Masafumi Ihara, Satoshi Saito (Handling Associate Editor: Robert Friedland)
Drug Repositioning for Alzheimer’s Disease: Finding Hidden Clues in Old Drugs
Abstract: Although more than 100 years have passed since Alois Alzheimer reported a case of Alzheimer’s disease (AD), a definitive answer to the causes of cognitive impairment in the disease remains elusive. Despite significant enthusiasm and investment from the pharmaceutical industry, clinical trials of many disease-modifying drugs for AD have been largely unsuccessful. Drug repositioning (DR) or repurposing approaches are relatively inexpensive and more reliable compared to de novo drug development in AD. About 30% of clinical trials for AD in progress around the world use the DR method and hold potential in halting the current deadlock in treatment options. By using drugs approved for other indications, these clinical trials target dysregulated pathways in AD with different or a combination of modes of action, including anti-amyloid, cardiovascular, anti-tau, anti-inflammatory, immunomodulatory, metabolic, neuroprotective, and neurotransmission-based approaches. For instance, anti-diabetic drugs, such as insulin, metformin, liraglutide, and dapagliflozin, and cardiovascular drugs, such as cilostazol, candesartan, telmisartan, prazosin, and dabigatran, could serendipitously provide previously unearthed benefits in AD. This is in line with recent thinking, which views AD as a complex multifactorial disorder, not dominated by one dominant biological factor, such as amyloid-β, and likely a confluence of many pathobiological mechanisms, including vascular dysregulation. Such increasingly available knowledge of phenotyping may be used to design ‘tailor-made’ DR and relatively homogeneous AD subpopulations specifically targeted with existing drugs based on known modes of action. It is thus expected that DR approaches will create a major paradigm shift in AD research and development.
Hermine Counil, Slavica Krantic
Synaptic Activity and (Neuro)Inflammation in Alzheimer’s Disease: Could Exosomes be an Additional Link?
Abstract: Nanosized extracellular vesicles, known as exosomes, are produced by all cell types in mammalian organisms and have been recently involved in neurodegeneration. In the brain, both glia and neurons give rise to exosomes, which contribute to their intercellular communication. In addition, brain-derived exosomes have a remarkable property to cross the blood-brain-barrier bi-directionally. In this line, exosomes of central origin have been identified in peripheral circulation and already considered as putative blood biomarkers of neurodegenerative diseases, including Alzheimer’s disease (AD). Moreover, tentative use of exosomes as vehicle for the clearance of brain-born toxic proteins or, conversely, neuroprotective drug delivery, was also envisaged. However, little is known about the precise role of exosomes in the control and regulation of neuronal functions. Based on the presence of subunits of glutamate receptors in neuron-derived exosomes on one hand, and complement proteins in astrocyte-derived exosomes on the other hand, we hypothesize that exosomes may participate in the control of neuronal excitability via inflammatory-like mechanisms both at the central level and from the periphery. In this review, we will focus on AD and discuss the mechanisms by which exosomes of neuronal, glial, and/or peripheral origin could impact on neuronal excitability either directly or indirectly.
Ganesh M. Babulal, Catherine M. Roe, Sarah H. Stout, Ganesh Rajasekar, Julie K. Wisch, Tammie L.S. Benzinger, John C. Morris, Beau M. Ances
Depression Is Associated with Tau and Not Amyloid Positron Emission Tomography in Cognitively Normal Adults
Abstract: Background: Depression is also common with older age. Alzheimer’s disease (AD) studies suggest that both cerebrospinal fluid and positron emission tomography (PET) amyloid biomarkers are associated with more depressive symptoms in cognitively normal older adults. The recent availability of tau radiotracers offers the ability to examine in vivo tauopathy. It is unclear if the tau biomarker is associated with depression diagnosis. Objective: We examined if tau and amyloid imaging were associated with a depression diagnosis among cognitively normal adults (Clinical Dementia Rating = 0) and whether antidepressants modified this relationship. Methods: Among 301 participants, logistic regression models evaluated whether in vivo PET tau was associated with depression, while another model tested the interaction between PET tau and antidepressant use. A second set of models substituted PET amyloid for PET tau. A diagnosis of depression (yes/no) was made during an annual clinical assessment by a clinician. Antidepressant use (yes/no) was determined by comparing medications the participants used to a list of 30 commonly used antidepressants. All models adjusted for age, sex, education, race, and apolipoprotein ε4. Similar models explored the association between the biomarkers and depressive symptoms. Results: Participants with elevated tau were twice as likely to be depressed. Antidepressant use modified this relationship where participants with elevated tau who were taking antidepressants had greater odds of being depressed. Relatedly, elevated amyloid was not associated with depression. Conclusions: Our results demonstrate that tau, not amyloid, was associated with a depression diagnosis. Additionally, antidepressant use interacts with tau to increase the odds of depression among cognitively normal adults.
Ehsan Tadayon, Beatrice Moret, Giulia Sprugnoli, Lucia Monti, Alvaro Pascual-Leone, Emiliano Santarnecchi, for the Alzheimer’s Disease Neuroimaging Initiative
Improving Choroid Plexus Segmentation in the Healthy and Diseased Brain: Relevance for Tau-PET Imaging in Dementia
Abstract: Recent studies have revealed the possible role of choroid plexus (ChP) in Alzheimer’s disease (AD). T1-weighted MRI is the modality of choice for the segmentation of ChP in humans. Manual segmentation is considered the gold-standard technique, but given its time-consuming nature, large-scale neuroimaging studies of ChP would be impossible. In this study, we introduce a lightweight segmentation algorithm based on the Gaussian Mixture Model (GMM). We compared its performance against manual segmentation as well as automated segmentation by Freesurfer in three separate datasets: 1) patients with structural MRIs enhanced with contrast (n=19), 2) young healthy subjects (n=20), and 3) patients with AD (n=20). GMM outperformed Freesurfer and showed high similarity with manual segmentation. To further assess the algorithm’s performance in large scale studies, we performed GMM segmentations in young healthy subjects from the Human Connectome Project (n=1,067), as well as healthy controls, mild cognitive impairment (MCI), and AD patients from the Alzheimer’s Disease Neuroimaging Initiative (n=509). In both datasets, GMM segmented ChP more accurately than Freesurfer. To show the clinical importance of accurate ChP segmentation, total AV1451 (tau) PET binding to ChP was measured in 108 MCI and 32 AD patients. GMM was able to reveal the higher AV1451 binding to ChP in AD compared with MCI. Our results provide evidence for the utility of the GMM in accurately segmenting ChP and show its clinical relevance in AD. Future structural and functional studies of ChP will benefit from GMM’s accurate segmentation.
Rasha H. Mehder, Brian M. Bennett, R. David Andrew (Handling Associate Editor: Sergio Ferreira)
Morphometric Analysis of Hippocampal and Neocortical Pyramidal Neurons in a Mouse Model of Late Onset Alzheimer's Disease
Abstract: The study of late-onset (sporadic) Alzheimer’s disease (LOAD) has lacked animal models where impairments develop with aging. Oxidative stress promotes LOAD, so we have developed an oxidative stress-based model of age-related cognitive impairment based on gene deletion of aldehyde dehydrogenase 2 (ALDH2). This enzyme is important for the detoxification of endogenous aldehydes arising from lipid peroxidation. Compared to wildtype (WT) mice, the knockout (KO) mice exhibit a progressive decline in recognition and spatial memory and AD-like pathologies. Here we performed morphometric analyses in the dorsal and ventral hippocampal CA1 regions (dCA1 and vCA1) as well as in overlying primary sensory cortex to determine if altered neuronal structure can help account for the cognitive impairment in 12-month old KO mice. Dendritic morphology was quantitatively analyzed following Golgi-Cox staining using 9 WT mice (108 neurons) and 15 KO mice (180 neurons). Four pyramidal neurons were traced per mouse in each region, followed by branched structured analysis and Sholl analysis. Compared to WT controls, the morphology and complexity of dCA1 pyramidal neurons from KOs showed significant reductions in apical and basal dendritic length, dendrite intersections, ends, and nodes. As well, spine density along dorsal CA1 apical dendrites was significantly lower in KO versus WT. In contrast, pyramidal arborization in the vCA1 and primary sensory cortex were only minimally reduced in KO versus WT mice. This major and specific reduction in synaptic input to the pyramidal neurons of the dorsal hippocampus is in keeping with studies showing that lesions to dorsal hippocampus impair primarily cognitive memory whereas ventral hippocampal lesions cause deficits in stress, emotion, and affect.
Julie K. Wisch, Catherine M. Roe, Ganesh M. Babulal, Suzanne E. Schindler, Anne M. Fagan, Tammie L. Benzinger, John C. Morris, Beau M. Ances
Resting State Functional Connectivity Signature Differentiates Cognitively Normal from Individuals Who Convert to Symptomatic Alzheimer’s Disease
Abstract: Background: Changes in resting state functional connectivity (rs-fc) occur in Alzheimer’s disease (AD), but few longitudinal rs-fc studies have been performed. Most studies focus on single networks and not a global measure of rs-fc. Although the amyloid tau neurodegeneration (AT(N)) framework is increasingly utilized by the AD community, few studies investigated when global rs-fc signature changes occur within this model. Objective: 1) Identify a global rs-fc signature that differentiates cognitively normal (CN) individuals from symptomatic AD. 2) Assess when longitudinal changes in rs-fc occur relative to conversion to symptomatic AD. 3) Compare rs-fc with amyloid, tau, and neurodegeneration biomarkers. Methods: A global rs-fc signature composed of intra-network connections was longitudinally evaluated in a cohort of cognitively normal participants at baseline (n = 335). Biomarkers, including cerebrospinal fluid (Aβ42 and tau), structural magnetic resonance imaging, and positron emission tomography were obtained. Results: Global rs-fc signature distinguished CN individuals from individuals who developed symptomatic AD. Changes occurred nearly four years before conversion to symptomatic AD. The global rs-fc signature most strongly correlated with markers of neurodegeneration. Conclusion: The global rs-fc signature changes near symptomatic onset and is likely a neurodegenerative biomarker. Rs-fc changes could serve as a biomarker for evaluating potential therapies for symptomatic conversion to AD.
Jingtian Zhang, Zhizhuang Joe Zhao, Xueqi Fu, Han Niu, Chen Hu, Yunzhou Dong, Mei-Zhen Cui, Fuqiang Zhang, Linlin Zeng, Xuemin Xu (Handling Associate Editor: Cheng-Xin Gong)
Proapoptotic Mitochondrial Carrier Homolog Protein PSAP Mediates Death Receptor 6 Induced Apoptosis
Abstract: Presenilin-associated protein (PSAP) was originally identified as a mitochondrial proapoptotic protein. To further explore the apoptotic pathway that involves PSAP, our yeast two-hybrid screen revealed that PSAP interacts with a death receptor, DR6. DR6 is a relatively less common member of the death receptor family and has been shown to mediate the neurotoxicity of amyloid-β, mutant SOD1, and prion proteins and has also been implicated in the regulation of immune cell proliferation and differentiation. Our previous study showed that DR6 induces apoptosis via a unique mitochondria-dependent pathway different from the conventional death receptor-mediated extrinsic apoptotic pathways. Thus, the interaction of DR6 with PSAP established a direct molecular link between DR6 and mitochondrial apoptotic pathway. We investigated the possible role of PSAP in DR6-induced apoptosis. Interestingly, it was discovered that knockdown of PSAP strongly inhibited DR6-induced apoptosis. To further elucidate the mechanism by which PSAP mediates DR6-induced mitochondria-dependent apoptosis, our data demonstrated that knockdown of PSAP blocked DR6-induced Bax translocation and cytochrome c release from the mitochondria. Moreover, it was found that both PSAP and DR6 form complexes with Bax, but at different subcellular locations. The DR6-Bax complex was detected in the cytosolic fraction while the PSAP-Bax complex was detected in the mitochondrial fraction. The observation that knockdown of DR6 significantly reduced the amount of PSAP-Bax complex detected in mitochondria suggests a possibility that DR6-bound Bax is transferred to PSAP upon interaction with PSAP at the mitochondria, leading to cytochrome c release and eventually apoptosis.
Maurizio Gallucci, Claudia Pallucca, Maria Elena Di Battista, Cristina Bergamelli, Vittorio Fiore, Franco Boccaletto, Michele Fiorini, Daniela Perra, Gianluigi Zanusso, Chiara Fenoglio, Maria Serpente, Daniela Galimberti, Laura Bonanni (Handling Associate Editor: Beatrice Arosio)
Anti-Cholinergic Derangement of Cortical Metabolism on 18F-FDG PET in a Patient with Frontotemporal Lobar Degeneration Dementia: A Case of the TREDEM Registry
Abstract: We present the case of a patient with an atypical course of frontotemporal lobar degeneration (FTLD) complicated by the use of an anticholinergic drug. A 70-year-old patient, followed by psychiatrists for depression and behavioral disorders, received a diagnosis of dementia with Lewy bodies (DLB) at another center due to auditory hallucinations, gait impairment, and tendency to fall. He was then admitted at our Memory Clinic Unit for behavioral disturbances, such as delusional thinking, auditory hallucinations, and memory complaints. At that time, the patient’s therapy included Lorazepam, Quetiapine, Promazine, and Biperiden. The latter was immediately suspended for the absence of extrapyramidal signs and to avoid the anticholinergic cognitive side effects. A 18F-FDG PET showed a derangement of cortical metabolism with diffusely reduced activity, and limited areas of hyperactivity involving lateral frontal and lateral temporal inferior regions bilaterally. The patient underwent a series of exams, including neuropsychological tests, 123I-MIBG scintigraphy, cerebrospinal fluid examination, and genetic analysis. A second 18F-FDG PET showed an extensive remodulation of metabolic activity: relative higher concentration of the tracer in the prefrontal and inferior temporal cortex was no more detectable. Similarly, the diffuse reduced metabolic activity could not be traced anymore. Nonetheless, the metabolic activity still appeared reduced in the frontal lobe, in the anterior cingulate bilaterally, and in the anterior part of the hemispheric fissure. Taken together, clinical and neuroimaging features would point to a FTLD-like form. Furthermore, the diagnostic work-up was likely confounded by the anticholinergic drug on 18F-FDG PET, highlighting the importance of carefully checking the patient’s pharmacology during the diagnostic process.
Andrew J. Aschenbrenner, Brian A. Gordon, Anne M. Fagan, Suzanne E. Schindler, David A. Balota, John C. Morris, Jason J. Hassenstab (Handling Associate Editor: Andrea Tales)
Neurofilament Light Predicts Decline in Attention but Not Episodic Memory in Preclinical Alzheimer’s Disease
Abstract:Background: Cerebrospinal fluid tau and neurofilament light (NfL) are two biomarkers of neurodegeneration in Alzheimer’s disease. Previous reports have shown that the influence of tau on cognitive decline depends on levels of amyloid burden whereas NfL predicts decline independently of amyloid. Most studies use a global cognitive composite as the primary outcome, and it is unknown if critical cognitive domain scores are similarly sensitive to rates of decline due to neurodegeneration. Objective: To examine the unique contribution of amyloid, tau, and NfL to rates of cognitive decline in multiple cognitive composites in a cognitively healthy, middle-aged to older adult cohort. Methods: A total of 255 participants (55% female; mean age = 66.2 years, range = 42.5 – 86.7 years) completed CSF studies and serial cognitive assessments to measure global cognition, episodic memory, and attentional control. Linear mixed effects models were used to examine rates of change on each composite score as a function of baseline biomarker levels. Results: Total tau predicted decline in attention regardless of amyloid status, but the relationship to global cognition and episodic memory was dependent on amyloid, replicating prior literature. NfL predicted decline in attention and global cognition, but not memory, and this effect was independent of amyloid status. Conclusions: These findings suggest that NfL can be used to monitor cognitive decline in aging and Alzheimer’s disease and that an attentional control composite may be a better outcome for tracking general neurodegenerative effects on cognition.
Sky Dominguez, Guadalupe Rodriguez, Hossein Fazelinia, Hua Ding, Lynn Spruce, Steven H. Seeholzer, Hongxin Dong
Sex Differences in the Phosphoproteomic Profiles of APP/PS1 Mice after Chronic Unpredictable Mild Stress
Abstract: Approximately two-thirds of those suffering with Alzheimer’s disease (AD) are women, however, the biological mechanisms underlying this sex divergence of AD prevalence remain unknown. Previous research has shown sex-specific biochemical differences that bias female mice toward pro-AD signaling on the phosphoproteomic level via corticotropin releasing factor (CRF) receptor 1 activation after CRF overexpression. Here we aimed to determine if chronic stress would induce a similar response in AD mouse models. We stressed 4-month-old APP/PS1 mice using a chronic unpredictable mild stress (CUMS) paradigm for up to 1 month. Following CUMS and behavioral assessments, we quantified whole protein and phosphoprotein levels in the cortex of stressed and non-stressed APP/PS1 mice using mass spectrometry-based proteomics. While there were no statistically significant differences at the total protein and peptide abundance levels, we found 909 and 841 statistically significant phosphopeptides between stressed and unstressed females and males, respectively, using a false discovery rate of 5%. Of these significant phosphopeptides, only 301 were the same in males and females. These results indicate that while both males and females undergo protein phosphorylation changes following stress, the peptides that are phosphorylated differ between sexes. We then used Metacore analysis to determine which biological pathways were affected. We found that several pathways were changed differently between male and female mice including NMDA receptor trafficking, cytoskeleton organization, and tau pathology. The differing biological pathways affected between males and females in response to chronic stress may help us to better understand why women are at a higher risk of AD.
Claudia Cicognola, Tugce Munise Satir, Gunnar Brinkmalm, Irena Matečko-Burmann, Lotta Agholme, Petra Bergström, Bruno Becker, Henrik Zetterberg, Kaj Blennow*, Kina Höglund* (Handling Associate Editor: Piotr Lewczuk) *These authors share senior authorship.
Tauopathy-Associated Tau Fragment Ending at Amino Acid 224 Is Generated by Calpain-2 Cleavage
Abstract: Background: Tau aggregation in neurons and glial cells characterizes tauopathies as Alzheimer’s disease (AD), progressive supranuclear palsy (PSP), and corticobasal degeneration (CBD). Tau proteolysis has been proposed as a trigger for tau aggregation and tau fragments have been observed in brain and cerebrospinal fluid (CSF). Our group identified a major tau cleavage at amino acid (aa) 224 in CSF; N-terminal tau fragments ending at aa 224 (N-224) were significantly increased in AD and lacked correlation to total tau (t-tau) and phosphorylated tau (p-tau) in PSP and CBD. Objective: Previous studies have shown cleavage from calpain proteases at sites adjacent to aa 224. Our aim was to investigate if calpain-1 or -2 could be responsible for cleavage at aa 224. Methods: Proteolytic activity of calpain-1, calpain-2, and brain protein extract was assessed on a custom tau peptide (aa 220-228), engineered with fluorescence resonance energy transfer (FRET) technology. Findings were confirmed with in-gel trypsination and mass spectrometry (MS) analysis of brain-derived bands with proteolytic activity on the FRET substrate. Finally, knock-down of the calpain-2 catalytic subunit gene (CAPN2) was performed in a neuroblastoma cell line (SH-SY5Y). Results: Calpain-2 and brain protein extract, but not calpain-1, showed proteolytic activity on the FRET substrate. MS analysis of active gel bands revealed presence of calpain-2 subunits, but not calpain-1. Calpain-2 depletion and chemical inhibition suppressed proteolysis of the FRET substrate. CAPN2 knock-down caused a 76.4% reduction of N-224 tau in the cell-conditioned media. Conclusions: Further investigation of the calpain-2 pathway in the pathogenesis of tauopathies is encouraged.
Alexandre Morin, Jorge Samper-Gonzalez, Anne Bertrand, Sébastian Ströer, Didier Dormont, Aline Mendes, Pierrick Coupé, Jamila Ahdidan, Marcel Lévy, Dalila Samri, Harald Hampel, Bruno Dubois, Marc Teichmann, Stéphane Epelbaum, Olivier Colliot
Accuracy of MRI Classification Algorithms in a Tertiary Memory Center Clinical Routine Cohort
Abstract: Background: Automated volumetry software (AVS) has recently become widely available to neuroradiologists. MRI volumetry with AVS may support the diagnosis of dementias by identifying regional atrophy. Moreover, automatic classifiers using machine learning techniques have recently emerged as promising approaches to assist diagnosis. However, the performance of both AVS and automatic classifiers has been evaluated mostly in the artificial setting of research datasets. Objective: Our aim was to evaluate the performance of two AVS and an automatic classifier in the clinical routine condition of a memory clinic. Methods: We studied 239 patients with cognitive troubles from a single memory center cohort. Using clinical routine T1-weighted MRI, we evaluated the classification performance of: 1) univariate volumetry using two AVS (volBrain and Neuroreader™); 2) Support Vector Machine (SVM) automatic classifier, using either the AVS volumes (SVM-AVS), or whole gray matter (SVM-WGM); 3) reading by two neuroradiologists. The performance measure was the balanced diagnostic accuracy. The reference standard was consensus diagnosis by three neurologists using clinical, biological (cerebrospinal fluid) and imaging data and following international criteria. Results: Univariate AVS volumetry provided only moderate accuracies (46% to 71% with hippocampal volume). The accuracy improved when using SVM-AVS classifier (52% to 85%), becoming close to that of SVM-WGM (52 to 90%). Visual classification by neuroradiologists ranged between SVM-AVS and SVM-WGM. Conclusion: In the routine practice of a memory clinic, the use of volumetric measures provided by AVS yields only moderate accuracy. Automatic classifiers can improve accuracy and could be a useful tool to assist diagnosis.
Eva Kiss*, Femke Groeneweg*, Karin Gorgas, Andrea Schlicksupp, Stefan Kins, Joachim Kirsch, Jochen Kuhse (Handling Associate Editor: Sergio Ferreira) *These authors contributed equally to this work.
Amyloid-β Fosters p35/CDK5 Signaling Contributing to Changes of Inhibitory Synapses in Early Stages of Cerebral Amyloidosis
Abstract: Early changes in inhibitory synapse connectivities are thought to contribute to the excitation/inhibition imbalance preceding neurodegeneration in Alzheimer’s disease (AD). Recently, we reported a robust increase in the level of different key-proteins of inhibitory synapses in hippocampal subregions of pre-symptomatic APPswe-PS1 mice, a model of cerebral amyloidosis. Besides increased inhibitory synaptic clusters on parvalbumin-positive projections in CA1 and CA3, we observed impaired communication between these two hippocampal areas of young APP-PS1 mice. Interestingly, the phosphorylation of gephyrin, a major organizer of inhibitory synapses, was also increased. Here, we demonstrate that the protein levels of CDK5, a kinase involved in the phosphorylation of gephyrin, and its regulatory protein p35 are also significantly increased in hippocampal subregions of young APP-PS1 mice. Consistently, the expression of hAPP-swe in cultured hippocampal neurons resulted in higher p35-protein levels, indicating a possible molecular link between increased Aβ-production and the elevated p35/CDK5 levels seen in vivo. Further, a shRNA mediated downregulation of p35-expression in hippocampal neurons correlated with a decrease in gephyrin phosphorylation and in a reduced density of synaptic γ2-GABAA-receptor clusters. These findings, together with the detection of gephyrin colocalization with CDK5 and p35 by immunostaining and proximity ligation experiments in vivo and in vitro, are supporting our hypothesis that Aβ has a profound impact on inhibitory network properties, likely mediated at least in part by p35/CDK5 signaling. This further underscores the impact of altered inhibitory synaptic transmission in AD.
Gargi Banerjee, Gareth Ambler, Ashvini Keshavan, Ross W. Paterson, Martha S. Foiani, Jamie Toombs, Amanda Heslegrave, John C. Dickson, Francesco Fraioli, Ashley M. Groves, Michael P. Lunn, Nick C. Fox, Henrik Zetterberg, Jonathan M. Schott*, David J. Werring* * These authors contributed equally to the manuscript.
Cerebrospinal Fluid Biomarkers in Cerebral Amyloid Angiopathy
Abstract: Background: There is limited data on cerebrospinal fluid (CSF) biomarkers in sporadic amyloid-β (Aβ) cerebral amyloid angiopathy (CAA). Objective: To determine the profile of biomarkers relevant to neurodegenerative disease in the CSF of patients with CAA. Methods: We performed a detailed comparison of CSF markers, comparing patients with CAA, Alzheimer’s disease (AD), and control (CS) participants, recruited from the Biomarkers and Outcomes in CAA (BOCAA) study, and a Specialist Cognitive Disorders Service. Results: We included 10 CAA, 20 AD, and 10 CS participants (mean age 68.6, 62.5, and 62.2 years, respectively). In unadjusted analyses, CAA patients had a distinctive CSF biomarker profile, with significantly lower (p<0.01) median concentrations of Aβ38, Aβ40, Aβ42, sAβPPα, and sAβPPβ. CAA patients had higher levels of neurofilament light (NFL) than the CS group (p<0.01), but there were no significant differences in CSF total tau, phospho-tau, soluble TREM2 (sTREM2), or neurogranin concentrations. AD patients had higher total tau, phospho-tau and neurogranin than CS and CAA groups. In age-adjusted analyses, differences for the CAA group remained for Aβ38, Aβ40, Aβ42, and sAβPPβ. Comparing CAA patients with amyloid-PET positive (n=5) and negative (n=5) scans, PET positive individuals had lower (p<0.05) concentrations of CSF Aβ42, and higher total tau, phospho-tau, NFL, and neurogranin concentrations, consistent with an “AD-like” profile. Conclusion: CAA has a characteristic biomarker profile, suggestive of a global, rather than selective, accumulation of amyloid species; we also provide evidence of different phenotypes according to amyloid-PET positivity. Further replication and validation of these preliminary findings in larger cohorts is needed.
Graciela Muniz Terrera, John E. Harrison, Craig W. Ritchie, Karen Ritchie
Cognitive Functions as Predictors of Alzheimer’s Disease Biomarker Status in the European Prevention of Alzheimer’s Dementia Cohort
Abstract: Alterations in Alzheimer’s disease (AD) biomarkers have been observed decades before the onset of dementia. Cognitive dysfunction, while central to the clinical diagnosis of AD, has long been considered as a late-stage phenomenon. This assumption is currently challenged and signals on some cognitive tests are now being observed within the preclinical stage. As part of the European Prevention of Alzheimer’s Dementia (EPAD) project, a battery of cognitive tests has been proposed (the EPAD Neuropsychological Examination, ENE) which is designed to detect cognitive changes in persons without clinical signs of AD but who are at high risk. Analysis of results from the 361 participants with complete measures and without dementia recruited into the EPAD Longitudinal Cohort Study that the majority have elevated biomarker levels, with significant associations between an episodic verbal memory task and tau, while amyloid-β (Aβ) was associated with a central executive task. These preliminary findings suggest that profiles of cognitive performance may be specific to a given biomarker, with a primarily hippocampal task being associated with higher levels of tau and a frontal executive task being associated with higher levels of Aβ. While previous research has focused on the relationship between cognition and levels of Aβ, our findings suggest that p-tau may potentially be a more significant correlate.
Marek Alifier, Bob Olsson, Ulf Andreasson, Nicholas C. Cullen, Jolanta Czyżewska, Piotr Jakubów, Andrzej Sieśkiewicz, Anna Stasiak-Barmuta, Tomasz Hirnle, Johannes Kornhuber, Henrik Zetterberg, Piotr Lewczuk, Kaj Blennow
Cardiac Surgery Is Associated with Biomarker Evidence of Neuronal Damage
Abstract: Background: Anesthesia and surgery is commonly associated with central nervous system sequelae and cognitive symptoms, which may be caused by neuronal injury. Neuronal injury can be monitored by plasma concentrations of the neuronal biomarkers tau and neurofilament light protein (NFL). Currently, there are no studies examining whether neuronal injury varies between surgical procedures. Objective: Our aim was to investigate if neuronal damage is more frequent after cardiac than after otolaryngeal surgery, as estimated by tau and NFL concentrations in plasma. Methods: Blood samples were drawn before, during, and after surgery and concentrations of tau, NFL, Aβ40, and Aβ42 were measured in 25 patients undergoing cardiac surgery (9 off-pump and 16 on-pump) and 26 patients undergoing otolaryngeal surgery. Results: Tau increased during surgery (1752%, p=0.0001) and NFL rose seven days post-surgery (1090%, p<0.0001) in patients undergoing cardiac surgery; even more in patients on-pump than off-pump. No changes were observed in patients undergoing otolaryngeal surgery and only minor fluctuations were observed for Aβ40 and Aβ42. Conclusion: Cardiac surgery is associated with neuronal injury, which is aggravated by extracorporeal circulation. Analyses of NFL and tau in blood may guide development of surgical procedures to minimize neuronal damage, and may also be used in longitudinal clinical studies to assess the relationship of surgery with future neurocognitive impairment or dementia.
Ragnhild Oesterhus, Ingvild Dalen, Anne K. Bergland, Dag Aarsland, Svein R. Kjosavik
Risk of Hospitalization in Patients with Alzheimer’s Disease and Lewy Body Dementia: Time to and Length of Stay
Abstract Background: Patients with dementia are at high risk of being hospitalized, but there is little knowledge whether this applies to all forms of dementia. Objective: To investigate if there are differences in hospitalization between patients with Alzheimer’s disease (AD) and Lewy body disease (LBD), and further, to compare admission rate with the general age-matched population. Methods: Patients (age 75.7±7.4) recently diagnosed with mild form of AD (n=110) or LBD (n=91) were included from outpatient clinics. The participants were followed from time of diagnosis, for five years or until death. Study outcomes were time to first hospitalization after diagnosis, number of admissions, total number of hospital days, and length of stay. Age-standardized admission ratios were calculated. Time to first admission was analyzed using competing risks regression models, and differences in number of hospitalizations and hospital days were addressed using negative binomial regression models. Results: More than 77% of the patients were admitted, largely as unplanned hospitalizations. Patients with LBD had significantly shorter time until first hospitalization (median 1.28 years, 95% CI 0.93-1.67 versus AD: 2.32 years, 95% CI 1.74-3.31) and more unplanned hospital days (median 7 days, IQR 2-26), than patients with AD (2 days, IQR 0-11). Conclusion: Our data indicates that patients with LBD have shorter time until first admission and higher admission rate than AD patients. This imposes a great burden on patients, their family, and the health care system. More knowledge about hospital admissions of people with dementia is needed. Future studies should investigate strategies to avoid potentially preventable admissions.
Yaowei Huang*, Wei Huang*, Yingwei Huang, Pingping Song, Melanie Zhang, Han-Ting Zhang, Suyue Pan, Yafang Hu *These authors contributed equally to this work.
Cdk5 Inhibitory Peptide Prevents Loss of Neurons and Alleviates Behavioral Changes in p25 Transgenic Mice
Abstract: Background: Accumulation of p25 is thought to be a causative risk factor for Alzheimer's disease (AD). As a cleaved product of p35, p25 binds to cyclin-dependent kinase 5 (Cdk5) and leads to the hyperactivity of Cdk5. Then, Cdk5/p25 phosphorylates many pathological substrates related to neurodegenerative diseases. p25 transgenic (Tg) mouse model recaptures some pathological changes of AD, including tau hyperphosphorylation, neurofibrillary tangles, neuroinflammation, and neuronal death, which can be prevented by transgenic expression of Cdk5 inhibitory peptide (CIP) before the insult of p25. Objective: In the present study, we would like to know whether adeno-associated virus serotype-9 (AAV9)-mediated CIP can protect neurons after insult of p25 in p25Tg mice. Methods: Administration of AAV9-CIP or control virus were delivered in the brain of p25Tg mice via intracerebroventricular infusions following the induction of p25. Western blotting, immunohistochemistry and immunofluorescence assessment, and animal behavioral evaluation were performed. Results: Brain atrophy, neuronal death, tau phosphorylation and inflammation in the hippocampus, and cognitive decline were observed in p25Tg mice. Administration of CIP but not the control virus in p25Tg mice reduced levels of tau phosphorylation and inflammation in the hippocampus, which is correlated with inhibition of brain atrophy and neuronal apoptosis in the hippocampus, and improvement of cognitive decline. Conclusion: Our results provide further evidence that the neurotoxicity of p25 can be alleviated by CIP.
José A. Luchsinger, Priya Palta, Brady Rippon, Luisa Soto, Fernando Ceballos, Michelle Pardo, Krystal Laing, Kay Igwe, Aubrey Johnson, Zeljko Tomljanovic, Hengda He, Christiane Reitz, William Kreisl, Qolamreza Razlighi, Jeanne Teresi, Herman Moreno, Adam M. Brickman (Handling Associate Editor: Liqin Zhao)
Sex Differences in in vivo Alzheimer’s Disease Neuropathology in Late Middle-Aged Hispanics
Abstract: Background: Females may have a higher risk of dementia than males. It is not clear if sex differences in Alzheimer’s disease (AD) neuropathology explain the higher risk of dementia in females. Sex differences in AD neuropathology might begin in middle age, decades before the sex differences in dementia are apparent. Objective: To examine sex differences in in vivo AD neuropathology in late middle age. Methods: We conducted a cross-sectional comparison of AD biomarkers among 266 Hispanic males and females (mean age: 64.0; 71.8% females) without dementia. Amyloid burden was measured as global standardized uptake value ratio (SUVR) with 18F-Florbetaben positron emission tomography (PET). Neurodegeneration was ascertained as cortical thickness in AD signature areas using brain magnetic resonance imaging. Tau burden was measured as tau SUVR in the middle/inferior temporal gyri and medial temporal cortex with 18F-MK-6240 in 75 of the 266 participants. Results: Females had higher amyloid SUVR and tau SUVR in the middle/inferior temporal gyri than males. However, females had higher cortical thickness than males and performed better in a test of verbal memory despite having higher AD neuropathology burden. Conclusion: Higher amyloid and tau in females compared to males in late middle-age may explain the reported higher dementia risk in elderly females compared to males. Longitudinal follow-up is necessary to examine whether higher amyloid and tau burden in late middle age is followed by increased neurodegeneration and cognitive decline in females as compared with males.
Hyun Ju Yang, Na Ri Kang, Young Eun Jung, Moon Doo Kim, Hyun Ghang Jeong, Tae Jin Lee, Ji Won Han, Ki Woong Kim, Joon Hyuk Park
“Choosing Wisely”: Apolipoprotein E Genetic Testing for the Diagnosis of Alzheimer’s Disease in Dementia Clinics
Abstract: Background: Apolipoprotein E (APOE) ε4 allele carriers have an increased risk of late-onset Alzheimer’s disease (AD). However, in the “Choosing Wisely” campaign for avoiding unnecessary medical tests, treatments, and procedures, APOE genetic testing is not recommended as a predictive test for AD. Objective: The aim of this study was to investigate the potential value of APOE genetic testing in a specific clinical context. Methods: Subjects with poor performance in the Korean version of the Mini-Mental Status Examination for dementia screening (MMSE-DS) with a Z-score of less than -1.5 were recruited from the public health centers. All participants underwent APOE genetic testing. Family history of dementia (FHx) was confirmed if one or more first-degree relatives had dementia. Results: Among 349 subjects, 162 (46.4%) were diagnosed with AD. APOE ε4 allele carriers had a much higher risk of AD in the group with FHx than in the group without FHx (OR = 15.81, 95% CI = 2.74–91.21 versus OR = 1.82, 95% CI = 1.00–3.27, z = 2.293, p = 0.011). The sensitivity, specificity, positive predictive value, and negative predictive value for the APOE ε4 allele were 47.7%, 90.9%, 91.3%, and 46.5% in the group with FHx. Conclusion: It would be a wise choice to perform the APOE genetic testing for the diagnosis of AD in subjects with poor performance in a screening test and a family history of dementia.
Ya-Juan Wang, Hao Hu, Yu-Xiang Yang, Chuan-Tao Zuo, Lan Tan, Jin-Tai Yu, Alzheimer’s Disease Neuroimaging Initiative (Handling Associate Editor: Yong Liu)
Regional Amyloid Accumulation and White Matter Integrity in Cognitively Normal Individuals
Abstract: Background: Recent studies have shown that amyloid-β (Aβ) burden influenced white matter (WM) integrity before the onset of dementia. Objective: To assess whether the effects of Aβ burden on WM integrity in cognitively normal (CN) individuals were regionally specific. Methods: Our cohort consisted of 71 CNs from the Alzheimer’s Disease Neuroimaging Initiative (ADNI) database who underwent both AV45 amyloid-PET and diffusion tensor imaging. Standardized uptake value ratio (SUVR) was computed across four bilateral regions of interest (ROIs) corresponding to four stages of in vivo amyloid staging model (Amyloid stages I-IV). Linear regression models were conducted in entire CN group and between APOE ε4 carriers and non-carriers. Results: Our results indicated that higher global Aβ-SUVR was associated with higher mean diffusivity (MD) in the entire CN group (p = 0.023), and with both higher MD (p = 0.015) and lower fractional anisotropy (FA) (p = 0.026) in APOE ε4 carriers. Subregion analysis showed that higher Amyloid stage I-II Aβ-SUVRs were associated with higher MD (Stage-1: p = 0.030; Stage-2: p = 0.016) in the entire CN group, and with both higher MD (Stage-1: p = 0.004; Stage-2: p = 0.010) and lower FA (Stage-1: p = 0.022; Stage-2: p = 0.014) in APOE ε4 carriers. No associations were found in APOE ε4 non-carriers and in Amyloid stage III-IV ROIs. Conclusions: Our results indicated that the effects of Aβ burden on WM integrity in CNs might be regionally specific, particularly in Amyloid stage I-II ROIs, and modulated by APOE ε4 status.
Judith R. Harrison, Sumit Mistry, Natalie Muskett, Valentina Escott-Price (Handling Associate Editor: Keeley Brookes)
From Polygenic Scores to Precision Medicine in Alzheimer’s Disease: A Systematic Review
Abstract: Background: Late-onset Alzheimer’s disease (AD) is highly heritable. The effect of many common genetic variants, single nucleotide polymorphisms (SNPs), confer risk. Variants are clustered in areas of biology, notably immunity and inflammation, cholesterol metabolism, endocytosis, and ubiquitination. Polygenic scores (PRS), which weight the sum of an individual’s risk alleles, have been used to draw inferences about the pathological processes underpinning AD. Objective: This paper aims to systematically review how AD PRS are being used to study a range of outcomes and phenotypes related to neurodegeneration. Methods: We searched the literature from July 2008-July 2018 following PRISMA guidelines. Results: 57 studies met criteria. The AD PRS can distinguish AD cases from controls. The ability of AD PRS to predict conversion from mild cognitive impairment (MCI) to AD was less clear. There was strong evidence of association between AD PRS and cognitive impairment. AD PRS were correlated with a number of biological phenotypes associated with AD pathology, such as neuroimaging changes and amyloid and tau measures. Pathway-specific polygenic scores were also associated with AD-related biologically relevant phenotypes. Conclusion: PRS can predict AD effectively and are associated with cognitive impairment. There is also evidence of association between AD PRS and other phenotypes relevant to neurodegeneration. The associations between pathway specific polygenic scores and phenotypic changes may allow us to define the biology of the disease in individuals and indicate who may benefit from specific treatments. Longitudinal cohort studies are required to test the ability of PGS to delineate pathway-specific disease activity.
Insa Feinkohl, Carola G. Schipke, Jochen Kruppa, Felix Menne, Georg Winterer, Tobias Pischon, Oliver Peters
Plasma Amyloid Concentration in Alzheimer’s Disease: Performance of a High-Throughput Amyloid Assay in Distinguishing Alzheimer’s Disease Cases from Controls
Abstract: Background. Collection of cerebrospinal fluid (CSF) for measurement of amyloid-β (Aβ) species is a gold standard in Alzheimer’s disease (AD) diagnosis, but has risks. Thus, establishing a low-risk blood Aβ test with high AD sensitivity and specificity is of outmost interest. Objective. We evaluated the ability of a commercially available plasma Aβ assay to distinguish AD patients from biomarker-healthy controls. Method. In a case-control design, we examined plasma samples from 44 AD patients (A+N+) and 49 controls (A-N-) from a memory clinic. AD was diagnosed using a combination of neuropsychological examination, CSF biomarker analysis and brain imaging. Total Aβ40 and total Aβ42 in plasma were measured through enzyme-linked immunosorbent assay (ELISA) technology using ABtest40 and ABtest42 test kits (Araclon Biotech Ltd.). Receiver operating characteristic (ROC) analyses with outcome AD were performed, and sensitivity and specificity were calculated. Results. Plasma Aβ42/40 was weakly positively correlated with CSF Aβ42/40 (Spearman’s rho 0.22; p=0.037). Plasma Aβ42/40 alone was not able to statistically significantly distinguish between AD patients and controls (AUC 0.58; 95% CI 0.46, 0.70). At a cut-point of 0.076 maximizing sensitivity and specificity, plasma Aβ42/40 had a sensitivity of 61.2% and a specificity of 63.6%. Conclusion. In this sample, the high-throughput blood Aβ assay was not able to distinguish well between AD patients and controls. Whether or not the assay may be useful in large-scale epidemiological settings remains to be seen.
Lily Li, Marina Cavuoto, Karen Biddiscombe, Kerryn E. Pike (Handling Associate Editor: Ramit Ravona-Springer)
Diabetes Mellitus Increases Risk of Incident Dementia in APOE ε4 Carriers: A Meta-Analysis
Abstract: Background: Dementia is a devastating condition for older adults, with both modifiable (e.g., diabetes mellitus) and unmodifiable risk factors (e.g., APOE ε4 allele). It remains unclear how, and to what extent, diabetes impacts dementia risk via both cerebrovascular and amyloid-β pathways. Objective: We conducted a quantitative meta-analysis to investigate the contribution of diabetes to incident dementia risk in people with ε4 and, based on the vascular-related neuropathology of diabetes, whether the combination of these factors increases risk for vascular dementia versus Alzheimer’s disease (AD). Methods: Systematic literature searches were conducted using EMBASE, MEDLINE, PsychINFO, and CINHAL databases. Pooled relative risk (RR) estimates were calculated using a random effects model, and subgroup analyses conducted across dementia subtypes. Results: Twelve studies were included, with a total of 16,200 participants. Considered concurrently, diabetes increased incident dementia risk an additional 35% for those with ε4 (RR = 1.35, 95% CI = 1.13-1.63). Similar patterns were observed for AD and vascular dementia. Conclusion: Interventions to prevent co-morbid diabetes, and diabetes-related complications and neuropathological changes, may be one way of modifying dementia risk in the vulnerable ε4 population.
Timothy Daly, Marion Houot, Anouk Barberousse, Yves Agid, Stéphane Epelbaum
Amyloid-β in Alzheimer’s Disease: A Study of Citation Practices of the Amyloid Cascade Hypothesis Between 1992 and 2019
Abstract: The amyloid cascade hypothesis (ACH) has dominated contemporary biomedical research into Alzheimer’s disease (AD) since the 1990s but still lacks definitive confirmation by successful clinical trials of anti-amyloid medicines in human AD. In this uncertain period regarding the centrality of amyloid-β (Aβ) in AD pathophysiology, and with the community apparently divided about the ACH’s validity, we used citation practices as a proxy for measuring how researchers have invested their belief in the hypothesis between 1992 and 2019. We sampled 445 articles citing Hardy & Higgins (1992, “HH92”) and classified the polarity of their HH92 citation according to Greenberg (2009)’s citation taxonomy of positive, neutral, and negative citations, and then tested four hypotheses. We identified two major attitudes towards HH92: a majority (62%) of neutral attitudes with consistent properties across the time period, and a positive attitude (35%), tending to cite HH92 earlier on within the bibliography as time went by, tending to take HH92 as an established authority. Despite the majority of neutral HH92 citations, there was a positive majority of attitudes toward different versions of the ACH and anti-amyloid therapeutic strategies (65%), suggesting that the ACH has been dominant and has undergone significant refinement since 1992. Finally, of those 110 original articles within the sample also testing the ACH empirically, an overwhelming majority (89%) returned a pro-ACH test result, suggesting that the ACH’s central claim is reproducible. Further studies will quantify the extent to which results from different methods within such original studies convergence to provide a robust conclusion vis-à-vis Aβ’s pathogenicity in AD.