Francesca Fagiani*, Cristina Lanni*, Marco Racchi, Alessia Pascale, Stefano Govoni *These authors contributed equally to this work.
Amyloid-β and Synaptic Vesicle Dynamics: A Cacophonic Orchestra
Abstract: It is now more than two decades since amyloid-β (Aβ), the proteolytic product of the amyloid-β protein precursor (AβPP), was first demonstrated to be a normal and soluble product of neuronal metabolism. To date, despite a growing body of evidence suggests its regulatory role on synaptic function, the exact cellular and molecular pathways involved in Aβ-driven synaptic effects remain elusive. This review provides an overview of the mounting evidence showing Aβ-mediated effects on presynaptic functions and neurotransmitter release from axon terminals, focusing on its interaction with synaptic vesicle cycle. Indeed, Aβ peptides have been found to interact with key presynaptic scaffold proteins and kinases affecting the consequential steps of the synaptic vesicle dynamics (e.g., synaptic vesicles exocytosis, endocytosis, and trafficking). Defects in the fine-tuning of synaptic vesicle cycle by Aβ and deregulation of key molecules and kinases, which orchestrate synaptic vesicle availability, may alter synaptic homeostasis, possibly contributing to synaptic loss and cognitive decline. Elucidating the presynaptic mechanisms by which Aβ regulate synaptic transmission is fundamental for a deeper comprehension of the biology of presynaptic terminals as well as of Aβ-driven early synaptic defects occurring in prodromal stage of AD. Moreover, a better understating of Aβ involvement in cellular signal pathways may allow to set up more effective therapeutic interventions by detecting relevant molecular mechanisms, whose imbalance might ultimately lead to synaptic impairment in AD.
Topi Rönkkö, Hilkka Timonen
Overview of Sources and Characteristics of Nanoparticles in Urban Traffic-Influenced Areas
Abstract: Atmospheric nanoparticles can be formed either via nucleation in atmosphere or be directly emitted to the atmosphere. In urban areas, several combustion sources (engines, biomass burning, power generation plants) are directly emitting nanoparticles to the atmosphere and, in addition, the gaseous emissions from the same sources can participate to atmospheric nanoparticle formation. This article focuses on the sources and formation of nanoparticles in traffic-influenced environments and reviews current knowledge on composition and characteristics of these nanoparticles. In general, elevated number concentrations of nanoparticles are very typically observed in traffic-influenced environments. Traffic related nanoparticles can originate from combustion process or from non-exhaust related sources such as brake wear. Particles originating from combustion process can be divided to three different sources; 1) primary nanoparticles formed in high temperature, 2) delayed primary particles formed as gaseous compounds nucleate during the cooling and dilution process and 3) secondary nanoparticles formed from gaseous precursors via the atmospheric photochemistry. The nanoparticles observed in roadside environment are a complex mixture of particles from several sources affected by atmospheric processing, local co-pollutants and meteorology.
Johanna Thunell, Patricia Ferido, Julie Zissimopoulos (Handling Associate Editor: Igor Akushevich)
Measuring Alzheimer’s Disease and Other Dementias in Diverse Populations Using Medicare Claims Data
Abstract: We examined how methods used for identifying dementia in administrative claims affected dementia incidence across racial/ethnic populations using a 100% sample of Medicare beneficiaries (n=23,793,452). We found levels differed by method from 3.1% annual incidence to 3.6% in 2014. Dementia incidence declined 2007 to 2014, but choice of method differentially impacted levels and trends by race/ethnicity. Methods using codes for dementia diagnosis and drugs to treat symptoms identified proportionally more Hispanics and Asians with dementia than other race/ethnicities, while codes for dementia diagnosis, drugs, and symptoms identified proportionally more whites and American Indians/Alaska Natives with dementia than other race/ethnicities.
Stuart G. Snowden, Amera A. Ebshiana, Abdul Hye, Olga Pletnikova, Richard O’Brien, An Yang, Juan Troncoso, Cristina Legido-Quigley*, Madhav Thambisetty* *Shared senior authorship.
Neurotransmitter Imbalance in the Brain and Alzheimer’s Disease Pathology
Abstract: Background: Cholinesterase inhibitors represent three of the four treatments for Alzheimer’s disease (AD), and target the pathological reduction of acetylcholine levels. Here we aimed to study the role of other neurotransmitter pathways in AD pathology. Objective: This study aimed to determine associations between AD pathology at both symptomatic and asymptomatic stages of disease progression, and the metabolism of a range of non-cholinergic neurotransmitters. Methods: Tissue samples were obtained from three groups, controls, AD, and ‘asymptomatic AD’ (ASYMAD), i.e., cognitively normal individuals that had significant AD neuropathology. Three brain areas were studied, the middle frontal gyrus (MFG), the inferior temporal gyrus (ITG), and the cerebellum. Results: 12 of 15 metabolites involved in neurotransmitter metabolism were shown to be associated with AD pathology. Decreases in dopamine were most pronounced in the MFG with lower levels seen in the ASYMAD group compared to control (FC=0.78, p=2.9×10-2). In the ITG significant changes were seen in GABAergic and serotonin metabolism between control and AD patients; however, these changes were not seen between control and ASYMAD individuals. Conclusion: These results indicate that dopamine could be depleted in brains with AD pathology but intact cognition, while an imbalance of several neurotransmitters is evident in the brains of AD patients.
Kumar B. Rajan, Elizabeth A. McAninch, Robert S. Wilson, Jennifer Weuve, Lisa L. Barnes, Denis A. Evans
Race, APOE ε4, and Long-Term Cognitive Trajectories in a Biracial Population Sample
Abstract: Background: The association of the APOE ε4 allele with incident Alzheimer’s dementia is higher among European Americans (EAs) than African Americans (AAs), but similar for the rate of cognitive decline. Objective: To examine the racial differences in the association of the APOE ε4 allele with incident Alzheimer’s dementia and cognitive decline. Methods: Using a population-based sample of 5,117 older adults (66% AAs and 63% females), we identified cognitive trajectory groups from a latent class mixed model and examined the association of the APOE ε4 allele with these groups. Results: The frequency of the APOE ε4 allele was higher among AAs than EAs (37% versus 26%). Four cognitive trajectories were identified: slow, mild, moderate, and rapid. Overall, AAs had a lower baseline global cognition than EAs, and a higher proportion had rapid (7% versus 5%) and moderate (20% versus 15%) decline, but similar mild (44% versus 46%), and lesser slow (29% versus 34%) decline compared to EAs. Additionally, 25% of AAs (13% of EAs) with mild and 5% (< 1% of EAs) with slow decline were diagnosed with incident Alzheimer’s dementia. The APOE ε4 allele was associated with higher odds of rapid and moderate decline compared to slow decline among AAs and EAs, but not with mild decline. Conclusions: AAs had lower cognitive levels and were more likely to meet the cognitive threshold for Alzheimer’s dementia among mild and slow decliners, explaining the attenuated association of the ε4 allele with incident Alzheimer’s dementia among AAs.
Glykeria Tsentidou, Despina Moraitou, Magda Tsolaki
Cognition in Vascular Aging and Mild Cognitive Impairment
Abstract: Cardiovascular health declines with age, due to vascular risk factors, and this leads to an increasing risk of cognitive decline. Mild cognitive impairment (MCI) is defined as the negative cognitive changes beyond what is expected in normal aging. The purpose of the study was to compare older adults with vascular risk factors (VRF), MCI patients, and healthy controls (HC) in main dimensions of cognitive control. The sample comprised a total of 109 adults, aged 50 to 85 (M = 66.09, S.D. = 9.02). They were divided into three groups: 1) older adults with VRF, 2) MCI patients, and 3) healthy controls (HC). VRF and MCI did not differ significantly in age, educational level, or gender as was the case with HC. The tests used mainly examine inhibition, cognitive flexibility, and working memory processing. Results showed that the VRF group had more Set Loss Errors in drawing designs indicating deficits in establishing cognitive set and in cognitive shifting. MCI patients displayed lower performance in processing. Hence, different types of specific impairments emerge in vascular aging and MCI, and this may imply that discrete underlying pathologies may play a role in the development of somewhat different profiles of cognitive decline.
Ilona Har-Paz, Nicole Roisman, Daniel M. Michaelson, Anan Moran (Handling Associate Editor: Ashley Bush)
Extra-Hippocampal Learning Deficits in Young Apolipoprotein E4 Mice and Their Synaptic Underpinning
Abstract: The E4 allele of apolipoprotein (apoE4) is the primary genetic risk factor for late onset Alzheimer’s disease (AD), yet the exact manner in which apoE4 leads to the development of AD is undetermined. Human and animal studies report that apoE4-related memory deficits appear earlier than the AD clinical manifestation, thus suggesting the existence of early, pre-pathological, apoE4 impairments that may later lead to AD onset. While current research regards the hippocampus as the initial and primary effected locus by apoE4, we presently investigate the possibility that apoE4 innately impairs any brain area that requires synaptic plasticity. To test this hypothesis, we trained young (3-4-month-old) target-replacement apoE3 and apoE4 mice in conditioned taste aversion (CTA) acquisition and extinction learnings—hippocampus-independent learnings that are easily performed at a young age. Synaptic vesicular markers analysis was conducted in the gustatory cortex (GC), basolateral amygdala (BLA), medial prefrontal cortex (mPFC), and hippocampal CA3 to reveal underlying apoE4-related impairments. We have found that young apoE4 mice are severely impaired in CTA acquisition and extinction learning. CTA acquisition impairment was correlated with reduced vGat and vGlut levels in the BLA and GC, but not in CA3. CTA extinction was correlated with lower marker levels of synaptophysin and vGlut in the mPFC, a central region in CTA extinction. Our results support apoE4-related early-life plasticity impairments that precede the AD clinical manifestations and affect any brain area that depends on extensive plasticity; early impairments that may promote the development of AD pathologies later in life.
RuiQi Pang, XiaoFan Wang, FeiFei Pei, Weizhe Zhang, Jiaming Shen, Xiaoqun Gao, Cheng Chang
Regular Exercise Enhances Cognitive Function and Intracephalic GLUT Expression in Alzheimer’s Disease Model Mice
Abstract: Brain energy metabolic impairment is one of the main features of Alzheimer's disease (AD) and is considered an underlying factor involved in cognitive impairment. Therefore, brain energy metabolism may represent a new therapeutic target for AD medical interventions. Among nutrients providing energy, glucose, the primary energy source, cannot cross the blood-brain barrier freely without specific glucose transporters (GLUTs), which are essential for the maintenance of cerebral energy metabolism homeostasis. Several converging lines of evidence suggest that GLUT1 deficiency in mice leads to synapse reduction and dysregulation coupled with mitochondrial morphological changes. In this study, the results revealed that regular exercise (RE) decreased the expression of amyloid-β and phosphorylated tau by western blot, and enhanced the spatial learning and exploration ability of AD model mice as assessed by Morris water maze test. Mitochondrial cristae and edges were clear and intact, ATP production in the brain raised, the number of synapses increased, and GLUT1 and GLUT3 expression levels improved in the central nervous system (CNS) in AD model mice after RE. Changes in GLUT1 and GLUT3 expression at the protein level after RE are an important part of energy metabolic adaptation in AD model mice. Learning and memory improvement are highly associated with mitochondrial integrity and sufficient synapses in the CNS. This research suggests that increased brain energy metabolism attributed to RE exhibits promising therapeutic potential for AD.
Qin Cao*, Tian Meng*, Jianhui Man, Dong Peng, Hongxia Chen, Qi Xiang, ZhijianSu, Qihao Zhang, Yadong Huang *These authors contributed equally to this work.
aFGF Promotes Neurite Growth by Regulating GSK3β-CRMP2 Signaling Pathway in Cortical Neurons Damaged by Amyloid-β
Abstract: Glycogen synthase kinase 3β (GSK3β) is a key component of pathogenesis in Alzheimer's disease, and its inhibitors can restore cognitive function as therapeutic interventions in neurodegenerative diseases. The previous studies showed that acidic fibroblast growth factor (aFGF) could increase the phosphorylation of GSK3β through the PI3K/Akt signaling pathway. We found that aFGF14–154 markedly increased the average length of neurites in neurons damaged by amyloid-β (Aβ), and this promoting effect was blocked by GSK3β inhibitor. It is still unknown which downstream substrates of GSK3β are related to the neurite growth facilitated by aFGF14-154. The downstream substrates interacting with GSK3β were screened by co-immunoprecipitation and LTQ-Orbitrap proteomics technology in our study. Collapsin response mediator protein 2 (CRMP2) has been identified as a protein interacting with GSK3β, which is involved in the axon formation and neuron regeneration by regulating microtubule reorganization. aFGF14-154 increased the phosphorylation of GSK3β (Ser9) to inhibit its activity, then was followed by a low phosphorylation level of CRMP2 (Thr514), which led to the neurite growth. The knockdown of CRMP2 blocked the rescue of aFGF14–154 with broken neurites and shrunken cell bodies in neurons with Aβ injury. These results highlight the important role of CRMP2 and its phosphorylation through GSK3β in the effect that aFGF14-154 promoted the growth of neurite damaged by Aβ.
Laura Serra, Laura Petrosini, Andrea Salaris, Lorenzo Pica, Michela Bruschini, Carlotta Di Domenico, Carlo Caltagirone, Camillo Marra, Marco Bozzali
Testing for the Myth of Cognitive Reserve: Are the Static and Dynamic Cognitive Reserve Indexes a Representation of Different Reserve Warehouses?
Abstract: Background: Cognitive reserve (CR) explains the individual resilience to neurodegeneration. Years of formal education express the static measure of reserve (sCR). A dynamic aspect of CR (dCR) has been recently proposed. Objective: The aim of the study was to compare sCR and dCR indexes, respectively, to detect brain abnormalities in Alzheimer’s disease (AD) patients. Methods: 117 individuals [39 AD, 40 amnestic mild cognitive impairment (aMCI), 38 healthy subjects (HS)] underwent neuropsychological evaluation and a 3T-MRI. T1-weighted volumes were used for manual segmentation of the hippocampus and of the parahippocampal cortices. Years of formal education were used as an index of sCR. Partial Least Square analysis was used to decompose the variance of individual MMSE scores, considered as a dCR index. In aMCI and AD patients, the brain abnormalities have been assessed comparing individuals with high and low levels of sCR and dCR in turn. Moreover, we investigated the effect of the different CR indexes in mediating the relationship between changes in brain volumes and memory performances. Results: sCR and dCR indexes classified differently individuals having high or low levels of CR. Smaller hippocampal and parahippocampal volumes in high dCR patients were found. The sCR and dCR indexes mediated significantly the relationship between brain abnormalities and memory in patients. Conclusions: CR mediated the relationship between brain and memory dysfunctions. We hypothesized that sCR and dCR indexes are a representation of different warehouses of reserve not operating in parallel but forming a complex system, in which crystalized cognitive abilities and actual cognitive efficiency interact with brain atrophy impacting on memory.
Olli Jääskeläinen*, Eino Solje*, Anette Hall, Kasper Katisko, Ville Korhonen, Mika Tiainen, Antti J. Kangas, Seppo Helisalmi, Maria Pikkarainen, Anne Koivisto, Päivi Hartikainen, Mikko Hiltunen, Mika Ala-Korpela, Hilkka Soininen, Pasi Soininen, Annakaisa Haapasalo, Anne M. Remes, Sanna-Kaisa Herukka *These authors contributed equally to this work.
Low Serum High-Density Lipoprotein Cholesterol Levels Associate with the C9orf72 Repeat Expansion in Frontotemporal Lobar Degeneration Patients
Abstract: Decreased levels of serum high-density lipoprotein (HDL) cholesterol have previously been linked to systemic inflammation and neurodegenerative diseases, such as Alzheimer’s disease. Here, we aimed to analyze the lipoprotein profile and inflammatory indicators, the high-sensitivity C-reactive peptide (hs-CRP) and glycoprotein acetyls (GlycA), in sporadic and C9orf72 repeat expansion-associated frontotemporal lobar degeneration (FTLD) patients. The C9orf72 hexanucleotide repeat expansion is the most frequent genetic etiology underlying FTLD. The concentrations of different lipid measures in the sera of 67 FTLD patients (15 C9orf72 repeat expansion carriers), including GlycA, were analyzed by nuclear magnetic resonance spectroscopy. To verify the state of systemic inflammation, hs-CRP was also quantified from patient sera. We found that the total serum HDL concentration was decreased in C9orf72 repeat expansion carriers when compared to non-carriers. Moreover, decreased concentrations of HDL particles of different sizes and subclass were consistently observed. No differences were detected in the very low- and low-density lipoprotein subclasses between the C9orf72 repeat expansion carriers and non-carriers. Furthermore, hs-CRP and GlycA levels did not differ between the C9orf72 repeat expansion carriers and non-carriers. In conclusion, the HDL-related changes were linked with C9orf72 repeat expansion associated FTLD but were not seen to associate with systemic inflammation. The underlying reason for the HDL changes remains unclear.
Yiran Wang, Ying Wang, Veni Bharti, Hong Zhou, Vanessa Hoi, Hua Tan, Zijian Wu, Pandian Nagakannan, Eftekhar Eftekharpour, Jun-Feng Wang (Handling Associate Editor: Wolff Kirsch)
Upregulation of Thioredoxin-Interacting Protein in Brain of Amyloid-β Protein Precursor/Presenilin 1 Transgenic Mice and Amyloid-β Treated Neuronal Cells
Abstract: Oxidative stress has been hypothesized to play a role in the pathophysiology of Alzheimer’s disease (AD). Previously, we found that total nitrosylated protein levels were increased in the brain of amyloid-β protein precursor (AβPP) and presenilin 1 (PS1) double transgenic mice, an animal model for AD, suggesting that cysteine oxidative protein modification may contribute to this disease. Thioredoxin (Trx) is a major oxidoreductase that can reverse cysteine oxidative modifications such as sulfenylation and nitrosylation, and inhibit oxidative stress. Thioredoxin-interacting protein (Txnip) is an endogenous Trx inhibitor. To understand the involvement of Trx and Txnip in AD development, we investigated Trx and Txnip in the brain of AβPP/PS1 mice. Using immunoblotting analysis, we found that although Trx protein levels were not changed, Txnip protein levels were significantly increased in hippocampus and frontal cortex of 9- and 12-month-old AβPP/PS1 mice when compared to wild-type mice. Txnip protein levels were also increased by amyloid-β treatment in primary cultured mouse cerebral cortical neurons and HT22 mouse hippocampal cells. Using biotin switch and dimedone conjugation methods, we found that amyloid-β treatment increased protein nitrosylation and sulfenylation in HT22 cells. We also found that downregulation of Txnip, using CRISPR/Cas9 method in HT22 cells, attenuated amyloid-β-induced protein nitrosylation and sulfenylation. Our findings suggest that amyloid-β may increase Txnip levels, subsequently inhibiting Trx reducing capability and enhancing protein cysteine oxidative modification. Our findings also indicate that Txnip may be a potential target for the treatment of AD.
Ana Pozueta, Carmen Lage, María García Martínez, Martha Kazimierczak, María Bravo, Sara López-García, Javier Riancho, Andrea González-Suarez, José Luis Vázquez-Higuera, María de Arcocha-Torres, Ignacio Banzo, Julio Jimenez Bonilla, José Berciano, Eloy Rodríguez-Rodríguez, Pascual Sánchez-Juan
A Brief Drawing Task for the Differential Diagnosis of Semantic Dementia
Abstract: Background: Semantic dementia (SD) is a subtype of frontotemporal lobe degeneration characterized by semantic loss, with other cognitive functions initially preserved. SD requires differential diagnosis with Alzheimer’s disease (AD) and behavioral variant frontotemporal dementia (bvFTD). Semantic knowledge can be evaluated through different tests; however, most of them depend on language. Objective: We describe the development of a brief drawing task that may the helpful for the differential diagnosis of SD. Methods: Seventy-two patients, including 32 AD, 19 bvFTD, and 21 SD were asked to draw 12 items with different age of acquisition and familiarity, belonging to four different semantic categories. We employed the drawings of healthy volunteers to build a scoring scheme. Results: Turtle, strawberry, train, and envelope were the items of each category that best discriminated between groups and were selected for the Brief drawing task. The discriminatory power of the Brief drawing task between SD versus AD and bvFTD patients, estimated through the area under the curve was 0.84 (95% CI=0.72-0.96, p=0.000007). In a logistic model, the Brief drawing task (p=0.003) and VOSP “number location” subtest (p=0.016) were significant predictors of the diagnosis of SD versus AD and bvFTD after adjustment by the main covariates. The Brief drawing task provided clinically useful qualitative information. SD drawings were characterized by loss of the distinctive features, intrusions, tendency to prototype, and answers like "I don't know what this is". Conclusion: The Brief drawing task appears to reveal deficits in semantic knowledge among patients with SD that may assist in the differential diagnosis with other neurodegenerative diseases.
Marlena Zyśk, Fredrik Clausen, Ximena Aguilar, Dag Sehlin, Stina Syvänen, Anna Erlandsson
Long-Term Effects of Traumatic Brain Injury in a Mouse Model of Alzheimer’s Disease
Abstract: Alzheimer’s disease (AD) is the leading cause of dementia worldwide, affecting over 10% of the elderly population. Epidemiological evidence indicates that traumatic brain injury (TBI) is an important risk factor for developing AD later in life. However, which injury-induced processes that contribute to the disease onset remains unclear. The aim with the present study was to identify cellular processes that could link TBI to AD development, by investigating the chronic impact of two different injury models, controlled cortical impact (CCI) and midline fluid percussion injury (mFPI). The trauma was induced in 3-month-old tg-ArcSwe mice, carrying the Arctic mutation along with the Swedish mutation, and the influence of TBI on AD progression was analyzed at 12- and 24-weeks post-injury. The long-term effect of the TBI on memory deficiency, amyloid-β (Aβ) pathology, neurodegeneration and inflammation was investigated by Morris water maze, PET imaging, immunohistochemistry, and biochemical analyses. Morris water maze analysis demonstrated that mice subjected to CCI or mFPI performed significantly worse than uninjured tg-ArcSwe mice, especially at the later time point. Moreover, the injured mice showed a late upregulation of reactive gliosis, which concurred with a more pronounced Aβ pathology, compared to uninjured AD mice. Our results suggest that the delayed glial activation following TBI may be an important link between the two diseases. However, further studies in both experimental models and human TBI patients will be required to fully elucidate the reasons why TBI increases the risk of neurodegeneration.
Angelina R. Sutin, Yannick Stephan, Antonio Terracciano (Handling Associate Editor: Shana Stites)
Self-Reported Personality Traits and Informant-Rated Cognition: A 10-Year Prospective Study
Abstract: Personality traits, such as higher Neuroticism and lower Conscientiousness, are associated with risk of Alzheimer’s disease and other dementias. A diagnosis of dementia relies, in part, on informant ratings of the individual’s cognitive status. Here we examine whether self-reported personality traits are associated with four measures of informant-rated cognition up to a decade later. Participants from the Health and Retirement Study (N=2,536) completed a five-factor model measure of personality in 2006 or 2008. Informants completed the 2016 Harmonized Cognitive Assessment Protocol (HCAP), which included ratings of the participant’s current cognitive functioning and change in cognitive function over the last decade assessed with the IQCODE, Blessed, 1066, and CSID. Controlling for characteristics of the participant, informant, and their relationship, higher Neuroticism and lower Conscientiousness were associated consistently with worse informant-rated cognition. The association between Openness and better informant-rated cognition was due primarily to higher baseline cognitive function. Extraversion and Agreeableness were associated with better informant-rated cognition only among participants who were cognitively intact at follow-up. The present research suggests that knowledgeable informants are able to detect cognitive deficits associated with personality.
Ping-Song Chou, Meng-Ni Wu, Chen-Cheng Yang, Cheng-Ting Shen, Yuan-Han Yang
Effect of Advanced Glycation End Products on the Progression of Alzheimer’s Disease
Abstract: Background: Shared links between type 2 diabetes mellitus (T2DM) and Alzheimer’s disease (AD) have been well-known. A high concentration of advanced glycation end products (AGEs) has been reported to contribute to impaired mobility in patients with AD, but there is limited understanding regarding the longitudinal impact of AGEs on cognitive performance. Objective: This study aims to explore whether the concentrations of AGEs mediate the clinical progression of cognitive performance in patients with AD and T2DM. Methods: Twenty-five patients aged 79.0 ± 5.8 years who were diagnosed with probable AD with a Clinical Dementia Rating (CDR) of 0.5 or 1 and T2DM were enrolled in this study. When patients participated in the study, the concentration of plasma AGEs was tested. A series of neuropsychological tests, namely the Mini-Mental Status Examination (MMSE), Cognitive Assessment Screening Instrument (CASI), and CDR, were performed annually during follow-up. The association between the concentration of AGEs and changes in overall cognition and cognition related daily living performance was analyzed. Results: After the mean 48.6 ± 2.1 months of follow-up, AGEs were found to be significantly associated with a change in CDR. A total of 12 (48%) patients experienced a decline in CDR; they had a significantly higher concentration of AGEs than did those whose CDR did not deteriorate (100.5 ± 14.2 versus 81.5 ± 17.7; p = 0.007). This difference in CDR remained significant after adjustment for age, sex, education level, and apolipoprotein E4 status (adjusted p = 0.020). Conclusion: In conclusion, this study indicates that a high concentration of AGEs may be a predictor of a long-term decline in cognition related daily living performance in patients with AD and T2DM.
Qian Wang, Hailun Jiang, Linlin Wang, Hong Yi, Zhuorong Li, Rui Liu
Vitegnoside Mitigates Neuronal Injury, Mitochondrial Apoptosis, and Inflammation in an Alzheimer’s Disease Cell Model via the p38 MAPK/JNK Pathway
Abstract: Alzheimer's disease (AD) is a chronic neurodegenerative disorder characterized by progressive cognitive impairments. Vitegnoside is a flavonoid present in the medicinal plant Vitex negundo, widely used as a folk medicine in several Asian countries including China. It possesses several biological activities, including axon outgrowth, but no evidence is available on its effect on AD. Since no effective treatment is available to cure AD, the effect of vitegnoside on this disease was investigated. The human neuroblastoma SH-SY5Y cell line carrying the Swedish mutation that induces AβPP overexpression was used as an in vitro AD cell model. AβPP overexpression does not induce toxicity per se unless triggered by copper. Vitegnoside promoted neuroprotection through the improvement of cell viability, maintenance of cytomembrane integrity and nuclear homogeneity in these cells, but these effects were not observed in the copper-treated SH-SY5Y cells without AβPP overexpression used as the wild-type control, indicating that vitegnoside exerted neuroprotection under copper-triggered Aβ toxic conditions. Vitegnoside failed to decrease AβPP expression, Aβ40/42 levels, and oxidative stress due to copper-induced Aβ toxicity. However, its administration protected the mitochondrial function and restored the imbalance between pro-apoptotic and anti-apoptotic proteins. Additionally, vitegnoside inactivated p38 MAPK/MK2, JNK/c-Jun, and downstream NF-κB inflammatory transductions. Furthermore, the inactivation of p38 MAPK/JNK signaling contributed to vitegnoside-mediated neuroprotection resulting from pharmacological inhibition of p38 MAPK/JNK and in silico interaction prediction. Our study revealed the neuroprotective effect of vitegnoside and its potential mechanisms against copper-induced Aβ neurotoxicity. These findings highlighted the potential therapeutic effect of vitegnoside against AD progression.
Sini Toppala, Laura L. Ekblad, Jyrki Lötjönen, Semi Helin, Saija Hurme, Jarkko Johansson, Antti Jula, Mira Karrasch, Juha Koikkalainen, Hanna Laine, Riitta Parkkola, Matti Viitanen, Juha O. Rinne (Handling Associate Editor: Katherine Bangen)
Midlife Insulin Resistance as a Predictor for Late-Life Cognitive Function and Cerebrovascular Lesions
Abstract: Background: Type 2 diabetes (T2DM) increases the risk for Alzheimer’s disease (AD) but not for AD neuropathology. The association between T2DM and AD is assumed to be mediated through vascular mechanisms. However, insulin resistance (IR), the hallmark of T2DM, has been shown to associate with AD neuropathology and cognitive decline. Objective: To evaluate if midlife IR predicts late-life cognitive performance and cerebrovascular lesions (white matter hyperintensities and total vascular burden), and whether cerebrovascular lesions and brain amyloid load are associated with cognitive functioning. Methods: This exposure-to-control follow-up study examined 60 volunteers without dementia (mean age 70.9 years) with neurocognitive testing, brain 3T-MRI and amyloid-PET imaging. The volunteers were recruited from the Finnish Health 2000 survey (n=6062) to attend follow-up examinations in 2014–2016 according to their insulin sensitivity in 2000 and their APOE genotype. The exposure group (n=30) had IR in 2000 and the 30 controls had normal insulin sensitivity. There were 15 APOE ε4 carriers per group. Statistical analyses were performed with multivariable linear models. Results: At follow-up the IR+ group performed worse on executive functions (p=0.02) and processing speed (p=0.007) than the IR- group. The groups did not differ in cerebrovascular lesions. No associations were found between cerebrovascular lesions and neurocognitive test scores. Brain amyloid deposition associated with slower processing speed. Conclusion: Midlife IR predicted poorer executive functions and slower processing speed, but not cerebrovascular lesions. Brain amyloid deposition was associated with slower processing speed. The association between midlife IR and late-life cognition might not be mediated through cerebrovascular lesions measured here.
Hamizah Shahirah Hamezah, Lina Wati Durani, Daijiro Yanagisawa, Nor Faeizah Ibrahim, Wan Mohd Aizat, Suzana Makpol, Wan Zurinah Wan Ngah, Hanafi Ahmad Damanhuri, Ikuo Tooyama
Modulation of Proteome Profile in AβPP/PS1 Mice Hippocampus, Medial Prefrontal Cortex, and Striatum by Palm Oil Derived Tocotrienol-Rich Fraction
Abstract: Tocotrienol-rich fraction (TRF) is a mixture of vitamin E analogs derived from palm oil. We previously demonstrated that supplementation with TRF improved cognitive function and modulated amyloid pathology in AβPP/PS1 mice brains. The current study was designed to examine proteomic profiles underlying the therapeutic effect of TRF in the brain. Proteomic analyses were performed on samples of hippocampus, medial prefrontal cortex (mPFC), and striatum using liquid chromatography coupled to Q Exactive HF Orbitrap mass spectrometry. From these analyses, we profiled a total of 5,847 proteins of which 155 proteins were differentially expressed between AβPP/PS1 and wild-type mice. TRF supplementation of these mice altered the expression of 255 proteins in the hippocampus, mPFC, and striatum. TRF also negatively modulated the expression of amyloid beta A4 protein and receptor-type tyrosine-protein phosphatase alpha protein in the hippocampus. The expression of proteins in metabolic pathways, oxidative phosphorylation, and those involved in Alzheimer’s disease were altered in the brains of AβPP/PS1 mice that received TRF supplementation.
David Smeijer, M. Kamran Ikram, Saima Hilal
Enlarged Perivascular Spaces and Dementia: A Systematic Review
Abstract: Perivascular compartments surrounding the penetrating arteries in the brain are part of a physiologic system, which facilitates fluids exchange and clearance of solutes from the brain. The perivascular compartments become visible on MRI when enlarged and are commonly referred to as perivascular spaces (ePVS). Previous studies on the association between ePVS and dementia have been inconsistent due to varying methods of measuring ePVS. As a frame of reference for future MRI studies on ePVS, we systematically review the literature on ePVS as a marker of vascular brain injury related to dementia from population-based as well as hospital-based settings. We identified three longitudinal and ten cross-sectional studies involving 7,744 persons. Potential outcomes were all-cause dementia, Alzheimer’s disease, and vascular dementia. There was considerable heterogeneity in ePVS assessment: with studies using either visual inspection or segmentation, examining different brain locations and implementing different grading scales. Moreover, out of the total of 13 studies, all five studies on vascular dementia reported an association with presence of basal ganglia ePVS after adjustment for age, gender, and white matter hyperintensities. For seven studies on Alzheimer’s disease and all-cause dementia, the results were ambiguous. This review did not identify an independent association of ePVS with prevalent or incident dementia. Harmonized methods for ePVS assessment, tested across different populations, may benefit future MRI studies on ePVS and dementia.
Frank J. Castora, Barbara L. Conyers, Blake S. Gershon, Kimberly A. Kerns, Robert Campbell, Jr, Fatma Simsek-Duran
The T9861C Mutation in the mtDNA-Encoded Cytochrome C Oxidase Subunit III Gene Occurs in High Frequency but with Unequal Distribution in the Alzheimer’s Disease Brain
Abstract: Mitochondrial dysfunction is recognized as a critical component in the pathogenesis of neurodegenerative diseases, including Alzheimer’s disease (AD). Deficits in oxidative capacity and, specifically, cytochrome c oxidase (CO) activity have been reported in AD brains and platelets. We previously identified a point mutation at np 9861 in AD brain mitochondrial DNA (mtDNA) that alters amino acid 219 of subunit III of CO from phenylalanine to leucine. We rapidly screened and quantitated levels of T9861C in samples using mismatched PCR-RFLP and nucleotide extension assays. Six of 40 AD brains possessed the T9861C mutation (designated AD+) compared to zero of 40 age-matched control brains. The 15% frequency of T9861C in AD brain is 115-fold higher than the frequency (0.13%) reported in 9,986 human mtDNA samples queried in world-wide databases. T9861C is heteroplasmic, with mutant load varying from 11% to >95%. Detected initially in parietal cortex, T9861C is not localized to that region but is also found in temporal cortex and caudate but not in hippocampus. The mutant load is unequally distributed throughout these brain regions with the highest load occurring in the parietal or temporal cortex. CO activity normalized to citrate synthase (CS) is reduced an average of 48.5% in AD+ brains. CO/CS ratios amongst controls and the two AD populations (AD and AD+) were significantly different (p = 0.001). Post hoc differences were also significant between controls and AD+ (p = 0.001) and controls and AD (p = 0.019). There was no significant difference between AD and AD+ (p = 0.317).
Naoto Jingami, Kengo Uemura, Megumi Asada, Akira Kuzuya, Shigeki Yamada, Masatsune Ishikawa, Takashi Kawahara, Takuya Iwasaki, Masamichi Atsuchi, Ryosuke Takahashi, Ayae Kinoshita
Two-Point Dynamic Observation of Alzheimer’s Disease Cerebrospinal Fluid Biomarkers in Idiopathic Normal Pressure Hydrocephalus
Abstract: Background: Extensive research into cerebrospinal fluid (CSF) biomarkers was performed in patients with idiopathic normal pressure hydrocephalus (iNPH). Most prior research into CSF biomarkers has been one-point observation. Objective: To investigate dynamic changes in CSF biomarkers during routine tap test in iNPH patients. Methods: We analyzed CSF concentrations of tau, amyloid-β (Aβ) 42 and 40, and leucine rich α-2-glycoprotein (LRG) in 88 consecutive potential iNPH patients who received a tap test. We collected two-point lumbar CSF separately at the first 1 ml (First Drip (FD)) and at the last 1 ml (Last Drip (LD)) during the tap test and 9 patients who went on to receive ventriculo-peritoneal shunt surgery each provided 1 ml of ventricular CSF (VCSF). Results: Tau concentrations were significantly elevated in LD and VCSF compared to FD (LD/FD = 1.22, p = 0.003, VCSF/FD = 2.76, p = 0.02). Conversely, Aβ42 (LD/FD = 0.80, p < 0.001, VCSF/FD = 0.38, p = 0.03) and LRG (LD/FD = 0.74, p < 0.001, VCSF/FD = 0.09, p = 0.002) concentrations were significantly reduced in LD and VCSF compared to FD. Gait responses to the tap test and changes in cognitive function in response to shunt were closely associated with concentrations of tau (p = 0.02) and LRG (p = 0.04), respectively. Conclusions: Dynamic changes were different among the measured CSF biomarkers, suggesting that LD of CSF as sampled during the tap test reflects an aspect of VCSF contributing to the pathophysiology of iNPH and could be used to predict shunt effectiveness.
Rebecca L. Robinson, Dorene M. Rentz, Valerie Bruemmer, Jeffrey Scott Andrews, Anthony Zagar, Yongin Kim, Ronald L. Schwartz, Wenyu Ye, Howard M. Fillit
Observation of Patient and Caregiver Burden Associated with Early Alzheimer’s Disease in the United States: Design and Baseline Findings of the GERAS-US Cohort Study
Abstract: Background: Alzheimer’s disease (AD) is one of the costliest diseases in the United States. Objective: To describe aspects of real-world patient and caregiver burden in patients with clinician diagnosed early AD, including mild cognitive impairment (MCI) and mild dementia (MILD) due to AD. Methods: Cross-sectional assessment of GERAS-US, a 36-month cohort study of patients seeking care for early AD. Eligible patients were categorized based on study-defined categories of MCI and MILD and by amyloid positivity [+] or negativity [-] within each severity cohort. Demographic characteristics, health related outcomes, medical history, and caregiver burden by amyloid status are described. Results: Of 1,198 patients with clinician-diagnosed early AD, 52% were amyloid[+]. For patients in both cohorts, amyloid[-] was more likely to occur in those with: delayed time to an AD-related diagnosis, higher rates of depression, poorer Bath Assessment of Subjective Quality of Life in Dementia scores, and Hispanic/Latino ethnicity (all p<0.05). MILD[-] patients (versus MILD[+]) were more medically complex with greater rates of depression (55.7% versus 40.4%), sleep disorders (34.3% versus 26.5%), and obstructive pulmonary disease (11.8% versus 6.6%); and higher caregiver burden (Zarit Burden Interview) (all p<0.05). MILD[+] patients had lower function according to the Functional Activities Questionnaire (p<0.001), yet self assessment of cognitive complaints across multiple measures did not differ by amyloid status in either severity cohort. Conclusions: Considerable patient and caregiver burden was observed in patient’s seeking care for memory concerns. Different patterns emerged when both disease severity and amyloid status were evaluated underscoring the need for further diagnostic assessment and care for patients.
Somayeh Meysami, Cyrus A. Raji, David A. Merrill, Verna R. Porter, Mario F. Mendez
MRI Volumetric Quantification in Persons with a History of Traumatic Brain Injury and Cognitive Impairment
Abstract: Background: While traumatic brain injury (TBI) is recognized as a risk factor for dementia, there is lack of clinical tools to identify brain changes that may confer such vulnerability. Brain MRI with volumetrics can sensitively identify brain atrophy. Objective: To characterize regional brain volume loss in persons with TBI presenting with cognitive impairment. Methods: IRB approved review of medical records in patients with cognitive decline focused on those who had documented TBI histories and brain MRI scans after TBI (n=40, 67.7±14.5 years) with volumetric quantification by applying an FDA cleared software program. TBI documentation included head trauma mechanism. Brain volumes were compared to a normative database to determine the extent of atrophy. Correlations between these regions and global tests of cognition (MMSE in n=17, MoCA in n=27, n=14 in both) were performed. Results: Multiple regions demonstrated volume loss in TBI, particularly ventral diencephalon, putamen, and pallidum with smaller magnitude of atrophy in temporal lobes and brainstem. Lobar structures showed strongest correlations between atrophy and lower scores on MMSE and MoCA. The hippocampus, while correlated to tests of cognitive function, was the least atrophic region as a function of TBI history. Conclusion: Persons with TBI history exhibit show regional brain atrophy. Several of these areas, such as thalamus and temporal lobes, also correlate with cognitive function. Alzheimer’s disease atrophy was less likely given relative sparing of the hippocampi. Volumetric quantification of brain MRI in TBI warrants further investigation to further determine its clinical potential in TBI and differentiating causes of cognitive impairment.
Alexandre Amlie-Wolf*, Mitchell Tang*, Jessica Way, Beth Dombroski, Ming Jiang, Nicholas Vrettos, Yi-Fan Chou, Yi Zhao, Amanda Kuzma, Elisabeth E. Mlynarski, Yuk Yee Leung, Christopher D. Brown, Li-San Wang, Gerard D. Schellenberg (Handling Associate Editor: Rita Guerreiro) *These authors contributed equally to this work.
Inferring the Molecular Mechanisms of Noncoding Alzheimer’s Disease-Associated Genetic Variants
Abstract: Most of the loci identified by genome-wide association studies (GWAS) for late-onset Alzheimer’s disease (LOAD) are in strong linkage disequilibrium (LD) with nearby variants all of which could be the actual functional variants, often in non-protein-coding regions and implicating underlying gene regulatory mechanisms. We set out to characterize the causal variants, regulatory mechanisms, tissue contexts, and target genes underlying these associations. We applied our INFERNO algorithm to the top 19 non-APOE loci from the IGAP GWAS study. INFERNO annotated all LD-expanded variants at each locus with tissue-specific regulatory activity. Bayesian co-localization analysis of summary statistics and eQTL data was performed to identify tissue-specific target genes. INFERNO identified enhancer dysregulation in all 19 tag regions analyzed, significant enrichments of enhancer overlaps in the immune-related blood category, and co-localized eQTL signals overlapping enhancers from the matching tissue class in ten regions (ABCA7, BIN1, CASS4, CD2AP, CD33, CELF1, CLU, EPHA1, FERMT2, ZCWPW1). In several cases, we identified dysregulation of long noncoding RNA (lncRNA) transcripts and applied the lncRNA target identification algorithm from INFERNO to characterize their downstream biological effects. We also validated the allele-specific effects of several variants on enhancer function using luciferase expression assays. By integrating functional genomics with GWAS signals, our analysis yielded insights into the regulatory mechanisms, tissue contexts, genes, and biological processes affected by noncoding genetic variation associated with LOAD risk.
Elena L. Paley
Discovery of Gut Bacteria Specific to Alzheimer’s Associated Diseases Is a Clue to Understanding Disease Etiology: Meta-Analysis of Population-Based Data on Human Gut Metagenomics and Metabolomics
Abstract: Alzheimer’s disease (AD)-associated sequence (ADAS) of cultured fecal bacteria was discovered in human gut targeted screening. This study provides important information to expand our current understanding of the structure/activity relationship of ADAS and putative inhibitors/activators that are potentially involved in ADAS appearance/disappearance. The NCBI database analysis revealed that ADAS presents at a large proportion in American Indian Oklahoman (C&A) with a high prevalence of obesity/diabetes and in colorectal cancer (CRC) patients from the US and China. An Oklahoman non-native group (NNI) showed no ADAS. Comparison of two large US populations reveals that ADAS is more frequent in individuals aged ≥66 and in females. Prevalence and levels of fecal metabolites are altered in the C&A and CRC groups versus controls. Biogenic amines (histamine, tryptamine, tyramine, phenylethylamine, cadaverine, putrescine, agmatine, spermidine) that present in food and are produced by gut microbiota are significantly higher in C&A (e.g., histamine/histidine 95-fold) versus NNI (histamine/histidine 16-fold). The majority of these bio-amines are cytotoxic at concentrations found in food. Inositol phosphate signaling implicated in AD is altered in C&A and CRC. Tryptamine stimulated accumulation of inositol phosphate. The seizure-eliciting tryptamine induced cytoplasmic vacuolization and vesiculation with cell fragmentation. Present additions of ADAS-carriers at different ages including infants led to an ADAS-comprising human sample size of 2,830 from 27 studies from four continents (North America, Australia, Asia, Europe). Levels of food-derived monoamine oxidase inhibitors and anti-bacterial compounds, the potential modulators of ADAS-bacteria growth and biogenic amine production, were altered in C&A versus NNI. ADAS is attributable to potentially modifiable risk factors of AD associated diseases.