34, Number 4, March 2013
Nadja Schröder, Luciana Silva Figueiredo, Maria Noêmia Martins de Lima
Role of Brain Iron Accumulation in Cognitive Dysfunction: Evidence from Animal Models and Human Studies
Abstract: Over the last decades, studies from our laboratory and other groups using animal models have shown that iron overload, resulting in iron accumulation in the brain, produces significant cognitive deficits. Iron accumulation in the hippocampus and the basal ganglia has been related to impairments in spatial memory, aversive memory, and recognition memory in rodents. These results are corroborated by studies showing that the administration of iron chelators attenuates cognitive deficits in a variety of animal models of cognitive dysfunction, including aging and Alzheimer’s disease models. Remarkably, recent human studies using magnetic resonance image techniques have also shown a consistent correlation between cognitive dysfunction and iron deposition, mostly in the hippocampus, cortical areas, and basal ganglia in humans. These findings may have relevant implications in the light of the knowledge that iron accumulates in brain regions of patients suffering from neurodegenerative diseases. A better understanding of the functional consequences of iron dysregulation in aging and neurological diseases may help to identify novel targets for treating memory problems that afflict a growing aging population.
Elke Kalbe, Pasquale Calabrese, Sophie Fengler, Josef Kessler (Handling Associate Editor: Piotr Lewczuk)
DemTect, PANDA, EASY, and MUSIC: Cognitive Screening Tools with Age Correction and Weighting of Subtests according to their Sensitivity and Specificity
Abstract: Many cognitive screening instruments have been developed during the last decades to detect mild cognitive dysfunction and dementia, and there is an ongoing discussion as to which tool should be used in which setting and which challenges have to be considered. Among other aspects, dependence on age is a recognized problem in screening tools which still has not found its way into common scoring procedures. Another aspect which has been handled very heterogeneously is which domain is represented in which proportion in the total score. Furthermore, screening ethnic minority patients has been identified as an important but so far widely unresolved matter. In this review, four cognitive screening tools that all follow a common, stringent concept and pay regard to some critical aspects are described: the DemTect, a “generic” tool; the PANDA for Parkinson’s disease patients; the EASY, a non-verbal, culture-fair screening test for patients with migration background; and the MUSIC for patients with multiple sclerosis. All of these screening instruments have an age-correction, provide a total score in which the different subtests are weighted according to their individual sensitivity and specificity, and include tasks that are specifically aligned to the cognitive profile of the target group, including the EASY with non-verbal, culture-fair tasks to overcome language and cultural barriers. The development, main characteristics, data, and limitations of these tools are presented and discussed against the background of the current landscape of cognitive screening tools.
María Izco, Pedro Pesini, Virginia Pérez-Grijalba, Noelia Fandos, Manuel Sarasa
Optimized Protocol for Amyloid-β Extraction from the Brain
Abstract: Brain levels of amyloid-β (Aβ) are frequently assessed in transgenic mice models of Alzheimer’s disease. The procedure involves tissue sample homogenization using different buffers in a sequential process. No attempt has been made to assess if these procedures are able to extract the total amount of Aβ present in the samples. Here we present data suggesting that standard protocols can lead to a dramatic underestimation of the Aβ content. Results show that higher extraction buffer volumes and at least two repetitions of the soluble and membrane-bound extraction steps are necessary for a more accurate estimation of the Aβ content in brain tissues.
Sid E. O’Bryant, Guanghua Xiao, Melissa Edwards, Michael Devous, Veer Bala Gupta, Ralph Martins, Fan Zhang, Robert Barber, for the Texas Alzheimer’s Research and Care Consortium (TARCC)
Biomarkers of Alzheimer’s Disease Among Mexican Americans
Abstract: Background: Mexican Americans are the fastest aging segment of the U.S. population, yet little scientific literature exists regarding the Alzheimer’s disease (AD) among this segment of the population. The extant literature suggests that biomarkers of AD will vary according to race/ethnicity though no prior work has explicitly studied this possibility. The aim of this study was to create a serum-based biomarker profile of AD among Mexican American. Methods: Data were analyzed from 363 Mexican American participants (49 AD and 314 normal controls) enrolled in the Texas Alzheimer’s Research & Care Consortium (TARCC). Non-fasting serum samples were analyzed using a luminex-based multi-plex platform. A biomarker profile was generated using random forest analyses. Results: The biomarker profile of AD among Mexican Americans was different from prior work from non-Hispanic populations with regards to the variable importance plots. In fact, many of the top markers were related to metabolic factors (e.g., FABP, GLP-1, CD40, pancreatic polypeptide, insulin-like-growth factor, and insulin). The biomarker profile was a significant classifier of AD status yielding an area under the receiver operating characteristic curve, sensitivity, and specificity of 0.77, 0.92, and 0.64, respectively. Combining biomarkers with clinical variables yielded a better balance of sensitivity and specificity. Conclusion: The biomarker profile for AD among Mexican American cases is significantly different from that previously identified among non-Hispanic cases from many large-scale studies. This is the first study to explicitly examine and provide support for blood-based biomarkers of AD among Mexican Americans. Areas for future research are highlighted.
Laura B. Zahodne, Devangere Devanand, Yaakov Stern (Handling Associate Editor: Josep Garre-Olmo)
Coupled Cognitive and Functional Change in Alzheimer’s Disease and the Influence of Depressive Symptoms
Abstract: In Alzheimer’s disease (AD), cognition and function are only moderately correlated in cross-sectional studies, and studies of their longitudinal association are less common. One potential non-cognitive contributor to function is depression, which has been associated with poorer clinical outcomes. The current study investigated longitudinal associations between functional abilities, cognitive status, and depressive symptoms in AD. 517 patients diagnosed with probable AD and enrolled in The Multicenter Study of Predictors of Disease Course in Alzheimer’s Disease were included. Patients were followed at 6-month intervals over 5.5 years. Longitudinal changes in the Blessed Dementia Rating Scale, modified Mini-Mental State Exam, and the depression subscale of the Columbia University Scale for Psychopathology in AD were examined in a multivariate latent growth curve model that controlled for gender, age, education, and recruitment site. Results showed that cognition and function worsened over the study period, whereas depressive symptoms were largely stable. Rates of change in cognition and function were correlated across participants and coupled within participants, indicating that they travel together over time. Worse initial cognitive status was associated with faster subsequent functional decline, and vice versa. Higher level of depressive symptoms was associated with worse initial functioning and faster subsequent cognitive and functional decline. These findings highlight the importance of both cognitive and psychiatric assessment for functional prognosis. Targeting both cognitive and depressive symptoms in the clinical treatment of AD may have incremental benefit on functional abilities.
Kathryn A. Ellis, Yen Ying Lim, Karra Harrington, David Ames, Ashley I. Bush, David Darby, Ralph N. Martins, Colin L. Masters, Christopher C. Rowe, Greg Savage, Cassandra Szoeke, Victor L. Villemagne, Paul Maruff, for the AIBL Research Group
Decline in Cognitive Function over 18 Months in Healthy Older Adults with High Amyloid-β
Abstract: We aimed to characterize the nature and magnitude of cognitive decline in a group of healthy older adults with high and low levels of amyloid-β (Aβ) and who were APOE ε4 carriers and non-carriers. Healthy older adults underwent positron emission tomography neuroimaging for Aβ, APOE genotyping, and cognitive and clinical assessment as part of their baseline assessment in the Australian Imaging, Biomarker, and Lifestyle study. Cognitive function and clinical ratings were reassessed 18 months later. Linear mixed model analyses adjusted for baseline cognitive function indicated that relative to healthy older adults with low Aβ, healthy older adults with high Aβ showed greater decline in episodic memory and language at 18 months. No decline on any measure of executive function, attention, or clinical rating was observed for healthy older adults with high Aβ levels. Compared to non-carriers, APOE ε4 carriers showed a greater decline only on the task of visual memory at the 18 month assessment. Importantly though, no interaction between APOE ε4 and Aβ was observed on any measure of cognitive function. The results of this study suggest that high Aβ load was associated with greater decline in episodic memory and language, that the magnitude of this decline was moderate and equivalent across both domains, and that APOE ε4 carriage did not moderate the relationship between Aβ and decline in memory and language functions.
Ana C. Abbott, Carla Calderon Toledo, Florencia C. Aranguiz, Nibaldo C. Inestrosa, Lorena Varela-Nallar
Tetrahydrohyperforin Increases Adult Hippocampal Neurogenesis in Wild-Type and APPswe/PS1ΔE9 Mice
Abstract: Tetrahydrohyperforin (IDN5706), a semi-synthetic derivative of hyperforin, has shown neuroprotective properties preventing the impairment of synaptic plasticity and cognitive decline in an in vivo model of Alzheimer’s disease (AD). Considering the reported role of adult neurogenesis in the plasticity of the hippocampal network, we investigated whether IDN5706 affects adult neurogenesis and hippocampal function. In hippocampal progenitors cultured from adult rats, IDN5706 increased proliferation. Moreover, treatment with IDN5706 for 4 weeks increased cell proliferation in the subgranular zone (SGZ) of the hippocampus in 2 month-old wild-type mice in vivo. As determined by double labeling with BrdU and neuronal markers, IDN5706 treatment increased the number of immature neurons and newborn mature neurons in the adult dentate gyrus. In addition, IDN5706 treatment improved long‐term memory in a hippocampal‐dependent spatial memory task. Finally, IDN5706 treatment increased cell proliferation and neural commitment in the SGZ of the double transgenic APPswe/PS1ΔE9 mouse model of AD. These results indicate that IDN5706 increases adult hippocampal neurogenesis and may have therapeutic value in neurological disorders in which adult neurogenesis is impaired.
Supplementary Data for Abbott et al. article (PDF)
Marta Balietti, Belinda Giorgetti, Tiziana Casoli, Moreno Solazzi, Francesco Tamagnini, Costanza Burattini, Giorgio Aicardi, Patrizia Fattoretti (Handling Associate Editor: ShiDu Yan)
Early Selective Vulnerability of Synapses and Synaptic Mitochondria in the Hippocampal CA1 Region of the Tg2576 Mouse Model of Alzheimer’s Disease
Abstract: Increasing experimental evidence indicates that synaptic alterations play a key role in cognitive decline in Alzheimer’s disease (AD). Functional and structural synaptic changes progressively take place, beginning in the early phase of AD, mainly triggered by intracellular accumulation of soluble amyloid-β (Aβ) oligomers. These peptides also accumulate within mitochondria, heavily affecting their function and morphology, particularly in synaptic compartments. To better understand the role of mitochondrial impairment in synaptic alterations during the early stages of AD, a morphological investigation was performed by means of electron microscopy in the hippocampus of 3 month-old Tg2576 and transgene-negative littermate mice. In the stratum moleculare of CA1 pyramidal cells (SMCA1) of transgenic animals compared to controls, we found significantly larger and less numerous synapses, with a significantly reduced fraction of the perforated subtype, as well as significantly smaller and more numerous mitochondria. In contrast, no differences between the two groups of mice were found in the inner molecular layer of the dentate gyrus. The reduction of synaptic contacts in SMCA1 indicates a precocious vulnerability of this region, and the synaptic enlargement may reflect a compensating process aimed at maintaining the overall contact density. Accordingly, mitochondrial modifications may represent a plastic reactive phenomenon aimed at sustaining the increased energy needs for synaptic remodeling, since mitochondrial morphology was perfectly preserved and smaller mitochondria are metabolically more efficient. Thus, morphological changes occurring at synaptic level in SMCA1 of 3 month-old Tg2576 mice might reflect a precocious vulnerability associated with a residual plastic reactivity which may slow down functional alterations.
D. Richard Lachno, Barbara A Evert, Hugo Vanderstichele, Michael Robertson, Ronald B. DeMattos, Robert J. Konrad, Jayne A. Talbot, Margaret M. Racke, Robert A. Dean
Validation of Assays for Measurement of Amyloid-β Peptides in Cerebrospinal Flui and Plasma Specimens from Patients with Alzheimer’s Disease Treated with Solanezumab
Abstract: The aim of this study was to validate new assays for measurement of amyloid-β (Aβ) peptides in cerebrospinal fluid (CSF) and plasma specimens in clinical studies of solanezumab according to current regulatory recommendations. Four assays based on the INNOTEST® β-AMYLOID(1-42) and prototype INNOTEST β-AMYLOID(1-40) kits were developed and validated. To render these assays ‘solanezumab-tolerant’, excess drug was added to calibrators, quality control, and test samples via a 2-fold dilution with kit diluent. Validation parameters were evaluated by repeated testing of human CSF and EDTA-plasma pools containing solanezumab. Calibration curve correlation coefficients for the four assays were ≥0.9985. Intra- and inter-assay coefficients of variation for Aβ1-40 and Aβ1-42 were ≤13% and ≤15%, respectively for both matrices. Dilutional linearity, within and between assays, was demonstrated for both analytes in CSF and plasma at clinically relevant dilution factors. This dilution regimen was successfully applied during Phase 3 clinical sample analysis. Aβ1-40 and Aβ1-42 were stable in CSF and plasma containing solanezumab at 2–8°C and room temperature for up to 8 h and during 5 additional freeze-thaw cycles from ≤−20°C and ≤−70°C. Results of parallel tests on stored clinical samples using INNOTEST methods and proprietary ELISA methods were closely correlated (r2>0.9), although bias in reported concentrations was observed between assays. In conclusion, the modified INNOTEST assays provided (relatively) accurate and precise quantification of Aβ1-40 and Aβ1-42 in CSF and plasma containing solanezumab according to established consensus validation criteria. The clinical experience with these assays post validation has shown them to be robust and reliable.
Supplementary Data for Lachno et al. article (PDF)
Pedro Carmona, Marina Molina, Miguel Calero, Félix Bermejo-Pareja, Pablo Martínez-Martín, Adolfo Toledano (Handling Associate Editor: Miglena Angelova)
Discrimination Analysis of Blood Plasma Associated with Alzheimer’s Disease Using Vibrational Spectroscopy
Abstract: In this study we have determined whether Raman and infrared spectroscopy of blood plasma differentiates Alzheimer’s disease (AD) from normal aging of healthy controls. Spectroscopic analysis was conducted on blood plasma samples from 8 mild AD, 16 moderate AD, 11 severe AD, and 12 normal elderly control persons using Fourier transform spectrometers and a near-infrared laser beam as excitation source for Raman spectroscopy. Spectra were processed employing discriminant analysis to determine whether band areas and frequency-intensity relationships might reveal biochemical differences associated with AD. Seven spectral biomarkers were identified in the Raman regions of 1700-1600 cm-1 (protein secondary structure), 980-910 cm-1 (protein α-helices), 790-730 cm-1 (protein tertiary structure), and 440-390 cm-1 (protein backbone) and in the infrared regions of 1700-1600 cm-1 (protein secondary structure) and 1150-1000 cm-1 (oxidative stress). This discriminant analysis model differentiated AD from normal aging of elderly control persons with a sensitivity of 89% and specificity of 92%. Moreover, specificity increases to 100% for the detection of mild AD. In summary, our results open the possibility of using this spectroscopic approach as a non-invasive, rapid, and relatively inexpensive procedure for early accurate diagnosis of AD.
Supplementary Data for Carmona et al. article (PDF)
Christina E. Wierenga, Lindsay R. Clark, Sheena I. Dev, David D. Shin, Sarah M. Jurick, Robert A. Rissman, Thomas T. Liu, Mark W. Bondi
Interaction of Age and APOE Genotype on Cerebral Blood Flow at Rest
Abstract: We investigated the impact of APOE genotype on cerebral blood flow (CBF) in older and younger adults. Forty cognitively normal older adults (16 ε4 carriers, 24 non-ε4 carriers) and 30 younger adults (15 ε4 carriers, 15 non-ε4 carriers) completed a resting-state whole-brain pulsed arterial spin labeling magnetic resonance scan. Main effects of aging were demonstrated wherein older adults had decreased gray matter CBF corrected for partial volume effects compared to younger adults in widespread brain regions. Main effects of APOE genotype were also observed wherein ε4 carriers displayed greater CBF in the left lingual gyrus and precuneus than non-carriers. An interaction between age and APOE genotype in the left anterior cingulate cortex (ACC) was characterized by reduced CBF in older ε4 carriers and increased CBF in young ε4 carriers. Increased CBF in the left ACC resulting from the interaction of age group and APOE genotype was positively correlated with executive functioning in young ε4 adults (r = 0.61, p = 0.04). Results demonstrate APOE genotype differentially impacts cerebrovascular function across the lifespan and may modify the relationship between CBF and cognition. Findings may partially support suggestions that the gene exerts antagonistic pleiotropic effects.
Yanping Zhou, Yi Luo, Jiapei Dai
Axonal and Dendritic Changes are associated with Diabetic Encephalopathy in Rats: An Important Risk Factor for Alzheimer’s Disease
Abstract: Axonopathy is closely linked to and promotes diabetic peripheral neuropathy and a subset of neurological diseases including Alzheimer’s disease (AD), but its involvement in the development of diabetic encephalopathy remains unknown. In the present study, we aimed to ascertain the role of axonopathy in the development of diabetic encephalopathy and the possible relationship between diabetic encephalopathy and AD. The streptozotocin (STZ)-induced diabetic rat model was used. A Y-maze task, in vivo neuronal tracing, immunohistochemistry, and western blot analysis were performed to evaluate the cognitive functions, axonal and dendritic changes, and the expressions of amyloid-β (Aβ) and hyperphosphorylated tau in relation to the development of diabetic encephalopathy in this diabetic model. Coincident with significant memory impairment, the diabetic rats showed obvious axonal and dendritic changes, termed axonopathy and dendropathy, respectively, which mainly manifested as the swelling of axons, varicosities, and dendrites in the cognitive-associated brain regions compared to the non-diabetic animals. The site-specific hyperphosphorylated tau, but not deposits of Aβ, was detected in the diabetic rat brains. These data reveal a key role of axonopathy and dendropathy accompanied with the site-specific hyperphosphorylated tau in the course of diabetic encephalopathy, which may be the early link to the neuropathological processes of AD.
Sindre Rolstad, Anne Ingeborg Berg, Maria Bjerke, Boo Johansson, Henrik Zetterberg, Anders Wallin (Handling Associate Editor: Natalie Grima)
Cerebrospinal Fluid Biomarkers Mirror Rate of Cognitive Decline
Abstract: The ability to predict future decline in cognitive systems using the cerebrospinal fluid (CSF) biomarkers 42 amino acid form of amyloid-β (Aβ42) and total tau (T-tau) is not fully understood. In a clinical sample ranging from cognitively healthy to dementia (m = 326), linear regression models were performed in order to investigate the ability of CSF biomarkers to predict cognitive decline in all cognitive domains from baseline to 2-year follow-up. Gender, age, and years of education were included as covariates. In patients with subjective cognitive impairment, T-tau had a small impact on executive functions (r2=0.07). T-tau had a small to moderate influence (r2=0.06–0.11) on all cognitive functions with the exception of visuospatial functions in patients with mild cognitive impairment (MCI). In patients with dementia, the impact of T-tau was large (r2=0.29) on semantic memory. Aβ42 had a small effect (r2=0.07) on speed and executive functions in MCI. In patients with dementia, Aβ42 had a moderate influence (r2=0.13–0.24) on semantic and verbal working memory/fluency. Our results speak in favor of the notion that CSF biomarkers reflect the rate of cognitive decline across the continuum of cognitive impairment from healthy to dementia. CSF predicted subsequent decline in more cognitive domains among MCI cases, but the impact was most pronounced in patients with dementia.
Andrew C. Nyborg, Jonathan R. Moll, Renee D. Wegrzyn, Daniel Havas, Birgit Hutter-Paier, Alan S. Rudolph, Giora Feuerstein (Handling Associate Editor: Ute Panzenboeck)
In Vivo and Ex Vivo Imaging of Amyloid-β Cascade Aggregates with a PronucleonTM Peptide
Abstract: Accumulation of amyloid-β (Aβ) cascade aggregates is considered a hallmark of Alzheimer’s disease (AD). Current dogma holds that the appearance of Aβ oligomers and larger aggregates occur many years prior to plaque formation associated with the advanced and irreparable neurocognitive decline characteristic of AD. This premise is the impetus to identify these Aβ precursor structures prior to advanced plaque development. The PronucleonTM technology platform is comprised of a novel series of engineered peptides that provide a unique readout when associated with beta-rich fiber and oligomeric Aβ. This technology has been applied to ex vivo tissue sections and in vivo mouse models of AD to determine the potential utility of these synthetic peptides as potential imaging agents. In ex vivo studies, the PronucleonTM peptide binds plaque like structures in brain sections obtained from transgenic mice overexpressing hAPP with both the human Swedish and London Aβ mutations. In vivo, PronucleonTM peptide administered peripherally can localize to the brain and label plaques throughout the brain in transgenic mice. Taken together, the data suggest that Pronucleon™ could provide a new imaging tool for Aβ cascade elements that precede advanced plaque and fibril formation, thereby advancing early diagnosis and treatment opportunities.
David C. Zhu, Shantanu Majumdar, Igor O. Korolev, Kevin L. Berger, Andrea C. Bozoki
Alzheimer’s Disease and Amnestic Mild Cognitive Impairment Weaken Connections within the Default-Mode Network: a Multi-Modal Imaging Study
Abstract: We applied a multi-modal imaging approach to examine structural and functional alterations in the default-mode network (DMN) that are associated with Alzheimer’s disease (AD) and amnestic mild cognitive impairment (aMCI), a transitional phase between healthy cognitive aging and dementia. Subjects included 10 patients with probable AD, 11 patients with aMCI, and 12 age- and education-matched normal controls (NC). Whole-brain resting-state functional, diffusion-weighted, and volumetric magnetic resonance imaging (MRI) data as well as 18F-fluorodeoxyglucose-based positron emission tomography (FDG-PET) data were acquired. We carried out resting-state functional MRI-based functional connectivity and diffusion MRI-based structural connectivity analyses using isthmus of the cingulate cortex (ICC) and the subjacent white matter as the seeds. Whole-brain group and region of interest-based analyses demonstrated that AD weakens the structural and functional connections between ICC and other regions within the DMN, consistent with regional reduction of metabolic activity and atrophy within the DMN. A progressive weakening trend of these connections was also observed from NC to aMCI and then AD, although significant differences between aMCI and the other two groups were not found. Overall, based on both FDG-PET and MRI results, the DMN appears to serve as a window to understanding structural and functional brain changes associated with AD and aMCI.
Lei Wang-Dietrich*, Susanne Aileen Funke*, Katja Kühbach, Kun Wang, Astrid Besmehn, Sabine Willbold, Yeliz Cinar, Oliver Bannach, Eva Birkmann, Dieter Willbold *These authors contributed equally.
The Amyloid-β Oligomer Count in Cerebrospinal Fluid is a Biomarker for Alzheimer’s Disease
Abstract: Recent studies indicate that small amyloid-β peptide (Aβ) oligomers are the major toxic species responsible for development and progression of Alzheimer’s disease (AD). Therefore, we suggest that the number of Aβ oligomers in body fluids is the most direct and relevant biomarker for AD. Determination of the Aβ oligomer content of cerebrospinal fluid (CSF) samples from 14 AD patients and 12 age-matched controls revealed a clear distinction between both groups. All samples of the control group showed homogenously low numbers of Aβ oligomers, while the samples of the AD group exhibited significantly higher levels of Aβ oligomers. The Aβ oligomer numbers correlated with the patients’ Mini-Mental State Examination scores. This indicates that the quantity of Aβ oligomers in CSF reflects the severity of the disease and that Aβ oligomers play a crucial role in AD pathology and in turn can be used as a diagnostic biomarker.
Lidia Blazquez-Llorca, Ángel Merchán-Pérez, Rodrigo Rodríguez, Jorge Gascón, Javier DeFelipe
FIB/SEM Technology and Alzheimer’s Disease: Three-Dimensional Analysis of Human Cortical Synapses
Abstract: The quantification and measurement of synapses is a major goal in the study of brain organization in both health and disease. Serial section electron microscopy (EM) is the ideal method since it permits the direct quantification of crucial features such as the number of synapses per unit volume or the distribution and size of synapses. However, a major limitation is that obtaining long series of ultrathin sections is extremely time-consuming and difficult. Consequently, quantitative EM studies are scarce and the most common method employed to estimate synaptic density in the human brain is indirect, by counting at the light microscopic level immunoreactive puncta using synaptic markers. The recent development of automatic EM methods in experimental animals, such as the combination of focused ion beam milling and scanning electron microscopy (FIB/SEM), are opening new avenues. Here we explored the utility of FIB/SEM to examine the cerebral cortex of Alzheimer’s disease patients. We found that FIB/SEM is an excellent tool to study in detail the ultrastructure and alterations of the synaptic organization of the human brain. Using this technology, it is possible to reconstruct different types of plaques and the surrounding neuropil to find new aspects of the pathological process associated with the disease, namely; to count the exact number and types of synapses in different regions of the plaques, to study the spatial distribution of synapses, and to analyze the morphology and nature of the various types of dystrophic neurites and amyloid deposits.
Supplementary Data for Blazquez-Llorca et al. article (PDF)
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Claudio Babiloni, Roberta Lizio, Claudio Del Percio, Nicola Marzano, Andrea Soricelli, Elena Salvatore, Raffaele Ferri, Filomena I.I. Cosentino, Gioacchino Tedeschi, Patrizia Montella, Silvia Marino, Simona De Salvo, Guido Rodriguez, Flavio Nobili, Fabrizio Vernieri, Francesca Ursini, Ciro Mundi, Jill C. Richardson, Giovanni B. Frisoni, Paolo M. Rossini (Handling Associate Editor: J. Wesson Ashford)
Cortical Sources of Resting State EEG Rhythms are Sensitive to the Progression of Alzheimer’s Disease at Early Stage
Abstract: Cortical sources of resting state electroencephalographic (EEG) rhythms are abnormal in subjects with Alzheimer’s disease (AD). Here we tested the hypothesis that these sources are also sensitive to the progression of early stage AD over the course of one year. The resting state eyes-closed EEG data were recorded in 88 mild AD patients at baseline (Mini Mental State Evaluation, MMSE I= 21.7 ± 0.2 standard error, SE) and at approximately one-year follow up (13.3 months ± 0.5 SE; MMSE II= 20 ± 0.4 SE). All patients received standard therapy with acetylcholinesterase inhibitors. EEG recordings were also performed in 35 normal elderly (Nold) subjects as controls. EEG rhythms of interest were delta (2-4 Hz), theta (4-8 Hz), alpha 1 (8-10.5 Hz), alpha 2 (10.5-13 Hz), beta 1 (13-20 Hz), beta 2 (20-30 Hz), and gamma (30-40 Hz). Cortical EEG sources were estimated by low-resolution brain electromagnetic tomography (LORETA). Compared to the Nold subjects, the mild AD patients were characterized by a power increase of widespread delta sources and by a power decrease of posterior alpha sources. In the mild AD patients, the follow-up EEG recordings showed increased power of widespread delta sources as well as decreased power of widespread alpha and posterior beta 1 sources. These results suggest that the resting state EEG sources were sensitive, at least at group level, to the cognitive decline occurring in the mild AD group over a one-year period, and might represent cost-effective and non-invasive markers with which to enrich cohorts of AD patients that decline faster for clinical studies.
Rob J.A. Nabuurs, Remco Natté, Fenna M. de Ronde, Ingrid Hegeman-Kleinn, Jouke Dijkstra, Sjoerd G. van Duinen, Andrew G. Webb, Annemieke J. Rozemuller, Mark A. van Buchem, Louise van der Weerd (Handling Associate Editor: Wolff Kirsch)
MR Microscopy of Human Amyloid-β Deposits: Characterization of Parenchymal Amyloid, Diffuse Plaques, and Vascular Amyloid
Abstract: Cerebral deposits of amyloid-β peptides (Aβ) form the neuropathological hallmarks of Alzheimer’s disease (AD) and cerebral amyloid angiopathy (CAA). In the brain, Aβ can aggregate as insoluble fibrils present in amyloid plaques and vascular amyloid, or as diffuse plaques consisting of mainly non-fibrillar Aβ. Previously, magnetic resonance imaging (MRI) has been shown to be capable of detecting individual amyloid plaques, not only via the associated iron, but also Aβ itself has been suggested to be responsible for a decrease in the image intensity. In this current study we aim to investigate the MRI properties of the different cerebral Aβ deposits including diffuse plaques and vascular amyloid. Postmortem 60-µm-thick brain sections of AD, CAA, and Down's syndrome patients, known to contain Aβ, were studied. High resolution T2*- and T2-weighted MRI scans and quantitative relaxation maps were acquired using a microcoil on a Bruker 9.4T MRI system. Specific MRI characteristics of each type of Aβ deposit were examined by co-registration of the MRI with Congo Red and Aβ-immunostainings of the same sections. Our results show that only fibrillar Aβ, present in both vascular and parenchymal amyloid, induced a significant change in T2* and T2 values. However, signal changes were not as consistent for all of the vessels affected by CAA, irrespective of possible dyshoric changes. In contrast, the non-fibrillar diffuse plaques did not create any detectable MRI signal changes. These findings are relevant for the interpretation and further development of (quantitative) MRI methods for the detection and follow-up of AD and CAA.
Sara van Duijn, Rob J.A. Nabuurs, Sjoerd G. van Duinen, Remco Natté, Mark A. van Buchem, Alia Alia
Longitudinal Monitoring of Sex-Related in vivo Metabolic Changes in the Brain of Alzheimer’s Disease Transgenic Mouse using Magnetic Resonance Spectroscopy
Abstract: Epidemiological studies indicate that the incidence of Alzheimer’s disease (AD) is higher in women than in men. There is evidence that changes in metabolites in the brain associated with the development of AD are present earlier than structural brain changes. The effect of sex on the metabolic profile during the development of AD has not yet been studied. In this study we longitudinally monitored and compared in vivo metabolic changes in male and female AβPPswe,PSEN1dE9 transgenic mice brains using magnetic resonance spectroscopy. Our results show a lower level of glutamate as well as of N-acetylaspartate (NAA) in transgenic mice. The decline in NAA with age was more apparent in female mice. The level of taurine was higher in female mice and showed a faster decline over time. In conclusion, our study is the first to suggest that changes in the metabolic profile during AD development are influenced by sex.