Alzheimer disease (AD) is the most common form of neurodegenerative disease, estimated to contribute 60–70% of all cases of dementia worldwide. According to the prevailing amyloid cascade hypothesis, amyloid-β (Aβ) deposition in the brain is the initiating event in AD, although evidence is accumulating that this hypothesis is insufficient to explain many aspects of AD pathogenesis. The discovery of increased levels of inflammatory markers in patients with AD and the identification of AD risk genes associated with innate immune functions suggest that neuroinflammation has a prominent role in the pathogenesis of AD. In this Review, we discuss the interrelationships between neuroinflammation and amyloid and tau pathologies as well as the effect of neuroinflammation on the disease trajectory in AD. We specifically focus on microglia as major players in neuroinflammation and discuss the spatial and temporal variations in microglial phenotypes that are observed under different conditions. We also consider how these cells could be modulated as a therapeutic strategy for AD. Accumulating evidence indicates important roles for microglial activation and neuroinflammation in Alzheimer disease (AD). Here, Leng and Edison describe the interplay between microglial activation and AD-related pathologies and discuss how microglial priming and activation might influence the trajectory of AD.

Neuroinflammation and microglial activation in Alzheimer disease: where do we go from here?

Background The Religious Orders Study and Rush Memory and Aging Project are both ongoing longitudinal clinical-pathologic cohort studies of aging and Alzheimer's disease (AD). Objectives To summarize progress over the past five years and its implications for understanding neurodegenerative diseases. Methods Participants in both studies are older adults who enroll without dementia and agree to detailed longitudinal clinical evaluations and organ donation. The last review summarized findings through the end of 2011. Here we summarize progress and study findings over the past five years and discuss new directions for how these studies can inform on aging and AD in the future. Results We summarize 1) findings on the relation of neurobiology to clinical AD; 2) neurobiologic pathways linking risk factors to clinical AD; 3) non-cognitive AD phenotypes including motor function and decision making; 4) the development of a novel drug discovery platform. Conclusion Complexity at multiple levels needs to be understood and overcome to develop effective treatments and preventions for cognitive decline and AD dementia.

/pdf/religious-orders-study-and-rush-memory-and-aging-project-4vya55qpey.pdf

Religious Orders Study and Rush Memory and Aging Project.

As the discovery of the Alzheimer's disease (AD) genes, APP, PSEN1, and PSEN2, in families with autosomal dominant early-onset AD (EOAD), gene discovery in familial EOAD came more or less to a standstill. Only 5% of EOAD patients are carrying a pathogenic mutation in one of the AD genes or a apolipoprotein E (APOE) risk allele e4, most of EOAD patients remain unexplained. Here, we aimed at summarizing the current knowledge of EOAD genetics and its role in ongoing approaches to understand the biology of AD and disease symptomatology as well as developing new therapeutics. Next, we explored the possible molecular mechanisms that might underlie the missing genetic etiology of EOAD and discussed how the use of massive parallel sequencing technologies triggered novel gene discoveries. To conclude, we commented on the relevance of reinvestigating EOAD patients as a means to explore potential new avenues for translational research and therapeutic discoveries.

https://alz-journals.onlinelibrary.wiley.com/doi/pdf/10.1016/j.jalz.2016.01.012

Molecular genetics of early-onset Alzheimer's disease revisited.

See Mander et al. (doi:10.1093/awx174) for a scientific commentary on this article.Sleep deprivation increases amyloid-beta, suggesting that chronically disrupted sleep may promote amyloid plaques and other downstream Alzheimer's disease pathologies including tauopathy or inflammation. To date, studies have not examined which aspect of sleep modulates amyloid-beta or other Alzheimer's disease biomarkers. Seventeen healthy adults (age 35-65 years) without sleep disorders underwent 5-14 days of actigraphy, followed by slow wave activity disruption during polysomnogram, and cerebrospinal fluid collection the following morning for measurement of amyloid-beta, tau, total protein, YKL-40, and hypocretin. Data were compared to an identical protocol, with a sham condition during polysomnogram. Specific disruption of slow wave activity correlated with an increase in amyloid-beta40 (r = 0.610, P = 0.009). This effect was specific for slow wave activity, and not for sleep duration or efficiency. This effect was also specific to amyloid-beta, and not total protein, tau, YKL-40, or hypocretin. Additionally, worse home sleep quality, as measured by sleep efficiency by actigraphy in the six nights preceding lumbar punctures, was associated with higher tau (r = 0.543, P = 0.045). Slow wave activity disruption increases amyloid-beta levels acutely, and poorer sleep quality over several days increases tau. These effects are specific to neuronally-derived proteins, which suggests they are likely driven by changes in neuronal activity during disrupted sleep.

Slow wave sleep disruption increases cerebrospinal fluid amyloid-β levels.

In the 12 years since the publication of the first Consensus Paper of the WFSBP on biomarkers of neurodegenerative dementias, enormous advancement has taken place in the field, and the Task Force t...

https://www.tandfonline.com/doi/pdf/10.1080/15622975.2017.1375556

Cerebrospinal fluid and blood biomarkers for neurodegenerative dementias: An update of the Consensus of the Task Force on Biological Markers in Psychiatry of the World Federation of Societies of Biological Psychiatry

Importance Individuals in the presymptomatic stage of Alzheimer disease (AD) are increasingly being targeted for AD secondary prevention trials. How early during the normal life span underlying AD pathologies begin to develop, their patterns of change over time, and their relationship with future cognitive decline remain to be determined. Objective To characterize the within-person trajectories of cerebrospinal fluid (CSF) biomarkers of AD over time and their association with changes in brain amyloid deposition and cognitive decline in cognitively normal middle-aged individuals. Design, Setting, and Participants As part of a cohort study, cognitively normal (Clinical Dementia Rating [CDR] of 0) middle-aged research volunteers (n = 169) enrolled in the Adult Children Study at Washington University, St Louis, Missouri, had undergone serial CSF collection and longitudinal clinical assessment (mean, 6 years; range, 0.91-11.3 years) at 3-year intervals at the time of analysis, between January 2003 and November 2013. A subset (n = 74) had also undergone longitudinal amyloid positron emission tomographic imaging with Pittsburgh compound B (PiB) in the same period. Serial CSF samples were analyzed for β-amyloid 40 (Aβ40), Aβ42, total tau, tau phosphorylated at threonine 181 (P-tau 181 ), visinin-like protein 1 (VILIP-1), and chitinase-3-like protein 1 (YKL-40). Within-person measures were plotted according to age and AD risk defined by APOE genotype (e4 carriers vs noncarriers). Linear mixed models were used to compare estimated biomarker slopes among middle-age bins at baseline (early, 45-54 years; mid, 55-64 years; late, 65-74 years) and between risk groups. Within-person changes in CSF biomarkers were also compared with changes in cortical PiB binding and progression to a CDR higher than 0 at follow-up. Main Outcomes and Measures Changes in Aβ40, Aβ42, total tau, P-tau 181 , VILIP-1, and YKL-40 and, in a subset of participants, changes in cortical PiB binding. Results While there were no consistent longitudinal patterns in Aβ40 ( P  = .001-.97), longitudinal reductions in Aβ42 were observed in some individuals as early as early middle age ( P  ≤ .05) and low Aβ42 levels were associated with the development of cortical PiB-positive amyloid plaques (area under receiver operating characteristic curve = 0.9352; 95% CI, 0.8895-0.9808), especially in mid middle age ( P 181 , and VILIP-1) dramatically increased in some individuals in mid and late middle age ( P  ≤ .02), whereas the neuroinflammation marker YKL-40 increased consistently throughout middle age ( P  ≤ .003). These patterns were more apparent in at-risk e4 carriers (Aβ42 in an allele dose-dependent manner) and appeared to be associated with future cognitive deficits as determined by CDR. Conclusions and Relevance Longitudinal CSF biomarker patterns consistent with AD are first detectable during early middle age and are associated with later amyloid positivity and cognitive decline. Such measures may be useful for targeting middle-aged, asymptomatic individuals for therapeutic trials designed to prevent cognitive decline.

https://jamanetwork.com/journals/jamaneurology/articlepdf/2368726/noi150034.pdf

Longitudinal Cerebrospinal Fluid Biomarker Changes in Preclinical Alzheimer Disease During Middle Age

properties of these proteins and the interference of matrix components make the establishment of referencematerials very challenging. As a consequence up to now, the trust in the in commercial assays is limited. Since CSF quality control samples were not broadly available. Methods: A large number of individual CSF samples were pooled to establish 5 samples with different A b 1-42 and Ab 1-40 concentrations. Different compounds were added to the pools before lyophilization. The pools underwent one freeze-thaw cycle before aliquotation (250 ml, polypropylene screw-cap tubes). All aliquots were lyophilized and stored at -20 C. The consistency and homogeneity of the prepared panel was evaluated using three different lot numbers of the assays and analysis in 3 different laboratories by different users. In addition, the performance of the proficiency panel was integrated into a multicenter study and compared to performances of neat CSF or run-validation samples (1⁄4 analyte in buffer). Results: Addition of components do not affect analytical behavior of the CSF sample. Lyophilisation of the samples was successful. Stability was considerably increased by that procedure as analytes showed only 5% CV after one week at 37 C. Neat CSF, with and without the additives, as well as samples from the proficiency panel, showed a very good parallelism (1⁄4 absence of matrix interference in the assays) upon dilution for the three analytes evaluated in the study. The production process did not change the intrinsic characteristics of the CSF samples. Overall variability in a multicenter study for the proficiency panel did not exceed > 10%, including the sum of % CVof intra-run, inter-run, inter-operator, and inter-lab. Conclusions: A panel of 5 stabilized and lyophilized CSF samples with target values covering the whole range of the calibration curve of the A b 1-42 , Ab 1-40 and Total-Tau ELISA. The excellent precision data obtained in a multicenter study make this panel an excellent new tool to verify the quality of the biomarker measurements in research settings, but also for routine labs. In the absence of an international reference standard, this commercially available proficiency panel may significantly increase the trust in the values measured by ELISA of CSF diagnostics.

Improvements to innotest® htau ag

replicates and technical replicates were analyzed for 3 AD and 3 non-AD over ten consecutive days. For the vast majority of the peptides CVs were <5%. The second, 6 AD and 6 non-AD, indicated slightly increased levels of cystatin C, beta-2-microglobulin, and APP, as well as clearly increased levels of chromogranin A, secretogranin-2, and neurosecretory protein VGF for AD. Moreover, for complex samples the advantage of high resolution instrumentation became evident because of the superior possiblity to avoid signal interferences. Conclusions: The assay is reproducible and consumes little amount per analysis. Preliminary results should be interpreted with caution due to the limited sample material. Data from a larger study, using clinically well characterized samples, is under way and will be presented.

Heather Darby

Papers

Longitudinal Cerebrospinal Fluid Biomarker Changes in Preclinical Alzheimer Disease During Middle Age

Improvements to innotest® htau ag

Improvements to innotest® phospho-tau 181p

Improvements to innotest® b-amyloid 1-42