Pages 817-836
Review
Tapan K. Khan, Daniel L. Alkon
Alzheimer’s Disease Cerebrospinal Fluid and Neuroimaging Biomarkers: Diagnostic Accuracy and Relationship to Drug Efficacy
Abstract: Widely researched Alzheimer’s disease (AD) biomarkers include in vivo brain imaging with PET and MRI, imaging of amyloid plaques, and biochemical assays of Aβ1-42, total tau, and phosphorylated tau (p-tau-181) in cerebrospinal fluid (CSF). In this review, we critically evaluate these biomarkers and discuss their clinical utility for the differential diagnosis of AD. Current AD biomarker tests are either highly invasive (requiring CSF collection) or expensive and labor-intensive (neuroimaging), making them unsuitable for use in the primary care, clinical office-based setting, or to assess drug efficacy in clinical trials. In addition, CSF and neuroimaging biomarkers continue to face challenges in achieving required sensitivity and specificity and minimizing center-to-center variability (for CSF-Aβ1-42 biomarkers CV=26.5%; http://www.alzforum.org/news/conference-coverage/paris-standardization-hurdle-spinal-fluid-imaging-markers). Although potentially useful for selecting patient populations for inclusion in AD clinical trials, the utility of CSF biomarkers and neuroimaging techniques as surrogate endpoints of drug efficacy needs to be validated. Recent trials of β- and γ-secretase inhibitors and Aβ immunization-based therapies in AD showed no significant cognitive improvements, despite changes in CSF and neuroimaging biomarkers. As we learn more about the dysfunctional cellular and molecular signaling processes that occur in AD, and how these processes are manifested in tissues outside of the brain, new peripheral biomarkers may also be validated as non-invasive tests to diagnose preclinical and clinical AD.
Pages 837-842
Short Communication
Delphine Asselineau, Khadija Benlhassan, Beatrice Arosio, Daniela Mari, Evelyn Ferri, Martina Casati, Cristina Gussago, Enzo Tedone, Giorgio Annoni, Paolo Mazzola, Francois Piette, Joel Belmin, Sylvie Pariel, Anne Bornand, Jean-Louis Beaudeux, Mohamed Doulazmi, Jean Mariani, Dorothy H. Bray (Handling Associate Editor: Federico Licastro)
Interleukin-10 Production in Response to Amyloid-β Differs between Slow and Fast Decliners in Patients with Alzheimer’s DiseaseAbstract: We investigated IL-10 and IL-6 production in amyloid-β (Aβ) stimulated peripheral blood mononuclear cells (PBMCs) in twenty Alzheimer’s disease (AD) patients with slow progression, eleven with fast progression, and twenty age-matched controls. Promoter polymorphisms in IL-10 (position -592, -819, -1082), IL-6 (-174), transforming growth factor-β1 (TGF-β1) (-10, -25), interferon-γ (IFN-γ) (-874), and tumor necrosis factor-α (TNF-α) (-308) genes were analyzed. IL-10 production after Aβ stimulation was high in PBMC from slow decliners and almost completely abrogated in fast decliners. Association between AA IFN-γ low-producing genotype and fast progression was demonstrated. Investigations in a larger sample will clarify these findings.
Pages 843-848
Short Communication
Isabel Arrieta-Cruz, Colette M. Knight, Roger Gutiérrez-Juárez
Acute Exposure of the Mediobasal Hypothalamus to Amyloid-β25-35 Perturbs Hepatic Glucose Metabolism
Abstract: Patients with Alzheimer’s disease (AD) have a higher risk for developing insulin resistance and diabetes. Amyloid plaques, a hallmark of AD, are composed of amyloid-β (Aβ). Because the mediobasal hypothalamus controls hepatic glucose production, we examined the hypothesis that its exposure to Aβ perturbs the regulation of glucose metabolism. The infusion of Aβ25-35, but not its scrambled counterpart, into the mediobasal hypothalamus of young rats, increased circulating glucose as a consequence of enhanced hepatic glucose production during pancreatic clamp studies. These findings suggest a link between AD and alterations of glucose metabolism.
Pages 849-853
Short Communication
Philipp O. Tsvetkov, Ivan B. Cheglakov, Armen A. Ovsepyan, Oleg Y. Mediannikov, Alexander O. Morozov, Georgy B. Telegin, Sergey A. Kozin (Handling Associate Editor: Vladimir Buchman)
Peripherally Applied Synthetic Tetrapeptides HAEE and RADD Slow Down the Development of Cerebral β-Amyloidosis in AβPP/PS1 Transgenic Mice
Abstract: Two tetrapeptides, HAEE and RADD, which are ionic-complementary to the primary zinc recognition site of amyloid-β (Aβ), have been reported to inhibit zinc-induced dimerization of the Aβ metal-binding domain and slow Aβ aggregation in vitro. In the present study, we investigate the impact of HAEE and RADD on the development of cerebral β-amyloidosis in a mouse model of Alzheimer’s disease. We have found chronic intravenous administration of each peptide results in significant decrease of amyloid plaque burden in the treated mice.
Pages 855-862
Geneviève Nolze-Charron, Abderazzak Mouiha, Simon Duchesne, Christian Bocti, for the Alzheimer’s Disease Neuroimaging Initiative
White Matter Hyperintensities in Mild Cognitive Impairment and Lower Risk of Cognitive Decline
Abstract: Background: White matter hyperintensities (WMH) may have a different impact on cognitive decline depending on strategic localization. Objective: The goal of this study is to assess the impact of global and cholinergic WMH on cognitive decline of mild cognitive impairment (MCI) patients in the ADNI-1 dataset. Methods: This is a retrospective analysis of data from a natural history study. MRI scans (T2 and PD sequences) were assessed with two visual scales: 1) The Cholinergic Pathways HyperIntensities Scale (CHIPS) score, designed to assess WMH in the cholinergic tracts, and 2) the Age-Related White Matter Changes Scale (ARWMC), a scale to assess the global WMH burden. All subjects underwent standardized neuropsychological testing. Results: Subjects included 310 individuals with MCI. Analysis showed no association between WMH at baseline and conversion from MCI to Alzheimer’s disease (AD), either for the global WMH burden or WMH within the cholinergic pathways. However, ARWMC scores had a significant confounding effect (p=0.03) on conversion to dementia (hazard ratio of 0.37) among MCI subjects with low executive functions. Conclusion: We found no association between the burden of WMH at baseline in MCI and conversion to AD over 3 years. However, a higher global WMH burden appears to reduce the risk of conversion to AD in subjects with low executive functions. These results suggest that higher WMH burden in MCI individuals may be associated with a more gradual cognitive decline or stabilization, compared to a low WMH burden.
Pages 863-876
Hao Wu*, Mei-Hong Lu*, Wang Wang, Mao-Ying Zhang, Qian-Qian Zhu, Yi-Yuan Xia, Ru-Xiang Xu, Yi Yang, Li-Hua Chen, Quan-Hong Ma (Handling Associate Editor: Yong Shen) *These authors contributed equally to this work.
Lamotrigine Reduces β-Site AβPP-Cleaving Enzyme 1 Protein Levels Through Induction of Autophagy
Abstract: Lamotrigine (LTG), a broad-spectrum anti-epileptic drug widely used in treatment for seizures, shows potential efficacy in Alzheimer’s disease (AD) therapy. Chronic LTG treatment rescues the suppressed long-term potentiation, loss of spines and cognitive deficits in AβPP/PS1 mice, known to overexpress a chimeric mouse/human mutant amyloid-β protein precursor (AβPP) and a mutant human presenilin 1 (PS1). These changes are accompanied by reduction of amyloid-β (Aβ) plaques density and of levels of β-C-terminal fragment of AβPP (β-CTF), a fragment of AβPP cleaved by β-secretase. These results suggest LTG treatment reduces Aβ production, possibly through modulation of cleavage of AβPP by β-secretase. However, the underlying mechanisms still remain unclear. In this study, decreased protein levels, but not mRNA levels of β-site AβPP-cleaving enzyme 1 (BACE1), were observed in cultured HEK293 cells and the brains of AβPP/PS1 transgenic mice upon LTG treatment. Moreover, LTG treatment suppressed mammalian target of rapamycin (mTOR) signaling, while enhancing activation of cAMP response element binding protein (CREB), two signaling pathways essential for autophagy induction. LTG treatment increased the numbers of LC3-GFP+ puncta and LC3-II levels in HEK293 cells, indicating an induction of autophagy. The downregulation of BACE1 by LTG treatment was prevented by the autophagy inhibitor 3-Methyladenine. Therefore, this study shows that LTG treatment reduces the protein levels of BACE1 through activation of autophagy, possibly via inhibition of mTOR signaling and activation of CREB.
Pages 877-888
Henrik H. Hansen, Katrine Fabricius, Pernille Barkholt, Michael L. Niehoff, John E. Morley, Jacob Jelsing, Charles Pyke, Lotte Bjerre Knudsen, Susan A Farr, Niels Vrang
The GLP-1 Receptor Agonist Liraglutide Improves Memory Function and Increases Hippocampal CA1 Neuronal Numbers in a Senescence-Accelerated Mouse Model of Alzheimer’s Disease
Abstract: Recent studies indicate that glucagon-like peptide 1 (GLP-1) receptor agonists, currently used in the management of type 2 diabetes, exhibit neurotrophic and neuroprotective effects in amyloid-β (Aβ) toxicity models of Alzheimer’s disease (AD). We investigated the potential pro-cognitive and neuroprotective effects of the once-daily GLP-1 receptor agonist liraglutide in senescence-accelerated mouse prone 8 (SAMP8) mice, a model of age-related sporadic AD not dominated by Aβ plaques. Six-month-old SAMP8 mice received liraglutide (100 or 500 µg/kg/day, s.c.) or vehicle once daily for 4 months. Vehicle-dosed age-matched 50% back-crossed as well as untreated young (4-month-old) SAMP8 mice were used as control groups for normal memory function. Vehicle-dosed 10-month-old SAMP8 mice showed significant learning and memory retention deficits in an active-avoidance T-maze, as compared to both control groups. Also, 10-month-old SAMP8 mice displayed no immunohistological signatures of Aβ plaques or hyperphosphorylated tau, indicating the onset of cognitive deficits prior to deposition of amyloid plaques and neurofibrillary tangles in this AD model. Liraglutide significantly increased memory retention and total hippocampal CA1 pyramidal neuron numbers in SAMP8 mice, as compared to age-matched vehicle-dosed SAMP8 mice. In conclusion, liraglutide delayed or partially halted the progressive decline in memory function associated with hippocampal neuronal loss in a mouse model of pathological aging with characteristics of neurobehavioral and neuropathological impairments observed in early-stage sporadic AD.
Pages 889-899
Els Coart, Leandro García Barrado, Flora H. Duits, Philip Scheltens, Wiesje M. van der Flier, Charlotte E. Teunissen, Saskia M. van der Vies, Tomasz Burzykowski, for the Alzheimer’s Disease Neuroimaging Initiative (Handling Associate Editor: Henrik Zetterberg)
Correcting for the Absence of a Gold Standard Improves Diagnostic Accuracy of Biomarkers in Alzheimer’s Disease
Abstract: Background: Studies investigating the diagnostic accuracy of biomarkers for Alzheimer’s disease (AD) are typically performed using the clinical diagnosis or amyloid-β positron emission tomography as the reference test. However, neither can be considered a gold standard or a perfect reference test for AD. Not accounting for errors in the reference test is known to cause bias in the diagnostic accuracy of biomarkers. Objective: To determine the diagnostic accuracy of AD biomarkers while taking the imperfectness of the reference test into account. Methods: To determine the diagnostic accuracy of AD biomarkers and taking the imperfectness of the reference test into account, we have developed a Bayesian method. This method establishes the biomarkers’ true value in predicting the AD-pathology status by combining the reference test and the biomarker data with available information on the reliability of the reference test. The new methodology was applied to two clinical datasets to establish the joint accuracy of three cerebrospinal fluid biomarkers (amyloid-β1-42, Total tau, and P-tau181) by including the clinical diagnosis as imperfect reference test into the analysis. Results: The area under the receiver-operating-characteristics curve to discriminate between AD and controls, increases from 0.949 (with 95% credible interval [0.935,0.960]) to 0.990 ([0.985,0.995]) and from 0.870 ([0.817,0.912]) to 0.975 ([0.943,0.990]) for the cohorts, respectively. Conclusions: Use of the Bayesian methodology enables an improved estimate of the exact diagnostic value of AD biomarkers and overcomes the lack of a gold standard for AD. Using the new method will increase the diagnostic confidence for early stages of AD.
Pages 901-912
Benjamin M. Kandel, Brian B. Avants, James C. Gee, Steven E. Arnold, David A. Wolk; for the Alzheimer’s Disease Neuroimaging Initiative (Handling Associate Editor: Andrew Saykin)
Neuropsychological Testing Predicts Cerebrospinal Fluid Amyloid-β in Mild Cognitive Impairment
Abstract: Background: Psychometric tests predict conversion of mild cognitive impairment (MCI) to probable Alzheimer’s disease (AD). Because the definition of clinical AD relies on those same psychometric tests, the ability of these tests to identify underlying AD pathology remains unclear. Objective: To determine the degree to which psychometric testing predicts molecular evidence of AD amyloid pathology, as indicated by cerebrospinal fluid (CSF) amyloid-β (Aβ)1-42, in patients with MCI, as compared to neuroimaging biomarkers. Methods: We identified 408 MCI subjects with CSF Aβ levels, psychometric test data, FDG-PET scans, and acceptable volumetric MR scans from the Alzheimer’s Disease Neuroimaging Initiative (ADNI). We used psychometric tests and imaging biomarkers in univariate and multivariate models to predict Aβ status. Results: The 30-min delayed recall score of the Rey Auditory Verbal Learning Test was the best predictor of Aβ status among the psychometric tests, achieving an AUC of 0.67±0.02 and odds ratio of 2.5±0.4. FDG-PET was the best imaging-based biomarker (AUC 0.67±0.03, OR 3.2±1.2), followed by hippocampal volume (AUC 0.64±0.02, OR 2.4±0.3). A multivariate analysis based on the psychometric tests improved on the univariate predictors, achieving an AUC of 0.68±0.03 (OR 3.38±1.2). Adding imaging biomarkers to the multivariate analysis did not improve the AUC. Conclusion: Psychometric tests perform as well as imaging biomarkers to predict presence of molecular markers of AD pathology in MCI patients and should be considered in the determination of the likelihood that MCI is due to AD.
Pages 913-928
Mansi R. Khanna, Mark E. Fortini (Handling Associate Editor: M. Paul Murphy)
Transcriptomic Analysis of Drosophila Mushroom Body Neurons Lacking Amyloid-β Precursor-Like Protein Activity
Abstract: The amyloid-β protein precursor (AβPP) is subjected to sequential intramembrane proteolysis by α-, β-, and γ-secretases, producing secreted amyloid-β (Aβ) peptides and a cytoplasmically released AβPP Intracellular Domain (AICD). AICD complexes with transcription factors in the nucleus, suggesting that this AβPP fragment serves as an active signaling effector that regulates downstream genes, although its nuclear targets are poorly defined. To further understand this potential signaling mechanism mediated by AβPP, we performed a transcriptomic identification of the Drosophila genome that is regulated by the fly AβPP orthologue in fly mushroom body neurons, which control learning- and memory-based behaviors. We find significant changes in expression of 245 genes, representing approximately 1.6% of the Drosophila genome, with the changes ranging from +6 fold to -40 fold. The largest class of responsive targets corresponds to non-protein coding genes and includes microRNAs that have been previously implicated in Alzheimer’s disease pathophysiology. Several genes were identified in our Drosophila microarray analyses that have also emerged as putative AβPP targets in similar mammalian transcriptomic studies. Our results also indicate a role for AβPP in cellular pathways involving the regulation of Drosophila Casein Kinase II, mitochondrial oxidative phosphorylation, RNA processing, and innate immunity. Our findings provide insights into the intracellular events that are regulated by AβPP activity in healthy neurons and that might become dysregulated as a result of abnormal AβPP proteolysis in AD.
Pages 929-946
Elisa Kärkkäinen, Hanna-Maija Lahtinen, Johanna Närväinen, Olli Gröhn, Heikki Tanila (Handling Associate Editor: Gary Arendash)
Brain Amyloidosis and BDNF Deficiency Have Opposite Effects on Brain Volumes in AβPP/PS1 Mice Both in vivo and ex vivo
Abstract: Magnetic resonance imaging (MRI) volumetry is widely used in Alzheimer’s disease (AD) research and diagnostics alongside clinical assessment. Yet few MRI volumetry studies have been conducted in AD model mice with mixed results. We performed in vivo and ex vivo MRI and extensive postmortem histological analysis in transgenic mice derived from crossing amyloid plaque producing AβPP/PS1 mice with brain-derived neurotrophic factor (BDNF)+/– mice. This allowed us to compare developmental volumetric changes due to BDNF deficiency with progressive changes due to amyloid accumulation. We found decreased whole brain volume at 3 months and decreased cortical volume at both 3 and 8 months in vivo in BDNF+/– Tg mice but increased whole brain and cortical volumes at 8 months in AβPP/PS1 mice. Consistent with this, the postmortem histological analysis showed decreased brain parenchymal area in BDNF+/– mice but an increase in AβPP/PS1 mice. BDNF gene deficiency did not affect brain amyloid load or astrogliosis, but led to decreased dentate gyrus length, whereas AβPP/PS1 mice had significantly increased amyloid load, astrogliosis, and decreased neurogenesis. Distinct and layer-specific effects were found in the hippocampus of AβPP/PS1 and BDNF+/– mice. In contrast to human AD patients, brain atrophy in amyloid producing mice appears to be masked by volume increase due to amyloid accumulation and especially accompanying astrogliosis. Our results indicate that cortical MRI volumetry can be used to some extent as a proxy to progressive brain amyloidosis in preclinical studies.
Pages 947-961
Nicola Voyle, David Baker, Samantha C. Burnham, Antonia Covin, Zhanpan Zhang, Dipen P. Sangurdekar, Cristina A. Tan Hehir, Chantal Bazenet, Simon Lovestone, Steven Kiddle*, Richard J.B. Dobson*, and the AIBL research group (Handling Associate Editor: Gary Arendash) *These authors are considered joint senior authors.
Blood Protein Markers of Neocortical Amyloid-β Burden: A Candidate Study Using SOMAscan Technology
Abstract: Background: Four previously reported studies have tested for association of blood proteins with neocortical amyloid-β burden (NAB). If shown to be robust, these proteins could have utility as a blood test for enrichment in clinical trials of Alzheimer’s disease (AD) therapeutics. Objective: This study aimed to investigate whether previously identified blood proteins also show evidence for association with NAB in serum samples from the Australian Imaging, Biomarker and Lifestyle Flagship Study of Ageing (AIBL). The study considers candidate proteins seen in cohorts other than AIBL and candidates previously discovered in the AIBL cohort. Methods: Our study used the SOMAscan platform for protein quantification in blood serum. Linear and logistic regressions were used to model continuous NAB and dichotomized NAB respectively using single proteins as a predictor. Multiple protein models were built using stepwise regression techniques and support vectors machines. Age and APOE ε4 carriage were used as covariates for all analysis. Results: Of the 41 proteins previously reported, 15 AIBL candidates and 20 non-AIBL candidates were available for testing. Of these candidates, pancreatic polypeptide (PPY) and IgM showed a significant association with NAB. Notably, IgM was found to associate with continuous NAB across cognitively normal control subjects. Conclusions: We have further demonstrated the association of PPY and IgM with NAB, despite technical differences between studies. There are several reasons for a lack of significance for the other candidates including platform differences and the use of serum rather than plasma samples. To investigate the possibility of technical differences causing lack of further replication, further studies are required.
Pages 963-970
Maddalena Boccia, Mauro Acierno, Laura Piccardi
Neuroanatomy of Alzheimer’s Disease and Late-Life Depression: A Coordinate-Based Meta-Analysis of MRI Studies
Abstract: Depression and cognitive impairment are both common disorders in elderly people and frequently occur together. Due to the presence of a common set of behavioral and cognitive symptoms, differential diagnosis may become arduous. Neuroimaging may offer a good tool during diagnosis. We performed a coordinate-based meta-analysis to compare gray matter changes in Alzheimer’s disease (AD) and late-life depression (LLD). AD and LLD led to brain atrophy in networks only partially overlapping. Both conditions are linked to a reduction of the bilateral hippocampal volume, but AD is correlated with great atrophy in the left anterior hippocampus and bilateral posterior cingulate cortex, while LLD is correlated with great atrophy in the precuneus, superior frontal gyrus, and ventromedial frontal. Present results shed some light on neural underpinnings of AD and LLD and provide new useful evidence for differential diagnosis.
Pages 971-982
Tobias Welt, Luka Kulic, Sarah E. Hoey, Jordan McAfoose, Claudia Späni, Antonella Santuccione Chadha, Abraham Fisher, Roger M. Nitsch
Acute Effects of Muscarinic M1 Receptor Modulation on AβPP Metabolism and Amyloid-β Levels in vivo: A Microdialysis Study
Abstract: Indirect modulation of cholinergic activity by cholinesterase inhibition is currently a widely established symptomatic treatment for Alzheimer’s disease (AD). Selective activation of certain muscarinic receptor subtypes has emerged as an alternative cholinergic-based amyloid-lowering strategy for AD, as selective muscarinic M1 receptor agonists can reduce amyloid-β (Aβ) production by shifting endoproteolytic amyloid-β protein precursor (AβPP) processing toward non-amyloidogenic pathways. In this study, we addressed the hypothesis that acute stimulation of muscarinic M1 receptors can inhibit Aβ production in awake and freely moving AβPP transgenic mice. By combining intracerebral microdialysis with retrodialysis, we determined hippocampal Aβ concentrations during simultaneous pharmacological modulation of brain M1 receptor function. Infusion with a M1 receptor agonist AF102B resulted in a rapid reduction of interstitial fluid (ISF) Aβ levels while treatment with the M1 antagonist dicyclomine increased ISF Aβ levels reaching significance within 120 minutes of treatment. The reduction in Aβ levels was associated with PKCα and ERK activation resulting in increased levels of the α-secretase ADAM17 and a shift in AβPP processing toward the non-amyloidogenic processing pathway. In contrast, treatment with the M1 receptor antagonist dicyclomine caused a decrease in levels of phosphorylated ERK that was independent of PKCα, and led to an elevation of β-secretase levels associated with increased amyloidogenic AβPP processing. The results of this study demonstrate rapid effects of in vivo M1 receptor modulation on the ISF pool of Aβ and suggest that intracerebral microdialysis with retrodialysis is a useful technical approach for monitoring acute treatment effects of muscarinic receptor modulators on AβPP/Aβ metabolism.
Pages 983-987
Commentary
Richard J. Wurtman
How Anticholinergic Drugs Might Promote Alzheimer’s Disease: More Amyloid-β and Less Phosphatidylcholine
Abstract: Drugs that block muscarinic cholinergic neurotransmission in the brain can, as a consequence, increase the formation of amyloid-β, and decrease brain levels of phosphatidylcholine (by slowing its synthesis and accelerating its turnover). Both of these effects might cause a decrease in brain synapses, as characterizes and probably underlies the memory disorder of early Alzheimer’s disease.
Pages 989-1005
Hyeon-Gu Yeo*, Youngjeon Lee*, Chang-Yeop Jeon*, Kang-Jin Jeong, Yeung Bae Jin, Philyong Kang, Sun-Uk Kim, Ji-Su Kim, Jae-Won Huh, Young-Hyun Kim, Bo-Woong Sim, Bong-Seok Song, Young-Ho Park, Yonggeun Hong, Sang-Rae Lee, Kyu-Tae Chang (Handling Associate Editor: Isidro Ferrer) *These authors contributed equally to this work.
Characterization of Cerebral Damage in a Monkey Model of Alzheimer’s Disease Induced by Intracerebroventricular Injection of Streptozotocin
Abstract: In line with recent findings showing Alzheimer’s disease (AD) as an insulin-resistant brain state, a non-transgenic animal model with intracerebroventricular streptozotocin (icv-STZ) administration has been proposed as a representative experimental model of AD. Although icv-STZ rodent models of AD have been increasingly researched, studies in non-human primate models are very limited. In this study, we aimed to characterize the cerebral damage caused by icv-STZ in non-human primates; to achieve this, three cynomolgus monkeys (Macaca fascicularis) were administered four dosages of STZ (2 mg/kg) dissolved in artificial cerebrospinal fluid and another three controls were injected with only artificial cerebrospinal fluid at the cerebellomedullary cistern. In vivo neuroimaging was performed with clinical 3.0 T MRI, followed by quantitative analysis with FSL for evaluation of structural changes of the brain. Immunohistochemistry was performed to evaluate cerebral histopathology. We showed that icv-STZ caused severe ventricular enlargement and parenchymal atrophy, accompanying amyloid-β deposition, hippocampal cell loss, tauopathy, ependymal cell loss, astrogliosis, and microglial activation, which are observed in human aged or AD brain. The findings suggest that the icv-STZ monkey model would be a valuable resource to study the mechanisms and consequences of a variety of cerebral pathologies including major pathological hallmarks of AD. Furthermore, the study of icv-STZ monkeys could contribute to the development of treatments for age- or AD-associated cerebral changes.
Pages 1007-1020
William I. Zhang, Gregory Antonios, Alberto Rabano, Thomas A. Bayer, Anja Schneider, Silvio O. Rizzoli
Super-Resolution Microscopy of Cerebrospinal Fluid Biomarkers as a Tool for Alzheimer’s Disease Diagnostics
Abstract: Alzheimer’s disease (AD) is neuropathologically characterized by aggregates of amyloid-β peptides (Aβ) and tau proteins. The consensus in the AD field is that Aβ and tau should serve as diagnostic biomarkers for AD. However, their aggregates have been difficult to investigate by conventional fluorescence microscopy, since their size is below the diffraction limit (~200 nm). To solve this, we turned to a super-resolution imaging technique, stimulated emission depletion (STED) microscopy, which has a high enough precision to allow the discrimination of low- and high-molecular weight aggregates prepared in vitro. We used STED to analyze the structural organization of Aβ and tau in cerebrospinal fluid (CSF) from 36 AD patients, 11 patients with mild cognitive impairment (MCI), and 21 controls. We measured the numbers of aggregates in the CSF samples, and the aggregate sizes and intensities. These parameters enabled us to distinguish AD patients from controls with a specificity of ~87% and a sensitivity of ~79%. In addition, the aggregate parameters determined with STED microscopy correlated with the severity of cognitive impairment in AD patients. Finally, these parameters may be useful as predictive tools for MCI cases. Two MCI patients who developed AD during the course of the study were correctly identified. The same was observed for MCI patients whose Aβ ELISA values fall within the accepted range for AD. We suggest that super-resolution imaging is a promising tool for AD diagnostics.
Pages 1021-1032
Pankaj D. Mehta, Bruce A. Patrick, Marc Barshatzky, Sangita P. Mehta, Janusz Frackowiak, Bozena Mazur-Kolecka, David L. Miller
Generation of Rabbit Monoclonal Antibody to Amyloid-β38 (Aβ38): Increased Plasma Aβ38 Levels in Down Syndrome
Abstract: Secreted soluble amyloid-β (Aβ)38 is the second most prominent Aβ form next to Aβ40, and is found in cerebrospinal fluid (CSF) and blood. Recent studies have shown the importance of quantitation of CSF Aβ38 levels in combination with those of Aβ40 and Aβ42 to support the diagnosis of Alzheimer’s disease (AD), and other neurodegenerative diseases, and to facilitate drug discovery studies. However, the availability of reliable and specific Aβ38 monoclonal antibody is limited. Our first aim was to generate and partially characterize rabbit monoclonal antibody (RabmAb) to Aβ38. The antibody was specific to Aβ38, since it did not react with Aβ37, Aβ39, Aβ40, or Aβ42 in ELISA or immunoblotting. The antibody was sensitive enough to measure Aβ38 levels in plasma. Our second aim was to quantitate Aβ38 levels in plasma from older Down syndrome (DS) persons and age-matched controls. Persons with DS (35 years and older) have neuropathological changes characteristic of AD. Studies have shown that plasma Aβ40 and Aβ42 levels are higher in older persons with DS than in controls. However, none examined Aβ38 levels in DS. Our quantitation data showed that, like Aβ40 and Aβ42 plasma levels, Aβ38 plasma levels were higher in DS than in controls. Longitudinal studies will determine whether plasma Aβ38 levels in combination with levels of Aβ40 and Aβ42 are useful to predict early signs of AD in DS.
Pages 1033-1038
Annachiara Cagnin, Mariachiara Simioni, Matteo Tagliapietra, Valentina Citton, Sara Pompanin, Alessandro Della Puppa, Mario Ermani, Renzo Manara (Handling Associate Editor: Daniela Galimberti)
A Simplified Callosal Angle Measure Best Differentiates Idiopathic-Normal Pressure Hydrocephalus from Neurodegenerative Dementia
Abstract: Background: Idiopathic normal-pressure hydrocephalus (iNPH) can resemble or occur in combination with other brain disorders frequently present in the elderly such as Alzheimer’s disease (AD) and dementia with Lewy bodies (DLB). Objective: To study the accuracy of a simplified callosal angle measure in differentiating iNPH from DLB and AD using conventional brain MRI. Methods: 76 patients (24 iNPH, 30 DLB, 22 AD) and 40 healthy controls served as discovering cohort. The callosal angle measure was obtained on standard coronal brain MRI images crossing the corpus callosum midpoint. 41 patients (21 iNPH and 20 DLB/AD) were used as independent validation cohort. A set of other conventional MRI markers of iNPH was also evaluated. Results: iNPH showed a significantly decreased mean callosal angle value compared to both disease groups and controls (iNPH=109±9; DLB=136.9±8.2; AD=135.4±11.3; Controls=138.5±5.2; p<0.00001). Using a cut-off angle of 123, derived by the mean -3SD of the control group, an accuracy of 96% (sensitivity 100%, specificity 95.4%) was obtained. By ROC analysis, the area under the curve was 0.99 (95% CI: 0.97–1). The measure was consistent (inter-rater: r=0.94) and reproducible (intra-rater: r=0.89). In the validation cohort, this cut-off angle value discriminated iNPH from DLB/AD with 97.5% accuracy. None of the conventional MRI signs reached the same accuracy. Conclusions: This simplified callosal angle measure represents an accurate, reproducible, and easy marker of iNPH.
Pages 1039-1047
Alex Dregan, Phil Chowienczyk, Martin C. Gulliford (Handling Associate Editor: Calogero Caruso)
Are Inflammation and Related Therapy Associated with All-Cause Dementia in a Primary Care Population?
Abstract: Background: There is limited primary-care based evidence for an association between chronic inflammation and related therapy with all-cause dementia. Objective: To estimate the association between several chronic inflammatory disorders and related drug therapy and all-cause dementia. Methods: The study population included a cohort of patients diagnosed with inflammatory conditions and matching controls (ratio 1:2) from the Clinical Practice Research Datalink, a database or primary care records in the UK. Inflammation patients and controls were matched on age, gender, and family practice. The study outcome measure was all-cause dementia. Chronic inflammation diagnosis and anti-inflammatory drugs represented the exposure variables of interest. Competing risks analyses were used to estimate the risk of dementia associated with exposure variables. Results: There were 1,378 (1%) and 2,805 (1%) dementia events recorded for chronic inflammation patients and their matched controls, respectively. Systemic vasculitis was associated with increased hazard ratios of dementia (1.75, 95% confidence interval (CI) 1.35-2.27, p<0.001). The analyses revealed increased risk of dementia for systemic vasculitis (1.64, 95%CI 1.24-2.18), Crohn’s diseases (2.08, 95%CI 1.16-3.74), bullous skin diseases (1.55, 95%CI 1.11-2.18), and inflammatory arthritis (1.33, 95%CI1.06-1.63) among treated patients. Combined glucocorticoids and NSAID therapy suggested reduced risk of dementia across most conditions, particularly systemic autoimmune disorders (0.41, 95%CI 0.18-0.95). Conclusion: The association between chronic inflammation and dementia varied across inflammatory disorders, being stronger for systemic vasculitis. There was evidence that combined therapy was associated with lower risk of dementia across most disorders. These data highlight potential avenues for future mechanistic and intervention investigations.
Pages 1049-1070
Hui Wang, Lan Tan, Hui-Fu Wang, Ying Liu, Rui-Hua Yin, Wen-Ying Wang, Xiao-Long Chang, Teng Jiang, Jin-Tai Yu (Handling Associate Editor: Francesca Baglio)
Magnetic Resonance Spectroscopy in Alzheimer’s Disease: Systematic Review and Meta-Analysis
Abstract: Background: The application of non-invasive proton magnetic resonance spectroscopy (1H-MRS) could potentially identify changes in cerebral metabolites in the patients with Alzheimer’s disease (AD). However, whether these metabolites can serve as biomarkers for the diagnosis of AD remains unclear. Objective: Using meta-analysis, we aimed to investigate the patterns of cerebral metabolite changes in several cerebral regions that are strongly associated with cognitive decline in AD patients. Methods: Using Hedges’ g effect size, a systematic search was performed in PubMed, Cochrane Library, Ovid, Embase, and EBSCO, and 38 studies were integrated into the final meta-analysis. Results: According to the observational studies, N-acetyl aspartate (NAA) in AD patients was significantly reduced in the posterior cingulate (PC) (effect size (ES)=-0.924, p<0.005) and bilateral hippocampus (left hippocampus: ES=-1.329, p<0.005; right hippocampus: ES=-1.287, p<0.005). NAA/Cr (creatine) ratio decreased markedly in the PC (ES=-1.052, p<0.005). Simultaneously, significant elevated myo-inositol (mI)/Cr ratio was found not only in the PC but also in the parietal gray matter. For lack of sufficient data, we failed to elucidate the efficacy of pharmacological interventions with the metabolites changes. Conclusion: The available data indicates that NAA, mI, and the NAA/Cr ratio might be potential biomarkers of brain dysfunction in AD subjects. Choline (Cho)/Cr and mI/NAA changes might also contribute toward the diagnostic process. Thus, large, well-designed studies correlated with cerebral metabolism are needed to better estimate the cerebral extent of alterations in brain metabolite levels in AD patients.
Pages 1071-1077
Jacopo C. DiFrancesco, Mehdi Touat, Massimo Caulo, Massimo Gallucci, Béatrice Garcin, Richard Levy, Antonino Uncini, Fabrizio Piazza
Recurrence of Cerebral Amyloid Angiopathy-Related Inflammation: A Report of Two Cases from the iCAβ International Network
Abstract: Background. Cerebral amyloid angiopathy-related inflammation (CAA-ri) represents the most readily responsive form of CAA, if diagnosed and treated early. Although CAA-ri typically presents with a monophasic pattern, recurrences have been occasionally reported. Objectives. To describe the evolution of the clinical and neuroradiological features of CAA-ri recurrence. Methods. From the 60 CAA-ri cases recruited through the iCAβ International Network, we identified those patients who experienced a CAA-ri recurrence at more than 12 months after the first inflammatory event. Neuroradiological evidence of cerebral inflammation (vasogenic edema) and sulcal superficial siderosis or multiple areas of cortical/subcortical microhemorrhages (MHs) were evaluated based upon fluid-attenuated inversion recovery and T2*-weighted gradient echo or susceptibility weighted imaging, respectively. In one patient, the deposition of amyloid-β was evaluated using 11C-Pittsburgh Compound B-positron emission tomography (PiB-PET). Results. Of the 60 cases, two were identified as having experienced a late CAA-ri recurrence, at two and seven years after the first presentation, respectively. At recurrence, the inflammatory lesions colocalized with the appearance of new MHs and were observed in brain areas different from those where the first onset occurred. PiB-PET four months after remission showed particularly low amyloid-β deposition in the left frontal lobe, while no change was observed in the area of the inflammatory relapse. Conclusions. Our observations highlight the importance of not underestimating any new neurological symptoms in patients who have already experienced an episode of CAA-ri. Although the frequency of CAA-ri recurrences is rare, in cases of suspected relapse, a prompt clinical and radiological follow-up should be considered in order to obtain a timely diagnosis and treatment, having a potential strong impact on patients’ clinical outcome.
Pages 1079-1089
Samantha C. Burnham, Nandini Raghavan, William Wilson, David Baker, Michael T. Ropacki, Gerald Novak, David Ames, Kathryn Ellis, Ralph N. Martins, Paul Maruff, Colin L. Masters, Gary Romano, Christopher C. Rowe, Greg Savage, S. Lance Macaulay, Vaibhav A. Narayan, for the Alzheimer’s Disease Neuroimaging Initiative and the AIBL Research Group
Novel Statistically-Derived Composite Measures for Assessing the Efficacy of Disease-Modifying Therapies in Prodromal Alzheimer’s Disease Trials: An AIBL Study
Abstract: Background: There is a growing consensus that disease-modifying therapies must be given at the prodromal or preclinical stages of Alzheimer’s disease (AD) to be effective. A major unmet need is to develop and validate sensitive measures to track disease progression in these populations. Objective: To generate novel statistically-derived composites from standard scores, which have increased sensitivity in the assessment of change from baseline in prodromal AD. Methods: An empirically based method was employed to generate domain specific, global, and cognitive-functional novel composites. The novel composites were compared and contrasted with each other, as well as standard scores for their ability to track change from baseline. The longitudinal characteristics and power to detect decline of the measures were evaluated. Data from participants in the Australian Imaging, Biomarkers and Lifestyle (AIBL) Study characterized as mild cognitively impaired with high neocortical amyloid-β burden were utilized for the study. Results: The best performing standard scores were CDR Sum-of-Boxes and MMSE. The statistically-derived novel composites performed better than the standard scores from which they were derived. The domain-specific composites generally did not perform as well as the global composites or the cognitive-functional composites. Conclusion: A systematic method was employed to generate novel statistically-derived composite measures from standard scores. Composites comprised of measures including function and multiple cognitive domains appeared to best capture change from baseline. These composites may be useful to assess progression or lack thereof in prodromal AD. However, the results should be replicated and validated using an independent clinical sample before implementation in a clinical trial.
Pages 1091-1101
Anna Bogstedt, Maria Groves, Keith Tan, Rajesh Narwal, Mary McFarlane, Kina Höglund
Development of Immunoassays for the Quantitative Assessment of Amyloid-β in the Presence of Therapeutic Antibody: Application to Pre-Clinical Studies
Abstract: Utilizing decision making biomarkers in drug development requires thorough assay validation. Special considerations need to be taken into account when monitoring biomarkers using immunoassays in the presence of therapeutic antibodies. We have developed robust and sensitive assays to assess target engagement and proof of mechanism to support the clinical progression of a human monoclonal antibody against the neurotoxic amyloid-β (Aβ)42 peptide. Here we present the introduction of novel pre-treatment steps to ensure drug-tolerant immunoassays and describe the validation of the complete experimental procedures to measure total Aβ42 concentration (bound and unbound) in cerebrospinal fluid (CSF) and plasma, free Aβ42 concentration (unbound) in CSF, and Aβ40 concentration in CSF. The difference in composition of the matrices (CSF and plasma) and antigen levels therein, in combination with the hydrophobic properties of Aβ protein, adds to the complexity of validation. Monitoring pharmacodynamics of an Aβ42 specific monoclonal antibody in a non-human primate toxicology study using these assays, we demonstrated a 1500-fold and a 3000-fold increase in total Aβ42 in plasma, a 4-fold and 8-fold increase in total Aβ42 in CSF together with a 95% and 96% reduction of free Aβ42 in CSF following weekly intravenous injections of 10 mg/kg and 100 mg/kg, respectively. Levels of Aβ40 were unchanged. The accuracy of these data is supported by previous pre-clinical studies as well as predictive pharmacokinetic/pharmacodynamics modeling. In contrast, when analyzing the same non-human primate samples excluding the pre-treatment steps, we were not able to distinguish between free and total Aβ42. Our data clearly demonstrate the importance of thorough evaluation of antibody interference and appropriate validation to monitor different types of biomarkers in the presence of a therapeutic antibody.
Pages 1103-1110
Wesley Jongbloed, Karin D. van Dijk, Sandra D. Mulder, Wilma D.J. van de Berg, Marinus A. Blankenstein, Wiesje van der Flier, Robert Veerhuis (Handling Associate Editor: Henrietta Nielsen)
Clusterin Levels in Plasma Predict Cognitive Decline and Progression to Alzheimer’s Disease
Abstract: Background. Increased clusterin levels have been reported in brain, cerebrospinal fluid (CSF), and plasma of Alzheimer’s disease (AD) patients. Because changes are also observed in mild cognitive impairment (MCI), a possible relationship between clusterin levels and early neurodegenerative changes in AD was suggested. Objectives. To determine whether clusterin concentrations could 1) serve as a diagnostic marker for AD, 2) predict disease progression in MCI, and 3) correlate with AD-biomarkers. Methods. Clusterin levels in CSF and plasma, as well as AD biomarker levels of Aβ42, Tau, and pTau in CSF and Mini-Mental State Examination scores (MMSE) were determined in 67 controls, 50 MCI, and 107 AD patients. Repeated MMSE was obtained for 44 MCI and 72 AD patients after, on average, 2.7 years. Results. Elevated clusterin concentrations in plasma, but not in CSF, were a risk factor for AD (HR 18.6; 95%CI 2.8-122), and related to cognitive decline in MCI (r=-0.38; p<0.01). An inverse relation between plasma clusterin levels and cognitive decline was observed in AD patients (r=0.23; p≤0.05). In CSF, but not in plasma, clusterin levels correlated with Tau and pTau in all groups. Conclusion. Elevated plasma clusterin levels in MCI confer an increased risk for progression to AD, and more rapid cognitive decline. We speculate that clusterin levels in CSF may reflect its involvement in the earliest neurodegenerative processes associated with AD pathology. Whereas neither clusterin levels in CSF nor in plasma had diagnostic value, plasma clusterin levels may serve as a prognostic marker for AD.
Pages 1111-1127
Meeting Report
Deborah R. Gustafson, Martha Clare Morris, Nikolaos Scarmeas, Raj C. Shah, John Sijben, Kristine Yaffe, Xiongwei Zhu
New Perspectives on Alzheimer’s Disease and Nutrition
Abstract: Accumulating evidence shows nutritional factors influence the risk of developing Alzheimer’s disease (AD) and its rate of clinical progression. Dietary and lifestyle guidelines to help adults reduce their risk have been developed. However, the clinical dementia picture remains complex, and further evidence is required to demonstrate that modifying nutritional status can protect the brain and prevent, delay, or reduce pathophysiological consequences of AD. Moreover, there is a pressing need for further research because of the global epidemic of overweight and obesity combined with longer life expectancy of the general population and generally observed decreases in body weight with aging and AD. A new research approach is needed, incorporating more sophisticated models to account for complex scenarios influencing the relationship between nutritional status and AD. Systematic research should identify and address evidence gaps. Integrating longitudinal epidemiological data with biomarkers of disease, including brain imaging technology, and randomized controlled interventions may provide greater insights into progressive and subtle neurological changes associated with dietary factors in individuals at risk for or living with AD. In addition, greater understanding of mechanisms involved in nutritional influences on AD risk and progression, such as oxidative stress and loss of neuronal membrane integrity, will better inform possible interventional strategies. There is consensus among the authors that nutritional deficits, and even states of excess, are associated with AD, but more work is needed to determine cause and effect. Appropriately designed diets or nutritional interventions may play a role, but additional research is needed on their clinical–cognitive effectiveness.
