Greg Kennedy, Roy J. Hardman, Helen Macpherson, Andrew B. Scholey, Andrew Pipingas
How Does Exercise Reduce the Rate of Age-Associated Cognitive Decline? A Review of Potential Mechanisms
Abstract: The rate of age-associated cognitive decline varies considerably between individuals. It is important, both on a societal and individual level, to investigate factors that underlie these differences in order to identify those which might realistically slow cognitive decline. Physical activity is one such factor with substantial support in the literature. Regular exercise can positively influence cognitive ability, reduce the rate of cognitive aging, and even reduce the risk of Alzheimer’s disease (AD) and other dementias. However, while there is substantial evidence in the extant literature for the effect of exercise on cognition, the processes that mediate this relationship are less clear. This review examines cardiovascular health, production of brain derived neurotrophic factor (BDNF), insulin sensitivity, stress, and inflammation as potential pathways, via which exercise may maintain or improve cognitive functioning, and may be particularly pertinent in the context of the aging brain. A greater understanding of these mechanisms and their potential relationships with exercise and cognition will be invaluable in providing biomarkers for investigating the efficacy of differing exercise regimes on cognitive outcomes.
Stephen P. Arnerić, Richard Batrla-Utermann, Laurel Beckett, Tobias Bittner, Kaj Blennow, Leslie Carter, Robert Dean, Sebastiaan Engelborghs, Just Genius, Mark Forrest Gordon, Janice Hitchcock, June Kaplow, Johan Luthman, Richard Meibach, David Raunig, Klaus Romero, Mahesh N. Samtani, Mary Savage, Leslie Shaw, Diane Stephenson, Robert M. Umek, Hugo Vanderstichele, Brian Willis, Susan Yule Note: Authors listed in alphabetical order
Cerebrospinal Fluid Biomarkers for Alzheimer’s Disease: A View of the Regulatory Science Qualification Landscape from the Coalition Against Major Diseases CSF Biomarker Team
Abstract: Alzheimer’s disease (AD) drug development is burdened with the current requirement to conduct large, lengthy, and costly trials to overcome uncertainty in patient progression and effect size on treatment outcome measures. There is an urgent need for the discovery, development, and implementation of novel, objectively measured biomarkers for AD that would aid selection of the appropriate subpopulation of patients in clinical trials, and presumably, improve the likelihood of successfully evaluating innovative treatment options. Amyloid deposition and tau in the brain, which are most commonly assessed either in cerebrospinal fluid (CSF) or by molecular imaging, are consistently and widely accepted. Nonetheless, a clear gap still exists in the accurate identification of subjects that truly have the hallmarks of AD. The Coalition Against Major Diseases (CAMD), one of 12 consortia of the Critical Path Institute (C-Path), aims to streamline drug development for AD and related dementias by advancing regulatory approved drug development tools for clinical trials through precompetitive data sharing and adoption of consensus clinical data standards. This report focuses on the regulatory process for biomarker qualification, briefly comments on how it contrasts with approval or clearance of companion diagnostics, details the qualifications currently available to the field of AD, and highlights the current challenges facing the landscape of CSF biomarkers qualified as hallmarks of AD. Finally, it recommends actions to accelerate regulatory qualification of CSF biomarkers that would, in turn, improve the efficiency of AD therapeutic development.
Denis Cuccaro, Elvira Valeria De Marco, Rita Cittadella, Sebastiano Cavallaro (Handling Associate Editor: Dominique Campion)
Copy Number Variants in Alzheimer’s Disease
Abstract: Alzheimer’s disease (AD) is a devastating disease mainly afflicting elderly people, characterized by decreased cognition, loss of memory, and eventually death. Although risk and deterministic genes are known, major genetics research programs are underway to gain further insights into the inheritance of AD. In the last years, in particular, new developments in genome-wide scanning methodologies have enabled the association of a number of previously uncharacterized copy number variants (CNVs, gain or loss of DNA) in AD. Because of the exceedingly large number of studies performed, it has become difficult for geneticists as well as clinicians to systematically follow, evaluate, and interpret the growing number of (sometime conflicting) CNVs implicated in AD. In this review, after a brief introduction of this type of structural variation, and a description of available databases, computational analyses, and technologies involved, we provide a systematic review of all published data showing statistical and scientific significance of pathogenic CNVs and discuss the role they might play in AD.
Joery Goossens*, Jorne Laton*, Jeroen Van Schependom, Jeroen Gielen, Hanne Struyfs, Sara Van Mossevelde, Tobi Van den Bossche, Johan Goeman, Peter Paul De Deyn, Anne Sieben, Jean-Jacques Martin, Christine Van Broeckhoven, Julie van der Zee, Sebastiaan Engelborghs§, Guy Nagels§ *These authors contributed equally to this work. §Joint last authors
EEG Dominant Frequency Peak Differentiates Between Alzheimer’s Disease and Frontotemporal Lobar Degeneration
Abstract: We investigated the power of EEG as biomarker in differential diagnosis of Alzheimer’s disease (AD) and frontotemporal lobar degeneration (FTLD). EEG was recorded from 106 patients with AD or FTLD, of which 37 had a definite diagnosis, and 40 controls. Dominant frequency peaks were extracted for all 19 channels, for each subject. The average frequency of the largest dominant frequency peaks (maxpeak) was significantly lower in AD than FTLD patients and controls. Based on ROC analysis, classification could be made with diagnostic accuracy of 78.4%. Our findings show that quantitative analysis of EEG maxpeak frequency is an easy and useful measure for differential dementia diagnosis.
Pier Paolo Sainaghi, Mattia Bellan, Franco Lombino, Fedreica Alciato, Miryam Carecchio, Daniela Galimberti, Chaira Fenoglio, Elio Scarpini, Roberto Cantello, Mario Pirisi, Comi Comi (Handling Associate Editor: Marco Bozzali)
Growth Arrest Specific 6 Concentration is Increased in the Cerebrospinal Fluid of Patients with Alzheimer's Disease
Abstract: Growth arrest specific 6 (Gas6) has neurotrophic and neuroinflammatory functions, and may play a role in Alzheimer’s disease (AD). In keeping with this hypothesis, we observed that cerebrospinal fluid (CSF) Gas6 is increased in AD patients compared to controls (63 versus 67 subjects; median value 13.3 versus 9.1 ng/ml; p<0.0001). Thereafter, we assessed whether CSF Gas6 concentration was correlated to the following parameters: disease duration, MMSE score two years after clinical diagnosis, AD CSF biomarkers, and years of formal schooling. We detected an inverse correlation between CSF Gas6 levels at diagnosis and both disease duration (p<0.0001) and decrease in the MMSE score two years later (p< 0.0001). Conversely, we found no correlation between CSF Gas6 and both AD biomarkers and years of formal schooling. In conclusion, our results suggest that upregulation of CSF Gas6 may be part of a defensive response aimed at counteracting AD progression.
Yoshihisa Kitamura, Masatoshi Inden, Yasuto Kimoto, Kazuyuki Takata, Daijiro Yanagisawa, Masanori Hijioka, Eishi Ashihara, Ikuo Tooyama, Shun Shimohama, Hiroyoshi Ariga (Handling Associate Editor: Koji Abe)
Effects of a DJ-1-Binding Compound on Spatial Learning and Memory Impairment in a Mouse Model of Alzheimer’s Disease
Abstract: Previously, DJ-1 modulator UCP0054278/comp-B was identified by virtual screening, where comp-B interacts with DJ-1 to produce antioxidant and neuroprotective responses in Parkinson’s disease models. However, the effect of comp-B in an in vivo Alzheimer’s disease (AD) model is yet undetermined. Thus, we examined the effect of comp-B on spatial learning, memory, and amyloid-β (Aβ) clearance in a transgenic mouse model of AD. We found that comp-B resolved the cognitive deficits, reduced insoluble Aβ42 levels, and prevented the degeneration of synaptic functions, thereby suggesting that comp-B may become a major compound for AD treatment.
Akihiko Nunomura, Xiongwei Zhu, George Perry (Handling Editor: Jesús Ávila)
Modulation of Parkinson’s Disease associated Protein Rescues Alzheimer’s Disease Degeneration
Abstract: DJ-1, a causative gene product of an autosomal recessive familial form of Parkinson’s disease (PD), plays roles in reducing oxidative stress and transcriptional regulation. Loss of its function is thought to result in the onset of PD. DJ-1 has been demonstrated to show general cytoprotective function mainly through antioxidant properties and possibly regulates the extent of stroke-induced damage and neurodegeneration in Alzheimer’s disease (AD). The paper, " Effects of a DJ-1-Binding Compound on Spatial Learning and Memory Impairment in a Mouse Model of Alzheimer’s Disease", by Kitamura et al. in this issue of Journal of Alzheimer's Disease reports that a DJ-1 modulator UCP0054278/compound B (comp-B), which has been previously shown to exhibit antioxidant and neuroprotective properties in PD models, can prevent neurodegenerative changes and cognitive dysfunction in an animal model of AD. Indeed, comp-B reduces not only α-synuclein but also insoluble Aβ42 levels, prevents the reductions in synaptophysin and drebrin, and rescues cognitive deficits in transgenic APdE9 mice model of AD. It is noteworthy that pharmacological modulation of a familial PD gene product is sufficient to modify biochemical phenotypes and cognitive performance in amyloid-based genetically driven mouse models of AD. Together with mixed pathology in the vast majority of the patients with late-onset dementia, these findings strongly suggest the existence of common pathogenesis of diverse neurodegenerative disorders. Anti-oxidative strategy such as DJ-1 modulation is one of the major candidates to address the common pathogenesis and should be assembled among multimodal or combinatory interventions against neurodegenerative disorders.
Peifen Chang*, Xin Li*, Chao Ma*, Sisi Zhang, Zhen Liu, Kewei Chen Lin Ai#, Jingling Chang,#, Zhanjun Zhang *These authors contributed equally to this work.
The Effects of an APOE Promoter Polymorphism on Human White Matter Connectivity during Non-Demented Aging
Abstract: Polymorphisms of the apolipoprotein E (APOE) promoter rs405509 are related to Alzheimer’s disease (AD). The T/T allele of rs405509 decreases the transcription of the APOE gene and leads to impairments in a specific brain structural network in aged individuals; thus, it is an important risk factor for AD. However, it remains unknown whether rs405509 affects white matter networks during aging. Here, we investigated the effect of the rs405509 genotype (T/T versus G-allele) on age-related brain white matter structural networks via construction of the graph theory-based structural connectome using diffusion MRI data in a large cohort. Network communication efficiency was quantified, along with the network’s betweenness centrality (Bc), global efficiency, local efficiency, and shortest path length. Regarding cognition, TT carriers had significant negative correlations between age and memory performance and between age and executive functions. A network analysis showed that TT carriers had an accelerated age-related loss of Bc and that regional Bc decreased in the left inferior frontal gyrus pars opercularis, the left posterior cingulate cortex, the right inferior occipital gyrus (IOG.R), and the left angular gyrus (ANG.L). Additional brain-behavior relationship analyses showed that polymorphism of rs405509 and age have strong interaction effects on the association of nodal Bc and cognition, mainly in the IOG.R and ANG.L. These results demonstrate that the rs405509 T/T allele of APOE causes an age-related cognitive decline in non-demented elderly people, possibly by modulating brain network communication efficiency, which may be beneficial for understanding the neural mechanisms of rs405509-related cognitive aging and AD pathogenesis.
Peter J. Fried, Lukas Schilberg, Anna-Katharine Brem, Sadhvi Saxena, Bonnie Wong, Aaron M. Cypess, Edward S. Horton, Alvaro Pascual-Leone
Humans with Type-2 Diabetes Show Abnormal Long-Term Potentiation-Like Cortical Plasticity Associated with Verbal Learning Deficits
Abstract: Background. Type-2 diabetes mellitus (T2DM) accelerates cognitive aging and increases risk of Alzheimer’s disease. Rodent models of T2DM show altered synaptic plasticity associated with reduced learning and memory. Humans with T2DM also show cognitive deficits, including reduced learning and memory, but the relationship of these impairments to the efficacy of neuroplastic mechanisms has never been assessed. Objective. Our primary objective was to compare mechanisms of cortical plasticity in humans with and without T2DM. Our secondary objective was to relate plasticity measures to standard measures of cognition. Methods. A prospective cross-sectional cohort study was conducted on 21 adults with T2DM and 15 demographically-similar non-diabetic controls. Long-term potentiation-like plasticity was assessed in primary motor cortex by comparing the amplitude of motor evoked potentials (MEPs) from single-pulse transcranial magnetic stimulation before and after intermittent theta-burst stimulation (iTBS). Plasticity measures were compared between groups and related to neuropsychological scores. Results. In T2DM, iTBS-induced modulation of MEPs was significantly less than controls, even after controlling for potential confounds. Furthermore, in T2DM, modulation of MEPs 10-min post-iTBS was significantly correlated with Rey Auditory Verbal Learning Task (RAVLT) performance. Conclusion. Humans with T2DM show abnormal cortico-motor plasticity that is correlated with reduced verbal learning. Since iTBS after-effects and the RAVLT are both NMDA receptor-dependent measures, their relationship in T2DM may reflect brain-wide alterations in the efficacy of NMDA receptors. These findings offer novel mechanistic insights into the brain consequences of T2DM and provide a reliable means to monitor brain health and evaluate the efficacy of clinical interventions.
Ingrid H. Philippens*, Paul R. Ormel*, Guus Baarends, Maja Johansson, Ed J. Remarque, Magnus Doverskog *These authors contributed equally to this work.
Acceleration of Amyloidosis by Inflammation in the Amyloid-Beta Marmoset Monkey Model of Alzheimer’s Disease
Abstract: Background: The immune system is increasingly mentioned as a potential target for Alzheimer’s disease (AD) treatment. Objective: In the present pilot study, the effect of (neuro)inflammation on amyloidopathy was investigated in the marmoset monkey, which has potential as an AD animal model due to its natural cerebral amyloidosis similar to humans. Methods: Six adult/aged marmosets (Callithrix jacchus) were intracranial injected with amyloid-beta (Aβ) fibrils at three cortical locations in the right hemisphere. Additionally, in half of the monkeys, lipopolysaccharide (LPS) was co-injected with the Aβ fibrils and injected in the other hemisphere without Aβ fibrils. The other three monkeys received phosphate buffered saline instead of LPS, as a control for the inflammatory state. The effect of inflammation on amyloidopathy was also investigated in an additional monkey that suffered from the chronic inflammatory wasting syndrome. Mirror histology sections were analyzed to assess amyloidopathy and immune reaction, and peripheral blood for AD biomarker expression. Results: All LPS-injected monkeys showed an early AD immune blood cell expression profile on CD95 and CD45RA. Two out of three monkeys injected with Aβ and LPS and the additional monkey, suffering from chronic inflammation, developed plaques. None of the controls, injected with Aβ only, developed any plaques. Conclusion: This study shows the importance of immune modulation on the susceptibility for amyloidosis, a hallmark of AD, which offers new perspectives for disease modifying approaches in AD.
Alexandre Dal-Pan, Stéphanie Dudonné, Philippe Bourassa, Morgane Bourdoulous, Cyntia Tremblay, Yves Desjardins, Frédéric Calon, on behalf of the Neurophenols consortium (Handling Associate Editor: Othman Ghribi)
Cognitive-Enhancing Effects of a Polyphenols-Rich Extract from Fruits without Changes in Neuropathology in an Animal Model of Alzheimer's Disease
Abstract: No effective preventive treatment is available for age-related cognitive decline and Alzheimer's disease (AD). Epidemiological studies indicate that a diet rich in fruit is associated with cognitive improvement. It was thus proposed that high polyphenol concentrations found in berries can prevent cognitive impairment associated with aging and AD. Therefore, the Neurophenols project aimed at investigating the effects of a polyphenolic extract from blueberries and grapes (PEBG) in the triple-transgenic (3xTg-AD) mouse model of AD, which develops AD neuropathological markers, including amyloid-β plaques and neurofibrillary tangles, leading to memory deficits. In this study, 12-month-old 3xTg-AD and NonTg mice were fed a diet supplemented with standardized PEBG (500 or 2500 mg/kg) for 4 months (n=15-20/group). A cognitive evaluation with the novel object recognition test was performed at 15 months of age and mice were sacrificed at 16 months of age. We observed that PEBG supplementation with doses of 500 or 2500 mg/kg prevented the decrease in novel object recognition observed in both 15-month-old 3xTg-AD mice and NonTg mice fed a control diet. Although PEBG treatment did not reduce Aβ and tau pathologies, it prevented the decrease in mature BDNF observed in 16-month-old 3xTg-AD mice. Finally, plasma concentrations of phenolic metabolites, such as dihydroxyphenyl valerolactone, a microbial metabolite of epicatechin, positively correlated with memory performances in supplemented mice. The improvement in object recognition observed in 3xTg-AD mice after PEBG administration supports the consumption of polyphenols-rich extracts to prevent memory impairment associated with age-related disease, without significant effects on classical AD neuropathology.
Hang-Rai Kim*, Young Ho Park*, Jae-Won Jang, So Young Park, Min Jeong Wang, Min Jae Baek, Beom Joon Kim, Soyeon Ahn, SangYun Kim *These authors contributed equally to this work.
Visual Rating of Posterior Atrophy as a Marker of Progression to Dementia in Mild Cognitive Impairment Patients
Abstract: Background: Although medial temporal atrophy (MTA) is a useful imaging marker of the progression to dementia in mild cognitive impairment (MCI), substantial numbers of MCI patients without MTA still progress to dementia. Objective: We investigated whether visual ratings of posterior atrophy (PA) on magnetic resonance imaging show independent predictive value for the progression to dementia in MCI patients. Methods: This was a retrospective cohort study of elderly patients who visited Seoul National University Bundang Hospital between 2004 and 2012. A total of 148 patients who were initially diagnosed with MCI were followed for up to 3 years (median 22 months) to determine whether they progressed to dementia. We used 4-point and 5-point visual rating scales to assess PA and MTA, respectively. PA and MTA scores were dichotomized into normal (no atrophy) or abnormal (atrophy) in each patient. We performed a Cox regression analysis to examine the hazard ratios (HRs) of PA and MTA for the progression to dementia with adjustment for age, APOE ε4 allele status, and baseline Mini-Mental State Examination score. Results: Among the study population, 47 patients progressed to dementia. Visual assessment of the MRI scans revealed that 67 patients (45.3%) showed PA, whereas 85 patients (57.3%) showed MTA. The HRs with 95% confidence intervals for PA and MTA were 2.516 (1.244-5.091) and 4.238 (1.680-10.687), respectively. The predictive values of visually assessed PA and MTA remained significant, independent of the covariates. Conclusion: Visual assessment of PA has independent predictive value for progression to dementia in MCI patients.
Irina Gureviciene, Kestutis Gurevicius, Ekaterina Mugantseva, Mikhail Kislin, Leonard Khiroug, Heikki Tanila
Amyloid Plaques Show Binding Capacity of Exogenous Injected Amyloid-β
Abstract: Amyloid plaques, although inducing damage to the immediately surrounding neuropil, have been proposed to provide a relatively innocuous way to deposit toxic soluble amyloid-β (Aβ) species. Here we address this hypothesis by exploring spread and absorption of fluorescent Aβ to pre-existing amyloid plaques after local application in wild-type mice versus APP/PS1 transgenic mice with amyloid plaques. Local intracortical or intracerebroventricular injection of fluorescently-labeled Aβ in APP/PS1 mice with a high plaque density resulted in preferential accumulation of the peptide in amyloid plaques in both conventional postmortem histology and in live imaging using two-photon microscopy. These findings support the contention that amyloid plaques may act as buffers to protect neurons from the toxic effects of momentary high concentrations of soluble Aβ oligomers.
Piotr Lewczuk, Natalia Lelental, Ingolf Lachmann, Max Holzer, Katharina Flach, Sebastian Brandner, Sebastiaan Engelborghs, Charlotte E. Teunissen, Henrik Zetterberg, José Luis Molinuevo, Barbara Mroczko, Kaj Blennow, Julius Popp, Lucilla Parnetti, Davide Chiasserini, Armand Perret-Liaudet, Philipp Spitzer, Juan Manuel Maler, Johannes Kornhuber (Handling Associate Editor: Daniela Galimberti)
Non-Phosphorylated Tau as a Potential Biomarker of Alzheimer's Disease: Analytical and Diagnostic Characterization
Abstract: Background: Virtually nothing is known about a potential diagnostic role of non-phospho-epitopes of Tau (Non-P-Tau) in cerebrospinal fluid (CSF). Objective: To establish and analytically and clinically characterize the first assay capable to measure concentrations of Non-P-Tau in human CSF. Methods: An antibody (1G2) was developed that selectively binds to the Tau molecule non-phosphorylated at the positions T175, T181, and T231, and was used in establishing a sandwich ELISA capable to measure Non-P-Tau in human CSF, following analytical and clinical validation of the method. Results: The 1G2 antibody shows decreasing reactivity to tau peptides containing phosphorylation at positions T175, T181, and T231. Detection limit of the assay is 25 pg/ml; the coefficients of variation (CVs) of the optical densities of the repeated standard curves were between 3.6-15.9%. Median intra-assay imprecision of double measurements was 4.8%; inter-assay imprecision was in the range of 11.2%-15.3%. Non-P-Tau concentrations are stable in the CSF samples sent to distinct laboratories under ambient temperature; inter-laboratory variation was approximately 30%. The Non-P-Tau CSF concentrations were highly significantly increased in patients with Alzheimer's disease in stage of mild cognitive impairment or dementia (AD/MCI, n=58, 109.2 ± 32.0 pg/mL) compared to the non-demented Controls (n=42, 62.1 ± 9.3 pg/mL, p<0.001). At the cut-off of 78.3 pg/mL, the sensitivity and the specificity were 94.8% and 97.6%, respectively. Conclusion: For the first time, an assay is reported to reliably measure concentrations of non-phosphorylated Tau in human CSF.
Marta Domínguez-Prieto, Ana Velasco, Lourdes Vega, Arantxa Tabernero, José M. Medina (Handling Associate Editor: Daniela Puzzo)
Aberrant Co-Localization of Synaptic Proteins Promoted by Alzheimer’s Disease Amyloid-β Peptides: Protective Effect of Human Serum Albumin
Abstract: Amyloid-β (Aβ), Aβ40, Aβ42, and, recently, Aβ25-35 have been directly implicated in the pathogenesis of Alzheimer’s disease. We have studied the effects of Aβ on neuronal death, reactive oxygen species (ROS) production, and synaptic assembling in neurons in primary culture. Aβ25-35, Aβ40, and Aβ42 significantly decreased neuronal viability, although Aβ25-35 showed a higher effect. Aβ25-35 showed a more penetrating ability to reach mitochondria while Aβ40 did not enter the neuronal cytosol and Aβ42 was scarcely internalized. We did not observe a direct correlation between ROS production and cell death because both Aβ40 and Aβ42 decreased neuronal viability but Aβ40 did not change ROS production. Rather, ROS production seems to correlate with the penetrating ability of each Aβ. No significant differences were found between Aβ40 and Aβ42 regarding the extent of the deleterious effects of both peptides on neuronal viability or synaptophysin expression. However, Aβ40 elicited a clear delocalization of PSD-95 and synaptotagmin from prospective synapsis to the neuronal soma, suggesting the occurrence of a crucial effect of Aβ40 on synaptic disassembling. The formation of Aβ40- or Aβ42-serum albumin complexes avoided the effects of these peptides on neuronal viability, synaptophysin expression, and PSD-95/synaptotagmin disarrangement suggesting that sequestration of Aβ by albumin prevents deleterious effects of these peptides. We can conclude that Aβ borne by albumin can be safely transported through body fluids, a fact that may be compulsory for Aβ disposal by peripheral tissues.
Chiara Cerami, Alessandra Dodich, Lucia Greco, Sandro Iannaccone, Giuseppe Magnani, Alessandra Marcone, Elisabetta Pelagallo, Roberto Santangelo, Stefano F. Cappa, Daniela Perani (Handling Associate Editor: Christine Bastin)
The Role of Single-Subject Brain Metabolic Patterns in the Early Differential Diagnosis of Primary Progressive Aphasias and in Prediction of Progression to Dementia
Abstract: Background and Objective: Primary progressive aphasia (PPA) is a clinical syndrome due to different neurodegenerative conditions in which an accurate early diagnosis needs to be supported by a reliable diagnostic tool at the individual level. In this study, we investigated in PPA the FDG-PET brain metabolic patterns at the single-subject level, in order to assess the case-to-case variability and its relationship with clinical-neuropsychological findings. Material and Methods: 55 patients (i.e., 11 semantic variant/sv-PPA, 19 non fluent variant/nfv-PPA, 17 logopenic variant/lv-PPA, 3 slowly progressive anarthria/SPA, and 5 mixed PPA/m-PPA) were included. Clinical-neuropsychological information and FDG-PET data were acquired at baseline. A follow-up of 27.4±12.55 months evaluated the clinical progression. Brain metabolism was analyzed using an optimized and validated voxel-based SPM method at the single-subject level. Results: FDG-PET voxel-wise metabolic assessment revealed specific metabolic signatures characterizing each PPA variant at the individual level, reflecting the underlying neurodegeneration in language networks. Notably, additional dysfunctional patterns predicted clinical progression to specific dementia conditions. In the case of nfv-PPA, a metabolic pattern characterized by involvement of parietal, subcortical and brainstem structures predicted progression to a corticobasal degeneration syndrome or to progressive supranuclear palsy. lv-PPA and sv-PPA cases who progressed to Alzheimer’s disease and frontotemporal dementia at the follow-up presented with extended bilateral patterns at baseline. Discussion: Our results indicate that FDG-PET voxel-wise imaging is a valid biomarker for the early differential diagnosis of PPAs and for the prediction of progression to specific dementia condition. This study supports the use of FDG-PET imaging quantitative assessment in clinical settings for a better characterization of PPA individuals and prognostic definition of possible endo-phenotypes.
Animesh Alexander Raha, James W. Henderson, Simon R.W. Stott, Romina Vuono, Simona Foscarin, Robert P. Friedland, Shahid H. Zaman, Ruma Raha-Chowdhury
Neuroprotective Effect of TREM-2 in Aging and Alzheimer’s Disease Model
Abstract: Neuroinflammation and activation of innate immunity are early events in neurodegenerative diseases including Alzheimer’s disease (AD). Recently, a rare mutation in the gene Triggering receptor expressed on myeloid cells 2 (TREM2) has been associated with a substantial increase in the risk of developing late onset AD. To uncover the molecular mechanisms underlying this association, we investigated the RNA and protein expression of TREM2 in APP/PS1 transgenic mice. Our findings suggest that TREM2 not only plays a critical role in inflammation, but is also involved in neuronal cell survival and in neurogenesis. We have shown that TREM2 is a soluble protein transported by macrophages through ventricle walls and choroid plexus, and then enters the brain parenchyma via radial glial cells. TREM2 protein is essential for neuroplasticity and myelination. During the late stages of life, a lack of TREM2 protein may accelerate aging processes and neuronal cell loss and reduce microglial activity, ultimately leading to neuroinflammation. As inflammation plays a major role in neurodegenerative diseases, a lack of TREM2 could be a missing link between immunomodulation and neuroprotection.
Julie M. Robillard, Tanya L. Feng (Handling Associate Editor: Allyson Rosen)
Health Advice in a Digital World: Quality and Content of Online Information about the Prevention of Alzheimer’s Disease
Abstract: Background: As the number of older adults turning to the Internet for health information increases, so does the potential for online information to have a substantial impact on the patient-physician relationship and on their health. Inaccurate information may weaken patient-physician relationships or result in increased physician visits and health-anxiety, while high quality information may allow Internet users to make better decisions about their health. Objective: To assess the quality and content of available online resources about the prevention of Alzheimer’s disease (AD). Methods: A sample of 308 articles related to the prevention of AD was collected from the first three pages of location-independent keyword searches on Google.com between September 17–30, 2014. Content analysis was applied to articles that met criteria (n=298) and a quality evaluation tool was developed to generate a quality score for each of the articles (n=290). Results: We found that articles on the high end of the quality spectrum focused on modifiable risk factors and tended to present balanced information, while articles of low quality emphasized nutrition as a method of prevention and were more likely to be in conflict of interest. Conclusion: This study provides the first insight into the content and quality of prevention information for AD currently available online and highlights the importance of future research to better understand the impact of this information on the patient-physician relationship and health decision-making of older adults.
Yamila Rodríguez Cruz, Manon Strehaiano, Teresita Rodríguez Obaya, Julío César García Rodríguez, Tangui Maurice
An Intranasal Formulation of Erythropoietin (Neuro-EPO) Prevents Memory Deficits and Amyloid Toxicity in the APPSwe Transgenic Mouse Model of Alzheimer's Disease
Abstract: Erythropoietin (EPO) is a cytokine known to have effective cytoprotective action in the brain, particularly in ischemic, traumatic, inflammatory, and neurodegenerative conditions. We previously reported the neuroprotective effect of a low sialic form of EPO, Neuro-EPO, applied intranasally in rodent models of stroke or cerebellar ataxia and in a non-transgenic mouse model of Alzheimer's disease (AD). Here we analyzed the protective effect of Neuro-EPO in APPSwe mice, a reference transgenic mouse model of AD. Mice were administered 3 times a day, 3 days in the week with Neuro-EPO (125, 250 µg/kg) intranasally, between 12 and 14 months of age. Motor responses, general activity, and memory responses were analyzed during and after treatment. The deficits in spontaneous alternation, place learning in the water-maze, and novel object recognition observed in APPSwe mice were alleviated by the low dose of Neuro-EPO. Oxidative stress, neuroinflammation, trophic factor levels, and a synaptic marker were analyzed in the hippocampus or cortex of the animals. The increases in lipid peroxidation or in GFAP and Iba-1 contents in APPSwe mice were significantly reduced after Neuro-EPO. Activation of intrinsic and extrinsic apoptotic pathways was analyzed. The increases in Bax/Bcl-2 ratio, TNFα, or Fas ligand levels observed in APPSwe mice were reduced by Neuro-EPO. Finally, immunohistochemical and ELISA analyses of Aβ1-42 levels in the APPSwe mouse cortex and hippocampus showed a marked reduction in Aβ deposits and in soluble and insoluble Aβ1-42 forms. This study therefore confirmed the neuroprotective activity of EPO, particularly for an intranasally deliverable formulation, devoid of erythropoietic side effects, in a transgenic mouse model of AD. Neuro-EPO alleviated memory alterations, oxidative stress, neuroinflammation, apoptosis induction, and amyloid load in 14-month-old APPSwe mice.
Jamie C. Fong, Julio C. Rojas, Jee Bang, Andrea Legati, Katherine P. Rankin, Sven Forner, Zachary A. Miller, Anna M. Karydas, Giovanni Coppola, Carrie K. Grouse, Jeffrey Ralph, Bruce L. Miller, Michael D. Geschwind
Genetic Prion Disease Caused by PRNP Q160X Mutation Presenting with an Orbitofrontal Syndrome, Cyclic Diarrhea, and Peripheral Neuropathy
Abstract: Patients with pathogenic truncating mutations in the prion gene (PRNP) usually present with prolonged disease courses with severe neurofibrillary tangle and cerebral amyloidosis pathology, but more atypical phenotypes also occur, including those with dysautonomia and peripheral neuropathy. We describe the neurological, cognitive, neuroimaging, and electrophysiological features of a 31-year-old man presenting with an orbitofrontal syndrome, gastrointestinal symptoms, and peripheral neuropathy associated with PRNP Q160X nonsense mutation, with symptom onset at age 27. The mutation was also detected in his asymptomatic father and a symptomatic paternal cousin; several members of prior generations died from early onset dementia. This is the first report of a family affected with the nonsense PRNP mutation Q160X displaying clear autosomal dominant disease in multiple family members and reduced penetrance. This case strengthens the evidence suggesting an association between PRNP truncating mutations and prion systemic amyloidosis. PRNP gene testing should be considered in any patient with atypical dementia, especially with early onset and neuropathy, even in the absence of a family history.
Louis Jacob, Ji Won Han, Tae Hui Kim, Joon Hyuk Park, Seok Bum Lee, Jung Jae Lee, Seung-Ho Ryu, Shin-Kyeom Kim, Jong Chul Yoon, Jin Hyeong Jhoo, Jeong Lan Kim, Kyung Phil Kwak, Seok Woo Moon, Bong Jo Kim, Dong Young Lee, Ki Woong Kim (Handling Associate Editor: Andrea Tales)
How Different are Quality of Life Ratings for People with Dementia Reported by Their Family Caregivers from Those Reported by the Patients Themselves?
Abstract: Background: Measurements of patient quality of life (QoL) play a major role in the management of dementia. Objective: We investigated the self-proxy discrepancy of QoL ratings in the elderly and the impact of dementia severity on the discrepancy. Methods: QoL of 718 patients with dementia and 651 non-demented elderly were rated by themselves and their caregivers (CG) using the Quality of Life-AD (QoL-AD). The impact of the rater on the total and item scores of QoL-AD was analyzed using repeated measures ANOVA and differential response patterns between self and proxy were analyzed using differential item functioning (DIF) analysis. Results: Self-rated scores were higher than CG-rated scores in all diagnostic groups. The interaction between rater and diagnostic group was significant in total QoL-AD score and 5 item scores (‘memory’, ‘marriage’, ‘chores around the house’, ‘do things for fun’, and ‘life as a whole’). The strength of the DIF increased with advancing dementia in these items. Conclusion: Self-proxy rating discrepancy of QoL was influenced by the presence and severity of dementia only in five items.
Babak A. Ardekani, Elaine Bermudez, Asim M. Mubeen, Alvin H. Bachman, for the Alzheimer’s Disease Neuroimaging Initiative (Handling Associate Editor: Ralph Buchert)
Prediction of Incipient Alzheimer’s Disease Dementia in Patients with Mild Cognitive Impairment
Abstract: Background: Mild cognitive impairment (MCI) is a transitional stage from normal aging to Alzheimer’s disease (AD) dementia. It is extremely important to develop criteria that can be used to separate the MCI subjects at imminent risk of conversion to Alzheimer-type dementia from those who would remain stable. We have developed an automatic algorithm for computing a novel measure of hippocampal volumetric integrity (HVI) from structural MRI scans that may be useful for this purpose. Objective: To determine the utility of HVI in classification between stable and progressive MCI patients using the Random Forest classification algorithm. Methods: We used a 16-dimensional feature space including bilateral HVI obtained from baseline and one-year follow-up structural MRI, cognitive tests, and genetic and demographic information to train a Random Forest classifier in a sample of 164 MCI subjects categorized into two groups [progressive (n=86) or stable (n=78)] based on future conversion (or lack thereof) of their diagnosis to probable AD. Results: The overall accuracy of classification was estimated to be 82.3% (86.0% sensitivity, 78.2% specificity). The accuracy in women (89.1%) was considerably higher than that in men (78.9%). The prediction accuracy achieved in women is the highest reported in any previous application of machine learning to AD diagnosis in MCI. Conclusion: The method presented in this paper can be used to separate stable MCI patients from those who are at early stages of AD dementia with high accuracy. There may be stronger indicators of imminent AD dementia in women with MCI as compared to men.
Woojae Myung*, Chunsoo Lee*, Jin Hong Park, Sook-young Woo, Seonwoo Kim, Sangha Kim, Jae Won Chung, Hyo Shin Kang, Shinn-Won Lim, Junbae Choi, Duk L. Na, Seong Yoon Kim, Jae-Hong Lee, Seol-Heui Han, Seong Hye Choi, Sang Yun Kim, Bernard J Carroll, Doh Kwan Kim *These authors contributed equally to this work.
Occupational Attainment as Risk Factor for Progression from Mild Cognitive Impairment to Alzheimer’s Disease: A CREDOS Study
Abstract: High occupational attainment has been known as a marker of cognitive reserve. Previous studies in the general population have shown that high occupational attainment is associated with reduced risk of Alzheimer’s disease (AD). However, few studies have assessed the effect of occupational attainment on the clinical course of mild cognitive impairment (MCI). In this study, we evaluated whether individuals with high occupational attainment show more rapid progression from MCI to AD. Participants (n = 961) with MCI were recruited from a nationwide, hospital-based multi-center cohort, and were followed for up to 60 months (median: 17.64, interquartile range [12.36, 29.28]). We used Cox regression for competing risks to analyze the effect of occupational attainment on development of AD, treating dementia other than AD as a competing risk. Among the 961 individuals with MCI, a total of 280 (29.1%) converted to dementia during the follow-up period. The risk of progression to AD was higher in the individuals with high occupational attainment after controlling for potential confounders (hazard ratio = 1.83, 95% confidence interval = 1.25–2.69, p = 0.002). High occupational attainment in individuals with MCI is an independent risk factor for early progression of MCI to AD. This result suggests that the protective effect of high occupational attainment against cognitive decline disappears in the MCI stage, and that careful assessment of occupational history can yield important clinical information for prognosis in individuals with MCI.
Sung-Mi Shim*, Hyo-Soon Cheon*, Chulman Jo, Young Ho Koh, Jihyun Song, Jae-Pil Jeon *These authors contributed equally to this work.
Elevated Epstein-Barr Virus Antibody Level is Associated with Cognitive Decline in the Korean Elderly
Abstract: Chronic viral infection is implicated in cognitive decline and Alzheimer’s disease (AD). Our goal was to identify biomarkers for the development of amnestic mild cognitive impairment (aMCI) from cognitively normal state. To accomplish this, we analyzed plasma IgG levels against Epstein-Barr virus (EBV) and herpes simplex virus (HSV-1) in study subjects with incident aMCI (Converter) and normal cognitive function (NC Control) who did or did not convert from cognitively normal state to aMCI during the 2-year follow-up period, respectively. The Converter group exhibited elevated levels of anti-EBV IgG antibodies in the post-follow-up phase (aMCI state) compared to the pre-follow-up phase (cognitively normal state), but not the NC Control group. In contrast, the total IgG level was not significantly changed over the follow-up period. Moreover, elevated anti-EBV IgG levels were significantly associated with CDR scales and total CERAD scores in the Converter group. These results suggest that EBV infection or its related host immune response is linked to cognitive decline. Thus, an EBV antibody level may be used as a potential biomarker for assessing the risk of aMCI development, implying a role for chronic EBV infection in AD pathogenesis.
Claire L. Russell, Vikram Mitra, Karl Hansson, Kaj Blennow, Johan Gobom, Henrik Zetterberg, Mikko Hiltunen, Malcolm Ward, Ian Pike (Handling Associate Editor: Khalid Iqbal)
Comprehensive Quantitative Profiling of Tau and Phosphorylated Tau Peptides in Cerebrospinal Fluid by Mass Spectrometry Provides New Biomarker Candidates
Abstract: Aberrant tau phosphorylation is a hallmark in Alzheimer’s disease (AD), believed to promote formation of paired helical filaments, the main constituent of neurofibrillary tangles in the brain. While cerebrospinal fluid (CSF) levels of total tau and tau phosphorylated at threonine residue 181 (pThr181) are established core biomarkers for AD, the value of alternative phosphorylation sites, which may have more direct relevance to pathology, for early diagnosis is not yet known, largely due to their low levels in CSF and lack of standardized detection methods. To overcome sensitivity limitations for analysis of phosphorylated tau in CSF, we have applied an innovative mass spectrometry (MS) workflow, TMTcalibrator™, to enrich and enhance the detection of phosphoproteome components of AD brain tissue in CSF, and enable the quantitation of these analytes. We aimed to identify which tau species present in the AD brain are also detectable in CSF and which, if any, are differentially regulated with disease. Over 75% coverage of full-length (2N4R) tau was detected in the CSF with 47 phosphopeptides covering 31 different phosphorylation sites. Of these, 11 phosphopeptides were upregulated by at least 40%, along with an overall increase in tau levels in the CSF of AD patients relative to controls. Use of the TMTcalibrator™ workflow dramatically improved our ability to detect tau-derived peptides that are directly related to human AD pathology. Further validation of regulated tau peptides as early biomarkers of AD is warranted and is currently being undertaken.
Francesca Zimetti, Paolo Caffarra, Nicoletta Ronda, Elda Favari, Maria Pia Adorni, Ilaria Zanotti, Franco Bernini, Federica Barocco, Marco Spallazzi, Daniela Galimberti, Chiara Ricci, Massimiliano Ruscica, Alberto Corsini, Nicola Ferri
Increased PCSK9 Cerebrospinal Fluid Concentrations in Alzheimer’s DiseaseAbstract: Background: Alzheimer’s disease (AD) has been associated with dysregulation of brain cholesterol trafficking and abnormal production of apolipoprotein E isoform 4 (apoE4). Proprotein convertase subtilisin/kexin type 9 (PCSK9) is a protein present in serum and cerebrospinal fluid (CSF) degrading the low-density lipoprotein receptor (LDLr) and other apoE-binding receptors involved in neuron cholesterol uptake. The role of PCSK9 in AD is controversial. Objective: We compared PCSK9 levels in CSF of AD patients and non-AD controls and looked at correlations with CSF total apoE and apoE4. Methods: CSF from AD (n=30) and from age and sex-matched non-AD patients (n=30) was collected by lumbar puncture for routine diagnosis. CSF PCSK9, total apoE, and apoE4 levels were measured by ELISA. AD patients showed the typical CSF neurobiomarker pattern (decreased Aβ42 and increased tau and phospho-tau) and impaired cognitive performances, as indicated by the scores of the Mini-Mental State Examination test. Results: PCSK9 levels in CSF were higher in AD than in non-AD subjects (+1.45 fold; p=0.0049). CSF total apoE concentrations did not differ between the two groups, while apoE4 levels were higher in AD subjects (+3.34 fold; p=0.0068). Considering all samples, a significant positive correlation was found between PCSK9 and apoE4 (r=0.4409; p=0.0006). PCSK9 levels were higher in APOE ε4 carriers, reaching statistical significance in the AD group (+1.45 fold; p=0.0454). Conclusion: These results report for the first time an alteration of CSF PCSK9 levels in AD and suggest a pathophysiological link between PCSK9, apoE4, and AD.
Damien Leger, Maxime Elbaz, Alexandre Dubois, Stéphane Rio, Hocine Mezghiche, Paulo Carita, Jeanne Stemmelin, Melanie Strauss
Alzheimer’s Disease Severity is Not Significantly Associated with Short Sleep: Survey by Actigraphy on 208 Mild and Moderate Alzheimer’s Disease Patients
Abstract: Background: In epidemiological surveys, cognitive decline has been found to be associated with both short and long sleep duration. Objective: Our goal was to objectively determine how total sleep time (TST) at night was associated or not with apathy or severity scores in patients with Alzheimer ’s disease (AD). Methods: During an observational first step of a clinical trial, sleep was assessed in institutionalized patients with mild or moderate AD using actigraphy (MW8, Camtech, Cambridge, UK) for 14 consecutive 24-hour periods. Sleep parameters analyzed were: TST, time in bed (TIB), wake after sleep onset (WASO), sleep efficiency (SE) defined by the ratio TST/TIB, in percentage), the number and length of awakenings, the night fragmentation index, the interdaily stability, and intradaily variability indexes. Statistical association analyses were tested between these values and AD apathy and severity scores. Results: 208 individuals coming from 82 centers worldwide (France, Germany, Spain, Italy, Portugal, Poland, United States, Canada, and Australia) and ≥ 50 years old participated. Their average TST was 7 hours and 35 minutes and the average WASO 58 minutes. TST and SE were significantly higher in patients with apathy and the number of awakenings was significantly lower. TST was also positively associated with functional disability (ADCS-ADL scores), but it was not found significantly greater in patients with a moderate AD severity compared to the mild. Conclusion: Despite several and long awakenings, TST was not found too short in patients with AD. TST was even significantly increased with disability and apathy.
Whitney M. Freeze, Heidi I. L. Jacobs, Ed H. Gronenschild, Jacobus F. A. Jansen, Saartje Burgmans, Pauline Aalten, Lies Clerx, Stephanie J. Vos, Mark A. van Buchem, Frederik Barkhof, Wiesje M. van der Flier, Marcel M. Verbeek, Marcel Olde Rikkert, Walter H. Backes, Frans R. Verhey, on behalf of the LeARN project (Handling Associate Editor: Joel Ramirez)
White Matter Hyperintensities Potentiate Hippocampal Volume Reduction in Non-Demented Older Individuals with Abnormal Amyloid-β
Abstract: Cerebral small vessel disease (cSVD) and amyloid-β (Aβ) deposition often co-exist in (prodromal) dementia, and both types of pathology have been associated with neurodegeneration. We examined whether cSVD and Aβ have independent or interactive effects on hippocampal volume (HV) in a memory clinic population. We included 87 individuals with clinical diagnoses of Alzheimer’s disease (AD) (n=24), mild cognitive impairment (MCI) (n=26), and subjective cognitive complaints (SCC) (n=37). cSVD magnetic resonance imaging markers included white matter hyperintensity (WMH) volume, lacunar infarct presence, and microbleed presence. Aβ pathology was assessed as cerebrospinal fluid-derived Aβ1-42 levels and dichotomized into normal or abnormal, and HV was determined by manual volumetric measurements. A linear hierarchical regression approach was applied for the detection of additive or interaction effects between cSVD and Aβ on HV in the total participant group (n=87) and in the non-demented group (including SCC and MCI individuals only, n=63). The results revealed that abnormal Aβ and lacunar infarct presence were independently associated with lower HV in the non-demented individuals. Interestingly, Aβ and WMH pathology interacted in the non-demented individuals, such that WMH had a negative effect on HV in individuals with abnormal CSF Aβ42 levels, but not in individuals with normal CSF Aβ42 levels. These associations were not present when individuals with AD were included in the analyses. Our observations suggest that relatively early on in the disease process older individuals with abnormal Aβ levels are at an increased risk of accelerated disease progression when concomitant cSVD is present.
Miguel Ángel Araque Caballero, Stefan Klöppel, Martin Dichgans, Michael Ewers for the Alzheimer’s Disease Neuroimaging Initiative (Handling Associate Editor: Natalie Marchant)
Spatial Patterns of Longitudinal Gray Matter Change as Predictors of Concurrent Cognitive Decline in Amyloid Positive Healthy Subjects
Abstract: A substantial proportion of cognitively healthy elders (HC) show abnormally high amyloid-β (Aβ) deposition, a major pathology of Alzheimer’s disease (AD). These subjects are at increased risk of Alzheimer’s disease (AD) dementia, and biomarkers are needed to predict their cognitive deterioration. Here we used relevance vector regression (RVR), a pattern-recognition method, to predict concurrent cognitive decline on the basis of longitudinal gray matter (GM) changes, within two a priori, meta-analytically defined functional networks subserving episodic memory and executive function. Ninety-six HC subjects were assessed annually for three years with structural MRI and cognitive tests within the Alzheimer’s Disease Neuroimaging Initiative. Presence of abnormal biomarker values of Aβ (Aβ+) were determined with cerebrospinal fluid and amyloid-PET (HC-Aβ+, n = 30; with n = 66 for normal HC-Aβ-). Using leave-one-out cross-validation, we found that in HC-Aβ+ patterns of GM changes within both networks predicted decline in episodic memory (r = 0.61, p < 0.001; r = 0.40, p = 0.03), but not executive function. In HC-Aβ-, GM changes within the executive function network predicted decline in executive function (r = 0.44, p < 0.001). Previously established region-of-interest (ROI)-based predictors such as changes in hippocampal volume, within an AD-signature multi-ROI, or total GM volume were not predictive of cognitive decline in any group or cognitive domain. RVR analyses unrestricted to the a priori networks yielded compatible results with the restricted case. In conclusion, RVR-derived patterns of subtle cortical GM changes are biomarker candidates of concurrent cognitive decline in aging and subjects at risk for AD.
Kaffer Kara, Amir Abbas Mahabadi, Christian Weimar, Angela Winkler, Till Neumann, Hagen Kälsch, Nico Dragano, Susanne Moebus, Raimund Erbel, Karl-Heinz Jöckel*, Martha Jokisch* *These authors contributed equally to this work.
N-Terminal Pro-B Type Natriuretic Peptide is Associated with Mild Cognitive Impairment in the General Population
Abstract: Background: N-terminal pro-B type natriuretic peptide (NT-proBNP) is a marker of cardiac stress and is linked with silent cardiac diseases. While associations of cognitive impairment with manifest cardiovascular diseases are established, data on whether subclinical elevation of NT-proBNP levels below clinically established threshold of heart failure is related with cognitive functioning, especially mild cognitive impairment (MCI), is rare. Objective: Aim of the present study was to investigate the cross-sectional association of NT-proBNP levels and MCI in a population-based study sample without heart failure. Methods: We used data from the second examination of the population based Heinz-Nixdorf-Recall-Study. Subjects with overt coronary heart disease and subjects with NT-proBNP levels indicating potential heart failure (NT-proBNP ≥ 300 pg/ml) were excluded from this analysis. Participants performed a validated brief cognitive assessment and were classified either as MCI [subtypes: amnestic-MCI (aMCI), non-amnestic-MCI (naMCI)], or cognitively-normal. Results: We included 419 participants with MCI (63.1±7.4 y; 47% men; aMCI n=209; naMCI n=210) and 1,206 cognitively normal participants (62.42±7.1 y; 48% men). NT-proBNP-levels ≥125 pg/ml compared to
Ane-Victoria Idland, Torgeir Bruun Wyller, Randi Støen, Lars Magne Eri, Frede Frihagen, Johan Ræder, Farrukh Abbas Chaudhry, Oskar Hansson, Henrik Zetterberg, Kaj Blennow, Nenad Bogdanovic, Anne Brækhus, Leiv Otto Watne (Handling Associate Editor: Inga Zerr)
Preclinical Amyloid-β and Axonal Degeneration Pathology in Delirium
Abstract: Background: The clinical relevance of brain β-amyloidosis in older adults without dementia is not established. As delirium and dementia are strongly related, studies on patients with delirium may give pathophysiological clues. Objective: To determine whether the Alzheimer’s disease (AD) cerebrospinal fluid (CSF) biomarkers amyloid-β 1-42 (Aβ42), total tau (T-tau), and phosphorylated tau (P-tau) are associated with delirium in hip fracture patients with and without dementia. Methods: CSF was collected in conjunction to spinal anesthesia in 129 patients. Delirium was assessed using the Confusion Assessment Method once daily in all patients, both pre- and postoperatively. The diagnosis of dementia at admission was based upon clinical consensus. CSF levels of Aβ42, T-tau, and P-tau were analyzed. Results: In patients without dementia, we found lower CSF Aβ42 levels (median, 310 ng/L versus 489 ng/L, p=0.006), higher T-tau levels (median, 505 ng/L versus 351 ng/L, p=0.02), but no change in P-tau in patients who developed delirium (n=16) compared to those who remained lucid (n=49). Delirious patients also had lower ratios of Aβ42 to T-tau (p<0.001) and P-tau (p=0.001) relative to those without delirium. CSF Aβ42 and T-tau remained significantly associated with delirium status in adjusted analyses. In patients with dementia, CSF biomarker levels did not differ between those with (n=54) and without delirium (n=10). Conclusion: The reduction in CSF Aβ42, indicating β-amyloidosis, and increase in T-tau, indicating neurodegeneration, in hip fracture patients without dementia developing delirium indicates that preclinical AD brain pathology is clinically relevant and possibly plays a role in delirium pathophysiology.
Julia Kim, Tom A. Schweizer, Corinne E. Fischer, David G. Munoz
The Role of Cerebrovascular Disease on Cognitive and Functional Status and Psychosis in Severe Alzheimer’s Disease
Abstract: Background: The pathophysiology behind psychosis in patients with Alzheimer’s disease (AD) remains unknown. Vascular risk factors have been recognized as an important modifier of the clinical presentation of AD. Objective: The purpose of our study is to investigate the mechanism through which vascular risk factors mediate psychosis and whether or not it involves cerebrovascular lesions. Methods: Data was provided by the National Alzheimer’s Coordinating Centre. The Uniform Data Set was used to collect information on subject-reported history of vascular risk factors, clinician-reported state of cognitive performance, and presence of psychosis based on the Neuropsychiatric Inventory Questionnaire (NPI-Q). The Neuropathology Data Set was used to evaluate the presence of vascular lesions and the severity of AD pathology. Subjects with high probability of AD based on the NIA/AA Reagan criteria were included in the analysis. Results: We identified 1,459 patients with high probability of AD and corresponding NPI-Q scores. We confirmed the association between hypertension and diabetes on psychosis, specifically in delusions and the co-occurrence of delusions and hallucinations. Furthermore, the presence of white matter rarefaction based on pathological evaluation was associated with hallucinations. A history of vascular risk factors was positively associated with vascular lesions. However, vascular lesions in the presence of vascular risk factors did not increase the likelihood of psychosis. Furthermore, vascular lesions were not associated with greater cognitive or functional impairments in this group with severe AD pathology. Conclusion: Vascular risk factors and vascular lesions are independently associated with psychosis in patients with severe AD. However, vascular lesions are not the mechanism through which vascular risk factors mediate psychosis.
Carolyn L. Fisher, Ross J. Resnick, Soumya De, Lucila A. Acevedo, Kun Ping Lu, Frank C. Schroeder, Linda K. Nicholson
Cyclic cis-Locked Phospho-Dipeptides Reduce Entry of AβPP into Amyloidogenic Processing Pathway
Abstract: The cis/trans isomerization of X-Pro peptide bonds in proteins in some instances acts as a molecular switch in biological pathways. Our prior work suggests that the cis isomer of the phospho-Thr668-Pro669 motif, located in the cytoplasmic domain of the amyloid-β protein precursor (AβPP), is correlated with an increase in amyloidogenic processing of AβPP and production of amyloid-beta (Aβ), the neurotoxic peptide fragment in Alzheimer’s disease (AD). We designed a 100% cis-locked cyclic dipeptide composed of cyclized phospho-Thr-Pro (pCDP) as a mimic for this putative pathological conformation, and three phosphate-blocked derivatives (pCDP-diBzl, pCDP-Bzl, and pCDP-diPOM). Two H4 neuroglioma cell lines were established as AD cell models for use in testing these compounds: H4-AβPP695 for stable overexpression of wild-type AβPP695, and H4-BACE1 for stable overexpression of β-site AβPP cleaving enzyme-1 (BACE1). The level of the secreted AβPP fragment resulting from BACE1 activity, sAβPPβ, served as a key proxy for amyloidogenic processing, since cleavage of AβPP by BACE1 is a requisite first step in Aβ production. Of the compounds tested, pCDP-diBzl decreased sAβPPβ levels in both cell lines, while pCDP-diPOM decreased sAβPPβ levels in only H4-BACE1 cells, all with similar dose-dependences and patterns of proteolytic AβPP fragments. Enzymatic assays showed that none of the pCDP derivatives directly inhibit BACE1 catalytic activity. These results suggest a model in which pCDP-diBzl and pCDP-diPOM act at a common point to inhibit entry of AβPP into the amyloidogenic AβPP processing pathway but through different targets, and provide important insights for the development of novel AD therapeutics.
William A. Banks, Andrej Kovac, Petra Majerova, Kristin M. Bullock, Min Shi, Jing Zhang (Handling Associate Editor: Maria Deli)
Tau Proteins Cross the Blood-Brain Barrier
Abstract: Tauopathies are a hallmark of many neurodegenerative diseases, including Alzheimer’s disease and traumatic brain injuries. It has been demonstrated that amyloid-beta peptides, alpha-synuclein, and prion proteins cross the blood-brain barrier (BBB), contributing to their abilities to induce disease. Very little is known about whether tau proteins can cross the BBB. Here we systematically characterized several key forms of tau proteins to cross the BBB, including Tau-441 (2N4R), Tau-410 (2N3R), truncated tau 151-391 (0N4R), and truncated tau 121-227. All of these tau proteins crossed the BBB readily and bidirectonally; however, only Tau-410 had a saturable component to its influx. The tau proteins also entered the blood after their injection into the brain, with Tau 121-227 having the slowest exit from brain. The tau proteins varied in regards to their enzymatic stability in brain and blood and in their peripheral pharmacokinetics. These results show that blood-borne tau proteins could contribute to brain tauopathies. The result also suggest that the CNS can contribute to blood levels of tau, raising the possibility that, as suggested for other misfolded proteins, blood levels of tau proteins could be used as a biomarker of CNS disease.
Laura Serra, Matteo Mancini,, Mara Cercignani, Carlotta Di Domenico, Barbara Spanò, Giovanni Giulietti, Giacomo Koch, Camillo Marra, Marco Bozzali (Handling Associate Editor: Daniela Galimberti)
Network-Based Substrate of Cognitive Reserve in Alzheimer’s Disease
Abstract: Cognitive reserve (CR) is known to modulate the clinical features of Alzheimer’s disease (AD). This concept may be critical for the development of non-pharmacological interventions able to slow down patients’ cognitive decline in the absence of disease-modifying treatments. We aimed at identifying the neurobiological substrates of CR (i.e., neural reserve) over the transition between normal aging and AD, by assessing the underlying brain networks and their topological properties. A cohort of 154 participants (n=68 with AD, n=61 with amnestic mild cognitive impairment (aMCI), and 25 healthy subjects) underwent resting-state functional MRI and neuropsychological testing. Within each group, participants were classified as having high or low CR, and functional connectivity measures were compared, within group, between high and low CR individuals. Network-based statistics and topological network properties derived from graph theory were explored. Connectivity differences between high and low CR were evident only for aMCI patients, with participants with high CR showing a significant increase of connectivity in a network involving mainly fronto-parietal nodes. Conversely, they showed significantly decreased connectivity in a network involving fronto-temporo-cerebellar nodes. Consistently, changes to topological measures were observed in either direction, and were associated with measures of global cognitive function. These findings support the hypothesis that CR impacts on neurodegenerative process in the early phase of AD only. In addition, they fit with the existence of a “neural reserve”, characterized by specific neural networks and their efficiency. It remains to be demonstrated whether interventions later in life can modulate this “neural reserve”.
Oriol Grau-Rivera, Anna Calvo, Núria Bargalló, Gemma C. Monté, Carlos Nos, Albert Lladó, José Luis Molinuevo, Ellen Gelpi, Raquel Sánchez-Valle (Handling Associate Editor: Inga Zerr)
Quantitative Magnetic Resonance Abnormalities in Creutzfeldt-Jakob Disease and Fatal Insomnia
Abstract: Background: Quantitative neuroimaging might unveil abnormalities in prion diseases that are not perceivable at visual inspection. On the other hand, scarce studies have quantified volumetric changes in prion diseases. Objectives: We aim to characterize volumetric and diffusion tensor imaging (DTI) changes in patients with prion diseases who presented with either Creutzfeldt-Jakob disease (CJD) or fatal insomnia (FI) phenotype. Methods: Twenty patients with prion diseases—15 with CJD and 5 with fatal insomnia (FI)—and 40 healthy controls were examined with a 3-Tesla magnetic resonance imaging scanner. Images were segmented and normalized with SPM12. DTI maps were obtained with FMRIB Software Library. Whole-brain voxel-wise and region-of-interest analyses of volumetric and DTI changes were performed with SPM12. White matter (WM) changes were also analyzed with tract-based spatial statistics. Semiquantitive assessment of neuropathological parameters was compared with DTI metrics in thalamus from 11 patients. Results: Patients with CJD and FI presented significant atrophy in thalamus and cerebellum. In CJD, mean diffusivity (MD) was decreased in striatum and increased in subcortical WM, while both increased and decreased values were observed across different thalamic nuclei. In FI, MD was increased in thalamus and cerebellum. Spongiform change and PrPSc deposition were more intense in thalamus in CJD than in FI, although no significant correlations arose with MD values in the nuclei studied. Conclusion: Volumetric and DTI abnormalities suggest a central common role of the thalamus in prion diseases. We report, for the first time, quantitative MRI changes in FI, and provide further evidence of WM involvement in prion diseases.