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Kang K, Ko PW, Jin M, Suk K, Lee HW. Idiopathic normal-pressure hydrocephalus, cerebrospinal fluid biomarkers, and the cerebrospinal fluid tap test. J Clin Neurosci 2014; 21:1398-403. [PMID: 24836892 DOI: 10.1016/j.jocn.2013.11.039] [Citation(s) in RCA: 35] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/19/2013] [Revised: 09/29/2013] [Accepted: 11/13/2013] [Indexed: 12/17/2022]
Abstract
Cerebrospinal fluid (CSF) biomarkers, including soluble amyloid β-42 (Aβ-42) and phosphorylated-tau (P-tau), reflect core pathophysiological features of Alzheimer's disease (AD). AD is frequently a concomitant pathology in older patients with idiopathic normal-pressure hydrocephalus (iNPH), and somewhat similar altered CSF dynamics exist in both AD and iNPH. We therefore investigated relationships between lumbar CSF biomarkers Aβ-42 and P-tau and clinical parameters in iNPH patients, along with differences in these biomarkers between CSF tap test (CSFTT) responders and non-responders. Thirty-one iNPH patients (14 CSFTT responders and 17 CSFTT non-responders) were included in the final analysis. We found lower CSF Aβ-42 correlated with poor cognitive performance (r=0.687, p<0.001 for Korean Mini Mental State Examination; r=0.568, p=0.001 for Frontal Assessment Battery; r=-0.439, p=0.014 for iNPH grading scale [iNPHGS] cognitive score; r=-0.588, p=0.001 for Clinical Dementia Rating Scale), and lower CSF P-tau correlated with gait dysfunction (r=-0.624, p<0.001 for Timed Up and Go Test; r=-0.652, p<0.001 for 10meter walking test; r=-0.578, p=0.001 for Gait Status Scale; r=-0.543, p=0.002 for iNPHGS gait score). In subgroup analysis, CSF P-tau/Aβ-42 ratios were significantly higher in CSFTT non-responders compared to responders (p=0.027). Two conjectures are suggested. One, CSF biomarkers may play different and characteristic roles in relation to different iNPH symptoms such as cognition and gait. Two, comorbid AD pathology in iNPH patients may affect the response to the CSFTT. Larger studies using combinations of other biomarkers associated with AD would be necessary to evaluate these hypotheses.
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Affiliation(s)
- Kyunghun Kang
- Department of Neurology, Kyungpook National University School of Medicine, 50 Samdeok-dong 2-ga, Jung-gu, Daegu 700-721, South Korea
| | - Pan-Woo Ko
- Department of Neurology, Kyungpook National University School of Medicine, 50 Samdeok-dong 2-ga, Jung-gu, Daegu 700-721, South Korea
| | - Myungwon Jin
- Department of Pharmacology, Kyungpook National University School of Medicine, Daegu, South Korea; Brain Science & Engineering Institute, Kyungpook National University School of Medicine, Daegu, South Korea
| | - Kyoungho Suk
- Department of Pharmacology, Kyungpook National University School of Medicine, Daegu, South Korea; Brain Science & Engineering Institute, Kyungpook National University School of Medicine, Daegu, South Korea
| | - Ho-Won Lee
- Department of Neurology, Kyungpook National University School of Medicine, 50 Samdeok-dong 2-ga, Jung-gu, Daegu 700-721, South Korea; Brain Science & Engineering Institute, Kyungpook National University School of Medicine, Daegu, South Korea.
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102
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Forlenza OV, Diniz BS, Teixeira AL, Stella F, Gattaz W. Mild cognitive impairment. Part 2: Biological markers for diagnosis and prediction of dementia in Alzheimer's disease. BRAZILIAN JOURNAL OF PSYCHIATRY 2014; 35:284-94. [PMID: 24142092 DOI: 10.1590/1516-4446-2012-3505] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/08/2012] [Accepted: 09/08/2012] [Indexed: 11/21/2022]
Abstract
OBJECTIVE To present a critical review of publications reporting on the rationale and clinical implications of the use of biomarkers for the early diagnosis of Alzheimer's disease (AD). METHODS We conducted a systematic search of the PubMed and Web of Science electronic databases, limited to articles published in English between 1999 and 2012, and based on the following terms: mild cognitive impairment, Alzheimer's disease OR dementia, biomarkers. We retrieved 1,130 articles, of which 175 were reviews. Overall, 955 original articles were eligible. RESULTS The following points were considered relevant for the present review: a) rationale for biomarkers research in AD and mild cognitive impairment (MCI); b) usefulness of distinct biomarkers for the diagnosis and prediction of AD; c) the role of multimodality biomarkers for the diagnosis and prediction of AD; d) the role of biomarkers in clinical trials of patients with AD and MCI; and e) current limitations to the widespread use of biomarkers in research and clinical settings. CONCLUSION Different biomarkers are useful for the early diagnosis and prediction of AD in at-risk subjects. Nonetheless, important methodological limitations need to be overcome for widespread use of biomarkers in research and clinical settings.
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Affiliation(s)
- Orestes V Forlenza
- Universidade de São Paulo, Laboratory of Neuroscience, Department and Institute of Psychiatry, School of Medicine, São PauloSP, Brazil
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Blennow K, Dubois B, Fagan AM, Lewczuk P, de Leon MJ, Hampel H. Clinical utility of cerebrospinal fluid biomarkers in the diagnosis of early Alzheimer's disease. Alzheimers Dement 2014; 11:58-69. [PMID: 24795085 DOI: 10.1016/j.jalz.2014.02.004] [Citation(s) in RCA: 310] [Impact Index Per Article: 31.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/15/2013] [Revised: 02/09/2014] [Accepted: 02/11/2014] [Indexed: 12/11/2022]
Abstract
Several potential disease-modifying drugs for Alzheimer's disease (AD) have failed to show any effect on disease progression in clinical trials, conceivably because the AD subjects are already too advanced to derive clinical benefit from treatment and because diagnosis based on clinical criteria alone introduces a high misdiagnosis rate. Thus, well-validated biomarkers for early detection and accurate diagnosis are crucial. Low cerebrospinal fluid (CSF) concentrations of the amyloid-β (Aβ1-42) peptide, in combination with high total tau and phosphorylated tau, are sensitive and specific biomarkers highly predictive of progression to AD dementia in patients with mild cognitive impairment. However, interlaboratory variations in the results seen with currently available immunoassays are of concern. Recent worldwide standardization efforts and quality control programs include standard operating procedures for both preanalytical (e.g., lumbar puncture and sample handling) and analytical (e.g., preparation of calibration curve) procedures. Efforts are also ongoing to develop highly reproducible assays on fully automated instruments. These global standardization and harmonization measures will provide the basis for the generalized international application of CSF biomarkers for both clinical trials and routine clinical diagnosis of AD.
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Affiliation(s)
- Kaj Blennow
- Department of Neuroscience and Physiology, Clinical Neurochemistry Laboratory, Sahlgrenska University Hospital, University of Gothenburg, Mölndal, Sweden.
| | - Bruno Dubois
- Institute for Memory and Alzheimer's Disease, Institute of Neurology, Pitié-Salpêtrière Hospital Group, Pierre and Marie Curie University, Paris, France
| | - Anne M Fagan
- Department of Neurology, Washington University School of Medicine, St Louis, MO, USA
| | - Piotr Lewczuk
- Universitätsklinikum Erlangen and Friedrich-Alexander Universität Erlangen-Nürnberg, Erlangen, Germany
| | - Mony J de Leon
- Department of Psychiatry, New York University School of Medicine, New York, NY, USA; Centre for Brain Health, New York University School of Medicine, New York, NY, USA
| | - Harald Hampel
- Institute for Memory and Alzheimer's Disease, Institute of Neurology, Pitié-Salpêtrière Hospital Group, Pierre and Marie Curie University, Paris, France
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104
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Cerebrospinal fluid biomarkers of Alzheimer's disease. Neurosci Bull 2014; 30:233-42. [PMID: 24733653 DOI: 10.1007/s12264-013-1412-1] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/14/2013] [Accepted: 01/23/2014] [Indexed: 10/25/2022] Open
Abstract
Alzheimer's disease (AD) is a fatal neurodegenerative disorder that takes about a decade to develop, making early diagnosis possible. Clinically, the diagnosis of AD is complicated, costly, and inaccurate, so it is urgent to find specific biomarkers. Due to its multifactorial nature, a panel of biomarkers for the multiple pathologies of AD, such as cerebral amyloidogenesis, neuronal dysfunction, synapse loss, oxidative stress, and inflammation, are most promising for accurate diagnosis. Highly sensitive and high-throughput proteomic techniques can be applied to develop a panel of novel biomarkers for AD. In this review, we discuss the metabolism and diagnostic performance of the well-established core candidate cerebrospinal fluid (CSF) biomarkers (β-amyloid, total tau, and hyperphosphorylated tau). Meanwhile, novel promising CSF biomarkers, especially those identified by proteomics, updated in the last five years are also extensively discussed. Furthermore, we provide perspectives on how biomarker discovery for AD is evolving.
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105
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Morris JC, Blennow K, Froelich L, Nordberg A, Soininen H, Waldemar G, Wahlund LO, Dubois B. Harmonized diagnostic criteria for Alzheimer's disease: recommendations. J Intern Med 2014; 275:204-13. [PMID: 24605805 DOI: 10.1111/joim.12199] [Citation(s) in RCA: 88] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
BACKGROUND Two major sets of criteria for the clinical diagnosis of Alzheimer's disease (AD) recently have been published, one from an International Working Group (IWG) and the other from working groups convened by the National Institute on Aging (NIA) and the Alzheimer's Association (AA) in the United States. These criteria both aim to support a clinical diagnosis with in vivo evidence of AD pathology, using imaging methods and detection of biofluid biomarkers, and emphasize an aetiological diagnosis even in the prodromal stages of the disorder. Nonetheless, there are substantial differences in these two sets of criteria. METHODS An international group of investigators with experience in the clinical diagnosis of AD met at the Key Symposium in Stockholm, Sweden on 6 & 7 December 2012, to develop recommendations to harmonize these criteria. The group was led by individuals who were integral to the development of both the IWG and the NIA-AA criteria. The similarities and differences between the two sets of criteria were identified and open discussion focused on ways to resolve the differences and thus yield a harmonized set of criteria. RESULTS Based on both published evidence as well as the group's collective clinical experience, the group was tasked with achieving consensus, if not unanimity, as it developed recommendations for harmonized clinical diagnostic criteria for AD. CONCLUSION The recommendations are to: (i) define AD as a brain disorder, regardless of clinical status; (ii) refer to the clinically expressed disorder, including its prodromal stages, as symptomatic AD; (iii) after the successful completion of standardization efforts, consider incorporating biomarkers into diagnostic algorithms for AD; and (iv) allow nonamnestic, atypical presentations to be included as symptomatic AD, especially when there is supportive biomarker evidence.
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Affiliation(s)
- J C Morris
- Department of Neurology, Washington University, St. Louis, MO, USA
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Tosun D, Joshi S, Weiner MW. Multimodal MRI-based Imputation of the Aβ+ in Early Mild Cognitive Impairment. Ann Clin Transl Neurol 2014; 1:160-170. [PMID: 24729983 PMCID: PMC3981105 DOI: 10.1002/acn3.40] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/18/2023] Open
Abstract
Objective The primary goal of this study was to identify brain atrophy from structural MRI (magnetic resonance imaging) and cerebral blood flow (CBF) patterns from arterial spin labeling perfusion MRI that are best predictors of the Aβ-burden, measured as composite 18F-AV45-PET (positron emission tomography) uptake, in individuals with early mild cognitive impairment (MCI). Furthermore, another objective was to assess the relative importance of imaging modalities in classification of Aβ+/Aβ− early MCI. Methods Sixty-seven Alzheimer's Disease Neuroimaging Initiative (ADNI)-GO/2 participants with early MCI were included. Voxel-wise anatomical shape variation measures were computed by estimating the initial diffeomorphic mapping momenta from an unbiased control template. CBF measures normalized to average motor cortex CBF were mapped onto the template space. Using partial least squares regression, we identified the structural and CBF signatures of Aβ after accounting for normal cofounding effects of age, gender, and education. Results 18F-AV45-positive early MCIs could be identified with 83% classification accuracy, 87% positive predictive value, and 84% negative predictive value by multidisciplinary classifiers combining demographics data, ApoE ε4-genotype, and a multimodal MRI-based Aβ score. Interpretation Multimodal MRI can be used to predict the amyloid status of early-MCI individuals. MRI is a very attractive candidate for the identification of inexpensive and noninvasive surrogate biomarkers of Aβ deposition. Our approach is expected to have value for the identification of individuals likely to be Aβ+ in circumstances where cost or logistical problems prevent Aβ detection using cerebrospinal fluid analysis or Aβ-PET. This can also be used in clinical settings and clinical trials, aiding subject recruitment and evaluation of treatment efficacy. Imputation of the Aβ-positivity status could also complement Aβ-PET by identifying individuals who would benefit the most from this assessment.
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Affiliation(s)
- Duygu Tosun
- Department of Radiology and Biomedical Imaging, University of California - San Francisco, San Francisco, CA USA
| | - Sarang Joshi
- Scientific Computing and Imaging Institute, University of Utah, Salt Lake City, UT 84112, USA (72 S Central Campus Drive, Room 3750, Salt Lake City, UT 84112)
| | - Michael W Weiner
- Department of Radiology and Biomedical Imaging, University of California - San Francisco, San Francisco, CA USA
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Apostolova LG, Hwang KS, Kohannim O, Avila D, Elashoff D, Jack CR, Shaw L, Trojanowski JQ, Weiner MW, Thompson PM. ApoE4 effects on automated diagnostic classifiers for mild cognitive impairment and Alzheimer's disease. NEUROIMAGE-CLINICAL 2014; 4:461-72. [PMID: 24634832 PMCID: PMC3952354 DOI: 10.1016/j.nicl.2013.12.012] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 03/26/2013] [Revised: 12/24/2013] [Accepted: 12/24/2013] [Indexed: 01/30/2023]
Abstract
Biomarkers are the only feasible way to detect and monitor presymptomatic Alzheimer's disease (AD). No single biomarker can predict future cognitive decline with an acceptable level of accuracy. In addition to designing powerful multimodal diagnostic platforms, a careful investigation of the major sources of disease heterogeneity and their influence on biomarker changes is needed. Here we investigated the accuracy of a novel multimodal biomarker classifier for differentiating cognitively normal (NC), mild cognitive impairment (MCI) and AD subjects with and without stratification by ApoE4 genotype. 111 NC, 182 MCI and 95 AD ADNI participants provided both structural MRI and CSF data at baseline. We used an automated machine-learning classifier to test the ability of hippocampal volume and CSF Aβ, t-tau and p-tau levels, both separately and in combination, to differentiate NC, MCI and AD subjects, and predict conversion. We hypothesized that the combined hippocampal/CSF biomarker classifier model would achieve the highest accuracy in differentiating between the three diagnostic groups and that ApoE4 genotype will affect both diagnostic accuracy and biomarker selection. The combined hippocampal/CSF classifier performed better than hippocampus-only classifier in differentiating NC from MCI and NC from AD. It also outperformed the CSF-only classifier in differentiating NC vs. AD. Our amyloid marker played a role in discriminating NC from MCI or AD but not for MCI vs. AD. Neurodegenerative markers contributed to accurate discrimination of AD from NC and MCI but not NC from MCI. Classifiers predicting MCI conversion performed well only after ApoE4 stratification. Hippocampal volume and sex achieved AUC = 0.68 for predicting conversion in the ApoE4-positive MCI, while CSF p-tau, education and sex achieved AUC = 0.89 for predicting conversion in ApoE4-negative MCI. These observations support the proposed biomarker trajectory in AD, which postulates that amyloid markers become abnormal early in the disease course while markers of neurodegeneration become abnormal later in the disease course and suggests that ApoE4 could be at least partially responsible for some of the observed disease heterogeneity. Multimodal classifiers have better predictive power than unimodal classifier. ApoE4 significantly affects diagnostic discriminability in the MCI and dementia stages. Our data supports the hypothesized biomarker trajectory in AD.
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Key Words
- AD, Alzheimer's disease
- ADNI
- ADNI, Alzheimer's Disease Neuroimaging Initiative
- AUC, area under the curve
- Abeta
- Alzheimer's disease
- ApoE, apolipoprotein E
- Aβ, Amyloid beta
- Aβ42, Amyloid beta with 42 amino acid residues
- CSF, cerebrospinal fluid
- Diagnosis
- Hippocampus atrophy
- ICBM, International Consortium for Brain Mapping
- MCI, mild cognitive impairment
- MCIc, MCI converters
- MCInc, MCI nonconverters
- MMSE, Mini-Mental State Examination
- NC, normal control
- ROC, receiver operating curve
- SVM, support vector machine
- Tau
- p-tau, phosphorylated tau protein
- t-tau, total tau protein
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Affiliation(s)
- Liana G Apostolova
- Department of Neurology, David Geffen School of Medicine, UCLA, Los Angeles, CA, USA
| | - Kristy S Hwang
- Department of Neurology, David Geffen School of Medicine, UCLA, Los Angeles, CA, USA
| | - Omid Kohannim
- Imaging genetics Center, Institute for Neuroimaging and Informatics, University of Southern California, Los Angeles, CA, USA
| | - David Avila
- Department of Neurology, David Geffen School of Medicine, UCLA, Los Angeles, CA, USA
| | - David Elashoff
- Department of Medicine Statistics Core, UCLA, Los Angeles, CA, USA
| | - Clifford R Jack
- Department of Diagnostic Radiology, Mayo Clinic, Rochester, MN, USA
| | - Leslie Shaw
- Department of Pathology and Laboratory Medicine, University of Pennsylvania School of Medicine, Philadelphia, PA, USA
| | - John Q Trojanowski
- Department of Pathology and Laboratory Medicine, University of Pennsylvania School of Medicine, Philadelphia, PA, USA
| | - Michael W Weiner
- Department of Radiology, University of Pittsburgh, Pittsburgh, PA, USA ; Department of Veteran's Affairs Medical Center, San Francisco, CA, USA
| | - Paul M Thompson
- Imaging genetics Center, Institute for Neuroimaging and Informatics, University of Southern California, Los Angeles, CA, USA
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Koppel J, Greenwald BS. Optimal treatment of Alzheimer's disease psychosis: challenges and solutions. Neuropsychiatr Dis Treat 2014; 10:2253-62. [PMID: 25473289 PMCID: PMC4247130 DOI: 10.2147/ndt.s60837] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/28/2023] Open
Abstract
Psychotic symptoms emerging in the context of neurodegeneration as a consequence of Alzheimer's disease was recognized and documented by Alois Alzheimer himself in his description of the first reported case of the disease. Over a quarter of a century ago, in the context of attempting to develop prognostic markers of disease progression, psychosis was identified as an independent predictor of a more-rapid cognitive decline. This finding has been subsequently well replicated, rendering psychotic symptoms an important area of exploration in clinical history taking - above and beyond treatment necessity - as their presence has prognostic significance. Further, there is now a rapidly accreting body of research that suggests that psychosis in Alzheimer's disease (AD+P) is a heritable disease subtype that enjoys neuropathological specificity and localization. There is now hope that the elucidation of the neurobiology of the syndrome will pave the way to translational research eventuating in new treatments. To date, however, the primary treatments employed in alleviating the suffering caused by AD+P are the atypical antipsychotics. These agents are approved by the US Food and Drug Administration for the treatment of schizophrenia, but they have only marginal efficacy in treating AD+P and are associated with troubling levels of morbidity and mortality. For clinical approaches to AD+P to be optimized, this syndrome must be disentangled from other primary psychotic disorders, and recent scientific advances must be translated into disease-specific therapeutic interventions. Here we provide a review of atypical antipsychotic efficacy in AD+P, followed by an overview of critical neurobiological observations that point towards a frontal, tau-mediated model of disease, and we suggest a new preclinical animal model for future translational research.
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Affiliation(s)
- Jeremy Koppel
- The Feinstein Institute for Medical Research, North Shore-Long Island Jewish Health System, Manhasset, NY, USA ; Zucker Hillside Hospital, Hofstra North Shore-Long Island Jewish School of Medicine, Glen Oaks, NY, USA
| | - Blaine S Greenwald
- Zucker Hillside Hospital, Hofstra North Shore-Long Island Jewish School of Medicine, Glen Oaks, NY, USA
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Abstract
Knowledge of aging and dementia is rapidly evolving with the aim of identifying individuals in the earliest stages of disease processes. Biomarkers allow clinicians to show the presence of a pathologic process and resultant synapse dysfunction and neurodegeneration, even in the earliest stages. This article focuses on biomarkers for mild cognitive impairment caused by Alzheimer disease, structural magnetic resonance imaging, fluorodeoxyglucose positron emission tomography (PET) or single-photon emission computed tomography, and PET with dopamine ligands. Although these biomarkers are useful, several limitations exist. Several new biomarkers are emerging and a more biological characterization of underlying pathophysiologic spectra may become possible.
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Affiliation(s)
- Meredith Wicklund
- Fellow, Division of Behavioral Neurology, Department of Neurology, Mayo Clinic, Rochester, MN
| | - Ronald C. Petersen
- Cora Kanow Professor of Alzheimer's Disease Research, Director, Mayo Alzheimer's Disease Research Center, Division of Behavioral Neurology, Department of Neurology, Mayo Clinic, Rochester, MN
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110
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Moghekar A, Li S, Lu Y, Li M, Wang MC, Albert M, O'Brien R. CSF biomarker changes precede symptom onset of mild cognitive impairment. Neurology 2013; 81:1753-8. [PMID: 24132375 DOI: 10.1212/01.wnl.0000435558.98447.17] [Citation(s) in RCA: 75] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
Abstract
OBJECTIVE This study evaluated longitudinal CSF biomarker measures collected when participants were cognitively normal to determine the magnitude and time course of biomarker changes before the onset of clinical symptoms in subjects with mild cognitive impairment (MCI). METHODS Longitudinal CSF collection and cognitive assessments were performed on a cohort of 265 participants who were cognitively normal at their baseline assessment and subsequently developed MCI or dementia. CSF β-amyloid 1-42 (Aβ1-42), total tau (t-tau), and phosphorylated tau (p-tau) were determined longitudinally. Consensus diagnoses were completed annually. Cox regression analyses were performed, with baseline CSF values and time-dependent rate of change in CSF values as covariates (adjusted by baseline age, race, and education), in relation to time to onset of mild cognitive symptoms. RESULTS The mean time from baseline to onset of mild cognitive symptoms was 5.41 years. Increased risk of progressing from normal cognition to onset of clinical symptoms was associated with baseline values of Aβ1-42, p-tau, and the ratios of p-tau/Aβ1-42 and t-tau/Aβ1-42 (p < 0.002). Additionally, the rate of change in the ratios of t-tau/Aβ1-42 (p < 0.004) and p-tau/Aβ1-42 (p < 0.02) was greater among participants who were subsequently diagnosed with MCI. CONCLUSIONS Baseline differences in CSF values were predictive of clinical symptoms that were a harbinger of a diagnosis of MCI more than 5 years before symptom onset, and continue to show longitudinal changes as cognitive symptoms develop, demonstrating that baseline and longitudinal changes in CSF biomarkers are evident during the preclinical phase of Alzheimer disease.
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Affiliation(s)
- Abhay Moghekar
- From the Department of Neurology (A.M., M.L., M.A., R.O.), The Johns Hopkins University School of Medicine, Baltimore; and Department of Biostatistics (S.L., Y.L., M.-C.W.), Johns Hopkins Bloomberg School of Public Health, Baltimore, MD
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Abstract
PURPOSE OF REVIEW The term mild cognitive impairment (MCI) is used to describe older subjects with demonstrable cognitive impairment who have not crossed the threshold for dementia. Because patients with MCI have an increased risk of developing dementia, especially Alzheimer disease (AD), there is significant interest in the clinical characterization of these subjects and in understanding the pathophysiology of the transition from MCI to AD. RECENT FINDINGS The MCI syndrome, as an expression of an incipient disorder that may lead to dementia, is extremely heterogeneous and may coexist with systemic, neurologic, or psychiatric disorders that can cause cognitive deficits. Recent clinical criteria were designed to take into account the different forms of clinical presentation of the syndrome, and introduced the possible contribution of biomarkers to the clinical diagnosis. Bedside diagnosis of MCI can be difficult, since patients who report having cognitive problems may have normal scores in global cognitive scales or in brief neuropsychological instruments. SUMMARY This article presents the evolution of the clinical concept of MCI, the operationalization of its current definitions, the development of biomarkers that can help to identify an underlying neurodegenerative process as the etiology of the syndrome, and its proposed treatments.
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112
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Tosun D, Joshi S, Weiner MW. Neuroimaging predictors of brain amyloidosis in mild cognitive impairment. Ann Neurol 2013; 74:188-98. [PMID: 23686534 DOI: 10.1002/ana.23921] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/29/2012] [Revised: 04/22/2013] [Accepted: 04/24/2013] [Indexed: 01/24/2023]
Abstract
OBJECTIVE To identify a neuroimaging signature predictive of brain amyloidosis as a screening tool to identify individuals with mild cognitive impairment (MCI) that are most likely to have high levels of brain amyloidosis or to be amyloid-free. METHODS The prediction model cohort included 62 MCI subjects screened with structural magnetic resonance imaging (MRI) and (11) C-labeled Pittsburgh compound B positron emission tomography (PET). We identified an anatomical shape variation-based neuroimaging predictor of brain amyloidosis and defined a structural MRI-based brain amyloidosis score (sMRI-BAS). Amyloid beta positivity (Aβ(+) ) predictive power of sMRI-BAS was validated on an independent cohort of 153 MCI patients with cerebrospinal fluid Aβ1-42 biomarker data but no amyloid PET scans. We compared the Aβ(+) predictive power of sMRI-BAS to those of apolipoprotein E (ApoE) genotype and hippocampal volume, the 2 most relevant candidate biomarkers for the prediction of brain amyloidosis. RESULTS Anatomical shape variations predictive of brain amyloidosis in MCI embraced a characteristic spatial pattern known for high vulnerability to Alzheimer disease pathology, including the medial temporal lobe, temporal-parietal association cortices, posterior cingulate, precuneus, hippocampus, amygdala, caudate, and fornix/stria terminals. Aβ(+) prediction performance of sMRI-BAS and ApoE genotype jointly was significantly better than the performance of each predictor separately (area under the curve [AUC] = 0.88 vs AUC = 0.70 and AUC = 0.81, respectively) with >90% sensitivity and specificity at 20% false-positive rate and false-negative rate thresholds. Performance of hippocampal volume as an independent predictor of brain amyloidosis in MCI was only marginally better than random chance (AUC = 0.56). INTERPRETATION As one of the first attempts to use an imaging technique that does not require amyloid-specific radioligands for identification of individuals with brain amyloidosis, our findings could lead to development of multidisciplinary/multimodality brain amyloidosis biomarkers that are reliable, minimally invasive, and widely available.
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Affiliation(s)
- Duygu Tosun
- Department of Radiology and Biomedical Imaging, University of California, San Francisco, San Francisco, CA; Veterans Administration Medical Center, Center for Imaging of Neurodegenerative Diseases, San Francisco, CA
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Podlesniy P, Figueiro-Silva J, Llado A, Antonell A, Sanchez-Valle R, Alcolea D, Lleo A, Molinuevo JL, Serra N, Trullas R. Low cerebrospinal fluid concentration of mitochondrial DNA in preclinical Alzheimer disease. Ann Neurol 2013; 74:655-68. [PMID: 23794434 DOI: 10.1002/ana.23955] [Citation(s) in RCA: 154] [Impact Index Per Article: 14.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/09/2013] [Revised: 05/23/2013] [Accepted: 05/24/2013] [Indexed: 11/07/2022]
Abstract
OBJECTIVE To identify a novel biochemical marker that precedes clinical symptoms in Alzheimer disease (AD). METHODS Using quantitative polymerase chain reaction techniques, we measured circulating cell-free mitochondrial DNA (mtDNA) in cerebrospinal fluid (CSF) from study participants, selected from a cohort of 282 subjects, who were classified according to their concentrations of amyloid β1-42, total tau, and phosphorylated tau and by the presence or absence of dementia, into asymptomatic subjects at risk of AD, symptomatic patients diagnosed with sporadic AD, presymptomatic subjects carrying pathogenic PSEN1 mutations, and patients diagnosed with frontotemporal lobar degeneration (FTLD). We performed equivalent studies in a separate validation cohort of sporadic AD and FTLD patients. In addition, we measured mtDNA copy number in cultured cortical neurons from mutant amyloid precursor protein/presenilin1 (APP/PS1) transgenic mice. RESULTS Asymptomatic patients at risk of AD and symptomatic AD patients, but not FTLD patients, exhibit a significant decrease in circulating cell-free mtDNA in the CSF. These observations were confirmed in the validation cohort. In addition, presymptomatic subjects carrying pathogenic PSEN1 gene mutations show low mtDNA content in CSF before the appearance of AD-related biomarkers in CSF. Moreover, mtDNA content in CSF discriminates with high sensitivity and specificity AD patients from either controls or patients with FTLD. Furthermore, cultured cortical neurons from APP/PS1 transgenic mice have fewer mtDNA copies before the appearance of altered synaptic markers. INTERPRETATION Low content of mtDNA in CSF may be a novel biomarker for the early detection of preclinical AD. These findings support the hypothesis that mtDNA depletion is a characteristic pathophysiological factor of neurodegeneration in AD.
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Affiliation(s)
- Petar Podlesniy
- Neurobiology Unit, Instituto de Investigaciones Biomedicas de Barcelona, Consejo Superior de Investigaciones Cientificas, CSIC, Barcelona, Spain; Centro de Investigacion Biomedica en Red de Enfermedades Neurodegenerativas, CIBERNED, Madrid, Spain
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CSF biomarker associations with change in hippocampal volume and precuneus thickness: implications for the Alzheimer's pathological cascade. Brain Imaging Behav 2013; 6:599-609. [PMID: 22614327 DOI: 10.1007/s11682-012-9171-6] [Citation(s) in RCA: 36] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
Neurofibrillary tangles (NFT) and amyloid plaques are hallmark neuropathological features of Alzheimer's disease (AD). There is some debate as to which neuropathological feature comes first in the disease process, with early autopsy studies suggesting that NFT develop first, and more recent neuroimaging studies supporting the early role of amyloid beta (Aβ) deposition. Cerebrospinal fluid (CSF) biomarkers of Aβ₄₂ and hyperphosphorylated tau (p-tau) have been shown to serve as in vivo proxy measures of amyloid plaques and NFT, respectively. The aim of this study was to examine the association between CSF biomarkers and rate of atrophy in the precuneus and hippocampus. These regions were selected because the precuneus appears to be affected early and severely by Aβ deposition, and the hippocampus similarly by NFT pathology. We predicted (1) baseline Aβ₄₂ would be related to accelerated rate of cortical thinning in the precuneus and volume loss in the hippocampus, with the latter relationship expected to be weaker, (2) baseline p-tau(181p) would be related to accelerated rate of hippocampal atrophy and cortical thinning in the precuneus, with the latter relationship expected to be weaker. Using all ADNI cohorts, we fitted separate linear mixed-effects models for changes in hippocampus and precuneus longitudinal outcome measures with baseline CSF biomarkers modeled as predictors. Results partially supported our hypotheses: Both baseline p-tau(181p) and Aβ₄₂ were associated with hippocampal atrophy over time. Neither p-tau(181p) nor Aβ₄₂ were significantly related to cortical thinning in the precuneus over time. However, follow-up analyses demonstrated that having abnormal levels of both Aβ₄₂ and p-tau(181p) was associated with an accelerated rate of atrophy in both the hippocampus and precuneus. Results support early effects of Aβ in the Alzheimer's disease process, which are less apparent than and perhaps dependent on p-tau effects as the disease progresses. However, amyloid deposition alone may be insufficient for emergence of significant morphometric changes and clinical symptoms.
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CSF protein biomarkers predicting longitudinal reduction of CSF β-amyloid42 in cognitively healthy elders. Transl Psychiatry 2013; 3:e293. [PMID: 23962923 PMCID: PMC3756294 DOI: 10.1038/tp.2013.69] [Citation(s) in RCA: 42] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/26/2013] [Revised: 06/03/2013] [Accepted: 07/15/2013] [Indexed: 12/17/2022] Open
Abstract
β-amyloid (Aβ) plaque accumulation is a hallmark of Alzheimer's disease (AD). It is believed to start many years prior to symptoms and is reflected by reduced cerebrospinal fluid (CSF) levels of the peptide Aβ1-42 (Aβ42). Here we tested the hypothesis that baseline levels of CSF proteins involved in microglia activity, synaptic function and Aβ metabolism predict the development of Aβ plaques, assessed by longitudinal CSF Aβ42 decrease in cognitively healthy people. Forty-six healthy people with three to four serial CSF samples were included (mean follow-up 3 years, range 2-4 years). There was an overall reduction in Aβ42 from a mean concentration of 211-195 pg ml(-1) after 4 years. Linear mixed-effects models using longitudinal Aβ42 as the response variable, and baseline proteins as explanatory variables (n=69 proteins potentially relevant for Aβ metabolism, microglia or synaptic/neuronal function), identified 10 proteins with significant effects on longitudinal Aβ42. The most significant proteins were angiotensin-converting enzyme (ACE, P=0.009), Chromogranin A (CgA, P=0.009) and Axl receptor tyrosine kinase (AXL, P=0.009). Receiver-operating characteristic analysis identified 11 proteins with significant effects on longitudinal Aβ42 (largely overlapping with the proteins identified by linear mixed-effects models). Several proteins (including ACE, CgA and AXL) were associated with Aβ42 reduction only in subjects with normal baseline Aβ42, and not in subjects with reduced baseline Aβ42. We conclude that baseline CSF proteins related to Aβ metabolism, microglia activity or synapses predict longitudinal Aβ42 reduction in cognitively healthy elders. The finding that some proteins only predict Aβ42 reduction in subjects with normal baseline Aβ42 suggest that they predict future development of the brain Aβ pathology at the earliest stages of AD, prior to widespread development of Aβ plaques.
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Brunnström H, Hansson O, Zetterberg H, Londos E, Englund E. Correlations of CSF tau and amyloid levels with Alzheimer pathology in neuropathologically verified dementia with Lewy bodies. Int J Geriatr Psychiatry 2013; 28:738-44. [PMID: 22911491 DOI: 10.1002/gps.3881] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/19/2011] [Accepted: 08/02/2012] [Indexed: 11/11/2022]
Abstract
OBJECTIVE The presence of concomitant Alzheimer pathology has been linked to earlier death in cases with dementia with Lewy bodies (DLB). Recently, elevated cerebrospinal fluid (CSF) tau protein levels have been reported to be associated with shorter survival in clinically diagnosed DLB. Correlations between CSF biomarkers and neuropathological findings in DLB are missing. The aim of this study was to investigate correlations between CSF biomarker levels and histopathological findings, with a focus on concomitant Alzheimer pathology, in neuropathologically verified DLB cases. METHODS The extent of neurofibrillary pathology (Braak stage), neuritic plaques (CERAD stage), Alzheimer pathology (PPAD9 stage) and cerebral amyloid angiopathy was assessed in 16 cases with DLB in whom total tau (T-tau), hyperphosphorylated tau and amyloid beta 1-42 (Aβ42) protein levels in CSF had been analyzed in vivo. Demographic and clinical data were collected. RESULTS Both Braak and PPAD9 stages were inversely correlated with Aβ42 levels, whereas CERAD stage showed no significant correlations. Cerebral amyloid angiopathy correlated positively with T-tau and T-tau/Aβ42 ratio, and inversely with Aβ42 levels, but the group showed a very heterogeneous extent of cerebral amyloid angiopathy. CONCLUSIONS The burden of concomitant Alzheimer pathology correlates with CSF Aβ42 but not with T-tau levels in cases with neuropathologically defined DLB.
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Affiliation(s)
- Hans Brunnström
- Department of Pathology, Lund University and Regional Laboratories Region Skåne, Lund, Sweden.
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117
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Gaser C, Franke K, Klöppel S, Koutsouleris N, Sauer H. BrainAGE in Mild Cognitive Impaired Patients: Predicting the Conversion to Alzheimer's Disease. PLoS One 2013; 8:e67346. [PMID: 23826273 PMCID: PMC3695013 DOI: 10.1371/journal.pone.0067346] [Citation(s) in RCA: 325] [Impact Index Per Article: 29.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/18/2013] [Accepted: 05/16/2013] [Indexed: 01/21/2023] Open
Abstract
Alzheimer’s disease (AD), the most common form of dementia, shares many aspects of abnormal brain aging. We present a novel magnetic resonance imaging (MRI)-based biomarker that predicts the individual progression of mild cognitive impairment (MCI) to AD on the basis of pathological brain aging patterns. By employing kernel regression methods, the expression of normal brain-aging patterns forms the basis to estimate the brain age of a given new subject. If the estimated age is higher than the chronological age, a positive brain age gap estimation (BrainAGE) score indicates accelerated atrophy and is considered a risk factor for conversion to AD. Here, the BrainAGE framework was applied to predict the individual brain ages of 195 subjects with MCI at baseline, of which a total of 133 developed AD during 36 months of follow-up (corresponding to a pre-test probability of 68%). The ability of the BrainAGE framework to correctly identify MCI-converters was compared with the performance of commonly used cognitive scales, hippocampus volume, and state-of-the-art biomarkers derived from cerebrospinal fluid (CSF). With accuracy rates of up to 81%, BrainAGE outperformed all cognitive scales and CSF biomarkers in predicting conversion of MCI to AD within 3 years of follow-up. Each additional year in the BrainAGE score was associated with a 10% greater risk of developing AD (hazard rate: 1.10 [CI: 1.07–1.13]). Furthermore, the post-test probability was increased to 90% when using baseline BrainAGE scores to predict conversion to AD. The presented framework allows an accurate prediction even with multicenter data. Its fast and fully automated nature facilitates the integration into the clinical workflow. It can be exploited as a tool for screening as well as for monitoring treatment options.
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Affiliation(s)
- Christian Gaser
- Structural Brain Mapping Group, Department of Psychiatry, Jena University Hospital, Jena, Germany
- Department of Neurology, Jena University Hospital, Jena, Germany
| | - Katja Franke
- Structural Brain Mapping Group, Department of Psychiatry, Jena University Hospital, Jena, Germany
- * E-mail:
| | - Stefan Klöppel
- Department of Psychiatry and Psychotherapy, Department of Neurology, Freiburg Brain Imaging, University Medical Center Freiburg, Freiburg, Germany
| | - Nikolaos Koutsouleris
- Department of Psychiatry and Psychotherapy, Ludwig-Maximilians-University, Munich, Germany
| | - Heinrich Sauer
- Structural Brain Mapping Group, Department of Psychiatry, Jena University Hospital, Jena, Germany
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White MT, Xie SX. Adjustment for measurement error in evaluating diagnostic biomarkers by using an internal reliability sample. Stat Med 2013; 32:4709-25. [PMID: 23765915 DOI: 10.1002/sim.5878] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/21/2011] [Accepted: 05/18/2013] [Indexed: 11/07/2022]
Abstract
Biomarkers are often measured with error due to imperfect lab conditions or temporal variability within subjects. Using an internal reliability sample of the biomarker, we develop a parametric bias-correction approach for estimating a variety of diagnostic performance measures including sensitivity, specificity, the Youden index with its associated optimal cut-point, positive and negative predictive values, and positive and negative diagnostic likelihood ratios when the biomarker is subject to measurement error. We derive the asymptotic properties of the proposed likelihood-based estimators and show that they are consistent and asymptotically normally distributed. We propose confidence intervals for these estimators and confidence bands for the receiver operating characteristic curve. We demonstrate through extensive simulations that the proposed approach removes the bias due to measurement error and outperforms the naïve approach (which ignores the measurement error) in both point and interval estimation. We also derive the asymptotic bias of naïve estimates and discuss conditions in which naïve estimates of the diagnostic measures are biased toward estimates produced when the biomarker is ineffective (i.e., when sensitivity equals 1 - specificity) or are anticonservatively biased. The proposed method has broad biomedical applications and is illustrated using a biomarker study in Alzheimer's disease. We recommend collecting an internal reliability sample during the biomarker discovery phase in order to adequately evaluate the performance of biomarkers with careful adjustment for measurement error.
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Affiliation(s)
- Matthew T White
- Clinical Research Center, Boston Children's Hospital, Boston, MA 02115, U.S.A.; Department of Psychiatry, Harvard Medical School, Boston, MA 02215, U.S.A
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Wang LS, Leung YY, Chang SK, Leight S, Knapik-Czajka M, Baek Y, Shaw LM, Lee VMY, Trojanowski JQ, Clark CM. Comparison of xMAP and ELISA assays for detecting cerebrospinal fluid biomarkers of Alzheimer's disease. J Alzheimers Dis 2013; 31:439-45. [PMID: 22571982 DOI: 10.3233/jad-2012-120082] [Citation(s) in RCA: 53] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
The best-studied biomarkers of Alzheimer's disease (AD) are the pathologically-linked cerebrospinal fluid (CSF) proteins amyloid-β 42 (Aβ(1-42)), total tau (t-tau), and tau phosphorylated on amino acid 181 (p-tau(181)). Many laboratories measure these proteins using enzyme-linked immunosorbent assay (ELISA). Multiplex xMAP Luminex is a semi-automated assay platform with reduced intra-sample variance, which could facilitate its use in CLIA-approved clinical laboratories. CSF concentrations of these three biomarkers reported using xMAP technology differ from those measured by the most commonly used ELISA, confounding attempts to compare results. To develop a model for converting between xMAP and ELISA levels of the three biomarkers, we analyzed CSF samples from 140 subjects (59 AD, 30 controls, 34 with mild cognitive impairment, and 17 with Parkinson's disease, including 1 with dementia). Log-transformation of ELISA and xMAP levels made the variance constant in all three biomarkers and improved the linear regression: t-tau concentrations were highly correlated (r = 0.94); p-tau(181) concentrations by ELISA can be better predicted using both the t-tau and p-tau(181) xMAP values (r = 0.96) as compared to p-tau(181) concentrations alone (r = 0.82); correlation of Aβ(1-42) concentrations was relatively weaker but still high (r = 0.77). Among all six protein/assay combinations, xMAP Aβ(1-42) had the best accuracy for diagnostic classification (88%) between AD and control subjects. In conclusion, our study demonstrates that multiplex xMAP is an appropriate assay platform providing results that can be correlated with research-based ELISA values, facilitating the incorporation of this diagnostic biomarker into routine clinical practice.
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Affiliation(s)
- Li-San Wang
- Department of Pathology and Laboratory Medicine, University of Pennsylvania, Philadelphia, PA, USA.
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Babiloni C, Del Percio C, Bordet R, Bourriez JL, Bentivoglio M, Payoux P, Derambure P, Dix S, Infarinato F, Lizio R, Triggiani AI, Richardson JC, Rossini PM. Effects of acetylcholinesterase inhibitors and memantine on resting-state electroencephalographic rhythms in Alzheimer’s disease patients. Clin Neurophysiol 2013; 124:837-50. [DOI: 10.1016/j.clinph.2012.09.017] [Citation(s) in RCA: 54] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/15/2011] [Revised: 09/21/2012] [Accepted: 09/24/2012] [Indexed: 10/27/2022]
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Irwin DJ, Trojanowski JQ, Grossman M. Cerebrospinal fluid biomarkers for differentiation of frontotemporal lobar degeneration from Alzheimer's disease. Front Aging Neurosci 2013; 5:6. [PMID: 23440936 PMCID: PMC3578350 DOI: 10.3389/fnagi.2013.00006] [Citation(s) in RCA: 74] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/06/2013] [Accepted: 02/05/2013] [Indexed: 12/12/2022] Open
Abstract
Accurate ante mortem diagnosis in frontotemporal lobar degeneration (FTLD) is crucial to the development and implementation of etiology-based therapies. Several neurodegenerative disease-associated proteins, including the major protein constituents of inclusions in Alzheimer's disease (AD) associated with amyloid-beta (Aβ(1-42)) plaque and tau neurofibrillary tangle pathology, can be measured in cerebrospinal fluid (CSF) for diagnostic applications. Comparative studies using autopsy-confirmed samples suggest that CSF total-tau (t-tau) and Aβ(1-42) levels can accurately distinguish FTLD from AD, with a high t-tau to Aβ(1-42) ratio diagnostic of AD; however, there is also an urgent need for FTLD-specific biomarkers. These analytes will require validation in large autopsy-confirmed cohorts and face challenges of standardization of within- and between-laboratory sources of error. In addition, CSF biomarkers with prognostic utility and longitudinal study of CSF biomarker levels over the course of disease are also needed. Current goals in the field include identification of analytes that are easily and reliably measured and can be used alone or in a multi-modal approach to provide an accurate prediction of underlying neuropathology for use in clinical trials of disease modifying treatments in FTLD. To achieve these goals it will be of the utmost importance to view neurodegenerative disease, including FTLD, as a clinicopathological entity, rather than exclusively a clinical syndrome.
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Affiliation(s)
- David J Irwin
- Department of Pathology and Laboratory Medicine, Center for Neurodegenerative Disease Research, Alzheimer's Disease Core Center, Institute on Aging, University of Pennsylvania Philadelphia, PA, USA ; Department of Neurology, Center for Frontotemporal Dementia, Perelman School of Medicine, University of Pennsylvania Philadelphia, PA, USA
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Negash S, Xie S, Davatzikos C, Clark CM, Trojanowski JQ, Shaw LM, Wolk DA, Arnold SE. Cognitive and functional resilience despite molecular evidence of Alzheimer's disease pathology. Alzheimers Dement 2012; 9:e89-95. [PMID: 23127468 DOI: 10.1016/j.jalz.2012.01.009] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/05/2011] [Revised: 12/29/2011] [Accepted: 01/10/2012] [Indexed: 10/27/2022]
Abstract
BACKGROUND The correlation between neuropathological lesions and cognition is modest. Some individuals remain cognitively intact despite the presence of significant Alzheimer's disease (AD) pathology, whereas others manifest cognitive symptoms and dementia in the same context. The aim of the present study was to examine cognitive and cerebral reserve factors associated with resilient functioning in the setting of AD pathology. METHODS University of Pennsylvania Alzheimer's Disease Center research participants with biochemical biomarker evidence of AD pathology (cerebrospinal fluid amyloid-β1-42 <192 pg/mL) and comparable medial temporal lobe atrophy were categorized by Clinical Dementia Rating Scale-Sum of Boxes (CDR-SOB) score as AD dementia (CDR-SOB >1) or AD resilient (CDR-SOB ≤0.5). Groups were compared for a variety of demographic, clinical, and neuroimaging variables to identify factors that are associated with resilience to AD pathology. RESULTS A univariate model identified education and intracranial volume (ICV) as significant covariates. In a multivariate model with backward selection procedure, ICV was retained as a factor most significantly associated with resilience. The interaction term between ICV and education was not significant, suggesting that larger cranial vault size is associated with resilience even in the absence of more education. CONCLUSIONS Premorbid brain volume, as measured through ICV, provided protection against clinical manifestations of dementia despite evidence of significant accumulations of AD pathology. This finding provides support for the brain reserve hypothesis of resilience to AD.
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Affiliation(s)
- Selam Negash
- Department of Psychiatry, University of Pennsylvania, Philadelphia, PA, USA
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123
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Irwin DJ, McMillan CT, Toledo JB, Arnold SE, Shaw LM, Wang LS, Van Deerlin V, Lee VMY, Trojanowski JQ, Grossman M. Comparison of cerebrospinal fluid levels of tau and Aβ 1-42 in Alzheimer disease and frontotemporal degeneration using 2 analytical platforms. ACTA ACUST UNITED AC 2012; 69:1018-25. [PMID: 22490326 DOI: 10.1001/archneurol.2012.26] [Citation(s) in RCA: 89] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
OBJECTIVE To use values of cerebrospinal fluid tau and β-amyloid obtained from 2 different analytical immunoassays to differentiate Alzheimer disease (AD) from frontotemporal lobar degeneration (FTLD). DESIGN Cerebrospinal fluid values of total tau (T-tau) and β-amyloid 1-42 (Aβ 1-42) obtained using the Innotest enzyme-linked immunosorbent assay were transformed using a linear regression model to equivalent values obtained using the INNO-BIA AlzBio3 (xMAP; Luminex) assay. Cutoff values obtained from the xMAP assay were developed in a series of autopsy-confirmed cases and cross validated in another series of autopsy-confirmed samples using transformed enzyme-linked immunosorbent assay values to assess sensitivity and specificity for differentiating AD from FTLD. SETTING Tertiary memory disorder clinics and neuropathologic and biomarker core centers. PARTICIPANTS Seventy-five samples from patients with cerebrospinal fluid data obtained from both assays were used for transformation of enzyme-linked immunosorbent assay values. Forty autopsy-confirmed cases (30 with AD and 10 with FTLD) were used to establish diagnostic cutoff values and then cross validated in a second sample set of 21 autopsy-confirmed cases (11 with AD and 10 with FTLD) with transformed enzyme-linked immunosorbent assay values. MAIN OUTCOME MEASURE Diagnostic accuracy using transformed biomarker values. RESULTS Data obtained from both assays were highly correlated. The T-tau to Aβ 1-42 ratio had the highest correlation between measures (r = 0.928, P < .001) and high reliability of transformation (intraclass correlation coefficient= 0.89). A cutoff of 0.34 for the T-tau to Aβ 1-42 ratio had 90% and 100% sensitivity and 96.7% and 91% specificity to differentiate FTLD cases in the validation and cross-validation samples, respectively. CONCLUSIONS Values from 2 analytical platforms can be transformed into equivalent units, which can distinguish AD from FTLD more accurately than the clinical diagnosis.
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Affiliation(s)
- David J Irwin
- Center for Neurodegenerative Disease Research, Department of Pathology and Laboratory Medicine, Institute on Aging, Perelman School of Medicine, University of Pennsylvania, Philadelphia, USA
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Supporting evidence for using biomarkers in the diagnosis of MCI due to AD. J Neurol 2012; 260:640-50. [PMID: 23070466 DOI: 10.1007/s00415-012-6694-0] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/07/2012] [Revised: 09/24/2012] [Accepted: 09/26/2012] [Indexed: 01/02/2023]
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Saint-Aubert L, Puel M, Chollet F, Pariente J. [Early diagnosis of Alzheimer's disease]. Rev Neurol (Paris) 2012; 168:825-32. [PMID: 22989783 DOI: 10.1016/j.neurol.2012.07.006] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
INTRODUCTION Diagnosis of Alzheimer's disease (AD) remains difficult to establish, and can only be considered as certain thanks to anatomopathological evidence, or genetic mutations. Current diagnostic criteria rely on innovative imaging and biological tools, in order to detect pathological cues from very early stages, and with best sensibility and sensitivity. STATE OF ART Advances in neuro-imaging enabled the development of different tools to help establishing the diagnosis, such as cerebral atrophy assessment on magnetic resonance imaging (MRI), and cerebral metabolism study on positron emission tomography (PET). Besides, the increasing use of in vivo biological markers, combined to clinical criteria, enables to discriminate patients from healthy controls at even earlier stages. This includes studies on tau and beta-amyloid proteins concentrations in the cerebrosinal fluid, and amyloid-specific radioligands uptake. Familial forms of Alzheimer represent a great model for studying early or even pre-symptomatic AD, as genetic analyses constitute a diagnosis of certainty, even though they usually evolve earlier and faster. PERSPECTIVES, CONCLUSION Diagnostic tools are more and more numerous and performant. According to patients' clinical heterogeneity, it appears essential to associate different method to investigate, in order to make a diagnosis as early and as reliable as possible.
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Affiliation(s)
- L Saint-Aubert
- Inserm, imagerie cérébrale et handicaps neurologiques UMR 825, CHU Purpan, place du Docteur-Baylac, Toulouse cedex 9, France
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Abstract
Research progress has provided detailed understanding of the molecular pathogenesis of Alzheimer disease (AD). This knowledge has been translated into new drug candidates with putative disease-modifying effects, which are now being tested in clinical trials. The promise of effective therapy has created a great need for biomarkers able to detect AD in the predementia phase, because drugs will probably be effective only if neurodegeneration is not too advanced. In this chapter, cerebrospinal fluid (CSF) and plasma biomarkers are reviewed. The core CSF biomarkers total tau (T-tau), phosphorylated tau (P-tau) and the 42 amino acid form of β-amyloid (Aβ42) reflect AD pathology, and have high diagnostic accuracy to diagnose AD with dementia and prodromal AD in mild cognitive impairment cases. The rationale for the use of CSF biomarkers to identify and monitor the mechanism of action of new drug candidates is also outlined in this chapter.
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Affiliation(s)
- Kaj Blennow
- Clinical Neurochemistry Laboratory, Institute of Neuroscience and Physiology, Department of Psychiatry and Neurochemistry, The Sahlgrenska Academy at University of Gothenburg, Sahlgrenska University Hospital, Mölndal, SE-431 80 Mölndal, Sweden.
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Lahiri DK, Ray B. Abnormal cerebrospinal fluid (CSF) dynamics in Alzheimer's disease and normal pressure hydrocephalus: CSF-amyloid β precursor protein metabolites as possible biomarkers. Eur J Neurol 2012; 20:211-3. [DOI: 10.1111/j.1468-1331.2012.03832.x] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
| | - B. Ray
- Department of Psychiatry, Institute of Psychiatric Research; Indiana University School of Medicine; Indianapolis; IN; USA
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Pillai JA, McEvoy LK, Hagler DJ, Holland D, Dale AM, Salmon DP, Galasko D, Fennema-Notestine C. Higher education is not associated with greater cortical thickness in brain areas related to literacy or intelligence in normal aging or mild cognitive impairment. J Clin Exp Neuropsychol 2012; 34:925-35. [PMID: 22905705 DOI: 10.1080/13803395.2012.702733] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
Education may reduce risk of dementia through passive reserve, by increasing neural substrate. We tested the hypotheses that education is associated with thicker cortex and reduced rates of atrophy in brain regions related to literacy and intellectual ability. Healthy older adults and those with mild cognitive impairment were categorized into high (≥18 years) and low (≤13 years) education groups. Higher education was associated with thinner cortices in several areas, but one-year atrophy rates in these areas did not differ by education group. These results do not support a passive reserve model in which early-life education protects against dementia by increasing cortical thickness. Connectivity and synaptic efficiency or other lifestyle factors may more directly reflect cognitive reserve.
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Affiliation(s)
- Jagan A Pillai
- Department of Neurology, VA San Diego Medical Center, San Diego, CA, USA
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129
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Wu L, Rosa-Neto P, Gauthier S. Use of Biomarkers in Clinical Trials of Alzheimer Disease. Mol Diagn Ther 2012; 15:313-25. [DOI: 10.1007/bf03256467] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023]
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130
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Tang LL, Zhou XH. A semiparametric separation curve approach for comparing correlated ROC data from multiple markers. J Comput Graph Stat 2012; 21:662-676. [PMID: 23074360 DOI: 10.1080/10618600.2012.663303] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/28/2022]
Abstract
In this article we propose a separation curve method to identify the range of false positive rates for which two ROC curves differ or one ROC curve is superior to the other. Our method is based on a general multivariate ROC curve model, including interaction terms between discrete covariates and false positive rates. It is applicable with most existing ROC curve models. Furthermore, we introduce a semiparametric least squares ROC estimator and apply the estimator to the separation curve method. We derive a sandwich estimator for the covariance matrix of the semiparametric estimator. We illustrate the application of our separation curve method through two real life examples.
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131
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Hu WT, Holtzman DM, Fagan AM, Shaw LM, Perrin R, Arnold SE, Grossman M, Xiong C, Craig-Schapiro R, Clark CM, Pickering E, Kuhn M, Chen Y, Van Deerlin VM, McCluskey L, Elman L, Karlawish J, Chen-Plotkin A, Hurtig HI, Siderowf A, Swenson F, Lee VMY, Morris JC, Trojanowski JQ, Soares H. Plasma multianalyte profiling in mild cognitive impairment and Alzheimer disease. Neurology 2012; 79:897-905. [PMID: 22855860 DOI: 10.1212/wnl.0b013e318266fa70] [Citation(s) in RCA: 175] [Impact Index Per Article: 14.6] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022] Open
Abstract
OBJECTIVES While plasma biomarkers have been proposed to aid in the clinical diagnosis of Alzheimer disease (AD), few biomarkers have been validated in independent patient cohorts. Here we aim to determine plasma biomarkers associated with AD in 2 independent cohorts and validate the findings in the multicenter Alzheimer's Disease Neuroimaging Initiative (ADNI). METHODS Using a targeted proteomic approach, we measured levels of 190 plasma proteins and peptides in 600 participants from 2 independent centers (University of Pennsylvania, Philadelphia; Washington University, St. Louis, MO), and identified 17 analytes associated with the diagnosis of very mild dementia/mild cognitive impairment (MCI) or AD. Four analytes (apoE, B-type natriuretic peptide, C-reactive protein, pancreatic polypeptide) were also found to be altered in clinical MCI/AD in the ADNI cohort (n = 566). Regression analysis showed CSF Aβ42 levels and t-tau/Aβ42 ratios to correlate with the number of APOE4 alleles and plasma levels of B-type natriuretic peptide and pancreatic polypeptide. CONCLUSION Four plasma analytes were consistently associated with the diagnosis of very mild dementia/MCI/AD in 3 independent clinical cohorts. These plasma biomarkers may predict underlying AD through their association with CSF AD biomarkers, and the association between plasma and CSF amyloid biomarkers needs to be confirmed in a prospective study.
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Affiliation(s)
- William T Hu
- Department of Neurology, University of Pennsylvania School of Medicine, Philadelphia, USA.
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Abstract
Dementia due to Alzheimer's disease (AD) is estimated to reach epidemic proportions by the year 2030. Given the limited accuracy of current AD clinical diagnosis, biomarkers of AD pathologies are currently being sought. Reductions in cerebrospinal fluid levels of β-amyloid 42 (a marker of amyloid plaques) and elevations in tau species (markers of neurofibrillary tangles and/or neurodegeneration) are well-established as biomarkers useful for AD diagnosis and prognosis. However, novel markers for other features of AD pathophysiology (e.g., β-amyloid processing, neuroinflammation and neuronal stress/dysfunction) and for other non-AD dementias are required to improve the accuracy of AD disease diagnosis, prognosis, staging and therapeutic monitoring (theragnosis). This article discusses the potential of several promising novel cerebrospinal fluid analytes, highlights the next steps critical for advancement in the field, and provides a prediction on how the field may evolve in 5-10 years.
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Affiliation(s)
- Anne M Fagan
- Department of Neurology, Washington University School of Medicine, 660 South Euclid Ave., St Louis, MO 63110, USA.
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133
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Jack CR. Alzheimer disease: new concepts on its neurobiology and the clinical role imaging will play. Radiology 2012; 263:344-61. [PMID: 22517954 DOI: 10.1148/radiol.12110433] [Citation(s) in RCA: 150] [Impact Index Per Article: 12.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Alzheimer disease (AD) is one of, if not the most, feared diseases associated with aging. The prevalence of AD increases exponentially with age after 60 years. Increasing life expectancy coupled with the absence of any approved disease-modifying therapies at present position AD as a dominant public health problem. Major advances have occurred in the development of disease biomarkers for AD in the past 2 decades. At present, the most well-developed AD biomarkers are the cerebrospinal fluid analytes amyloid-β 42 and tau and the brain imaging measures amyloid positron emission tomography (PET), fluorodeoxyglucose PET, and magnetic resonance imaging. CSF and imaging biomarkers are incorporated into revised diagnostic guidelines for AD, which have recently been updated for the first time since their original formulation in 1984. Results of recent studies suggest the possibility of an ordered evolution of AD biomarker abnormalities that can be used to stage the typical 20-30-year course of the disease. When compared with biomarkers in other areas of medicine, however, the absence of standardized quantitative metrics for AD imaging biomarkers constitutes a major deficiency. Failure to move toward a standardized system of quantitative metrics has substantially limited potential diagnostic usefulness of imaging in AD. This presents an important opportunity that, if widely embraced, could greatly expand the application of imaging to improve clinical diagnosis and the quality and efficiency of clinical trials.
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Affiliation(s)
- Clifford R Jack
- Department of Radiology, Mayo Clinic and Foundation, Rochester, MN 55905, USA.
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134
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CSF biomarkers cutoffs: the importance of coincident neuropathological diseases. Acta Neuropathol 2012; 124:23-35. [PMID: 22526019 DOI: 10.1007/s00401-012-0983-7] [Citation(s) in RCA: 124] [Impact Index Per Article: 10.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/05/2012] [Revised: 04/07/2012] [Accepted: 04/08/2012] [Indexed: 12/13/2022]
Abstract
The effects of applying clinical versus neuropathological diagnosis and the inclusion of cases with coincident neuropathological diagnoses have not been assessed specifically when studying cerebrospinal fluid (CSF) biomarker classification cutoffs for patients with neurodegenerative diseases that cause dementia. Thus, 142 neuropathologically diagnosed neurodegenerative dementia patients [71 Alzheimer's disease (AD), 29 frontotemporal lobar degeneration (FTLD), 3 amyotrophic lateral sclerosis, 7 dementia with Lewy bodies, 32 of which cases also had coincident diagnoses] were studied. 96 % had enzyme-linked immunosorbant assay (ELISA) CSF data and 77 % had Luminex CSF data, with 43 and 46 controls for comparison, respectively. Aβ(42), total, and phosphorylated tau(181) were measured. Clinical and neuropathological diagnoses showed an 81.4 % overall agreement. Both assays showed high sensitivity and specificity to classify AD subjects against FTLD subjects and controls, and moderate sensitivity and specificity for classifying FTLD subjects against controls. However, among the cases with neuropathological diagnoses of AD plus another pathology (26.8 % of the sample), 69.4 % (ELISA) and 96.4 % (Luminex) were classified as AD according to their biomarker profiles. Use of clinical diagnosis instead of neuropathological diagnosis led to a 14-17 % underestimation of the biomarker accuracy. These results show that while CSF Aβ and tau assays are useful for diagnosis of AD and neurodegenerative diseases even at MCI stages, CSF diagnostic analyte panels that establish a positive diagnosis of Lewy body disease and FTLD are also needed, and must be established based on neuropathological rather than clinical diagnoses.
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135
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Panza F, Frisardi V, Solfrizzi V, Imbimbo BP, Logroscino G, Santamato A, Greco A, Seripa D, Pilotto A. Immunotherapy for Alzheimer's disease: from anti-β-amyloid to tau-based immunization strategies. Immunotherapy 2012; 4:213-38. [PMID: 22339463 DOI: 10.2217/imt.11.170] [Citation(s) in RCA: 100] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022] Open
Abstract
The exact mechanisms leading to Alzheimer's disease (AD) are largely unknown, limiting the identification of effective disease-modifying therapies. The two principal neuropathological hallmarks of AD are extracellular β-amyloid (Aβ), peptide deposition (senile plaques) and intracellular neurofibrillary tangles containing hyperphosphorylated tau protein. During the last decade, most of the efforts of the pharmaceutical industry were directed against the production and accumulation of Aβ. The most innovative of the pharmacological approaches was the stimulation of Aβ clearance from the brain of AD patients via the administration of Aβ antigens (active vaccination) or anti-Aβ antibodies (passive vaccination). Several active and passive anti-Aβ vaccines are under clinical investigation. Unfortunately, the first active vaccine (AN1792, consisting of preaggregate Aβ and an immune adjuvant, QS-21) was abandoned because it caused meningoencephalitis in approximately 6% of treated patients. Anti-Aβ monoclonal antibodies (bapineuzumab and solanezumab) are now being developed. The clinical results of the initial studies with bapineuzumab were equivocal in terms of cognitive benefit. The occurrence of vasogenic edema after bapineuzumab, and more rarely brain microhemorrhages (especially in Apo E ε4 carriers), has raised concerns on the safety of these antibodies directed against the N-terminus of the Aβ peptide. Solanezumab, a humanized anti-Aβ monoclonal antibody directed against the midregion of the Aβ peptide, was shown to neutralize soluble Aβ species. Phase II studies showed a good safety profile of solanezumab, while studies on cerebrospinal and plasma biomarkers documented good signals of pharmacodynamic activity. Although some studies suggested that active immunization may be effective against tau in animal models of AD, very few studies regarding passive immunization against tau protein are currently available. The results of the large, ongoing Phase III trials with bapineuzumab and solanezumab will tell us if monoclonal anti-Aβ antibodies may slow down the rate of deterioration of AD. Based on the new diagnostic criteria of AD and on recent major failures of anti-Aβ drugs in mild-to-moderate AD patients, one could argue that clinical trials on potential disease-modifying drugs, including immunological approaches, should be performed in the early stages of AD.
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Affiliation(s)
- Francesco Panza
- Geriatric Unit & Gerontology-Geriatric Research Laboratory, IRCCS Casa Sollievo della Sofferenza, Foggia, Italy.
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Tabaraud F, Leman JP, Milor AM, Roussie JM, Barrière G, Tartary M, Boutros-Toni F, Rigaud M. Alzheimer CSF biomarkers in routine clinical setting. Acta Neurol Scand 2012; 125:416-23. [PMID: 21954973 DOI: 10.1111/j.1600-0404.2011.01592.x] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
OBJECTIVES Our work was aimed to evaluate Alzheimer's disease diagnosis improvement using cerebrospinal fluid biomarkers (CSF) in neurological daily practice. MATERIALS AND METHODS For this purpose, 150 patients clinically and neurochemically classified as having AD or cognitive impairment with or without other dementia type were included in the study. The following CSF peptides were studied, blindly to the clinical diagnosis: beta-amyloid(1-42) peptide (Aβ(1-42)), Tau (T-tau), threonine-181 hyperphosphorylated tau protein (P-tau(181)), and beta-amyloid(1-40) peptide (Aβ(1-40)). From these measurements, Innotest® Amyloid Tau Index (IATI) was calculated for each patient. RESULTS This assessment allowed to separate 83 biochemical profiles of AD and 67 non-Alzheimer's disease (non-AD), both AD and non-AD categories match with clinical data amounting to 73% and 90%, respectively. Among mild cognitive impairment (MCI) patients, CSF biomarkers led to discriminate those who are likely to be AD. We devoted a special section to Aβ(1-40) which is not a routine parameter but can help to confirm a pathological amyloid process as Aβ(1-42)/Aβ(1-40) ratio underlining the real decline of the Aβ(1-42). CONCLUSIONS The interest of biomarkers and their ability to solve awkward cases were carefully noticed all the more when a discrepancy between clinical and CSF biological data was involved. The final proposed algorithm allowed to identify pathogenic forms of AD according to the prevailing role of hyperphosphorylated tau or amyloid beta peptide.
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Affiliation(s)
- F Tabaraud
- Clinical Center, Clinique du Colombier, Limoges, France
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Patel S, Lee EB, Xie SX, Law A, Jackson EM, Arnold SE, Clark CM, Shaw LM, Grady MS, Trojanowski JQ, Hamilton RH. Phosphorylated tau/amyloid beta 1-42 ratio in ventricular cerebrospinal fluid reflects outcome in idiopathic normal pressure hydrocephalus. Fluids Barriers CNS 2012; 9:7. [PMID: 22444461 PMCID: PMC3353832 DOI: 10.1186/2045-8118-9-7] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/23/2011] [Accepted: 03/23/2012] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND Idiopathic normal pressure hydrocephalus (iNPH) is a potentially reversible cause of dementia and gait disturbance that is typically treated by operative placement of a ventriculoperitoneal shunt. The outcome from shunting is variable, and some evidence suggests that the presence of comorbid Alzheimer's disease (AD) may impact shunt outcome. Evidence also suggests that AD biomarkers in cerebrospinal fluid (CSF) may predict the presence of AD. The aim of this study was to investigate the relationship between the phosphorylated tau/amyloid beta 1-42 (ptau/Aβ1-42) ratio in ventricular CSF and shunt outcome in patients with iNPH. METHODS We conducted a prospective trial with a cohort of 39 patients with suspected iNPH. Patients were clinically and psychometrically assessed prior to and approximately 4 months after ventriculoperitoneal shunting. Lumbar and ventricular CSF obtained intraoperatively, and tissue from intraoperative cortical biopsies were analyzed for AD biomarkers. Outcome measures included performance on clinical symptom scales, supplementary gait measures, and standard psychometric tests. We investigated relationships between the ptau/Aβ1-42 ratio in ventricular CSF and cortical AD pathology, initial clinical features, shunt outcome, and lumbar CSF ptau/Aβ1-42 ratios in the patients in our cohort. RESULTS We found that high ptau/Aβ1-42 ratios in ventricular CSF correlated with the presence of cortical AD pathology. At baseline, iNPH patients with ratio values most suggestive of AD presented with better gait performance but poorer cognitive performance. Patients with high ptau/Aβ1-42 ratios also showed a less robust response to shunting on both gait and cognitive measures. Finally, in a subset of 18 patients who also underwent lumbar puncture, ventricular CSF ratios were significantly correlated with lumbar CSF ratios. CONCLUSIONS Levels of AD biomarkers in CSF correlate with the presence of cortical AD pathology and predict aspects of clinical presentation in iNPH. Moreover, preliminary evidence suggests that CSF biomarkers of AD may prove useful for stratifying shunt prognosis in patients being evaluated and treated for this condition.
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Affiliation(s)
- Sunil Patel
- Department of Neurology, University of Pennsylvania School of Medicine, Philadelphia, PA 19104, USA.
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Reitz C. Evidence for an effect of single nucleotide polymorphisms in SORL1 on cerebrospinal fluid markers of Alzheimer’s disease. FUTURE NEUROLOGY 2012. [DOI: 10.2217/fnl.12.10] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Evaluation of: Alexopoulos P, Guo LH, Kratzer M, Westerteicher C, Kurz A, Perneczky R. Impact of SORL1 single nucleotide polymorphisms on Alzheimer’s disease cerebrospinal fluid markers. Dement. Geriatr. Cogn. Disord. 32, 164–170 (2011). This study explores the effect of previously reported SORL1 variants on cerebrospinal fluid (CSF) levels of Aβ1–42, phosphorylated tau181 and total tau in 100 nondemented people, 166 people with mild cognitive impairment and 87 people with probable Alzheimer’s disease. In individuals with Alzheimer’s disease, the A allele of single nucleotide polymorphism 23 and the T allele of single nucleotide polymorphism 24 were associated with lower CSF Aβ1–42, the latter association becoming marginally insignificant after correction for multiple testing. Both associations showed an interaction with the APOE genotype. There were no significant associations of SORL1 single nucleotide polymorphisms with CSF Aβ1–42 levels in the mild cognitive impairment group or with phosphorylated tau181 or total tau in any of the groups.
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Affiliation(s)
- Christiane Reitz
- The Taub Institute for Research on Alzheimer’s Disease & the Aging Brain, NY, USA and Gertrude H Sergievsky Center, 630 West 168th Street, Columbia University, New York, NY 10032, USA and The Department of Neurology, College of Physicians & Surgeons, Columbia University, New York, NY, USA
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Tosun D, Schuff N, Shaw LM, Trojanowski JQ, Weiner MW. Relationship between CSF biomarkers of Alzheimer's disease and rates of regional cortical thinning in ADNI data. J Alzheimers Dis 2012; 26 Suppl 3:77-90. [PMID: 21971452 DOI: 10.3233/jad-2011-0006] [Citation(s) in RCA: 38] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
Previously it was reported that Alzheimer's disease (AD) patients have reduced amyloid (Aβ 1-42) and elevated total tau (t-tau) and phosphorylated tau (p-tau 181p) in the cerebro-spinal fluid (CSF), suggesting that these same measures could be used to detect early AD pathology in healthy elderly (CN) and mild cognitive impairment (MCI). In this study, we tested the hypothesis that there would be an association among rates of regional brain atrophy, the CSF biomarkers Aβ 1-42, t-tau, and p-tau 181p and ApoE ε4 status, and that the pattern of this association would be diagnosis specific. Our findings primarily showed that lower CSF Aβ 1-42 and higher tau concentrations were associated with increased rates of regional brain tissue loss and the patterns varied across the clinical groups. Taken together, these findings demonstrate that CSF biomarker concentrations are associated with the characteristic patterns of structural brain changes in CN and MCI that resemble to a large extent the pathology seen in AD. Therefore, the finding of faster progression of brain atrophy in the presence of lower Aβ 1-42 levels and higher p-tau levels supports the hypothesis that CSF Aβ 1-42 and tau are measures of early AD pathology. Moreover, the relationship among CSF biomarkers, ApoE ε4 status, and brain atrophy rates are regionally varying, supporting the view that the genetic predisposition of the brain to amyloid and tau mediated pathology is regional and disease stage specific.
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Affiliation(s)
- Duygu Tosun
- Center for Imaging of Neurodegenerative Diseases, Department of Veterans Affairs Medical Center, San Francisco, CA 94121, USA.
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140
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Abstract
Alzheimer's disease (AD) is a chronic neurodegenerative disease with well-defined pathophysiological mechanisms, mostly affecting medial temporal lobe and associative neocortical structures. Neuritic plaques and neurofibrillary tangles represent the pathological hallmarks of AD, and are respectively related to the accumulation of the amyloid-beta peptide (Aβ) in brain tissues, and to cytoskeletal changes that arise from the hyperphosphorylation of microtubule-associated Tau protein in neurons. According to the amyloid hypothesis of AD, the overproduction of Aβ is a consequence of the disruption of homeostatic processes that regulate the proteolytic cleavage of the amyloid precursor protein (APP). Genetic, age-related and environmental factors contribute to a metabolic shift favoring the amyloidogenic processing of APP in detriment of the physiological, secretory pathway. Aβ peptides are generated by the successive cleavage of APP by beta-secretase (BACE-1) and gamma-secretase, which has been recently characterized as part of the presenilin complex. Among several beta-amyloid isoforms that bear subtle differences depending on the number of C-terminal amino acids, Aβ (1-42) plays a pivotal role in the pathogenesis of AD. The neurotoxic potential of the Aβ peptide results from its biochemical properties that favor aggregation into insoluble oligomers and protofibrils. These further originate fibrillary Aβ species that accumulate into senile and neuritic plaques. These processes, along with a reduction of Aβ clearance from the brain, leads to the extracellular accumulation of Aβ, and the subsequent activation of neurotoxic cascades that ultimately lead to cytoskeletal changes, neuronal dysfunction and cellular death. Intracerebral amyloidosis develops in AD patients in an age-dependent manner, but recent evidence indicate that it may be observed in some subjects as early as in the third or fourth decades of life, with increasing magnitude in late middle age, and highest estimates in old age. According to recent propositions, three clinical phases of Alzheimer's disease may be defined: (i) pre-symptomatic (or pre-clinical) AD, which may last for several years or decades until the overproduction and accumulation of Aβ in the brain reaches a critical level that triggers the amyloid cascade; (ii) pre-dementia phase of AD (compatible with the definition of progressive, amnestic mild cognitive impairment), in which early-stage pathology is present, ranging from mild neuronal dystrophy to early-stage Braak pathology, and may last for several years according to individual resilience and brain reserve; (iii) clinically defined dementia phase of AD, in which cognitive and functional impairment is severe enough to surmount the dementia threshold; at this stage there is significant accumulation of neuritic plaques and neurofibrillary tangles in affected brain areas, bearing relationship with the magnitude of global impairment. New technologies based on structural and functional neuroimaging, and on the biochemical analysis of cerebrospinal fluid may depict correlates of intracerebral amyloidosis in individuals with mild, pre-dementia symptoms. These methods are commonly referred to as AD-related biomarkers, and the combination of clinical and biological information yields good diagnostic accuracy to identify individuals at high risk of AD. In other words, the characterization of pathogenic Aβ by means of biochemical analysis of biological fluids or by molecular neuroimaging are presented as diagnostic tools to help identify AD cases at the earliest stages of the disease process. The relevance of this early diagnosis of AD relies on the hypothesis that pharmacological interventions with disease-modifying compounds are more likely to produce clinically relevant benefits if started early enough in the continuum towards dementia. Therapies targeting the modification of amyloid-related cascades may be viewed as promising strategies to attenuate or even to prevent dementia. Therefore, the cumulative knowledge on the pathogenesis of AD derived from basic science models will hopefully be translated into clinical practice in the forthcoming years.
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Affiliation(s)
- Vanessa J De-Paula
- Laboratory of Neuroscience (LIM 27), Department and Institute of Psychiatry, Faculty of Medicine, University of Sao Paulo, Rua Dr. Ovídio Pires de Campos 785, Terceiro Andar-Ala Norte, 05403-010, São Paulo-SP, Brazil,
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141
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Sojkova J, Resnick SM. In vivo human amyloid imaging. Curr Alzheimer Res 2011; 8:366-72. [PMID: 21222593 DOI: 10.2174/156720511795745375] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/20/2010] [Accepted: 12/22/2010] [Indexed: 11/22/2022]
Abstract
PET imaging agents such as Pittsburgh compound B (PiB) allow detection of fibrillar β-amyloid (Aβ) in vivo. In addition to quantification of Aβ deposition in mild cognitive impairment and Alzheimer's disease, PiB has also increased our understanding of Aβ deposition in older adults without cognitive impairment. In vivo Aβ deposition has been studied in relation to genotype, structural and functional brain changes, as well as alterations in biomarker levels. To date, several studies have reported changes in Aβ burden over time. This, together with investigation of the relationship between Aβ deposition and cognition, sets the stage for elucidation of the temporal sequence of the neurobiological events leading to cognitive decline. Furthermore, correlation of Aβ levels detected by PiB PET and those obtained from biopsy or postmortem specimens will allow more rigorous quantitative interpretation of PiB PET data in relation to neuropathological evaluation. Since the first human study in 2004, in vivo amyloid imaging has led to advances in our understanding of the role of Aβ deposition in human aging and cognitive decline, as well as provided new tools for patient selection and therapeutic monitoring in clinical trials.
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Affiliation(s)
- J Sojkova
- Laboratory of Personality and Cognition, NIH Biomedical Research Center, National Institute on Aging, IRP, Baltimore, MD 21224, USA
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Diversity and disparity in dementia: the impact of ethnoracial differences in Alzheimer disease. Alzheimer Dis Assoc Disord 2011; 25:187-95. [PMID: 21399486 DOI: 10.1097/wad.0b013e318211c6c9] [Citation(s) in RCA: 298] [Impact Index Per Article: 22.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
Debate exists regarding differences in the prevalence of Alzheimer disease (AD) in African Americans and Hispanics in the United States, with some evidence suggesting that the prevalence of AD may be considerably higher in these groups than in non-Hispanic whites. Despite this possible disparity, patients of minority ethnoracial groups often receive delayed diagnosis or inadequate treatment for dementia. This review investigates these disparities by conceptualizing the dementia disease process as a product of both biological and cultural factors. Ethnoracial differences in biological risk factors, such as genetics and cardiovascular disease, may help to explain disparities in the incidence and prevalence of AD, whereas race-specific cultural factors may impact diagnosis and treatment. Cultural factors include differences in perceptions about what is normal aging and what is not, lack of adequate access to medical care, and issues of trust between minority groups and the medical establishment. The diagnosis of AD in diverse populations may also be complicated by racial biases inherent in cognitive screening tools widely used by clinicians, but controlling for literacy level or using savings scores in psychometric analyses has the potential to mitigate these biases. We also suggest that emerging biomarker-based diagnostic tools may be useful in further characterizing diverse populations with AD. Recognizing the gap in communication that exists between minority communities and the medical research community, we propose that education and outreach are a critical next step in the effort to understand AD as it relates to diverse populations.
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Lopez OL, McDade E, Riverol M, Becker JT. Evolution of the diagnostic criteria for degenerative and cognitive disorders. Curr Opin Neurol 2011; 24:532-41. [PMID: 22071334 PMCID: PMC3268228 DOI: 10.1097/wco.0b013e32834cd45b] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
PURPOSE OF REVIEW This review describes the evolution of the clinical criteria for Alzheimer's disease over the past 25 years, with special emphasis on those recently published that have incorporated the use of biomarkers. RECENT FINDINGS One of the most important advances in the knowledge of Alzheimer's disease was the development of cerebrospinal fluid, PET and MRI biomarkers. These have shown that the Alzheimer's disease is present in cognitively normal individuals, suggesting that there is a long incubation process that precedes the onset of the symptoms. Although there are diagnostic criteria for Alzheimer's disease, the National Institute on Aging and the Alzheimer's Association has proposed a set of diagnostic criteria oriented to provide a unified vision of the pathological process from preclinical, to mild cognitive impairment, and to full-blown dementia. These new criteria take advantage of different biomarkers to support the clinical diagnosis of the different stages of the disease. SUMMARY The new guidelines provide a definition of the dementia syndrome and core diagnostic features to be used in research and clinical practice, although they caution about the use of biomarkers, since they still require validation, and the longitudinal interaction and dynamics of these biomarkers in relationship to the manifestation of the symptoms are not fully understood.
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Affiliation(s)
- Oscar L Lopez
- Department of Neurology, Alzheimer's Disease Research Center, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania 15213, USA
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Hampel H, Wilcock G, Andrieu S, Aisen P, Blennow K, Broich K, Carrillo M, Fox NC, Frisoni GB, Isaac M, Lovestone S, Nordberg A, Prvulovic D, Sampaio C, Scheltens P, Weiner M, Winblad B, Coley N, Vellas B. Biomarkers for Alzheimer's disease therapeutic trials. Prog Neurobiol 2011; 95:579-93. [PMID: 21130138 DOI: 10.1016/j.pneurobio.2010.11.005] [Citation(s) in RCA: 96] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/30/2010] [Revised: 11/10/2010] [Accepted: 11/22/2010] [Indexed: 11/26/2022]
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Roubaud-Baudron C, Krolak-Salmon P, Quadrio I, Mégraud F, Salles N. Impact of chronic Helicobacter pylori infection on Alzheimer's disease: preliminary results. Neurobiol Aging 2011; 33:1009.e11-9. [PMID: 22133280 DOI: 10.1016/j.neurobiolaging.2011.10.021] [Citation(s) in RCA: 92] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/21/2011] [Revised: 10/12/2011] [Accepted: 10/21/2011] [Indexed: 12/27/2022]
Abstract
Recent case-control studies reported an association between H. pylori infection and Alzheimer's disease (AD). Our aim was to compare cognitive impairment, neuroinflammation, and cerebrovascular lesion load in a group of AD patients according to their H. pylori status. For the 53 AD patients included, we assessed: clinical data (vascular comorbidities and cognitive assessment), biological data (especially fibrinogen, homocysteine levels, apolipoprotein E4 genotype; cerebrospinal fluid [CSF] total tau protein [Tau], phospho-tau(181) protein [pTau(181)]), and amyloid beta peptide levels, serum/CSF-cytokines (interleukin [IL]-1β, IL-6, IL-8, tumor necrosis factor [TNF]-α) and pepsinogen I/pepsinogen II (PgI/PgII) ratio, and cerebrovascular lesion load (magnetic resonance imaging [MRI] fluid-attenuated inversion recovery [FLAIR] with the Fazekas and Schmidt scale). H. pylori infection was diagnosed by enzyme-linked immunosorbent assay (ELISA) and immunoblot test. H. pylori infection was associated with a decreased Mini Mental State Examination (MMS) (p = 0.024), and higher CSF pTau(181) (p = 0.014) and tau (p = 0.021) levels. A decreased PgI/II ratio (i.e., an increased gastric atrophy) was associated with the infection (p = 0.005). Homocysteine levels were positively correlated to Fazekas score (r = 0.34; p = 0.032) and to H. pylori immunoglobulin (Ig)G levels (r = 0.44; p = 0.001). Higher CSF cytokine levels (IL-8, p = 0.003; TNF-α, p = 0.019) were associated with the infection, but systemic inflammation results were controversial. Finally, in multivariate analysis, a lower MMSE score (odds ratio [OR], 0.83 [0.72-0.97]; p = 0.017), plasma IL-1β level (OR, 0.31 [0.11-0.87]; p = 0.025), an increased gastric atrophy, i.e., a lower PgI/PgII ratio (OR, 0.63 [0.43-0.93]; p = 0.020) were still associated with the infection. AD patients infected by H. pylori tended to be more cognitively impaired. Studies are needed to attest to the impact of H. pylori infection on AD course, especially on cerebrovascular lesions and neuroinflammation.
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Jack CR, Vemuri P, Wiste HJ, Weigand SD, Aisen PS, Trojanowski JQ, Shaw LM, Bernstein MA, Petersen RC, Weiner MW, Knopman DS. Evidence for ordering of Alzheimer disease biomarkers. ARCHIVES OF NEUROLOGY 2011; 68:1526-35. [PMID: 21825215 PMCID: PMC3387980 DOI: 10.1001/archneurol.2011.183] [Citation(s) in RCA: 164] [Impact Index Per Article: 12.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
OBJECTIVE To empirically assess the concept that Alzheimer disease (AD) biomarkers significantly depart from normality in a temporally ordered manner. DESIGN Validation sample. SETTING Multisite, referral centers. PARTICIPANTS A total of 401 elderly participants in the Alzheimer's Disease Neuroimaging Initiative who were cognitively normal, who had mild cognitive impairment, or who had AD dementia. We compared the proportions of 3 AD biomarker values (the Aβ42 level in cerebrospinal fluid [CSF], the total tau level in CSF, and the hippocampal volume adjusted for intracranial volume [hereafter referred to as the adjusted hippocampal volume]) that were abnormal as cognitive impairment worsened. Cut points demarcating normal vs abnormal for each biomarker were established by maximizing diagnostic accuracy in independent autopsy samples. MAIN OUTCOME MEASURES Three AD biomarkers (ie, the CSF Aβ42 level, the CSF total tau level, and the adjusted hippocampal volume). RESULTS Within each clinical group of the entire sample (n = 401), the CSF Aβ42 level was abnormal more often than was the CSF total tau level or the adjusted hippocampal volume. Among the 298 participants with both baseline and 12-month data, the proportion of participants with an abnormal Aβ42 level did not change from baseline to 12 months in any group. The proportion of participants with an abnormal total tau level increased from baseline to 12 months in cognitively normal participants (P = .05) but not in participants with mild cognitive impairment or AD dementia. For 209 participants with an abnormal CSF Aβ42 level at baseline, the percentage with an abnormal adjusted hippocampal volume but normal CSF total tau level increased from baseline to 12 months in participants with mild cognitive impairment. No change in the percentage of MCI participants with an abnormal total tau level was seen between baseline and 12 months. CONCLUSIONS A reduction in the CSF Aβ42 level denotes a pathophysiological process that significantly departs from normality (ie, becomes dynamic) early, whereas the CSF total tau level and the adjusted hippocampal volume are biomarkers of downstream pathophysiological processes. The CSF total tau level becomes dynamic before the adjusted hippocampal volume, but the hippocampal volume is more dynamic in the clinically symptomatic mild cognitive impairment and AD dementia phases of the disease than is the CSF total tau level.
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Affiliation(s)
- Clifford R Jack
- Department of Radiology, Mayo Clinic and Mayo Foundation for Medical Education and Research, 200 First St, SW, Rochester, MN 55905, USA.
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Vlassenko AG, Benzinger TLS, Morris JC. PET amyloid-beta imaging in preclinical Alzheimer's disease. Biochim Biophys Acta Mol Basis Dis 2011; 1822:370-9. [PMID: 22108203 DOI: 10.1016/j.bbadis.2011.11.005] [Citation(s) in RCA: 110] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/24/2011] [Revised: 10/21/2011] [Accepted: 11/04/2011] [Indexed: 12/13/2022]
Abstract
Alzheimer's disease (AD) is the leading cause of dementia, accounting for 60-70% of all cases [Hebert et al., 2003, 1]. The need for effective therapies for AD is great. Current approaches, including cholinesterase inhibitors and N-methyl-d-aspartate (NMDA) receptor antagonists, are symptomatic treatments for AD but do not prevent disease progression. Many diagnostic and therapeutic approaches to AD are currently changing due to the knowledge that underlying pathology starts 10 to 20 years before clinical signs of dementia appear [Holtzman et al., 2011, 2]. New therapies which focus on prevention or delay of the onset or cognitive symptoms are needed. Recent advances in the identification of AD biomarkers now make it possible to detect AD pathology in the preclinical stage of the disease, in cognitively normal (CN) individuals; this biomarker data should be used in the selection of high-risk populations for clinical trials. In vivo visualization of AD neuropathology and biological, biochemical or physiological confirmation of the effects of treatment likely will substantially improve development of novel pharmaceuticals. Positron emission tomography (PET) is the leading neuroimaging tool to detect and provide quantitative measures of AD amyloid pathology in vivo at the early stages and follow its course longitudinally. This article is part of a Special Issue entitled: Imaging Brain Aging and Neurodegenerative disease.
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Affiliation(s)
- Andrei G Vlassenko
- Department of Radiology, Washington University School of Medicine, St. Louis, MO, USA
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148
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Fields JA, Ferman TJ, Boeve BF, Smith GE. Neuropsychological assessment of patients with dementing illness. Nat Rev Neurol 2011; 7:677-87. [PMID: 22045270 DOI: 10.1038/nrneurol.2011.173] [Citation(s) in RCA: 42] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
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149
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Castellano JM, Kim J, Stewart FR, Jiang H, DeMattos RB, Patterson BW, Fagan AM, Morris JC, Mawuenyega KG, Cruchaga C, Goate AM, Bales KR, Paul SM, Bateman RJ, Holtzman DM. Human apoE isoforms differentially regulate brain amyloid-β peptide clearance. Sci Transl Med 2011; 3:89ra57. [PMID: 21715678 DOI: 10.1126/scitranslmed.3002156] [Citation(s) in RCA: 822] [Impact Index Per Article: 63.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/02/2022]
Abstract
The apolipoprotein E (APOE) ε4 allele is the strongest genetic risk factor for late-onset, sporadic Alzheimer's disease (AD). The APOE ε4 allele markedly increases AD risk and decreases age of onset, likely through its strong effect on the accumulation of amyloid-β (Aβ) peptide. In contrast, the APOE ε2 allele appears to decrease AD risk. Most rare, early-onset forms of familial AD are caused by autosomal dominant mutations that often lead to overproduction of Aβ(42) peptide. However, the mechanism by which APOE alleles differentially modulate Aβ accumulation in sporadic, late-onset AD is less clear. In a cohort of cognitively normal individuals, we report that reliable molecular and neuroimaging biomarkers of cerebral Aβ deposition vary in an apoE isoform-dependent manner. We hypothesized that human apoE isoforms differentially affect Aβ clearance or synthesis in vivo, resulting in an apoE isoform-dependent pattern of Aβ accumulation later in life. Performing in vivo microdialysis in a mouse model of Aβ-amyloidosis expressing human apoE isoforms (PDAPP/TRE), we find that the concentration and clearance of soluble Aβ in the brain interstitial fluid depends on the isoform of apoE expressed. This pattern parallels the extent of Aβ deposition observed in aged PDAPP/TRE mice. ApoE isoform-dependent differences in soluble Aβ metabolism are observed not only in aged but also in young PDAPP/TRE mice well before the onset of Aβ deposition in amyloid plaques in the brain. Additionally, amyloidogenic processing of amyloid precursor protein and Aβ synthesis, as assessed by in vivo stable isotopic labeling kinetics, do not vary according to apoE isoform in young PDAPP/TRE mice. Our results suggest that APOE alleles contribute to AD risk by differentially regulating clearance of Aβ from the brain, suggesting that Aβ clearance pathways may be useful therapeutic targets for AD prevention.
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Affiliation(s)
- Joseph M Castellano
- Department of Neurology, Washington University School of Medicine, St. Louis, MO 63110, USA
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Shim YS, Morris JC. Biomarkers predicting Alzheimer's disease in cognitively normal aging. J Clin Neurol 2011; 7:60-8. [PMID: 21779293 PMCID: PMC3131540 DOI: 10.3988/jcn.2011.7.2.60] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/15/2010] [Revised: 01/31/2011] [Accepted: 01/31/2011] [Indexed: 02/07/2023] Open
Abstract
The pathophysiologic process of Alzheimer's disease (AD) begins years before the diagnosis of clinical dementia. This concept of preclinical AD has arisen from the observation of AD pathologic findings such as senile plaques and neurofibrillary tangles in the brains of people who at the time of death had normal cognitive function. Recent advances in biomarker studies now provide the ability to detect the pathologic changes of AD, which are antecedent to symptoms of the illness, in cognitively normal individuals. Functional and structural brain alterations that begin with amyloid-β accumulation already show the patterns of abnormality seen in individuals with dementia due to AD. The presence of preclinical AD provides a critical opportunity for potential interventions with disease-modifying therapy. This review focuses on the studies of antecedent biomarkers for preclinical AD.
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Affiliation(s)
- Yong S Shim
- Department of Neurology, Bucheon St. Mary's Hospital, The Catholic University of Korea College of Medicine, Bucheon, Korea
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