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Importance: An accurate blood test for Alzheimer disease (AD) could streamline the diagnostic workup and treatment of AD. Objective: To prospectively evaluate a clinically available AD blood test in primary care and secondary care using predefined biomarker cutoff values. Design, Setting, and Participants: There were 1213 patients undergoing clinical evaluation due to cognitive symptoms who were examined between February 2020 and January 2024 in Sweden. The biomarker cutoff values had been established in an independent cohort and were applied to a primary care cohort (n = 307) and a secondary care cohort (n = 300); 1 plasma sample per patient was analyzed as part of a single batch for each cohort. The blood test was then evaluated prospectively in the primary care cohort (n = 208) and in the secondary care cohort (n = 398); 1 plasma sample per patient was sent for analysis within 2 weeks of collection. Exposure: Blood tests based on plasma analyses by mass spectrometry to determine the ratio of plasma phosphorylated tau 217 (p-tau217) to non-p-tau217 (expressed as percentage of p-tau217) alone and when combined with the amyloid-ß 42 and amyloid-ß 40 (Aß42:Aß40) plasma ratio (the amyloid probability score 2 [APS2]). Main Outcomes and Measures: The primary outcome was AD pathology (determined by abnormal cerebrospinal fluid Aß42:Aß40 ratio and p-tau217). The secondary outcome was clinical AD. The positive predictive value (PPV), negative predictive value (NPV), diagnostic accuracy, and area under the curve (AUC) values were calculated. Results: The mean age was 74.2 years (SD, 8.3 years), 48% were women, 23% had subjective cognitive decline, 44% had mild cognitive impairment, and 33% had dementia. In both the primary care and secondary care assessments, 50% of patients had AD pathology. When the plasma samples were analyzed in a single batch in the primary care cohort, the AUC was 0.97 (95% CI, 0.95-0.99) when the APS2 was used, the PPV was 91% (95% CI, 87%-96%), and the NPV was 92% (95% CI, 87%-96%); in the secondary care cohort, the AUC was 0.96 (95% CI, 0.94-0.98) when the APS2 was used, the PPV was 88% (95% CI, 83%-93%), and the NPV was 87% (95% CI, 82%-93%). When the plasma samples were analyzed prospectively (biweekly) in the primary care cohort, the AUC was 0.96 (95% CI, 0.94-0.98) when the APS2 was used, the PPV was 88% (95% CI, 81%-94%), and the NPV was 90% (95% CI, 84%-96%); in the secondary care cohort, the AUC was 0.97 (95% CI, 0.95-0.98) when the APS2 was used, the PPV was 91% (95% CI, 87%-95%), and the NPV was 91% (95% CI, 87%-95%). The diagnostic accuracy was high in the 4 cohorts (range, 88%-92%). Primary care physicians had a diagnostic accuracy of 61% (95% CI, 53%-69%) for identifying clinical AD after clinical examination, cognitive testing, and a computed tomographic scan vs 91% (95% CI, 86%-96%) using the APS2. Dementia specialists had a diagnostic accuracy of 73% (95% CI, 68%-79%) vs 91% (95% CI, 88%-95%) using the APS2. In the overall population, the diagnostic accuracy using the APS2 (90% [95% CI, 88%-92%]) was not different from the diagnostic accuracy using the percentage of p-tau217 alone (90% [95% CI, 88%-91%]). Conclusions and Relevance: The APS2 and percentage of p-tau217 alone had high diagnostic accuracy for identifying AD among individuals with cognitive symptoms in primary and secondary care using predefined cutoff values. Future studies should evaluate how the use of blood tests for these biomarkers influences clinical care.
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Enfermedad de Alzheimer , Péptidos beta-Amiloides , Biomarcadores , Fragmentos de Péptidos , Atención Primaria de Salud , Atención Secundaria de Salud , Proteínas tau , Anciano , Anciano de 80 o más Años , Femenino , Humanos , Masculino , Persona de Mediana Edad , Enfermedad de Alzheimer/diagnóstico , Enfermedad de Alzheimer/sangre , Péptidos beta-Amiloides/sangre , Biomarcadores/sangre , Disfunción Cognitiva/diagnóstico , Disfunción Cognitiva/sangre , Fragmentos de Péptidos/sangre , Fosforilación , Estudios Prospectivos , Sensibilidad y Especificidad , Suecia , Proteínas tau/sangreRESUMEN
INTRODUCTION: Incorporating blood-based Alzheimer's disease biomarkers such as tau and amyloid beta (Aß) into screening algorithms may improve screening efficiency. METHODS: Plasma Aß, phosphorylated tau (p-tau)181, and p-tau217 concentration levels from AHEAD 3-45 study participants were measured using mass spectrometry. Tau concentration ratios for each proteoform were calculated to normalize for inter-individual differences. Receiver operating characteristic (ROC) curve analysis was performed for each biomarker against amyloid positivity, defined by > 20 Centiloids. Mixture of experts analysis assessed the value of including tau concentration ratios into the existing predictive algorithm for amyloid positron emission tomography status. RESULTS: The area under the receiver operating curve (AUC) was 0.87 for Aß42/Aß40, 0.74 for phosphorylated variant p-tau181 ratio (p-tau181/np-tau181), and 0.92 for phosphorylated variant p-tau217 ratio (p-tau217/np-tau217). The Plasma Predicted Centiloid (PPC), a predictive model including p-tau217/np-tau217, Aß42/Aß40, age, and apolipoprotein E improved AUC to 0.95. DISCUSSION: Including plasma p-tau217/np-tau217 along with Aß42/Aß40 in predictive algorithms may streamline screening preclinical individuals into anti-amyloid clinical trials. CLINICALTRIALS: gov Identifier: NCT04468659 HIGHLIGHTS: The addition of plasma phosphorylated variant p-tau217 ratio (p-tau217/np-tau217) significantly improved plasma biomarker algorithms for identifying preclinical amyloid positron emission tomography positivity. Prediction performance at higher NAV Centiloid levels was improved with p-tau217/np-tau217. All models generated for this study are incorporated into the Plasma Predicted Centiloid (PPC) app for public use.
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Enfermedad de Alzheimer , Humanos , Enfermedad de Alzheimer/diagnóstico , Péptidos beta-Amiloides , Fragmentos de Péptidos , Amiloide , Proteínas tau , Tomografía de Emisión de Positrones , BiomarcadoresRESUMEN
INTRODUCTION: In trials of amyloid-lowering drugs for Alzheimer's disease (AD), differential eligibility may contribute to under-inclusion of racial and ethnic underrepresented groups. We examined plasma amyloid beta 42/40 and positron emission tomography (PET) amyloid eligibility for the ongoing AHEAD Study preclinical AD program (NCT04468659). METHODS: Univariate logistic regression models were used to examine group differences in plasma and PET amyloid screening eligibility. RESULTS: Of 4905 participants screened at time of analysis, 1724 were plasma eligible to continue in screening: 13.3% Hispanic Black, 24.7% Hispanic White, 20.8% non-Hispanic (NH) Asian, 24.7% NH Black, and 38.9% NH White. Plasma eligibility differed across groups in models controlling for covariates (odds ratio from 1.9 to 4.0 compared to the NH White reference group, P < 0.001). Among plasma eligible participants, PET eligibility did not differ by group. DISCUSSION: These results suggest that prevalence of brain amyloid pathology differed, but that eligibility based on plasma was equally effective across racial and ethnic group members. HIGHLIGHTS: Plasma amyloid eligibility is lower in underrepresented racial and ethnic groups. In plasma eligible adults, positron emission tomography eligibility rates are similar across race and ethnicity. Plasma biomarker tests may be similarly effective across racial and ethnic groups.
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Enfermedad de Alzheimer , Péptidos beta-Amiloides , Biomarcadores , Tomografía de Emisión de Positrones , Anciano , Femenino , Humanos , Masculino , Enfermedad de Alzheimer/sangre , Enfermedad de Alzheimer/etnología , Enfermedad de Alzheimer/diagnóstico por imagen , Péptidos beta-Amiloides/sangre , Biomarcadores/sangre , Encéfalo/diagnóstico por imagen , Encéfalo/patología , Etnicidad , Grupos RacialesRESUMEN
BACKGROUND: With the availability of disease-modifying therapies for Alzheimer's disease (AD), it is important for clinicians to have tests to aid in AD diagnosis, especially when the presence of amyloid pathology is a criterion for receiving treatment. METHODS: High-throughput, mass spectrometry-based assays were used to measure %p-tau217 and amyloid beta (Aß)42/40 ratio in blood samples from 583 individuals with suspected AD (53% positron emission tomography [PET] positive by Centiloid > 25). An algorithm (PrecivityAD2 test) was developed using these plasma biomarkers to identify brain amyloidosis by PET. RESULTS: The area under the receiver operating characteristic curve (AUC-ROC) for %p-tau217 (0.94) was statistically significantly higher than that for p-tau217 concentration (0.91). The AUC-ROC for the PrecivityAD2 test output, the Amyloid Probability Score 2, was 0.94, yielding 88% agreement with amyloid PET. Diagnostic performance of the APS2 was similar by ethnicity, sex, age, and apoE4 status. DISCUSSION: The PrecivityAD2 blood test showed strong clinical validity, with excellent agreement with brain amyloidosis by PET.
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Algoritmos , Enfermedad de Alzheimer , Péptidos beta-Amiloides , Biomarcadores , Encéfalo , Espectrometría de Masas , Fragmentos de Péptidos , Tomografía de Emisión de Positrones , Proteínas tau , Humanos , Péptidos beta-Amiloides/sangre , Femenino , Masculino , Proteínas tau/sangre , Enfermedad de Alzheimer/sangre , Enfermedad de Alzheimer/diagnóstico , Enfermedad de Alzheimer/diagnóstico por imagen , Anciano , Fragmentos de Péptidos/sangre , Encéfalo/diagnóstico por imagen , Encéfalo/metabolismo , Biomarcadores/sangre , Persona de Mediana Edad , Anciano de 80 o más Años , Curva ROCRESUMEN
INTRODUCTION: As Alzheimer's disease (AD) biomarkers rapidly develop, tools are needed that accurately and effectively communicate risk of AD dementia. METHODS: We analyzed longitudinal data from >10,000 cognitively unimpaired older adults. Five-year risk of AD dementia was modeled using survival analysis. RESULTS: A demographic model was developed and validated on independent data with area under the receiver operating characteristic curve (AUC) for 5-year prediction of AD dementia of 0.79. Clinical and cognitive variables (AUC = 0.79), and apolipoprotein E genotype (AUC = 0.76) were added to the demographic model. We then incorporated the risk computed from the demographic model with hazard ratios computed from independent data for amyloid positron emission tomography status and magnetic resonance imaging hippocampal volume (AUC = 0.84), and for plasma amyloid beta (Aß)42/Aß40 (AUC = 0.82). DISCUSSION: An adaptive tool was developed and validated to compute absolute risks of AD dementia. This approach allows for improved accuracy and communication of AD risk among cognitively unimpaired older adults.
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Enfermedad de Alzheimer , Disfunción Cognitiva , Humanos , Anciano , Enfermedad de Alzheimer/patología , Péptidos beta-Amiloides , Biomarcadores , Tomografía de Emisión de Positrones , Proteínas tauRESUMEN
INTRODUCTION: Pre-analytical sample handling might affect the results of Alzheimer's disease blood-based biomarkers. We empirically tested variations of common blood collection and handling procedures. METHODS: We created sample sets that address the effect of blood collection tube type, and of ethylene diamine tetraacetic acid plasma delayed centrifugation, centrifugation temperature, aliquot volume, delayed storage, and freeze-thawing. We measured amyloid beta (Aß)42 and 40 peptides with six assays, and Aß oligomerization-tendency (OAß), amyloid precursor protein (APP)699-711 , glial fibrillary acidic protein (GFAP), neurofilament light (NfL), total tau (t-tau), and phosphorylated tau181. RESULTS: Collection tube type resulted in different values of all assessed markers. Delayed plasma centrifugation and storage affected Aß and t-tau; t-tau was additionally affected by centrifugation temperature. The other markers were resistant to handling variations. DISCUSSION: We constructed a standardized operating procedure for plasma handling, to facilitate introduction of blood-based biomarkers into the research and clinical settings.
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Enfermedad de Alzheimer , Antígenos de Grupos Sanguíneos , Péptidos beta-Amiloides , Biomarcadores , Humanos , Estándares de Referencia , Manejo de Especímenes , Proteínas tauRESUMEN
Sacubitril/valsartan (LCZ696) is the first angiotensin receptor neprilysin inhibitor approved to reduce cardiovascular mortality and hospitalization in patients with heart failure with reduced ejection fraction. As neprilysin (NEP) is one of several enzymes known to degrade amyloid-ß (Aß), there is a theoretical risk of Aß accumulation following long-term NEP inhibition. The primary objective of this study was to evaluate the potential effects of sacubitril/valsartan on central nervous system clearance of Aß isoforms in cynomolgus monkeys using the sensitive Stable Isotope Labeling Kinetics (SILK™)-Aß methodology. The in vitro selectivity of valsartan, sacubitril, and its active metabolite sacubitrilat was established; sacubitrilat did not inhibit other human Aß-degrading metalloproteases. In a 2-week study, sacubitril/valsartan (50mg/kg/day) or vehicle was orally administered to female cynomolgus monkeys in conjunction with SILK™-Aß. Despite low cerebrospinal fluid (CSF) and brain penetration, CSF exposure to sacubitril was sufficient to inhibit NEP and resulted in an increase in the elimination half-life of Aß1-42 (65.3%; p=0.026), Aß1-40 (35.2%; p=0.04) and Aßtotal (29.8%; p=0.04) acutely; this returned to normal as expected with repeated dosing for 15days. CSF concentrations of newly generated Aß (AUC(0-24h)) indicated elevations in the more aggregable form Aß1-42 on day 1 (20.4%; p=0.039) and day 15 (34.7%; p=0.0003) and in shorter forms Aß1-40 (23.4%; p=0.009), Aß1-38 (64.1%; p=0.0001) and Aßtotal (50.45%; p=0.00002) on day 15. However, there were no elevations in any Aß isoforms in the brains of these monkeys on day 16. In a second study cynomolgus monkeys were administered sacubitril/valsartan (300mg/kg) or vehicle control for 39weeks; no microscopic brain changes or Aß deposition, as assessed by immunohistochemical staining, were present. Further clinical studies are planned to address the relevance of these findings.
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Aminobutiratos/toxicidad , Péptidos beta-Amiloides/metabolismo , Antagonistas de Receptores de Angiotensina/toxicidad , Encéfalo/efectos de los fármacos , Neprilisina/antagonistas & inhibidores , Inhibidores de Proteasas/toxicidad , Tetrazoles/toxicidad , Administración Oral , Aminobutiratos/administración & dosificación , Aminobutiratos/farmacocinética , Antagonistas de Receptores de Angiotensina/administración & dosificación , Antagonistas de Receptores de Angiotensina/farmacocinética , Animales , Biotransformación , Compuestos de Bifenilo , Encéfalo/enzimología , Combinación de Medicamentos , Femenino , Humanos , Inmunohistoquímica , Marcaje Isotópico , Macaca fascicularis , Neprilisina/metabolismo , Inhibidores de Proteasas/administración & dosificación , Inhibidores de Proteasas/farmacocinética , Isoformas de Proteínas , Proteínas Recombinantes/metabolismo , Medición de Riesgo , Tetrazoles/administración & dosificación , Tetrazoles/farmacocinética , Regulación hacia Arriba , ValsartánRESUMEN
The apolipoprotein E (APOE)-ε4 allele is the strongest genetic risk factor for late-onset, sporadic Alzheimer's disease, likely increasing risk by altering amyloid-ß (Aß) accumulation. We recently demonstrated that the low-density lipoprotein receptor (LDLR) is a major apoE receptor in the brain that strongly regulates amyloid plaque deposition. In the current study, we sought to understand the mechanism by which LDLR regulates Aß accumulation by altering Aß clearance from brain interstitial fluid. We hypothesized that increasing LDLR levels enhances blood-brain barrier-mediated Aß clearance, thus leading to reduced Aß accumulation. Using the brain Aß efflux index method, we found that blood-brain barrier-mediated clearance of exogenously administered Aß is enhanced with LDLR overexpression. We next developed a method to directly assess the elimination of centrally derived, endogenous Aß into the plasma of mice using an anti-Aß antibody that prevents degradation of plasma Aß, allowing its rate of appearance from the brain to be measured. Using this plasma Aß accumulation technique, we found that LDLR overexpression enhances brain-to-blood Aß transport. Together, our results suggest a unique mechanism by which LDLR regulates brain-to-blood Aß clearance, which may serve as a useful therapeutic avenue in targeting Aß clearance from the brain.
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Amiloidosis/metabolismo , Apolipoproteína E4/genética , Receptores de LDL/biosíntesis , Alelos , Péptidos beta-Amiloides/metabolismo , Animales , Barrera Hematoencefálica , Encéfalo/metabolismo , Modelos Animales de Enfermedad , Insulina/metabolismo , Cinética , Ratones , Ratones Endogámicos C57BL , Ratones Endogámicos DBA , Ratones Transgénicos , Microdiálisis , TransgenesRESUMEN
Alzheimer's disease is the public health crisis of the 21st century. There is a clear need for a widely available, inexpensive and reliable method to diagnosis Alzheimer's disease in the earliest stages, track disease progression, and accelerate clinical development of new therapeutics. One avenue of research being explored is blood based biomarkers. In April 2012, the Alzheimer's Association and the Alzheimer's Drug Discovery Foundation convened top scientists from around the world to discuss the state of blood based biomarker development. This manuscript summarizes the meeting and the resultant discussion, including potential next steps to move this area of research forward.
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Enfermedad de Alzheimer/sangre , Biomarcadores/sangre , Progresión de la Enfermedad , Diagnóstico Precoz , Ensayo de Inmunoadsorción Enzimática , HumanosRESUMEN
Alzheimer's disease (AD) is a progressive irreversible neurodegenerative disorder that represents a major global public health concern. Traditionally, AD is diagnosed using cerebrospinal fluid biomarker analysis or brain imaging modalities. Recently, less burdensome, more widely available blood biomarker (BBM) assays for amyloid-beta (Aß42/40) and phosphorylated-tau concentrations have been found to accurately identify the presence/absence of brain amyloid plaques and tau tangles and have helped to streamline AD diagnosis. However, few BBMs have been rigorously analytically validated. Herein, we report the analytical validation of a novel liquid chromatography-tandem mass spectrometry (LC-MS/MS) multiplex method for quantifying plasma phosphorylated-tau217 (p-tau217) and non-phosphorylated-tau217 (np-tau217) peptide concentrations. We combined the p-tau217/np-tau217 concentrations ratio (%p-tau217) and the previously validated LC-MS/MS multiplex assay for plasma Aß42/40 into a new multianalyte assay with algorithmic analysis (MAAA; PrecivityAD2™ test) that identifies brain amyloid status based on brain amyloid positron emission tomography. We found (a) the %p-tau217 assay is precise, accurate, sensitive, and linear over a wide analytical measurement range, and free from carryover and interference; (b) the pre-analytical specimen collection, processing, storage, and shipping conditions that maintain plasma tau peptide stability; and (c) using the measured analytical imprecision for plasma Aß42/40 and p-tau217/np-tau217 levels in a worst-case scenario model, the PrecivityAD2 test algorithm for amyloid pathology classification changed for only 3.5% of participants from brain amyloid positive to negative, or from negative to positive. The plasma sample preparation and LC-MS/MS methods underlying the PrecivityAD2 test are suitable for use in the clinical laboratory and valid for the test's intended purpose: to aid in the diagnostic evaluation of individuals aged 55 and older with signs or symptoms of mild cognitive impairment or dementia.
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BACKGROUND: Amyloid beta protein (Aß) is a treatment target in Alzheimer's Disease (AD). Lowering production of its parent protein, APP, has benefits in preclinical models. Posiphen, an orally administered small molecule, binds to an iron-responsive element in APP mRNA and decreases translation of APP and Aß. To augment human data for Posiphen, we evaluated safety, tolerability and pharmacokinetic and pharmacodynamic (PD) effects on Aß metabolism using Stable Isotope Labeling Kinetic (SILK) analysis. METHODS: Double-blind phase 1b randomized ascending dose clinical trial, at five sites, under an IRB-approved protocol. Participants with mild cognitive impairment or mild AD (Early AD) confirmed by low CSF Aß42/40 were randomized (within each dose arm) to Posiphen or placebo. Pretreatment assessment included lumbar puncture for CSF. Participants took Posiphen or placebo for 21-23 days, then underwent CSF catheter placement, intravenous infusion of 13C6-leucine, and CSF sampling for 36 h. Safety and tolerability were assessed through participant reports, EKG and laboratory tests. CSF SILK analysis measured Aß40, 38 and 42 with immunoprecipitation-mass spectrometry. Baseline and day 21 CSF APP, Aß and other biomarkers were measured with immunoassays. The Mini-Mental State Exam and ADAS-cog12 were given at baseline and day 21. RESULTS: From June 2017 to December 2021, 19 participants were enrolled, randomized within dose cohorts (5 active: 3 placebo) of 60 mg once/day and 60 mg twice/day; 1 participant was enrolled and completed 60 mg three times/day. 10 active drug and 5 placebo participants completed all study procedures. Posiphen was safe and well-tolerated. 8 participants had headaches related to CSF catheterization; 5 needed blood patches. Prespecified SILK analyses of Fractional Synthesis Rate (FSR) for CSF Aß40 showed no significant overall or dose-dependent effects of Posiphen vs. placebo. Comprehensive multiparameter modeling of APP kinetics supported dose-dependent lowering of APP production by Posiphen. Cognitive measures and CSF biomarkers did not change significantly from baseline to 21 days in Posiphen vs. placebo groups. CONCLUSIONS: Posiphen was safe and well-tolerated in Early AD. A multicenter SILK study was feasible. Findings are limited by small sample size but provide additional supportive safety and PK data. Comprehensive modeling of biomarker dynamics using SILK data may reveal subtle drug effects. TRIAL REGISTRATION: NCT02925650 on clinicaltrials.gov (registered on 10-24-2016).
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Enfermedad de Alzheimer , Péptidos beta-Amiloides , Humanos , Enfermedad de Alzheimer/tratamiento farmacológico , Enfermedad de Alzheimer/líquido cefalorraquídeo , Método Doble Ciego , Masculino , Femenino , Anciano , Péptidos beta-Amiloides/líquido cefalorraquídeo , Disfunción Cognitiva/tratamiento farmacológico , Persona de Mediana Edad , Relación Dosis-Respuesta a Droga , Fragmentos de Péptidos/líquido cefalorraquídeo , Biomarcadores/líquido cefalorraquídeo , Anciano de 80 o más Años , Precursor de Proteína beta-Amiloide/genética , Resultado del TratamientoRESUMEN
Background: Amyloid beta protein (Aß) is a treatment target in Alzheimer's Disease (AD). Lowering production of its parent protein, APP, has benefits in preclinical models. Posiphen binds to an iron-responsive element in APP mRNA and decreases translation of APP and Aß. To augment human data for Posiphen, we evaluated safety, tolerability and pharmacokinetic and pharmacodynamic (PD) effects on Aß metabolism using Stable Isotope Labeling Kinetic (SILK) analysis. Methods: Double-blind phase 1b randomized ascending dose clinical trial, at five sites, under an IRB-approved protocol. Participants with mild cognitive impairment or mild AD (Early AD) with positive CSF biomarkers were randomized (within each dose arm) to Posiphen or placebo. Pretreatment assessment included lumbar puncture for CSF. Participants took Posiphen or placebo for 21-23 days, then underwent CSF catheter placement, intravenous infusion of 13C6-leucine, and CSF sampling for 36 hours. Safety and tolerability were assessed through participant reports, EKG and laboratory tests. CSF SILK analysis measured Aß40, 38 and 42 with immunoprecipitation-mass spectrometry. Baseline and day 21 CSF APP, Aß and other biomarkers were measured with immunoassays. The Mini-Mental State Exam and ADAS-cog12 were given at baseline and day 21. Results: From June 2017 to December 2021, 19 participants were enrolled, in dose cohorts (6 active: 2 placebo) of 60 mg once/day and 60 mg twice/day; 1 participant was enrolled and completed 60 mg three times/day. 10 active drug and 5 placebo participants completed all study procedures. Posiphen was safe and well-tolerated. 8 participants had headaches related to CSF catheterization; 5 needed blood patches. Prespecified SILK analyses of Fractional Synthesis Rate (FSR) for CSF Aß40 showed no significant overall or dose-dependent effects of Posiphen vs. placebo. Comprehensive multiparameter modeling of APP kinetics supported dose-dependent lowering of APP production by Posiphen. Cognitive measures and CSF biomarkers did not change significantly from baseline to 21 days in Posiphen vs placebo groups. Conclusions: Posiphen was safe and well-tolerated in Early AD. A multicenter SILK study was feasible. Findings are limited by small sample size but provide additional supportive safety and PK data. Comprehensive modeling of biomarker dynamics using SILK data may reveal subtle drug effects. Trial registration: NCT02925650 on clinicaltrials.gov.
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STUDY OBJECTIVES: Given the established racial disparities in both sleep health and dementia risk for African American populations, we assess cross-sectional and longitudinal associations of self-report sleep duration (SRSD) and daytime sleepiness with plasma amyloid beta (Aß) and cognition in an African American (AA) cohort. METHODS: In a cognitively unimpaired sample drawn from the African Americans Fighting Alzheimer's in Midlife (AA-FAiM) study, data on SRSD, Epworth Sleepiness Scale, demographics, and cognitive performance were analyzed. Aß40, Aß42, and the Aß42/40 ratio were quantified from plasma samples. Cross-sectional analyses explored associations between baseline predictors and outcome measures. Linear mixed-effect regression models estimated associations of SRSD and daytime sleepiness with plasma Aß and cognitive performance levels and change over time. RESULTS: One hundred and forty-seven participants comprised the cross-sectional sample. Baseline age was 63.2â ±â 8.51 years. 69.6% self-identified as female. SRSD was 6.4â ±â 1.1 hours and 22.4% reported excessive daytime sleepiness. The longitudinal dataset included 57 participants. In fully adjusted models, neither SRSD nor daytime sleepiness is associated with cross-sectional or longitudinal Aß. Associations with level and trajectory of cognitive test performance varied by measure of sleep health. CONCLUSIONS: SRSD was below National Sleep Foundation recommendations and daytime sleepiness was prevalent in this cohort. In the absence of observed associations with plasma Aß, poorer self-reported sleep health broadly predicted poorer cognitive function but not accelerated decline. Future research is necessary to understand and address modifiable sleep mechanisms as they relate to cognitive aging in AA at disproportionate risk for dementia. CLINICAL TRIAL INFORMATION: Not applicable.
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Demencia , Trastornos de Somnolencia Excesiva , Trastornos del Inicio y del Mantenimiento del Sueño , Anciano , Femenino , Humanos , Persona de Mediana Edad , Péptidos beta-Amiloides , Negro o Afroamericano , Cognición , Estudios Transversales , Trastornos de Somnolencia Excesiva/complicaciones , Duración del Sueño , MasculinoRESUMEN
The bcl-x gene appears to play a critical role in regulating apoptosis in the developing and mature CNS and following CNS injury. Two isoforms of Bcl-x are produced as a result of alternative pre-mRNA splicing: Bcl-x(L) (the long form) is anti-apoptotic, while Bcl-x(S) (short form) is pro-apoptotic. Despite the antagonistic activities of these two isoforms, little is known about how regulation of alternative splicing of bcl-x may mediate neural cell apoptosis. Here, we report that apoptotic stimuli (staurosporine or C2-ceramide) reciprocally altered Bcl-x splicing in neural cells, decreasing Bcl-x(L) while increasing Bcl-x(S). Specific knockdown of Bcl-x(S) attenuated apoptosis. To further define regulatory elements that influenced Bcl-x splicing, a Bcl-x minigene was constructed. Deletional analysis revealed several consensus sequences within intron 2 that altered splicing. We found that the splicing factor, CUG-binding-protein-1 (CUGBP1), bound to a consensus sequence close to the Bcl-x(L) 5' splice site, altering the Bcl-x(L)/Bcl-x(S) ratio and influencing cell death. In vivo, neonatal hypoxia-ischemia reciprocally altered Bcl-x pre-mRNA splicing, similar to the in vitro studies. Manipulation of the splice isoforms using viral gene transfer of Bcl-x(S) shRNA into the hippocampus of rats before neonatal hypoxia-ischemia decreased vulnerability to injury. Moreover, alterations in nuclear CUGBP1 preceded Bcl-x splicing changes. These results suggest that alternative pre-mRNA splicing may be an important regulatory mechanism for cell death after acute neurological injury and may potentially provide novel targets for intervention.
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Empalme Alternativo/genética , Lesiones Encefálicas/etiología , Hipoxia-Isquemia Encefálica/complicaciones , Precursores del ARN/metabolismo , Proteína bcl-X/metabolismo , Análisis de Varianza , Animales , Animales Recién Nacidos , Apoptosis/efectos de los fármacos , Apoptosis/genética , Proteínas CELF1 , Células Cultivadas , Corteza Cerebral/citología , Relación Dosis-Respuesta a Droga , Embrión de Mamíferos , Inhibidores Enzimáticos/farmacología , Femenino , Lateralidad Funcional , Regulación de la Expresión Génica/efectos de los fármacos , Regulación de la Expresión Génica/genética , Proteínas Fluorescentes Verdes/genética , Humanos , Etiquetado Corte-Fin in Situ , L-Lactato Deshidrogenasa/metabolismo , Masculino , Ratones , Neuronas/efectos de los fármacos , Neuronas/metabolismo , Embarazo , Precursores del ARN/genética , ARN Interferente Pequeño/metabolismo , Proteínas de Unión al ARN/metabolismo , Ratas , Esfingosina/análogos & derivados , Esfingosina/farmacología , Estaurosporina/farmacología , Factores de Tiempo , Transfección/métodos , Proteína bcl-X/genéticaRESUMEN
The contractile performance of the heart is linked to the energy that is available to it. Yet, the heart needs to respond quickly to changing demands. During diastole, the heart fills with blood and the heart chambers expand. Upon activation, contraction of cardiac muscle expels blood into the circulation. Early in systole, parts of the left ventricle are being stretched by incoming blood, before contraction causes shrinking of the ventricle. We explore here the effect of stretch of contracting permeabilized cardiac trabeculae of the rat on the rate of inorganic phosphate (P(i)) release resulting from ATP hydrolysis, using a fluorescent sensor for P(i) with millisecond time resolution. Stretch immediately reduces the rate of P(i) release, an effect observed both at full calcium activation (32 µmol/liter of Ca(2+)), and at a physiological activation level of 1 µmol/liter of Ca(2+). The results suggest that stretch redistributes the actomyosin cross-bridges toward their P(i)-containing state. The redistribution means that a greater fraction of cross-bridges will be poised to rapidly produce a force-generating transition and movement, compared with cross-bridges that have not been subjected to stretch. At the same time stretch modifies the P(i) balance in the cytoplasm, which may act as a cytoplasmic signal for energy turnover.
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Calcio/fisiología , Contracción Miocárdica , Miocardio/metabolismo , Fosfatos/metabolismo , Adenosina Trifosfato/metabolismo , Animales , Fenómenos Biomecánicos , Calcio/farmacología , Femenino , Técnicas In Vitro , Contracción Isométrica , Cinética , Miocardio/enzimología , Miosinas/metabolismo , Ratas , Ratas Sprague-Dawley , Sarcómeros/metabolismo , Sarcómeros/fisiología , Estrés FisiológicoRESUMEN
BACKGROUND: Participant eligibility for the A4 Study was determined by amyloid PET imaging. Given the disadvantages of amyloid PET imaging in accessibility and cost, blood-based biomarkers may serve as a sufficient biomarker and more cost-effective screening tool for patient enrollment into preclinical AD trials. OBJECTIVE: To determine if a blood-based screening test can adequately identify amyloid burden in participants screened into a preclinical AD trial. METHODS: In this cross-sectional study, 224 participants from the A4 Study received an amyloid PET scan (18Florbetapir) within 90 days of blood sample collection. Blood samples from all study participants were processed within 2âh after phlebotomy. Plasma amyloid measures were quantified by Shimazdu and C2âN Diagnostics using mass spectrometry-based platforms. A corresponding subset of blood samples (nâ=â100) was processed within 24âh after phlebotomy and analyzed by C2âN. RESULTS: Plasma Aß42/Aß40 demonstrated the highest association for Aß accumulation in the brain with an AUC 0.76 (95%CIâ=â0.69, 0.82) at C2âN and 0.80 (95%CIâ=â0.75, 0.86) at Shimadzu. Blood samples processed to plasma within 2âh after phlebotomy provided a better prediction of amyloid PET status than blood samples processed within 24âh (AUC 0.80 versus 0.64; pâ<â0.001). Age, sex, and APOE É4 carrier status did not the diagnostic performance of plasma Aß42/Aß40 to predict amyloid PET positivity in A4 Study participants. CONCLUSION: Plasma Aß42/Aß40 may serve as a potential biomarker for predicting elevated amyloid in the brain. Utilizing blood testing over PET imaging may improve screening efficiency into clinical trials.
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Enfermedad de Alzheimer , Humanos , Enfermedad de Alzheimer/diagnóstico , Péptidos beta-Amiloides , Estudios Transversales , Amiloide , Proteínas Amiloidogénicas , Biomarcadores , Tomografía de Emisión de Positrones , Fragmentos de PéptidosRESUMEN
BACKGROUND: The amyloid probability score (APS) is the model read-out of the analytically validated mass spectrometry-based PrecivityAD® blood test that incorporates the plasma Aß42/40 ratio, ApoE proteotype, and age to identify the likelihood of brain amyloid plaques among cognitively impaired individuals being evaluated for Alzheimer's disease. PURPOSE: This study aimed to provide additional independent evidence that the pre-established APS algorithm, along with its cutoff values, discriminates between amyloid positive and negative individuals. METHODS: The diagnostic performance of the PrecivityAD test was analyzed in a cohort of 200 nonrandomly selected Australian Imaging, Biomarker & Lifestyle Flagship Study of Aging (AIBL) study participants, who were either cognitively impaired or healthy controls, and for whom a blood sample and amyloid PET imaging were available. RESULTS: In a subset of the dataset aligned with the Intended Use population (patients aged 60 and older with CDR ≥0.5), the pre-established APS algorithm predicted amyloid PET with a sensitivity of 84.9% (CI: 72.9-92.1%) and specificity of 96% (CI: 80.5-99.3%), exclusive of 13 individuals for whom the test was inconclusive. INTERPRETATION: The study shows individuals with a high APS are more likely than those with a low APS to have abnormal amounts of amyloid plaques and be on an amyloid accumulation trajectory, a dynamic and evolving process characteristic of progressive AD pathology. Exploratory data suggest APS retains its diagnostic performance in healthy individuals, supporting further screening studies in the cognitively unimpaired.
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Enfermedad de Alzheimer , Péptidos beta-Amiloides , Humanos , Persona de Mediana Edad , Anciano , Placa Amiloide/diagnóstico por imagen , Australia , Enfermedad de Alzheimer/diagnóstico por imagen , Enfermedad de Alzheimer/patología , Envejecimiento/patología , AmiloideRESUMEN
Introduction: Continuous measures of amyloid burden as measured by positron emission tomography (PET) are being used increasingly to stage Alzheimer's disease (AD). This study examined whether cerebrospinal fluid (CSF) and plasma amyloid beta (Aß)42/Aß40 could predict continuous values for amyloid PET. Methods: CSF Aß42 and Aß40 were measured with automated immunoassays. Plasma Aß42 and Aß40 were measured with an immunoprecipitation-mass spectrometry assay. Amyloid PET was performed with Pittsburgh compound B (PiB). The continuous relationships of CSF and plasma Aß42/Aß40 with amyloid PET burden were modeled. Results: Most participants were cognitively normal (427 of 491 [87%]) and the mean age was 69.0 ± 8.8 years. CSF Aß42/Aß40 predicted amyloid PET burden until a relatively high level of amyloid accumulation (69.8 Centiloids), whereas plasma Aß42/Aß40 predicted amyloid PET burden until a lower level (33.4 Centiloids). Discussion: CSF Aß42/Aß40 predicts the continuous level of amyloid plaque burden over a wider range than plasma Aß42/Aß40 and may be useful in AD staging. Highlights: Cerebrospinal fluid (CSF) amyloid beta (Aß)42/Aß40 predicts continuous amyloid positron emission tomography (PET) values up to a relatively high burden.Plasma Aß42/Aß40 is a comparatively dichotomous measure of brain amyloidosis.Models can predict regional amyloid PET burden based on CSF Aß42/Aß40.CSF Aß42/Aß40 may be useful in staging AD.
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OBJECTIVE: The objective of this study was to examine clinicians' patient selection and result interpretation of a clinically validated mass spectrometry test measuring amyloid beta and ApoE blood biomarkers combined with patient age (PrecivityAD® blood test) in symptomatic patients evaluated for Alzheimer's disease (AD) or other causes of cognitive decline. METHODS: The Quality Improvement and Clinical Utility PrecivityAD Clinician Survey (QUIP I, ClinicalTrials.gov Identifier: NCT05477056) was a prospective, single-arm cohort study among 366 patients evaluated by neurologists and other cognitive specialists. Participants underwent blood biomarker testing and received an amyloid probability score (APS), indicating the likelihood of a positive result on an amyloid positron emission tomography (PET) scan. The primary study outcomes were appropriateness of patient selection as well as result interpretation associated with PrecivityAD blood testing. RESULTS: A 95% (347/366) concordance rate was noted between clinicians' patient selection and the test's intended use criteria. In the final analysis including these 347 patients (median age 75 years, 56% women), prespecified test result categories incorporated 133 (38%) low APS, 162 (47%) high APS, and 52 (15%) intermediate APS patients. Clinicians' pretest and posttest AD diagnosis probability changed from 58% to 23% in low APS patients and 71% to 89% in high APS patients (p < 0.0001). Anti-AD drug therapy decreased by 46% in low APS patients (p < 0.0001) and increased by 57% in high APS patients (p < 0.0001). INTERPRETATION: These findings demonstrate the clinical utility of the PrecivityAD blood test in clinical care and may have added relevance as new AD therapies are introduced.
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Enfermedad de Alzheimer , Disfunción Cognitiva , Humanos , Femenino , Anciano , Masculino , Péptidos beta-Amiloides/metabolismo , Estudios de Cohortes , Estudios Prospectivos , Enfermedad de Alzheimer/diagnóstico por imagen , Enfermedad de Alzheimer/complicaciones , Disfunción Cognitiva/diagnóstico , Encéfalo/diagnóstico por imagen , Encéfalo/metabolismo , Amiloide , Biomarcadores , Pruebas HematológicasRESUMEN
Introduction: It is critical to develop more inclusive Alzheimer's disease (AD) research protocols to ensure that historically excluded groups are included in preclinical research and have access to timely diagnosis and treatment. If validated in racialized groups, plasma AD biomarkers and measures of subtle cognitive dysfunction could provide avenues to expand diversity in preclinical AD research. We sought to evaluate the utility of two easily obtained, low-burden disease markers, plasma amyloid beta (Aß)42/40, and intra-individual cognitive variability (IICV), to predict concurrent and longitudinal cognitive performance in a sample of Black adults. Methods: Two hundred fifty-seven Black participants enrolled in the African Americans Fighting Alzheimer's in Midlife (AA-FAIM) study underwent at least one cognitive assessment visit; a subset of n = 235 had plasma samples. Baseline IICV was calculated as the standard deviation across participants' z scores on five cognitive measures: Rey Auditory Verbal Learning Test Delayed Recall, Trail Making Test Parts A and B (Trails A and B), and Boston Naming Test. Using mixed effects regression models, we compared concurrent and longitudinal models to baseline plasma Aß42/40 or IICV by age interactions. PrecivityAD assays quantified baseline plasma Aß42/40. Results: IICV was associated with concurrent/baseline performance on several outcomes but did not modify associations between age and cognitive decline. In contrast, plasma Aß42/40 was unrelated to baseline cognitive performance, but a pattern emerged in interactions with age in longitudinal models of Trails A and B and Rey Auditory Verbal Learning Test total learning trials. Although not significant after correcting for multiple comparisons, low Aß42/40 was associated with faster cognitive declines over time. Discussion: Our results are promising as they extend existing findings to an Black American sample using low-cost, low-burden methods that can be implemented outside of a research center, thus supporting efforts for inclusive AD biomarker research.