Greg Kennedy, BSc (Hons), Recipient of the 2018 Alzheimer Award
Morgane Piton, Christophe Hirtz, Caroline Desmetz, Jacqueline Milhau, Anne Dominique Lajoix, Karim Bennys, Sylvain Lehmann, Audrey Gabelle
Alzheimer’s Disease: Advances in Drug Development
Abstract: As of 2018, Alzheimer’s disease (AD) is the most common form of neurodegenerative dementia. It contributes to a progressive neuron loss, deterioration of memory, and cognitive impairment. Current therapies may provide a symptomatic benefit, but do not treat the underlying process. Ongoing researches focus on understanding the causal mechanisms and finding neuropathological hallmarks of AD. Therapeutic approaches targeting senile plaques or neurofibrillary tangles have not yet resulted in a significant cognitive improvement. However, recent data according to the analysis of AD clinical trials (clinicaltrials.gov database) show promising results. This literature review aims at summarizing the recent advances and at highlighting the most promising results of the ongoing researches. It compares the merits of small-molecules, antibodies, cell, and gene-based therapies and emphasizes the need for treatment at earlier stages of the disease.
Rui Chen*, Jiangwei Shi*, Qingsheng Yin, Xiaojin Li, Yanyuan Sheng, Juan Han, Pengwei Zhuang, Yanjun Zhang *These authors contributed equally to this work.
Morphological and Pathological Characteristics of Brain in Diabetic Encephalopathy
Abstract: Diabetes mellitus is a metabolic disease often accompanied by a series of complications, such as diabetic nephropathy, retinopathy, and diabetic foot. The survival time of diabetics has been significantly prolonged due to advancements in medicine. However, the prolonged survival time for diabetics can increase the prevalence of diabetic central nervous system disease. Diabetic encephalopathy (DE) has become one of the main complications of the disease, and the main clinical manifestation of DE is cognitive dysfunction. However, the typical morphological and pathological characteristics of the brain in DE are rarely systematically reported. Thus, this phenomenon severely restricts the diagnosis and treatment of DE. This article presents a description of the pathology characteristics of DE, including atrophy of the brain (gray matter, white matter, and hippocampus), changes in cerebrovascular morphology and function, impairment of synaptic plasticity, and dysfunction of neuroglia. In addition, abnormalities in the glymphatic clearance system of the brain are closely related to the progression of DE. A review of typical brain morphological and pathological characteristics would aid in the diagnosis and treatment of DE.
Sebastian Aguayo, Christina Maria Anna Pia Schuh, Benjamin Vicente, Luis Gerardo Aguayo ( Handling Associate Editor: Jack de la Torre)
Association between Alzheimer’s Disease and Oral and Gut Microbiota: Are Pore Forming Proteins the Missing Link?
Abstract: Alzheimer’s disease (AD) is a neurodegenerative condition affecting millions of people worldwide. It is associated with cerebral amyloid-β (Aβ) plaque deposition in the brain, synaptic disconnection, and subsequent progressive neuronal death. Although considerable progress has been made to elucidate the pathogenesis of AD, the specific causes of the disease remain highly unknown. Recent research has suggested a potential association between certain infectious diseases and dementia, either directly due to bacterial brain invasion and toxin production, or indirectly by modulating the immune response. Therefore, in the present review we focus on the emerging issues of bacterial infection and AD, including the existence of antimicrobial peptides having pore-forming properties that act in a similar way to pores formed by Aβ in a variety of cell membranes. Special focus is placed on oral bacteria and biofilms, and on the potential mechanisms associating bacterial infection and toxin production in AD. The role of bacterial outer membrane vesicles on the transport and delivery of toxins as well as porins to the brain is also discussed. Aβ has shown to possess antimicrobial activity against several bacteria, and therefore could be upregulated as a response to bacteria and bacterial toxins in the brain. Although further research is needed, we believe that the control of biofilm-mediated diseases could be an important potential prevention mechanism for AD development.
Conrad N. Trumbore
Shear-Induced Amyloid Formation in the Brain: III. The Roles of Shear Energy and Seeding in a Proposed Shear Model
Abstract: If cerebrospinal and interstitial fluids move through very narrow brain flow channels, these restrictive surroundings generate varying levels of fluid shear and different shear rates, and dissolved amyloid monomers absorb different shear energies. It is proposed that dissolved amyloid-β protein (Aβ) and other amyloid monomers undergo shear-induced conformational changes that ultimately lead to amyloid monomer aggregation even at very low brain flow and shear rates. Soluble Aβ oligomers taken from diseased brains initiate in vivo amyloid formation in non-diseased brains. The brain environment is apparently responsible for this result. A mechanism involving extensional shear is proposed for the formation of a seed Aβ monomer molecule that ultimately promotes templated conformational change of other Aβ molecules. Under non-quiescent, non-equilibrium conditions, gentle extensional shear within the brain parenchyma, and perhaps even during laboratory preparation of Aβ samples, may be sufficient to cause subtle conformational changes in these monomers. These result from brain processes that significantly lower the high activation energy predicted for the quiescent Aβ dimerization process. It is further suggested that changes in brain location and changes brought about by aging expose Aβ molecules to different shear rates, total shear, and types of shear, resulting in different conformational changes in these molecules. The consequences of such changes caused by variable shear energy are proposed to underlie formation of amyloid strains causing different amyloid diseases. Amyloid researchers are urged to undertake studies with amyloids, anti-amyloid drugs, and antibodies while all of these are under shear conditions similar to those in the brain.
Colin Groot*, Nelleke Tolboom*, Milos D. Ikonomovic, Adriaan A. Lammertsma, Baayla D.C. Boon, Frederik Barkhof, Philip Scheltens, William E. Klunk, Annemieke J.M. Rozemuller, Rik Ossenkoppele, Bart N.M. van Berckel *These authors contributed equally to this work.
Quantitative PET and Histology of Brain Biopsy Reveal Lack of Selective Pittsburgh Compound-B Binding to Intracerebral Amyloidoma
Abstract: This single case study examines selective Pittsburgh compound-B (PiB) binding to an intracerebral light-chain amyloidoma using a 90-minute dynamic [11C]PiB-PET scan and brain biopsy tissue. Parametric non-displaceable binding potential (BPND) images showed low specific binding in the amyloidoma (BPND=0.23), while relative tracer delivery was adequate (R1=0.44). Histology of the tissue revealed strong coloring with Congo-red, thioflavin-S, and X-34, indicating presence of amyloid. However, immunological staining with 6F/3D revealed absence of amyloid-β and histofluorescence of 6-CN-PiB, a highly fluorescent derivative of PiB, was at background levels. Our results suggest that PiB does not detect the atypical amyloid pathology associated with an intracerebral light-chain amyloidoma. These findings are of interest to clinicians and researchers applying [11C]PiB-PET to detect atypical forms of amyloid pathology.
Stephen T. Chen*, Prabha Siddarth*, David A. Merrill, Jacqueline Martinez, Natacha D. Emerson, Jie Liu, Koon-Pong Wong, Nagichettiar Satyamurthy, Christopher C. Giza, Sung-Cheng Huang, Robert P. Fitzsimmons, Julian Bailes, Bennet Omalu, Jorge R. Barrio, Gary W. Small *These authors contributed equally to this work.
FDDNP-PET Tau Brain Protein Binding Patterns in Military Personnel with Suspected Chronic Traumatic Encephalopathy
Abstract: Background: Our group has shown that in vivo tau brain binding patterns from FDDNP-PET scans in retired professional football players with suspected chronic traumatic encephalopathy differ from those of tau and amyloid aggregate binding observed in Alzheimer’s disease (AD) patients and cognitively-intact controls. Objective: To compare these findings with those from military personnel with histories of mild traumatic brain injury (mTBI). Methods: FDDNP-PET brain scans were compared among 7 military personnel and 15 retired players with mTBI histories and cognitive and/or mood symptoms, 24 AD patients, and 28 cognitively-intact controls. Nonparametric ANCOVAs with Tukey-Kramer adjusted post-hoc comparisons were used to test for significant differences in regional FDDNP binding among subject groups. Results: FDDNP brain binding was higher in military personnel compared to controls in the amygdala, midbrain, thalamus, pons, frontal and anterior and posterior cingulate regions (p<0.01-0.0001). Binding patterns in the military personnel were similar to those of the players except for the amygdala and striatum (binding higher in players; p=0.02-0.003). Compared with the AD group, the military personnel showed higher binding in the midbrain (p=0.0008) and pons (p=0.002) and lower binding in the medial temporal, lateral temporal, and parietal regions (all p=0.02). Conclusion: This first study of in vivo tau and amyloid brain signals in military personnel with histories of mTBI shows binding patterns similar to those of retired football players and distinct from the binding patterns in AD and normal aging, suggesting the potential value of FDDNP-PET for early detection and treatment monitoring in varied at-risk populations.
Francisco P.M. Oliveira, Ana Paula Moreira, Alexandre de Mendonça, Ana Verdelho, Carolina Xavier, Dalila Barroca, Joana Rio, Eva Cardoso, Ângela Cruz, Antero Abrunhosa, Miguel Castelo-Branco
Can 11C-PiB-PET Relative Delivery R1 or 11C-PiB-PET Perfusion Replace 18F-FDG-PET in the Assessment of Brain Neurodegeneration?
Abstract: Background: Pittsburgh Compound B (PiB) positron emission tomography (PET) is used to visualize in vivo amyloid plaques in the brain. Frequently the PiB examinations are complemented with a fluorodeoxyglucose (FDG) PET scan to further assess neurodegeneration. Objective: Our goal is to identify alternative correlates of FDG images by assessing which kinetic methods originate PiB derived relative delivery ratio (R1) images that can be correlated with the FDG images, and to also compare them with PiB perfusion (pPiB) images obtained from the early-phase of PiB acquisition. Methods: We selected 52 patients with cognitive impairment who underwent a dynamic PiB and FDG acquisitions. To compute the R1 images, two simplified reference tissue models (SRTM and SRTM2) and two multi-linear reference tissue models (MRTM and MRTM2) were used. The pPiB images were obtained in two different time intervals. Results: All six types of images were of good quality and highly correlated with the FDG images (mean voxelwise within-subjects r > 0.92). The higher correlation was found for FDG-R1(MRTM). Regarding the voxelwise regional correlation, the higher mean all brain correlations was r = 0.825 for FDG-R1(MRTM) and statistically significant in the whole brain analysis. Conclusion: All R1 and pPiB images here tested have potential to assess the metabolic impact of neurodegeneration almost as reliably as the FDG images. However, this is not enough to validate these images for a single-subject analysis compared with the FDG image, and thus they cannot yet be used clinically to replace the FDG image before such evaluation.
Lei Feng, Lisa Langsetmo, Kristine Yaffe, Ye Sun, Howard A. Fink, James M. Shikany, PC Leung, Nancy E. Lane, Jane A Cauley, for the Osteoporotic Fractures in Men (MrOS) Study Group (Handling Associate Editor: Jin-Tai Yu)
No Effects of Black Tea on Cognitive Decline Among Older US Men: A Prospective Cohort Study
Abstract: Background: Accumulating evidence supports the neuroprotective effects of bioactive compounds from tea leaves. There are limited data from black tea consumption populations. Objective: To determine whether black tea consumption is associated with cognitive decline among older men. Methods: We chose to study the association between black tea consumption and cognition using data from the Osteoporotic Fractures in Men (MrOS) cohort, which collected information on tea consumption at baseline and has repeatedly assessed cognitive function in 3,844 men aged 65+ years (mean=72.4 years). We defined tea drinkers as those who drank black tea at least once per week and further grouped them into weekly drinkers and daily drinkers. Cognitive function was assessed at baseline and approximately 7 years later using the Modified Mini-Mental State Examination (3MSE). Multivariable logistic regression and linear regression models were constructed to assess the association between black tea consumption and risk of fast cognitive decline as a binary variable and change in 3MSE scores as continuous variable. Fast cognitive decline was defined as decline in 3MSE >1.5 standard deviation of mean change score. Models were adjusted for age, education level, and baseline cognitive scores. Results: Weekly and daily black tea drinkers were 24.8% and 12.4% of the study cohort, respectively. Fast cognitive decline occurred in 243 (6.3%) participants. Tea consumption was not associated with risk of cognitive decline, nor was tea associated with cognitive decline measured by absolute change in 3MSE scores. Conclusions: There was no association of black tea consumption and cognitive decline among older men in the US.
Edmarie Guzmán-Vélez*, Sehily Jaimes*, Daniel C. Aguirre-Acevedo, Daniel J. Norton, Kathryn V. Papp, Rebecca Amariglio, Dorene Rentz, Ana Baena, Eliana Henao, Victoria Tirado, Claudia Muñoz, Margarita Giraldo, Reisa A. Sperling, Francisco Lopera, Yakeel T. Quiroz (Handling Associate Editor: David Loewenstein) *These authors contributed equally to this manuscript.
A Three-Factor Structure of Cognitive Functioning Among Carriers and Non-Carriers of Autosomal-Dominant Alzheimer’s Disease
Abstract: Background: There is a need to find cognitive markers that can help identify individuals at risk for Alzheimer’s disease (AD), and that can be used to reliably measure cognitive decline. Objective: We tested whether a theoretically driven three-factor structure would characterize cognitive functioning in individuals who are genetically-determined to develop AD due to a mutation in Presenilin-1 (PSEN1) gene. We also examined whether these factors could distinguish cognitively unimpaired PSEN1 mutation carriers from age-matched non-carrier family members. Methods: 1,395 cognitively unimpaired members of a Colombian kindred with the PSEN1 E280A mutation were included in the study. A confirmatory factor analysis examined the fit of the three-factor model comprising episodic memory (MMSE memory recall, CERAD-COL Word list recall, and Constructional praxis recall), executive function (Phonemic fluency and WCST perseverative errors), and psychomotor processing speed (TMT-A and WAIS-III Digit Symbol). Results: The three-factor model provided an excellent fit for all participants (p=0.24; RMSEA=0.01). Further, the episodic memory (p=0.0004, d=0.25) and executive functioning (p=0.001, d=0.18) factors distinguished cognitively unimpaired carriers from non-carriers. The episodic memory factor provided the earliest indication of preclinical cognitive decline at 35 years of age, nine years before individuals’ estimated age of clinical onset. Conclusions: The three theoretically derived cognitive factors provide a reliable measure of cognition and may be useful for the early detection of AD, as well as for measuring disease progression. However, longitudinal studies are needed to confirm that these factors can be used to track the progression of cognitive decline in preclinical AD.
Abdulla Watad, Nicola L. Bragazzi, Shmuel Tiosano, Yarden Yavne, Doron Comaneshter, Arnon D. Cohen*, Howard Amital* *These authors contributed equally to this work.
Alzheimer’s Disease in Systemic Sclerosis Patients: A Nationwide Population-Based Cohort Study
Abstract: Background: Neurological features are often overlooked in systemic sclerosis (SSc) patients and little is known about the link between dementia and SSc. Objectives: We sought to investigate whether an association exists between Alzheimer’s disease (AD) and SSc, as well as assess the impact of a dual diagnosis on mortality rates, by performing an extensive data analysis on a large subject sample. Methods: We utilized the medical database of the Clalit-Health-Services in a case-control study. Patients with SSc were compared with age- and sex-matched controls with regard to the prevalence of AD and its impact on their mortality. Results: Our study included 2,431 SSc patients and 12,377 age- and sex-matched controls. The mean age of the study population was 63.32±18.06 years and the female to male ratio was 4.5:1. 134 (5.5%) cases had AD as a co-morbidity in comparison with 749 (5.9%) of the controls. The mortality rate was 12.5% among controls and 26.2% among SSc cases. On the Cox multivariate survival analysis, diagnosis of SSc and AD demonstrated significant HRs (2.35 (95%CI 2.05-2.69, p<0.0001) and 2.19 (95%CI 1.94-2.48, p<0.0001), respectively). SSc patients with AD had a relative risk of death of 2.35 (95%CI: 1.44-3.83) in comparison with SSc patients without AD. Conclusion: AD is a predictor of death in SSc and therefore preemptive screening may be warranted. Further studies are needed to evaluate whether improvements in the medical regimen for SSc may lead to a reduction in AD development and possibly to increased survival as well.
Noemi Malandrino, Esmeralda Capristo, Tracey H. Taveira, Geltrude Mingrone, Wen-Chih Wu (Handling Associate Editor: Suzanne de la Monte)
Cognitive Function in Individuals with Normal Weight Obesity: Results from the Third National Health and Nutrition Examination Survey (NHANES III)
Abstract: Background/Objective. Normal weight obesity (NWO) is associated with increased risk of metabolic syndrome, cardiovascular- and all-cause mortality. However, no data have been reported on the relationship between adiposity and cognitive performance in NWO. We therefore studied the association between cognitive function and body fat percentage (BF%) in NWO, using a representative sample of the United States population. Methods. A cross-sectional study was performed using the nationwide 1988 to 1994 data set from the Third National Health and Nutrition Examination Survey. Cognitive function was measured by three validated cognitive tests: simple reaction time test (SRTT), symbol digit substitution test (SDST), and serial digit learning test (SDLT). The association between BF% and cognitive performance was evaluated in 2,039 adults aged 20-59 years and with a body mass index ranging from 18.5 to 24.9 kg/m2. Linear regression modeling was used to adjust for potential confounders. Results. Increased BF% was significantly associated with poorer performance on SDLT in the entire study sample (coefficient [95%CI]: 0.15 [0.01, 0.29]) and with poorer performance on SDST in the age group 20-29 years (coefficient [95%CI]: 0.30 [0.10, 0.49]). Increased BF% did not significantly predict poorer performance on SRTT. Conclusion. Higher BF% is significantly associated with poorer cognitive function in a nationally representative sample of US adults with NWO. The identification of possible complications associated with increased adipose tissue underlines the need to measure body fat content in NWO individuals, whose metabolic and cognitive dysfunction could go undetected for years due to their young age and normal body weight.
Nanna A. Sobol, Christian Have Dall, Peter Høgh, Kristine Hoffmann, Kristian Steen Frederiksen, Asmus Vogel, Volkert Siersma, Gunhild Waldemar, Steen G. Hasselbalch, Nina Beyer
Change in Fitness and the Relation to Change in Cognition and Neuropsychiatric Symptoms After Aerobic Exercise in Patients with Mild Alzheimer’s Disease
Abstract: Background: Physical activity has the potential to improve physical function in patients with Alzheimer’s disease (AD) and may contribute to modify disease processes and cognitive function. Objective: The aim of this study was to investigate 1) the effect of moderate-high-intensity aerobic exercise on cardiorespiratory fitness, i.e., peak oxygen uptake (VO2peak) determined by direct breath-by-breath cardiopulmonary exercise test, and 2) the association between changes in VO2peak and changes in cognition and neuropsychiatric symptoms in patients with mild AD. Methods: The study is based on secondary outcome analyses from the large single-blinded multi-center study ADEX (Preserving Cognition, Quality of Life, Physical Health and Functional Ability in Alzheimer’s Disease: The Effect of Physical Exercise). A preselected sub-group of 55 participants (age 52-83 years), 29 from the intervention group (IG) and 26 from the control group (CG), was included. IG performed 16 weeks of supervised moderate-to-high intensity aerobic exercise. Assessments of VO2peak, mental speed and attention (Symbol Digit Modalities Test, SDMT), and neuropsychiatric symptoms (Neuropsychiatric Inventory, NPI) were performed at baseline and at 16 weeks. Result: VO2peak increased 13% in the IG and a between-group difference in mean change (3.92 ml/kg/min, 95% CI 6.34-1.51, p=0.003) was present in favor of the IG. Combined data from IG and CG showed positive associations between changes in VO2peak and changes in NPI (Rho=-0.41, p=0.042) and changes in SDMT (Rho=0.36, p=0.010), respectively. Conclusion: Aerobic exercise improves VO2peak in community-dwelling patients with mild AD. Furthermore, changes in VO2peak appear to be associated to changes in cognition and neuropsychiatric symptoms.
Leila Sellami*, Martina Bocchetta*, Mario Masellis, David M. Cash, Katrina M. Dick, John van Swieten, Barbara Borroni, Daniela Galimberti, Maria Carmela Tartaglia, James B. Rowe, Caroline Graff, Fabrizio Tagliavini, Giovanni Frisoni, Elizabeth Finger, Alexandre de Mendonça, Sandro Sorbi, Jason D. Warren, Jonathan D. Rohrer#, Robert Jr Laforce#, on behalf of the Genetic FTD Initiative, GENFI *These authors contributed equally to this work. #Joint senior authors
Distinct Neuroanatomical Correlates of Neuropsychiatric Symptoms in the Three Main Forms of Genetic Frontotemporal Dementia in the GENFI Cohort
Abstract: Background: The overlap between frontotemporal dementia (FTD) and primary psychiatric disorders has been brought to light by reports of prominent neuropsychiatric symptoms (NPS) in FTD-related genetic mutations, particularly among C9orf72 and GRN carriers. It has been recently demonstrated that early neuroanatomical changes in genetic FTD may be different across the major disease-causing mutations. Objective: We aimed to identify whether NPS could be driven by distinct structural correlates. Methods: One hundred and sixty-seven mutation carriers (75 GRN, 60 C9orf72, and 32 MAPT) were included from the Genetic FTD Initiative (GENFI) study, a large international cohort of genetic FTD. Neuropsychiatric symptoms including delusions, hallucinations (visual, auditory, and tactile), depression, and anxiety were investigated using a structured interview. Voxel-based morphometry was performed to identify neuroanatomical correlates of NPS. Results: Psychotic symptoms correlated mainly with grey matter (GM) atrophy in the anterior insula, left thalamus, cerebellum, and cortical regions including frontal, parietal, and occipital lobes in GRN mutations carriers. GM atrophy in posterior structures of the default-mode network was associated with anxiety in the GRN group. Delusions in C9orf72 expansion carriers were mainly associated with left frontal cortical atrophy. Cerebellar atrophy was found to be correlated only with anxiety in C9orf72 carriers. NPS in the MAPT group were mainly associated with volume loss in the temporal lobe. Conclusion: Neuroanatomical correlates of NPS appear to be distinct across the main forms of genetic FTD. Overall, our findings support overlapping brain structural changes between FTD and primary psychiatric disorders.
Kaja Plucińska, Barry Crouch, Jie M Yeap, Sandra Stoppelkamp, Gernot Riedel, Bettina Platt
Histological and Behavioral Phenotypes of a Novel Mutated APP Knock-In Mouse
Abstract: Gene mutations within amyloid precursor protein (APP or AβPP) and/or presenilin 1 (PS1) genes are determinants of familial Alzheimer’s disease (fAD) and remain fundamental for experimental models. Here, we generated a neuronal knock-in mouse (PLB2APP) with mutated human APPSwe/Lon and investigated histopathology and behavioral phenotypes. Additionally, PLB2APP mice were cross-bred with a presenilin (PS1A246E) line to assess the impact of this gene combination. Immunohistochemistry determined amyloid-β (Aβ) pathology, astrogliosis (via GFAP labelling), and neuronal densities in hippocampal and cortical brain regions. One-year old PLB2APP mice showed higher levels of intracellular Aβ in CA1, dentate gyrus, and cortical regions compared to PLBWT controls. Co-expression of PS1 reduced hippocampal but elevated cortical Aβ build-up. Amyloid plaques were sparse in aged PLB2APP mice, and co-expression of PS1 promoted plaque formation. Heightened GFAP expression followed the region-specific pattern of Aβ in PLB2APP and PLB2APP/PS1 mice. Behaviorally, habituation to a novel environment was delayed in 6-month-old PLB2APP mice, and overall home-cage activity was reduced in both lines at 6 and 12 months, particularly during the dark phase. Spatial learning in the water maze was impaired in PLB2APP mice independent of PS1 expression and associated with reduced spatial navigation strategies. Memory retrieval was compromised in PLB2APP mice only. Our data demonstrate that low expression of APP is sufficient to drive histopathological and cognitive changes in mice without overexpression or excessive plaque deposition. AD-like phenotypes were altered by co-expression of PS1, including a shift from hippocampal to cortical Aβ pathology, alongside reduced deficits in spatial learning.
Gonzalo Sánchez-Benavides, Oriol Grau-Rivera, Raffaele Cacciaglia, Marc Suárez-Calvet, Carles Falcon, Carolina Minguillon, Nina Gramunt, Aleix Sala-Vila, ALFA study, Juan Domingo Gispert, José Luis Molinuevo
Distinct Cognitive and Brain Morphological Features in Healthy Subjects Unaware of Informant-Reported Cognitive Decline
Abstract: Background: Subtle cognitive decline preceding cognitive impairment can be self-perceived, referred to as subjective cognitive decline (SCD), or go unrecognized. Objective: To study the clinical, cognitive, and structural neuroimaging characteristics of psychometrically normal subjects without self-awareness of cognitive decline (unaware decliners, UD) and to compare them with SCD participants and controls. Methods: 2,640 participants from the ALFA cohort, 1,899 controls, 173 UD (decline reported by the informant only), and 568 SCD underwent clinical and cognitive explorations. A subset of 530 underwent structural MRI (379 Controls; 43 UD; 108 SCD). Linear models adjusting for confounders (age, sex, education, and mood state) were used to assess group differences on cognition and voxel-wise grey matter (GM) volumes. Results: 6.6% were UD while 21.5% SCD. No differences in anxiety and depression were observed between controls and UD, while SCD did (p<0.01). UD showed lower performance in the Memory Binding Test free recall (p<0.005) than controls, but no differences compared to SCD. Right medial frontal and insular increments of GM volumes were observed in UD with respect to controls. Informant report of decline in UD and SCD was associated with lower left hippocampal GM volume but related to memory performance only in UD (rho=0.46, p=0.002). Conclusions: UD had worse memory performance than controls which correlated with hippocampal GM volume and presented brain volume increments in self-appraisal areas (medial frontal and insula). Individuals unaware of cognitive decline may represent a distinct group at risk for cognitive impairment and support the usefulness of informant-reported cognitive decline.
Yazeli E. Cruz-Rivera, Jaileene Perez-Morales, Yaritza M. Santiago, Valerie M. Gonzalez, Luisa Morales, Mauricio Cabrera-Rios, Clara E. Isaza (Handling Associate Editor: George Acquaah-Mensah)
A Selection of Important Genes and Their Correlated Behavior in Alzheimer’s Disease
Abstract: In 2017, approximately 5 million Americans are living with Alzheimer’s disease (AD), and it is estimated that by 2050 this number could increase to 16 million. In this study, we apply mathematical optimization to approach microarray analysis to detect differentially expressed genes and determine the most correlated structure among their expression changes. The analysis of GSE4757 microarray dataset, which compares expression between AD neurons without neurofibrillary tangles (controls) and with neurofibrillary tangles (cases), was casted as a multiple criteria optimization (MCO) problem. Through the analysis it was possible to determine a series of Pareto efficient frontiers to find the most differentially expressed genes, which are here proposed as potential AD biomarkers. The Traveling Sales Problem (TSP) model was used to find the cyclical path of maximal correlation between the expression changes among the genes deemed important from the previous stage. This leads to a structure capable of guiding biological exploration with enhanced precision and repeatability. Ten genes were selected (FTL, GFAP, HNRNPA3, COX1, ND2, ND3, ND4, NUCKS1, RPL41, and RPS10) and their most correlated cyclic structure was found in our analyses. The biological functions of their products were found to be linked to inflammation and neurodegenerative diseases and some of them had not been reported for AD before. The TSP path connects genes coding for mitochondrial electron transfer proteins. Some of these proteins are closely related to other electron transport proteins already reported as important for AD.
Ana Gámez-Valero, Julia Canet-Pons, Aintzane Urbizu, Ana Anillo, Cristina Santos, Aurelio Ariza, Katrin Beyer
INDEL Length and Haplotypes in the β-Synuclein Gene: A Key to Differentiate Dementia with Lewy Bodies?
Abstract: Lewy body diseases (LBD) include Parkinson’s disease (PD) and dementia with Lewy bodies (DLB) and together with Alzheimer’s disease (AD) they show an important neuropathological and clinical overlap. The human alpha- and beta-synuclein genes (SNCA and SNCB) are key factors for the development of Lewy body diseases. Here, we aimed to analyze the genotype distribution of potentially functional SNPs in SNCA and SNCB, perform haplotype analysis for SNCB, and to identify functional insertion and deletion (INDEL) variations within the regulatory region of SNCB which might be responsible for the drastically diminished beta-synuclein levels reported for pure DLB. Thus, we genotyped brain samples from AD, DLB, PD, and healthy controls for two SNCA and four SNCB SNPs. We also analyzed INDEL variations upstream of SNCB, determined SNCB expression levels, and correlated INDEL lengths with expression levels. Applying Fisher’s exact, chi-square, ANOVA tests, and the ΔΔCt method, we found disease-specific genotype distribution of SNCA and SNCB SNPs. Additionally, we identified three INDEL variations upstream of SNCB and showed that the INDEL allele lengths were associated with SNCB expression levels. INDEL alleles associated with low SNCB expression were accumulated in pure DLB. Finally, one major and four minor DLB specific SNCB haplotypes were identified with Haploview and Arlequin. In summary, our study showed that different SNCA and SNCB genotypes are associated with the development of either PD or DLB, and that the frequencies of genotypes associated with low SNCB expression are elevated in DLB.
Alessandro Padovani, Alberto Benussi, Valentina Cantoni, Valentina Dell’Era, Maria Sofia Cotelli, Salvatore Caratozzolo, Rosanna Turrone, Luca Rozzini, Antonella Alberici, Daniele Altomare, Alessandro Depari, Alessandra Flammini, Giovanni B. Frisoni, Barbara Borroni (Handling Associate Editor: Andrea Arighi)
Diagnosis of Mild Cognitive Impairment Due to Alzheimer’s Disease with Transcranial Magnetic Stimulation
Abstract: Background: Considering the increasing evidence that disease-modifying treatments for Alzheimer's disease (AD) must be administered early in the disease course, the development of diagnostic tools capable of accurately identifying AD at early disease stages has become a crucial target. In this view, transcranial magnetic stimulation (TMS) has become an effective tool to discriminate between different forms of neurodegenerative dementia. Objective: To determine whether a TMS multi-paradigm approach can be used to correctly identify mild cognitive impairment (MCI) due to AD (AD MCI). Methods: A sample of 69 subjects with MCI were included and classified as AD MCI or MCI unlikely due to AD (non-AD MCI) based on 1) extensive neurological and neuropsychological evaluation, 2) MRI imaging, and 3) cerebrospinal fluid analysis or/and amyloid PET imaging. A paired-pulse TMS multi-paradigm approach assessing short interval intracortical inhibition-facilitation (SICI-ICF), dependent on GABAergic and glutamatergic intracortical circuits, respectively, and short latency afferent inhibition (SAI), dependent on cholinergic circuits, was performed. Results: We observed a significant impairment of SAI and unimpaired SICI and ICF in AD MCI as compared to non-AD MCI. According to ROC curve analysis, the SICI-ICF / SAI index differentiated AD MCI from non-AD MCI with a specificity of 87.9% and a sensitivity of 94.4%. Conclusions: The assessment of intracortical connectivity with TMS could aid in the characterization of MCI subtypes, correctly identifying AD pathophysiology. TMS can be proposed as an adjunctive, non-invasive, inexpensive, and time-saving screening tool in MCI differential diagnosis.
Amanda Douglass, Mark Walterfang, Dennis Velakoulis, Larry Abel (Handling Associate Editor: Sharon Savage)
Behavioral Variant Frontotemporal Dementia Performance on a Range of Saccadic Tasks
Abstract: Background: Saccadic paradigms display changes across a number of degenerative conditions reflecting changes in the oculomotor pathway which in some conditions have been linked to disease presentation. Objective: To examine a novel range of saccadic paradigms in behavioral variant frontotemporal dementia (bvFTD). Methods: Prosaccade, predictive, self-paced, memory-guided, and anti-saccade tasks were examined in bvFTD patients and controls. Results: A significant increase in latency for the bvFTD group was seen in all tasks. Self-paced saccades are reduced in number, memory-guided saccades display an increase in errors. Predictive saccades show an increased latency that does not remain when prosaccades latency changes are accounted for. While changes were seen across a range of paradigms, no individual task completely separated bvFTD from control participants. Conclusion: bvFTD patients as a group display a number of changes on saccadic testing which may reflect the frontal lobe changes seen in this condition.
Yiren Qin*, Yu Zhang*, Inge Tomic, Wenlin Hao, Michael D. Menger, Chunfeng Liu, Klaus Fassbender, Yang Liu (Handling Associate Editor: Jianping Jia) *These authors contributed equally to this work.
Ginkgo biloba Extract EGb 761 and Its Specific Components Elicit Protective Protein Clearance Through the Autophagy-Lysosomal Pathway in Tau-Transgenic Mice and Cultured Neurons
Abstract: Alzheimer’s disease (AD) is a neurodegenerative disease pathologically characterized by extracellular amyloid-β (Aβ) deposits and intracellular neurofibrillary tangles (NFT) in many brain regions. NFT are primarily composed of hyperphosphorylated tau protein (p-Tau). Aβ and p-Tau are two major pathogenic molecules with tau acting downstream to Aβ to induce neuronal degeneration. In this study, we investigated whether Ginkgo biloba extract EGb 761 reduces cerebral p-Tau level and prevents AD pathogenesis. Human P301S tau mutant-transgenic mice were fed with EGb 761, added to the regular diet for 2 or 5 months. We observed that treatment with EGb 761 for 5 months significantly improved the cognitive function of mice, attenuated the loss of synaptophysin and recovered the phosphorylation of CREB in the mouse brain. Treatment with EGb 761 for 5 but not 2 months also decreased p-Tau protein amount and shifted microglial pro-inflammatory to anti-inflammatory activation in the brain. As potential therapeutic mechanisms, we demonstrated that treatment with EGb 761, especially the components of ginkgolide A, bilobalide, and flavonoids, but not with purified ginkgolide B or C, increased autophagic activity and degradation of p-Tau in lysosomes of neurons. Inhibiting ATG5 function or treating cells with Bafilomycin B1 abolished EGb 761-enhanced degradation of p-Tau in cultured neurons. Additionally, we observed that 5- instead of 2-month-treatment with EGb 761 inhibited the activity of p38-MAPK and GSK-3β. Therefore, long-term treatment with Ginkgo biloba extract EGb 761, a clinically available and well-tolerated herbal medication, ameliorates AD pathology through mechanisms against multiple AD pathogenic processes.
Marc Vandermeeren*, Marianne Borgers*, Kristof Van Kolen, Clara Theunis, Bruno Vasconcelos, Astrid Bottelbergs, Cindy Wintmolders, Guy Daneels, Roland Willems, Koen Dockx, Lore Delbroek, André Marreiro, Luc Ver Donck, Cristiano Sousa, Rupesh Nanjunda, Eilyn Lacy, Tom Van De Casteele, Debby Van Dam, Peter Paul De Deyn, John A. Kemp, Thomas J. Malia, Marc H. Mercken *These authors contributed equally to this work.
Anti-Tau Monoclonal Antibodies Derived from Soluble and Filamentous Tau Show Diverse Functional Properties in vitro and in vivo
Abstract: The tau spreading hypothesis provides rationale for passive immunization with an anti-tau monoclonal antibody to block seeding by extracellular tau aggregates as a disease-modifying strategy for the treatment of Alzheimer’s disease (AD) and potentially other tauopathies. As the biochemical and biophysical properties of the tau species responsible for the spatio-temporal sequences of seeding events are poorly defined, it is not yet clear which epitope is preferred for obtaining optimal therapeutic efficacy. Our internal tau antibody collection has been generated by immunizations with different tau species: aggregated- and non-aggregated tau and human postmortem AD brain-derived tau fibrils. In this communication, we describe and characterize a set of these anti-tau antibodies for their biochemical and biophysical properties, including binding, tissue staining by immunohistochemistry, and epitope. The antibodies bound to different domains of the tau protein and some were demonstrated to be isoform-selective (PT18 and hTau56) or phospho-selective (PT84). Evaluation of the antibodies in cellular- and in vivo seeding assays revealed clear differences in maximal efficacy. Limited proteolysis experiments support the hypothesis that some epitopes are more exposed than others in the tau seeds. Moreover, antibody efficacy seems to depend on the structural properties of fibrils purified from tau Tg mice- and postmortem human AD brain.
Roberta Mercorio*, Laura Pergoli*, Daniela Galimberti, Chiara Favero, Michele Carugno, Elisabetta Dalla Valle, Francesco Barretta, Francesca Cortini, Elio Scarpini, Valentina Bollati Valentina, Angela Cecilia Pesatori *These authors contributed equally to this work.
PICALM Gene Methylation in Blood of Alzheimer’s Disease Patients Is Associated with Cognitive Decline
Abstract: Epigenetic mechanisms might be involved in Alzheimer’s disease (AD). Genetic polymorphisms in several genes, including APOE (Apolipoprotein E), PSEN1 (Presenilin 1), CR1 (Complement receptor 1), and PICALM (Phosphatidylinositol binding clathrin assembly protein), have been associated to an increased AD risk. However, data regarding methylation of these specific genes are lacking. We evaluated DNA methylation measured by quantitative bisulfite-PCR pyrosequencing in 43 AD patients and 38 healthy subjects (HS). In a multivariate age- and gender-adjusted model, PICALM methylation was decreased in AD compared to HS (mean = 3.54 and 4.63, respectively, p = 0.007). In AD, PICALM methylation level was also positively associated to Mini-Mental Scale Examination (MMSE) score (percent change 3.48%, p = 0.008). Moreover, a negative association between PICALM methylation and age was observed only in HS (percent change -2.29%, p = 0.002). In conclusion, our data suggest a possible role of PICALM methylation in AD, particularly related to cognitive function. Given the small study sample and the associative nature of our study, further prospective investigations are required to assess the dynamics of DNA methylation in the early stages of AD development.
Tammy M. Scott, Rafeeque A. Bhadelia, Wei Qiao Qiu, Marshal F. Folstein, Irwin H. Rosenberg
Small Vessel Cerebrovascular Pathology Identified by Magnetic Resonance Imaging Is Prevalent in Alzheimer’s Disease and Mild Cognitive Impairment: A Potential Target for Intervention
Abstract: Background: There is evidence that Alzheimer’s disease (AD) has significant cerebrovascular etiopathogenesis. Understanding potentially modifiable risk factors for vascular disease can help design long-term intervention strategies for controlling or preventing cognitive dysfunction attributable to cerebrovascular disease. Objective: To evaluate the presence and severity of markers of cerebrovascular pathology, its relationship to diagnostic categories of dementia, including AD, and association with the metabolic biomarker homocysteine. Methods: In a cross-sectional observational study, 340 community-dwelling elders received a clinical evaluation including brain MRI and neuropsychological tests. Dementia and mild cognitive impairment (MCI) were diagnosed by consensus committee. Fasting total plasma homocysteine was measured. Statistical analyses were adjusted for demographics and cerebrovascular risk factors. Results: Nearly 25% of those diagnosed with AD had small vessel infarcts (SVI). Periventricular white matter hyperintensity (pvWMHI) was prevalent in participants with AD (61%) or MCI (amnesic 61% and non-amnesic 54%, respectively). Participants with SVI and/or pvWMHI also had greater brain atrophy. Homocysteine concentrations were higher in individuals with cerebrovascular findings than in those without. In individuals with cerebrovascular disease, homocysteine was inversely related to executive function (p=0.022) and directly related to degree of brain atrophy (p=0.009). Conclusions: We demonstrated a significant prevalence of small vessel markers of cerebrovascular pathology in individuals diagnosed with AD, with a significant concurrence between cerebrovascular disease and brain and ventricular atrophy. While current research on AD has focused on amyloid-β peptide deposition, tau-pathology, and microglial activation and inflammation, greater attention to the cerebrovascular contribution to this neurodegenerative disease presents an additional target for therapeutic prevention and intervention.
Jordan I. Ali, Colette M. Smart, Jodie R. Gawryluk
Subjective Cognitive Decline and APOE ε4: A Systematic Review
Abstract: Individuals with subjective cognitive decline (SCD) report self-perceived declines in cognitive function but perform within normal limits on standardized tests. However, for some, these self-perceived changes may herald eventual decline to Alzheimer’s disease (AD). In light of this, the relationship between SCD and APOE ε4, a known genetic risk factor for AD, has garnered interest; however, no systematic review of this literature exists. The current review (n = 36 articles) examined the prevalence of APOE ε4 in SCD samples relative to healthy and objectively impaired samples, and summarized APOE ε4-related risk of conversion from SCD to AD. Univariate ANOVA indicated that APOE ε4 frequency was comparable between healthy control and SCD samples, yet significantly higher in objectively impaired samples (i.e., MCI, AD) relative to either of these groups. Narrative review provided mixed evidence linking coincident APOE ε4-positive genotype and SCD to structural neuropathology. Though there was little evidence to suggest that APOE ε4 predisposes individuals to developing SCD, both APOE ε4 and SCD were found to confer individual and multiplicative risk of conversion to objective cognitive impairment. Combined, it is likely that a relationship between APOE ε4, SCD, and AD exists, though its exact nature remains undetermined. A clearer understanding of these relationships is hindered by a lack of standardization in SCD classification and a dearth of longitudinal outcome research. Wide-scale adoption of genetic screening for dementia risk in persons with SCD is considered premature at this time. Ethical considerations and clinical implications of genetic testing for dementia risk are discussed.