Margaret F. Bassendine, Simon D. Taylor-Robinson, Michael Fertleman, Michael Khan, Dermot Neely
Is Alzheimer’s Disease a Liver Disease of the Brain?
Abstract: Clinical specialization is not only a force for progress, but it has also led to the fragmentation of medical knowledge. The focus of research in the field of Alzheimer’s disease (AD) is neurobiology, while hepatologists focus on liver diseases and lipid specialists on atherosclerosis. This article on AD focuses on the role of the liver and lipid homeostasis in the development of AD. Amyloid-β (Aβ) deposits accumulate as plaques in the brain of an AD patient long before cognitive decline is evident. Aβ generation is a normal physiological process; the steady-state level of Aβ in the brain is determined by balance between Aβ production and its clearance. We present evidence suggesting that the liver is the origin of brain Aβ deposits and that it is involved in peripheral clearance of circulating Aβ in the blood. Hence the liver could be targeted to decrease Aβ production or increase peripheral clearance.
George D. Wilson, Thomas G. Wilson, Alaa Hanna, Justin Kulchycki, Katie Buelow, Barbara L. Pruetz, Daniel B. Michael, Prakash Chinnaiyan, Michael E. Maddens, Alvaro A. Martinez, James Fontanesi
Low Dose Brain Irradiation Reduces Amyloid-β and Tau in 3xTg-AD Mice
Abstract: We have previously reported that low doses of external beam ionizing irradiation reduced amyloid-β (Aβ) plaques and improved cognition in APP/PS1 mice. In this study we investigated the effects of radiation in an age-matched series of 3xTg-AD mice. Mice were hemibrain-irradiated with 5 fractions of 2 Gy and sacrificed 8 weeks after the end of treatment. Aβ and tau were assessed using immunohistochemistry and quantified using image analysis with Definiens Tissue Studio. We observed a significant reduction in Aβ plaque burden and tau staining; these two parameters were significantly correlated. This preliminary data is further support that low doses of radiation may be beneficial in Alzheimer’s disease.
Felix Clay, David Howett, James FitzGerald, Paul Fletcher, Dennis Chan, Annabel Price (Handling Associate Editor: Kerryn Pike)
Use of Immersive Virtual Reality in the Assessment and Treatment of Alzheimer’s Disease: A Systematic Review
Abstract: Background: Immersive virtual reality (iVR) allows seamless interaction with simulated environments and is becoming an established tool in clinical research. It is unclear whether iVR is acceptable to people with Alzheimer’s disease (AD) dementia or useful in their care. We explore whether iVR is a viable research tool that may aid the detection and treatment of AD. Objectives: This review examines the use of iVR in people with AD or mild cognitive impairment (MCI). Methods: Medline, PsycINFO, Embase, CINAHL, and Web of Science databases were searched from inception. PRISMA guidelines were used with studies selected by at least two researchers. Results: Nine studies were eligible for inclusion. None reported any issues with iVR tolerability in participants with MCI and AD on assessment or treatment tasks. One study demonstrated capability for detecting prodromal AD and correlated with neuroanatomical substrates. Two studies showed iVR to have high accuracy in differentiating participants with AD from controls but were not hypothesis driven or with adequate controls measures. In a small validation study and two longitudinal case studies, iVR cognitive training was positively rated but did not demonstrate reliable benefit. Conclusion: iVR is emerging as a viable method of assessing older adults and people with AD. Strongest benefits were seen when closely integrated with theoretical models of neurodegeneration and existing screening methods. Further randomized controlled trials integrated with clinical populations are required. This will consolidate the power of iVR for assessment of MCI and clarify treatment efficacy beyond current applications in physical rehabilitation.
Yasunari Seita*, Toshifumi Morimura*, Naoki Watanabe, Chizuru Iwatani, Hideaki Tsuchiya, Shinichiro Nakamura, Toshiharu Suzuki, Daijiro Yanagisawa, Tomoyuki Tsukiyama, Masataka Nakaya, Eiichi Okamura, Masanaga Muto, Masatsugu Ema, Masaki Nishimura, Ikuo Tooyama (Handling Associate Editor: Shun Shimohama) *These authors contributed equally to this work.
Generation of Transgenic Cynomolgus Monkeys Overexpressing the Gene for Amyloid-β Precursor Protein
Abstract: Alzheimer’s disease (AD) is the most common cause of dementia and understanding its pathogenesis should lead to improved therapeutic and diagnostic methods. Although several groups have developed transgenic mouse models overexpressing the human amyloid-β precursor protein (APP) gene with AD mutations, with and without presenilin mutations, as well as APP gene knock-in mouse models, these animals display amyloid pathology but do not show neurofibrillary tangles or neuronal loss. This presumably is due to differences between the etiology of the aged-related human disease and the mouse models. Here we report the generation of two transgenic cynomolgus monkeys overexpressing the human gene for APP with Swedish, Artic, and Iberian mutations, and demonstrated expression of gene tagged green fluorescent protein marker in the placenta, amnion, hair follicles, and peripheral blood. We believe that these nonhuman primate models will be very useful to study the pathogenesis of dementia and AD. However, generated Tg monkeys still have some limitations. We employed the CAG promoter, which will promote gene expression in a non-tissue specific manner. Moreover, we used transgenic models but not knock-in models. Thus, the inserted transgene destroys endogenous gene(s) and may affect the phenotype(s). Nevertheless, it will be of great interest to determine whether these Tg monkeys will develop tauopathy and neurodegeneration similar to human AD.
Shweta Kishor Sonawane, Subashchandrabose Chinnathambi
P301L, an FTDP-17 Mutant, Exhibits Enhanced Glycation in vitro
Abstract: Background: Frontotemporal dementia and parkinsonism-linked to chromosome-17 are a group of diseases with tau mutations leading to primary tauopathies which include progressive supranuclear palsy, corticobasal syndrome, and frontotemporal lobar degeneration. Alzheimer’s disease is a non-primary tauopathy, which displays tau neuropathology of excess tangle formation and accumulation. FTDP-17 mutations are responsible for early onset of AD, which can be attributed to compromised physiological functions due to the mutations. Tau is a microtubule-binding protein that secures the integrity of polymerized microtubules in neuronal cells. It malfunctions owing to various insults and stress conditions-like mutations and post-translational modifications. Objective: In this study, we modified the wild type and tau mutants by methyl glyoxal and thus studied whether glycation can enhance the aggregation of predisposed mutant tau. Methods: Tau glycation was studied by fluorescence assays, SDS-PAGE analysis, conformational evaluation, and transmission electron microscopy. Results: Our study suggests that FTDP-17 mutant P301L leads to enhanced glycation-induced aggregation as well as advanced glycation end products formation. Glycation forms amorphous aggregates of tau and its mutants without altering its native conformation. Conclusion: The metabolic anomalies and genetic predisposition have found to accelerate tau-mediated neurodegeneration and prove detrimental for the early-onset of Alzheimer’s disease.
Catherine Dion, Franchesca Arias, Shawna Amini, Randall Davis, Dana Penney, David J. Libon, Catherine C. Price
Cognitive Correlates of Digital Clock Drawing Metrics in Older Adults with and without Mild Cognitive Impairment
Abstract: Background: A digital version of the clock drawing test (dCDT) provides new latency and graphomotor behavioral measurements. These variables have yet to be validated with external neuropsychological domains in non-demented adults. Objective: The current investigation reports on cognitive constructs associated with selected dCDT latency and graphomotor variables and compares performances between individuals with mild cognitive impairment (MCI) and non-MCI peers. Methods: 202 non-demented older adults (age 68.79 ± 6.18, 46% female, education years 16.02 ± 2.70) completed the dCDT and a comprehensive neuropsychological protocol. dCDT variables of interest included: total completion time (TCT), pre-first hand latency (PFHL), post-clock face latency (PCFL), and clock face area (CFA). We also explored variables of percent time drawing (i.e., ‘ink time’) versus percent time not drawing (i.e., ‘think time’). Neuropsychological domains of interest included processing speed, working memory, language, and declarative memory. Results: Adjusting for age and premorbid cognitive reserve metrics, command TCT positively correlated with multiple cognitive domains; PFHL and PCFL negatively associated with worse performance on working memory and processing speed tests. For Copy, TCT, PCFL, and PFHL negatively correlated with processing speed, and CFA negatively correlated with language. Between-group analyses show MCI participants generated slower command TCT, produced smaller CFA, and required more command ‘think’ (%Think) than ‘ink’ (%Ink) time. Conclusion: Command dCDT variables of interest were primarily processing speed and working memory dependent. MCI participants showed dCDT differences relative to non-MCI peers, suggesting the dCDT may assist with classification. Results document cognitive construct validation to digital metrics of clock drawing.
Xiangzhu Zhu, Amy R. Borenstein, Yinan Zheng, Wei Zhang, Douglas L. Seidner, Reid Ness, Harvey J. Murff, Bingshan Li, Martha J. Shrubsole, Chang Yu, Lifang Hou, Qi Dai
Ca:Mg Ratio, APOE Cytosine Modifications, and Cognitive Function: Results from a Randomized Trial
Abstract: Background: Deterioration of ionized calcium (Ca2+) handling in neurons could lead to neurodegenerative disease. Magnesium (Mg) antagonizes Ca during many physiologic activities, including energy metabolism and catalyzation of demethylation from 5-methylcytosine(5-mC) to 5-hydroxymethylcytosine(5-hmC). Objective: To test the hypothesis that actively reducing the Ca:Mg intake ratio in the diet through Mg supplementation improves cognitive function, and to test whether this effect is partially mediated by modified cytosines in Apolipoprotein E (APOE). Methods: This study is nested within the Personalized Prevention of Colorectal Cancer Trial (PPCCT), a double-blind 2x2 factorial randomized controlled trial, which enrolled 250 participants from Vanderbilt University Medical Center. Target doses for both Mg and placebo arms were personalized. Results: Among those aged >65 years old who consumed a high Ca:Mg ratio diet, we found that reducing the Ca:Mg ratio to around 2.3 by personalized Mg supplementation significantly improved cognitive function by 9.1% (p=0.03). We also found that reducing the Ca:Mg ratio significantly reduced 5-mC at the cg13496662 and cg06750524 sites only among those aged >65 years old (p values=0.02 and 0.03, respectively). Furthermore, the beneficial effect of reducing the Ca:Mg ratio on cognitive function in those aged over 65 years was partially mediated by reductions in 5-mC levels (i.e., cg13496662 and cg06750524) in APOE (p for indirect effect=0.05). Conclusion: Our findings suggest that, among those age 65 and over with a high dietary Ca:Mg ratio, optimal Mg status may improve cognitive function partially through modifications in APOE methylation. These findings, if confirmed, have significant implications for the prevention of cognitive aging and Alzheimer’s disease.
Andreas Traschütz*, S. Jonas Enkirch*, Nenad Polomac, Catherine N. Widmann, Hans H. Schild, Michael T. Heneka, Elke Hattingen (Handling Associate Editor: Robert Perneczky) *These authors contributed equally to this work.
The Entorhinal Cortex Atrophy Score Is Diagnostic and Prognostic in Mild Cognitive Impairment
Abstract: Background: Structural magnetic resonance imaging (MRI) is routinely performed in patients with mild cognitive impairment (MCI), but diagnostic accuracy to detect early cerebral atrophy is limited. Objective: To validate the visual entorhinal cortex atrophy (ERICA) rating scale regarding diagnosis, biomarker status, neuropsychological profile, and dementia risk in MCI. Methods: The ERICA score was retrospectively assessed regarding its discrimination of MCI (n = 80) from subjective cognitive decline and Alzheimer’s disease (AD) dementia (n = 60, respectively), its prediction of conversion to dementia (median follow-up 28 months) and amyloid/tau biomarker status, and its association with neuropsychological tests. Results: The ERICA score achieved 97% positive predictive value (PPV) for the presence of MCI. Discrimination between MCI and AD dementia (area under the curve: 0.71) was comparable to volumetry, and superior to the medial temporal lobe atrophy (MTA) score (p = 0.006). The PPV of the ERICA score for conversion to dementia was 83%, equivalent to tau status. It achieved 90% PPV for conversion when combined with tau, and 100% negative predictive value with verbal recall. While no measure predicted the predominantly positive amyloid status, the ERICA score was at least comparable to volumetry, and superior to the MTA score in predicting tau positivity (92% PPV for phospho-tau). The ERICA score was associated with verbal learning and memory, and, unlike the MTA score, also with AD-specific deficits in cued verbal recall. Conclusion: The ERICA score is a simple and valuable tool to exploit structural MRI for diagnosis and prognosis in MCI and is non-inferior to volumetry.
Veena V. Kumar, Hanfeng Huang, Liping Zhao, Danielle D. Verble, Alexandra Nutaitis, Sonum D. Tharwani, Alexandra L. Brown, Henrik Zetterberg, William Hu, Ryan Shin, Patrick G. Kehoe, Arshed Quyyumi, Joe Nocera, Andrea Kippels, Whitney Wharton
Baseline Results: The Association between Cardiovascular Risk and Preclinical Alzheimer’s Disease Pathology (ASCEND) Study
Abstract: Background: The rate of AD for African Americans (AAs) is 64% higher than for non-Hispanic White Americans (Whites). It is hypothesized that poor peripheral vascular function, in combination with genetics, stress, and inflammation may directly contribute to the accumulation of AD pathologic biomarkers. These risk factors may disproportionately affect AAs. Objective: Our objective was to determine if in a healthy middle-aged cohort at risk for AD (1) AD biomarkers in CSF differ by race, (2) peripheral vascular dysfunction and cognition are related to a higher burden of CSF AD biomarkers, and (3) these relationships differ by race. Methods: We enrolled 82 cognitively normal, middle-aged (45 and older) adults including AAs and Whites at high risk for AD due to parental history. Study procedures included lumbar puncture, vascular ultrasound, and cognitive testing. Results: While participants were in overall good health, AAs exhibited poorer indices of preclinical vascular health, including higher central SBP, central MAP, and EndoPAT AI, a marker of arterial stiffness. AAs also had significantly less cerebrospinal fluid tau burden than Whites. After polynomial regression analysis, adjusted for age, gender, education, and ApoE4 status, race significantly modified the relationship between total tau, phospho-tau, and Trails B, a marker of executive function. Small differences in tau correlated with poorer cognition in AAs. Conclusion: In a healthy middle-aged cohort at risk for AD, AAs had worse peripheral vascular health and worse cognition than Whites. Despite lower tau burden overall, race modified the relationship between tau and cognition, such that small differences in tau between AAs was related to worse cognition when compared to Whites.
Dominic D. Quintana, Jorge A. Garcia, Yamini Anantula, Stephanie L. Rellick, Elizabeth B. Engler-Chiurazzi, Saumyendra N. Sarkar, Candice M. Brown, James W. Simpkins (Handling Associate Editor: Branko Huisa)
Amyloid-β Causes Mitochondrial Dysfunction via a Ca2+-Driven Upregulation of Oxidative Phosphorylation and Superoxide Production in Cerebrovascular Endothelial Cells
Abstract: Cerebrovascular pathology is pervasive in Alzheimer’s disease (AD), yet it is unknown whether cerebrovascular dysfunction contributes to the progression or etiology of AD. In human subjects and in animal models of AD, cerebral hypoperfusion and hypometabolism are reported to manifest during the early stages of the disease and persist for its duration. Amyloid-β is known to cause cellular injury in both neurons and endothelial cells by inducing the production of reactive oxygen species and disrupting intracellular Ca2+ homeostasis. We present a mechanism for mitochondrial degeneration caused by the production of mitochondrial superoxide, which is driven by increased mitochondrial Ca2+ uptake. We found that persistent superoxide production injures mitochondria and disrupts electron transport in cerebrovascular endothelial cells. These observations provide a mechanism for the mitochondrial deficits that contribute to cerebrovascular dysfunction in patients with AD.
Alfred Yamoah, Priyanka Tripathi, Antonio Sechi, Christoph Köhler, Haihong Guo, Akila Chandrasekar, Kay Wilhelm Nolte, Christoph Jan Wruck, Istvan Katona, Jasper Anink, Dirk Troost, Eleonora Aronica, Harry Steinbusch, Joachim Weis*, Anand Goswami* *These authors contributed equally to this work
Aggregates of RNA Binding Proteins and ER Chaperones Linked to Exosomes in Granulovacuolar Degeneration of the Alzheimer’s Disease Brain
Abstract: Granulovacuolar degeneration (GVD) occurs in Alzheimer’s disease (AD) brain due to compromised autophagy. Endoplasmic reticulum (ER) function and RNA binding protein (RBP) homeostasis regulate autophagy. We observed that the ER chaperones GRP78/BiP, Sigma receptor 1 (SigR1), and VAPB were elevated in many AD patients’ subicular neurons. However, those neurons which were affected by GVD showed lower chaperone levels, and there was only minor co-localization of chaperones with GVD bodies (GVBs), suggesting that neurons lacking sufficient chaperone-mediated proteostasis enter the GVD pathway. Consistent with this notion, granular, incipient pTau aggregates in human AD and pR5 tau transgenic mouse neurons were regularly co-localized with increased chaperone immunoreactivity, whereas neurons with mature neurofibrillary tangles lacked both the chaperone buildup and significant GVD. On the other hand, APP/PS1 (APPswe/PSEN1dE9) transgenic mouse hippocampal neurons that are devoid of pTau accumulation displayed only few GVBs-like vesicles, which were still accompanied by prominent chaperone buildup. Identifying a potential trigger for GVD, we found cytoplasmic accumulations of RBPs including Matrin 3 and FUS as well as stress granules in GVBs of AD patient and pR5 mouse neurons. Interestingly, we observed that GVBs containing aggregated pTau and pTDP-43 were consistently co-localized with the exosomal marker Flotillin 1 in both AD and pR5 mice. In contrast, intraneuronal 82E1-immunoreactive amyloid-β in human AD and APP/PS1 mice only rarely co-localized with Flotillin 1-positive exosomal vesicles. We conclude that altered chaperone-mediated ER protein homeostasis and impaired autophagy manifesting in GVD are linked to both pTau and RBP accumulation and that some GVBs might be targeted to exocytosis.
May A. Beydoun, Hind A. Beydoun, Sharmin Hossain, Ziad W. El-Hajj, Jordan Weiss, Alan B. Zonderman
Clinical and Bacterial Markers of Periodontitis and Their Association with Incident All-Cause and Alzheimer’s Disease Dementia in a Large National Survey
Abstract: Microbial agents including periodontal pathogens have recently appeared as important actors in Alzheimer’s disease (AD) pathology. We examined associations of clinical periodontal and bacterial parameters with incident all-cause and AD dementia as well as AD mortality among US middle-aged and older adults. Clinical [Attachment Loss (AL); probing pocket depth (PPD)] and bacterial [pathogen immunoglobulin G (IgG)] periodontal markers were investigated in relation to AD and all-cause dementia incidence and to AD mortality, using data from the third National Health and Nutrition Examination Surveys (NHANES III, 1988-1994) linked longitudinally with National Death Index and Medicare data through January 1, 2014, with up to 26 years of follow-up. Sex- and age-specific multivariable-adjusted Cox proportional hazards models were conducted. Among those ≥65 years, AD incidence and mortality were consistently associated with probing depth, two factors and one cluster comprised of IgG titers against Porphyromonas gingivalis (P. gingivalis), Prevotella melaninogenica (P. melaninogenica) and Campylobacter rectus (C. rectus) among others. Specifically, AD incidence was linked to a composite of C. rectus and P. gingivalis titers (per SD, aHR=1.22; 95% CI, 1.04-1.43, p=0.012), while AD mortality risk was increased with another composite (per SD, aHR=1.46; 95% CI, 1.09-1.96, p=0.017) loading highly on IgG for P. gingivalis, Prevotella intermedia, Prevotella nigrescens, Fusobacterium nucleatum, C. rectus, Streptococcus intermedius, Capnocylophaga Ochracea, and P. melaninogenica. This study provides evidence for an association between periodontal pathogens and AD, which was stronger for older adults. Effectiveness of periodontal pathogen treatment on reducing sequelae of neurodegeneration should be tested in randomized controlled trials.
Masakazu Miyamoto, Akira Kuzuya, Yasuha Noda, Sakiho Ueda, Megumi Asada-Utsugi, Shinji Ito, Yoshiyasu Fukusumi, Hiroshi Kawachi, Ryosuke Takahashi, Ayae Kinoshita (Handling Associate Editor: Shun Shimohama)
Synaptic Vesicle Protein 2B Negatively Regulates the Amyloidogenic Processing of AβPP as a Novel Interaction Partner of BACE1
Abstract: Background: Given that amyloid-β (Aβ) peptide is produced and released at synapses, synaptic Aβ is one of the promising therapeutic targets to prevent synaptic dysfunction in Alzheimer’s disease (AD). Although Aβ production begins with the cleavage of the amyloid-β protein precursor (AβPP) by β-site AβPP cleaving enzyme 1 (BACE1), the mechanism on how BACE1 is involved in AβPP processing at synapses remains unclear. Objective: This study aimed to identify novel BACE1 interacting proteins regulating Aβ production at the synapse. Methods: BACE1 interacting proteins were pulled down using a mass spectrometry-based proteomics of wild-type (WT) rat brain synaptoneurosome lysates utilizing anti-BACE1 antibody. Then, a novel BACE1 interactor was identified and characterized using experimental systems that utilized transfected cells and knockout (KO) mice. Results: Synaptic vesicle protein 2B (SV2B) was identified as a novel presynaptic interaction partner of BACE1. In HEK293 cells, co-overexpression of SV2B with BACE1 significantly reduced the sAβPPβ and Aβ levels released in the media; thus, SV2B overexpression negatively affected the AβPP cleavage by BACE1. Compared with those of WT mice, the hippocampal lysates of SV2B knockout mice had significantly elevated Aβ levels, whereas the β-secretase activity and the AβPP and BACE1 protein levels remained unchanged. Finally, a fractionation assay revealed that BACE1 was mislocalized in SV2B KO mice; hence, SV2B may be involved in BACE1 trafficking downregulating the amyloidogenic pathway of AβPP. Conclusion: SV2B has a novel role of negatively regulating the amyloidogenic processing of AβPP at the presynapses.
Annie M. Racine, Alexandra Touroutoglou, Tatiana Abrantes, Bonnie Wong, Tamara G. Fong, Michele Cavallari, Thomas G. Travison, Yun Gou, Edward R. Marcantonio, David C. Alsop, Richard N. Jones, Sharon K. Inouye*, Bradford C. Dickerson* for the SAGES study group (Handling Associate Editor: Barbara Bendlin) *These authors contributed equally as co-senior authors.
Older Patients with Alzheimer’s Disease-Related Cortical Atrophy Who Develop Post-Operative Delirium May Be at Increased Risk of Long-Term Cognitive Decline After Surgery
Abstract: Background: Older surgical patients with Alzheimer’s disease (AD) dementia and delirium are at increased risk for accelerated long-term cognitive decline. Objective: Investigate associations between a probabilistic marker of preclinical AD, delirium, and long-term cognitive decline. Methods: The Successful Aging after Elective Surgery cohort includes older adults (≥70 years) without dementia who underwent elective surgery. 140 patients underwent preoperative magnetic resonance imaging and had ≥ 6 months cognitive follow-up. Cortical thickness was measured in ‘AD-Signature’ regions. Delirium was evaluated each postoperative day by the Confusion Assessment Method. Cognitive performance was assessed using a detailed neuropsychological battery at baseline; months 1, 2, and 6; and every 6 months thereafter until 36 months. Using either a General Cognitive Performance composite (GCP) or individual test scores as outcomes, we performed linear mixed effects models to examine main effects of AD-signature atrophy and the interaction of AD-signature atrophy and delirium on slopes of cognitive change from post-operative months 2-36. Results: Reduced baseline AD-signature cortical thickness was associated with greater 36-month cognitive decline in GCP (standardized beta coefficient, β = -0.030, 95% confidence interval [-0.060, -0.001]). Patients who developed delirium who also had thinner AD signature cortex showed greater decline on a verbal learning test (β = -0.100 [-0.192, -0.007]). Conclusion: Patients with the greatest baseline AD-related cortical atrophy who develop delirium after elective surgery appear to experience the greatest long-term cognitive decline. Thus, atrophy suggestive of preclinical AD and the development of delirium may be high-risk indicators for long-term cognitive decline following surgery.
Antoine Garnier-Crussard, Julien Vernaudon, Nicolas Auguste, Virginie Dauphinot, Pierre Krolak-Salmon
What Could Be the Main Levers to Promote a Timely Diagnosis of Neurocognitive Disorders?
Abstract: Background: Neurocognitive disorders (NCD) are a growing health issue and the importance of diagnosis is still debated despite the benefits of making a diagnosis appearing to be greater than the risks. Objective: The aim of the present study was to explore the perception of the main benefits and risks to perform a diagnosis workup of NCD in a population of general practitioners (GPs), specialized physicians (SPs), other healthcare professionals (OHPs), and informal caregivers (ICs), and to identify the lowest perceived benefits and the highest perceived risks that could be levers to promote a diagnosis of NCD. Methods: A standardized questionnaire was submitted to GPs, SPs, OHPs, and ICs aiming to evaluate the importance of eight benefits and eight risks related to NCD diagnosis (selected from the literature) for four prototypical clinical cases at different stages of the disease: subjective cognitive impairment/mild NCD, major NCD at mild/moderate stage, moderate stage with behavioral and psychotic symptoms, and severe stage. Results: The lowest perceived benefits of making an NCD diagnosis were “access to medical research”, “patient’s right to know”, and “initiation of symptomatic drug treatment”. The highest perceived risks of making an NCD diagnosis were “negative psychological impact for the patient”, “absence of disease-modifying treatment”, and “absence of suitable institution”. Conclusion: This study highlights the lowest perceived benefits and the highest perceived risks of making an NCD diagnosis. These benefits and risks could be modified to become levers to promote a personalized diagnosis of NCD.
Yuan Qiao*, Xin-Yi Xie*, Guo-Zhen Lin, Yang Zou, Sheng-Di Chen, Ru-Jing Ren, Gang Wang (Handling Associate Editor: Jin-Tai Yu) *These authors contributed equally to this work.
Computer-Assisted Speech Analysis in Mild Cognitive Impairment and Alzheimer’s Disease: A Pilot Study from Shanghai, China
Abstract: Background: Language dysfunction is a frequently reported symptom in Alzheimer's disease (AD). However, computer-assisted analysis of spontaneous speech in AD and mild cognitive impairment (MCI) is rarely used to date. Objective: To characterize the language impairment in AD and amnestic MCI (aMCI) with computer-based automatic analysis via the "Automatic Speech Recognition (ASR) software for cognitive impairment V1.3". Methods: A total of 64 subjects, including 20 AD patients, 20 aMCI patients, and 24 healthy controls were recruited. All subjects underwent neuropsychological testing, and spontaneous speech samples were recorded through the description of the “Cookie-Theft Picture” and then analyzed by the computerized software. Subsequently, we compared the speech parameters between the subjects and the controls. Results: We identified seven spontaneous speech parameters (percentage of silence duration, average duration of phrasal segments, average duration of silence segments, number of speech segments, number of long pauses, ratio of hesitation/speech counts and ratio of short pause/speech counts) demonstrating significant differences between the three groups (p < 0.05). All seven speech parameters significantly correlated with cognitive performance, with average duration of silence segments demonstrating the best correlation to cognitive performance on stepwise multiple linear regression analysis. Conclusion: Computer-assisted automated analysis of speech/silence segments demonstrated the potential to reflect the intrinsic linguistic impairment associated with MCI and AD. It has a promising prospect in the early detection of AD and assessment of disease severity.
Angelica Vieira Cavalcanti de Sousa, Ulrike Grittner, Dan Rujescu, Nadine Külzow*, Agnes Flöel* (Handling Associate Editor: Carlo Abbate) *These authors share last authorship.
Impact of 3-Day Combined Anodal Transcranial Direct Current Stimulation-Visuospatial Training on Object-Location Memory in Healthy Older Adults and Patients with Mild Cognitive Impairment
Abstract: Background: Associative object-location memory (OLM) is known to decline even in normal aging, and this process is accelerated in patients with mild cognitive impairment (MCI). Given the lack of curative treatment for Alzheimer’s disease, activating cognitive resources during its preclinical phase might prevent progression to dementia. Objective: To evaluate the effects of anodal transcranial direct current stimulation (atDCS) combined with an associative episodic memory training on OLM in MCI patients and in healthy elderly (HE). Methods: In a single-blind cross-over design, 16 MCI patients and 32 HE underwent a 3-day visuospatial OLM training paired with either 20 min or 30 s (sham) atDCS (1 mA, right temporoparietal cortex). Effects on immediate (training success) and long-term memory (1-month) were investigated by conducting Mixed Model analyses. In addition, the impact of combined intervention on within-session (online) and on between-session (offline) performance were explored. Results: OLM training + atDCS enhanced training success only in MCI patients, but not HE (difference n.s.). Relative performance gain was similar in MCI patients compared to HE under atDCS. No beneficial effect was found after 1 month. Exploratory analyses suggested a positive impact for online, but a negative effect on offline performance in MCI patients. In both groups, exploratory post-hoc analyses indicated an association between initially low-performers and greater benefit from atDCS. Conclusion: Cognitive training in MCI may be enhanced by atDCS, but further delineation of the impact of current brain state, as well as temporal characteristics of multi-session atDCS-training application, may be needed to induce longer-lasting effects.
Mei-Hong Lu*, Xiu-Yun Zhao*, De-en Xu*, Ji-Bo Chen,Wen-Li Ji, Ze-ping Huang, Ting-ting Pan, Lu-Lu Xue, Fen Wang, Qi-Fa Li, Yue Zhang, Ting-Hua Wang, Yuchio Yanagawa, Chun-Feng Liu, Ru-Xiang Xu, Yi-Yuan Xia, Shao Li, Quan-Hong Ma (Handling Associate Editor: Ling-Qiang Zhu) *These authors contributed equally to this work.
Transplantation of GABAergic Interneuron Progenitor Attenuates Cognitive Deficits of Alzheimer’s Disease Model Mice
Abstract: Excitatory (E) and inhibitory (I) balance of neural network activity is essential for normal brain function and of particular importance to memory. Disturbance of E/I balance contributes to various neurological disorders. The appearance of neural hyperexcitability in Alzheimer’s disease (AD) is even suggested as one of predictors of accelerated cognitive decline. In this study, we found that GAD67+, Parvalbumin+, Calretinin+, and Neuropeptide Y+ interneurons were progressively lost in the brain of APP/PS1 mice. Transplanted embryonic medial ganglionic eminence derived interneuron progenitors (IPs) survived, migrated, and differentiated into GABAergic interneuron subtypes successfully at 2 months after transplantation. Transplantation of IPs hippocampally rescued impaired synaptic plasticity and cognitive deficits of APP/PS1 transgenic mice, concomitant with a suppression of neural hyperexcitability, whereas transplantation of IPs failed to attenuate amyloid-β accumulation, neuroinflammation, and synaptic loss of APP/PS1 transgenic mice. These observations indicate that transplantation of IPs improves learning and memory of APP/PS1 transgenic mice via suppressing neural hyperexcitability. This study highlights a causal contribution of GABAergic dysfunction to AD pathogenesis and the potentiality of IP transplantation in AD therapy.
Marta Luísa Gonçalves de Freitas Pereira, Marina von Zuben de Arruda Camargo, Ariella Fornachari Ribeiro Bellan, Ana Carolina Tahira, Bernardo dos Santos, Jéssica dos Santos, Ariane Machado-Lima, Fátima L.S. Nunes, Orestes Vicente Forlenza (Handling Associate Editor: Amanda Douglass)
Visual Search Efficiency in Mild Cognitive Impairment and Alzheimer’s Disease: an Eye Movement Study
Abstract: Background: Visual search abilities are essential to everyday life activities and are known to be affected in Alzheimer’s disease (AD). However, little is known about visual search efficiency in mild cognitive impairment (MCI), a transitive state between normal aging and dementia. Eye movement studies and machine learning methods have been recently used to detect oculomotor impairments in individuals with dementia. Objective: The aim of the present study is to investigate the association between eye movement metrics and visual search impairment in MCI and AD. Methods: 127 participants were tested: 43 healthy controls, 51 with MCI, and 33 with AD. They completed an eyetracking visual search task where they had to find a previously seen target stimulus among distractors. Results: Both patient groups made more fixations on the screen when searching for a target, with longer duration than controls. MCI and AD fixated the distractors more often and for a longer period of time than the target. Healthy controls were quicker and made less fixations when scanning the stimuli for the first time. Machine-learning methods were able to distinguish between controls and AD subjects and to identify MCI subjects with a similar oculomotor profile to AD with a good accuracy. Conclusion: Results showed that eye movement metrics are useful for identifying visual search impairments in MCI and AD, with possible implications in the early identification of individuals with high-risk of developing AD.
Sascha Gill, Pauline Mouches, Sophie Hu, Deepthi Rajashekar, Frank P. MacMaster, Eric E. Smith, Nils D. Forkert, Zahinoor Ismail, for the Alzheimer’s Disease Neuroimaging Initiative
Using Machine Learning to Predict Dementia from Neuropsychiatric Symptom and Neuroimaging Data
Abstract: Background: Machine learning (ML) is a promising technique for patient-specific prediction of mild cognitive impairment (MCI) and dementia development. Neuropsychiatric symptoms (NPS) might improve the accuracy of ML models but have barely been used for this purpose. Objectives: To investigate if baseline mild behavioral impairment (MBI) status used for NPS quantification along with brain morphology features are predictive of follow-up diagnosis, median 40 months later in patients with normal cognition (NC) or MCI. Method: Baseline neuroimaging, neuropsychiatric, and clinical data from 102 individuals with NC and 239 with MCI were extracted from the Alzheimer’s Disease Neuroimaging Initiative database. Neuropsychiatric inventory questionnaire items were transformed to MBI domains using a published algorithm. Diagnosis at latest follow-up was used as the outcome variable and ground truth classification. A logistic model tree classifier combined with information gain feature selection was trained to predict follow-up diagnosis. Results: In the binary classification (NC versus MCI/AD), the optimal ML model required only two features from over 200, MBI total score and left hippocampal volume. These features correctly classified participants as remaining normal or developing cognitive impairment with 84.4% accuracy (area under the receiver operating characteristics curve [ROC-AUC] =0.86). Seven features were selected for the three-class model (NC versus MCI versus dementia) achieving an accuracy of 58.8% (ROC-AUC=0.73). Conclusion: Baseline NPS, categorized for MBI domain and duration, have prognostic utility in addition to brain morphology measures for predicting diagnosis change using ML. MBI total score, followed by impulse dyscontrol and affective dysregulation were most predictive of future diagnosis.
Alexandra Horvath, Zeinab Salman, Patrick Quinlan, Anders Wallin, Johan Svensson
Patients with Alzheimer’s Disease Have Increased Levels of Insulin-like Growth Factor-I in Serum but not in Cerebrospinal Fluid
Abstract: Background: Insulin-like growth factor-I (IGF-I) is important for amyloid-β (Aβ) metabolism, and also interacts with the brain vasculature. In previous IGF-I studies, it has not been evaluated whether Alzheimer’s disease (AD) patients had vascular comorbidities. Objective and Methods: A cross-sectional study of 40 consecutive non-diabetic AD patients and 36 healthy controls. We measured IGF-I in serum and cerebrospinal fluid (CSF) and also serum insulin. Mixed forms of AD and vascular dementia were excluded. Results: After adjustment for covariates including age, serum IGF-I level was higher in the AD group than in the controls, whereas CSF IGF-I and serum insulin were unchanged. Binary logistic regression confirmed that high serum IGF-I was associated with increased prevalence of AD [adjusted Odds Ratio (OR) = 1.83, 95% confidence interval (CI): 1.005-3.32 per standard deviation (SD) increase in serum IGF-I]. This association was more robust after exclusion of patients receiving treatment with acetylcholinesterase inhibitors or N-methyl D-aspartate (NMDA) receptor antagonists (OR = 2.23, 95 % CI: 1.10-4.48). In the total study population (n=76) as well in the AD group (n=40), serum IGF-I correlated negatively with CSF Aβ1-42, and CSF IGF-I correlated positively with CSF/serum albumin ratio, CSF total tau, and CSF phosphorylated tau. Conclusion: In AD patients without major brain vascular comorbidities, serum but not CSF levels of IGF-I were increased after correction for covariates. This association was strengthened by exclusion of patients receiving medical treatment. Overall, the results support the notion of IGF-I resistance in mild AD dementia.
Ya-Nan Ou*, Jun-Xia Zhu*, Xiao-He Hou, Xue-Ning Shen, Wei Xu, Qiang Dong, Lan Tan, Jin-Tai Yu (Handling Associate Editor: Ling-Qiang Zhu) *These authors contributed equally to this work.
Associations of Infectious Agents with Alzheimer’s Disease: A Systematic Review and Meta-Analysis
Abstract: Background: The role of infectious agents in the development of Alzheimer’s disease (AD) has long been debated, however, uncertainties still persist. Objective: We aimed to illuminate the associations between infectious agents and risk of AD comprehensively. Methods: Studies examining the associations between AD and infectious agents were identified through a systematic search of PubMed, Embase, and Cochrane library. A random-effects meta-analysis was conducted. Publication bias was explored using funnel plot. Results: Fifty-one studies were included in the systematic review, of which forty-seven studies with 108,723 participants and 4,039 AD cases were eligible for meta-analysis. Evidence based on case control studies demonstrated that Chlamydia pneumoniae [odds ratio (OR): 4.39, 95% CI = 1.81-10.67; I2 = 68%)], Human herpes virus-6 (OR: 3.97, 95% CI = 2.04-7.75; I2 = 0%), Epstein-Barr virus (OR:1.45, 95% CI = 1.00-2.08; I2 = 0%), Herpes simplex virus-1 (OR:1.34, 95% CI = 1.02-1.75; I2 = 0%), and the Herpesviridae family (OR:1.41, 95% CI = 1.15-1.74; I2 = 12%) infection were associated with a higher risk of AD. No significant evidence of publication bias was found. Conclusion: These findings strengthened the evidence that infection may play an important role in AD. Additional research is required to determine whether treatment strategies targeting infectious diseases to prevent AD are viable in the future.
Yan Cheng, Ali Ahmed, Edward Zamrini, Debby W. Tsuang, Helen M. Sheriff, Qing Zeng-Treitler
Alzheimer’s Disease and Alzheimer’s Disease-Related Dementias in Older African American and White Veterans
Abstract: Background: Racial disparity in the epidemiology of Alzheimer's disease and Alzheimer's disease-related dementias (AD/ADRD) has been reported. However, less is known about this disparity among Veterans. Objective: To estimate the racial disparity in AD/ADRD among the Veterans. Methods: Of the 5,413,418 Veterans ≥65 years receiving care at the Veterans Health Administration (1999–2016), 4,045,269 were free of prevalent AD/ADRD, schizophrenia, or bipolar disorder at baseline. Of these, 432,469 were African American. Race was self-identified and incident AD/ADRD during 20 (median 6.7) years of follow-up was ascertained using International Classification of Diseases codes. Results: Patients had a mean age of 70.4 (±6.6) years and 97.8% were men. Age-sex-adjusted incidence of AD/ADRD per 1,000 person-year was 19.3 and 10.8 for African American and white Veterans, respectively (age-sex-adjusted hazard ratio associated with African American race, 1.77; 95% confidence interval, 1.75–1.79; p<0.0001). This association remained essentially unchanged after multivariable adjustment (hazard ratio, 1.67; 95% confidence interval, 1.65–1.69; p<0.0001). Among the key baseline characteristics that were significant predictors of AD/ADRD in both races, stroke was a significantly stronger predictor among African Americans, and Hispanic ethnicity and depression among whites (p-value for all interaction, <0.0001). Conclusion: The findings of a higher incidence of AD/ADRD among African American Veterans is consistent with the findings in the general population reported in the literature, although the overall incidence appears to be lower than that in the general population. Future studies need to examine this disparity in incidence as well as the between-race heterogeneity in AD/ADRD risk.
Sophia Schedin-Weiss*, Per Nilsson*, Anna Sandebring-Matton, Michael Axenhus, Misaki Sekiguchi, Takashi Saito, Bengt Winblad, Takaomi Saido, Lars O. Tjernberg *These authors contributed equally to this work.
Proteomics Time-Course Study of App Knock-In Mice Reveals Novel Presymptomatic Aβ42-Induced Pathways to Alzheimer’s Disease Pathology
Abstract: Background: The 42 amino acids long amyloid-β peptide, Aβ42, may initiate a cascade of events leading to the severe neurodegeneration observed in Alzheimer’s disease (AD) brain. However, the underlying molecular mechanisms remain to be established. Objective: To find early Aβ42-induced AD related mechanisms, we performed a brain proteomics time-course study on a novel App knock-in AD mouse model, AppNL-F, expressing high levels of Aβ42 without AβPP overexpression artifacts. Methods: Hippocampus and cortex were analyzed separately by using 18O-labelling mass spectrometry to reveal alterations in protein levels. Pathway analysis of proteomics data was used to identify altered biological functions. Immunohistochemistry was used to further investigate a significant key regulatory protein. Results: Around 100 proteins were differently expressed in AppNL-F mice at each time point (3, 6, 9, and 18 months of age) as compared to wild type mice. Strikingly, already at 3 months of age—long before Aβ plaque development and memory impairment—several pathways, including long-term potentiation and synaptic plasticity, were downregulated, and neuritogenesis was increased. Huntingtin (HTT) was identified as an upstream regulator, i.e., a key protein affecting the levels of several proteins. Increased levels of HTT in hippocampus of AppNL-F mice was supported by immunofluorescence microscopy. Conclusion: Notably, the proteome was significantly altered already at 3 months of age, 6 months before the development of plaques. Differentially expressed proteins varied over time, indicating that increased Aβ42 levels initiate a cascade of events that eventually manifests in amyloid depositions, inflammation, and decline in memory.
Sally Hunter, Suvi R.K. Hokkanen, Hannah A.D. Keage, Jane Fleming, Thais Minett, Tuomo Polvikoski, Kieren Allinson, Carol Brayne, the Cambridge City over 75s Cohort collaboration
TDP-43 Related Neuropathologies and Phosphorylation State: Associations with Age and Clinical Dementia in the Cambridge City over-75s Cohort
Abstract: Pathologies associated with the Tar-DNA binding protein 43 KDa (TDP-43) are associated with neurodegenerative diseases and aging. Phosphorylation of cellular proteins is a well-accepted mechanism of biological control and can be associated with disease pathways. Phosphorylation state associated with TDP-43 associated pathology has not been investigated with respect to dementia status in a population representative sample. TDP-43 immunohistochemistry directed toward phosphorylated (TDP-43P) and unphosphorylated (TDP-43U) was assessed in sections of hippocampus and temporal cortex from 222 brains donated to the population representative Cambridge City over-75s Cohort. Relationships between dementia status and age at death for TDP-43 immunoreactive pathologies by phosphorylation state were investigated. TDP-43 pathologies are common in the oldest old in the population and often do not conform to MacKenzie classification. Increasing age is associated with glial (TDP-43P) and neuronal inclusions (TDP-43P and TDP-43U), neurites, and granulovacuolar degeneration (GVD). Dementia status is associated with GVD and glial (TDP-43 P) and neural inclusions (TDP-43 P and U). Dementia severity was associated with glial (TDP-43P) and neuronal inclusions (TDP-43U and TDP-43P), GVD, and neurites. The associations between dementia severity and both glial cytoplasmic inclusions and GVD were independent from other pathologies and TDP-43 neuronal cytoplasmic inclusions. TDP-43 pathology contributes to dementia status and progression in a variety of ways in different phosphorylation states involving both neurons and glia, independently from age and from classic Alzheimer-related pathologies. TDP-43 pathologies as cytoplasmic inclusions in neurons or glia or as GVD contribute independently to dementia.