Clusterin is a major cholesterol transporter in the central nervous system (CNS) and different SNPs in the CLU gene have been associated with Alzheimer’s disease (AD) risk. The rs11136000_T variant in the CLU gene has been shown to decrease the risk of AD. In this work, we investigate the role of the CLU rs11136000_T protective variant and of the clusterin protein throughout different phases of the AD spectrum. Levels of clusterin, Tau, phospho(181) Tau (p-tau), and Aß were measured using ELISA and synaptic proteins were measured using immunoprecipitation followed by mass spectroscopy in the CSF of cognitively unimpaired individuals. Flortaucipir PET was used to measure tau deposition and 18F-NAV4694 PET was used to measure amyloid burden in the same subjects. ELISA was used to measure clusterin levels and RT-PCR was used to measure mRNA levels in cortical areas of autopsied-confirmed controls and AD subjects. Genotype was performed using Illumina Infinium Omni2.5M-8 microarray. There was no effect of the protective genotype on the levels of PET biomarkers, CSF biomarkers or synaptic proteins in cognitively unimpaired individuals. CSF clusterin levels were positively associated with Aß (p = 0.021), total-tau (p<0.001), p-tau (p<0.001), synaptotagmin (p<0.001), SNAP 25 (p = 00006), GAP 43 (p = 0.00055) and neurogranin (p = 0.0086) in the CSF and with amyloid deposition in the hippocampus (p = 0.018) and tau retention in the entorhinal cortex (p = 0.0082) and temporal pole (p = 0.0124) in cognitively unimpaired individuals at high risk for AD. Clusterin is increased in the brain of individuals who are homozygous for the CLU_T variant (p = 0.04) and in AD patients compared to age-matched controls (p = 0.024). mRNA levels are increased in individuals homozygous for the CLU_T variant (p = 0.003), but there are no significant differences in AD patients compared to controls (p = 0.07). Our work shows significant correlation between CSF clusterin and the main AD biomarkers (PET and CSF) and synaptic proteins before disease onset, in subjects at high risk for the disease. In the later stage of the disease, clusterin protein and CLU mRNA levels are increased as a function of genotype and disease status, suggesting that CLU may play a protective role by increases in gene expression in the CNS.

Inflammation is central to Alzheimer Disease (AD), as astrocyte reactivity accompanies the appearance of Aβ and phosphorylated tau (Bellaver et al., 2023). As expected, therefore, AD patients have elevated levels of CSF inflammatory cytokines (Onyango et al., 2021). To understand the importance of these phenomena, exploration of individual inflammatory markers before and at the time of dementia onset is needed. To uncover key CK/Rs involved in the early pathogenesis of AD, we investigated selected cytokines and their receptors (CK/Rs) in the preclinical stages of the disease. We analyzed 433 longitudinal CSF samples from 104 participants in the PREVENT-AD cohort. These persons, who were symptom-free at baseline but at enhanced risk of developing AD because of their family history, have now been followed for over 10 years. We used ELISA to analyze Aβ42, p181, and total tau in the CSF [Fujirebio Innotest, Ghent, Belgium], while CK/Rs were assayed using the Olink proximity extension assay Target 96 Inflammation panel [Upsala, Sweden]. Linear mixed model analyses controlled for participant age and APOE4 status. We found that IL10RB, IL18, and CD40 levels in the CSF were significantly associated with both p(181)tau and Aβ42 levels in the CSF over time. IL10RB, IL18, and CD40 each showed significant positive association with p(181)tau levels across time (F(1,213.191) = 7.013, p = 0.009; F(1,237.624) = 9.972, p = 0.002; F(1,246.859) = 8.211, p = 0.005). The longitudinal effects of IL10RB and IL18 on Aβ42 were contingent on both sex and time (F(5,55.406) = 2.548, p = 0.038; F(5,54.792) = 4.280, p = 0.002), while the significantly positive association of CD40 levels on Aβ42 across time was stronger in females than in males (F(1, 59.669) = 4.099, p = 0.047). These investigations of CSF proteins in preclinical AD persons identified inflammatory markers that exhibited specific relationships with p(181)tau and Aβ42 across time and sex. These results may guide further study of biomarkers for detection of AD in its preclinical stages, and/or therapeutic strategies. Of special importance, characterization of the pathogenesis of pre-symptomatic AD may facilitate development of early interventions for the prevention of AD dementia.

Scavenger receptors (SR) are a group of receptors involved in the endocytosis of various ligands, such as modified LDL and soluble β-amyloid, which connects them to Alzheimer’s disease (AD). SCARF2 (SREC-II) is part of the SR family, but unlike other scavenger receptors, internalizes a low amount of modified LDL. Its main function revolves around the binding of Aβ (Vo et al. 2023). Other studies found SCARF2 to be a SCARF1 inhibitor (Ishii et al. 2002). This study compares gene expression and protein levels of SCARF2 in post-mortem brain tissue of AD and control subjects, as well as in the CSF of participants with a family history of AD. The goal is to track the progression of AD using the expression pattern of SCARF2. SCARF2 CSF protein levels were assessed in the PREVENT-AD (PRe-symptomatic EValuation of Experimental or Novel Treatments for Alzheimer’s Disease) cohort which is composed of asymptomatic subjects with parental history of AD. SCARF2 has been measured with a primer extension assay using Olink technology. ELISA immunoassay has been used to quantify SCARF2 protein levels in frontal cortex homogenates of 86 brains from the Douglas Bell Canada Brain Bank (DBCBB). mRNA prevalence was measured using Gene Chip Clariom D human microarray. All statistical analyses were performed using JMP pro 17 software. SCARF2 Protein levels, but not mRNA, are significantly lower in brains with AD (p<0.001). SCARF2 protein display a strong negative association with plaques bound Aβ, despite being a well-established Aβ receptor (R 2 = 0.277, p<0.0001). Interestingly, CSF protein levels correlate positively with AD biomarkers such as total and phosphorylated(181) tau (R 2 = 0.235, p<0.0001; R 2 = 0.288, p<0.0001) and Aβ to a lesser extent (R 2 = 0.045, p = 0.0318). Our study unveils a distinctive role for SCARF2 in AD pathogenesis. Despite being a known Aβ receptor, SCARF2 exhibits lower cortical protein levels in AD brains, inversely linked to plaques bound Aβ. In contrast, elevated CSF SCARF2 protein levels correlate positively with CSF AD biomarkers in the presymptomatic phase of the disease; suggesting differential response to amyloid and tau deposition. These findings shed light on the intricate interplay of SCARF2 in AD pathophysiology, offering potential avenues for further research.

Synaptic dysfunction is a central pathologic feature of Alzheimer’s disease (AD), with synaptic loss even preceding neuronal loss in specific brain regions. In healthy individuals, synaptic function and plasticity are orchestrated through the complex integration of signaling inputs generated by cell surface receptors. In this study, we investigate the role of one such receptor, protein tyrosine phosphatase receptor sigma (PTPRS), in the context of Alzheimer’s disease. Publicly available datasets (BRAINEAC, ROSMAP, ADC1) and a cohort of asymptomatic but “at risk” individuals (PREVENT-AD) were used to explore the relationship between PTPRS and various Alzheimer’s disease biomarkers. We identified that PTPRS rs10415488 variant C shows features of neuroprotection against early phospho (181)-tau pathology (p<0.005) and synaptic degeneration (GAP-43, p<0.001) in Alzheimer’s disease. In brain tissues, PTPRS protein abundance was significantly correlated with the quantity of two markers of synaptic integrity: SNAP25(R 2 =0.20, p < 0.0001) and SYT-1(R 2 =0.12, p < 0.0001). We also found the presence of sexual dimorphism for PTPRS, with higher CSF concentrations in males (p<0.001) than females. Male carriers for variant C exhibit a 10-month delay in the onset of AD (p <0.05). One molecular function of PTPRS we chose to explore is macrophagy, given the implication of this biological process in the response against neurodegeneration. Macrophagy-associated LC3 immunoreactivity occurs in most dystrophic neurites in AD and co-localized with abnormal P-tau in most neurofibrillary tangles. In the ROSMAP subjects, LC3 cortical protein levels were found to be significant reduced in C carriers PTPRS acts as a soluble, secreted neuroprotective receptor, found in the extracellular space in Alzheimer’s disease. These findings also highlight the functional importance of synaptic plasticity in the protection against neurodegenerative diseases.

The heterogeneous etiology of “sporadic” Alzheimer’s disease (sAD) includes genetic influences. To better understand synaptic dysfunction in AD pathogenesis, we used protein quantitative train loci (pQTL) assessments and a polygenic risk score (PRS) to examine the relationship between synaptic integrity and longitudinal cognitive performance in the presymptomatic phase of the disease. The PREVENT-AD cohort includes symptom-free elderly participants at risk of AD because of their family history. A second resource, the Quebec Founder Population (QFP) brain bank, derives from the descendants of the 17 th and 18 th century French settlers in Eastern Canada. We used Olink Proximity Extension Assays to measure the soluble synaptic proteins ADAM 22 (post-synaptic) and ADAM23 (pre-synaptic) in 120 CSFs, while immunoprecipitated SYT1 (pre-synaptic) and SNAP25 (pos-synaptic) were analyzed in 141 CSF samples using a quadrupole–orbitrap mass spectrometer. The Repeatable Battery for Assessment of Neuropsychological Status (RBANS) indicated cognitive trajectory. Genotyping was performed using the Illumina Infinium Omni 2.5M-8 array. Cortical RNAs (n=86) from the QFP cohort were processed using GeneChip WT Pico Kit. Statistical analyses included sex, education and APOE e4 status as covariates. Among PREVENT-AD participants who remained cognitively unimpaired over the past 11 years, we observed significant correlations between a PRS constructed from pQTL ADAM 22 CSF concentrations and delayed memory (R 2 = 0.06, p = 0.0132), visuospatial constructional memory (R 2 = 0.274, p = 0.00408) and total index scale (R 2 = 0.202, p = 0.0454), but only trend-levels association with immediate memory (R 2 = 0.1, p = 0.0747). We also found similar correlations between PRS constructed from of CSF ADAM 23, CSF SYT1, CSF SNAP25 concentrations and the different RBANS subscales. Significantly lower cortical mRNA levels for ADAM22 (p = 0.062), ADAM23 (p = 0.0030), SYT1 (p = 0.033) and SNAP25 (p = 0.0036) were found in the autopsied AD brains compared to autopsied control brains. CSF synaptic protein levels show promising correlations with emerging cognitive deficits and provide insights toward a possible compensatory mechanism in the early presymptomatic phase of the disease.

The immune complement system is key to the elimination of redundant neural connections in the brain through a process called synaptic pruning. In neurodegenerative diseases such as Alzheimer's disease (AD), this system may result in excessive synapse loss, leading to brain atrophy and cognitive impairment. While increased cerebrospinal fluid (CSF) levels of complement proteins have been observed in patients with AD dementia, no studies have yet investigated the role of complement in the pre-symptomatic phase of AD, nor throughout its progression. We used Luminex technology to assess complement protein levels in 566 CSF samples obtained over five years from 160 high-risk asymptomatic subjects with familial history of AD [the PREVENT-AD cohort; Breitner et al, 2016: JPAD 3,(4) 236]. Baseline complement levels were contrasted with CSF biomarkers of AD pathology (Aβ42, p(181) and total tau, NFL) and markers of synaptic dysfunction (GAP-43, SYT1, SNAP-25, ADAM22, ADAM23). Analyses were stratified by sex and ApoE4 carrier status. Currently pending are additional longitudinal analyses probing complement levels versus PET-quantified cerebral amyloid and tau deposition, MRI volume of AD-implicated structures, and cognitive ability (RBANS). Preliminary analyses revealed significant positive associations between complement proteins and p-(181)tau (C1q: R 2 = .238, p < .0001; C3: R 2 = .041, p = .0099; C3b: R 2 = .027, p = .0384; Factor H: R 2 = .128, p < .0001) and total tau levels (C1q: R 2 = .247, p < .0001; C3: R 2 = .023, p = .0543; Factor H: R 2 = .128, p < .0001). Complement relationships with synaptic protein levels were more significant overall in females, which showed the following associations [GAP-43 (C1q: R 2 = .389, p < .0001; Factor H: R 2 = .315, p = .0002); SNAP-25 (C1q: R 2 = .367, p < .0001; C3: R 2 = .106, p = .0459; Factor H: R 2 = .278, p = .0072); SYT1 (C1q: R 2 = .316, p = .0002; Factor H: R 2 = .246, p = .0015)]. There is a clear association between complement levels, tau pathology, and synaptic markers in the asymptomatic phase of AD, especially in women. Longitudinal and multimodal investigation is ongoing to further characterize these relationships.

Study Objectives Although short sleep could promote neurodegeneration, long sleep may be a marker of ongoing neurodegeneration, potentially as a result of neuroinflammation. The objective was to evaluate sleep patterns with age of expected Alzheimer's disease (AD) onset and neuroinflammation.Methods We tested 203 dementia-free participants (68.5 +/- 5.4 years old, 78M). The PREVENT-AD cohort includes older persons with a parental history of AD whose age was nearing their expected AD onset. We estimated expected years to AD onset by subtracting the participants' age from their parent's at AD dementia onset. We extracted actigraphy sleep variables of interest (times of sleep onset and morning awakening, time in bed, sleep efficiency, and sleep duration) and general profiles (sleep fragmentation, phase delay, and hypersomnia). Cerebrospinal fluid (CSF) inflammatory biomarkers were assessed with OLINK multiplex technology.Results Proximity to, or exceeding, expected age of onset was associated with a sleep profile suggestive of hypersomnia (longer sleep and later morning awakening time). This hypersomnia sleep profile was associated with higher CSF neuroinflammatory biomarkers (IL-6, MCP-1, and global score). Interaction analyses revealed that some of these sleep-neuroinflammation associations were present mostly in those closer/exceeding the age of expected AD onset, APOE4 carriers, and those with better memory performance.Conclusions Proximity to, or exceeding, parental AD dementia onset was associated with a longer sleep pattern, which was related to elevated proinflammatory CSF biomarkers. We speculate that longer sleep may serve a compensatory purpose potentially triggered by neuroinflammation as individuals are approaching AD onset. Further studies should investigate whether neuroinflammatory-triggered long sleep duration could mitigate cognitive deficits. Graphical Abstract

We examined the role of protein tyrosine phosphatase receptor sigma (PTPRS) in the context of Alzheimer's disease and synaptic integrity. Publicly available datasets (BRAINEAC, ROSMAP, ADC1) and a cohort of asymptomatic but "at risk" individuals (PREVENT-AD) were used to explore the relationship between PTPRS and various Alzheimer's disease biomarkers. We identified that PTPRS rs10415488 variant C shows features of neuroprotection against early Tau pathology and synaptic degeneration in Alzheimer's disease. This single nucleotide polymorphism correlated with higher PTPRS transcript abundance and lower p(181)Tau and GAP-43 levels in the CSF. In the brain, PTPRS protein abundance was significantly correlated with the quantity of two markers of synaptic integrity: SNAP25 and SYT-1. We also found the presence of sexual dimorphism for PTPRS, with higher CSF concentrations in males than females. Male carriers for variant C were found to have a 10-month delay in the onset of AD. We thus conclude that PTPRS acts as a neuroprotective receptor in Alzheimer's disease. Its protective effect is most important in males, in whom it postpones the age of onset of the disease.

Insulin, insulin-like growth factors (IGF) and their receptors are highly expressed in the adult hippocampus. Thus, disturbances in the insulin-IGF signalling pathway may account for the selective vulnerability of the hippocampus to nascent Alzheimer's disease (AD) pathology. In the present study, we examined the predominant IGF-binding protein in the CSF, IGFBP2.CSF was collected from 109 asymptomatic members of the parental history-positive PREVENT-AD cohort. CSF levels of IGFBP2, core AD and synaptic biomarkers were measured using proximity extension assay, ELISA and mass spectrometry. Cortical amyloid-beta (A beta) and tau deposition were examined using 18F-NAV4694 and flortaucipir. Cognitive assessments were performed during up to 8 years of follow-up, using the Repeatable Battery for the Assessment of Neuropsychological Status. T1-weighted structural MRI scans were acquired, and neuroimaging analyses were performed on pre-specified temporal and parietal brain regions. Next, in an independent cohort, we allocated 241 dementia-free ADNI-1 participants into four stages of AD progression based on the biomarkers CSF A beta 42 and total-tau (t-tau). In this analysis, differences in CSF and plasma IGFBP2 levels were examined across the pathological stages. Finally, IGFBP2 mRNA and protein levels were examined in the frontal cortex of 55 autopsy-confirmed AD and 31 control brains from the Quebec Founder Population (QFP) cohort, a unique population isolated from Eastern Canada.CSF IGFBP2 progressively increased over 5 years in asymptomatic PREVENT-AD participants. Baseline CSF IGFBP2 was positively correlated with CSF AD biomarkers and synaptic biomarkers, and negatively correlated with longitudinal changes in delayed memory (P = 0.024) and visuospatial abilities (P = 0.019). CSF IGFBP2 was negatively correlated at a trend-level with entorhinal cortex volume (P = 0.082) and cortical thickness in the piriform (P = 0.039), inferior temporal (P = 0.008), middle temporal (P = 0.014) and precuneus (P = 0.033) regions. In ADNI-1, CSF (P = 0.009) and plasma (P = 0.001) IGFBP2 were significantly elevated in Stage 2 [CSF A beta(+)/t-tau(+)]. In survival analyses in ADNI-1, elevated plasma IGFBP2 was associated with a greater rate of AD conversion (hazard ratio = 1.62, P = 0.021). In the QFP cohort, IGFBP2 mRNA was reduced (P = 0.049); however, IGFBP2 protein levels did not differ in the frontal cortex of autopsy-confirmed AD brains (P = 0.462).Nascent AD pathology may induce an upregulation in IGFBP2 in asymptomatic individuals. CSF and plasma IGFBP2 may be valuable markers for identifying CSF A beta(+)/t-tau(+) individuals and those with a greater risk of AD conversion. Brain changes associated with Alzheimer's disease can begin up to 20 years or more before the onset of symptoms. Quesnel et al. find that a protein called IGFBP2 may be a valuable marker for identifying at-risk individuals and could serve as a drug target to restore deficient insulin signalling in the Alzheimer's disease brain.

INTRODUCTION:We investigate the role of osteopontin (OPN) in participants with Pre-symptomatic Alzheimer's disease (AD), mild cognitive impairment (MCI), and in AD brains. METHODS:Cerebrospinal fluid (CSF) OPN, AD, and synaptic biomarker levels were measured in 109 cognitively unimpaired (CU), parental-history positive Pre-symptomatic Evaluation of Experimental or Novel Treatments for Alzheimer's Disease (PREVENT-AD) participants, and in 167 CU and 399 participants with MCI from the Alzheimer's Disease Neuroimaging Initiative (ADNI) cohort. OPN levels were examined as a function of amyloid beta (Aβ) and tau positivity. Survival analyses investigated the link between OPN and rate of conversion to AD. RESULTS:In PREVENT-AD, CSF OPN was positively correlated with synaptic biomarkers. In PREVENT-AD and ADNI, OPN was elevated in CSF Aβ42/40(+)/total tau(+) and CSF Aβ42/40(+)/phosphorylated tau181(+) individuals. In ADNI, OPN was increased in Aβ(+) positron emission tomography (PET) and tau(+) PET individuals, and associated with an accelerated rate of conversion to AD. OPN was elevated in autopsy-confirmed AD brains. DISCUSSION:Strong associations between CSF OPN and key markers of AD pathophysiology suggest a significant role for OPN in tau neurobiology, particularly in the early stages of the disease. HIGHLIGHTS:In the Pre-symptomatic Evaluation of Experimental or Novel Treatments for Alzheimer's Disease cohort, we discovered that cerebrospinal fluid (CSF) osteopontin (OPN) levels can indicate early synaptic dysfunction, tau deposition, and neuronal loss in cognitively unimpaired elderly with a parental history. CSF OPN is elevated in amyloid beta(+) positron emission tomography (PET) and tau(+) PET individuals. Elevated CSF OPN is associated with an accelerated rate of conversion to Alzheimer's disease (AD). Elevated CSF OPN is associated with an accelerated rate of cognitive decline on the Alzheimer's Disease Assessment Scale-Cognitive subscale 13, Montreal Cognitive Assessment, Mini-Mental State Examination, and Clinical Dementia Rating Scale Sum of Boxes. OPN mRNA and protein levels are significantly upregulated in the frontal cortex of autopsy-confirmed AD brains.

INTRODUCTION Measuring day-to-day sleep variability might reveal unstable sleep-wake cycles reflecting neurodegenerative processes. We evaluated the association between Alzheimer's disease (AD) fluid biomarkers with day-to-day sleep variability. METHODS In the PREVENT-AD cohort, 203 dementia-free participants (age: 68.3 +/- 5.4; 78 males) with a parental history of sporadic AD were tested with actigraphy and fluid biomarkers. Day-to-day variability (standard deviations over a week) was assessed for sleep midpoint, duration, efficiency, and nighttime activity count. RESULTS Lower cerebrospinal fluid (CSF) ApoE, higher CSF p-tau181/amyloid-beta (A beta)(42), and higher plasma p-tau231/A beta(42) were associated with higher variability of sleep midpoint, sleep duration, and/or activity count. The associations between fluid biomarkers with greater sleep duration variability were especially observed in those that carried the APOE4 allele, mild cognitive impairment converters, or those with gray matter atrophy. DISCUSSION Day-to-day sleep variability were associated with biomarkers of AD in at-risk individuals, suggesting that unstable sleep promotes neurodegeneration or, conversely, that AD neuropathology disrupts sleep-wake cycles.

Background: Apolipoproteins and contactin 5 are proteins associated with Alzheimer's disease (AD) pathophysiology. Apolipoproteins act on transport and clearance of cholesterol and phospholipids during synaptic turnover and terminal proliferation. Contactin 5 is a neuronal membrane protein involved in key processes of neurodevelopment. Objective: To investigate the interactions between contactin 5 and apolipoproteins in AD, and the role of these proteins in response to neuronal damage. Methods: Apolipoproteins (measured by Luminex), contactin 5 (measured by Olink's proximity extension assay), and cholesterol (measured by liquid chromatography mass spectrometry) were assessed in the cerebrospinal fluid (CSF) and plasma of cognitively unimpaired participants (n = 93). Gene expression was measured using polymerase chain reaction in the frontal cortex of autopsied-confirmed AD (n = 57) and control subjects (n = 31) and in the hippocampi of mice following entorhinal cortex lesions. Results: Contactin 5 positively correlated with apolipoproteins B (p = 5.4x10(-8)), D (p = 1.86x10(-4)), E (p = 2.92x10(-9)), J (p = 2.65x10(-9)), and with cholesterol (p = 0.0096) in the CSF, and with cholesterol (p = 0.02), HDL (p = 0.0143), and LDL (p = 0.0121) in the plasma. Negative correlations were seen between CNTN5, APOB (p = 0.034) and APOE (p = 0.015) mRNA levels in the brains of control subjects. In the mouse model, apoe and apoj gene expression increased during the reinnervation phase (p < 0.05), while apob (p = 0.023) and apod (p = 0.006) increased in the deafferentation stage. Conclusions: Extensive interactions were observed between contactin 5 and apolipoproteins and cholesterol, possibly due to neuronal damage. The alterations in gene expression of apolipoproteins suggest a role in axonal, terminal, and synaptic remodeling in response to entorhinal cortex damage.

Apolipoprotein B (APOB), a receptor-binding protein present in cholesterol-rich lipoproteins, has been implicated in Alzheimer's disease (AD). High levels of APOB-containing low-density lipoproteins (LDL) are linked to the pathogenesis of both early-onset familial and late-onset sporadic AD. Rare coding mutations in the APOB gene are associated with familial AD, suggesting a role for APOB-bound lipoproteins in the central nervous system. This research explores APOB gene regulation across the AD spectrum using four cohorts: BRAINEAC (elderly control brains), DBCBB (controls, AD brains), ROSMAP (controls, MCI, AD brains), and ADNI (control, MCI, AD clinical subjects). APOB protein levels, measured via mass spectrometry and ELISA, positively correlated with AD pathology indices and cognition, while APOB mRNA levels showed negative correlations. Brain APOB protein levels are also correlated with cortical Aβ levels. A common coding variant in the APOB gene locus affected its expression but didn't impact AD risk or brain cholesterol concentrations, except for 24-S-hydroxycholesterol. Polymorphisms in the CYP27A1 gene, notably rs4674344, were associated with APOB protein levels. A negative correlation was observed between brain APOB gene expression and AD biomarker levels. CSF APOB correlated with Tau pathology in presymptomatic subjects, while cortical APOB was strongly associated with cortical Aβ deposition in late-stage AD. The study discusses the potential link between blood-brain barrier dysfunction and AD symptoms in relation to APOB neurobiology. Overall, APOB's involvement in lipoprotein metabolism appears to influence AD pathology across different stages of the disease.

We previously showed that day-to-day sleep variability was associated with biomarkers of Alzheimer’s disease (AD) pathology. Given that brain-derived neurotrophic factor (BDNF) activity has been involved in both AD and cognitive impacts of lifestyle risk factors, we sought to evaluate day-to-day sleep variability in those carrying the Met allele of the Val66Met BDNF polymorphism, which affects BDNF release. Additionally, we explored whether BDNF polymorphism modified the association between CSF AD pathology and day-to-day sleep variability. The PREVENT-AD cohort enrolls dementia-free persons with a parental history of sporadic AD. We characterized 203 dementia-free participants from this cohort at the polymorphic BDNF locus, identifying 136 persons with genotype Val/Val (age 68.2±5.3y, 75%women), 67 Met heterozygotes/homozygotes (68.4±5.6y, 73% women, including six Met/Met homozygotes). After a week of actigraphy, we calculated these participants’ standard deviation of day-to-day sleep characteristics. We used t-tests to compare day-to-day sleep variability in sleep characteristics between Val homozygotes and Met carriers. In a subsample of 101 participants, we assayed CSF Aβ 42 , t-tau and p-tau181, and used age- and sex-adjusted linear regressions with an interaction term to test for moderation by BDNF genotype (36 Met carriers vs. 65 Val homozygotes) between sleep variability and CSF biomarker results. As compared to Val homozygotes, sleep was disturbed and unstable in BDNF Met carriers (heterozygotes/homozygotes). They had higher day-to-day variability in sleep fragmentation (activity counts, wake after sleep onset, fragmentation index), sleep onset latency, and sleep duration, resulting in weekly sleep patterns that were more fragmented and less efficient. Further, BDNF genotype moderated the association between CSF t-tau and p-tau181 with day-to-day sleep duration variability, such that only Met carriers showed an association between elevated tau concentration and sleep duration variability. BDNF Met carriers had disturbed and unstable daily sleep patterns. Because the Met allele is known to decrease plasticity of neural mechanisms, the ability to achieve healthy and stable sleep may depend on such mechanisms. Thus, poorer sleep in Met carriers might be a biological mechanism by which altered BDNF activity affects tau pathology or, alternatively, accumulated AD pathology in Met carriers may disrupt sleep-wake patterns.

Osteopontin (OPN) is a secreted protein that plays pivotal roles in the recruitment and activation of immune cells, cell survival, and tissue repair following injury. OPN has been demonstrated to be increased in the cerebrospinal fluid (CSF) and brains of individuals with Alzheimer’s disease (AD). However, in order to elucidate the role of OPN in the asymptomatic stage of sporadic AD, we analyzed data from the PREVENT-AD cohort, which consists of asymptomatic individuals with a parental or multi-sibling history of AD. The Olink Proximity Extension Assay was used to measure CSF levels of OPN. CSF levels of amyloid beta (Aβ 1-42 ), and total Tau (t-Tau) were measured by enzyme-linked immunosorbent assay (Fujirebio). Participants were staged as CSF Aβ 1-42 or t-Tau positive according to specified thresholds of 989 pg/mL and 336 pg/mL, respectively. CSF levels of synaptic proteins, including GAP43, SYT1, SNAP25 and NRGN were measured by immunoprecipitation followed by mass spectrometry. Tau and Aβ positron emission tomography (PET) burdens were measured using 18 F-AV1451 and 18 F-NAV4694. Aβ(+)/Tau(-) individuals displayed a reduction in CSF OPN levels, relative to Aβ(-)/Tau(-) individuals (p = 0.001). Furthermore, Aβ(+)/Tau(+) individuals exhibited a significant increase in CSF OPN levels relative to Aβ(+)/Tau(-) individuals (p < 0.001), and at a trend level, to Aβ(-)/Tau(-) individuals (p = 0.069). In addition, CSF OPN levels were positively correlated with synaptic markers in the CSF, including GAP43 (p < 0.001), SYT1 (p = 0.001), SNAP25 (p < 0.001) and NRGN (p = 0.004). Finally, in PET imaging analyses, CSF OPN levels were positively correlated with pTau burden in the entorhinal cortex (p = 0.009), fusiform gyrus (p = 0.030) and lingual gyrus (p = 0.003). However, CSF OPN levels were not correlated with global cortical Aβ burden (p = 0.374). Our results suggest that early Aβ pathology dampens OPN levels in asymptomatic individuals with a family history of AD. Furthermore, our data provide compelling evidence that OPN plays a critical role in the compensatory response to neurofibrillary tangle formation, neuronal loss and synaptic dysfunction. Finally, our findings reveal that OPN may be a valuable therapeutic target.

Increasing evidence shows that Alzheimer’s Disease (AD) pathology, i.e., the Aß peptide, tau tangles and the APOEε4 allele, have all been associated with disrupted sleep and change in circadian rhythms. However, objective sleep measurements are often assessed over a single night. Measures of day-to-day variability might reveal unstable sleep and circadian rhythms that may reflect neurodegenerative processes. We sought to evaluate the association between AD biomarkers and sleep and circadian variability measured over a week of actigraphy. 203 dementia-free participants (age: 68.5±5.4 years, 151 women) from the PREVENT-AD cohort with known APOEε4 carrier status were tested with a week of actigraphy. Overlapping subsamples were tested for determination of cerebrospinal fluid (CSF) Aß 1-42, total t-tau and p(181)-tau (n = 100); CSF apoE protein (n = 69); and plasma Aß 1-42 (n = 144). Day-to-day variability in actigraphy circadian and sleep measures were assessed using the standard deviation of individual results. Day-to-day variability was compared between APOEε4 carriers were compared to non-carriers using t-tests. Linear regressions were performed between day-to-day variability with CSF and plasma, adjusted for age, sex, and time interval between measurements. An interaction term for APOEε4 carrier status was additionally tested in regression models. APOEε4 carriers did not differ meaningfully from non-carriers regarding sleep and circadian variability. Lower CSF Aß 1-42 was associated with higher day-to-day variability of time of morning awakening and nighttime sleep duration (ß = -0.263, p = 0.009; b = -0.206, p = 0.041). Higher plasma Aß 1-42 was also associated with higher day-to-day variability for time in bed, activity counts, sleep onset latency, sleep efficiency, and nighttime sleep duration (ß = 0.160 to 0.242; p = 0.010 to 0.002). Lower CSF apoE protein was associated with increased day-to-day variability for time of morning awakening, time in bed, activity counts, and nighttime sleep duration (ß = -0.243 to -0.420; p = 0.042 to <0.001). Higher CSF t-tau, and a trend for p(181)-tau were associated with time of morning awakening day-to-day variability inε4 carriers only (interaction p<0.001;ß = 0.330, p = 0.047; b = 0.281, p = 0.094). Sleep and circadian variability are associated with biomarkers of AD pathology and apoE metabolism. These results may suggest that unstable sleep promotes neurodegeneration or, conversely, that AD neuropathology disrupts sleep and circadian function.

Synaptic proteins in the cerebrospinal fluid (CSF) may reveal changes in the pre-symptomatic stages of Alzheimer’s disease (AD), thus may be candidate biomarkers for early detection of the disease. The PREVENT-AD cohort includes symptom-free (upon enrolment) elderly participants who are at risk of developing AD from their family history. We used enzyme-linked immunosorbent assay kits to assess CSF samples from 129 such participants for the “classical” AD biomarkers total tau, phosphorylated (181) tau and Aβ42. We also used neuroimaging data (MRI, PET) and neuropsychological assessments (MMSE, RBANS) as potential indicators disease progression. We then used in the CSF samples to measure the soluble synaptic biomarkers ADAM 22 (post-synaptic), ADAM23 (pre-synaptic). Immunoprecipitated SYT1 (pre-synaptic) from CSF were analyyzed using high-resolution selected ion monitoring analyses on a quadrupole–orbitrap mass spectrometer Q Exactive. Statistical analysis of the association of these markers with evidence of disease in analyses were done included sex and APOE e4 status as covariates. Among participants who remained cognitively unimpaired, we observed significant correlations between baseline CSF ADAM 22 levels and t- tau (R 2 = 0.22, p < 0.0001), p-tau (R 2 = 0.22, p < 0.0001), and Aβ42 (R 2 = 0.06, p = 0.01488). We also found similarly suggestive correlations also between CSF ADAM 23, CSF SYT1 and the same disease markers. Covariate analyses suggested little or no variation in the associations between these synaptic proteins with t-tau and p-tau by sex, APOE e4 status, negative PET amyloid positivity (standardized uptake value ratio ≤ 1.37) and negative CSF total tau positivity (≤ 335pg/ul). PET amyloid positivity was significantly associated with ADAM22 and p-tau interactions whereas SYT1 was significantly associated with t-tau and p-tau in CSF tau-positive participants. In linear regression analyses, baseline CSF ADAM22 levels correlated with the language cognitive performance trajectory slopes estimated over the course of 5 to 8 years on the RBANS (R 2 = 0.04, p = 0.03912). We found no significant interaction between other baseline CSF synaptic protein levels and other subscales of the RBANS. CSF synaptic protein levels show promising correlation with landmark AD proteins and emerging cognitive deficits.

CSF apolipoproteins exhibit lipid-specific relationships (signatures) with Alzheimer’s disease (AD) pathological markers and APOE -ε4 in asymptomatic individuals. Mass spectrometry-based CSF lipid analysis was performed as described before (Sampaio et al. 2011). Lipids were extracted using a one-step chloroform/methanol procedure. After extraction, resulting samples were analyzed by direct infusion on a QExactive mass spectrometer equipped with a TriVersa NanoMate ion source. Both MS and MSMS data were combined to monitor CE, DAG and TAG ions as ammonium adducts; PC, PC O-, as acetate adducts; and CL, PA, PE, PE O-, PG and PI as deprotonated anions. CSF levels of amyloid beta (Aβ 42 ), and total Tau (t-Tau) were measured by enzyme-linked immunosorbent assay (Fujirebio, Sweden) whereas apolipoproteins (AI, AII, B, CI, CII, CIII, D, E and J) concentrations were assessed using the Luminex/Biorad assays kit (10-plex magneto-fluorescent immunoassays, BioRad, USA). To characterize human CSF lipid signatures and their relationship to several apolipoproteins in pre-symptomatic AD, we profiled and analyzed 21 classes of lipid species (for a total of 796 sub-species) and 10 apolipoproteins in 120 cognitively unaffected subjects exhibiting various levels of total tau, p(181)tau and Aβ 42 . Figure 1 illustrates the signature profile (after FDR correction) following stratification by APOE-ε4 genotype at the time of recruitment, when no cognitive deficit was detected. Please note the preferential associations between phosphatidylethanolamine acetate species and apoB levels in the CSF in non-ε4 carrier. The apoD-lipid signature profile was found to be very different in ε4 versus non-ε4 carriers. Figure 2 illustrates the different associations between lipid species and the different apolipoproteins found in the CSF as a function of AD severity (stratified using the CSF T-Tau/Aβ 42 ratio). As ratio increases (top tertile) and pathology unfolds, the lipid signatures become markedly altered, with strong effects observed with apoB, apoD and apoJ interactions. Our results suggest that early amyloid and tau pathologies modulate the release of specific lipid species in the CSF which alters their relationship with apolipoproteins in an APOE-ε4-dependent manner.

It has been increasingly recognized that neuroinflammation plays an important role in the pathophysiology of Alzheimer’s disease (AD). The HIVEP3 gene encodes a transcription factor that regulates inflammatory response, and variants in this gene have been associated with increased risk for Parkinson’s disease. HIVEP3 gene expression is transiently decreased following nerve damage, consistent with a role during neuronal remodeling . In the present work, we investigate genetic variants in the HIVEP3 gene as risk factors for AD, and study HIVEP3 gene expression in human cerebral cortex. We have used three different cohorts to assess the association of HIVEP3 polymorphisms with the risk of developing AD: the International Genomics of Alzheimer’s Project (IGAP), the Quebec Founder Population Cohort (QFP) and Kunkle et al. stage 1 GWAS dataset. In the QFP cohort, we measured HIVEP3 protein levels (using ELISA) and mRNA levels (using RT-PCR) in the frontal cortex of autopsied-confirmed AD and control subjects. We have found that the rs10493098 C variant is associated with increased risk of AD in IGAP 2009 (p = 0.018, OR = 1.04), QFP (p< 5 × 10 −8 , OR = 1.37) and Kunkle et al. 2019 stage 1 IGAP GWAS (p = 0.006). In the IGAP cohort, this variant is associated with increased risk of AD only in APOE4 negative participants (p = 0.0009). Cortical HIVEP3 protein levels are increased in subjects with AD compared to controls (p = 0.029) and in subjects with at least one copy of the rs10493098 C variant compared to non-carriers (p = 0.03). There are no changes in mRNA levels as a function of disease status or presence of the rs10493098 C variant. There is no correlation between HIVEP3 protein or mRNA levels and senile plaques or neurofibrillary tangles densities. We have identified a new genetic variant associated with increased risk for AD. The HIVEP3 rs10493098 C variant is associated with increased risk of AD, particularly in APOE4 negative participants. HIVEP3 proteins levels are increased in the frontal cortex of AD subjects compared to controls and in rs10493098 C carriers.

Both short and long sleep duration have been associated with increased risk of developing Alzheimer’s Disease (AD). While short sleep has been hypothesized to be a risk factor promoting neurodegenerative processes. Long sleep has been viewed as a marker of ongoing neurodegeneration, potentially as a result of neuroinflammation. The objective of the study is to evaluate sleep patterns measured with actigraphy close to expected symptom onset in association with neuroinflammatory biomarkers. We leveraged the PREVENT-AD cohort in which participants with a parental history of sporadic AD are studied before clinical onset. 203 participants (age: 68.5±5.4 years, 151 women) free of dementia were tested with a week of actigraphy. Nighttime sleep duration, time in bed, sleep latency, sleep efficiency, and number of sleep bouts were calculated using the Actiware scoring algorithm (medium threshold). The standard deviation of these characteristics was calculated across actigraphy days to assess day-to-day variability. Years to expected onset was calculated by the number of years remaining before the age of clinical onset of a parent, or the earliest age of clinical onset if both parents developed AD. A subset of 100 participants underwent a lumbar puncture, and IL-6 and MCP-1 levels were assessed using OLINK technology in cerebrospinal fluid (CSF). The association between sleep characteristics, years to expected onset and inflammatory markers was assessed using linear regressions adjusted for age, sex, and time interval between measurements. Being closer to expected onset was associated with longer nighttime sleep duration (b = -0.19, p = 0.015) and lower sleep bouts day-to-day variability (b = 0.17, p = 0.027). Higher CSF IL-6 was associated with longer sleep duration and time in bed (b = 0.30, p = 0.006; b = 0.24, p = 0.028), whereas higher MCP-1 was associated with longer nighttime sleep duration (b = 0.25, p = 0.019). Higher CSF MCP-1 levels were associated with lower sleep bouts day-to-day variability and shorter sleep onset latency only in those within 10 years of expected onset (interaction p = 0.012 and 0.061; b = -0.31, p = 0.043; b = -0.31, p = 0.047). Proximity to parental onset of sporadic AD onset was associated with a longer sleep profile that is more consolidated and stable, which may be due to proinflammatory processes.