tangles are present. Furthermore, our preliminary data suggest temporal differences in phosphorylation sites of tau associated with Aß pathology. Additional CSF analysis and immunostainings will be performed before the AAIC conference.

Sex‐specific CSF proteomic profiling of amyloid/tau positivity identifies distinctive sex‐specific alternation of multiple proteins involved in Alzheimer’s disease

AbstractBackgroundSporadic Alzheimer’s disease (AD) is a highly heterogeneous multifactorial disease in which females have a higher risk. Among 5.3 million senior Americans diagnosed with AD, over 60% are female. Despite the well‐established sex differences, sex‐specific molecular findings in AD are still limited. We therefore examined the role of sex in the proteomic alterations due to AD to elucidate potential protein markers of AD heterogeneity.MethodIn the discovery cohort, 599 preclinical AD and 435 controls underwent lumbar puncture. Over 7,000 proteins in cerebrospinal fluid (CSF) were measured using SomaLogic assay. Amyloid/tau positivity (AT classification) was determined using ELISA Aβ42 and pTau181 levels in CSF. Proteins with sex‐specific effects were identified through linear models focusing on the interaction term between AT classification and sex. Results were tested in the independent cohort (N = 732) using the identical approaches. We analyzed brain proteomics and transcriptomics data to validate the replicated sex‐specific proteins. We performed pathway enrichment, interaction network using ConsensusPathDB and drug‐target prediction.ResultWe identified 594 proteins with sex‐specific effects in discovery (P<0.05 and permutation FDR <0.05). Among them, 36 were validated in replication (P<0.05 and consistent direction). These proteins were found to be involved in neurologic disorders and highly enriched in axon regeneration (fold enrichment = 9.38 and FDR = 2.8×10−4). Among the 36 proteins identified, 13 were classified as female‐specific and 23 as male‐specific. These 36 proteins strongly predicted amyloid/tau positivity (AUC = 0.926) for all individuals as well as 13 female‐specific proteins for females (AUC = 0.929). The interaction network identified CCN2 as a hub and contained 10 additional proteins including JAG1 and DLL4 of Notch signaling pathway and CTSB, an amyloid precursor protein secretase, among others. The results of 36 proteins in brain proteomics and transcriptomics confirmed the sex‐specific effect of CCN2 and others on AD in different tissues. Drug target prediction suggests minocycline and etoposide as potential treatments for females as well amitriptyline and verteporfin for males.ConclusionWe robustly identified 36 proteins that showed significant sex‐specific alterations by preclinical AD. Several proteins involved in AD and neurodegeneration were highlighted. Our findings facilitate mechanistic understanding of sex differences for AD risk and progression.

Developing Topics.

Nitric oxide/cGMP/CREB signaling is critical for learning and memory processes and is disturbed by Abeta amyoid and in Alzheimer's disease. AR1001 is an inhibitor of phosphodiesterase (PDE)-5, which degrades specifically cGMP, thus having a potential to reverse AD pathology. For the in vivo study, AR1001 was intraperitoneally administered (4 mg/kg/day) to APP-C105 mice for 4 weeks. Then after behavioral tests (Morris-water maze and passive avoidance tests) were done, hippocampal levels of Abeta1-42 and p-Tau (S199/202) were determined. In the in vitro study using human neuroblastoma SH-SY5Y cells and mouse hippocampal HT-22 cells, the effects of AR1001 on Abeta1-42-induced cytotoxicity and intracellular signaling were examined. AR1001 markedly improved cognitive functions in both Morris-water maze and passive avoidance tests and reduced hippocampal Abeta1-42 and p-Tau levels in the APP-C105 mice. In the in vitro experiments, AR1001 inhibited Abeta1-42-induced cell death, mitochondrial membrane potential derangement, and apoptotic markers (cleaved caspase-3 and cleaved PPAR) concentration-dependently. AR1001 reversed Abeta1-42-induced decrease in phosphorylated CREB (p-CREB), and NGF/BDNF expression. Further, AR1001 blocked Abeta1-42-induced pSer9-GSK3beta decrease and p25/p35 increase. Interestingly, compared with sildenafil, vardenafil and tadalafil, AR1001 was more effective in inhibiting glucocorticoid receptor (GR) dimerization and Wnt antagonist Dickkopf-1 (Dkk-1) expression, and in enhancing Wnt3a expression. AR1001 had protective effects both in vivo and in vitro models of AD. Furthermore, AR1001 showed more pronounced activity in the modulation of GR and Wnt signaling among the various PDE-5 inhibitors. It is suggested that the multimodal activity of AR1001 contributes to the therapeutic effects of AR1001 observed in the phase 2 clinical trial in AD patients (NCT03625622).

Sex‐associated differences in plasma and cerebrospinal fluid biomarkers in Early‐onset Alzheimer’s disease

AbstractBackgroundFemale sex is associated with greater atrophy, amyloid and tau burden in Early‐onset Alzheimer’s Disease (EOAD) in the Longitudinal EOAD Study (LEADS). APOE‐ε4 non‐carrier‐status was found to be a further predictor of EOAD pathology. We expanded the analyses by examining the impact of sex and APOE‐ε4 on plasma and cerebrospinal fluid (CSF) biomarkers of AD. Plasma markers included: neurofilament light chain (NfL), plasma glial fibrillary acidic protein (GFAP), Aβ 42/40, and pTau231. CSF markers included: Aβ 42/40, neurogranin, tTau, pTau181, synaptosomal‐associated protein‐25 (SNAP25), YKL‐40, and visinin‐like protein‐1 (VILIP1).MethodWe included 201 amyloid‐positive EOAD, 64 amyloid‐negative Early‐onset cognitively impaired (EOnonAD), and 86 Cognitively Normal (CN) LEADS participants with plasma biomarker data. Of these 100 EOAD, 35 EOnonAD, and 38 CN participants also had CSF data. Participants were stratified by sex and APOE‐ε4 genotype. Demographics (age, education, APOE‐ε4, MMSE) and biomarker differences were compared using ANOVA within each diagnostic group. ANCOVAs were run to control for the effects of age and education on biomarkers.ResultCompared to men, EOAD women showed greater levels of plasma NfL (p = .03), and GFAP (p<.001) while Aβ 42/40, and pTau231 were comparable. In CSF, EOAD women showed higher levels of neurogranin (p = .01), tTau (p = .01), pTau181 (p = .01) and VILIP1 (p = .02). EOnonAD women showed significantly greater plasma GFAP levels (p = .02). In the CN cohort, women had greater CSF SNAP25 levels (p = .03) while men showed a trend for higher plasma pTau231 levels (p = .05). APOE‐ε4 carrier‐status was not associated with differences in levels of plasma or CSF biomarkers in either sex.ConclusionAs highly selective and specific AD fluid biomarkers emerge, understanding sex‐based differences in CSF and plasma is imperative. Female sex is associated with higher levels of neurodegeneration (NfL, tTau, pTau181, neurogranin, VILIP1) in EOAD and astrogliosis (GFAP) in both EOAD and EOnonAD.This data supports our previous findings that greater pathology burden is associated with female sex. This paves the way for further examination of sex and APOE‐ε4 genotype‐based differences in imaging and fluid biomarkers, their associations, and utility in early diagnosis.

Plasma biomarkers of Alzheimer´s disease in the continuum of dementia with Lewy bodies

AbstractBackgroundPatients with dementia with Lewy bodies (DLB) may have Alzheimer´s disease (AD) pathology. Plasma biomarkers of beta‐amyloid (Aβ), phosphorylated tau (pTau), and neurodegeneration are sensitive to AD neuropathologic changes in AD dementia. While these plasma biomarkers are well tested in the AD continuum, their performance for concomitant AD pathology in the DLB continuum is still unclear.MethodWe included patients with isolated REM sleep behavior disorder (iRBD; n = 15), with mild cognitive impairment with Lewy bodies (MCI‐LB; n = 37), and with DLB (n = 70) from the Mayo Clinic Alzheimer’s Disease Research Center. Cognitively unimpaired individuals (CU; n = 100) included from the Mayo Clinic Study of Aging were balanced on age and sex. A panel of plasma biomarkers of Aβ40, Aβ42, p‐tau181, neurofilament light chain (NfL), and glial fibrillary acidic protein (GFAP) measures was obtained. We calculated the ratio of plasma Aβ40/42. Lower Aβ40/42 indicates increased Aβ pathology. Plasma Aβ40, Aβ42, GFAP, and NfL were measured using the Simoa® Neurology 4‐Plex E Advantage kit and pTau‐181 was measured with the Simoa® pTau‐181 Advantage V2 kit. Both were run on a Quanterix HD‐X analyzer. AD imaging biomarkers were assessed on PET using Pittsburgh compound B (PiB) for Aβ and 18F‐Flortaucipir for tau.ResultHigher levels of plasma GFAP were observed in the MCI‐LB (p = 0.014) and DLB (p<0.001) groups compared to CU (Figure). DLB patients also showed higher levels of plasma pTau181 (p<0.001) and NfL (p<0.001). Higher amyloid and tau PET standardized uptake value ratio (SUVr) in the DLB continuum were associated with higher levels of plasma p‐tau181, NfL, and GFAP (p<0.001). After accounting for age, plasma Aβ40/42 did not correlate with amyloid or tau PET SUVr.ConclusionIn the DLB continuum, abnormal levels of GFAP in plasma can be detected as early as the prodromal stages of the disease. Plasma pTau181 reached abnormal levels in the DLB stage. Higher plasma GFAP, NfL, and p‐tau181 are associated with higher amyloid and tau PET SUVr in the DLB continuum. Plasma biomarkers have the potential to contribute to screening and early diagnosis in the DLB continuum, which has implications in designing new treatments.

Sex‐associated differences in plasma and cerebrospinal fluid biomarkers in Early‐onset Alzheimer’s disease

AbstractBackgroundFemale sex is associated with greater atrophy, amyloid and tau burden in Early‐onset Alzheimer’s Disease (EOAD) in the Longitudinal EOAD Study (LEADS). APOE‐e4 non‐carrier‐status was found to be a further predictor of EOAD pathology. We expanded the analyses by examining the impact of sex and APOE‐e4 on plasma and cerebrospinal fluid (CSF) biomarkers of AD. Plasma markers included: neurofilament light chain (NfL), plasma glial fibrillary acidic protein (GFAP), Aß 42/40, and pTau231. CSF markers included: Aß 42/40, neurogranin, tTau, pTau181, synaptosomal‐associated protein‐25 (SNAP25), YKL‐40, and visinin‐like protein‐1 (VILIP1).MethodWe included 201 amyloid‐positive EOAD, 64 amyloid‐negative Early‐onset cognitively impaired (EOnonAD), and 86 Cognitively Normal (CN) LEADS participants with plasma biomarker data. Of these 100 EOAD, 35 EOnonAD, and 38 CN participants also had CSF data. Participants were stratified by sex and APOE‐e4 genotype. Demographics (age, education, APOE‐e4, MMSE) and biomarker differences were compared using ANOVA within each diagnostic group. ANCOVAs were run to control for the effects of age and education on biomarkers.ResultCompared to men, EOAD women showed greater levels of plasma NfL (p = .03), and GFAP (p<.001) while Aß 42/40, and pTau231 were comparable. In CSF, EOAD women showed higher levels of neurogranin (p = .01), tTau (p = .01), pTau181 (p = .01) and VILIP1 (p = .02). EOnonAD women showed significantly greater plasma GFAP levels (p = .02). In the CN cohort, women had greater CSF SNAP25 levels (p = .03) while men showed a trend for higher plasma pTau231 levels (p = .05). APOE‐e4 carrier‐status was not associated with differences in levels of plasma or CSF biomarkers in either sex.ConclusionAs highly selective and specific AD fluid biomarkers emerge, understanding sex‐based differences in CSF and plasma is imperative. Female sex is associated with higher levels of neurodegeneration (NfL, tTau, pTau181, neurogranin, VILIP1) in EOAD and astrogliosis (GFAP) in both EOAD and EOnonAD. This data supports our previous findings that greater pathology burden is associated with female sex. This paves the way for further examination of sex and APOE‐e4 genotype‐based differences in imaging and fluid biomarkers, their associations, and utility in early diagnosis.

Diagnostic of Novel Plasma Biomarkers in Controls, SCD and MCI Subjects

AbstractBackgroundAlzheimer’s disease (AD) is the most common cause of dementia, and a challenging disease for the development of plasma biomarkers. Blood samples are the most easily collectable samples for medical diagnosis. This study evaluates the potential of plasma biomarkers in identifying early stages of AD.Method189 participants were recruited at the NYU Alzheimer Disease Research Center. This cohort includes n = 75 with normal cognition (NL), n = 77 with subjective cognitive decline (SCD), n = 37 with mild cognitive impairment (MCI). Comprehensive neuropsychological and magnetic resonance imaging evaluations were conducted for all patients. Plasma biomarkers assays (total tau [t‐tau], neurofilament light [NfL], glial fibrillary acid protein [GFAP], ubiquitin carboxyl‐terminal hydrolase L1 [UCH‐L1], Aβ1‐42, Aβ1‐40 and pTau181) were measured using the SIMOA SR‐X, a novel technology that employs highly sensitive immunoassays with a limit of detection (LOD) under 100 fg/ml.ResultThe levels of NfL, t‐Tau, GFAP and UCH‐L1 were measured using the Neurology 4‐plex A. NfL levels showed a significant difference between NL and SCD (one tailed t‐ test p = 0.0459). GFAP showed statistically significant differences between NL and MCI, (one tailed t‐test p = 0.0369). Aβ1‐42 showed a significant difference between SCD and MCI (one tailed t‐test p = 0.0493). pTau181 levels showed a significant difference between NL, SCD and NL, MCI (p = 0.0447 and p = 0.0439, respectively). The ratio of pTau181/Aβ1‐42 shows a significant difference between NL and MCI (one tailed t‐test p = 0.0187). Correlation of these biomarkers with brain imaging and cognitive measures is underway.ConclusionBiomarker levels of NfL, GFAP, Aβ1‐42, pTau181 and Ratio pTau181/Aβ1‐42 in plasma samples showed several significant differences between the three groups of subjects. Plasma biomarkers can be useful for the diagnosis of AD related pathology at early stages.

Plasma biomarkers of Alzheimer´s disease in the continuum of dementia with Lewy bodies

AbstractBackgroundPatients with dementia with Lewy bodies (DLB) may have Alzheimer´s disease (AD) pathology. Plasma biomarkers of beta‐amyloid (Aß), phosphorylated tau (pTau), and neurodegeneration are sensitive to AD neuropathologic changes in AD dementia. While these plasma biomarkers are well tested in the AD continuum, their performance for concomitant AD pathology in the DLB continuum is still unclear.MethodWe included patients with isolated REM sleep behavior disorder (iRBD; n = 15), with mild cognitive impairment with Lewy bodies (MCI‐LB; n = 37), and with DLB (n = 70) from the Mayo Clinic Alzheimer’s Disease Research Center. Cognitively unimpaired individuals (CU; n = 100) included from the Mayo Clinic Study of Aging were balanced on age and sex. A panel of plasma biomarkers of Aß40, Aß42, p‐tau181, neurofilament light chain (NfL), and glial fibrillary acidic protein (GFAP) measures was obtained. We calculated the ratio of plasma Aß40/42. Lower Aß40/42 indicates increased Aß pathology. Plasma Aß40, Aß42, GFAP, and NfL were measured using the Simoa® Neurology 4‐Plex E Advantage kit and pTau‐181 was measured with the Simoa® pTau‐181 Advantage V2 kit. Both were run on a Quanterix HD‐X analyzer. AD imaging biomarkers were assessed on PET using Pittsburgh compound B (PiB) for Aß and 18F‐Flortaucipir for tau.ResultHigher levels of plasma GFAP were observed in the MCI‐LB (p = 0.014) and DLB (p<0.001) groups compared to CU (Figure). DLB patients also showed higher levels of plasma pTau181 (p<0.001) and NfL (p<0.001). Higher amyloid and tau PET standardized uptake value ratio (SUVr) in the DLB continuum were associated with higher levels of plasma p‐tau181, NfL, and GFAP (p<0.001). After accounting for age, plasma Aß40/42 did not correlate with amyloid or tau PET SUVr.ConclusionIn the DLB continuum, abnormal levels of GFAP in plasma can be detected as early as the prodromal stages of the disease. Plasma pTau181 reached abnormal levels in the DLB stage. Higher plasma GFAP, NfL, and p‐tau181 are associated with higher amyloid and tau PET SUVr in the DLB continuum. Plasma biomarkers have the potential to contribute to screening and early diagnosis in the DLB continuum, which has implications in designing new treatments.

Basic Science and Pathogenesis - Part 1.

Neuropathologically, Alzheimer's disease (AD) is characterized by the presence of senile plaques composed of beta-amyloid (Aβ) and neurofibrillary tangles made of hyperphosphorylated tau. Aβ and p-tau have been shown to impact endoplasmic reticulum homeostasis, DNA damage response and autophagic functions. Intriguingly, alterations in these systems have also been connected to dysfunctions in UFMylation, a ubiquitin-like posttranslational modification. Analogous to ubiquitin, UFM1, is conjugated to substrates via a catalytic cascade involving UFM1-specific set of E1 (UBA5), E2 (UFC1), and a complex that consists of E3 ligase (UFL1), DDRGK1 and CDK5RAP3. UFMylation is reversible, and this is mediated by UFSP2. The UFMylation pathway is essential for brain development as complete loss of function of any of its components result in severe neurodevelopmental disorders. However, alterations in UFMylation and their role in and significance for age-related AD remains unknown. We performed Western blot and Meso Scale Discovery based ELISA to measure the protein level of UFM1, UFSP2, tau, p-tau and other UFMylation pathway components in human post-mortem brain. Analyses were performed with RIPA- and 2% SDS-soluble fraction from frontal cortex. To validate our finding in human tissues, we knocked out UFM1 and UFSP2 in ReN cells, a neural progenitor cell model that has already been used to study AD and that can be terminally differentiated in neurons. We found a significant reduction of RIPA UFSP2, but an increase of RIPA and SDS UFM1 in AD compared to controls. Strikingly, RIPA UFSP2 had a strong negative correlation with both RIPA and SDS UFM1. Furthermore. UFM1 was significantly increased in UFSP2-KO neurons compared to WT, mirroring the negative correlation between UFM1 and UFSP2 observed in human brain. In addition, RIPA and SDS UFM1 had a strong positive correlation with p-tau, indicating that dysfunctional UFMylation might play an important role for disease pathogenesis. Reduction of RIPA soluble UFSP2 in human AD frontal cortex might result in the abnormal accumulation of UFM1 and this might further facilitate the AD pathogenesis. Because of its role for several central AD-relevant pathways, the UFMylation pathway might be a potential therapeutic target for AD.

TREM2 AD risk variants impact pTau and microglia and astrocyte related biomarkers in cognitively unimpaired subjects

AbstractBackgroundIn the central nervous system, Triggering Receptor Expressed on Myeloid Cells 2 (TREM2) is expressed primarily in microglia. TREM2 receptors are important for microglial functions including phagocytosis, lipid metabolism and inflammatory responses. TREM2 coding variants (e.g. R47H rs75932628 and R62H rs143332484) increase the risk of late onset Alzheimer’s Diseases (AD). However, the impact of TREM2 risk variants on microglial cell functions in humans remains to be elucidated.MethodCSF and plasma samples were collected from AD patients (n = 120) and cognitively unimpaired control subjects (n = 53) with subjective complaints who do not meet biomarker‐based criteria for AD diagnosis. TREM2 AD risk variant carriers (n = 52) were screened from over 6000 samples of the Amsterdam dementia cohort using a combination of genotype array and exome sequencing. We performed extensive biomarker analysis of CSF and plasma samples with multidisciplinary approaches. We compared the effect of TREM2 mutations on AD disease and microglial and astrocytic biomarkers in AD patients and in cognitively unimpaired control subjects, respectively. A linear model was used with age and gender adjusted for the data analysis.ResultWe found higher levels of pTau181 and pTau231 in CSF and plasma in cognitively unimpaired TREM2 mutation carriers compared to non‐carriers, while no difference was observed between TREM2 genotype among the AD patients. Microglia and astrocyte biomarkers including sTREM2, FABP3, OLR1, YKL40 and GFAP were higher in the CSF from cognitively unimpaired TREM2 mutation carriers compared to non‐carriers, but no difference was detected between TREM2 genotype among the AD patients. We also found different levels of lipid metabolites in CSF and plasma samples from the TREM2 mutation carriers compared to non‐carriers in both AD patients and cognitively unimpaired control subjects.ConclusionTREM2 AD risk variants in cognitively unimpaired subjects increase pTau biomarkers and microglial and astrocytic related biomarkers. In AD patients, the biomarker differences between TREM2 genotype are diminished likely due to the extensive microglial responses to AD pathology. Moreover, our data indicates TREM2 AD risk variants may impact lipid‐metabolic processes in microglial cells. These data provide the biomarker insights on how TREM2 mutations may increase the risk of AD.

Diagnostic performance and clinical applicability of plasma pTau181 to predict dementia risk in a large real‐world cohort of a memory clinic

AbstractBackgroundThe Alzheimer Association has recently remarked the diagnostic and prognostic revolution that plasma biomarkers will mean for AD diagnosis, and highlighting the need of further research to translate them as a realistic option in the clinical practice. However, many studies to date have assessed them in research cohorts. Here we evaluated the diagnostic performance and clinical applicability of plasma pTau181 as a predictive marker of dementia risk in a real‐world memory clinic cohort.MethodThe ACE cohort encompass 1649 patients with subjective cognitive decline (SCD), mild cognitive impairment (MCI), AD dementia and other dementias, with a complete battery of neurological tests, biochemistry data, and paired CSF and plasma samples of the Ace Alzheimer Center Barcelona memory clinic. CSF AB42, AB40, pTau181 and tTau, and plasma pTau181 were measured using the Lumipulse G1200 automatic platform (Fujirebio Inc.). Complete cohort were divided in the Testing cohort (n = 1000) and Validation cohort (n = 649).ResultPlasma pTau181 significantly correlated (P<0.0001) with CSF pTau181 in MCI, AD dementia and other dementias, but not in SCD. Sex appeared not significant in plasma pTau181 levels, whereas age significantly influenced in the biomarker’s performance. ROC curve of A+T+ patients vs rest showed an AUC = 0.8250 and P<0.0001. Specifically for MCI patients, ROC curve of MCI A+T+ vs MCI A‐T‐ showed and AUC = 0.8874 and P<0.0001. A cut off value of 1.300 pg/ml of plasma pTau181 exhibited a 93.6% sensibility, 72.4% specificity, 77.8% precision and only 8.3% of false negatives in MCI patients. Hazard ratio of survival of conversion analysis showed that MCI patients above this cut off value exhibited a 4.570 higher risk to convert to dementia than MCI under the cut off value. Validation cohort confirmed these findings.ConclusionPlasma pTau181 could be useful as a pre‐screening biomarker of MCI patients with high risk to progress to dementia. However, positive patients will also require a CSF/PET confirmatory test. Plasma pTau181 by itself does not present a suitable performance in SCD patients. Another biomarker or a combination of biomarkers would be needed to this population. Further studies are need to obtain more clinical data and improve the biomarker performance to finally substitute CSF/PET biomarkers.

CSF Biomarkers and [18F]flutemetamol PET‐Derived Centiloids in Patients with SCD or MCI

AbstractBackgroundCSF biomarkers are well characterised as surrogate markers for amyloid deposition and neurofibrillary tau tangles reflecting pathological features of Alzheimer’s disease. Amyloid PET images provide a visual and quantitative assessment of brain amyloid burden. In diagnostic workup these biomarkers are considered interchangeable, however their relationship is not fully understood.MethodCentiloid (CL) values for 387 [18F]flutemetamol images from the Swedish BioFINDER I study were derived following the methods of Klunk et.al. (Alzheimer’s & Dementia, 2015). Subjects, comprising Controls, SCD and MCI (Table 1), were ranked by Centiloid values (lowest to highest) and the average for each consecutive group of 30 subjects calculated. Corresponding CSF biomarker values (Aß42/40 and pTau181) were plotted for each group.ResultSubjects in groups averaging ‐7.7 CL to 29.0 CL had a mean(±SD) Aß 42/40 ratio of 0.144 (±0.033, range 0.051 to 0.236, n = 240) with no statistically significant differences between groups (Fig. 1A). A statistically significant fall in CSF Aß42/40 ratio between the 29.0 CL and 47.3 CL groups (from 0.134 (+0.041, 0.066 to 0.236) to 0.088(+0.031, 0.045 to 0.183), p<0.0001) was observed. The average CSF Aß42/40 ratio value for all subjects ranging from 66.3 Cl to129.8 CL was 0.072 (±0.017, 0.030 to 0.127, n = 117) with no statistically significant difference in CSF levels across these CL bands. Subjects in the groups averaging ‐7.7 CL to 29.0 CL had a mean(±SD) pTau181 value of 48.9 pg/mL (±15.9, 22 to 138) with no statistically significant difference between groups (Fig. 1B). A statistically significant (p<0.05) increase between 29.0 CL (47.3±19.3, 24 to 116 pg/mL) and 47.3 CL groups (67.8±29.4, 24 to 175 pg/mL) was observed. For all Subjects from 66.3 CL to129.8 CL mean pTau181 levels were 79.6 (±30.3, 32 to 209 pg/mL) with no statistically significant difference across these CL bands.ConclusionComparison of [18F]flutemetamol image quantitation and CSF biomarkers indicates CSF Aß42/40 and pTau181 starts to show amyloid positivity at approximately 30‐40 CL units. Recent comparisons between visual rating and Centiloids from PET imaging indicate visual positivity from approximately 20 CL units indicating sensitivity of amyloid PET imaging for the detection of early amyloid deposition.

Subjective cognitive impairment and biomarkers of Alzheimer’s disease

AbstractBackgroundSubjective cognitive impairment (SCI) is common in older adults. It may represent the earliest clinical manifestation of cognitive decline and Alzheimer’s disease (AD).Objectives1) to evaluate associations between SCI and cerebrospinal fluid (CSF) biomarkers of AD; 2) to identify specific single questions or question combinations that are related to the presence of cerebral AD pathology; 3) to evaluate whether using SCI related scores or specific questions combined with other clinical features and biomarkers may improve prediction of cognitive decline.MethodWe conducted a longitudinal study in 164 non‐demented subjects participating on a biomarker study in a memory clinic setting, aged 53 to 88 years, with CDR scores of 0 (N = 84) and 0.5 (N = 80). SCI was assessed using the Cognitive Complaint Interview (CCI, Thomas‐Antérion et al., 2006), a validated 10 items questionnaire. Accordingly, SCI is defined as present when the subject answers “yes” to 3 or more items; and/or to item 5, and/or to items A, 4, 5, 7, 8. All participants underwent comprehensive neuropsychological evaluations and CSF biomarkers analysis. “Amyloid positivity" and “AD pathology” were defined according to the CSF Aβ1‐42 levels and pTau181/Aβ1‐42 ratio, respectively. Logistic regressions were used to address the associations of interest.ResultsParticipants with SCI had significantly lower Aβ1‐42 and higher Tau and pTau181 levels compared to those without SCI. SCI was associated with amyloid positivity while CCI total score and the question A (reporting changes in memory) were associated with both amyloid positivity and AD pathology in the whole cohort. When performing analysis separately in the CDR = 0 and CDR = 0.5 subgroups the associations remained significant in the CDR = 0.5 group. Only question 6 (difficulties in finding words) was associated with AD pathology in the CDR = 0 group. Results on the prediction of cognitive decline at follow‐up visits will be presented at the conference.ConclusionIn dementia‐free subjects from this memory clinic cohort SCI‐related scores and single questions indicate amyloid positivity and the presence of AD pathology depending on the absence/presence of mild cognitive impairment. Further studies are needed to evaluate the diagnostic and prognostic utility of cognitive complains in memory clinic patients.

Assessing the functional effect of the Presenilin‐1 G206A variant on age of onset of Alzheimer Disease in the Puerto Rican population

AbstractBackgroundThe variant G206A in Presenilin‐1 (PSEN1) gene has been identified almost exclusively in Alzheimer Disease (AD) Puerto Rican families. This variant represents a founder effect on the African background. The G206A variant associates with extreme variability in age of onset (AOO), ranging from 30 to 90 years. In contrast, other variants at the same amino acid of PSEN1 (G206N, G206S) have a tighter range of AOO (30‐35 years). We aim to identify the molecular mechanisms involved in the AOO variability between G206A carriers through functional analysis of induced pluripotent stem cells (iPSCs).MethodGenotyping data were phased using SHAPEIT to identify local ancestry and RFMix to estimate genetic ancestry. p‐Tau181 levels were tested from plasma using Simoa (Quanterix HD‐X). iPSCs of G206A carriers with different AOO were reprogrammed using non‐integrating Sendai virus. These clonal lines were assessed for pluripotency and chromosomal stability Isogenic construction of G206A iPSC lines is currently in progress.ResultWe screened for G206A carriers using whole genome from 896 individuals (182 families) and identified 43 carriers (39 AD and 4 cognitively unimpaired <65 years) from 8 families and 3 isolated cases. 55% of AD G206A carriers had AOO <65. A single African haplotype was identified in all G206Acarriers. We observed higher pTau181 levels in AD G206A carriers with early age of onset, compared to those with late onset. Association analysis did not identify APOE4 or SYNJ1 polymorphisms as contributing to the differences in AOO within G206A carriers. To perform functional studies, we selected three with early (<65) and three with late (>65) AOO AD peripheral blood mononuclear cells (PBMCs)that were reprogrammed into iPSC lines. G‐band Karyotype, factor loss analyses, genetic finger printing, immunocytochemistry (ICC) and qRT‐PCR for intracellular and surface pluripotency markers was confirmed in the iPSC lines.ConclusionThe PSEN1 G206A variant, originating in African ancestry haplotype revealing a founder effect, is an important contributor to AD in an underserved population. Understanding the role of the G206A variant in AD pathogenesis and the factors that influence its effect on AOO will provide insight on AD pathogenesis, age of onset variation and identification of potential novel therapeutic targets.

Digital and plasma biomarkers for an early diagnosis of Mild Cognitive Impairment and prodromal Alzheimer’s disease

AbstractBackgroundThe application of blood‐based biomarkers for the identification of Alzheimer’s disease (AD) and the development of novel digital technologies as cognitive screening tests are critical to moving toward a reliable, more accessible early diagnosis. Our aim was to evaluate the diagnostic performance of a machine learning‐based cognitive assessment known as Altoida’s digital neuro‐signature (DNS) in patients with non‐degenerative mild cognitive impairment (ndMCI) and MCI due to AD (prodromal AD) and its association with CSF and plasma biomarkers.MethodAltoida’s MCI‐DNS is a 10‐minute cognitive test battery evaluating activities of daily living via motoric and augmented reality tasks. The test consists of placing and finding virtual objects in a real environment and its final score is obtained by weighting multi‐modal digital data features, such as hands’ micro‐movements, speed, reaction times, or navigation trajectories. We included 81 participants, classified according to their clinical status and CSF AD biomarker profile as: cognitively unimpaired controls, CTR (n = 10; age = 68.5±5.9; MMSE = 29.4±1.1), ndMCI (n = 25; age = 67.6±7.2; MMSE = 26.9±1.9) and prodromal AD (n = 46; age = 70.8±4.9; MMSE = 24.3±3.3). We further investigated a subsample of participants classified according to their plasma pTau181 levels as measured by SiMoA [cutoff = 1.37 pg/mL (Sarto et al., 2022)]: pTau181 negative (n = 27; age = 68.5±5.9; MMSE = 26.9±2.7) or pTau181 positive (n = 30; age = 70.3±5.5; MMSE = 24.1±3.7).ResultSignificant differences were found in MCI‐DNS scores between CTR group and ndMCI (F = 23.5; p<0.001) and prodromal AD (F = 114.4; p<0.001) groups. Also, ndMCI showed higher MCI‐DNS scores than the prodromal AD group (F = 4.53; p<0.05, Fig. 1). ROC curves showed an excellent diagnostic accuracy of the MCI‐DNS in the discrimination between CTR vs. ndMCI (AUC = 0.879) and CTR vs. prodromal AD (AUC = 0.975) (Fig. 1). Further analyses showed differences in MCI‐DNS scores between CSF Aβ42 negative and CSF Aβ42 positive (F = 18.9; p<0.001; Fig. 2), as well as between plasma pTau181 negative and plasma pTau181 positive (F = 6.16; p<0.01; Fig. 2). Finally, MCI DNS scores significantly correlated with CSF Aβ42, CSF Aβ42/pTau ratio, CSF neurofilament‐light chain (NfL) and plasma pTau181 concentrations (Fig. 3).ConclusionAltoida’s MCI‐DNS test allows excellent discrimination between CTR and patients with MCI. MCI‐DNS scores significantly correlate with CSF AD core biomarkers, biomarkers of neurodegeneration and blood‐based biomarkers (i.e., plasma pTau181).

CSF Biomarkers and [18F]flutemetamol PET‐Derived Centiloids in Patients with SCD or MCI

AbstractBackgroundCSF biomarkers are well characterised as surrogate markers for amyloid deposition and neurofibrillary tau tangles reflecting pathological features of Alzheimer’s disease. Amyloid PET images provide a visual and quantitative assessment of brain amyloid burden. In diagnostic workup these biomarkers are considered interchangeable, however their relationship is not fully understood.MethodsCentiloid (CL) values for 387 [18F]flutemetamol images from the Swedish BioFINDER I study were derived following the methods of Klunk et.al. (Alzheimer’s & Dementia, 2015). Subjects, comprising Controls, SCD and MCI (Table 1), were ranked by Centiloid values (lowest to highest) and the average for each consecutive group of 30 subjects calculated. Corresponding CSF biomarker values (Aβ42/40 and pTau181) were plotted for each group.ResultsSubjects in groups averaging ‐7.7 CL to 29.0 CL had a mean(±SD) Aβ 42/40 ratio of 0.144 (±0.033, range 0.051 to 0.236, n = 240) with no statistically significant differences between groups (Fig. 1A). A statistically significant fall in CSF Aβ42/40 ratio between the 29.0 CL and 47.3 CL groups (from 0.134 (±0.041, 0.066 to 0.236) to 0.088(±0.031, 0.045 to 0.183), p<0.0001) was observed. The average CSF Aβ42/40 ratio value for all subjects ranging from 66.3 Cl to129.8 CL was 0.072 (±0.017, 0.030 to 0.127, n = 117) with no statistically significant difference in CSF levels across these CL bands.Subjects in the groups averaging ‐7.7 CL to 29.0 CL had a mean(±SD) pTau181 value of 48.9 pg/mL (±15.9, 22 to 138) with no statistically significant difference between groups (Fig. 1B). A statistically significant (p<0.05) increase between 29.0 CL (47.3±19.3, 24 to 116 pg/mL) and 47.3 CL groups (67.8±29.4, 24 to 175 pg/mL) was observed. For all Subjects from 66.3 CL to129.8 CL mean pTau181 levels were 79.6 (±30.3, 32 to 209 pg/mL) with no statistically significant difference across these CL bands.ConclusionsComparison of [18F]flutemetamol image quantitation and CSF biomarkers indicates CSF Aβ42/40 and pTau181 starts to show amyloid positivity at approximately 30‐40 CL units. Recent comparisons between visual rating and Centiloids from PET imaging indicate visual positivity from approximately 20 CL units indicating sensitivity of amyloid PET imaging for the detection of early amyloid deposition.

Age‐Related Enhanced BMP Signaling Elicits APOE‐Isoform Dependent Effects in IPSC Model of Alzheimer’s Disease

AbstractBackgroundAging is the strongest risk factor for developing Alzheimer’s Disease (AD), and APOE is the largest genetic risk factor for developing AD. Bone morphogenic protein 4 (BMP4) expression and subsequent signaling increases 10‐fold with age and is increased in AD patients compared to age‐matched controls. Enhanced BMP signaling in aged and AD brains suggest a potential molecular cascade involved in AD pathogenesis. A potential interaction exists between increased BMP signaling across lifespan APOE expression that contribute to risk of AD.MethodAD patient derived iPSC’s (APOE3/E4 genotype) and isogenic controls (APOE3/E3 genotype) were differentiated into astrocytes and neurons. Cells were grown for 35 days before treatment with BMP4 or vehicle for 3 days prior to fixation, protein/media collection, or preparation for single cell RNA sequencing (scRNAseq). For coculture studies, neurons and astrocytes of the same patient background were differentiated separately prior to combined plating and BMP treatment. Cocultures were in matched (APOE3/E4 neurons with APOE3/E4 astrocytes) or mismatched (APOE3/E3 neurons with APOE3/E4 astrocytes) conditions to understand the non‐cell autonomous effects of APOE genotype.ResultUpon BMP treatment, APOE3/E4 compared to APOE3/E3 astrocytes exhibit accumulation of lipid droplets with changes in lipid composition. Increased free cholesterol levels as well as triglyceride accumulation is observed in APOE3/E4 astrocytes and is further exacerbated with BMP treatment. RNA‐sequencing analysis reveals marked decreased expression in genes related to oxidative phosphorylation and increased cholesterol synthesis and metabolism in APOE3/E4 astrocytes that is modulated by BMP treatment. In a non‐cell autonomous fashion, APOE3/E3 neurons, when paired with APOE3/E4 astrocytes, express exacerbated pTau levels and aberrant metabolic processes in a BMP‐dependent manner.ConclusionOur results indicate an interaction between genetic and aging factors in cellular processes relevant to AD. Enhanced BMP signaling confers aberrant lipid composition and metabolic processing in APOE3/E4 astrocytes when compared to APOE3/E3. Subsequent BMP‐dependent non‐cell autonomous effects in APOE3/E3 neurons are observed when cocultured with APOE3/E4 astrocytes. This data suggests age‐associated increase in BMP signaling may modulate APOE isoform‐dependent metabolic processes and increase risk for APOE‐mediated pathological cascades.

Phosphorylated tau in the Down syndrome brain: Age related increases and comparison to late‐onset Alzheimer’s Disease

AbstractBackgroundIndividuals with Down Syndrome (DS) have an increased risk of developing Alzheimer’s Disease (AD) with nearly all individuals exhibiting neuropathological changes in the brain by age 40 years, and with a mean diagnosis of dementia by age ∼55 years. The purpose of this postmortem study was to characterize the age‐associated burden of several tau phosphorylation epitopes, including threonine (pT) 181, 217, and 231 by immunohistochemistry in the frontal cortex. We hypothesized that cerebral pT burden would increase with age in DS but not in controls and be higher in DS with AD neuropathology (DSAD) compared to late‐onset AD (LOAD).MethodWe examined 117 brains from: controls (non‐DS n = 53; ages 1‐91), DS without AD (n = 13; ages 1‐48), DSAD (n = 31; age 43‐68), and LOAD (n = 20; ages 63‐96). Serial sections from the frontal cortex were cut at 30µm and immunostained for phosphorylated tau pT181, pT217 and pT231. Whole slide images were digitized and analyzed by Aperio ImageScope software. The % area for each type of tau was quantified using positive pixel counts. Spearman rank correlations on log‐transformed data were used to test for positive age associations and t‐test was used to compare pT between DSAD and LOAD.ResultIn control cases, there was a positive correlation of age with pT181 (r = 0.47 p<0.001) but not with pT217 or pT231. In DS cases across the lifespan (DS and DSAD combined) displayed a positive correlation of age with pT181 (r = 0.70 p<.001), pT217 (r = 0.70 p<.001), and pT231 (r = 0.42 p = 0.005). DSAD cases had significantly higher pT181, pT217 and pT231 (p<.001) than late‐onset AD and control cases.ConclusionThese results suggest that tau phosphorylation for these epitopes is more positively correlated with age in people with DS than people without DS. Although pT181 increased with age in both cohorts, pT217 and pT231 showed a positive correlation with age in people with DS but not controls. Fluid biomarker studies focused on pTau in longitudinal cohorts of people with DS with subsequent brain donation will help reveal the link between peripheral and central pTau levels.