Barbara A. Maher
Airborne Magnetite- and Iron-Rich Pollution Nanoparticles: Potential Neurotoxicants and Environmental Risk Factors for Neurodegenerative Disease, Including Alzheimer’s Disease
Abstract: Fewer than 5% of Alzheimer’s disease (AD) cases are demonstrably directly inherited, indicating that environmental factors may be important in initiating and/or promoting the disease. Excess iron is toxic to cells; iron overload in the AD brain may aggressively accelerate AD. Magnetite nanoparticles, capable of catalyzing formation of reactive oxygen species, occur in AD plaques and tangles; they are thought to form in situ, from pathological iron dysfunction. A recent study has identified in frontal cortex samples the abundant presence of magnetite nanoparticles consistent with high-temperature formation; identifying therefore their external, not internal source. These magnetite particles range from ~10 to 150 nm in size, and are often associated with other, non-endogenous metals (including platinum, cadmium, cerium). Some display rounded crystal morphologies and fused surface textures, reflecting cooling and crystallization from an initially heated, iron-bearing source material. Precisely-matching magnetite ‘nanospheres’ occur abundantly in roadside air pollution, arising from vehicle combustion and, especially, frictional brake-wear. Airborne magnetite pollution particles <~200 nm in size can access the brain directly via the olfactory and/or trigeminal nerves, bypassing the blood-brain barrier. Given their toxicity, abundance in roadside air, and nanoscale dimensions, traffic-derived magnetite pollution nanoparticles may constitute a chronic and pernicious neurotoxicant, and hence an environmental risk factor for AD, for large population numbers globally. Olfactory nerve damage displays strong association with AD development. Reported links between AD and occupational magnetic fields (e.g., affecting welders, machinists) may instead reflect inhalation exposure to airborne magnetic nanoparticles.
Mario F. Mendez
Bilingualism and Dementia: Cognitive Reserve to Linguistic Competency
Abstract: Despite the large number of elderly bilinguals at risk for Alzheimer’s disease (AD) and dementia worldwide, significant questions remain about the relationship between speaking more than one language and later cognitive decline. Bilingualism may impact on cognitive and neural reserve, time of onset of dementia symptoms and neuropathology, and linguistic competency in dementia. This review indicates increased cognitive reserve from executive (monitoring, selecting, inhibiting) control of two languages and increased neural reserve involving left frontal and related areas for language control. Many, but not all, studies indicate a delay in dementia symptom onset but worse hippocampal and mesiotemporal atrophy among bilinguals versus monolinguals with AD. In contrast, bilinguals do worse on language measures, and bilinguals with AD or dementia have difficulty maintaining and monitoring their second language. Together, these studies suggest that early-acquired and proficient bilingualism increases reserve through frontal-predominant executive control, and these executive abilities compensate for early dementia symptoms, delaying their onset but not the neuropathology of their disease. Finally, as executive control decreases further with advancing dementia, there is increasing difficulty inhibiting the dominant first language and staying in the second language. These conclusions must be interpreted with caution, given the problems inherent in this type of research; however, they do recommend more work on the pre-dementia neuroprotective effects and the dementia-related language impairments of bilingualism.
Sujyoti Chandra, Avik Roy, Dhruv R. Patel, Kalipada Pahan
PPARα Between Aspirin and Plaque Clearance
Abstract: Mounting evidence has identified that impaired amyloid-β (Aβ) clearance might contribute to Alzheimer's disease (AD) pathology. The lysosome-autophagy network plays an important role in protein homeostasis and cell health by removing abnormal protein aggregates via intracellular degradation. Therefore, stimulation of cellular degradative machinery for efficient removal of Aβ has emerged as a growing field in AD research. However, mechanisms controlling such pathways and drugs to promote such mechanisms are poorly understood. Aspirin is a widely used drug throughout the world and recent studies have identified a new function of this drug. At low doses, aspirin stimulates lysosomal biogenesis and autophagy to clear amyloid plaques in an animal model of AD. This review delineates such functions of aspirin and analyzes underlying mechanisms that involve peroxisome proliferator-activated receptor alpha (PPARα)-mediated transcription of transcription factor EB (TFEB), the master regulator of lysosomal biogenesis.
Jadwiga Attier-Zmudka*, Jean-Marie Sérot* *These authors contributed equally to this work.
A Particularly Tragic Case of Possible Alzheimer’s Disease, that of Marshal Pétain
Abstract: After World War I and more particularly in June 1940, the prestige of French Marshal Philippe Pétain, considered as the winning general the battle of Verdun, was very high. He became President of Council while the French army was unable to stop the German offensives. But five years later he was sentenced to death for high treason. By rereading his bibliography from a medical perspective, it is possible to find multiple suggestive events and to affirm a posteriori Pétain suffered from a neurodegenerative disorder, whose first signs appeared in the 1930s, suggestive of Alzheimer's disease, which had an impact on French politics. The modern medical knowledge of this disease casts a new light on the behavior of Petain during the last war.
Carlo Abbate, Pietro D. Trimarchi, Silvia Inglese, Sarah Damanti, Giulia A.M. Dolci, Simona Ciccone, Paolo D. Rossi, Daniela Mari, Beatrice Arosio, Renzo Bagarolo, Fabrizio Giunco, Matteo Cesari
Does the Right Focal Variant of Alzheimer’s Disease Really Exist? A Literature Analysis
Abstract: Background: Alzheimer’s disease (AD) is a clinically heterogeneous disease. Multiple atypical syndromes, distinct from the usual amnesic phenotype, have been described. In this context, the existence of a right variant of AD (RAD), characterized by enduring visuospatial impairment associated with right-sided asymmetric brain damage, has been proposed. However, to date, this phenotype remains controversial. In particular, its peculiar characteristics and the independence from more prevalent cases (especially the posterior cortical atrophy syndrome) have to be demonstrated. Objective: To explore the existence of focal RAD on the basis of existing literature. Methods: We performed a literature search for the description of atypical AD presentations, potentially evoking cases of focal RAD. To be considered as affected by RAD, the described cases had to present: 1) well documented right-sided asymmetry at neuroimaging; 2) predominant cognitive deficits localizable on the right hemisphere; 3) no specific diagnosis of a known variant of AD. Results: Twenty-one cases were found in the literature, but some of them were subsequently excluded because some features of a different clinical syndrome were overlapped with the clinical features of RAD. Thirteen positive cases, three of them with pathologically confirmed AD, remained. A common right clinical-radiological syndrome, characterized by memory and visuospatial impairment with temporal and parietal involvement, consistently emerged. However, the heterogeneity among the reports prevented a definitive and univocal description of the syndrome. Conclusion: Even if sporadic observations strongly support the existence of a focal RAD, no definitive conclusions can still be drawn about it as an independent condition.
Takashi Tarumi, Heidi Rossetti, Binu P. Thomas, Thomas Harris, Benjamin Y. Tseng, Marcel Turner, Ciwen Wang, Zohre German, Kristin Martin-Cook, Ann M. Stowe, Kyle B. Womack, Dana Mathews, Diana R. Kerwin, Linda Hynan, Ramon Diaz-Arrastia, Hanzhang Lu, C. Munro Cullum, Rong Zhang (Handling Associate Editor: Ozioma Okonkwo)
Exercise Training in Amnestic Mild Cognitive Impairment: A One-Year Randomized Controlled Trial
Abstract: Background: The current evidence is inconclusive to support the benefits of aerobic exercise training (AET) for preventing neurocognitive decline in patients with amnestic mild cognitive impairment (aMCI). Objective: To examine the effect of a progressive, moderate-to-high intensity AET program on memory and executive function, brain volume, and cortical amyloid-β (Aβ) plaque deposition in aMCI patients. Methods: This is a proof-of-concept trial that randomized 70 aMCI patients to 12 months of AET or stretching and toning (SAT, active control) interventions. Primary neuropsychological outcomes were assessed by using the California Verbal Learning Test-second edition (CVLT-II) and the Delis–Kaplan Executive Function System (D-KEFS). Secondary outcomes were the global and hippocampal brain volumes and the mean cortical and precuneus Aβ deposition. Results: Baseline cognitive scores were similar between the groups. Memory and executive function performance improved over time but did not differ between the AET and SAT groups. Brain volume decreased and precuneus Aβ plaque deposition increased over time but did not differ between the groups. Cardiorespiratory fitness was significantly improved in the AET compared with SAT group. In amyloid positive patients, AET was associated with reduced hippocampal atrophy when compared with the SAT group. Conclusions: The AET and SAT groups both showed evidence of slightly improved neuropsychological scores in previously sedentary aMCI patients. However, these interventions did not prevent brain atrophy or increases in cortical Aβ deposition over 12 months. In amyloid positive patients, AET reduced hippocampal atrophy when compared with the SAT group.
Li Xiong, Andreas Charidimou, Marco Pasi, Gregoire Boulouis, Thanakit Pongpitakmetha, Markus D. Schirmer, Sanjula Singh, Emily Benson, Edip M. Gurol, Jonathan Rosand, Steven M. Greenberg, Alessandro Biffi, Anand Viswanathan
Predictors for Late Post-Intracerebral Hemorrhage Dementia in Patients with Probable Cerebral Amyloid Angiopathy
Abstract: Background and Objective: Cerebral amyloid angiopathy (CAA) accounts for the majority of lobar intracerebral hemorrhage (ICH); however, the risk factors for dementia conversion after ICH occurrence in CAA patients is unknown, especially in the long-term period after ICH. Therefore, we aimed to unravel the predictors for late post-ICH dementia (6 months after ICH event) in probable CAA patients. Methods: From a large consecutive MRI prospective cohort of spontaneous ICH (2006-2017), we identified probable CAA patients (modified Boston criteria) without dementia 6 months post-ICH. Cognitive outcome during follow-up was determined based on the information from standardized clinical visit notes. We used Cox regression analysis to investigate the association between baseline demographic characteristics, past medical history, MRI biomarkers, and late post-ICH dementia conversion (dementia occurred after 6 months). Results: Among 97 non-demented lobar ICH patients with probable CAA, 25 patients (25.8%) developed dementia during a median follow-up time of 2.5 years (IQR 1.5-3.8 years). Pre-existing mild cognitive impairment, increased white matter hyperintensities (WMH) burden, the presence of disseminated cortical superficial siderosis (cSS), and higher total small vessel disease score for CAA were all independent predictors for late dementia conversion. Conclusion: In probable CAA patients presenting with lobar ICH, high WMH burden and presence of disseminated cSS are useful neuroimaging biomarkers for dementia risk stratification. These findings have implications for clinical practice and future trial design.
Qiankun Quan, Yihua Qian, Xi Li, Ming Li (Handling Associate Editor: Xingchun Gou)
CDK5 Participates in Amyloid-β Production by Regulating PPARγ Phosphorylation in Primary Rat Hippocampal Neurons
Abstract: Cyclin-dependent kinase 5 (CDK5) in adipose tissue mediates peroxisome proliferator-activated receptor γ (PPARγ) phosphorylation at Ser273 to inhibit its activity, causing PPARγ target gene expression changes. Among these, insulin-degrading enzyme (IDE) degrades amyloid-β peptide (Aβ), the core pathological product of Alzheimer’s disease (AD), whereas β-amyloid cleavage enzyme 1 (BACE1) hydrolyzes amyloid-β protein precursor (AβPP). Therefore, we speculated that CDK5 activity in the brain might participate in Aβ production, thereby functioning as a key molecule in AD pathogenesis. To confirm this hypothesis, we transduced primary rat hippocampal neurons using CDK5-expressing lentiviral vectors. CDK5 overexpression increased PPARγ Ser273 phosphorylation, decreased IDE expression, increased BACE1 and AβPP expression, increased Aβ levels, and induced neuronal apoptosis. The CDK5 inhibitor roscovitine effectively reversed these CDK5 overexpression-mediated effects. Moreover, silencing of the Cdk5 gene via CDK5 shRNA-expressing lentiviral vectors in primary hippocampal neurons did not exert any protective effect against normal neuronal apoptosis, nor were significant effects observed on Aβ levels, PPARγ phosphorylation, or PPARγ target gene expression in the cells. However, Cdk5 gene silencing exhibited a neuroprotective effect in the Aβ-induced AD neuron model by effectively inhibiting the Aβ-induced neuronal apoptosis, PPARγ phosphorylation, PPARγ expression downregulation, and PPARγ target gene expression changes, and reducing Aβ levels. In conclusion, this study demonstrated that CDK5 played an important role in the pathogenesis of AD. Specifically, CDK5 participated in Aβ production by regulating PPARγ phosphorylation. Targeted therapy against CDK5 could effectively reduce and reverse the neurotoxic effects of Aβ and may represent a novel approach for AD treatment.
Wenhao Zhu*, Hao Huang*, Shiqi Yang, Xiang Luo, Wenzhen Zhu, Shabei Xu, Qi Meng, Chengchao Zuo, Kun Zhao, Hesheng Liu, Yong Liu, Wei Wang (Handling Associate Editor: Bing Zhang) *aThese authors contributed equally to this work.
Dysfunctional Architecture Underlies White Matter Hyperintensities with and without Cognitive Impairment
Abstract: Background: White matter hyperintensities (WMH) are common in older adults and are associated with cognitive decline. However, little is known about the functional changes underlying cognitive decline in WMH subjects. Objectives: To investigate whole-brain functional connectivity (FC) underpinnings of cognitive decline in WMH subjects using univariate and multivariate analyses. Methods: Twenty-three WMH subjects with mild cognitive impairment (WMH-MCI), 43 WMH subjects with no cognitive impairment (WMH-nCI), and 55 healthy controls underwent resting-state functional MRI scans. Whole-brain FC was calculated using the fine-grained human Brainnetome Atlas, followed by performance of between-group comparisons and FC-cognition correlation analysis. A multivariate analysis using support vector machine (SVM) was performed to classify WMH-MCI and WMH-nCI subjects based on FC. Results: Both the WMH-MCI and WMH-nCI subjects exhibited characteristic impaired FC patterns. Markedly reduced FC involving subcortical nuclei and cortical hub regions of cognitive networks, especially the cingulate cortex, was identified in the WMH-MCI patients. In the WMH-MCI group, several connections involving the cingulate cortex were associated with cognitive decline. The exploratory mediation analyses indicated that FC alterations could partially explain the association between WMH and cognition. Furthermore, an SVM classifier based on FC distinguished WMH-MCI and WMH-nCI subjects with 78.8% accuracy. Connections that contributed most to the classification showed a similar distribution as the connections identified in the univariate analysis. Conclusions: This study provides a new window into the pathophysiology of cognitive impairment in WMH subjects and offer a novel and potential approach for early detection of the cognitive impairment in WMH subjects at the individual level.
Alireza Showraki, Geetanjali Murari, Zahinoor Ismail, Joseph J. Barfett, Luis Fornazzari, David G. Munoz, Tom A. Schweizer, Corinne E. Fischer
Cerebrospinal Fluid Correlates of Neuropsychiatric Symptoms in Patients with Alzheimer’s Disease/Mild Cognitive Impairment: A Systematic Review
Abstract: Background: Neuropsychiatric symptoms (NPS) are common, accelerate the conversion to dementia, and are associated with increased caregiver burden in Alzheimer’s disease (AD) and mild cognitive impairment (MCI). Objective: The aim of this study is to identify potential associations between the core cerebrospinal fluid (CSF) biomarkers (amyloid/tau) and NPS in AD/MCI. Methods: For this systematic review, four databases, PubMed (1946-2018), Cochrane (2005-2018), EMBASE (1947-2018), and PsycINFO (1806-2018) were searched for relevant observational studies using an extensive list of keywords. English studies were selected for critical appraisal based on our inclusion/exclusion criteria. Inclusion criteria were defined as 1) at least one AD CSF biomarker has been measured; 2) at least one NPS has been assessed; and 3) analysis has been done to examine the association between core AD CSF biomarker and NPS (main outcome). Animal, postmortem, and review studies were excluded. Results: In total, 21 studies qualified for the systematic review. The overall picture regarding the association between NPS and AD CSF biomarkers is conflicting. However, agitation/aggression was significantly and consistently related to core AD CSF biomarkers. Moreover, depression was the only NPS to occasionally be associated with lower core AD CSF pathology. Conclusion: Our study has revealed agitation/aggression as the most consistent NPS related to core AD CSF biomarkers. Future studies are required to focus on other neglected NPS domains such as disinhibition. Moreover, why depression was the only NPS inversely associated with core AD CSF pathology remains to be elucidated. Our study also revealed a great degree of heterogeneity, hence calling for a more standardized “objective” approach for the evaluation of NPS.
Donel M. Martin, Adith Mohan, Angelo Alonzo, Nicola Gates, Oyetunde Gbadeyan, Marcus Meinzer, Perminder Sachdev, Henry Brodaty, Colleen Loo (Handling Associate Editor: Olivia Küster)
A Pilot Double-Blind Randomized Controlled Trial of Cognitive Training Combined with Transcranial Direct Current Stimulation for Amnestic Mild Cognitive Impairment
Abstract: Background: There is currently no effective intervention for improving memory in people at increased risk for dementia. Cognitive training (CT) has been promising, though effects are modest, particularly at follow-up. Objective: To investigate whether adjunctive non-invasive brain stimulation (transcranial direct current stimulation, tDCS) could enhance the memory benefits of CT in amnestic mild cognitive impairment (aMCI). Methods: Participants with aMCI were randomized to receive CT with either Active tDCS (2 mA for 30 min and 0.016 mA for 30 min) or Sham tDCS (0.016 mA for 60 min) for 15 sessions over a period of 5 weeks in a double-blind, sham-controlled, parallel group clinical trial. The primary outcome measure was the California Verbal Learning Task 2nd Edition. Results: 68 participants commenced the intervention. Intention-to-treat (ITT) analysis showed that the CT + Active tDCS group significantly improved at post treatment (p = 0.033), and the CT + Sham tDCS group did not (p = 0.050), but there was no difference between groups. At the 3-month follow-up, both groups showed large-sized memory improvements compared to pre-treatment (CT + Active tDCS: p < 0.01, d = 0.99; CT + Sham tDCS: p < 0.01, d = 0.74), although there was no significant difference between groups. Conclusion: This study found that CT + Active tDCS did not produce greater memory improvement compared to CT + Sham tDCS. Large-sized memory improvements occurred in both conditions at follow-up. One possible interpretation, based on recent novel findings, is that low intensity tDCS (used as ‘sham’) may have contributed biological effects. Further work should use a completely inert tDCS sham condition.
Shinji Matsunaga, Hiroshige Fujishiro, Hajime Takechi
Efficacy and Safety of Cholinesterase Inhibitors for Mild Cognitive Impairment: A Systematic Review and Meta-Analysis
Abstract: Background: The clinical benefit of cholinesterase inhibitors (ChEIs) for mild cognitive impairment (MCI) remains inconclusive. Objective: We performed a systematic review and meta-analysis of the efficacy/safety of ChEIs on subjects with MCI. Methods: We included randomized controlled trials (RCTs) of ChEIs in subjects with MCI, using cognitive function scores as a primary outcome measure. Results: Fourteen RCTs (six using donepezil, four using galantamine, and four using rivastigmine) with 5,278 subjects were included. We found no significant difference in cognitive function scores between the ChEIs and placebo groups [standardized mean difference (SMD) = −0.06, p = 0.38, I2 = 76%]. However, in the secondary outcomes, ChEIs were associated with a lower incidence of progression to dementia compared with placebo (risk ratio = 0.76, the number needed to treat = 20). For safety outcomes, ChEIs were associated with a lower prevalence of fall than placebo. On the other hand, compared with placebo, ChEIs were associated with a higher incidence of discontinuation due to all causes, discontinuation due to adverse events, at least one adverse event, abnormal dreams, diarrhea, dizziness, headache, insomnia, loose stools, muscle cramps, nausea, vomiting, and weight loss. Conclusions: Although ChEIs have a slight efficacy in the treatment of MCI, there are many safety issues. Therefore, ChEIs are difficult to recommend for MCI. However, the efficacy and safety of ChEIs on MCI with a biomarker-based diagnosis is unclear. Further RCTs are needed to confirm the efficacy and safety of ChEIs when used for individual neuropathological classifications of MCI.
Rita El-Hayeck, Rafic Baddoura, Amine Wehbé, Nazem Bassil, Salam Koussa, Karine Abou Khaled, Sami Richa, Rita Khoury, Abbas Alameddine, François Sellal (Handling Associate Editor: Benjamin Cretin)
An Arabic Version of the Mini-Mental State Examination for the Lebanese Population: Reliability, Validity, and Normative Data
Abstract: Background: The Mini-Mental State Examination (MMSE) has not been validated in the Lebanese population and no normative data exist at the national level. Objective: To evaluate the reliability and validity of an Arabic version of MMSE developed by the “Groupe de Travail sur les Démences de l’Université Saint Joseph” (A-MMSE(GTD–USJ)) and to provide normative data by gender, age, and education in adults over 55. Methods: Study design: national cross-sectional survey. Study population: 1,010 literate community-dwelling Lebanese residents aged 55 and above. Outcomes: reproducibility, internal consistency, sensitivity, specificity, predictive values, and area under the curve of the A-MMSE(GTD-USJ) for the detection of cognitive impairment using the Clinical Dementia Rating (CDR) as the gold standard. Normative data were established from 720 healthy adults. A-MMSE(GTD-USJ) scores corresponding to the 5th, 10th, 15th, and 50th percentiles were identified according to gender, age, and education. Results: Intra-rater and inter-rater test-retest score correlations were 0.89 and 0.72, respectively. Cronbach alpha coefficient for internal consistency of the A-MMSE(GTD-USJ) was 0.71. A threshold value of 23 provided a sensitivity of 80% and a specificity of 89.4%. The area under the curve was 0.92. A-MMSE(GTD-USJ) scores increased with education and decreased with age. Women had significantly lower scores than men. Normative data for A-MMSE(GTD-USJ) stratified by gender, age, and education were generated. Conclusion: In reference to the CDR, the A-MMSE(GTD-USJ) is a valid tool to assess cognitive status among Lebanese subjects aged 55 and above. Normative data will help clinicians in detecting cognitive impairment in this population.
Luis Ruano, Milton Severo, Andreia Sousa, Catarina Ruano, Mariana Branco, Rui Barreto, Sandra Moreira, Natália Araújo, Paula Pinto, Joana Pais, Nuno Lunet, Vítor Tedim Cruz (Handling Associate Editor: Claudia Suemoto)
Tracking Cognitive Performance in the General Population and in Patients with Mild Cognitive Impairment with a Self-Applied Computerized Test (Brain on Track)
Abstract: Repeated measurements could be helpful to identify patients with early cognitive decline. We compare the variation of cognitive performance over one year in patients with mild cognitive impairment (MCI) and healthy individuals using the Brain on Track self-applied computerized test (BoT). The study was initiated 30 patients with probable MCI and 377 controls from a population-based cohort, who performed the BoT test from home every three months for one year. The scores were compared using a linear mixed-effects model. All participants increased their scores in the first tests, after 120 days MCI patients started to decline, with a statistically significant higher rate. The area under the curve to detect MCI was 0.94. We identified a significant decline in cognitive performance over one year in patients with MCI using BoT and the test presented a high discriminative ability.
Kay Deckers, Dorina Cadar, Martin P.J. van Boxtel, Frans R.J. Verhey, Andrew Steptoe, Sebastian Köhler
Modifiable Risk Factors Explain Socioeconomic Inequalities in Dementia Risk: Evidence from a Population-Based Prospective Cohort Study
Abstract: Background: Differences in dementia risk across the gradient of socioeconomic status (SES) exist, but their determinants are not well understood. Objective: This study investigates whether health conditions and lifestyle-related risk factors explain the SES inequalities in dementia risk. Methods: 6,346 participants from the English Longitudinal Study of Ageing were followed up from 2008/2009 until 2014/2015. We used Cox regression adjusted for age, gender, wealth/education, and clustering at the household level to examine the association between SES markers (wealth, education) and time to dementia in a structural equation model including potential mediation or effect modification by a weighted compound score of twelve modifiable risk and protective factors for dementia (‘LIfestyle for BRAin health’ (LIBRA) score). Results: During a median follow-up of 6 years, 192 individuals (3.0%) developed dementia. LIBRA scores decreased with increasing wealth and higher educational level. A one-point increase in the LIBRA score was associated with a 13% increase in dementia risk (hazard ratio (HR) = 1.13, 95% confidence interval 1.07-1.19). Higher wealth was associated with a decreased dementia risk (HR = 0.58, 0.39-0.85). Mediation analysis showed that 52% of the risk difference between the highest and lowest wealth tertile was mediated by differences in LIBRA (indirect effect: HR = 0.75, 0.66-0.85). Education was not directly associated with dementia (HR = 1.05, 0.69-1.59), but was a distal risk factor for dementia by explaining differences in wealth and LIBRA scores (indirect effect high education: HR = 0.92, 0.88-0.95). Conclusion: Socioeconomic differences in dementia risk can be partly explained by differences in modifiable health conditions and lifestyle factors.
Ning Su, Xinyu Liang, Ming Yao, Li-Xin Zhou, Quan Wang, Zheng-Yu Jin, Shu-Yang Zhang, Li-Ying Cui, Gaolang Gong, Yi-Cheng Zhu*, Jun Ni* *These authors contributed equally to this work.
Cerebral Microbleeds Correlated with White Matter and Hippocampal Volumes in Community-Dwelling Populations
Abstract: Background: Few studies have investigated the correlation between cerebral microbleeds (CMBs), a hemorrhagic imaging marker of cerebral small vessel disease (CSVD), and brain volume. Objective: We investigated the association between the burden and locations of CMBs and brain volume in community-dwelling populations. Methods: Data were obtained from 1,029 participants who underwent brain magnetic resonance imaging (MRI) and APOE genotyping. Volumes of the whole brain, subcortical white matter (WM), cortical gray matter (GM), and hippocampus were extracted. Linear regression models were used to investigate the relationship between the CMB burden and their location with structural changes. Results: Regarding burden, participants with ≥3 CMBs had significantly lower whole brain (β = -1.124, p = 0.0133), subcortical WM (β = -1.020, p = 0.0043), and hippocampus (β = -0.015, p = 0.0088) volumes than those without CMBs. Regarding location and burden, the presence of ≥3 strictly lobar CMBs was negatively associated with whole brain volume (β = -2.838, p = 0.0088). Additionally, higher CMB burdens in strictly lobar locations or deep/mixed locations were associated with lower subcortical WM volume (β = -1.689, p = 0.0482; β = -0.872, p = 0.0464, respectively). Finally, the presence of ≥3 deep/mixed CMBs was associated with lower hippocampus volume (β = -0.018, p = 0.0088), and these associations were independent of other ischemic markers of CSVD. However, the CMB burden and distributional pattern did not correlate with cortical GM volumes. Conclusion: A higher CMB burden, in specific locations, is associated with decreased brain volumes in community-dwelling populations.
Charlotte Graham, Estibaliz Santiago-Mugica, Zeinab Abdel-All, Mosi Li, Richard McNally, Rajesh N. Kalaria, Elizabeta B. Mukaetova-Ladinska
Erythrocytes as Biomarkers for Dementia: Analysis of Protein Content and Alpha-Synuclein
Abstract: Background: Discovering biomarkers for dementia is a pivotal step toward successful early diagnosis and treatment. Although plasma biomarkers have been explored, no consensus has been reached. Alpha-synuclein (AS), a 14 kDa synaptic protein associated with several neurodegenerative diseases, exists natively within erythrocytes (ERC). This protein is characteristic of Lewy body diseases, in which it aggregates into toxic Lewy bodies. As ERC are implicated in dementia, they are a potential target for future biomarkers. Objective: The aims of this study were to assess AS levels within ERC and whether AS can be used as a peripheral biomarker to differentiate between dementia and aged matched healthy control subjects. Methods: A total of 114 samples (60 aging controls, 36 Alzheimer’s disease, 12 vascular dementia (VaD) and 6 dementia with Lewy bodies (DLB) subjects) were analyzed. We used Bradford assay to measure protein concentration, indirect ELISA to detect levels of AS, and immunoblotting to identify AS composition. Data were analyzed with nonparametric tests. Results: AS oligomers were present in dementia blood samples, whereas in controls, AS was largely monomeric. There was a significant increase in AS levels in DLB whole blood (p=0.005; Kruskal-Wallis test), with a sensitivity and specificity of 100.0% and 93.9%. Protein concentrations in ERC isolated at pH 5.7 were significantly increased in dementia patients compared to controls (17.58 versus 40.33 μg/ml; p≤0.005; Mann-Whitney test). In the VaD group, the protein concentration in the pH5.7 ERC fraction had sensitivity and specificity of 91.7% and 62.1%. Conclusions: ERC protein concentration and AS levels have a potential for development of a novel diagnostic dementia blood test.
Ruolun Qiu, Jae Eun Ahn, Robert Alexander, Michael A. Brodney, Ping He, Claire Leurent, Jessica Mancuso, Richard A. Margolin, Ekaterina Tankisheva, Danny Chen (Handling Associate Editor: M. Paul Murphy)
Safety, Tolerability, Pharmacokinetics, and Pharmacodynamic Effects of PF-06751979, a Potent and Selective Oral BACE1 Inhibitor: Results from Phase I Studies in Healthy Adults and Healthy Older Subjects
Abstract: PF-06751979 is a selective inhibitor of the beta-site amyloid precursor protein cleaving enzyme 1, which is a key aspartyl protease in the generation of amyloid-β (Aβ) peptides, thought to be critical for the cerebral degeneration observed in Alzheimer’s disease. Two Phase I studies (NCT02509117, NCT02793232) investigated the safety/tolerability, pharmacokinetics (PK), and pharmacodynamics (PD) of PF-06751979. Single-ascending doses up to 540 mg and multiple-ascending doses up to 275 mg once daily (QD) in healthy adults, and multiple doses of 50 mg or 125 mg QD in healthy older subjects were assessed. PF-06751979 was well tolerated at all doses given, and all treatment-related adverse events (AEs) were mild to moderate. PK parameters remained consistent across the PF 06751979 QD dosing regimens, and no notable food effects were observed. PD analysis showed that PF-06751979 reduced the cerebrospinal fluid (CSF) and plasma levels of Aβ peptides in a dose-dependent manner, with the greatest reductions observed in subjects treated with 275 mg QD (approximately 92% and 93% reduction in CSF Aβ1-40 and Aβ1-42 observed at 24 h after Day 14 dose, respectively). A drug interaction study (NCT03126721) using midazolam indicated that there was no clinically meaningful effect of multiple doses of PF-06751979 100 mg QD on the PK of single-dose midazolam in healthy adults. Overall, these data suggest that PF-06751979 with daily dosing is favorable for further clinical development.
Tao Liang, Feixiao Xue, Weijian Hang, Bin Wen, Qianying Zhang, Jiehui Chen, Xiaofeng Liu, Juan Chen (Handling Associate Editor: Qing Tian)
Neuron-Specific Apolipoprotein E4 (1-272) Fragment Induces Tau Hyperphosphorylation and Axonopathy via Triggering Endoplasmic Reticulum Stress
Abstract: Apolipoprotein (apo) E4 is the major genetic risk factor for Alzheimer's disease (AD). It is shown that apoE4 preferentially undergoes aberrant cleavage in neurons, yielding neurotoxic C-terminal-truncated apoE4 fragment. Endoplasmic reticulum (ER) stress has also been known to be involved in the pathogenesis of AD. However, little is known about the contribution of ER stress to the neurotoxicity of apoE4 fragment. In the present study, we established the neuron-specific expression human C-terminal-truncated apoE4(1-272) fragment transgenic mice and also transfected apoE4(1-272) fragment in neuroblastoma N2a cells. We found that human apoE4(1-272) fragment could trigger ER stress as evidenced by increasing the expression of ER stress markers both in vivo and in vitro. Meanwhile, the apoE4(1-272) transgenic mice presented obviously AD-like neuropathological changes, including the impairment of spatial learning and memory, prominent axonal morphological changes, and hyperphosphorylation of tau. At the same time, we also found that glycogen synthase kinase-3 activities were significantly increased. Furthermore, these neuropathological changes, especially tau hyperphosphorylation and axonal transport impairment, were significantly rescued by the ER stress protector 4-phenylbutyric acid (4-PBA) in apoE4(1-272)-transfected N2a cells. Pretreatment with 4-PBA not only decreased the protein expression of immunoglobulin binding protein (BiP) and C/EBP-homologous protein (CHOP), but also significantly reversed these defects in axonal transport. These results suggested that the neurotoxic effects of apoE4(1-272) fragment found in AD subjects, at least in part, through triggering ER stress and inducing tau hyperphosphorylation, led to the enduring impairment of axonal transport.
Brice Laurens*, Vincent Planche*, Stéphanie Cubizolle, Léa Declerck, Sandrine Dupouy, Maïté Formaglio, Lejla Koric, Magali Seassau, Caroline Tilikete, Alain Vighetto, Mathieu Ceccaldi, François Tison *These authors contributed equally to this work.
A Spatial Decision Eye-Tracking Task in Patients with Prodromal and Mild Alzheimer’s Disease
Abstract: Background/Objective: Performances on spatial decision eye-tracking tasks are known to be impaired in patients with moderate Alzheimer’s disease (AD), but the clinical relevance of this deficit during earlier stages of AD remains unclear. Methods: This study recruited patients with amnestic mild cognitive impairment (aMCI, prodromal AD), patients with mild AD, and age-matched controls from three French memory clinics. Participants’ ability to make spatial judgments and decisions was assessed with an eye-tracking system, and cognitive performance on conventional neuropsychological tests was evaluated. Results: We enrolled 26 controls, 25 aMCI patients (median Mini-Mental State Exam [MMSE] 26), and 23 mild-AD patients (median MMSE 23). Patients with mild AD had higher error rates on the spatial decision task than aMCI patients and controls (32.4% versus 23.5%; p < 0.01 and 32.4% versus 22.2%; p < 0.05, respectively), but there were no differences among the groups in anticipation rate or the percentage of express saccades. Additionally, error rates on the spatial decision task were inversely correlated with performance on visual memory tests (immediate and delayed recall on the DMS- 48: r=-0.44, p=0.0019 and r=-0.43, p=0.0020, respectively), semantic fluency (r=-0.44, p=0.0016), and global cognition (MMSE: r=-0.44, p=0.0019). Performance on the spatial decision task was not correlated with anti-saccades, processing speed, or attentional performance. Conclusions: Patients with mild AD made more errors on a spatial decision task than aMCI patients and controls. We hypothesize that impaired visuospatial judgment may explain these results and distinguish aMCI patients from mild AD patients.
Agnes Pirker-Kees, Peter Dal-Bianco, Reinhold Schmidt
Effects of Psychotropic Medication on Cognition, Caregiver Burden, and Neuropsychiatric Symptoms in Alzheimer’s Disease over 12 Months: Results from a Prospective Registry of Dementia in Austria (PRODEM)
Abstract: Behavioral and psychological symptoms of dementia are common in Alzheimer’s disease (AD) and associated with a more rapid decline in cognitive function. Psychotropic substances are frequently used in AD, but we lack conclusive evidence of their efficacy in this setting. SSRI and trazodone were reported to have positive effects on cognition. Based on the prospective registry of dementia in Austria (PRODEM), we investigated the effects of psychotropic substances on cognition, behavioral symptoms, and caregiver burden (CB) in patients with AD, followed up prospectively over a 12-month period. We used the Mini-Mental State Examination (MMSE), the Neuropsychiatric Inventory (NPI), and the Zarit caregiver burden interview. The study cohort consisted of 309 patients. Patients taking no psychotropic drugs (NO) or those undergoing consistent monotherapy with a psychotropic drug for 12 months were analyzed further (NO 101 patients, SSRI 22, trazodone 8, atypical neuroleptics or benzodiazepines (ANL/BZD) 18). Additionally, the subgroup of patients who started taking any of the substances during the study period were analyzed further to determine the effects before versus six months after the start of medication. MMSE, NPI, and CB at baseline and during follow-up did not differ between the groups. MMSE and CB declined over 12 months in the overall group (MMSE: 21.2 ±4 versus 19.7 ±5, p=0.001 and CB 20.3±12 versus 24.7 ±14.2, p=0.007), but no statistically significant changes were registered within groups over 12 months. When trazodone was started, only NPI improved significantly after 6 months (33.4±18 versus 18.9 ± 22.7, p<0.01). ANL/BZD or SSRI, when started, did not alter MMSE, NPI, or CB. SSRI had no beneficial effect on cognition. We conclude that trazodone might be helpful in the treatment of behavioral symptoms.
Paola Flores-Rodríguez, Charles R. Harrington, Claude M. Wischik, Vanessa Ibarra-Bracamontes, Natanael Zarco, Araceli Navarrete, Alejandra Martínez-Maldonado, Parménides Guadarrama-Ortíz, Ignacio Villanueva-Fierro, Miguel Angel Ontiveros-Torres, George Perry, Alejandra D. Alonso, Benjamin Floran-Garduño, José Segovia, José Luna-Muñoz (Handling Editor: Jesus Avila)
Phospho-Tau Protein Expression in the Cell Cycle of SH-SY5Y Neuroblastoma Cells: A Morphological Study
Abstract: It has been reported that the main function of tau protein is to stabilize microtubules and promote the movement of organelles through the axon in neurons. In Alzheimer's disease, tau protein is the major constituent of the paired helical filament, and it undergoes post-translational modifications including hyperphosphorylation and truncation. Whether other functions of tau protein are involved in Alzheimer’s disease is less clear. We used SH-SY5Y human neuroblastoma cells as an in vitro model to further study the functions of tau protein. We detected phosphorylated tau protein as small dense dots in the cell nucleus, which strongly colocalize with intranuclear speckle structures that were also labelled with an antibody to SC35, a protein involved in nuclear RNA splicing. We have shown further that tau protein, phosphorylated at the sites recognized by pT231, TG-3, and AD2 antibodies, is closely associated with cell division. Different functions may be characteristic of phosphorylation at specific sites. Our findings suggest that the presence of tau protein is involved in separation of sister chromatids in anaphase, and that tau protein also participates in maintaining the integrity of the DNA (pT231, prophase) and chromosomes during cell division (TG-3).
Zachary Hobel, A. Lisette Isenberg, Dhvani Raghupathy, Wendy Mack, Judy Pa for the Alzheimer’s Disease Neuroimaging Initiative and the Australian Imaging Biomarkers and Lifestyle flagship study of ageing (Handling Associate Editor: Liqin Zhao)
APOE ε4 Gene Dose and Sex Effects on Alzheimer’s Disease MRI Biomarkers in Older Adults with Mild Cognitive Impairment
Abstract: Background: APOE ε4 and sex have been linked to increased risk for conversion to Alzheimer’s disease (AD). However, the relationship between APOE ε4 gene dose, sex, and AD biomarkers remains understudied. Objective: To investigate the effect of APOE ε4 dose on AD biomarkers in a sample of older adults with mild cognitive impairment (MCI), and to examine whether APOE ε4 dose modifies AD risk differently in MCI women and men. Methods: We examined cross-sectional AD biomarkers for participants with MCI (n=930, 55-96 years old) from three large aging cohorts. Region of interest MRI volumes, global cognition, and episodic memory were analyzed by number of APOE ε4 alleles and stratified by sex. Results: Across all participants, number of APOE ε4 alleles was associated with smaller hippocampal and amygdala volumes and poorer cognition. When stratified by sex, women showed an APOE ε4 dose effect for bilateral hippocampal and left amygdala volumes and cognition. In contrast, men showed an APOE ε4 dose effect for hippocampal volumes with a trend in amygdala, but cognition did not differ between men with 1 and 2 APOE ε4 alleles. Women with 2 APOE ε4 alleles had poorer memory between 65-69 and poorer global cognition between 70-74 compared to men with 2 APOE ε4 alleles. Conclusion: APOE ε4 confers a dose effect on AD biomarkers in patients with MCI, and the number of APOE ε4 alleles has a greater detrimental impact in women than men, which may be specific to a critical time window.
Valory N. Pavlik, Wenyaw Chan, Eveleen Darby
Cohort Effects in Progression Rate on Cognitive and Functional Measures in an Alzheimer’s Disease Clinical Cohort
Abstract: Background: Accurate prediction of Alzheimer’s disease (AD) cognitive and functional outcomes in clinical research requires consistent underlying rates of change over time. Objective: To examine cohort effects in AD progression rate over five years of follow-up using a clinical database of probable AD patients. Methods: Baseline characteristics of three cohorts enrolled from 1995-1999, 2000-2004, and 2005-2009 were compared using ANOVA and chi-square tests. Differences in 5-year decline on the Mini-Mental State Examination (MMSE), Alzheimer’s Disease Assessment Scale-Cognitive Subscale (ADAS-Cog) and Clinical Dementia Rating Scale Sum of Boxes (CDR-SB), the Lawton and Brody Physical Self-maintenance Scale (PSMS), and Activities of Daily Living Scale (ADL) were assessed using longitudinal mixed effects regression, adjusting for age, sex, education, and other relevant clinical characteristics. Results: Cohorts 1 (n=287), 2 (n=257), and 3 (n=374) did not differ on age, race, APOE genotype, or cognitive and functional measures. Educational attainment increased over time (13.4, 14.1, and 14.5 years, respectively, p<0.001). Anti-dementia drug use at baseline was less common in Cohort 1 (32.2% versus 65.0%, and 66.8%, p<0.001). The rate of decline in MMSE and CDR-SB did not differ across cohorts. ADAS-Cog scores for Cohort 2 declined more slowly than Cohort 3 (Btime x cohort2=-0.91±0.35, p=0.009), whereas Cohort 1 did not differ from cohort 3 (reference). Cohorts 1 and 2 differed from Cohort 3 in progression rate on the PSMS, but not the IADL. Conclusions: There were no consistent temporal trends in progression rates over time. Longitudinal data over 15-20 years may be confidently pooled for outcomes analysis, but unexplained variability in rate of decline on some measures may occur.
Hui Li*, Xiao-Bing Luo*, Yan Xu, Xiao-Yu Hou *These authors contributed equally to this work.
A Brief Ischemic Postconditioning Protects Against Amyloid-β Peptide Neurotoxicity by Downregulating MLK3-MKK3/6-P38MAPK Signal in Rat Hippocampus
Abstract: Background: Oligomeric amyloid-β peptide (Aβ) is associated with dysfunctional neuronal networks and neuronal loss in the development of Alzheimer’s disease (AD). Ischemic postconditioning protects against post-ischemic excitotoxicity, oxidative stress, and inflammatory process that have also been implicated in the pathogenesis of AD. Evaluating the roles of ischemic postconditioning in oligomeric Aβ-induced neurotoxicity and underlying signal events may provide potential strategy for medical therapy in AD. Objectives: The aim of the present study was to explore whether and how a brief ischemic postconditioning protects against Aβ neurotoxicity in rat hippocampus. Methods: Oligomeric Aβ25-35 (20 nmol/rat) or Aβ1-42 (5 nmol/rat) was infused by intracerebroventricular injection in adult male Sprague-Dawley rats. Ischemic postconditioning, a brief episode of global brain ischemia (3 min), was conducted at 1, 3, or 7 days after Aβ treatment, respectively. Results: A brief ischemic postconditioning reduced neuronal loss and inhibited the activation of MLK3, MKK3/6, and P38MAPKs in rat hippocampal CA1 and CA3 subfields after Aβ oligomer infusion. An N-methyl-D-aspartate (NMDA) receptor antagonist amantadine, but not non-NMDA receptor antagonist CNQX, reversed the MLK3-MKK3/6-P38MAPK signal events and beneficial effect of ischemic postconditioning on neuronal survival. Such reversion was also realized by NVP-AAM077, a GluN2A-subunit-selective NMDA receptor antagonist. Moreover, posttreatment with low doses of NMDA (5 nmol - 40 nmol/rat) suppressed the Aβ-induced P38MAPK signaling and imitated the neuroprotection of ischemic postconditioning against Aβ neurotoxicity. Conclusions: Ischemic postconditioning provides neuroprotection against Aβ neurotoxicity by moderate upregulation of NMDA receptor signaling, especially GluN2A-containing NMDA receptor pathway, and thereafter downregulation of MLK3-MKK3/6-P38MAPK signal events.
Alica Rogojin, Diana J. Gorbet, Kara M. Hawkins, Lauren E. Sergio
Cognitive-Motor Integration Performance Is Affected by Sex, APOE Status, and Family History of Dementia
Abstract: Background: Cognitive-motor integration (CMI) involves concurrent thought and action which requires the interaction of large brain networks. Given that early-stage dementia involves neural network dysfunction, deficits in CMI may prove useful for early dementia detection. Objective: Our research objective was to investigate sex-related differences in the ability to integrate rules into action. Methods: Based on family medical history, we recruited male and female participants both with and without dementia risk factors. Participants did not demonstrate cognitive impairment at the time of testing. Participants were tested on four increasingly dissociated visuomotor tasks (eye and hand movements were made in different spatial planes and/or visual feedback was reversed). Results: We observed significantly greater hand movement endpoint error scores and corrective path lengths in at-risk females compared to at-risk males in the most complex CMI condition (plane-change + feedback reversal). Multiple regression analyses revealed both sex and family history as significant predictors of worse performance in a CMI condition requiring visual feedback reversal. Further, the regression analyses provided preliminary evidence that having an APOE ε4 allele was a significant predictor of poorer CMI performance in the two plane-change CMI conditions. Conclusion: These data suggest that underlying brain networks controlling simultaneous thought and action may differ between the sexes in ways that may be clinically relevant in dementia progression. Preliminary data also suggest an important connection between APOE variant and CMI performance in individuals at risk of developing dementia.
Lucy E. Stirland, Tom C. Russ, Craig W. Ritchie, Graciela Muniz-Terrera, EPAD Consortium (Handling Associate Editor: Maria Vassilaki)
Associations Between Multimorbidity and Cerebrospinal Fluid Amyloid: A Cross-Sectional Analysis of the European Prevention of Alzheimer's Dementia (EPAD) V500.0 Cohort
Abstract: Background: Multimorbidity (the co-occurrence of multiple chronic conditions) is increasingly common, especially among people with dementia. Few neuroimaging studies have explored amyloid biomarkers in people with multimorbidity. Objective: We aimed to conduct the first study of the association between multimorbidity and cerebrospinal fluid amyloid-β42 (CSF Aβ). Method: The European Prevention of Alzheimer's Dementia (EPAD) Longitudinal Cohort Study V500.0 dataset includes volunteers aged ≥50 years from 12 sites. Participants undergo detailed phenotyping, including CSF measures and a self-reported medical history. Using logistic and linear regression analyses, we explored the association between multimorbidity and continuous chronic condition count with CSF Aβ positivity (Aβ42 <1000pg/ml) and continuous CSF Aβ concentration. All models were adjusted for age, sex, APOE status, education, and family history of dementia. Results: Among 447 eligible participants without dementia, the mean (SD) age was 66.6 (6.6) years, 234 (52.3%) were women, and 157 (35.1%) were amyloid positive. With chronic conditions regarded as pseudo-continuous, each additional condition carried a decreased likelihood of amyloid positivity (OR=0.82, 95%CI: 0.68-0.97; p=0.026). With CSF Aβ as a continuous variable, each additional condition was associated with an increase of 54.2 pg/ml (95%CI: 9.9-98.5, p=0.017). Having ≥2 conditions was inversely associated with amyloid positivity (OR 0.59, 95%CI: 0.37-0.95, p=0.030) compared to one or none. Conclusion: Our findings suggest that the established association between multimorbidity and dementia may be due to a pathway other than amyloid. However, this cross-sectional study does not allow us to make causal inferences. Longitudinal work is required to confirm the inverse association found.