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[...]a substantial increase in long-term funding for multidisciplinary research programmes is absolutely essential to reduce the burden of individual suffering and the enormous societal cost of AD. In 2015, almost 47 million people worldwide were estimated to be affected by dementia, and the numbers are expected to reach 75 million by 2030, and 131 million by 2050, with the greatest increase expected in low-income and middle-income countries.2 In 2012 and 2015, the World Health Organization (WHO) presented reports in which it acknowledged this trend--sometimes described in terms of a fast-growing epidemic--and concluded that AD and other dementias should be regarded as a global public health priority.3,4 Similar policy declarations have been made by the European Union5 (EU) and by some individual countries. Care for people with dementia is provided by several sectors in society, with the social-care (long-term care and home services) and informal-care (provided by non-professional caregivers) sectors accounting for the greatest proportion of costs--even greater than the cost of direct medical care.6 In cost-of-illness studies, total societal cost estimates for dementia in Europe in 2010 were between $238·6 billion6 and [euro]105·6 billion.7 The economic costs of caring for a growing number of people with AD and other dementias are formidable, but the combined economic and societal burden of dementia is more daunting still, corresponding to the aggregate burden of people with dementia and their next of kin.

Practice effects (PE) defined as an improvement of performance in cognition due to repeated assessments between sessions is well known in unimpaired individuals, while less is known about impaired cognition and particularly in latent brain disease as autosomal-dominant Alzheimer’s disease. The purpose was to evaluate the general (across tests/domains) and domain-specific PE calculated as Annual Rate of Change (ARC) in relation to years to the estimated disease onset (YECO) and in four groups of AD: asymptomatic mutation carriers (aAD, n=19), prodromal, i.e. ,symptomatic mutation carriers, criteria for AD diagnosis not fulfilled (pAD, n=4) and mutation carriers diagnosed with AD (dAD, n=6) as well as mutation non-carriers from the AD families serving as a healthy controlhealthy comparison groups (HC, n=35). Cognition was assessed at baseline and follow-up about three years later by 12 tests covering six domains. The aAD and HC groups were comparable at baseline in demographic characteristics (age, gender, and education), when they were in the early 40ies, while the pAD and dAD groups were older and cognitively impaired. The results on mean ARC for the four groups were significantly different, small, positive, and age-insensitive in the HC group, while ARC was negative and declining with time/disease advancement in AD. The differences between HC and aAD groups in mean ARC and domain-specific ARC were not significant indicating a subtle PE in aAD in the early preclinical stage of AD. In symptomatic stages of AD, there was no PE probably due to cognitive disease-related progression. PE was largest in the verbal domain in both the HC and aAD groups indicating a relationship with cognitive vulnerability. The group-related difference in mean ARC was predominant in timekeeping tests. To conclude, the practice effect in over three years was suggested to be linked to procedural learning and memory/adaption to cognitive demands.

It is well-established that subcompartments of endoplasmic reticulum (ER) are in physical contact with the mitochondria. These lipid raft-like regions of ER are referred to as mitochondria-associated ER membranes (MAMs), and they play an important role in, for example, lipid synthesis, calcium homeostasis, and apoptotic signaling. Perturbation of MAM function has previously been suggested in Alzheimer’s disease (AD) as shown in fibroblasts from AD patients and a neuroblastoma cell line containing familial presenilin-2 AD mutation. The effect of AD pathogenesis on the ER–mitochondria interplay in the brain has so far remained unknown. Here, we studied ER–mitochondria contacts in human AD brain and related AD mouse and neuronal cell models. We found uniform distribution of MAM in neurons. Phosphofurin acidic cluster sorting protein-2 and σ1 receptor, two MAM-associated proteins, were shown to be essential for neuronal survival, because siRNA knockdown resulted in degeneration. Up-regulated MAM-associated proteins were found in the AD brain and amyloid precursor protein (APP) Swₑ/Lₒₙ mouse model, in which up-regulation was observed before the appearance of plaques. By studying an ER–mitochondria bridging complex, inositol-1,4,5-triphosphate receptor–voltage-dependent anion channel, we revealed that nanomolar concentrations of amyloid β-peptide increased inositol-1,4,5-triphosphate receptor and voltage-dependent anion channel protein expression and elevated the number of ER–mitochondria contact points and mitochondrial calcium concentrations. Our data suggest an important role of ER–mitochondria contacts and cross-talk in AD pathology.

Studying autosomal dominant Alzheimer’s disease (ADAD), caused by gene mutations yielding nearly complete penetrance and a distinct age of symptom onset, allows investigation of presymptomatic pathological processes that can identify a therapeutic window for disease-modifying therapies. Astrocyte activation may occur in presymptomatic Alzheimer’s disease (AD) because reactive astrocytes surround β-amyloid (Aβ) plaques in autopsy brain tissue. Positron emission tomography was performed to investigate fibrillar Aβ, astrocytosis and cerebral glucose metabolism with the radiotracers 11 C-Pittsburgh compound-B (PIB), 11 C-deuterium-L-deprenyl (DED) and 18 F-fluorodeoxyglucose (FDG) respectively in presymptomatic and symptomatic ADAD participants (n = 21), patients with mild cognitive impairment (n = 11) and sporadic AD (n = 7). Multivariate analysis using the combined data from all radiotracers clearly separated the different groups along the first and second principal components according to increased PIB retention/decreased FDG uptake (component 1) and increased DED binding (component 2). Presymptomatic ADAD mutation carriers showed significantly higher PIB retention than non-carriers in all brain regions except the hippocampus. DED binding was highest in presymptomatic ADAD mutation carriers. This suggests that non-fibrillar Aβ or early stage plaque depostion might interact with inflammatory responses indicating astrocytosis as an early contributory driving force in AD pathology. The novelty of this finding will be investigated in longitudinal follow-up studies.

Background Plasma assays for the detection of Alzheimer’s disease neuropathological changes are receiving ever increasing interest. The concentration of plasma glial fibrillary acidic protein (GFAP) has been suggested as a potential marker of astrocytes or recently, amyloid-β burden, although this hypothesis remains unproven. We compared plasma GFAP levels with the astrocyte tracer 11 C-Deuterium-L-Deprenyl ( 11 C-DED) in a multi-modal PET design in participants with sporadic and Autosomal Dominant Alzheimer’s disease. Methods Twenty-four individuals from families with known Autosomal Dominant Alzheimer’s Disease mutations (mutation carriers = 10; non-carriers = 14) and fifteen patients with sporadic Alzheimer’s disease were included. The individuals underwent PET imaging with 11 C-DED, 11 C-PIB and 18 F-FDG, as markers of reactive astrogliosis, amyloid-β deposition, and glucose metabolism, respectively, and plasma sampling for measuring GFAP concentrations. Twenty-one participants from the Autosomal Dominant Alzheimer’s Disease group underwent follow-up plasma sampling and ten of these participants underwent follow-up PET imaging. Results In mutation carriers, plasma GFAP levels and 11 C-PIB binding increased, while 11 C-DED binding and 18 F-FDG uptake significantly decreased across the estimated years to symptom onset. Cross-sectionally, plasma GFAP demonstrated a negative correlation with 11 C-DED binding in both mutation carriers and patients with sporadic disease. Plasma GFAP indicated cross-sectionally a significant positive correlation with 11 C-PIB binding and a significant negative correlation with 18 F-FDG in the whole sample. The longitudinal levels of 11 C-DED binding showed a significant negative correlation with longitudinal plasma GFAP concentrations over the follow-up interval. Conclusions Plasma GFAP concentration and astrocyte 11 C-DED brain binding levels followed divergent trajectories and may reflect different underlying processes. The strong negative association between plasma GFAP and 11 C-DED binding in Autosomal Dominant and sporadic Alzheimer’s disease brains may indicate that if both are markers of reactive astrogliosis, they may detect different states or subtypes of astrogliosis. Increased 11 C-DED brain binding seems to be an earlier phenomenon in Alzheimer’s disease progression than increased plasma GFAP concentration.

Copy number variation (CNV) of the amyloid-β precursor protein gene ( APP ) is a known cause of autosomal dominant Alzheimer disease (ADAD), but de novo genetic variants causing ADAD are rare. We report a mother and daughter with neuropathologically confirmed definite Alzheimer disease (AD) and extensive cerebral amyloid angiopathy (CAA). Copy number analysis identified an increased number of APP copies and genome sequencing (GS) revealed the underlying complex genomic rearrangement (CGR) including a triplication of APP with two unique breakpoint junctions (BPJs). The mosaic state in the mother had likely occurred de novo . Digital droplet PCR (ddPCR) on 42 different tissues, including 17 different brain regions, showed the derivative chromosome at varying mosaic levels (20–96%) in the mother who had symptom onset at age 58 years. In contrast, the derivative chromosome was present in all analyzed cells in the daughter whose symptom onset was at 34 years. This study reveals the architecture of a de novo CGR causing APP triplication and ADAD with a striking difference in age at onset between the fully heterozygous daughter compared to the mosaic mother. The GS analysis identified the complexity of the CGR illustrating its usefulness in identifying structural variants (SVs) in neurodegenerative disorders.

Recent findings have shown that the connectivity and crosstalk between mitochondria and the endoplasmic reticulum (ER) at mitochondria–ER contact sites (MERCS) are altered in Alzheimer’s disease (AD) and in AD-related models. MERCS have been related to the initial steps of autophagosome formation as well as regulation of mitochondrial function. Here, the interplay between MERCS, mitochondria ultrastructure and function and autophagy were evaluated in different AD animal models with increased levels of Aβ as well as in primary neurons derived from these animals. We start by showing that the levels of Mitofusin 1, Mitofusin 2 and mitochondrial import receptor subunit TOM70 are decreased in post-mortem brain tissue derived from familial AD. We also show that Aβ increases the juxtaposition between ER and mitochondria both in adult brain of different AD mouse models as well as in primary cultures derived from these animals. In addition, the connectivity between ER and mitochondria are also increased in wild-type neurons exposed to Aβ. This alteration in MERCS affects autophagosome formation, mitochondrial function and ATP formation during starvation. Interestingly, the increment in ER–mitochondria connectivity occurs simultaneously with an increase in mitochondrial activity and is followed by upregulation of autophagosome formation in a clear chronological sequence of events. In summary, we report that Aβ can affect cell homeostasis by modulating MERCS and, consequently, altering mitochondrial activity and autophagosome formation. Our data suggests that MERCS is a potential target for drug discovery in AD.

Direct conversion of human fibroblasts into mature and functional neurons, termed induced neurons (iNs), was achieved for the first time 6 years ago. This technology offers a promising shortcut for obtaining patient‐ and disease‐specific neurons for disease modeling, drug screening, and other biomedical applications. However, fibroblasts from adult donors do not reprogram as easily as fetal donors, and no current reprogramming approach is sufficiently efficient to allow the use of this technology using patient‐derived material for large‐scale applications. Here, we investigate the difference in reprogramming requirements between fetal and adult human fibroblasts and identify REST as a major reprogramming barrier in adult fibroblasts. Via functional experiments where we overexpress and knockdown the REST‐controlled neuron‐specific microRNAs miR‐9 and miR‐124, we show that the effect of REST inhibition is only partially mediated via microRNA up‐regulation. Transcriptional analysis confirmed that REST knockdown activates an overlapping subset of neuronal genes as microRNA overexpression and also a distinct set of neuronal genes that are not activated via microRNA overexpression. Based on this, we developed an optimized one‐step method to efficiently reprogram dermal fibroblasts from elderly individuals using a single‐vector system and demonstrate that it is possible to obtain iNs of high yield and purity from aged individuals with a range of familial and sporadic neurodegenerative disorders including Parkinson's, Huntington's, as well as Alzheimer's disease. Synopsis REST inhibition removes neuronal reprogramming barrier in adult dermal fibroblasts. The resulting high number of induced neurons from elderly patients allows for large scale biomedical applications such as disease modeling, drug screening and early and/or differential diagnostics. The most commonly used neural conversion genes Ascl1 and Brn2 elicit largely distinct transcriptional responses between fetal and adult fibroblasts. REST inhibition removes reprogramming barrier of adult fibroblasts. The effect of RESTi is only partially mediated via the neuron specific microRNAs miR‐9 and miR‐124 up‐regulation. In addition to activate a similar subset of neuronal genes as miR‐9 and miR‐124 overexpression, RESTi activates a distinct set of neuronal genes. An all‐in‐one conversion vector overexpressing Ascl1 and Brn2 and knocking down REST improves the reprogramming process and renders it suitable for biomedical applications. Graphical Abstract REST inhibition removes neuronal reprogramming barrier in adult dermal fibroblasts. The resulting high number of induced neurons from elderly patients allows for large scale biomedical applications such as disease modeling, drug screening and early and/or differential diagnostics.

Amyloids are fibrillar protein aggregates associated with diseases such as Alzheimer's disease (AD), Parkinson's disease (PD), type II diabetes and Creutzfeldt-Jakob disease. The process of amyloid polymerization involves three pathological protein transformations; from natively folded conformation to the cross-β conformation, from biophysically soluble to insoluble, and from biologically functional to non-functional. While amyloids share a similar cross-β conformation, the biophysical transformation can either take place spontaneously via a homogeneous nucleation mechanism (HON) or catalytically on an exogenous surface via a heterogeneous nucleation mechanism (HEN). Here, we postulate that the different nucleation pathways can serve as a mechanistic basis for an etiological classification of amyloidopathies, where hereditary forms generally follow the HON pathway, while sporadic forms follow seed-induced (prions) or surface-induced (including microbially induced) HEN pathways. Critically, the conformational and biophysical amyloid transformation results in loss-of-function (LOF) of the original natively folded and soluble protein. This LOF can, at least initially, be the mechanism of amyloid toxicity even before amyloid accumulation reaches toxic levels. By highlighting the important role of non-protein species in amyloid formation and LOF mechanisms of toxicity, we propose a generalized mechanistic framework that could help better understand the diverse etiology of amyloid diseases and offer new opportunities for therapeutic interventions, including replacement therapies.