Preanalytical sample handling recommendations for Alzheimer's disease plasma biomarkers

Liver as a new target organ in Alzheimer's disease: insight from cholesterol metabolism and its role in amyloid-beta clearance

Alzheimer's disease, the primary cause of dementia, is characterized by neuropathologies, such as amyloid plaques, synaptic and neuronal degeneration, and neurofibrillary tangles. Although amyloid plaques are the primary characteristic of Alzheimer's disease in the central nervous system and peripheral organs, targeting amyloid-beta clearance in the central nervous system has shown limited clinical efficacy in Alzheimer's disease treatment. Metabolic abnormalities are commonly observed in patients with Alzheimer's disease. The liver is the primary peripheral organ involved in amyloid-beta metabolism, playing a crucial role in the pathophysiology of Alzheimer's disease. Notably, impaired cholesterol metabolism in the liver may exacerbate the development of Alzheimer's disease. In this review, we explore the underlying causes of Alzheimer's disease and elucidate the role of the liver in amyloid-beta clearance and cholesterol metabolism. Furthermore, we propose that restoring normal cholesterol metabolism in the liver could represent a promising therapeutic strategy for addressing Alzheimer's disease.

Advances in Blood Biomarkers for Alzheimer's Disease: Ultra-Sensitive Detection Technologies and Impact on Clinical Diagnosis

Alzheimer's disease has escalated into a critical public health concern, marked by its neurodegenerative nature that progressively diminishes cognitive abilities. Recognized as a continuously advancing and presently incurable condition, AD underscores the necessity for early-stage diagnosis and interventions aimed at delaying the decline in mental function. Despite the proven efficacy of cerebrospinal fluid and positron emission tomography in diagnosing AD, their broader utility is constrained by significant costs and the invasive nature of these procedures. Consequently, the innovation of blood biomarkers such as Amyloid-beta, phosphorylated-tau, total-tau et al, distinguished by their high sensitivity, minimal invasiveness, accessibility, and cost-efficiency, emerges as a promising avenue for AD diagnosis. The advent of ultra-sensitive detection methodologies, including single-molecule enzyme-linked immunosorbent assay and immunoprecipitation-mass spectrometry, has revolutionized the detection of AD plasma biomarkers, supplanting previous low-sensitivity techniques. This rapid advancement in detection technology facilitates the more accurate quantification of pathological brain proteins and AD-associated biomarkers in the bloodstream. This manuscript meticulously reviews the landscape of current research on immunological markers for AD, anchored in the National Institute on Aging-Alzheimer's Association AT(N) research framework. It highlights a selection of forefront ultra-sensitive detection technologies now integral to assessing AD blood immunological markers. Additionally, this review examines the crucial pre-analytical processing steps for AD blood samples that significantly impact research outcomes and addresses the practical challenges faced during clinical testing. These discussions are crucial for enhancing our comprehension and refining the diagnostic precision of AD using blood-based biomarkers. The review aims to shed light on potential avenues for innovation and improvement in the techniques employed for detecting and investigating AD, thereby contributing to the broader field of neurodegenerative disease research.

The appropriate sample-handling procedure for measuring the plasma β-amyloid level using a fully automated immunoassay

Plasma β-amyloid (Aβ) assays are a promising tool for Alzheimer's disease diagnosis in clinical practice. To obtain reliable results, establishing an appropriate sample-handling procedure for each analytical platform is warranted. This study proposes an appropriate sample-handling procedure using HISCL analyzer by elucidating the individual/combined effects of pre-analytical parameters on plasma Aβ42/Aβ40 levels. We investigated the effects of various pre-analytical parameters, including storage times for whole blood, plasma, and freezing conditions, on plasma Aβ42/Aβ40 levels, and confirmed if these values met the acceptable criteria. Plasma Aβ42/Aβ40 levels were acceptable in all conditions. We determined our protocol by confirming that plasma Aβ42/Aβ40 levels remained acceptable when combining pre-analytical parameters. We established an appropriate sample-handling protocol that ensures reliable measurement of plasma Aβ42/Aβ40 levels using HISCL analyzer. We believe the Aβ assay, with our protocol, shows promise for aiding AD diagnosis in clinical settings.

New plasma LC-MS/MS assays for the quantitation of beta-amyloid peptides and identification of apolipoprotein E proteoforms for Alzheimer's disease risk assessment

Early detection of Alzheimer's disease (AD) represents an unmet clinical need. Beta-amyloid (Aβ) plays an important role in AD pathology, and the Aβ42/40 peptide ratio is a good indicator for amyloid deposition. In addition, variants of the apolipoprotein E (APOE) gene are associated with variable AD risk. Here, we describe the development and validation of high-throughput liquid chromatography-tandem mass spectrometry (LC-MS/MS) assays for plasma Aβ40 and Aβ42 quantitation, as well as apolipoprotein E (ApoE) proteotype determination as a surrogate for APOE genotype. Aβ40 and Aβ42 were simultaneously immunoprecipitated from plasma, proteolytically digested, and quantitated by LC-MS/MS. ApoE proteotype status was qualitatively assessed by targeting tryptic peptides from the ApoE2, ApoE3, and ApoE4 proteoforms. Both assays were validated according to the Clinical and Laboratory Standards Institute (CLSI) guidelines. Within-run precision was 1.8%-4.2% (Aβ40), 1.9%-7.2% (Aβ42), and 2.6%-8.3% (Aβ42/40 ratio). Between-run precision was 3.5%-5.9% (Aβ40), 3.8%-8.0% (Aβ42), and 3.3%-8.7% (Aβ42/40 ratio). Both Aβ40 and Aβ42 were linear from 10 to 2500 pg/mL. Identified ApoE proteotypes had 100% concordance with APOE genotypes. We have developed a precise, accurate, and sensitive high-throughput LC-MS/MS assay for plasma Aβ40, Aβ42, and proteoforms of ApoE.

Alzheimer blood biomarkers: practical guidelines for study design, sample collection, processing, biobanking, measurement and result reporting

Alzheimer's disease (AD), the most common form of dementia, remains challenging to understand and treat despite decades of research and clinical investigation. This might be partly due to a lack of widely available and cost-effective modalities for diagnosis and prognosis. Recently, the blood-based AD biomarker field has seen significant progress driven by technological advances, mainly improved analytical sensitivity and precision of the assays and measurement platforms. Several blood-based biomarkers have shown high potential for accurately detecting AD pathophysiology. As a result, there has been considerable interest in applying these biomarkers for diagnosis and prognosis, as surrogate metrics to investigate the impact of various covariates on AD pathophysiology and to accelerate AD therapeutic trials and monitor treatment effects. However, the lack of standardization of how blood samples and collected, processed, stored analyzed and reported can affect the reproducibility of these biomarker measurements, potentially hindering progress toward their widespread use in clinical and research settings. To help address these issues, we provide fundamental guidelines developed according to recent research findings on the impact of sample handling on blood biomarker measurements. These guidelines cover important considerations including study design, blood collection, blood processing, biobanking, biomarker measurement, and result reporting. Furthermore, the proposed guidelines include best practices for appropriate blood handling procedures for genetic and ribonucleic acid analyses. While we focus on the key blood-based AD biomarkers for the AT(N) criteria (e.g., amyloid-beta [Aβ]40, Aβ42, Aβ42/40 ratio, total-tau, phosphorylated-tau, neurofilament light chain, brain-derived tau and glial fibrillary acidic protein), we anticipate that these guidelines will generally be applicable to other types of blood biomarkers. We also anticipate that these guidelines will assist investigators in planning and executing biomarker research, enabling harmonization of sample handling to improve comparability across studies.

Prognostic biomarkers associated with immune checkpoint inhibitors in hepatocellular carcinoma

The treatment of hepatocellular carcinoma (HCC), particularly advanced HCC, has been a serious challenge. Immune checkpoint inhibitors (ICIs) are landmark drugs in the field of cancer therapy in recent years, which have changed the landscape of cancer treatment. In the field of HCC treatment, this class of drugs has shown good therapeutic prospects. For example, atezolizumab in combination with bevacizumab has been approved as first-line treatment for advanced HCC due to significant efficacy. However, sensitivity to ICI therapy varies widely among HCC patients. Therefore, there is an urgent need to search for determinants of resistance/sensitivity to ICIs and to screen biomarkers that can predict the efficacy of ICIs. This manuscript reviews the research progress of prognostic biomarkers associated with ICIs in HCC in order to provide a scientific basis for the development of clinically individualised precision medication regimens.

Biomarkers of Alzheimer's disease and neurodegeneration in dried blood spots-A new collection method for remote settings

BACKGROUND

We aimed to evaluate the precision of Alzheimer's disease (AD) and neurodegeneration biomarker measurements from venous dried plasma spots (DPSv enous) for the diagnosis and monitoring of neurodegenerative diseases in remote settings.

METHODS

In a discovery (n = 154) and a validation cohort (n = 115), glial fibrillary acidic protein (GFAP); neurofilament light (NfL); amyloid beta (Aβ) 40, Aβ42; and phosphorylated tau (p-tau181 and p-tau217) were measured in paired DPSvenous and ethylenediaminetetraacetic acid plasma samples with single-molecule array. In the validation cohort, a subset of participants (n = 99) had cerebrospinal fluid (CSF) biomarkers.

RESULTS

All DPSvenous and plasma analytes correlated significantly, except for Aβ42. In the validation cohort, DPSvenous GFAP, NfL, p-tau181, and p-tau217 differed between CSF Aβ-positive and -negative individuals and were associated with worsening cognition.

DISCUSSION

Our data suggest that measuring blood biomarkers related to AD pathology and neurodegeneration from DPSvenous extends the utility of blood-based biomarkers to remote settings with simplified sampling conditions, storage, and logistics.

HIGHLIGHTS

A wide array of biomarkers related to Alzheimer's disease (AD) and neurodegeneration were detectable in dried plasma spots (DPSvenous). DPSvenous biomarkers correlated with standard procedures and cognitive status. DPSvenous biomarkers had a good diagnostic accuracy discriminating amyloid status. Our findings show the potential interchangeability of DPSvenous and plasma sampling. DPSvenous may facilitate remote and temperature-independent sampling for AD biomarker measurement. Innovative tools for blood biomarker sampling may help recognizing the earliest changes of AD.

CSF and plasma Aβ42/40 across Alzheimer's disease continuum: comparison of two ultrasensitive Simoa® assays targeting distinct amyloid regions

OBJECTIVES

Decreased cerebrospinal fluid (CSF) amyloid beta 42/40 ratio (Aβ42/40) is one of the core Alzheimer's disease (AD) biomarkers. Measurement of Aβ42/40 in plasma has also been proposed as a surrogate marker for amyloidosis, however the validity and the diagnostic performance of this biomarker is still uncertain. Here we evaluated two immunoassays targeting distinct regions of the amyloid peptides by (a) performing a method comparison in both CSF and plasma, and (b) assessing the diagnostic performance across the AD continuum.

METHODS

We used N4PE and N3PA Simoa® assays to measure Aβ42/40 in CSF and plasma of 134 patients: preclinical AD (pre-AD, n=19), mild cognitive impairment due to AD (MCI-AD, n=41), AD at the dementia stage (AD-dem, n=35), and a control group (CTRL, n=39). The N4PE includes a detector antibody targeting the amyloid N-terminus, while the N3PA uses a detector targeting amyloid mid-region.

RESULTS

Method comparison of N4PE and N3PA assays revealed discrepancies in assessment of plasma Aβ42/Aβ40. While the diagnostic performance of the two assays did not significantly differ in CSF, in plasma, N4PE assay provided better accuracy for AD discrimination than N3PA assay (AUC AD-dem vs. CTRL 0.77 N4PE, 0.68 N3PA).

CONCLUSIONS

While both Aβ42/40 assays allowed for an effective discrimination between CTRL and different AD stages, the assay targeting amyloid N-terminal region provided the best diagnostic performance in plasma. Differences observed in technical and diagnostic performance of the two assays may depend on matrix-specific amyloid processing, suggesting that further studies should be carried to standardize amyloid ratio measurement in plasma.

Mitochondria-Related Candidate Genes and Diagnostic Model to Predict Late-Onset Alzheimer's Disease and Mild Cognitive Impairment

Background

Late-onset Alzheimer's disease (LOAD) is the most common type of dementia, but its pathogenesis remains unclear, and there is a lack of simple and convenient early diagnostic markers to predict the occurrence.

Objective

Our study aimed to identify diagnostic candidate genes to predict LOAD by machine learning methods.

Methods

Three publicly available datasets from the Gene Expression Omnibus (GEO) database containing peripheral blood gene expression data for LOAD, mild cognitive impairment (MCI), and controls (CN) were downloaded. Differential expression analysis, the least absolute shrinkage and selection operator (LASSO), and support vector machine recursive feature elimination (SVM-RFE) were used to identify LOAD diagnostic candidate genes. These candidate genes were then validated in the validation group and clinical samples, and a LOAD prediction model was established.

Results

LASSO and SVM-RFE analyses identified 3 mitochondria-related genes (MRGs) as candidate genes, including NDUFA1, NDUFS5, and NDUFB3. In the verification of 3 MRGs, the AUC values showed that NDUFA1, NDUFS5 had better predictability. We also verified the candidate MRGs in MCI groups, the AUC values showed good performance. We then used NDUFA1, NDUFS5 and age to build a LOAD diagnostic model and AUC was 0.723. Results of qRT-PCR experiments with clinical blood samples showed that the three candidate genes were expressed significantly lower in the LOAD and MCI groups when compared to CN.

Conclusion

Two mitochondrial-related candidate genes, NDUFA1 and NDUFS5, were identified as diagnostic markers for LOAD and MCI. Combining these two candidate genes with age, a LOAD diagnostic prediction model was successfully constructed.

Optimized Pre-analytical Handling Protocol for Blood-Based Biomarkers of Alzheimer's Disease

The therapeutic management of patients with Alzheimer's disease (AD) has been hindered by poor diagnostic accuracy. As such, there is an unmet clinical need for tools that can detect and diagnose the disease in its early stages. Compared with cerebrospinal fluid (CSF)-based biomarkers or positron emission tomography (PET), the use of reliable blood-based biomarkers could offer an accessible and minimally invasive method of streamlining diagnosis in the clinical setting. However, the influence of pre-analytical processing and sample handling parameters on the accurate measurement of protein biomarkers is well established, especially for AD CSF-based biomarkers. In this chapter, we provide recommendations for an optimal sample handling protocol for the analysis of blood-based biomarkers specifically for amyloid pathology in AD.

Translating blood biomarkers into clinical practice for Alzheimer's disease: Challenges and perspectives

Early and accurate diagnosis of Alzheimer's disease (AD) in clinical practice is urgent with advances in AD treatment. Blood biomarker assays are preferential diagnostic tools for widespread clinical use with the advantages of being less invasive, cost effective, and easily accessible, and they have shown good performance in research cohorts. However, in community-based populations with maximum heterogeneity, great challenges are still faced in diagnosing AD based on blood biomarkers in terms of accuracy and robustness. Here, we analyze these challenges, including the confounding impact of systemic and biological factors, small changes in blood biomarkers, and difficulty in detecting early changes. Furthermore, we provide perspectives on several potential strategies to overcome these challenges for blood biomarkers to bridge the gap from research to clinical practice.

Effects of storage conditions on the stability of blood-based markers for the diagnosis of Alzheimer's disease

OBJECTIVES

Alzheimer's disease (AD) is considered the most common cause of dementia in older people. Recently, blood-based markers (BBM) Aβ1-42, Aβ1-40, and phospho Tau181 (p-Tau181) have demonstrated the potential to transform the diagnosis and prognostic assessment of AD. Our aim was to investigate the effect of different storage conditions on the quantification of these BBM and to evaluate the interchangeability of plasma and serum samples.

METHODS

Forty-two individuals with some degree of cognitive impairment were studied. Thirty further patients were retrospectively selected. Aβ1-42, Aβ1-40, and p-Tau181 were quantified using the LUMIPULSE-G600II automated platform. To assess interchangeability between conditions, correction factors for magnitudes that showed strong correlations were calculated, followed by classification consistency studies.

RESULTS

Storing samples at 4 °C for 8-9 days was associated with a decrease in Aβ fractions but not when stored for 1-2 days. Using the ratio partially attenuated the pre-analytical effects. For p-Tau181, samples stored at 4 °C presented lower concentrations, whereas frozen samples presented higher ones. Concerning classification consistency in comparisons that revealed strong correlations (p-Tau181), the percentage of total agreement was greater than 90 % in a large number of the tested cut-offs values.

CONCLUSIONS

Our findings provide relevant information for the standardization of sample collection and storage in the analysis of AD BBM in an automated platform. This knowledge is crucial to ensure their introduction into clinical settings.

Alzheimer's disease biomarkers in cerebrospinal fluid are stable with the Elecsys immunoassay to most pre-analytical influencing factors except freezing at -80 °C

BACKGROUND

Alzheimer´s disease is considered a neurodegenerative disease and is diagnosed by exclusion, while the detection of specific cerebrospinal fluid (CSF) biomarkers, namely amyloid-beta (Aβ) peptides Aβ1-42 (Aß42), phospho-tau (181P; P-tau), and total-tau (T-tau), has been shown to improve diagnostic accuracy. Recently, a new generation of sample tubes (Sarstedt false-bottom tubes) for the Elecsys CSF immunoassay for the determination of Alzheimer´s disease biomarkers in CSF was introduced, promising better measurability. However, the pre-analytic influencing factors have not yet been sufficiently investigated.

METHODS

In 29 patients without Alzheimer's disease diagnosis, CSF concentrations of Aß42, P-tau and T-tau were examined in native CSF and after different influencing interventions using the Elecsys immunoassay test method. The following influencing factors were analyzed: contamination with blood (10,000 and 20,000 erythrocytes/µl CSF), 14-day storage at 4 °C, blood contamination of CSF and 14-day storage at 4 °C, 14-day freezing at -80 °C in Sarstedt tubes or glass vials, 3-month intermediate storage at -80 °C in glass vials.

RESULTS

Both storage at -80 °C for 14 days in Sarstedt false-bottom tubes and in glass vials and storage at -80 °C for 3 months in glass vials resulted in significant decreases in Aß42 (13% after 14 days in Sarstedt and 22% in glass vials, 42% after 3 months in glass vials), P-tau (9% after 14 days in Sarstedt and 13% in glass vials, 12% after 3 months in glass vials) and T-tau (12% after 14 days in Sarstedt and 19% in glass vials, 20% after 3 months in glass vials) concentrations in CSF. No significant differences were found for the other pre-analytical influencing factors.

CONCLUSIONS

Measurements of the concentrations of Aß42, P-tau, and T-tau in CSF with use of the Elecsys immunoassay are robust to the pre-analytical influencing factors of blood contamination and duration of storage. Freezing at -80 °C results in significant reduction of biomarker concentrations regardless of the storage tube and must be considered in retrospective analysis.

Preanalytical stability of plasma biomarkers for Alzheimer's disease pathology

Introduction

Plasma tests have demonstrated high diagnostic accuracy for identifying Alzheimer's disease pathology. To facilitate the transition to clinical utility, we assessed whether plasma storage duration and temperature affect the biomarker concentrations.

Methods

Plasma samples from 13 participants were stored at +4°C and +18°C. Concentrations of six biomarkers were measured after 2, 4, 6, 8, 10, and 24 h by single molecule array assays.

Results

Phosphorylated tau 181 (p-tau181), phosphorylated tau 231 (p-tau231), neurofilament light (NfL), and glial fibrillary acidic protein (GFAP) concentrations were unchanged both when stored at +4°C and +18°C. Amyloid-β 40 (Aβ40) and amyloid-β 42 (Aβ42) concentrations were stable for 24 h at +4°C but declined when stored at +18°C for longer than 6 h. This decline did not affect the Aβ42/Aβ40 ratio.

Discussion

Plasma samples can be stored for 24 h at +4°C or +18°C and result in valid assay results for p-tau181, p-tau231, Aβ42/Aβ40 ratio, GFAP, and NfL.

HIGHLIGHTS

Plasma samples were stored for 24 h at +4°C and +18°C, mimicking clinical practice.Concentrations for Alzheimer's disease biomarkers were measured at six time-points.p-tau181, p-tau231, NfL, and GFAP concentrations were unchanged during the experiment.Storage at +18°C affected Aβ40 and Aβ42 concentrations while storage at +4°C did not. The Aβ42/Aβ40 ratio was unaffected.These plasma tests seem suitable for use in general practice.

An accurate fully automated panel of plasma biomarkers for Alzheimer's disease

INTRODUCTION

There is a great need for fully automated plasma assays that can measure amyloid beta (Aβ) pathology and predict future Alzheimer's disease (AD) dementia.

METHODS

Two cohorts (n = 920) were examined: Panel A+ (n = 32 cognitively unimpaired [CU], n = 106 mild cognitive impairment [MCI], and n = 89 AD) and BioFINDER-1 (n = 461 CU, n = 232 MCI). Plasma Aβ42/Aβ40, phosphorylated tau (p-tau)181, two p-tau217 variants, ApoE4 protein, neurofilament light, and GFAP were measured using Elecsys prototype immunoassays.

RESULTS

The best biomarker for discriminating Aβ-positive versus Aβ-negative participants was Aβ42/Aβ40 (are under the curve [AUC] 0.83-0.87). Combining Aβ42/Aβ40, p-tau181, and ApoE4 improved the AUCs significantly (0.90 to 0.93; P< 0.01). Adding additional biomarkers had marginal effects (ΔAUC ≤0.01). In BioFINDER, p-tau181, p-tau217, and ApoE4 predicted AD dementia within 6 years in CU (AUC 0.88) and p-tau181, p-tau217, and Aβ42/Aβ40 in MCI (AUC 0.87).

DISCUSSION

The high accuracies for Aβ pathology and future AD dementia using fully automated instruments are promising for implementing plasma biomarkers in clinical trials and clinical routine.

Impact of pre-analytical sample handling factors on plasma biomarkers of Alzheimer's disease

An unmet need exists for reliable plasma biomarkers of amyloid pathology, in the clinical laboratory setting, to streamline diagnosis of Alzheimer's disease (AD). For routine clinical use, a biomarker must provide robust and reliable results under pre-analytical sample handling conditions. We investigated the impact of different pre-analytical sample handling procedures on the levels of seven plasma biomarkers in development for potential routine use in AD. Using (1) fresh (never frozen) and (2) previously frozen plasma, we evaluated the effects of (A) storage time and temperature, (B) freeze/thaw (F/T) cycles, (C) anticoagulants, (D) tube transfer, and (E) plastic tube types. Blood samples were prospectively collected from patients with cognitive impairment undergoing investigation in a memory clinic. β-amyloid 1-40 (Aβ40), β-amyloid 1-42 (Aβ42), apolipoprotein E4, glial fibrillary acidic protein, neurofilament light chain, phosphorylated-tau (phospho-tau) 181, and phospho-tau-217 were measured using Elecsys^® plasma prototype immunoassays. Recovery signals for each plasma biomarker and sample handling parameter were calculated. For all plasma biomarkers measured, pre-analytical effects were comparable between fresh (never frozen) and previously frozen samples. All plasma biomarkers tested were stable for ≤24 h at 4°C when stored as whole blood and ethylenediaminetetraacetic acid (EDTA) plasma. Recovery signals were acceptable for up to five tube transfers, or two F/T cycles, and in both polypropylene and low-density polyethylene tubes. For all plasma biomarkers except Aβ42 and Aβ40, analyte levels were largely comparable between EDTA, lithium heparin, and sodium citrate tubes. Aβ42 and Aβ40 were most sensitive to pre-analytical handling, and the effects could only be partially compensated by the Aβ42/Aβ40 ratio. We provide recommendations for an optimal sample handling protocol for analysis of plasma biomarkers for amyloid pathology AD, to improve the reproducibility of future studies on plasma biomarkers assays and for potential use in routine clinical practice.

Blood Biomarkers Discriminate Cerebral Amyloid Status and Cognitive Diagnosis when Collected with ACD-A Anticoagulant

BACKGROUND

The development of biomarkers that are easy to collect, process, and store is a major goal of research on current Alzheimer's Disease (AD) and underlies the growing interest in plasma biomarkers. Biomarkers with these qualities will improve diagnosis and allow for better monitoring of therapeutic interventions. However, blood collection strategies have historically differed between studies. We examined the ability of various ultrasensitive plasma biomarkers to predict cerebral amyloid status in cognitively unimpaired individuals when collected using acid citrate dextrose (ACD). We then examined the ability of these biomarkers to predict cognitive impairment independent of amyloid status.

METHODS

Using a cross-sectional study design, we measured amyloid beta 42/40 ratio, pTau-181, neurofilament-light, and glial fibrillary acidic protein using the Quanterix Simoa® HD-X platform. To evaluate the discriminative accuracy of these biomarkers in determining cerebral amyloid status, we used both banked plasma and 18F-AV45 PET cerebral amyloid neuroimaging data from 140 cognitively unimpaired participants. We further examined their ability to discriminate cognitive status by leveraging data from 42 cognitively impaired older adults. This study is the first, as per our knowledge, to examine these specific tests using plasma collected using acid citrate dextrose (ACD), as well as the relationship with amyloid PET status.

RESULTS

Plasma AB42/40 had the highest AUC (0.833, 95% C.I. 0.767-0.899) at a cut-point of 0.0706 for discriminating between the two cerebral amyloid groups (sensitivity 76%, specificity 78.5%). Plasma NFL at a cut-point of 20.58pg/mL had the highest AUC (0.908, 95% CI 0.851- 0.966) for discriminating cognitive impairment (sensitivity 84.8%, specificity 89.9%). The addition of age and apolipoprotein e4 status did not improve the discriminative accuracy of these biomarkers.

CONCLUSION

Our results suggest that the Aβ42/40 ratio is useful in discriminating clinician-rated elevated cerebral amyloid status and that NFL is useful for discriminating cognitive impairment status. These findings reinforce the growing body of evidence regarding the general utility of these biomarkers and extend their utility to plasma collected in a non-traditional anticoagulant.

Pre-Analytical Variables Influencing Stability of Blood-Based Biomarkers of Neuropathology

BACKGROUND

Sample collection and preanalytical protocols may significantly impact the results of large-scale epidemiological studies incorporating blood-based biomarkers of neuropathology.

OBJECTIVE

To evaluate the stability and assay variability of several blood-based biomarkers of neuropathology for common preanalytical conditions.

METHODS

We collected serum and plasma samples from 41 participants and evaluated the effect of processing delay of up to 72 h when stored at 4∘C, three freeze-thaw cycles, and a combination of 48-h processing delay when stored at 4∘C and three freeze-thaw cycles on biomarker stability. Using the Simoa assay (Quanterix Inc.), we measured amyloid-β 40 (Aβ40), amyloid-β 42 (Aβ42), neurofilament light (NfL), glial fibrillary acidic protein (GFAP), and phosphorylated tau 181 (p-tau-181).

RESULTS

We found that Aβ40 and Aβ42 levels significantly decreased after a 24-h processing delay in both plasma and serum samples, and a single freeze-thaw cycle (p < 0.0001). Nevertheless, serum Aβ42/40 ratio remained stable with a processing delay up to 48 h while plasma Aβ42/40 ratio showed only small but significant increase with a delay up to 72 h. Both plasma and serum GFAP and NfL levels were only modestly affected by processing delay and freeze-thaw cycles. Plasma p-tau-181 levels notably increased with a 24-, 48-, and 72-h processing delay, but remained stable in serum. Intra-individual variation over two weeks was minimal for all biomarkers and their levels were substantially lower in serum when compared with plasma.

CONCLUSION

These results suggest that standardizing preanalytical variables will allow robust measurements of biomarkers of neuropathology in population studies.

Feasibility and preliminary effects of exercise interventions on plasma biomarkers of Alzheimer's disease in the FIT-AD trial: a randomized pilot study in older adults with Alzheimer's dementia

BACKGROUND

Alzheimer's disease (AD) biomarkers have provided a unique opportunity to understand AD pathogenesis and monitor treatment responses. However, exercise trials show mixed effects on imagining and cerebrospinal fluid biomarkers of AD. The feasibility and effects of exercise on plasma biomarkers remain unknown. The primary objective of this study was to examine the feasibility of recruitment, retention, and blood sample collection in community-dwelling older adults with mild-to-moderate AD dementia. Secondarily, it estimated the preliminary effects of 6-month aerobic and stretching exercise on plasma amyloid-β42 and Aβ40 (Aβ42/40) ratio, phosphorylated tau (p-tau) 181, and total tau (t-tau).

METHODS

This pilot study was implemented in year 2 of the 2-parallel group FIT-AD trial that randomized 96 participants on a 2:1 allocation ratio to moderate-intensity cycling or low-intensity stretching for 20-50 min, 3 times/week for 6 months with 6-month follow-up. Investigators (except for the statistician) and data collectors were blinded to group assignment. Fasting blood samples were collected from 26 participants at baseline and 3 and 6 months. Plasma Aβ42, Aβ40, p-tau181, and t-tau were measured using Simoa™ assays. Data were analyzed using intention-to-treat, Cohen's d, and linear mixed models.

RESULTSS

The sample averaged 77.6±6.99 years old and 15.4±3.00 years of education with 65% being male and 96.2% being apolipoprotein epsilon 4 gene carriers. The recruitment rate was 76.5%. The retention rate was 100% at 3 months and 96.2% at 6 months. The rate of blood collection was 88.5% at 3 months and 96.2% at 6 months. Means (standard deviation) of within-group 6-month difference in the stretching and cycling group were 0.001 (0.012) and -0.001 (0.010) for Aβ42/40 ratio, 0.609 (1.417) pg/mL and 0.101(1.579) pg/mL for p-tau181, and -0.020 (0.279) pg/mL and -0.075 (0.215) pg/mL for t-tau. Effect sizes for within-group 6-month difference were observed for p-tau181 in stretching (d=0.43 [-0.33, 1.19]) and t-tau in cycling (-0.35 [-0.87, 0.17]).

CONCLUSIONS

Blood collections with fasting were well received by participants and feasible with high recruitment and retention rates. Plasma biomarkers of AD may be modifiable by exercise intervention. Important design considerations are provided for future Phase III trials.

TRIALS REGISTRATION

ClinicalTrials.gov Identifier: NCT01954550 and posted on October 1, 2013.

New developments of biofluid-based biomarkers for routine diagnosis and disease trajectories in frontotemporal dementia

Frontotemporal dementia (FTD) covers a spectrum of neurodegenerative disorders with different phenotypes, genetic backgrounds, and pathological states. Its clinicopathological diversity challenges the diagnostic process and the execution of clinical trials, calling for specific diagnostic biomarkers of pathologic FTD types. There is also a need for biomarkers that facilitate disease staging, quantification of severity, monitoring in clinics and observational studies, and for evaluation of target engagement and treatment response in clinical trials. This review discusses current FTD biofluid-based biomarker knowledge taking into account the differing applications. The limitations, knowledge gaps, and challenges for the development and implementation of such markers are also examined. Strategies to overcome these hurdles are proposed, including the technologies available, patient cohorts, and collaborative research initiatives. Access to robust and reliable biomarkers that define the exact underlying pathophysiological FTD process will meet the needs for specific diagnosis, disease quantitation, clinical monitoring, and treatment development.

Clinical performance and robustness evaluation of plasma amyloid-β42/40 prescreening

INTRODUCTION

Further evidence is needed to support the use of plasma amyloid β (Aβ) biomarkers as Alzheimer's disease prescreening tools. This study evaluated the clinical performance and robustness of plasma Aβ₄₂ /Aβ₄₀ for amyloid positivity prescreening.

METHODS

Data were collected from 333 BioFINDER and 121 Alzheimer's Disease Neuroimaging Initiative study participants. Risk and predictive values versus percentile of plasma Aβ₄₂ /Aβ₄₀ evaluated the actionability of plasma Aβ₄₂ /Aβ₄₀ , and simulations modeled the impact of potential uncertainties and biases. Amyloid PET was the brain amyloidosis reference standard.

RESULTS

Elecsys plasma Aβ₄₂ /Aβ₄₀ could potentially rule out amyloid pathology in populations with low-to-moderate amyloid positivity prevalence. However, simulations showed small measurement or pre-analytical errors in Aβ₄₂ and/or Aβ₄₀ cause misclassifications, impacting sensitivity or specificity. The minor fold change between amyloid PET positive and negative cases explains the biomarkers low robustness.

DISCUSSION

Implementing plasma Aβ₄₂ /Aβ₄₀ for routine clinical use may pose significant challenges, with misclassification risks.

HIGHLIGHTS

Plasma Aβ₄₂ /Aβ₄₀ ruled out amyloid PET positivity in a setting of low amyloid-positive prevalence. Including (pre-) analytical errors or measurement biases caused misclassifications. Plasma Aβ₄₂ /Aβ₄₀ had a low inherent dynamic range, independent of analytical method. Other blood biomarkers may be easier to implement as robust prescreening tools.

A Review of Application of Aβ42/40 Ratio in Diagnosis and Prognosis of Alzheimer’s Disease

The number of patients with Alzheimer’s disease (AD) and non-Alzheimer’s disease (non-AD) has drastically increased over recent decades. The amyloid cascade hypothesis attributes a vital role to amyloid-β protein (Aβ) in the pathogenesis of AD. As the main pathological hallmark of AD, amyloid plaques consist of merely the 42 and 40 amino acid variants of Aβ (Aβ 42 and Aβ 40). The cerebrospinal fluid (CSF) biomarker Aβ 42/40 has been extensively investigated and eventually integrated into important diagnostic tools to support the clinical diagnosis of AD. With the development of highly sensitive assays and technologies, blood-based Aβ 42/40, which was obtained using a minimally invasive and cost-effective method, has been proven to be abnormal in synchrony with CSF biomarker values. This paper presents the recent progress of the CSF Aβ 42/40 ratio and plasma Aβ 42/40 for AD as well as their potential clinical application as diagnostic markers or screening tools for dementia.

Plasma P-Tau181 for the Discrimination of Alzheimer’s Disease from Other Primary Dementing and/or Movement Disorders

Blood phospho-tau181 may offer a useful biomarker for Alzheimer’s disease. However, the use of either serum or plasma phospho-tau181 and their diagnostic value are currently under intense investigation. In a pilot study, we measured both serum and plasma phospho-tau181 (pT181-Tau) by single molecule array (Simoa) in a group of patients with Alzheimer’s disease and a mixed group of patients with other primary dementing and/or movement disorders. Classical cerebrospinal fluid biomarkers were also measured. Plasma (but not serum) pT181-Tau showed a significant increase in Alzheimer’s disease and correlated significantly with cerebrospinal fluid amyloid and pT181-Tau. Receiver operating curve analysis revealed a significant discrimination of Alzheimer’s from non-Alzheimer’s disease patients, with an area under the curve of 0.83 and an excellent sensitivity but a moderate specificity. Plasma pT181-Tau is not an established diagnostic biomarker for Alzheimer’s disease, but it could become one in the future, or it may serve as a screening tool for specific cases of patients or presymptomatic subjects.

Plasma Phospho-Tau-181 as a Diagnostic Aid in Alzheimer’s Disease

Cerebrospinal fluid (CSF) biomarkers remain the gold standard for fluid-biomarker-based diagnosis of Alzheimer’s disease (AD) during life. Plasma biomarkers avoid lumbar puncture and allow repeated sampling. Changes of plasma phospho-tau-181 in AD are of comparable magnitude and seem to parallel the changes in CSF, may occur in preclinical or predementia stages of the disease, and may differentiate AD from other causes of dementia with adequate accuracy. Plasma phospho-tau-181 may offer a useful alternative to CSF phospho-tau determination, but work still has to be done concerning the optimal method of determination with the highest combination of sensitivity and specificity and cost-effect parameters.

Higher cerebrospinal fluid biomarkers of neuronal injury in HIV-associated neurocognitive impairment

We evaluated whether biomarkers of age-related neuronal injury and amyloid metabolism are associated with neurocognitive impairment (NCI) in people with and without HIV (PWH, PWoH). This was a cross-sectional study of virally suppressed PWH and PWoH. NCI was assessed using a validated test battery; global deficit scores (GDS) quantified overall performance. Biomarkers in cerebrospinal fluid (CSF) were quantified by immunoassay: neurofilament light (NFL), total Tau (tTau), phosphorylated Tau 181 (pTau181), amyloid beta (Aβ)42, and Aβ40. Factor analysis was used to reduce biomarker dimensionality. Participants were 256 virally suppressed PWH and 42 PWoH, 20.2% female, 17.1% Black, 7.1% Hispanic, 60.2% non-Hispanic White, and 15.6% other race/ethnicities, mean (SD) age 56.7 (6.45) years. Among PWH, the best regression model for CSF showed that higher tTau (β = 0.723, p = 3.79e-5) together with lower pTau181 (β = −0.510, p = 0.0236) best-predicted poor neurocognitive performance. In univariable analysis, only higher tTau was significantly correlated with poor neurocognitive performance (tTau r = 0.214, p = 0.0006; pTau181 r = 0.00248, p = 0.969). Among PWoH, no CSF biomarkers were significantly associated with worse NCI. Predicted residual error sum of squares (PRESS) analysis showed no evidence of overfitting. Poorer neurocognitive performance in aging PWH was associated with higher CSF tTau, a marker of age-related neuronal injury, but not with biomarkers of amyloid metabolism. The findings suggest that HIV might interact with age-related neurodegeneration to contribute to cognitive decline in PWH.

Machine Learning Reveals a Multipredictor Nomogram for Diagnosing the Alzheimer's Disease Based on Chemiluminescence Immunoassay for Total Tau in Plasma

Background

Predicting amnestic mild cognitive impairment (aMCI) in conversion and Alzheimer's disease (AD) remains a daunting task. Standard diagnostic procedures for AD population are reliant on neuroimaging features (positron emission tomography, PET), cerebrospinal fluid (CSF) biomarkers (Aβ1-42, T-tau, P-tau), which are expensive or require invasive sampling. The blood-based biomarkers offer the opportunity to provide an alternative approach for easy diagnosis of AD, which would be a less invasive and cost-effective screening tool than currently approved CSF or amyloid β positron emission tomography (PET) biomarkers.

Methods

We developed and validated a sensitive and selective immunoassay for total Tau in plasma. Robust signatures were obtained based on several clinical features selected by multiple machine learning algorithms between the three participant groups. Subsequently, a well-fitted nomogram was constructed and validated, integrating clinical factors and total Tau concentration. The predictive performance was evaluated according to the receiver operating characteristic (ROC) curves and area under the curve (AUC) statistics. Decision curve analysis and calibration curves are used to evaluate the net benefit of nomograms in clinical decision-making.

Results

Under optimum conditions, chemiluminescence analysis (CLIA) displays a desirable dynamic range within Tau concentration from 7.80 to 250 pg/mL with readily achieved higher performances (LOD: 5.16 pg/mL). In the discovery cohort, the discrimination between the three well-defined participant groups according to Tau concentration was in consistent agreement with clinical diagnosis (AD vs. non-MCI: AUC = 0.799; aMCI vs. non-MCI: AUC = 0.691; AD vs. aMCI: AUC = 0.670). Multiple machine learning algorithms identified Age, Gender, EMPG, Tau, ALB, HCY, VB12, and/or Glu as robust signatures. A nomogram integrated total Tau concentration and clinical factors provided better predictive performance (AD vs. non-MCI: AUC = 0.960, AD vs. aMCI: AUC = 0.813 in discovery cohort; AD vs. non-MCI: AUC = 0.938, AD vs. aMCI: AUC = 0.754 in validation cohort).

Conclusion

The developed assay and a satisfactory nomogram model hold promising clinical potential for early diagnosis of aMCI and AD participants.

Diagnostic value of serum versus plasma phospho-tau for Alzheimer's disease

BACKGROUND

Blood phosphorylated tau (p-tau) forms are promising Alzheimer's disease (AD) biomarkers, but validation in matrices other than ethylenediaminetetraacetic acid (EDTA) plasma is limited. Firstly, we assessed the diagnostic potential of p-tau231 and p-tau181 in paired plasma and serum samples. Secondly, we compared serum and cerebrospinal fluid (CSF) samples from biomarker-positive AD and biomarker-negative control participants.

METHODS

We studied three independent cohorts (n=115 total): cohorts 1 and 2 included individuals with paired plasma and serum, while cohort 3 included paired serum and CSF. Blood-based p-tau231 and p-tau181 were measured using in-house or commercial single molecule array (Simoa) methods.

RESULTS

Serum and plasma p-tau231 and p-tau181 were two- to three-fold increased in biomarker-positive AD versus biomarker-negative controls (P≤0.0008). Serum p-tau231 separated diagnostic groups with area under the curve (AUC) of 82.2% (cohort 3) to 88.2% (cohort 1) compared with 90.2% (cohort 1) for plasma. Similarly, p-tau181 showed AUC of 89.6% (cohort 1) to 89.8% (cohort 3) in serum versus 85.4% in plasma (cohort 1). P-tau231 and p-tau181 correlated slightly better in serum (rho=0.92 for cohort 1, 0.93 for cohort 3) than in plasma (rho=0.88, cohort 1). Within-individual p-tau181 (Quanterix) and p-tau231 concentrations were twice higher in plasma versus serum, but p-tau181 (in-house, Gothenburg) levels were not statistically different. Bland-Altman plots revealed that the relative difference between serum/plasma was larger in the lower range. P-tau levels in paired plasma and serum correlated strongly with each other (rho=0.75-0.93) as well as with CSF Aβ₄₂ (rho= -0.56 to -0.59), p-tau and total-tau (rho=0.53-0.73). Based on the results, it seems possible that serum p-tau reflects the same pool of brain-secreted p-tau as in CSF; we estimated that less than 2% of CSF p-tau is found in serum, being same for both controls and AD.

CONCLUSIONS

Comparable diagnostic performances and strong correlations between serum versus plasma pairs suggest that p-tau analyses can be expanded to research cohorts and hospital systems that prefer serum to other blood matrices. However, absolute biomarker concentrations may not be interchangeable, indicating that plasma and serum samples should be used independently. These results should be validated in independent cohorts.

Crosswalk study on blood collection-tube types for Alzheimer's disease biomarkers

INTRODUCTION

Blood-based Alzheimer's disease (AD) biomarkers show promise, but pre-analytical protocol differences may pose problems. We examined seven AD blood biomarkers (amyloid beta [A β ] 42 ,A β 40 ,phosphorylated tau [ p - ta u 181 , total tau [t-tau], neurofilament light chain [NfL],A β 42 40 , andp - ta u 181 A β 42 ) in three collection tube types (ethylenediaminetetraacetic acid [EDTA] plasma, heparin plasma, serum).

METHODS

Plasma and serum were obtained from cerebrospinal fluid or amyloid positron emission tomography-positive and -negative participants (N = 38) in the Wisconsin Registry for Alzheimer's Prevention. We modeled AD biomarker values observed in EDTA plasma versus heparin plasma and serum, and assessed correspondence with brain amyloidosis.

RESULTS

Results suggested bias due to tube type, but crosswalks are possible for some analytes, with excellent model fit for NfL (R 2 = 0.94), adequate for amyloid (R 2 = 0.40-0.69), and weaker for t-tau (R 2 = 0.04-0.42) andp - ta u 181 (R 2 = 0.22-0.29). Brain amyloidosis differentiated several measures, especially EDTA plasmapTa u 181 A β 42 (d = 1.29).

DISCUSSION

AD biomarker concentrations vary by tube type. However, correlations for some biomarkers support harmonization across types, suggesting cautious optimism for use in banked blood.

Blood-based biomarkers for Alzheimer's disease

Neurodegenerative disorders such as Alzheimer's disease (AD) represent a mounting public health challenge. As these diseases are difficult to diagnose clinically, biomarkers of underlying pathophysiology are playing an ever-increasing role in research, clinical trials, and in the clinical work-up of patients. Though cerebrospinal fluid (CSF) and positron emission tomography (PET)-based measures are available, their use is not widespread due to limitations, including high costs and perceived invasiveness. As a result of rapid advances in the development of ultra-sensitive assays, the levels of pathological brain- and AD-related proteins can now be measured in blood, with recent work showing promising results. Plasma P-tau appears to be the best candidate marker during symptomatic AD (i.e., prodromal AD and AD dementia) and preclinical AD when combined with Aβ42/Aβ40. Though not AD-specific, blood NfL appears promising for the detection of neurodegeneration and could potentially be used to detect the effects of disease-modifying therapies. This review provides an overview of the progress achieved thus far using AD blood-based biomarkers, highlighting key areas of application and unmet challenges.

[Biomarkers for the diagnosis of cognitive impairment - Recommendations from the Swiss Memory Clinics]

Biomarkers for the diagnosis of cognitive impairment - Recommendations from the Swiss Memory Clinics Abstract. Molecular cerebrospinal fluid (CSF) biomarkers of neurodegenerative diseases are now part of the established diagnostic tools for the clinical investigation of cognitive disorders in the elderly. Biomarkers allow for earlier and more accurate differential diagnosis, and are recommended by the Swiss Memory Clinics as an additional investigation based upon individual indication. Information and counselling are needed both before and after biomarker-supported diagnosis. The procedures for diagnostic lumbar punctures and pre-analytical sample handling should follow published recommendations. The results must be interpreted in the context of the other available history and assessment outcome. Thanks to recent research progress, blood-based biomarkers and other non-invasive markers are expected to become available for clinical practice in the near future. This trend will likely lead to a much broader utilisation of biomarkers and may accelerate the development of effective and individually tailored prevention and treatment approaches. This review article provides an overview over the current state of biomarkers and provides the recommendations of the Swiss Memory Clinics for their use in clinical practice.

Establishing pre-analytical requirements and maximizing peptide recovery in the analytical phase for mass spectrometric quantification of amyloid-β peptides 1-42 and 1-40 in CSF

OBJECTIVES

Amyloid-β (Aβ) peptides in cerebrospinal fluid (CSF), including Aβ42 (residues 1-42) and Aβ40 (residues 1-40), are utilized as biomarkers in the diagnostic workup of Alzheimer's disease. Careful consideration has been given to the pre-analytical and analytical factors associated with measurement of these peptides via immunoassays; however, far less information is available for mass spectrometric methods. As such, we performed a comprehensive evaluation of pre-analytical and analytical factors specific to Aβ quantification using mass spectrometry.

METHODS

Using our quantitative mass spectrometry assay for Aβ42 and Aβ40 in CSF, we investigated the potential for interference from hemolysate, bilirubin, lipids, and anti-Aβ-antibodies. We also optimized the composition of the calibrator surrogate matrix and Aβ recovery during and after solid phase extraction (SPE).

RESULTS

There was no interreference observed with total protein up to 12 g/L, hemolysate up to 10% (v/v), bilirubin up to 0.5% (v/v), intralipid up to 1% (v/v), or anti-Aβ-antibodies at expected therapeutic concentrations. For hemolysate, bilirubin and lipids, visual CSF contamination thresholds were established. In the analytical phase, Aβ recovery was increased by ∼50% via SPE solvent modifications and by over 150% via modification of the SPE collection plate, which also extended analyte stability in the autosampler.

CONCLUSIONS

Attention to mass spectrometric-specific pre-analytical and analytical considerations improved analytical sensitivity and reproducibility, as well as, established CSF specimen acceptance and rejection criteria for use by the clinical laboratory.

Assessing Plasma Levels of α-Synuclein and Neurofilament Light Chain by Different Blood Preparation Methods

The potential biomarkers of Parkinson’s disease are α-synuclein and neurofilament light chain (NFL). However, inconsistent preanalytical preparation of plasma could lead to variations in levels of these biomarkers. Different types of potassium salts of EDTA and different centrifugation temperatures during plasma preparation may affect the results of α-synuclein and NFL measurements. In this study, we prepared plasma from eight patients with Parkinson’s disease (PD) and seven healthy controls (HCs) by using di- and tri-potassium (K₂- and K₃-) EDTA tubes and recruited a separated cohort with 42 PD patients and 40 HCs for plasma samples prepared from whole blood by centrifugation at room temperature and 4°C, respectively, in K₂-EDTA tubes. The plasma levels of α-synuclein and NFL in K₂- and K₃-EDTA were similar. However, the levels of α-synuclein in the plasma prepared at 4°C (101.57 ± 43.43 fg/ml) were significantly lower compared with those at room temperature (181.23 ± 196.31 fg/ml, P < 0.001). Room temperature preparation demonstrated elevated plasma levels of α-synuclein in PD patients (256.6 ± 50.2 fg/ml) compared with the HCs (102.1 ± 0.66 fg/ml, P < 0.001), whereas this increase in PD was not present by preparation at 4°C. Both plasma preparations at room temperature and 4°C demonstrated consistent results of NFL, which are increased in PD patients compared with HCs. Our findings confirmed that K₂- and K₃-EDTA tubes were interchangeable for analyzing plasma levels of α-synuclein and NFL. Centrifugation at 4°C during plasma preparation generates considerable reduction and variation of α-synuclein level that might hinder the detection of α-synuclein level changes in PD.

Characterization of pre-analytical sample handling effects on a panel of Alzheimer's disease-related blood-based biomarkers: Results from the Standardization of Alzheimer's Blood Biomarkers (SABB) working group

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 (Aβ)42 and 40 peptides with six assays, and Aβ oligomerization‐tendency (OAβ), 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 Aβ 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.

Guidelines for pre-analytical conditions for assessing the methylation of circulating cell-free DNA

Methylation analysis of circulating cell-free DNA (cirDNA), as a liquid biopsy, has a significant potential to advance the detection, prognosis, and treatment of cancer, as well as many genetic disorders. The role of epigenetics in disease development has been reported in several hereditary disorders, and epigenetic modifications are regarded as one of the earliest and most significant genomic aberrations that arise during carcinogenesis. Liquid biopsy can be employed for the detection of these epigenetic biomarkers. It consists of isolation (pre-analytical) and detection (analytical) phases. The choice of pre-analytical variables comprising cirDNA extraction and bisulfite conversion methods can affect the identification of cirDNA methylation. Indeed, different techniques give a different return of cirDNA, which confirms the importance of pre-analytical procedures in clinical diagnostics. Although novel techniques have been developed for the simplification of methylation analysis, the process remains complex, as the steps of DNA extraction, bisulfite treatment, and methylation detection are each carried out separately. Recent studies have noted the absence of any standard method for the pre-analytical processing of methylated cirDNA. We have therefore conducted a comprehensive and systematic review of the important pre-analytical and analytical variables and the patient-related factors which form the basis of our guidelines for analyzing methylated cirDNA in liquid biopsy.

Bias-generating factors in biofluid amyloid-β measurements for Alzheimer's disease diagnosis

Alzheimer's disease (AD) is the most prevalent cause of dementia worldwide, yet the dearth of readily accessible diagnostic biomarkers is a substantial hindrance towards progressing to effective preventive and therapeutic approaches. Due to a long delay between cerebral amyloid-β (Aβ) accumulation and the onset of cognitive impairments, biomarkers that reflect Aβ pathology and enable routine screening for disease progression are of urgent need for application in the clinical diagnosis of AD. According to accumulating evidences, cerebrospinal fluid (CSF) and plasma offer windows to the brain as they allow monitoring of biochemical changes in the brain. Considering the high availability and accuracy in depicting Aβ deposition in the brain, Aβ levels in CSF and plasma are regarded as promising fluid biomarkers for the diagnosis of AD patients at an early stage. However, clinical data with intra- and interindividual variations in the concentrations of CSF and plasma Aβ implicate the need to reevaluate current Aβ detection methods and establish a standardized operating procedure. Therefore, this review introduces three bias-generating factors in biofluid Aβ measurement that may hamper the accurate Aβ quantification and how such complications can be overcome for the widespread implementation of fluid Aβ detection in clinical practice.

Plasma amyloid-β oligomerization assay as a pre-screening test for amyloid status

OBJECTIVE

We assessed the performance of plasma amyloid oligomerization tendency (OAβ) as a marker for abnormal amyloid status. Additionally, we examined long-term storage effects on plasma OAβ.

METHODS

We included 399 subjects regardless of clinical diagnosis from the Amsterdam Dementia Cohort and European Medical Information Framework for AD project (age, 63.8 ± 6.6; 44% female). Amyloid status was determined by visual read on positron emission tomography (PET; nabnormal = 206). Plasma OAβ was measured using the multimer detection system (MDS). Long-term storage effects on MDS-OAβ were assessed using general linear models. Associations between plasma MDS-OAβ and Aβ-PET status were assessed using logistic regression and receiver operating characteristics analyses. Correlations between plasma MDS-OAβ and CSF biomarker levels were evaluated using Pearson correlation analyses.

RESULTS

MDS-OAβ was higher in individuals with abnormal amyloid, and it identified abnormal Aβ-PET with an area under the curve (AUC) of 0.74 (95% CI, 0.67-0.81), especially in samples with a storage duration < 4 years. Combining APOEe4 and age with plasma MDS-OAβ revealed an AUC of 81% for abnormal amyloid PET status (95% CI, 74-87%). Plasma MDS-OAβ correlated negatively with MMSE (r = - 0.29, p < .01) and CSF Aβ42 (r = - 0.20, p < 0.05) and positively with CSF Tau (r = 0.20, p = 0.01).

CONCLUSIONS

Plasma MDS-OAβ combined with APOEe4 and age accurately identifies brain amyloidosis in a large Aβ-confirmed population. Using plasma MDS-OAβ as a screener reduced the costs and number of PET scans needed to screen for amyloidosis, which is relevant for clinical trials. Additionally, plasma MDS-OAβ levels appeared affected by long-term storage duration, which could be of interest for others measuring plasma Aβ biomarkers.

The fluid biomarkers of Alzheimer’s disease

Alzheimer’s disease (AD) is the most common neurodegenerative disorder. However, it still has no available disease‐modifying therapies. Its pathology cascade begins decades before symptomatic presentation. For these reasons, highly sensitive and highly specific fluid biomarkers should be developed for the early diagnosis of AD. In this study, the well‐established and emerging fluid biomarkers of AD are summarized, and recent advances on their role in early diagnosis and progression monitoring as well as their correlations with AD pathology are highlighted. Future prospects and related research directions are also discussed.

The validation status of blood biomarkers of amyloid and phospho-tau assessed with the 5-phase development framework for AD biomarkers

PURPOSE

The development of blood biomarkers that reflect Alzheimer's disease (AD) pathophysiology (phosphorylated tau and amyloid-β) has offered potential as scalable tests for dementia differential diagnosis and early detection. In 2019, the Geneva AD Biomarker Roadmap Initiative included blood biomarkers in the systematic validation of AD biomarkers.

METHODS

A panel of experts convened in November 2019 at a two-day workshop in Geneva. The level of maturity (fully achieved, partly achieved, preliminary evidence, not achieved, unsuccessful) of blood biomarkers was assessed based on the Biomarker Roadmap methodology and discussed fully during the workshop which also evaluated cerebrospinal fluid (CSF) and positron emission tomography (PET) biomarkers.

RESULTS

Plasma p-tau has shown analytical validity (phase 2 primary aim 1) and first evidence of clinical validity (phase 3 primary aim 1), whereas the maturity level for Aβ remains to be partially achieved. Full and partial achievement has been assigned to p-tau and Aβ, respectively, in their associations to ante-mortem measures (phase 2 secondary aim 2). However, only preliminary evidence exists for the influence of covariates, assay comparison and cut-off criteria.

CONCLUSIONS

Despite the relative infancy of blood biomarkers, in comparison to CSF biomarkers, much has already been achieved for phases 1 through 3 - with p-tau having greater success in detecting AD and predicting disease progression. However, sufficient data about the effect of covariates on the biomarker measurement is lacking. No phase 4 (real-world performance) or phase 5 (assessment of impact/cost) aim has been tested, thus not achieved.

Plasma Amyloid Concentration in Alzheimer's Disease: Performance of a High-Throughput Amyloid Assay in Distinguishing Alzheimer's Disease Cases from Controls

Background:

Collection of cerebrospinal fluid (CSF) for measurement of amyloid-β (Aβ) species is a gold standard in Alzheimer’s disease (AD) diagnosis, but has risks. Thus, establishing a low-risk blood Aβ test with high AD sensitivity and specificity is of outmost interest.

Objective:

We evaluated the ability of a commercially available plasma Aβ assay to distinguish AD patients from biomarker-healthy controls.

Method:

In a case-control design, we examined plasma samples from 44 AD patients (A + N+) and 49 controls (A–N–) from a memory clinic. AD was diagnosed using a combination of neuropsychological examination, CSF biomarker analysis and brain imaging. Total Aβ₄₀ and total Aβ₄₂ in plasma were measured through enzyme-linked immunosorbent assay (ELISA) technology using ABtest40 and ABtest42 test kits (Araclon Biotech Ltd.). Receiver operating characteristic (ROC) analyses with outcome AD were performed, and sensitivity and specificity were calculated.

Results:

Plasma Aβ_42/40 was weakly positively correlated with CSF Aβ_42/40 (Spearman’s rho 0.22; p = 0.037). Plasma Aβ_42/40 alone was not able to statistically significantly distinguish between AD patients and controls (AUC 0.58; 95% CI 0.46, 0.70). At a cut-point of 0.076 maximizing sensitivity and specificity, plasma Aβ_42/40 had a sensitivity of 61.2% and a specificity of 63.6%.

Conclusion:

In this sample, the high-throughput blood Aβ assay was not able to distinguish well between AD patients and controls. Whether or not the assay may be useful in large-scale epidemiological settings remains to be seen.

Pre-Analytical Sampling and Storage Conditions of Amyloid-β Peptides in Venous and Capillary Blood

Previous studies on blood-based biomarkers for Alzheimer's disease suggest a less invasive blood test might be a valuable screening tool for Alzheimer-specific pathology. Pre-analytical sample storage conditions seem to play an important role on amyloid-β (Aβ) stability, impacting reliability and reproducibility. This study shows that Aβ40, Aβ42, and Aβ42/40 levels significantly and early decrease during storage at room temperature in whole blood or plasma. Storing blood samples at 4°C leads to stable Aβ peptide concentrations up to 72 h. In addition, Aβ peptides can be measured in capillary blood with a stable Aβ42/40 ratio up to 72 h at 4°C.

MarkVCID cerebral small vessel consortium: I. Enrollment, clinical, fluid protocols

The concept of vascular contributions to cognitive impairment and dementia (VCID) derives from more than two decades of research indicating that (1) most older individuals with cognitive impairment have post mortem evidence of multiple contributing pathologies and (2) along with the preeminent role of Alzheimer's disease (AD) pathology, cerebrovascular disease accounts for a substantial proportion of this contribution. Contributing cerebrovascular processes include both overt strokes caused by etiologies such as large vessel occlusion, cardioembolism, and embolic infarcts of unknown source, and frequently asymptomatic brain injuries caused by diseases of the small cerebral vessels. Cerebral small vessel diseases such as arteriolosclerosis and cerebral amyloid angiopathy, when present at moderate or greater pathologic severity, are independently associated with worse cognitive performance and greater likelihood of dementia, particularly in combination with AD and other neurodegenerative pathologies. Based on this evidence, the US National Alzheimer's Project Act explicitly authorized accelerated research in vascular and mixed dementia along with frontotemporal and Lewy body dementia and AD itself. Biomarker development has been consistently identified as a key step toward translating scientific advances in VCID into effective prevention and treatment strategies. Validated biomarkers can serve a range of purposes in trials of candidate interventions, including (1) identifying individuals at increased VCID risk, (2) diagnosing the presence of cerebral small vessel disease or specific small vessel pathologies, (3) stratifying study participants according to their prognosis for VCID progression or treatment response, (4) demonstrating an intervention's target engagement or pharmacodynamic mechanism of action, and (5) monitoring disease progression during treatment. Effective biomarkers allow academic and industry investigators to advance promising interventions at early stages of development and discard interventions with low success likelihood. The MarkVCID consortium was formed in 2016 with the goal of developing and validating fluid- and imaging-based biomarkers for the cerebral small vessel diseases associated with VCID. MarkVCID consists of seven project sites and a central coordinating center, working with the National Institute of Neurologic Diseases and Stroke and National Institute on Aging under cooperative agreements. Through an internal selection process, MarkVCID has identified a panel of 11 candidate biomarker "kits" (consisting of the biomarker measure and the clinical and cognitive data used to validate it) and established a range of harmonized procedures and protocols for participant enrollment, clinical and cognitive evaluation, collection and handling of fluid samples, acquisition of neuroimaging studies, and biomarker validation. The overarching goal of these protocols is to generate rigorous validating data that could be used by investigators throughout the research community in selecting and applying biomarkers to multi-site VCID trials. Key features of MarkVCID participant enrollment, clinical/cognitive testing, and fluid biomarker procedures are summarized here, with full details in the following text, tables, and supplemental material, and a description of the MarkVCID imaging biomarker procedures in a companion paper, "MarkVCID Cerebral small vessel consortium: II. Neuroimaging protocols." The procedures described here address a range of challenges in MarkVCID's design, notably: (1) acquiring all data under informed consent and enrollment procedures that allow unlimited sharing and open-ended analyses without compromising participant privacy rights; (2) acquiring the data in a sufficiently wide range of study participants to allow assessment of candidate biomarkers across the various patient groups who might ultimately be targeted in VCID clinical trials; (3) defining a common dataset of clinical and cognitive elements that contains all the key outcome markers and covariates for VCID studies and is realistically obtainable during a practical study visit; (4) instituting best fluid-handling practices for minimizing avoidable sources of variability; and (5) establishing rigorous procedures for testing the reliability of candidate fluid-based biomarkers across replicates, assay runs, sites, and time intervals (collectively defined as the biomarker's instrumental validity). Participant Enrollment Project sites enroll diverse study cohorts using site-specific inclusion and exclusion criteria so as to provide generalizable validation data across a range of cognitive statuses, risk factor profiles, small vessel disease severities, and racial/ethnic characteristics representative of the diverse patient groups that might be enrolled in a future VCID trial. MarkVCID project sites include both prospectively enrolling centers and centers providing extant data and samples from preexisting community- and population-based studies. With approval of local institutional review boards, all sites incorporate MarkVCID consensus language into their study documents and informed consent agreements. The consensus language asks prospectively enrolled participants to consent to unrestricted access to their data and samples for research analysis within and outside MarkVCID. The data are transferred and stored as a de-identified dataset as defined by the Health Insurance Portability and Accountability Act Privacy Rule. Similar human subject protection and informed consent language serve as the basis for MarkVCID Research Agreements that act as contracts and data/biospecimen sharing agreements across the consortium. Clinical and Cognitive Data Clinical and cognitive data are collected across prospectively enrolling project sites using common MarkVCID instruments. The clinical data elements are modified from study protocols already in use such as the Alzheimer's Disease Center program Uniform Data Set Version 3 (UDS3), with additional focus on VCID-related items such as prior stroke and cardiovascular disease, vascular risk factors, focal neurologic findings, and blood testing for vascular risk markers and kidney function including hemoglobin A1c, cholesterol subtypes, triglycerides, and creatinine. Cognitive assessments and rating instruments include the Clinical Dementia Rating Scale, Geriatric Depression Scale, and most of the UDS3 neuropsychological battery. The cognitive testing requires ≈60 to 90 minutes. Study staff at the prospectively recruiting sites undergo formalized training in all measures and review of their first three UDS3 administrations by the coordinating center. Collection and Handling of Fluid Samples Fluid sample types collected for MarkVCID biomarker kits are serum, ethylenediaminetetraacetic acid-plasma, platelet-poor plasma, and cerebrospinal fluid (CSF) with additional collection of packed cells to allow future DNA extraction and analyses. MarkVCID fluid guidelines to minimize variability include fasting morning fluid collections, rapid processing, standardized handling and storage, and avoidance of CSF contact with polystyrene. Instrumental Validation for Fluid-Based Biomarkers Instrumental validation of MarkVCID fluid-based biomarkers is operationally defined as determination of intra-plate and inter-plate repeatability, inter-site reproducibility, and test-retest repeatability. MarkVCID study participants both with and without advanced small vessel disease are selected for these determinations to assess instrumental validity across the full biomarker assay range. Intra- and inter-plate repeatability is determined by repeat assays of single split fluid samples performed at individual sites. Inter-site reproducibility is determined by assays of split samples distributed to multiple sites. Test-retest repeatability is determined by assay of three samples acquired from the same individual, collected at least 5 days apart over a 30-day period and assayed on a single plate. The MarkVCID protocols are designed to allow direct translation of the biomarker validation results to multicenter trials. They also provide a template for outside groups to perform analyses using identical methods and therefore allow direct comparison of results across studies and centers. All MarkVCID protocols are available to the biomedical community and intended to be shared. In addition to the instrumental validation procedures described here, each of the MarkVCID kits will undergo biological validation to determine whether the candidate biomarker measures important aspects of VCID such as cognitive function. Analytic methods and results of these validation studies for the 11 MarkVCID biomarker kits will be published separately. The results of this rigorous validation process will ultimately determine each kit's potential usefulness for multicenter interventional trials aimed at preventing or treating small vessel disease related VCID.

Fluid Biomarkers in Clinical Trials for Alzheimer's Disease: Current and Future Application

Alzheimer's disease (AD) research is entering a unique moment in which enormous information about the molecular basis of this disease is being translated into therapeutics. However, almost all drug candidates have failed in clinical trials over the past 30 years. These many trial failures have highlighted a need for the incorporation of biomarkers in clinical trials to help improve the trial design. Fluid biomarkers measured in cerebrospinal fluid and circulating blood, which can reflect the pathophysiological process in the brain, are becoming increasingly important in AD clinical trials. In this review, we first succinctly outline a panel of fluid biomarkers for neuropathological changes in AD. Then, we provide a comprehensive overview of current and future application of fluid biomarkers in clinical trials for AD. We also summarize the many challenges that have been encountered in efforts to integrate fluid biomarkers in clinical trials, and the barriers that have begun to be overcome. Ongoing research efforts in the field of fluid biomarkers will be critical to make significant progress in ultimately unveiling disease-modifying therapies in AD.

Diagnose it yourself: will there be a home test kit for Alzheimer's disease?

Alzheimer's disease is the most common neurodegenerative process leading to dementia. To date, there is no curative approach; thus, establishing a diagnosis as early as possible is necessary to implement preventive measures. However, today's gold standard for diagnosing Alzheimer's disease is high in both cost and effort and is not readily available. This defines the need for low-effort and economic alternatives that give patients low-threshold access to testing systems at their general practitioners or even at home for an independent retrieval of a biologic specimen. This perspective gives an overview of established and novel approaches in the field and speculates on the future of test strategies eventually technically implementable at home.

Moving fluid biomarkers for Alzheimer's disease from research tools to routine clinical diagnostics

Four fluid-based biomarkers have been developed into diagnostic tests for Alzheimer’s disease (AD) pathology: the ratio of 42 to 40 amino acid-long amyloid β, a marker of plaque pathology; total-tau and phosphorylated tau, markers of AD-related changes in tau metabolism and secretion; and neurofilament light, a marker of neurodegeneration. When measured in cerebrospinal fluid, these biomarkers can be used in clinical practice to support a diagnosis of mild cognitive impairment or dementia due to AD. Recently, technological breakthroughs have made it possible to measure them in standard blood samples as well. Here, we give an updated account of the current state of the fluid-based AD biomarker research field. We discuss how the new blood tests may be used in research and clinical practice, and what role they may play in relation to more established diagnostic tests, such as CSF biomarkers and amyloid and tau positron emission tomography, to facilitate the effective implementation of future disease-modifying therapies.

The search for a convenient procedure to detect one of the earliest signs of Alzheimer's disease: A systematic review of the prediction of brain amyloid status

INTRODUCTION

Convenient, cost-effective tests for amyloid beta (Aβ) are needed to identify those at higher risk for developing Alzheimer's disease (AD). This systematic review evaluates recent models that predict dichotomous Aβ. (PROSPERO: CRD42020144734).

METHODS

We searched Embase and identified 73 studies from 29,581 for review. We assessed study quality using established tools, extracted information, and reported results narratively.

RESULTS

We identified few high-quality studies due to concerns about Aβ determination and analytical issues. The most promising convenient, inexpensive classifiers consist of age, apolipoprotein E genotype, cognitive measures, and/or plasma Aβ. Plasma Aβ may be sufficient if pre-analytical variables are standardized and scalable assays developed. Some models lowered costs associated with clinical trial recruitment or clinical screening.

DISCUSSION

Conclusions about models are difficult due to study heterogeneity and quality. Promising prediction models used demographic, cognitive/neuropsychological, imaging, and plasma Aβ measures. Further studies using standardized Aβ determination, and improved model validation are required.

Detection of β-amyloid positivity in Alzheimer's Disease Neuroimaging Initiative participants with demographics, cognition, MRI and plasma biomarkers

In vivo gold standard for the ante-mortem assessment of brain β-amyloid pathology is currently β-amyloid positron emission tomography or cerebrospinal fluid measures of β-amyloid42 or the β-amyloid42/β-amyloid40 ratio. The widespread acceptance of a biomarker classification scheme for the Alzheimer's disease continuum has ignited interest in more affordable and accessible approaches to detect Alzheimer's disease β-amyloid pathology, a process that often slows down the recruitment into, and adds to the cost of, clinical trials. Recently, there has been considerable excitement concerning the value of blood biomarkers. Leveraging multidisciplinary data from cognitively unimpaired participants and participants with mild cognitive impairment recruited by the multisite biomarker study of Alzheimer's Disease Neuroimaging Initiative, here we assessed to what extent plasma β-amyloid42/β-amyloid40, neurofilament light and phosphorylated-tau at threonine-181 biomarkers detect the presence of β-amyloid pathology, and to what extent the addition of clinical information such as demographic data, APOE genotype, cognitive assessments and MRI can assist plasma biomarkers in detecting β-amyloid-positivity. Our results confirm plasma β-amyloid42/β-amyloid40 as a robust biomarker of brain β-amyloid-positivity (area under curve, 0.80-0.87). Plasma phosphorylated-tau at threonine-181 detected β-amyloid-positivity only in the cognitively impaired with a moderate area under curve of 0.67, whereas plasma neurofilament light did not detect β-amyloid-positivity in either group of participants. Clinical information as well as MRI-score independently detected positron emission tomography β-amyloid-positivity in both cognitively unimpaired and impaired (area under curve, 0.69-0.81). Clinical information, particularly APOE ε4 status, enhanced the performance of plasma biomarkers in the detection of positron emission tomography β-amyloid-positivity by 0.06-0.14 units of area under curve for cognitively unimpaired, and by 0.21-0.25 units for cognitively impaired; and further enhancement of these models with an MRI-score of β-amyloid-positivity yielded an additional improvement of 0.04-0.11 units of area under curve for cognitively unimpaired and 0.05-0.09 units for cognitively impaired. Taken together, these multi-disciplinary results suggest that when combined with clinical information, plasma phosphorylated-tau at threonine-181 and neurofilament light biomarkers, and an MRI-score could effectively identify β-amyloid+ cognitively unimpaired and impaired (area under curve, 0.80-0.90). Yet, when the MRI-score is considered in combination with clinical information, plasma phosphorylated-tau at threonine-181 and plasma neurofilament light have minimal added value for detecting β-amyloid-positivity. Our systematic comparison of β-amyloid-positivity detection models identified effective combinations of demographics, APOE, global cognition, MRI and plasma biomarkers. Promising minimally invasive and low-cost predictors such as plasma biomarkers of β-amyloid42/β-amyloid40 may be improved by age and APOE genotype.

Aβ-Induced Damage Memory in hCMEC/D3 Cells Mediated by Sirtuin-1

It is well accepted by the scientific community that the accumulation of beta-amyloid (Aβ) may be involved in endothelial dysfunction during Alzheimer’s disease (AD) progression; however, anti-Aβ anti-bodies, which remove Aβ plaques, do not improve cerebrovascular function in AD animal models. The reasons for these paradoxical results require investigation. We hypothesized that Aβ exposure may cause persistent damage to cerebral endothelial cells even after Aβ is removed (referred to as cerebrovascular endothelial damage memory). In this study, we aimed to investigate whether cerebrovascular endothelial damage memory exists in endothelial cells. hCMEC/D3 cells were treated with Aβ_1–42 for 12 h and then Aβ_1–42 was withdrawn for another 12 h incubation to investigate whether cerebrovascular endothelial damage memory exists in endothelial cells. A mechanism-based kinetics progression model was developed to investigate the dynamic characters of the cerebrovascular endothelial damage. After Aβ_1–42 was removed, the sirt-1 levels returned to normal but the cell vitality did not improve, which suggests that cerebrovascular endothelial damage memory may exist in endothelial cells. Sirt-1 activator SRT2104 and NAD⁺ (Nicotinamide Adenine Dinucleotide) supplement may dose-dependently relieve the cerebrovascular endothelial damage memory. sirt-1 inhibitor EX527 may exacerbate the cerebrovascular endothelial damage memory. Kinetics analysis suggested that sirt-1 is involved in initiating the cerebrovascular endothelial damage memory; otherwise, NAD⁺ exhaustion plays a vital role in maintaining the cerebrovascular endothelial damage memory. This study provides a novel feature of cerebrovascular endothelial damage induced by Aβ.

Modeling mtDNA hypermethylation vicious circle mediating Aβ-induced endothelial damage memory in HCMEC/D3 cell

It is well accepted that accumulation of beta-amyloid (Aβ) may involve in endothelial dysfunction during the Alzheimer's disease (AD) progression. However, cerebrovascular function cannot be improved by removing Aβ in AD animal models. The reasons for these paradoxical results still remain to be further investigated. We hypothesize that Aβ exposure may cause persistence damage to cerebral endothelial cell even after Aβ is removed (termed as cerebrovascular endothelial damage memory) mitochondria DNA (mtDNA) hypermethylation is assumed to be involved in this process. The aim of this study is to investigate whether Aβ exposure induces cerebrovascular endothelial damage memory in endothelial cells and mtDNA hypermethylation involves in this process. The hCMEC/D3 cell is treated with Aβ_1-42 for 12h and then withdraw Aβ_1-42 for another 12h incubation to investigate whether cerebrovascular endothelial damage memory exists in endothelial cells. The levels of mtDNA methylation and cell vitality were not improved by removing Aβ_1-42 after 12h Aβ_1-42 incubation which suggested that the cerebrovascular endothelial damage memory may exist in endothelial cells. Kinetics model analysis suggested that mtDNA hypermethylation involves in initiating the cerebrovascular endothelial damage memory otherwise α-oxoglutarate (AKG) exhaustion plays a vital role in maintaining this process. DNA methylation inhibitor decitabine and AKG supplement may relieve the cerebrovascular endothelial damage memory dose dependently. This study provides a novel feature of cerebrovascular endothelial damage induced by Aβ.