RESUMO
OBJECTIVE: The objective of this study was to evaluate novel plasma p-tau231 and p-tau181, as well as Aß40 and Aß42 assays as indicators of tau and Aß pathologies measured with positron emission tomography (PET), and their association with cognitive change, in cognitively unimpaired older adults. METHODS: In a cohort of 244 older adults at risk of Alzheimer's disease (AD) owing to a family history of AD dementia, we measured single molecule array (Simoa)-based plasma tau biomarkers (p-tau231 and p-tau181), Aß40 and Aß42 with immunoprecipitation mass spectrometry, and Simoa neurofilament light (NfL). A subset of 129 participants underwent amyloid-ß (18 F-NAV4694) and tau (18 F-flortaucipir) PET assessments. We investigated plasma biomarker associations with Aß and tau PET at the global and voxel level and tested plasma biomarker combinations for improved detection of Aß-PET positivity. We also investigated associations with 8-year cognitive change. RESULTS: Plasma p-tau biomarkers correlated with flortaucipir binding in medial temporal, parietal, and inferior temporal regions. P-tau231 showed further associations in lateral parietal and occipital cortices. Plasma Aß42/40 explained more variance in global Aß-PET binding than Aß42 alone. P-tau231 also showed strong and widespread associations with cortical Aß-PET binding. Combining Aß42/40 with p-tau231 or p-tau181 allowed for good distinction between Aß-negative and -positive participants (area under the receiver operating characteristic curve [AUC] range = 0.81-0.86). Individuals with low plasma Aß42/40 and high p-tau experienced faster cognitive decline. INTERPRETATION: Plasma p-tau231 showed more robust associations with PET biomarkers than p-tau181 in presymptomatic individuals. The combination of p-tau and Aß42/40 biomarkers detected early AD pathology and cognitive decline. Such markers could be used as prescreening tools to reduce the cost of prevention trials. ANN NEUROL 2022;91:548-560.
Assuntos
Doença de Alzheimer , Disfunção Cognitiva , Proteínas tau , Idoso , Doença de Alzheimer/diagnóstico , Peptídeos beta-Amiloides , Biomarcadores , Cognição , Disfunção Cognitiva/diagnóstico por imagem , Humanos , Tomografia por Emissão de Pósitrons , Proteínas tau/metabolismoRESUMO
In vitro studies of autosomal dominant Alzheimer's disease implicate longer amyloid-ß peptides in disease pathogenesis; however, less is known about the behaviour of these mutations in vivo. In this cross-sectional cohort study, we used liquid chromatography-tandem mass spectrometry to analyse 66 plasma samples from individuals who were at risk of inheriting a mutation or were symptomatic. We tested for differences in amyloid-ß (Aß)42:38, Aß42:40 and Aß38:40 ratios between presenilin 1 (PSEN1) and amyloid precursor protein (APP) carriers. We examined the relationship between plasma and in vitro models of amyloid-ß processing and tested for associations with parental age at onset. Thirty-nine participants were mutation carriers (28 PSEN1 and 11 APP). Age- and sex-adjusted models showed marked differences in plasma amyloid-ß between genotypes: higher Aß42:38 in PSEN1 versus APP (P < 0.001) and non-carriers (P < 0.001); higher Aß38:40 in APP versus PSEN1 (P < 0.001) and non-carriers (P < 0.001); while Aß42:40 was higher in both mutation groups compared to non-carriers (both P < 0.001). Amyloid-ß profiles were reasonably consistent in plasma and cell lines. Within the PSEN1 group, models demonstrated associations between Aß42:38, Aß42:40 and Aß38:40 ratios and parental age at onset. In vivo differences in amyloid-ß processing between PSEN1 and APP carriers provide insights into disease pathophysiology, which can inform therapy development.
Assuntos
Doença de Alzheimer/sangue , Doença de Alzheimer/genética , Peptídeos beta-Amiloides/sangue , Peptídeos beta-Amiloides/genética , Presenilina-1/sangue , Presenilina-1/genética , Adulto , Doença de Alzheimer/diagnóstico , Biomarcadores/sangue , Estudos de Coortes , Estudos Transversais , Feminino , Genótipo , Humanos , Células-Tronco Pluripotentes Induzidas/metabolismo , Estudos Longitudinais , Masculino , Pessoa de Meia-IdadeRESUMO
Alzheimer's disease has a preclinical stage when cerebral amyloid-ß deposition occurs before symptoms emerge, and when amyloid-ß-targeted therapies may have maximum benefits. Existing amyloid-ß status measurement techniques, including amyloid PET and CSF testing, are difficult to deploy at scale, so blood biomarkers are increasingly considered for screening. We compared three different blood-based techniques-liquid chromatography-mass spectrometry measures of plasma amyloid-ß, and single molecule array (Simoa) measures of plasma amyloid-ß and phospho-tau181-to detect cortical 18F-florbetapir amyloid PET positivity (defined as a standardized uptake value ratio of >0.61 between a predefined cortical region of interest and eroded subcortical white matter) in dementia-free members of Insight 46, a substudy of the population-based British 1946 birth cohort. We used logistic regression models with blood biomarkers as predictors of amyloid PET status, with or without age, sex and APOE ε4 carrier status as covariates. We generated receiver operating characteristics curves and quantified areas under the curves to compare the concordance of the different blood tests with amyloid PET. We determined blood test cut-off points using Youden's index, then estimated numbers needed to screen to obtain 100 amyloid PET-positive individuals. Of the 502 individuals assessed, 441 dementia-free individuals with complete data were included; 82 (18.6%) were amyloid PET-positive. The area under the curve for amyloid PET status using a base model comprising age, sex and APOE ε4 carrier status was 0.695 (95% confidence interval: 0.628-0.762). The two best-performing Simoa plasma biomarkers were amyloid-ß42/40 (0.620; 0.548-0.691) and phospho-tau181 (0.707; 0.646-0.768), but neither outperformed the base model. Mass spectrometry plasma measures performed significantly better than any other measure (amyloid-ß1-42/1-40: 0.817; 0.770-0.864 and amyloid-ß composite: 0.820; 0.775-0.866). At a cut-off point of 0.095, mass spectrometry measures of amyloid-ß1-42/1-40 detected amyloid PET positivity with 86.6% sensitivity and 71.9% specificity. Without screening, to obtain 100 PET-positive individuals from a population with similar amyloid PET positivity prevalence to Insight 46, 543 PET scans would need to be performed. Screening using age, sex and APOE ε4 status would require 940 individuals, of whom 266 would proceed to scan. Using mass spectrometry amyloid-ß1-42/1-40 alone would reduce these numbers to 623 individuals and 243 individuals, respectively. Across a theoretical range of amyloid PET positivity prevalence of 10-50%, mass spectrometry measures of amyloid-ß1-42/1-40 would consistently reduce the numbers proceeding to scans, with greater cost savings demonstrated at lower prevalence.
Assuntos
Doença de Alzheimer/sangue , Doença de Alzheimer/diagnóstico , Peptídeos beta-Amiloides/sangue , Fragmentos de Peptídeos/sangue , Idoso , Doença de Alzheimer/metabolismo , Biomarcadores/sangue , Diagnóstico Precoce , Feminino , Testes Hematológicos/métodos , Humanos , Masculino , Estudos Prospectivos , Sensibilidade e EspecificidadeRESUMO
INTRODUCTION: Reference materials based on human cerebrospinal fluid were certified for the mass concentration of amyloid beta (Aß)1-42 (Aß42 ). They are intended to be used to calibrate diagnostic assays for Aß42 . METHODS: The three certified reference materials (CRMs), ERM-DA480/IFCC, ERM-DA481/IFCC and ERM-DA482/IFCC, were prepared at three concentration levels and characterized using isotope dilution mass spectrometry methods. Roche, EUROIMMUN, and Fujirebio used the three CRMs to re-calibrate their immunoassays. RESULTS: The certified Aß42 mass concentrations in ERM-DA480/IFCC, ERM-DA481/IFCC, and ERM-DA482/IFCC are 0.45, 0.72, and 1.22 µg/L, respectively, with expanded uncertainties (k = 2) of 0.07, 0.11, and 0.18 µg/L, respectively. Before re-calibration, a good correlation (Pearson's r > 0.97), yet large biases, were observed between results from different commercial assays. After re-calibration the between-assay bias was reduced to < 5%. DISCUSSION: The Aß42 CRMs can ensure the equivalence of results between methods and across platforms for the measurement of Aß42 .
Assuntos
Peptídeos beta-Amiloides/líquido cefalorraquidiano , Imunoensaio/normas , Calibragem , Humanos , Imunoensaio/métodos , Padrões de ReferênciaRESUMO
Neurodegenerative dementias constitute a broad group of diseases in which abnormally folded proteins accumulate in specific brain regions and result in tissue reactions that eventually cause neuronal dysfunction and degeneration. Depending on where in the brain this happens, symptoms appear which may be used to classify the disorders on clinical grounds. However, brain changes in neurodegenerative dementias start to accumulate many years prior to symptom onset and there is a poor correlation between the clinical picture and what pathology that is the most likely to cause it. Thus, novel drug candidates having disease-modifying effects that is targeting the underlying pathology and changes the course of the disease needs to be defined using objective biomarker-based measures since the clinical symptoms are often non-specific and overlap between different disorders. Furthermore, the treatment should ideally be initiated as soon as symptoms are evident or when biomarkers confirm an underlying pathology (pre-clinical phase of the disease) to reduce irreversible damage to, for example, neurons, synapses and axons. Clinical trials in the pre-clinical phase bring a greater importance to biomarkers since by definition the clinical effects are difficult or slow to discern in a population that is not yet clinically affected. Here, we discuss neuropathological changes that may underlie neurodegenerative dementias, including how they can be detected and quantified using currently available biofluid-based biomarkers and how more of them could be identified using targeted proteomics approaches. This article is part of the special issue "Proteomics".
Assuntos
Demência , Doenças Neurodegenerativas , Proteômica/métodos , Peptídeos beta-Amiloides/sangue , Peptídeos beta-Amiloides/líquido cefalorraquidiano , Biomarcadores/sangue , Biomarcadores/líquido cefalorraquidiano , Proteínas de Ligação a DNA/sangue , Proteínas de Ligação a DNA/líquido cefalorraquidiano , Demência/metabolismo , Demência/patologia , Demência/fisiopatologia , Humanos , Doenças Neurodegenerativas/metabolismo , Doenças Neurodegenerativas/patologia , Doenças Neurodegenerativas/fisiopatologia , alfa-Sinucleína/sangue , alfa-Sinucleína/líquido cefalorraquidiano , Proteínas tau/sangue , Proteínas tau/líquido cefalorraquidianoRESUMO
BACKGROUND: The core Alzheimer's disease cerebrospinal fluid (CSF) biomarkers total tau (T-tau), phosphorylated tau (P-tau), ß-amyloid 1-42 (Aß42) and ß-amyloid 1-40 (Aß40) are increasing in importance and are now part of the research criteria for the diagnosis of the disease. The main aim of this study is to evaluate whether a set of certified reference materials (CRMs) are commutable for Aß42 and to serve as a feasibility study for the other markers. This property is a prerequisite for the establishment of CRMs which will then be used by manufacturers to calibrate their assays against. Once the preanalytical factors have been standardized and proper selection criteria are available for subject cohorts this harmonization between methods will allow for universal cut-offs to be determined. METHODS: Thirty-four individual CSF samples and three different CRMs where analyzed for T-tau, P-tau, Aß42 and Aß40, using up to seven different commercially available methods. For Aß40 and Aß42 a mass spectrometry-based procedure was also employed. RESULTS: There were strong pairwise correlations between the different methods (Spearman's ρ>0.92) for all investigated analytes and the CRMs were not distinguishable from the individual samples. CONCLUSIONS: This study shows that the CRMs are commutable for the different assays for Aß42. For the other analytes the results show that it would be feasible to also produce CRMs for these. However, additional studies are needed as the concentration interval for the CRMs were selected based on Aß42 concentrations only and did in general not cover satisfactory large concentration intervals for the other analytes.
Assuntos
Peptídeos beta-Amiloides/líquido cefalorraquidiano , Imunoensaio/normas , Fragmentos de Peptídeos/líquido cefalorraquidiano , Proteínas tau/líquido cefalorraquidiano , Biomarcadores/líquido cefalorraquidiano , Humanos , Padrões de ReferênciaRESUMO
INTRODUCTION: Alzheimer's disease (AD) is a neurodegenerative disease affecting the brain. Today there are three cerebrospinal fluid (CSF) biomarkers, amyloid-ß consisting of 42 amino acids (Aß42), total-tau (t-tau) and phosphorylated-tau (p-tau), which combined have sensitivity and specificity figures around 80%. However, pathological studies have shown that comorbidity is a common feature in AD and that the three currently used CSF biomarkers do not optimally reflect the activity of the disease process. Thus, additional markers are needed. Areas covered: In the present review, we screened PubMed for articles published the last five years (2012-2017) for proteomic studies in CSF with the criteria that AD had to be included as one of the diagnostic groups. Based on inclusion criteria, 28 papers were included reporting in total 224 biomarker-data that were altered in AD compared to control. Both mass spectrometry and multi-panel immunoassays were considered as proteomic studies. Expert commentary: A large number of pilot studies have been reported but so far there is a lack of replicated findings and to date no CSF biomarker discovered in proteomic studies has reached the clinic to aid in the diagnostic work-up of patients with cognitive impairment.
Assuntos
Doença de Alzheimer/líquido cefalorraquidiano , Peptídeos beta-Amiloides/líquido cefalorraquidiano , Proteômica , Proteínas tau/líquido cefalorraquidiano , Biomarcadores/líquido cefalorraquidiano , Humanos , Imunoensaio , Espectrometria de Massas , Sensibilidade e EspecificidadeRESUMO
The aim of this study was to assess the agreement between data on cerebral amyloidosis, derived using Pittsburgh compound B positron emission tomography and (i) multi-laboratory INNOTEST enzyme linked immunosorbent assay derived cerebrospinal fluid concentrations of amyloid-ß42; (ii) centrally measured cerebrospinal fluid amyloid-ß42 using a Meso Scale Discovery enzyme linked immunosorbent assay; and (iii) cerebrospinal fluid amyloid-ß42 centrally measured using an antibody-independent mass spectrometry-based reference method. Moreover, we examined the hypothesis that discordance between amyloid biomarker measurements may be due to interindividual differences in total amyloid-ß production, by using the ratio of amyloid-ß42 to amyloid-ß40 Our study population consisted of 243 subjects from seven centres belonging to the Biomarkers for Alzheimer's and Parkinson's Disease Initiative, and included subjects with normal cognition and patients with mild cognitive impairment, Alzheimer's disease dementia, frontotemporal dementia, and vascular dementia. All had Pittsburgh compound B positron emission tomography data, cerebrospinal fluid INNOTEST amyloid-ß42 values, and cerebrospinal fluid samples available for reanalysis. Cerebrospinal fluid samples were reanalysed (amyloid-ß42 and amyloid-ß40) using Meso Scale Discovery electrochemiluminescence enzyme linked immunosorbent assay technology, and a novel, antibody-independent, mass spectrometry reference method. Pittsburgh compound B standardized uptake value ratio results were scaled using the Centiloid method. Concordance between Meso Scale Discovery/mass spectrometry reference measurement procedure findings and Pittsburgh compound B was high in subjects with mild cognitive impairment and Alzheimer's disease, while more variable results were observed for cognitively normal and non-Alzheimer's disease groups. Agreement between Pittsburgh compound B classification and Meso Scale Discovery/mass spectrometry reference measurement procedure findings was further improved when using amyloid-ß42/40 Agreement between Pittsburgh compound B visual ratings and Centiloids was near complete. Despite improved agreement between Pittsburgh compound B and centrally analysed cerebrospinal fluid, a minority of subjects showed discordant findings. While future studies are needed, our results suggest that amyloid biomarker results may not be interchangeable in some individuals.
Assuntos
Peptídeos beta-Amiloides/metabolismo , Compostos de Anilina , Biomarcadores/metabolismo , Disfunção Cognitiva/metabolismo , Demência/metabolismo , Tiazóis , Idoso , Peptídeos beta-Amiloides/líquido cefalorraquidiano , Biomarcadores/líquido cefalorraquidiano , Disfunção Cognitiva/líquido cefalorraquidiano , Disfunção Cognitiva/diagnóstico por imagem , Demência/líquido cefalorraquidiano , Demência/diagnóstico por imagem , Ensaio de Imunoadsorção Enzimática , Europa (Continente) , Feminino , Humanos , Masculino , Espectrometria de Massas , Pessoa de Meia-Idade , Fragmentos de Peptídeos/líquido cefalorraquidiano , Tomografia por Emissão de PósitronsRESUMO
A clinical diagnosis of Alzheimer's disease is currently made on the basis of results from cognitive tests in combination with medical history and general clinical evaluation, but the peptide amyloid-beta (Aß) in cerebrospinal fluid (CSF) is increasingly used as a biomarker for amyloid pathology in clinical trials and in recently proposed revised clinical criteria for Alzheimer's disease. Recent analytical developments have resulted in mass spectrometry (MS) reference measurement procedures for absolute quantification of Aß1-42 in CSF. The CSF Aß1-42 /Aß1-40 ratio has been suggested to improve the detection of cerebral amyloid deposition, by compensating for inter-individual variations in total Aß production. Our aim was to cross-validate the reference measurement procedure as well as the Aß1-42 /Aß1-40 and Aß1-42 /Aß1-38 ratios in CSF, measured by high-resolution MS, with the cortical level of Aß fibrils as measured by amyloid (18 F-flutemetamol) positron emission tomography (PET). We included 100 non-demented patients with cognitive symptoms from the Swedish BioFINDER study, all of whom had undergone both lumbar puncture and 18 F-flutemetamol PET. Comparing CSF Aß1-42 concentrations with 18 F-flutemetamol PET showed high concordance with an area under the receiver operating characteristic curve of 0.85 and a sensitivity and specificity of 82% and 81%, respectively. The ratio of Aß1-42 /Aß1-40 or Aß1-42 /Aß1-38 significantly improved concordance with an area under the receiver operating characteristic curve of 0.95 and a sensitivity and specificity of 96% and 91%, respectively. These results show that the CSF Aß1-42 /Aß1-40 and Aß1-42 /Aß1-38 ratios using the described MS method are strongly associated with cortical Aß fibrils measured by 18 F-flutemetamol PET.
Assuntos
Doença de Alzheimer/líquido cefalorraquidiano , Doença de Alzheimer/diagnóstico por imagem , Peptídeos beta-Amiloides/líquido cefalorraquidiano , Amiloide/líquido cefalorraquidiano , Fragmentos de Peptídeos/líquido cefalorraquidiano , Tomografia por Emissão de Pósitrons , Doença de Alzheimer/epidemiologia , Biomarcadores/líquido cefalorraquidiano , Humanos , Estudos Longitudinais , Estudos Prospectivos , Padrões de Referência , Suécia/epidemiologiaRESUMO
BACKGROUND: The cerebrospinal fluid (CSF) amyloid-ß (Aß42) peptide is an important biomarker for Alzheimer's disease (AD). Variability in measured Aß42 concentrations at different laboratories may be overcome by standardization and establishing traceability to a reference system. Candidate certified reference materials (CRMs) are validated herein for this purpose. METHODS: Commutability of 16 candidate CRM formats was assessed across five CSF Aß42 immunoassays and one mass spectrometry (MS) method in a set of 48 individual clinical CSF samples. Promising candidate CRM formats (neat CSF and CSF spiked with Aß42) were identified and subjected to validation across eight (Elecsys, EUROIMMUN, IBL, INNO-BIA AlzBio3, INNOTEST, MSD, Simoa, and Saladax) immunoassays and the MS method in 32 individual CSF samples. Commutability was evaluated by Passing-Bablok regression and the candidate CRM termed commutable when found within the prediction interval (PI). The relative distance to the regression line was assessed. RESULTS: The neat CSF candidate CRM format was commutable for almost all method comparisons, except for the Simoa/MSD, Simoa/MS and MS/IBL where it was found just outside the 95% PI. However, the neat CSF was found within 5% relative distance to the regression line for MS/IBL, between 5% and 10% for Simoa/MS and between 10% and 15% for Simoa/MSD comparisons. CONCLUSIONS: The neat CSF candidate CRM format was commutable for 33 of 36 method comparisons, only one comparison more than expected given the 95% PI acceptance limit. We conclude that the neat CSF candidate CRM can be used for value assignment of the kit calibrators for the different Aß42 methods.
Assuntos
Peptídeos beta-Amiloides/líquido cefalorraquidiano , Biomarcadores/líquido cefalorraquidiano , Imunoensaio/normas , Humanos , Limite de Detecção , Padrões de Referência , Espectrometria de Massas em TandemRESUMO
INTRODUCTION: Cerebrospinal fluid (CSF) amyloid-ß 1-42 (Aß42) is an important biomarker for Alzheimer's disease, both in diagnostics and to monitor disease-modifying therapies. However, there is a great need for standardization of methods used for quantification. To overcome problems associated with immunoassays, liquid chromatography-tandem mass spectrometry (LC-MS/MS) has emerged as a critical orthogonal alternative. METHODS: We compared results for CSF Aß42 quantification in a round robin study performed in four laboratories using similar sample preparation methods and LC-MS instrumentation. RESULTS: The LC-MS results showed excellent correlation between laboratories (r(2) >0.98), high analytical precision, and good correlation with enzyme-linked immunosorbent assay (r(2) >0.85). The use of a common reference sample further decreased interlaboratory variation. DISCUSSION: Our results indicate that LC-MS is suitable for absolute quantification of Aß42 in CSF and highlight the importance of developing a certified reference material.
Assuntos
Peptídeos beta-Amiloides/líquido cefalorraquidiano , Biomarcadores/líquido cefalorraquidiano , Cromatografia Líquida/métodos , Fragmentos de Peptídeos/líquido cefalorraquidiano , Espectrometria de Massas em Tandem/métodos , Doença de Alzheimer/líquido cefalorraquidiano , Calibragem , Ensaio de Imunoadsorção Enzimática/normas , Humanos , Padrões de ReferênciaRESUMO
BACKGROUND: Cerebrospinal fluid (CSF) amyloid-ß (Aß42) is a well-established biomarker for Alzheimer disease. Several immunoassays for Aß42 exist but differ in absolute concentrations and may suffer from matrix interference, thereby hampering interlaboratory comparisons and the use of general cutoff levels. Together with the IFCC Working Group on CSF Proteins, we developed a candidate reference measurement procedure (RMP) for Aß42. METHODS: The antibody-independent candidate RMP was based on solid-phase extraction and isotope-dilution LC-MS/MS. The candidate RMP used 2 differently stable isotope-labeled Aß42 peptides for calibration in human CSF, an important aspect since there was no analyte-free matrix available. Because no CSF certified reference material (CRM) exists, we used a nonlabeled Aß42 standard, the concentration of which was determined by amino acid analysis. We performed measurements on a high-resolution quadrupole-Orbitrap hybrid instrument. The results were compared with a method run in a second laboratory with triple quadrupole instrumentation. RESULTS: The candidate RMP allowed quantification of CSF Aß42 from 150 to 4000 pg/mL. Validation of the method showed a recovery of 100% (15%), intraassay and interassay imprecision of 5.0% and 6.4%, respectively, and an expanded uncertainty of 15.7%. No analytical interferences or carryover were detected. CONCLUSIONS: This method will help set the value of CSF Aß42 in a CRM, which could be used to harmonize Aß42 assays and facilitate the introduction of general cutoff concentrations for CSF Aß42 in clinical trials and practice.
Assuntos
Peptídeos beta-Amiloides/líquido cefalorraquidiano , Fragmentos de Peptídeos/líquido cefalorraquidiano , Biomarcadores/líquido cefalorraquidiano , Calibragem , Isótopos de Carbono , Cromatografia Líquida/normas , Humanos , Isótopos de Nitrogênio , Padrões de Referência , Espectrometria de Massas em Tandem/normasRESUMO
Limited sample volume is often an obstacle in clinical research and one way to circumvent this is to use multiplex techniques where several different analytes are simultaneously measured. There is a multitude of different platforms that can be used for multiplexing and their uniqueness and similarities will be described. Multivariate analysis is a powerful tool for extracting information from multiplex data. An introduction to one such algorithm is presented followed by examples from the literature, in the field of neurodegeneration, where multiplex and multivariate methods have been used.
Assuntos
Análise Multivariada , Doenças Neurodegenerativas/líquido cefalorraquidiano , Algoritmos , Biomarcadores/líquido cefalorraquidiano , Ensaio de Imunoadsorção Enzimática , Humanos , Espectrometria de Massas , Metaboloma , Microesferas , Análise Serial de ProteínasRESUMO
BACKGROUND AND OBJECTIVE: PSEN1-H163Y carriers, at the presymptomatic stage, have reduced 18 FDG-PET binding in the cerebrum of the brain (Scholl et al., Neurobiol Aging 32:1388-1399, 2011). This could imply dysfunctional energy metabolism in the brain. In this study, plasma of presymptomatic PSEN1 mutation carriers was analyzed to understand associated metabolic changes. METHODS: We analyzed plasma from noncarriers (NC, n = 8) and presymptomatic PSEN1-H163Y mutation carriers (MC, n = 6) via untargeted metabolomics using gas and liquid chromatography coupled with mass spectrometry, which identified 1199 metabolites. All the metabolites were compared between MC and NC using univariate analysis, as well as correlated with the ratio of Aß1-42/A ß 1-40 , using Spearman's correlation. Altered metabolites were subjected to Ingenuity Pathway Analysis (IPA). RESULTS: Based on principal component analysis the plasma metabolite profiles were divided into dataset A and dataset B. In dataset A, when comparing between presymptomatic MC and NC, the levels of 79 different metabolites were altered. Out of 79, only 14 were annotated metabolites. In dataset B, 37 metabolites were significantly altered between presymptomatic MC and NC and nine metabolites were annotated. In both datasets, annotated metabolites represent amino acids, fatty acyls, bile acids, hexoses, purine nucleosides, carboxylic acids, and glycerophosphatidylcholine species. 1-docosapentaenoyl-GPC was positively correlated, uric acid and glucose were negatively correlated with the ratio of plasma Aß1-42 /Aß1-40 (P < 0.05). INTERPRETATION: This study finds dysregulated metabolite classes, which are changed before the disease symptom onset. Also, it provides an opportunity to compare with sporadic Alzheimer's Disease. Observed findings in this study need to be validated in a larger and independent Familial Alzheimer's Disease (FAD) cohort.
Assuntos
Doença de Alzheimer , Disfunção Cognitiva , Metaboloma , Plasma/metabolismo , Presenilina-1/genética , Sintomas Prodrômicos , Adulto , Doença de Alzheimer/sangue , Doença de Alzheimer/genética , Disfunção Cognitiva/sangue , Disfunção Cognitiva/genética , Humanos , Masculino , Pessoa de Meia-Idade , Mutação , Projetos Piloto , Análise de Componente Principal , Compostos RadiofarmacêuticosRESUMO
INTRODUCTION: Blood-based assays to measure brain amyloid beta (Aß) deposition are an attractive alternative to the cerebrospinal fluid (CSF)-based assays currently used in clinical settings. In this study, we examined different blood-based assays to measure Aß and how they compare among centers and assays. METHODS: Aliquots from 81 plasma samples were distributed to 10 participating centers. Seven immunological assays and four mass-spectrometric methods were used to measure plasma Aß concentrations. RESULTS: Correlations were weak for Aß42 while Aß40 correlations were stronger. The ratio Aß42/Aß40 did not improve the correlations and showed weak correlations. DISCUSSION: The poor correlations for Aß42 in plasma might have several potential explanations, such as the high levels of plasma proteins (compared to CSF), sensitivity to pre-analytical sample handling and specificity, and cross-reactivity of different antibodies. Different methods might also measure different pools of plasma Aß42. We, however, hypothesize that greater correlations might be seen in future studies because many of the methods have been refined during completion of this study.
RESUMO
Positron emission tomography (PET) neuroimaging with the Pittsburgh Compound_B (PiB) is widely used to assess amyloid plaque burden. Standard quantification approaches normalize PiB-PET by mean cerebellar gray matter uptake. Previous studies suggested similar pons and white-matter uptake in Alzheimer's disease (AD) and healthy controls (HC), but lack exhaustive comparison of normalization across the three regions, with data-driven diagnostic classification. We aimed to compare the impact of distinct reference regions in normalization, measured by data-driven statistical analysis, and correlation with cerebrospinal fluid (CSF) amyloid ß (Aß) species concentrations. 243 individuals with clinical diagnosis of AD, HC, mild cognitive impairment (MCI) and other dementias, from the Biomarkers for Alzheimer's/Parkinson's Disease (BIOMARKAPD) initiative were included. PiB-PET images and CSF concentrations of Aß38, Aß40 and Aß42 were submitted to classification using support vector machines. Voxel-wise group differences and correlations between normalized PiB-PET images and CSF Aß concentrations were calculated. Normalization by cerebellar gray matter and pons yielded identical classification accuracy of AD (accuracy-96%, sensitivity-96%, specificity-95%), and significantly higher than Aß concentrations (best accuracy 91%). Normalization by the white-matter showed decreased extent of statistically significant multivoxel patterns and was the only method not outperforming CSF biomarkers, suggesting statistical inferiority. Aß38 and Aß40 correlated negatively with PiB-PET images normalized by the white-matter, corroborating previous observations of correlations with non-AD-specific subcortical changes in white-matter. In general, when using the pons as reference region, higher voxel-wise group differences and stronger correlation with Aß42, the Aß42/Aß40 or Aß42/Aß38 ratios were found compared to normalization based on cerebellar gray matter.
Assuntos
Doença de Alzheimer/líquido cefalorraquidiano , Doença de Alzheimer/diagnóstico por imagem , Peptídeos beta-Amiloides/líquido cefalorraquidiano , Compostos de Anilina , Análise de Dados , Tomografia por Emissão de Pósitrons/métodos , Tiazóis , Idoso , Doença de Alzheimer/classificação , Biomarcadores/líquido cefalorraquidiano , Radioisótopos de Carbono , Feminino , Humanos , Masculino , Pessoa de Meia-IdadeRESUMO
Generation of amyloid-ß peptides (Aßs) by proteolytic cleavage of the amyloid-ß protein precursor (AßPP), especially increased production of Aß42/Aß43 over Aß40, and their aggregation as oligomers and plaques, represent a characteristic feature of Alzheimer's disease (AD). In familial AD (FAD), altered Aß production originates from specific mutations of AßPP or presenilins 1/2 (PS1/PS2), the catalytic subunits of γ-secretase. In sporadic AD, the origin of altered production of Aßs remains unknown. We hypothesize that the 'human chemical exposome' contains products able to favor the production of Aß42/Aß43 over Aß40 and shorter Aßs. To detect such products, we screened a library of 3500â+âcompounds in a cell-based assay for enhanced Aß42/Aß43 production. Nine pyrazole insecticides were found to induce a ß- and γ-secretase-dependent, 3-10-fold increase in the production of extracellular Aß42 in various cell lines and neurons differentiated from induced pluripotent stem cells derived from healthy and FAD patients. Immunoprecipitation/mass spectrometry analyses showed increased production of Aßs cleaved at positions 42/43, and reduced production of peptides cleaved at positions 38 and shorter. Strongly supporting a direct effect on γ-secretase activity, pyrazoles shifted the cleavage pattern of another γ-secretase substrate, alcadeinα, and shifted the cleavage of AßPP by highly purified γ-secretase toward Aß42/Aß43. Focusing on fipronil, we showed that some of its metabolites, in particular the persistent fipronil sulfone, also favor the production of Aß42/Aß43 in both cell-based and cell-free systems. Fipronil administered orally to mice and rats is known to be metabolized rapidly, mostly to fipronil sulfone, which stably accumulates in adipose tissue and brain. In conclusion, several widely used pyrazole insecticides enhance the production of toxic, aggregation prone Aß42/Aß43 peptides, suggesting the possible existence of environmental "Alzheimerogens" which may contribute to the initiation and propagation of the amyloidogenic process in sporadic AD.
Assuntos
Peptídeos beta-Amiloides/metabolismo , Inseticidas/efeitos adversos , Fragmentos de Peptídeos/metabolismo , Pirazóis/efeitos adversos , Tecido Adiposo/efeitos dos fármacos , Tecido Adiposo/metabolismo , Doença de Alzheimer/etiologia , Doença de Alzheimer/metabolismo , Secretases da Proteína Precursora do Amiloide/metabolismo , Animais , Encéfalo/efeitos dos fármacos , Encéfalo/metabolismo , Exposição Ambiental , Células HEK293 , Humanos , Células-Tronco Pluripotentes Induzidas/efeitos dos fármacos , Células-Tronco Pluripotentes Induzidas/metabolismo , Inseticidas/química , Inseticidas/farmacocinética , Camundongos , Neurônios/efeitos dos fármacos , Neurônios/metabolismo , Proteoma/efeitos dos fármacos , Pirazóis/química , Pirazóis/farmacocinética , RatosRESUMO
Alzheimer's disease (AD) is the most common neurodegenerative disease among the elderly and accounts for 60-80% of all cases of dementia. Currently, the diagnosis of AD is based on cognitive tests and mental state exams, but the peptide amyloid-beta (Aß) in cerebrospinal fluid (CSF) is increasingly used in clinical trials and settings. As for most protein and peptide biomarkers, quantification is performed using antibody-based techniques, such as enzyme-linked immunosorbent assay (ELISA). However, intra- and inter-laboratory variability in these assays hamper its use as a diagnostic marker in clinical routine. An antibody-independent Reference Measurement Procedure (RMP) was developed based on solid-phase extraction (SPE) and liquid chromatography (LC)-tandem mass spectrometry (MS/MS), where stable, isotope-labeled Aß peptides were used as internal standards, enabling absolute quantification. A high-resolution quadrupole-orbitrap hybrid instrument was used for the measurements. The method allows for the quantification of CSF Aß1-42 between 150-4,000 pg/mL.
Assuntos
Peptídeos beta-Amiloides/análise , Líquido Cefalorraquidiano/metabolismo , Espectrometria de Massas em Tandem/métodos , Doença de Alzheimer/diagnóstico , Doença de Alzheimer/metabolismo , Biomarcadores/metabolismo , Ensaio de Imunoadsorção Enzimática , Humanos , Extração em Fase SólidaRESUMO
Importance: Visual assessment of amyloid positron emission tomographic (PET) images has been approved by regulatory authorities for clinical use. Several immunoassays have been developed to measure ß-amyloid (Aß) 42 in cerebrospinal fluid (CSF). The agreement between CSF Aß42 measures from different immunoassays and visual PET readings may influence the use of CSF biomarkers and/or amyloid PET assessment in clinical practice and trials. Objective: To determine the concordance between CSF Aß42 levels measured using 5 different immunoassays and visual amyloid PET analysis. Design, Setting, and Participants: The study included 262 patients with mild cognitive impairment or subjective cognitive decline from the Swedish BioFINDER (Biomarkers for Identifying Neurodegenerative Disorders Early and Reliably) cohort (recruited from September 1, 2010, through December 31, 2014) who had undergone flutemetamol F 18 ([18F]flutemetamol)-labeled PET. Levels of CSF Aß42 were analyzed using the classic INNOTEST and the newer modified INNOTEST, fully automated Lumipulse (FL), EUROIMMUN (EI), and Meso Scale Discovery (MSD) assays. Concentrations of CSF Aß were assessed using an antibody-independent mass spectrometry-based reference measurement procedure. Main Outcomes and Measures: The concordance of CSF Aß42 levels and Aß42:Aß40 and Aß42:tau ratios with visual [18F]flutemetamol PET status. Results: Of 262 participants (mean [SD] age, 70.9 [5.5] years), 108 were women (41.2%) and 154 were men (58.8%). The mass spectrometry-derived Aß42 values showed higher correlations with the modified Aß42-INNOTEST (r = 0.97), Aß42-FL (r = 0.93), Aß42-EI (r = 0.93), and Aß42-MSD (r = 0.95) assays compared with the classic Aß42-INNOTEST assay (r = 0.88; P ≤ .01). The signal in the classic Aß42-INNOTEST assay was partly quenched by recombinant Aß1-40 peptide. However, the classic Aß42-INNOTEST assay showed better concordance with visual [18F]flutemetamol PET status (area under the receiver operating characteristic curve [AUC], 0.92) compared with the newer assays (AUCs, 0.87-0.89; P ≤ .01). The accuracies of the newer assays improved significantly when Aß42:Aß40 (AUCs, 0.93-0.95; P ≤ .01), Aß42 to total tau (T-tau) (AUCs, 0.94; P ≤ .05), or Aß42 to phosphorylated tau (P-tau) (AUCs, 0.94-0.95; P ≤ .001) ratios were used. A combination of the Aß42:Aß40 ratio and T-tau or P-tau level did not improve the accuracy compared with the ratio alone. Conclusions and Relevance: Concentrations of CSF Aß42 derived from the new immunoassays (modified INNOTEST, FL, EI, and MSD) may correlate better with the antibody-independent mass spectrometry-based reference measurement procedure and may show improved agreement with visual [18F]flutemetamol PET assessment when using the Aß42:Aß40 or Aß42:tau ratios. These findings suggest the benefit of implementing the CSF Aß42:Aß40 or Aß42:tau ratios as a biomarker of amyloid deposition in clinical practice and trials.
Assuntos
Peptídeos beta-Amiloides/líquido cefalorraquidiano , Amiloide/metabolismo , Córtex Cerebral/diagnóstico por imagem , Disfunção Cognitiva/líquido cefalorraquidiano , Fragmentos de Peptídeos/líquido cefalorraquidiano , Proteínas tau/líquido cefalorraquidiano , Idoso , Compostos de Anilina , Área Sob a Curva , Benzotiazóis , Córtex Cerebral/metabolismo , Disfunção Cognitiva/diagnóstico por imagem , Disfunção Cognitiva/metabolismo , Estudos de Coortes , Feminino , Humanos , Imunoensaio , Masculino , Tomografia por Emissão de Pósitrons , Curva ROC , Compostos Radiofarmacêuticos , SuéciaRESUMO
BACKGROUND: Proteolytic degradation of amyloid ß (Aß) peptides has been intensely studied due to the central role of Aß in Alzheimer's disease (AD) pathogenesis. While several enzymes have been shown to degrade Aß peptides, the main pathway of Aß degradation in vivo is unknown. Cerebrospinal fluid (CSF) Aß42 is reduced in AD, reflecting aggregation and deposition in the brain, but low CSF Aß42 is, for unknown reasons, also found in some inflammatory brain disorders such as bacterial meningitis. METHOD: Using 18O-labeling mass spectrometry and immune-affinity purification, we examined endogenous proteolytic processing of Aß in human CSF. RESULTS: The Aß peptide profile was stable in CSF samples from healthy controls but in CSF samples from patients with bacterial meningitis, showing increased leukocyte cell count, 18O-labeling mass spectrometry identified proteolytic activities degrading Aß into several short fragments, including abundant Aß1-19 and 1-20. After antibiotic treatment, no degradation of Aß was detected. In vitro experiments located the source of the proteolytic activity to blood components, including leukocytes and erythrocytes, with insulin-degrading enzyme as the likely protease. A recombinant version of the mid-domain anti-Aß antibody solanezumab was found to inhibit insulin-degrading enzyme-mediated Aß degradation. CONCLUSION: 18O labeling-mass spectrometry can be used to detect endogenous proteolytic activity in human CSF. Using this technique, we found an enzymatic activity that was identified as insulin-degrading enzyme that cleaves Aß in the mid-domain of the peptide, and could be inhibited by a recombinant version of the mid-domain anti-Aß antibody solanezumab.