Fiorella Casamenti, Cristina Grossi, Stefania Rigacci, Daniela Pantano, Ilaria Luccarini, Massimo Stefani
Oleuropein Aglycone: A Possible Drug against Degenerative Conditions. In Vivo Evidence of its Effectiveness against Alzheimer’s Disease
Abstract: The amyloid plaques and neurofibrillary tangles found in the Alzheimer’s disease (AD) brain arise as a result of self-assembly into fibrillar material of amyloid-β protein (Aβ) and hyperphosphorylated tau, respectively, through a pathological process starting with the appearance of aggregation nuclei and neurotoxic oligomers. Accordingly, the search of inhibitors of oligomer nucleation and growth is considered a promising target to prevent amyloid toxicity. In recent years, a number of dietary factors including antioxidants, vitamins, and polyphenols have been characterized for their ability to protect cells stressed by several factors including the presence of amyloid deposits as well as to inhibit amyloid self-assembly and cytotoxicity and some of them are currently in clinical trial. The present review summarizes the findings on the beneficial effects against neurodegeneration and other peripheral inflammatory and degenerative diseases of oleuropein aglycone (OLE), a natural phenol abundant in the extra virgin olive oil. The data presently available suggest that OLE could provide a protective and therapeutic effect against a number of pathologies, including Alzheimer’s disease (AD) as well as obesity, type 2 diabetes, non-alcoholic hepatitis, and other natural or experimentally-induced pathological conditions. Such a protection could result, at least in part, in a remarkable improvement of the pathological signs arising from stress conditions including oxidative stress, an excessive inflammatory response, and the presence of cytotoxic aggregated material. In particular, the recent data on the cellular and molecular correlates of OLE neuroprotection suggest it could also play a therapeutic role against AD.
Jessica A. Brommelhoff, David L. Sultzer (Handling Associate Editor: Gwenn Smith)
Brain Structure and Function Related to Depression in Alzheimer’s Disease: Contributions from Neuroimaging Research
Abstract: The development of minimally invasive in vivo methods for imaging the brain has allowed for unprecedented advancement in our understanding of brain-behavior relationships. Structural, functional, and multimodal neuroimaging techniques have become more sophisticated in detecting structural and physiological abnormalities that may underlie various affective disorders and neurological illnesses such as depression in Alzheimer’s disease (AD). In general, neuroimaging studies of depression in AD investigate whether depression is associated with damage to structures in specific neural networks involving frontal and subcortical structures or with functional disruption of cortical neural systems. This review provides an overview of how various imaging modalities have contributed to our understanding of the neurobiology of depression in AD. At present, the literature does not conclusively support any specific pathogenesis for depression, and it is not clear whether patients with AD and depression have histopathological and neurochemical characteristics that contribute to mood symptoms that are different from cognitively intact individuals with depression. Neuroimaging studies suggest that atrophy of temporal or frontal structures, white matter lesions in frontal lobe or subcortical systems, reduced activity in dorsolateral frontal cortex, or small vessel cerebrovascular disease may be associated with depression in AD. Conceptual, clinical, and methodological challenges in studying this relationship are discussed. Further work is needed to understand the specific brain structures, relevant white matter tracts, and interactions among them that are most important. This review concludes with potential directions for future research.
Massimo Leandri, Jackie Campbell, Luigi Molfetta, Cristina Barbera, Massimo Tabaton
Relationship between Balance and Cognitive Performance in Older People
Abstract: We investigated the relationship between balance and cognitive level in a group of 70 women with no definite Alzheimer’s disease or mild cognitive impairment diagnosis and no impairment of daily activity. Static stabilometry and the Montreal Cognitive Assessment (MoCA) test were performed. The antero-posterior sway component was demonstrated to be the best predictor of the MoCA overall score. As visual and proprioceptive components of balance could safely be excluded in our assessments, the vestibular system is to be considered as a putative link between balance and cognitive impairment.
Catherine Pan*, Ané Korff*, Douglas Galasko, Carmen Ginghina, Elaine Peskind, Ge Li, Joseph Quinn, Thomas J. Montine, Kevin Cain, Min Shi, Jing Zhang *These authors contributed equally to this work.
Diagnostic Values of Cerebrospinal Fluid T-Tau and Aβ42 using Meso Scale Discovery Assays for Alzheimer’s Disease
Abstract: Background. Meso Scale Discovery (MSD) recently established electrochemiluminescence-based assays to measure cerebrospinal fluid (CSF) levels of total tau (t-tau) and amyloid-β 1-42 peptide (Aβ42) that can aid in the diagnosis of Alzheimer’s disease (AD). The goal of this investigation is to independently evaluate this platform and establish cut-off values of these biomarkers for AD diagnosis. Objective. To validate the analytical and clinical performance of the MSD t-tau and Aβ42 kits and propose diagnostic cut-off values for the field. Methods. The analytical performance of the CSF t-tau and Aβ42 assays was determined, followed by assessment of diagnostic performance of CSF t-tau, Aβ42, and t-tau/Aβ42 in three clinically characterized cohorts. Results. Both MSD assays demonstrated consistent and stable analytical performance, as well as resistance to several important pre-analytic variables. Diagnostically, t-tau/Aβ42 performed the best. Conclusions. Our results independently confirm the analytical and clinical performance of the MSD CSF t-tau and Aβ42 assays. Based on a large, multi-center, clinically-diagnosed cohort, we propose for the first time candidate diagnostic cut-offs for MSD measured CSF t-tau, Aβ42, and t-tau/Aβ42. However, these values needs to be refined as more subjects are included and the assays are tested by other laboratories.
Bing Xie*, Huimin Zhou*, Rui Zhang, Mei Song, Lulu Yu, Lan Wang, Zanchao Liu, Qingfu Zhang, Dongsheng Cui, Xueyi Wang, Shunjiang Xu (Handling Associate Editor: Ling-Qiang Zhu) *These authors contributed equally to this work.
Serum miR-206 and miR-132 as Potential Circulating Biomarkers for Mild Cognitive Impairment
Abstract: MicroRNAs (miRNAs), a class of small, non-coding RNA molecules with gene regulatory functions, have emerged to play a critical role in the pathogenesis of a variety of diseases. Recently, circulating miRNAs have been reported as potential biomarkers for various pathologic conditions. The present study was performed to investigate the potential role of circulating miRNAs as diagnostic biomarkers for mild cognitive impairment (MCI). We collected 66 patients with MCI and 76 normal controls from our previous cross-sectional cohort study. Seven miRNAs (miR-206, miR-132, miR-193b, miR-130b, miR-20a, miR-296, and miR-329) related to Alzheimer’s disease (AD) were detected in serum using a quantitative real-time PCR (qRT-PCR) method. Each miRNA’s diagnostic performance was evaluated by receiver operating characteristic curves and the areas under curves (AUC) analysis. The levels of miR-206 and miR-132 in MCI patients’ serum were significantly elevated compared to normal controls. Combining detection of miR-206 and miR-132 achieved the highest AUC of 0.981, followed by test of miR-206 (AUC = 0.880) and miR-132 (AUC = 0.912) separately. Importantly, miR-206 and miR-132 were respectively correlated with the Montreal Cognitive Assessment score in MCI patients. These results preliminarily indicated that circulating miR-206 and miR-132 as novel miRNAs upregulated in MCI patient were potential biomarkers for diagnosis of MCI.
Petrus J.W. Naudé*, Alain D. Dekker*, Antonia M.W. Coppus, Yannick Vermeiren, Ulrich L.M. Eisel, Cornelia M. van Duijn, Debby Van Dam, Peter P. De Deyn (Handling Associate Editor: Beatrice Arosio) *These authors contributed equally to this work.
Serum NGAL is Associated with Distinct Plasma Amyloid-β Peptides According to the Clinical Diagnosis of Dementia in Down Syndrome
Abstract: Background: The majority of people with Down syndrome (DS) develop dementia due to Alzheimer’s disease (AD). Neuropathological features are characterized by an accumulation of amyloid-β (Aβ) deposits and the presence of an activated immune response. Neutrophil Gelatinase-Associated Lipocalin (NGAL) is a newly identified (neuro)inflammatory constituent in AD. Objective: This study examines NGAL as an inflammatory marker in DS and its associations with plasma Aβ peptides according to the follow-up clinical diagnosis of dementia. Methods: Baseline serum NGAL and plasma Aβ40, Aβ42, Aβn40, and Aβn42 were quantified in 204 people with DS. The diagnosis of dementia in DS was established by follow-up clinical assessments. The following study groups were characterized: DS with AD at baseline (n=67), DS without AD (n=53), and non-demented DS individuals that converted to AD (n=84). Serum NGAL was analyzed in 55 elderly non-DS, non-demented people. Results: Serum NGAL levels were significantly increased in DS subjects compared to non-DS people. Serum NGAL levels were not associated with clinical dementia symptoms in DS. However, NGAL was positively associated with Aβ42 and Aβn42 in demented DS individuals and with Aβ40 and Aβn40 in the non-demented DS group. NGAL was negatively associated with Aβ42/Aβ40 and Aβn42/Aβn40 ratios in converted DS subjects. These associations persisted for Aβn40, Aβ42/Aβ40, and Aβn42/Aβn40 after adjusting for demographics measures, apolipoprotein E ε4 allele, platelets, and anti-inflammatory medication. Conclusion: Serum NGAL levels are increased in DS and associated with distinct species of Aβ depending on the progression of dementia as diagnosed by baseline and follow-up clinical assessments.
Fabrizio Vecchio, Francesca Miraglia, Giuseppe Curcio, Riccardo Altavilla, Federica Scrascia, Federica Giambattistelli, Carlo Cosimo Quattrocchi, Placido Bramanti, Fabrizio Vernieri, Paolo Maria Rossini
Cortical Brain Connectivity Evaluated by Graph Theory in Dementia: A Correlation Study Between Functional and Structural Data
Abstract: A relatively new approach to brain function in neuroscience is the “functional connectivity”, namely the synchrony in time of activity in anatomically-distinct but functionally-collaborating brain regions. On the other hand, diffusion tensor imaging (DTI) is a recently developed magnetic resonance imaging (MRI)-based technique with the capability to detect brain structural connection with fractional anisotropy (FA) identification. FA decrease has been observed in the corpus callosum of subjects with Alzheimer’s disease (AD) and mild cognitive impairment (MCI, an AD prodromal stage). Corpus callosum splenium DTI abnormalities are thought to be associated with functional disconnections among cortical areas. This study aimed to investigate possible correlations between structural damage, measured by MRI-DTI, and functional abnormalities of brain integration, measured by characteristic path length detected in resting state EEG source activity (40 participants: 9 healthy controls, 10 MCI, 10 mild AD, 11 moderate AD). For each subject, undirected and weighted brain network was built to evaluate graph core measures. eLORETA lagged linear connectivity values were used as weight of the edges of the network. Results showed that callosal FA reduction is associated to a loss of brain interhemispheric functional connectivity characterized by increased delta and decreased alpha path length. These findings suggest that “global” (average network shortest path length representing an index of how efficient is the information transfer between two parts of the network) functional measure can reflect the reduction of fiber connecting the two hemispheres as revealed by DTI analysis and also anticipate in time this structural loss.
Lilian Calderón-Garcidueñas, Antonieta Mora-Tiscareño, Maricela Franco-Lira, Hongtu Zhu, Zhaohua Lu , Edelmira Solorio, Ricardo Torres-Jardón, Amedeo D’Angiulli
Decreases in Short Term Memory, IQ, and Altered Brain Metabolic Ratios in Urban Apolipoprotein ε4 Children Exposed to Air Pollution
Abstract: Children’s urban air pollution exposures result in systemic and brain inflammation and the early hallmarks of Alzheimer’s disease (AD). The apolipoprotein E (APOE) ε4 allele is the most prevalent genetic risk for AD. We assessed whether APOE in healthy children modulates cognition, olfaction, and metabolic brain indices. The Wechsler Intelligence Scale for Children (WISC-R) and the University of Pennsylvania Smell Identification Test were administered to 50 Mexico City Metropolitan Area children (13.4 ± 4.8 years, 28 APOE ε3 and 22 APOE ε4). N-acetylaspartate (NAA)/creatine (Cr), choline (Cho)/Cr, myo-inositol (mI)/Cr, and NAA/mI were calculated using proton magnetic resonance spectroscopy in the white matter of the frontal and parietal lobes, hippocampus, and pons. APOE ε4 versus ε3 children had a reduced NAA/Cr ratio in the right frontal white matter and decrements on attention, short-term memory, and below-average scores in Verbal and Full Scale IQ (>10 points). APOE modulated the group effects between WISC-R and left frontal and parietal white matter, and hippocampus metabolites. Soap was the predominantly failed odor AD-related item in urban children and in APOE ε4 versus ε3 carriers strongly correlated with left hippocampus mI/Cr ratio. APOE modulates responses to air pollution on the developing brain. APOE ε4 carriers could have a higher risk of developing early AD if they reside in a polluted environment. APOE, cognition, and olfaction testing and targeted magnetic resonance spectroscopy may contribute to the assessment of urban children and their results could provide new paths toward the unprecedented opportunity for early neuroprotection and AD prevention.
Kosuke Matsuzono, Nozomi Hishikawa, Yasuyuki Ohta, Toru Yamashita, Kentaro Deguchi, Yumiko Nakano, Koji Abe
Combination Therapy of Choline Esterase Inhibitor (Donepezil or Galantamine) plus Memantine in the Okayama Memantine Study
Abstract: Background/Objective: To compare the effectiveness of combination therapy with cholinesterase inhibitors (ChEI) plus memantine in all AD patients and in older AD patients (age >75 years). Methods: The Okayama Memantine Study was used to compare the clinical effects of combination therapy of donepezil plus memantine (n = 61) or galantamine plus memantine (n = 53) in all AD patients, and in older AD patients separately, with six batteries at baseline, at 6 months with ChEI only monotherapy, and at 3, 6, and 12 months after addition of memantine to the treatment schedule (18 months total). Results: The addition of memantine resulted in stabilization of the Mini-Mental State Examination scores and Hasegawa dementia rating for 6 months, and then significantly declined at 12 months in both subgroups. Frontal assessment battery (FAB) declined significantly at 12 months after memantine addition in the donepezil subgroup, while the galantamine subgroup significantly improved at 6 months. Affective functions were well preserved after memantine addition until 12 months, except for the apathy scale at 12 months after memantine addition in the galantamine subgroup. The combination therapy of donepezil plus memantine was better for apathy in older AD patients, and galantamine plus memantine was better for cognitive functions. Conclusions: The addition of memantine stabilized cognitive scores for 6 months and affective scores for 12 months in the donepezil subgroup. Additionally, memantine significantly improved FAB at 6 months in the galantamine subgroup although apathy scale became significantly worse at 12 months.
Xiao Wang*, Jinhui Wang*, Yi He, Huiying Li, Huishu Yuan, Alan Evans, Xin Yu, Yong He, Huali Wang (Handling Associate Editor: Ludovico Minati) *These authors contributed equally to this work.
Apolipoprotein E ε4 Modulates Cognitive Profiles, Hippocampal Volume, and Resting-State Functional Connectivity in Alzheimer’s Disease
Abstract: The apolipoprotein E ε4 (APOE ε4) allele is a well-established genetic risk factor for Alzheimer’s disease (AD). Numerous studies have suggested that the modulation of APOE ε4 affects cognition and brain structure and function in healthy populations, particularly in the hippocampus, a key area associated with AD pathology. However, the effect of APOE ε4 allele on cognitive performance, hippocampal structural morphology, and specifically on functional characteristics in patients with AD remains poorly understood. Here, we employed a neuropsychological battery test and multi-modal structural MRI and resting-state functional MRI dataset to systematically investigate cognitive performance, hippocampal structural volume, and functional properties (including local low-frequency oscillating amplitude, intra-regional functional synchrony, and inter-regional functional connectivity) in 16 APOE ε4-carriers and 26 non-carriers at early stages of AD. Compared to non-carriers, APOE ε4-carriers exhibited poorer performance on recognition performance, but performed better on the late item generation of the verbal fluency task (associated with executive function). Structural imaging analysis revealed that APOE ε4-carriers exhibited smaller left hippocampal volumes compared to non-carriers, and the result remains significant after correcting for effects of brain size. Functional imaging analysis revealed that APOE ε4-carriers exhibited decreased amplitude of low-frequency fluctuations in the left hippocampus, non-significant changes in intra-regional synchronization within the hippocampus and decreased hippocampal functional connectivity predominantly in components of the default-mode network including the medial frontal and parietal cortices and the lateral temporal cortical regions. Taken together, our results showed APOE genotypic effects on the cognitive profile and hippocampal structural and functional characteristics in patients at early stages of AD, thus providing empirical evidence for the modulation of the APOE genotype on disease phenotype.
Hongkuan Yang, Hongpeng Guan, Mingchun Yang, Ziyi Liu, Shigeko Takeuchi, Daijiro Yanagisawa, Steven R. Vincent, Shiguang Zhao, Ikuo Tooyama (Handling Associate Editor: Thomas Beach)
Upregulation of Mitochondrial Ferritin by Proinflammatory Cytokines: Implications for a Role in Alzheimer’s Disease
Abstract: Studies have shown an increased expression of mitochondrial ferritin (FtMt) and an antioxidant role for the protein in the brains of Alzheimer’s disease (AD) patients. However, little information is available concerning the role of FtMt in other AD pathologies, including inflammation and amyloidogenesis. Therefore, we investigated the regulation and function of FtMt in inflammation and amyloidogenesis. FtMt protein expression was increased by proinflammatory cytokines, including tumor necrosis factor-α (TNF-α), interleukin-1β (IL-1β), and interleukin 6 (IL-6), whereas FtMt mRNA levels were increased by TNF-α but not by IL-1β or IL-6 in IMR-32 cells. The transcription factor nuclear factor-κB (NF-κB) inhibitor, Bay 11-7082, suppressed this TNF-α–induced FtMt expression. FtMt overexpression increased NF-κB activity and translocation of p65 into the nucleus in HEK293 cells. Conversely, knockdown of FtMt attenuated TNF-α–induced NF-κB activity. Overexpression of FtMt inhibited TNF-α-induced apoptosis in the cell culture. FtMt overexpression reduced iron-mediated expression of amyloid-β protein precursor and decreased NF-κB-dependent increases in β- and γ-secretase, leading to decreased amyloid-β production. Our data provide new insights into the mechanism underlying the regulation of FtMt expression by proinflammatory cytokines and indicate further roles for FtMt in AD.
Hanne Struyfs*, Bianca Van Broeck*, Maarten Timmers, Erik Fransen, Kristel Sleegers, Christine Van Broeckhoven, Peter P. De Deyn, Johannes R. Streffer, Marc Mercken, Sebastiaan Engelborghs (Handling Associate Editor: Piotr Lewczuk) *These authors contributed equally to this work.
Diagnostic Accuracy of Cerebrospinal Fluid Amyloid-β Isoforms for Early and Differential Dementia Diagnosis
Abstract: Background: Overlapping cerebrospinal fluid biomarkers (CSF) levels between Alzheimer’s disease (AD) and non-AD patients decrease differential diagnostic accuracy of the AD core cerebrospinal fluid (CSF) biomarkers. Amyloid-β (Aβ) isoforms might improve the AD versus non-AD differential diagnosis. Objective: To determine the added diagnostic value of Aβ isoforms, Aβ1-37, Aβ1-38, and Aβ1-40, as compared to the AD CSF biomarkers Aβ1-42, T-tau, and P-tau181P. Methods: CSF from patients with dementia due to AD (n=50), non-AD dementias (n=50), mild cognitive impairment due to AD (n=50) and non-demented controls (n=50) was analyzed with a prototype multiplex assay using MSD detection technology. The non-AD group consisted of frontotemporal dementia (FTD; n=17), dementia with Lewy bodies (DLB; n=17), and vascular dementia (n=16). Results: Aβ1-37 and Aβ1-38 increased accuracy to differentiate AD from FTD or DLB. Aβ1-37, Aβ1-38, and Aβ1-40 levels correlated with Mini-Mental State Examination scores and disease duration in dementia due to AD. The Aβ1-42/Aβ1-40 ratio improved diagnostic performance of Aβ1-42 in most differential diagnostic situations. Aβ1-42 levels were lower in APOE ε4 carriers compared to non-carriers. Conclusions: Aβ isoforms help to differentiate AD from FTD and DLB. Aβ isoforms increase diagnostic performance of Aβ1-42. In contrast to Aβ1-42, Aβ isoforms seem to be correlated with disease severity in AD. Adding the Aβ isoforms to the current biomarker panel could enhance diagnostic accuracy.
Andrea Špolcová, Barbora Mikulášková, Martina Holubová, Veronika Nagelová, Zdenko Pirnik, Jana Zemenová, Martin Haluzík, Blanka Železná, Marie-Christine Galas, Lenka Maletínská
Anorexigenic Lipopeptides Ameliorate Central Insulin Signaling and Attenuate Tau Phosphorylation in Hippocampi of Mice with Monosodium Glutamate-Induced Obesity
Abstract: Numerous epidemiological and experimental studies have demonstrated that patients who suffer from metabolic disorders, such as type 2 diabetes mellitus (T2DM) or obesity, have higher risks of cognitive dysfunction and of Alzheimer’s disease (AD). Impaired insulin signaling in the brain could contribute to the formation of neurofibrillary tangles, which contain an abnormally hyperphosphorylated tau protein. This study aimed to determine whether potential tau hyperphosphorylation could be detected in an obesity-induced pre-diabetes state and whether anorexigenic agents could affect this state. We demonstrated that 6-month-old mice with monosodium glutamate (MSG) obesity, which represent a model of obesity-induced pre-diabetes, had increased tau phosphorylation at Ser396 and Thr231 in the hippocampus compared with the controls, as determined by western blots. Two weeks of subcutaneous treatment with a lipidized analog of prolactin-releasing peptide (palm-PrRP31) or with the T2DM drug liraglutide, which both had a central anorexigenic effect, resulted in increased phosphorylation of the insulin cascade kinases PDK1 (Ser241), Akt (Thr308), and GSK-3β (Ser9). Furthermore, these drugs attenuated phosphorylation at Ser396, Thr231, and Thr212 of tau and of the primary tau kinases in the hippocampi of 6-month-old MSG-obese mice. We identified tau hyperphosphorylation in the obesity-induced pre-diabetes state in MSG-obese mice and demonstrated the beneficial effects of palm-PrRP31 and liraglutide, both of known central anorexigenic effects, on hippocampal insulin signaling and on tau phosphorylation.
Doo Young Lee*, Jangsup Moon*, Soon-Tae Lee*, Keun-Hwa Jung, Dong-Kyu Park, Jung-Seok Yoo, Jun-Sang Sunwoo, Jung-Ick Byun, Jung-Won Shin, Daejong Jeon, Ki-Young Jung, Manho Kim, Sang Kun Lee, Kon Chu (Handling Associate Editor: Inhee Mook-Jung) *These authors contributed equally to this work.
Distinct Expression of Long Non-Coding RNAs in an Alzheimer’s Disease Model
Abstract: With the recent advancement in transcriptome-wide profiling approach, numerous non-coding transcripts previously unknown have been identified. Among the non-coding transcripts, long non-coding RNAs (lncRNAs) have received increasing attention for their capacity to modulate transcriptional regulation. Although alterations in the expressions of non-coding RNAs have been studied in Alzheimer’s disease (AD), most research focused on the involvement of microRNAs, and comprehensive expression profiling of lncRNAs in AD has been lacking. In this study, microarray analysis was performed to procure the expression profile of lncRNAs dysregulated in a triple transgenic model of AD (3xTg-AD). A total of 4,622 lncRNAs were analyzed: 205 lncRNAs were significantly dysregulated in 3xTg-AD compared with control mice, and 230 lncRNAs were significantly dysregulated within 3xTg-AD in an age-dependent manner (≥2.0-fold, p<0.05). Among these, 27 and 15 lncRNAs, respectively, had adjacent protein-coding genes whose expressions were also significantly dysregulated. A majority of these lncRNAs and their adjacent genes shared the same direction of dysregulation. For these pairs of lncRNAs and adjacent genes, significant Gene Ontology terms were DNA-dependent regulation of transcription, transcription regulator activity, and embryonic organ morphogenesis. One of the most highly upregulated lncRNAs had a 395 bp core sequence that overlapped with multiple chromosomal regions. This is the first study that comprehensively identified dysregulated lncRNAs in 3xTg-AD mice and will likely facilitate the development of therapeutics targeting lncRNAs in AD.
Mizanur Khondoker, Stephen Newhouse, Eric Westman, J-Sebastian Muehlboeck, Patrizia Mecocci, Bruno Vellas, Magda Tsolaki, Iwona Kłoszewska, Hilkka Soininen, Simon Lovestone, Richard Dobson*, Andrew Simmons* for the AddNeuroMed consortium and for the Alzheimer’s Disease Neuroimaging Initiative (Handling Associate Editor: Tânia C. T. Ferraz Alves) *Joint last authors.
Linking Genetics of Brain Changes to Alzheimer’s Disease: Sparse Whole Genome Association Scan of Regional MRI Volumes in the ADNI and AddNeuroMed Cohorts
Abstract: Background: Alzheimer’s disease (AD) is a highly heritable disease, but until recently few replicated genetic markers have been identified. Markers identified so far are likely to account for only a tiny fraction of the heritability of AD and many more genetic risk alleles are thought to be undiscovered. Objective: Identifying genetic markers for AD using combined analysis of genetics and brain imaging data. Methods: Imaging quantitative trait loci (iQTLs) has recently emerged as an interesting research area for linking genetics of brain changes to AD. We consider a genome-wide association scan of 109 brain-wide regional imaging phenotypes to identify genetic susceptibility loci for AD from a combined set of 1,045 subjects from the Alzheimer’s Disease Neuroimaging Initiative (ADNI) and the AddNeuroMed studies. We use one-SNP-at-a-time as well as multi-SNP Hyperlasso based iQTL methods for the analysis. Results: We identified several novel markers associated with AD, namely HOMER2 (rs1256429; intronic, p = 8.7×10−10), EOMES (rs2724509; flanking), JAM2 (rs2829841; intronic), and WEE1 (rs10770042; coding). The SNP rs1256429 (HOMER2) was one of the top hits in Hyperlasso as well as in the single-SNP analysis showing an association with the volume of the right thalamus and AD, a brain region reported to be linked with AD in several studies. Conclusion: We believe that the markers identified in this study are novel additions to the existing list of genetic variants associated with AD which can be validated in future replicated studies.
Rivka Inzelberg, Magda Massarwa, Edna Schechtman, Rosa Strugatsky, Lindsay A. Farrer, Robert P. Friedland
Estimating the Risk for Conversion from Mild Cognitive Impairment to Alzheimer's Disease in an Elderly Arab Community
Abstract: Background: Vascular risk factors and lack of formal education may increase the risk of Alzheimer's disease (AD). Objective: To determine the contribution of vascular risk factors and education to the risk of mild cognitive impairment (MCI) and AD and to estimate the risk for conversion from MCI to AD. Methods: This door-to-door survey was performed by an Arab-speaking team in Wadi Ara villages in Israel. All consenting residents aged ≥ 65 years were interviewed for medical history and underwent neurological and cognitive examinations. Individuals were cognitively classified as normal (CN), MCI, AD, vascular dementia, or unclassifiable. MCI patients were re-examined at least one year later to determine conversion to AD. The contributions of age, gender, school years, and vascular risk factors to the probability of conversion were estimated using logistic regression models. Results: Of the 906 participants, 297 (33%) had MCI and 95 (10%) had AD. Older age (p=0.0008), female gender (p=0.023), low schooling (p<0.0001), and hypertension (p=0.0002) significantly accounted for risk of MCI versus CN, and diabetes was borderline (p=0.051). The risk of AD versus CN was significantly associated with age (p<0.0001), female gender (p<0.0001), low schooling (p=0.004) and hypertension (p=0.049). Of the 231 subjects with MCI that were re-examined, 65 converted to AD. Conclusions: In this population, age, female gender, lack of formal education, and hypertension are risk factors for both AD and MCI. Conversion risk from MCI to AD could be estimated as a function of age, time interval between examinations, and hypertension.
Sindre Rolstad, Anne Ingeborg Berg, Carl Eckerström, Boo Johansson, Anders Wallin
Differential Impact of Neurofilament Light Subunit on Cognition and Functional Outcome in Memory Clinic Patients with and without Vascular Burden
Abstract: The neurofilament light (NF-L) subunit is mainly expressed in large-caliber myelinated axons, and elevated concentrations in the cerebrospinal fluid (CSF) are correlated with damage to white matter and subcortical regions. Because the correlation between NF-L and cognition and functional impairment is largely unknown, we investigated associations in patients (n = 622) with (n = 199) and without (n = 423) vascular burden in subjective cognitive impairment (SCI, n = 168), mild cognitive impairment (MCI, n = 261), and dementia (n = 193). Patients were staged according to disease severity and the presence/absence of cerebrovascular disease. CSF amyloid-β1-42 (Aβ1-42) was included in all models due to its concomitant influence on vascular and primary etiology. Linear regression was used to assess associations between NF-L and Aβ1-42 and five cognitive domains of a comprehensive neuropsychological battery as well as with functional impairment using the Clinical Dementia Rating. Changes in these outcomes at the 2-year follow-up were also evaluated. In SCI and MCI patients with vascular burden, higher NF-L concentrations were associated with baseline cognitive performance (β = −0.38 to −0.58) and executive decline (β = −0.44). Lower Aβ1-42 levels were associated with worse cognitive performance in dementia (β = 0.46 to 0.51). In MCI and dementia patients without vascular burden, higher NF-L (β = −0.30 to −0.34) and lower Aβ1-42 concentrations (β = 0.30) were associated with reduced cognitive performance. Higher NF-L concentrations (β = −0.26) were associated with functional decline in patients with vascular burden. CSF NF-L is associated with cognition in patients with and without vascular etiology. These associations were greater in pre-dementia phases in those with vascular etiology and vice versa in those without vascular burden.
Laura Buratti, Simona Balestrini, Claudia Altamura, Giovanna Viticchi, Lorenzo Falsetti, Simona Luzzi, Leandro Provinciali, Fabrizio Vernieri, Mauro Silvestrini (Handling Associate Editor: Jack de la Torre)
Markers for the Risk of Progression from Mild Cognitive Impairment to Alzheimer’s Disease
Abstract: Background: Defining reliable markers of conversion to dementia could be the first step in order to identify appropriate treatment strategies for mild cognitive impairment (MCI) patients. Objective: To develop a tool able to predict the risk of progression from MCI to Alzheimer’s disease (AD). Methods: 406 MCI patients were included and followed for a one-year period. Demographic characteristics, vascular risk factors, extent of cerebrovascular lesions, markers of carotid atherosclerosis investigated with an ultrasonographic assessment (plaque index and intima-media thickness) and cerebrovascular reactivity to apnea (breath-holding index) were considered as potential predictors of conversion. Results: 106 (26%) MCI patients showed a conversion to AD. Plaque index, intima-media thickness, and breath-holding index were relevant predictors of conversion (p=0.042; p=0.003; p<0.001, multivariate logistic regression analysis). A simplified scoring system was devised based on the magnitude of the estimated multinomial logistic regression β coefficient results. A total score was calculated as the sum of each predictive factor which resulted in a 0-5 range. The optimal cut-off score was ≥3 (sensitivity, 23.6%, 95%CI 15.9%-32.8%; specificity, 97.7%, 95% CI 95.3%-99.1%; positive likelihood ratio, 10.1, 95%CI 4.5%-22.7%; negative likelihood ratio, 0.78, 95%CI 0.70%-0.87%). The AUC was 0.71 (95%CI, 0.65-0.77). Conclusions: Our findings show the possibility to obtain a predictive indicator of the risk of conversion from MCI to dementia by considering the presence of both atherosclerotic changes in the carotid district and impairment of cerebral hemodynamics. Such an approach may allow us to formulate a correct prognosis in more than 70% of patients with amnesic MCI.
Jonathon Hull, Vinood Patel, Maya El Hindy, Christopher Lee, Esther Odeleye, Mohammed Hezwani, Seth Love, Patrick Kehoe, Katy Chalmers, Myra Conway
Regional Increase in the Expression of the BCAT Proteins in Alzheimer’s Disease Brain: Implications in Glutamate Toxicity
Abstract: Background: The human branched chain aminotransferases (hBCATm, mitochondrial and hBCATc, cytosolic) are major contributors to brain glutamate production. This excitatory neurotransmitter is thought to contribute to neurotoxicity in neurodegenerative conditions such as Alzheimer’s disease (AD) but the expression of hBCAT in this disease has not previously been investigated. Objective: The objective of investigating hBCAT expression is to gain insight into potential metabolic pathways that may be dysregulated in AD brain, which would contribute to glutamate toxicity. Methods: Western blot analysis and immunohistochemistry were used to determine the expression and localization of hBCAT in postmortem frontal and temporal cortex from AD and matched control brains. Results: Western blot analysis demonstrated a significant regional increase in hBCATc expression in the hippocampus (↑ 36%; p-values of 0.012), with an increase of ↑ 160% reported for hBCATm in the frontal and temporal cortex (p-values=4.22x10-4 and 2.79x10-5, respectively) in AD relative to matched controls, with evidence of post-translational modifications to hBCATm, more prominent in AD samples. Using immunohistochemistry, a significant increase in immunopositive labelling of hBCATc was observed in the CA1 and CA4 region of the hippocampus (p-values=0.011 and 0.026, respectively) correlating with western blot analysis. Moreover, the level of hBCATm in the frontal and temporal cortex correlated significantly with disease severity, as indicated by Braak staging (p-values=5.63x10-6 and 9.29x10-5, respectively). Conclusion: The expression of the hBCAT proteins is significantly elevated in AD brain. This may modulate glutamate production and toxicity, and thereby play a role in the pathogenesis of the disease.
Jun Ku Chung, Eric Plitman, Shinichiro Nakajima, Tiffany W. Chow, M. Mallar Chakravarty, Fernando Carravagio, Philip Gerretsen, Eric E. Brown, Yusuke Iwata, Benoit H. Mulsant, Ariel Graff-Guerrero, for the Alzheimer’s Disease Neuroimaging Initiative
Lifetime History of Depression Predicts Increased Amyloid-β Accumulation in Patients with Mild Cognitive Impairment
Abstract: Mounting evidence associates a lifetime history of major depression (LMD) with an increased risk for Alzheimer’s disease (AD). Studies have shown that major depression (MD) is strongly linked to pathophysiological markers of AD, such as cortical amyloid-β (Aβ) burden. However, no imaging studies have shown in vivo whether an LMD is linked to increased Aβ accumulation in patients with mild cognitive impairment (MCI) in four cortical regions that have been highly associated with increased Aβ deposition in previous literature: frontal, cingulate, parietal, and temporal. Drawing from the ADNI database, we found that patients with amnestic MCI (aMCI) and an LMD (n = 39) had significantly higher 18F-Florbetapir standardized uptake value ratios, a surrogate measure of Aβ deposition, mainly in the bilateral frontal cortex, compared to patients with aMCI without an LMD (n = 39) (p = 0.02). This difference was not explained by current depressive symptoms, vascular risk factors, or the use of different PET scanners. The results were reliable employing two independent methods for analysis: region-of-interest and voxel-based analyses. Increased Aβ in the bilateral frontal lobes may be a biomarker of depressive symptomology in aMCI patients. Further studies should test whether higher Aβ predicts future conversion into AD in this population.
Sahar Elahi, Alvin H. Bachman, Sang Han Lee, John J. Sidtis, Babak A. Ardekani, for the Alzheimer’s Disease Neuroimaging Initiative (Handling Associate Editor: Stefan Teipel)
Corpus Callosum Atrophy Rate in Mild Cognitive Impairment and Prodromal Alzheimer’s Disease
Abstract: Background: Corpus callosum (CC) size and shape have been previously studied in Alzheimer’s disease (AD) with the majority of studies having been cross-sectional. Due to the large variance in normal CC morphology, cross-sectional studies are limited in statistical power. Determining individual rates of change requires longitudinal data. Physiological changes are particularly relevant in mild cognitive impairment (MCI), in which CC morphology has not been previously studied longitudinally. Objective: To study temporal rates of change in CC morphology in MCI patients over a one-year period, and to determine whether these rates differ between MCI subjects who converted to AD (MCI-C) and those who did not (MCI-NC) over an average (±SD) observation period of 5.4 (±1.6) years. Methods: We used a novel multi-atlas based algorithm to segment the mid-sagittal cross-sectional area of the CC in longitudinal MRI scans. Rates of change of CC circularity, total area, and five sub-areas were compared between 57 MCI-NC and 81 MCI-C subjects. Results: The CC became less circular (-0.89% per year in MCI-NC, -1.85% per year in MCI-C) with time, with faster decline in MCI-C (p=0.0002). In females, atrophy rates were higher in MCI-C relative to MCI-NC in total CC area (p=0.0006), genu/rostrum (p=0.005), and splenium (0.002). In males, these rates did not differ between groups. Conclusion: A greater than normal decline in CC circularity was shown to be an indicator of prodromal AD in MCI subjects. This measure is potentially useful as an imaging biomarker of disease and a therapeutic target in clinical trials.
Nora E. Gray, Harini Sampath, Jonathan A. Zweig, Joseph F. Quinn, Amala Soumyanath
Centella asiatica Attenuates Amyloid-β-Induced Oxidative Stress and Mitochondrial Dysfunction
Abstract: Background: We previously showed that a water extract of the medicinal plant Centella asiatica (CAW) attenuates amyloid-β (Aβ)-induced cognitive deficits in vivo, and prevents Aβ-induced cytotoxicity in vitro. Yet the neuroprotective mechanism of CAW is unknown. Objective: The goal of this study was to identify biochemical pathways altered by CAW using in vitro models of Aβ toxicity. Methods: The effects of CAW on aberrations in antioxidant response, calcium homeostasis, and mitochondrial function induced by Aβ were evaluated in MC65 and SH-SY5Y neuroblastoma cells. Results: CAW decreased intracellular reactive oxygen species and calcium levels elevated in response to Aβ, and induced the expression of antioxidant response genes in both cell lines. In SH-SY5Y cells, CAW increased basal and maximal oxygen consumption without altering spare capacity, and attenuated Aβ-induced decreases in mitochondrial respiration. CAW also prevented Aβ-induced decreases in ATP and induced the expression of mitochondrial genes and proteins in both cell types. Caffeoylquinic acids from CAW were shown to have a similar effect on antioxidant and mitochondrial gene expression in neuroblastoma cells. Primary rat hippocampal neurons treated with CAW also showed an increase in mitochondrial and antioxidant gene expression. Conclusions: These data suggest an effect of CAW on mitochondrial biogenesis, which in conjunction with activation of antioxidant response genes and normalizing calcium homeostasis, likely contributes to its neuroprotective action against Aβ toxicity.
Megha M. Vasavada, Jianli Wang, Paul J. Eslinger, David J. Gill, Xiaoyu Sun, Prasanna Karunanayaka, Qing X. Yang (Handling Associate Editor: Kuncheng Li)
Olfactory Cortex Degeneration in Alzheimer’s Disease and Mild Cognitive Impairment
Abstract: Background: Olfactory deficits are prevalent in patients with Alzheimer’s disease (AD) and mild cognitive impairment (MCI). These symptoms precede clinical onset of cognitive and memory deficits and coincide with AD pathology preferentially in the central olfactory structures, suggesting a potential biomarker for AD early detection and progression. Objective: Therefore, we tested the hypothesis that structural degeneration of the primary olfactory cortex (POC) could be detected in AD as well as in MCI patients and would be correlated with olfactory functional magnetic resonance imaging (fMRI) alterations, reflecting loss of olfactory cortex activity. Methods: Total structural volumes and fMRI activation volumes of the POC and hippocampus were measured along with olfactory and cognitive behavioral tests in 27 cognitively normal (CN), 21 MCI, and 15 AD subjects. Results: Prominent atrophy in the POC and hippocampus was found in both AD and MCI subjects and correlated with behavioral measurements. While behavioral and volumetric measurements showed a gradual decline from CN to MCI to AD, olfactory activation volume in the POC and hippocampus showed a steeper decline in the MCI group compared to corresponding tissue volume, resembling the AD group. Conclusions: Decline in olfactory activity was correlated with the AD structural degeneration in the POC. A more prominent olfactory activity deficit than that of behavioral and tissue volume measurements was shown in the MCI stage. Olfactory fMRI may thus provide an earlier and more sensitive measure of functional neurodegeneration in AD and MCI patients.
Visar Berisha, Shuai Wang, Amy LaCross, Julie Liss
Tracking Discourse Complexity Preceding Alzheimer’s Disease Diagnosis: A Case Study Comparing the Press Conferences of Presidents Ronald Reagan and George Herbert Walker Bush
Abstract: Changes in some lexical features of language have been associated with the onset and progression of Alzheimer’s disease. Here we describe a method to extract key features from discourse transcripts, which we evaluated on non-scripted news conferences from President Ronald Reagan, who was diagnosed with Alzheimer's disease in 1994, and President George Herbert Walker Bush, who has no known diagnosis of Alzheimer’s disease. Key word counts previously associated with cognitive decline in Alzheimer’s disease were extracted and regression analyses were conducted. President Reagan showed a significant reduction in the number of unique words over time and a significant increase in conversational fillers and non-specific nouns over time. There was no significant trend in these features for President Bush.
Lorena Perrone, William B. Grant
Observational and Ecological Studies of Dietary Advanced Glycation End Products in National Diets and Alzheimer’s Disease Incidence and Prevalence
Abstract: Background. Considerable evidence indicates that diet is an important risk-modifying factor for Alzheimer’s disease (AD). Evidence is also mounting that dietary advanced glycation end products (AGEs) are important risk factors for AD. Objective. This study strives to determine whether estimated dietary AGEs estimated from national diets and epidemiological studies are associated with increased AD incidence. Methods. We estimated values of dietary AGEs using values in a published paper. We estimated intake of dietary AGEs from the Washington Heights-Inwood Community Aging Project (WHICAP) 1992 and 1999 cohort studies, which investigated how the Mediterranean diet (MeDi) affected AD incidence. Further, AD prevalence data came from three ecological studies and included data from 11 countries for 1977–1993, seven developing countries for 1995–2005, and Japan for 1985–2008. The analysis used dietary AGE values from 20 years before the AD prevalence data. Results. Meat was always the food with the largest amount of AGEs. Other foods with significant AGEs included fish, cheese, vegetables, and vegetable oil. High MeDi adherence results in lower meat and dairy intake, which possess high AGE content. By using two different models to extrapolate dietary AGE intake in the WHICAP 1992 and 1999 cohort studies, we showed that reduced dietary AGE significantly correlates with reduced AD incidence. For the ecological studies, estimates of dietary AGEs in the national diets corresponded well with AD prevalence data even though the cooking methods were not well known. Conclusion. Dietary AGEs appear to be important risk factors for AD.