Overview of the blood biomarkers in Alzheimer's disease: Promises and challenges

2024 VCP International Conference: Exploring multi-disciplinary approaches from basic science of valosin containing protein, an AAA+ ATPase protein, to the therapeutic advancement for VCP-associated multisystem proteinopathy

Valosin-containing protein (VCP/p97) is a ubiquitously expressed AAA+ ATPase associated with numerous protein-protein interactions and critical cellular functions including protein degradation and clearance, mitochondrial homeostasis, DNA repair and replication, cell cycle regulation, endoplasmic reticulum-associated degradation, and lysosomal functions including autophagy and apoptosis. Autosomal-dominant missense mutations in the VCP gene may result in VCP-associated multisystem proteinopathy (VCP-MSP), a rare degenerative disorder linked to heterogeneous phenotypes including inclusion body myopathy (IBM) with Paget's disease of bone (PDB) and frontotemporal dementia (FTD) or IBMPFD, amyotrophic lateral sclerosis (ALS), Alzheimer's disease (AD), parkinsonism, Charcot-Marie Tooth disease (CMT), and spastic paraplegia. The complexity of VCP-MSP makes collaboration among stakeholders essential and necessitates a multi-disciplinary approach. The 2024 VCP International Conference was hosted at Caltech between February 22 and 25. Co-organized by Cure VCP Disease and Dr. Tsui-Fen Chou, the meeting aimed to center the patient as a research partner, harmonize diverse stakeholder engagement, and bridge the gap between basic and clinical neuroscience as it relates to VCP-MSP. Over 100 multi-disciplinary experts attended, ranging from basic scientists to clinicians to patient advocates. Attendees discussed genetics and clinical presentation, cellular and molecular mechanisms underlying disease, therapeutic approaches, and strategies for future VCP research. The conference included three roundtable discussions, 29 scientific presentations, 32 scientific posters, nine patient and caregiver posters, and a closing discussion forum. The following conference proceedings summarize these sessions, highlighting both the identified gaps in knowledge and the significant strides made towards understanding and treating VCP diseases.

From Clinic to Mechanisms: Multi-Omics Provide New Insights into Cerebrospinal Fluid Metabolites and the Spectrum of Psychiatric Disorders

Cerebrospinal fluid (CSF) is crucial in maintaining brain homeostasis by facilitating waste clearance, nutrient transport, and immune signaling. However, the links between CSF metabolites and psychiatric disorders, as well as the underlying mechanisms, remain largely unexamined. We conducted a bidirectional two-sample Mendelian randomization analysis to investigate potential causal relationships between CSF metabolites and 12 psychiatric disorders. Summary data for psychiatric disorders were sourced from the Psychiatric Genomics Consortium, while information on CSF metabolites was derived from two studies within the Wisconsin Alzheimer's Disease cohort. Causal estimates and pleiotropy were assessed using several robust methods, including inverse-variance-weighted (IVW) analysis, weighted median analysis, MR-Egger regression, and the MR-Egger test. Furthermore, a transcriptome-wide association study was conducted to explore potential mechanisms and shared etiologies between CSF metabolites and psychiatric disorders. The genetic risk of eating disorders (ED) can be increased by leucine (OR = 1.55, 95% CI: 1.21-1.97, P = 4.35 × 10⁻4), salicylate (OR = 1.03, 95% CI: 1.01-1.04, P = 4.95 × 10⁻4), and 1-methylnicotinamide (OR = 1.06, 95% CI: 1.03-1.09, P = 6.94 × 10⁻6), while methylmalonate may reduce ED risk (OR = 0.95, 95% CI: 0.93-0.98, P = 1.31 × 10⁻4). Similarly, the risk of schizophrenia (SCZ) may be reduced by threonate (OR = 0.93, 95% CI: 0.89-0.97, P = 1.98 × 10⁻4), oxalate (OR = 0.94, 95% CI: 0.90-0.97, P = 3.15 × 10⁻4), phenyllactate (OR = 0.96, 95% CI: 0.94-0.98, P = 2.23 × 10⁻4), N-acetylglucosamine (OR = 0.98, 95% CI: 0.97-0.99, P = 3.57 × 10⁻5), and citramalate (OR = 0.98, 95% CI: 0.98-0.99, P = 5.78 × 10⁻4). Conversely, SCZ may upregulate gamma-glutamylleucine (β = 0.08, P = 1.97 × 10⁻4) and O-sulfo-L-tyrosine (β = 0.06, P = 1.25 × 10⁻4), while downregulating gamma-glutamylphenylalanine (β = - 0.50, P = 1.16 × 10⁻4). Signal pathways related to the mechanistic target of the rapamycin (mTOR), post-translational protein modifications, and immune regulation may mediate the causal relationship of CSF metabolites on ED and SCZ. We identified a casual genetic causal relationship between CSF metabolites and both ED and schizophrenia SCZ, which is potentially mediated by pathways related to energy metabolism, post-translational modifications, and immune regulation.

Active Immunotherapy for the Prevention of Alzheimer's and Parkinson's Disease

Neurodegenerative diseases (ND) give rise to significant declines in motor, autonomic, behavioral, and cognitive functions. Of these conditions, Alzheimer's disease (AD) and Parkinson's disease (PD) are the most prevalent, impacting over 55 million people worldwide. Given the staggering financial toll on the global economy and their widespread manifestation, NDs represent a critical issue for healthcare systems worldwide. Current treatment options merely seek to provide symptomatic relief or slow the rate of functional decline and remain financially inaccessible to many patients. Indeed, no therapy has yet demonstrated the potential to halt the trajectory of NDs, let alone reverse them. It is now recognized that brain accumulation of pathological variants of AD- or PD-associated proteins (i.e., amyloid-β, Tau, α-synuclein) begins years to decades before the onset of clinical symptoms. Accordingly, there is an urgent need to pursue therapies that prevent the neurodegenerative processes associated with pathological protein aggregation long before a clinical diagnosis can be made. These therapies must be safe, convenient, and affordable to ensure broad coverage in at-risk populations. Based on the need to intervene long before clinical symptoms appear, in this review, we present a rationale for greater investment to support the development of active immunotherapy for the prevention of the two most common NDs based on their safety profile, ability to specifically target pathological proteins, as well as the significantly lower costs associated with manufacturing and distribution, which stands to expand accessibility to millions of people globally.

Nucleic Acids-Based Biomarkers for Alzheimer's Disease Diagnosis and Novel Molecules to Treat the Disease

Alzheimer's disease (AD) represents the most common form of dementia and affects million people worldwide, with a high social burden and considerable economic costs. AD diagnosis benefits from a well-established panel of laboratory tests that allow ruling-in patients, along with FDG and amyloid PET imaging tools. The main laboratory tests used to identify AD patients are Aβ40, Aβ42, the Aβ42/Aβ40 ratio, phosphorylated Tau 181 (pTau181) and total Tau (tTau). Although they are measured preferentially in the cerebrospinal fluid (CSF), some evidence about the possibility for blood-based determination to enter clinical practice is growing up. Unfortunately, CSF biomarkers for AD and, even more, the blood-based ones, present a few flaws, and twenty years of research in this field did not overcome these pitfalls. The tale even worsens when the issue of treating AD is addressed due to the lack of effective strategies despite the many decades of attempts by pharmaceutic industries and scientists. Amyloid-based drugs failed to stop the disease, and no neuroinflammation-based drugs have been demonstrated to work so far. Hence, only symptomatic therapy is available, with no disease-modifying treatment on hand. Such a desolate situation fully justifies the active search for novel biomarkers to be used as reliable tests for AD diagnosis and molecular targets for treating patients. Recently, a novel group of molecules has been identified to be used for AD diagnosis and follow-up, the nuclei acid-based biomarkers. Nucleic acid-based biomarkers are a composite group of extracellular molecules consisting of DNA and RNA alone or in combination with other molecules, including proteins. This review article reports the main findings from the studies carried out on these biomarkers during AD, and highlights their advantages and limitations.

The Inflammasome Adaptor Protein ASC in Plasma as a Biomarker of Early Cognitive Changes

Dementia is a group of symptoms including memory loss, language difficulties, and other types of cognitive and functional impairments that affects 57 million people worldwide, with the incidence expected to double by 2040. Therefore, there is an unmet need to develop reliable biomarkers to diagnose early brain impairments so that emerging interventions can be applied before brain degeneration. Here, we performed biomarker analyses for apoptosis-associated speck-like protein containing a caspase recruitment domain (ASC), neurofilament light chain (NfL), glial fibrillary acidic protein (GFAP), and amyloid-β 42/40 (Aβ42/40) ratio in the plasma of older adults. Participants had blood drawn at baseline and underwent two annual clinical and cognitive evaluations. The groups tested either cognitively normal on both evaluations (NN), cognitively normal year 1 but cognitively impaired year 2 (NI), or cognitively impaired on both evaluations (II). ASC was elevated in the plasma of the NI group compared to the NN and II groups. Additionally, Aβ42 was increased in the plasma in the NI and II groups compared to the NN group. Importantly, the area under the curve (AUC) for ASC in participants older than 70 years old in NN vs. NI groups was 0.81, indicating that ASC is a promising plasma biomarker for early detection of cognitive decline.

SIMOA Diagnostics on Alzheimer's Disease and Frontotemporal Dementia

BACKGROUND

Accurate diagnosis of Alzheimer's disease (AD) and frontotemporal dementia (FTD) represents a health issue due to the absence of disease traits. We assessed the performance of a SIMOA panel in cerebrospinal fluid (CSF) from 43 AD and 33 FTD patients with 60 matching Control subjects in combination with demographic-clinical characteristics.

METHODS

136 subjects (AD: n = 43, FTD: n = 33, Controls: n = 60) participated. Single-molecule array (SIMOA), glial fibrillary acidic protein (GFAP), neurofilament light (NfL), TAU, and ubiquitin carboxy-terminal hydrolase L1 (UCH-L1) in CSF were analyzed with a multiplex neuro 4plex kit. Receiver operating characteristic (ROC) curve analysis compared area under the curve (AUC), while the principal of the sparse partial least squares discriminant analysis (sPLS-DA) was used with the intent to strengthen the identification of confident disease clusters.

RESULTS

CSF exhibited increased levels of all SIMOA biomarkers in AD compared to Controls (AUCs: 0.71, 0.86, 0.92, and 0.94, respectively). Similar patterns were observed in FTD with NfL, TAU, and UCH-L1 (AUCs: 0.85, 0.72, and 0.91). sPLS-DA revealed two components explaining 19% and 9% of dataset variation.

CONCLUSIONS

CSF data provide high diagnostic accuracy among AD, FTD, and Control discrimination. Subgroups of demographic-clinical characteristics and biomarker concentration highlighted the potential of combining different kinds of data for successful and more efficient cohort clustering.

Circulating Biomarkers for Alzheimer's Disease: Unlocking the Diagnostic Potential in Low- and Middle-Income Countries, Focusing on Africa

BACKGROUND

Alzheimer's disease (AD) is emerging as a significant public health challenge in Africa, with predictions indicating a tripling in incidence by 2050. The diagnosis of AD on the African continent is notably difficult, leading to late detection that severely limits treatment options and significantly impacts the quality of life for patients and their families.

SUMMARY

This review focuses on the potential of high-sensitivity specific blood biomarkers as promising tools for improving AD diagnosis and management globally, particularly in Africa. These advances are particularly pertinent in the continent, where access to medical and technical resources is often limited.

KEY MESSAGES

Identifying precise, sensitive, and specific blood biomarkers could contribute to the biological characterization and management of AD in Africa. Such advances promise to improve patient care and pave the way for new regional opportunities in pharmaceutical research and drug trials on the continent for AD.

Gene expression patterns of CRYM and SIGLEC10 in Alzheimer's disease: potential early diagnostic indicators

BACKGROUND

Alzheimer's disease (AD) is a neurological condition that may lead to dementia as well as a slow and steady decline in cognitive ability. Finding early signs that may be used in the diagnosis of AD is still a difficult aim to achieve in the field of medical practice.

METHODS AND RESULTS

The purpose of this research was to investigate to determine any differences in the gene expression patterns of crystallin mu (CRYM) and sialic acid-binding immunoglobulin-like lectin 10 (SIGLEC10) in whole blood samples obtained from fifty individuals who were diagnosed with AD and fifty individuals as a control group. When compared with controls, it was discovered that the expression of the CRYM gene was substantially decreased in AD patients, but the expression of the SIGLEC10 gene was significantly higher. A positive correlation between CRYM and SIGLEC10 was noticed solely in patients with AD. Furthermore, assessing the diagnostic value of these genes, CRYM and SIGLEC10 transcript levels displayed an area under the curve (AUC) of 0.74 and 0.81, respectively.

CONCLUSIONS

These results suggest that alterations in CRYM and SIGLEC10 expression may be implicated in AD pathology and that these genes expression levels can potentially serve as biomarkers for early detection and diagnosis of AD. Nevertheless, further validation of these findings requires the inclusion of more extensive and heterogeneous cohorts. The findings derived from this study possess the capability to offer a significant contribution towards the progression of innovative diagnostic and therapeutic strategies for AD.

Considerations for Use of Blood-Based Biomarkers in Epidemiologic Dementia Research

Dementia represents a growing public health burden with large social, racial, and ethnic disparities. The etiology of dementia is poorly understood, and the lack of robust biomarkers in diverse, population-representative samples is a barrier to moving dementia research forward. Existing biomarkers and other measures of pathology-derived from neuropathology, neuroimaging, and cerebrospinal fluid samples-are commonly collected from predominantly White and highly educated samples drawn from academic medical centers in urban settings. Blood-based biomarkers are noninvasive and less expensive, offering promise to expand our understanding of the pathophysiology of dementia, including in participants from historically excluded groups. Although largely not yet approved by the Food and Drug Administration or used in clinical settings, blood-based biomarkers are increasingly included in epidemiologic studies on dementia. Blood-based biomarkers in epidemiologic research may allow the field to more accurately understand the multifactorial etiology and sequence of events that characterize dementia-related pathophysiological changes. As blood-based dementia biomarkers continue to be developed and incorporated into research and practice, we outline considerations for using them in dementia epidemiology, and illustrate key concepts with Alzheimer's Disease Neuroimaging Initiative (2003-present) data. We focus on measurement, including both validity and reliability, and on the use of dementia blood-based biomarkers to promote equity in dementia research and cognitive aging. This article is part of a Special Collection on Mental Health.

Biological Diagnosis of Alzheimer's Disease Based on Amyloid Status: An Illustration of Confirmation Bias in Medical Research?

Alzheimer's disease (AD) was first characterized by Dr. Alois Alzheimer in 1906 by studying a demented patient and discovering cerebral amyloid plaques and neurofibrillary tangles. Subsequent research highlighted the roles of Aβ peptides and tau proteins, which are the primary constituents of these lesions, which led to the amyloid cascade hypothesis. Technological advances, such as PET scans using Florbetapir, have made it possible to visualize amyloid plaques in living patients, thus improving AD's risk assessment. The National Institute on Aging and the Alzheimer's Association introduced biological diagnostic criteria in 2011, which underlined the amyloid deposits diagnostic value. However, potential confirmation bias may have led researchers to over-rely on amyloid markers independent of AD's symptoms, despite evidence of their limited specificity. This review provides a critical examination of the current research paradigm in AD, including, in particular, the predominant focus on amyloid and tau species in diagnostics. We discuss the potential multifaceted consequences of this approach and propose strategies to mitigate its overemphasis in the development of new biomarkers. Furthermore, our study presents comprehensive guidelines aimed at enhancing the creation of biomarkers for accurately predicting AD dementia onset. These innovations are crucial for refining patient selection processes in clinical trial enrollment and for the optimization of therapeutic strategies. Overcoming confirmation bias is essential to advance the diagnosis and treatment of AD and to move towards precision medicine by incorporating a more nuanced understanding of amyloid biomarkers.

Biomarkers associated with the pathogenesis of Alzheimer's disease

Alzheimer's disease (AD) is a progressive degenerative neurological illness with insidious onset. Due to the complexity of the pathogenesis of AD and different pathological changes, the clinical phenotypes of dementia are diverse, and these pathological changes also interact with each other. Therefore, it is of great significance to search for biomarkers that can diagnose these pathological changes to improve the ability to monitor the course of disease and treat the disease. The pathological mechanism hypothesis with high recognition of AD mainly includes the accumulation of β-amyloid (Aβ) around neurons and hyperphosphorylation of tau protein, which results in the development of neuronal fiber tangles (NFTs) and mitochondrial dysfunction. AD is an irreversible disease; currently, there is no clinical cure or delay in the disease process of drugs, and there is a lack of effective early clinical diagnosis methods. AD patients, often in the dementia stages and moderate cognitive impairment, will seek medical treatment. Biomarkers can help diagnose the presence or absence of specific diseases and their pathological processes, so early screening and diagnosis are crucial for the prevention and therapy of AD in clinical practice. β-amyloid deposition (A), tau pathology (T), and neurodegeneration/neuronal damage (N), also known as the AT (N) biomarkers system, are widely validated core humoral markers for the diagnosis of AD. In this paper, the pathogenesis of AD related to AT (N) and the current research status of cerebrospinal fluid (CSF) and blood related biomarkers were reviewed. At the same time, the limitations of humoral markers in the diagnosis of AD were also discussed, and the future development of humoral markers for AD was prospected. In addition, the contents related to mitochondrial dysfunction, prion virology and intestinal microbiome related to AD are also described, so as to understand the pathogenesis of AD in many aspects and dimensions, so as to evaluate the pathological changes related to AD more comprehensively and accurately.

Poor Oral Health Linked with Higher Risk of Alzheimer's Disease

Alzheimer's disease (AD) is a multifactorial neurodegenerative disease characterized by cognitive and behavioral changes in older adults. Emerging evidence suggests poor oral health is associated with AD, but there is a lack of large-scale clinical studies demonstrating this link. Herein, we used the TriNetX database to generate clinical cohorts and assess the risk of AD and survival among >30 million de-identified subjects with normal oral health (n = 31,418,814) and poor oral health (n = 1,232,751). There was a greater than two-fold increase in AD risk in the poor oral health cohort compared to the normal oral health group (risk ratio (RR): 2.363, (95% confidence interval: 2.326, 2.401)). To reduce potential bias, we performed retrospective propensity score matching for age, gender, and multiple laboratory measures. After matching, the cohorts had no significant differences in survival probability. Furthermore, when comparing multiple oral conditions, diseases related to tooth loss were the most significant risk factor for AD (RR: 3.186, (95% CI: 3.007, 3.376)). Our results suggest that oral health may be important in AD risk, regardless of age, gender, or laboratory measures. However, more large-scale cohort studies are necessary to validate these findings and further evaluate links between oral health and AD.

Head-to-Head Comparison of Two Plasma Phospho-tau Assays in Predicting Conversion of Mild Cognitive Impairment to Dementia

BACKGROUND

Among blood biomarkers, phospho-tau181 (pTau181) is one of the most efficient in detecting Alzheimer disease across its continuum. However, transition from research to routine clinical use will require confirmation of clinical performance in prospective cohorts and evaluation of cofounding factors.

METHODS

Here we tested the Lumipulse assay for plasma pTau181 in mild cognitive impairment (MCI) participants from the Baltazar prospective cohort. We compared the performance of this assay to the corresponding Simoa assay for the prediction of conversion to dementia. We also evaluated the association with various routine blood parameters indicative of comorbidities.

RESULTS

Lumipulse and Simoa gave similar results overall, with hazard ratios for conversion to dementia of 3.48 (95% CI, 2.23-5.45) and 3.70 (95%CI, 2.39-5.87), respectively. However, the 2 tests differ somewhat in terms of the patients identified, suggesting that their use may be complementary. When combined with age, sex, and apolipoprotein E (APOE)ε4 status, areas under the curves for conversion detection were 0.736 (95% CI, 0.682-0.791) for Lumipulse and 0.733 (95% CI, 0.679-0.788) for Simoa. Plasma pTau181 was independently associated with renal dysfunction (assessed by creatinine and glomerular filtration) for both assays. Cardiovascular factors (adiponectin and cholesterol), nutritional, and inflammatory markers (total protein content, C-reactive protein) also impacted plasma pTau181 concentration, although more so with the Simoa than with the Lumipulse assay.

CONCLUSIONS

Plasma pTau181 measured using the fully automated Lumipulse assay performs as well as the Simoa assay for detecting conversion to dementia of MCI patients within 3 years and Lumipulse is less affected by comorbidities. This study suggests a pathway to routine noninvasive in vitro diagnosis-approved testing to contribute to the management of Alzheimer disease.

CLINICALTRIALS.GOV REGISTRATION NUMBER

NCT01315639.

Pomegranate: A Source of Multifunctional Bioactive Compounds Potentially Beneficial in Alzheimer's Disease

Pomegranate fruit (PF) is a fruit rich in nutraceuticals. Nonedible parts of the fruit, especially peels, contain high amounts of bioactive components that have been largely used in traditional medicine, such as the Chinese, Unani, and Ayurvedic ones, for treating several diseases. Polyphenols such as anthocyanins, tannins, flavonoids, phenolic acids, and lignans are the major bioactive molecules present in PF. Therefore, PF is considered a source of natural multifunctional agents that exert simultaneously antioxidant, anti-inflammatory, antitumor, antidiabetic, cardiovascular, and neuroprotective activities. Recently, several studies have reported that the nutraceuticals contained in PF (seed, peel, and juice) have a potential beneficial role in Alzheimer's disease (AD). Research suggests that the neuroprotective effect of PF is mostly due to its potent antioxidant and anti-inflammatory activities which contribute to attenuate the neuroinflammation associated with AD. Despite the numerous works conducted on PF, to date the mechanism by which PF acts in combatting AD is not completely known. Here, we summarize all the recent findings (in vitro and in vivo studies) related to the positive effects that PF and its bioactive components can have in the neurodegeneration processes occurring during AD. Moreover, considering the high biotransformation characteristics of the nutraceuticals present in PF, we propose to consider the chemical structure of its active metabolites as a source of inspiration to design new molecules with the same beneficial effects but less prone to be affected by the metabolic degradation process.

Electrochemical Immunosensors Developed for Amyloid-Beta and Tau Proteins, Leading Biomarkers of Alzheimer's Disease

Alzheimer's disease (AD) is the most common neurological disease and a serious cause of dementia, which constitutes a threat to human health. The clinical evidence has found that extracellular amyloid-beta peptides (Aβ), phosphorylated tau (p-tau), and intracellular tau proteins, which are derived from the amyloid precursor protein (APP), are the leading biomarkers for accurate and early diagnosis of AD due to their central role in disease pathology, their correlation with disease progression, their diagnostic value, and their implications for therapeutic interventions. Their detection and monitoring contribute significantly to understanding AD and advancing clinical care. Available diagnostic techniques, including magnetic resonance imaging (MRI) and positron emission tomography (PET), are mainly used to validate AD diagnosis. However, these methods are expensive, yield results that are difficult to interpret, and have common side effects such as headaches, nausea, and vomiting. Therefore, researchers have focused on developing cost-effective, portable, and point-of-care alternative diagnostic devices to detect specific biomarkers in cerebrospinal fluid (CSF) and other biofluids. In this review, we summarized the recent progress in developing electrochemical immunosensors for detecting AD biomarkers (Aβ and p-tau protein) and their subtypes (AβO, Aβ_(1-40), Aβ_(1-42), t-tau, cleaved-tau (c-tau), p-tau₁₈₁, p-tau₂₃₁, p-tau₃₈₁, and p-tau₄₄₁). We also evaluated the key characteristics and electrochemical performance of developed immunosensing platforms, including signal interfaces, nanomaterials or other signal amplifiers, biofunctionalization methods, and even primary electrochemical sensing performances (i.e., sensitivity, linear detection range, the limit of detection (LOD), and clinical application).

Inflammatory Processes in Alzheimer's Disease-Pathomechanism, Diagnosis and Treatment: A Review

Alzheimer's disease is one of the most commonly diagnosed cases of senile dementia in the world. It is an incurable process, most often leading to death. This disease is multifactorial, and one factor of this is inflammation. Numerous mediators secreted by inflammatory cells can cause neuronal degeneration. Neuritis may coexist with other mechanisms of Alzheimer's disease, contributing to disease progression, and may also directly underlie AD. Although much has been established about the inflammatory processes in the pathogenesis of AD, many aspects remain unexplained. The work is devoted in particular to the pathomechanism of inflammation and its role in diagnosis and treatment. An in-depth and detailed understanding of the pathomechanism of neuroinflammation in Alzheimer's disease may help in the development of diagnostic methods for early diagnosis and may contribute to the development of new therapeutic strategies for the disease.