Apolipoprotein E and Alzheimer's disease

Dual single nucleotide polymorphisms typing of apolipoprotein E gene based on double restriction endonuclease with lambda exonuclease and triple helix molecular switch assistance

Single nucleotide polymorphisms (SNPs) are critical determinants of disease susceptibility, pathogenesis, and drug response, underscoring the need for their accurate monitoring in clinical practice. In this study, we propose a novel apolipoprotein E (APOE) genotyping method for the rapid and precise identification of six genotypes (ε2/ε2, ε3/ε3, ε4/ε4, ε2/ε3, ε2/ε4, and ε3/ε4). The method utilizes restriction endonucleases AflIII and HaeII to selectively cleave the rs429358 and rs7412 sites, thereby generating distinct double-stranded DNA fragments. These fragments are subsequently processed by Lambda exonuclease to produce single-stranded DNA, which binds to a triple-helix molecular switch (THMS) and induces its conformational transition into a hairpin structure, resulting in a fluorescence change. The optimized assay exhibits a linear detection range of 5-1000 copies with a minimum detection limit of 2 copies for the rs429358 site, and a range of 10-1000 copies with a minimum detection limit of 6 copies for the rs7412 site. Furthermore, the method was validated using clinical samples from 10 Alzheimer's disease patients, achieving complete concordance with sequencing results, which underlines the high specificity and sensitivity of the method and demonstrates its potential as a valuable tool for the early diagnosis and personalized treatment of Alzheimer's disease.

Infections, genetics, and Alzheimer's disease: Exploring the pathogenic factors for innovative therapies

Alzheimer's disease (AD) is a progressive neurodegenerative condition that creates a significant global health challenge and profoundly affects patients and their families. Recent research has highlighted the critical role of microorganisms, particularly viral infections, in the pathogenesis of AD. The involvement of viral infections in AD pathogenesis is predominantly attributed to their ability to induce neuroinflammation and amyloid beta (Aβ) deposition in the brain. The extant research exploring the relationship between viruses and AD has focused largely on Herpesviridae family. Traces of Herpesviruses, such as Herpes Simplex Virus-1 and Epstein Barr Virus, have been found in the brains of patients with AD. These viruses are thought to contribute to the disease progression by triggering chronic inflammatory responses in the brain. They can remain dormant in the brain, and become reactivated due to stress, a secondary viral infection, or immune-senescence in older adults. This review focuses on the association between Herpesviridae and bacterial infections with AD. We explore the genetic factors that might regulate viral illness and discuss clinical trials investigating antiviral and anti-inflammatory agents as possible therapeutic strategies to mitigate cognitive decline in patients with AD. In summary, understanding the interplay between infections, genetic factors, and AD pathogenesis may pave the way for novel therapeutic approaches, facilitating better management and possibly even prevent this debilitating disease.

Multisystem failure, tipping points, and risk of Alzheimer's disease

INTRODUCTION

Medical conditions including obesity, diabetes, hyperlipidemia, and depression significantly increased risk of Alzheimer's disease (AD). However, effect of their duration, influenced by non-modifiable factors like chromosomal sex and apolipoprotein E (APOE) genotype, remains unclear.

METHODS

Data from 5644 UKBiobank participants were analyzed using Cox regression model to identify critical tipping points based on age of onset, risk factor (RF) duration and their interaction with sex and APOE genotype.

RESULTS

Hypertension or diabetes before age 62 exerted greater AD risk than APOEε4 alone. Obesity before age 62 increased AD risk by 54%, with the risk nearly tripling between ages 62-72. Hyperlipidemia and depression were associated with age-independent risk increases of 33% and 69%, respectively. After age 72, APOEε4 became the dominant RF.

DISCUSSION

Duration of AD-risk-factors can have a greater impact than APOEε4. Identification of critical age-related tipping points highlights temporal dynamics of AD progression and role of multisystem failure in AD progression.

HIGHLIGHTS

AD risk factors impact AD onset, especially diagnosed between ages 62 and 72. Later diagnoses of hypertension, diabetes, and obesity delayed AD onset. Hyperlipidemia and depression increased AD risk by 33% and 69%, age-independent. APOEε4 carriers regardless of sex exhibited a higher risk increasing with age. Trajectories differed between APOEε4 carriers and non-carriers across sex.

Apolipoprotein E in Alzheimer's disease: molecular insights and therapeutic opportunities

Apolipoprotein E (APOE- gene; apoE- protein) is the strongest genetic modulator of late-onset Alzheimer's disease (AD), with its three major isoforms conferring risk for disease ε2 < ε3 < ε4. Emerging protective gene variants, such as APOE Christchurch and the COLBOS variant of REELIN, an alternative target of certain apoE receptors, offer novel insights into resilience against AD. In recent years, the role of apoE has been shown to extend beyond its primary function in lipid transport, influencing multiple biological processes, including amyloid-β (Aβ) aggregation, tau pathology, neuroinflammation, autophagy, cerebrovascular integrity and protection from lipid peroxidation and the resulting ferroptotic cell death. While the detrimental influence of apoE ε4 on these and other processes has been well described, the molecular mechanisms underpinning this disadvantage require further enunciation, particularly to realize therapeutic opportunities related to apoE. This review explores the multifaceted roles of apoE in AD pathogenesis, emphasizing recent discoveries and translational approaches to target apoE-mediated pathways. These findings underscore the potential for apoE-based therapeutic strategies to prevent or mitigate AD in genetically at-risk populations.

P-glycoprotein and Alzheimer's Disease: Threats and Opportunities

Alzheimer's disease (AD) is a progressive neurodegenerative disorder that affects more than 50 million people worldwide. One of the hallmark features of AD is the accumulation of amyloid β-peptide (Aβ) protein in the brain. P-glycoprotein (P-gp) is a membrane-bound protein expressed in various tissues, including the cerebrovascular endothelium. It plays a crucial role in the efflux of toxic substances, including Aβ, from the brain. Aberrations in P-gp levels or activity have been implicated in the pathogenesis of AD by promoting the accumulation of Aβ in the brain. Therefore, modulating the P-gp function represents a promising therapeutic strategy for treating AD. P-gp has multiple substrate binding sites, creating the potential for substrates to fall into complementation groups based on these sites; two substrates in the same complementation group may compete with one other, but two substrates in different groups may exhibit cooperativity. Thus, a given P-gp substrate may interfere with Aβ efflux whereas another may promote clearance. These threats and opportunities, as well as other aspects of P-gp relevance to AD, are discussed here.

Involvement of the weak metabolic function in cardiovascular toxicity induced by idebenone in zebrafish

Idebenone (IDE) is a commonly used psychotropic drug in the clinic. However, the cardiovascular toxicity of IDE has not been reported previously. Therefore, we evaluated the safety of IDE and preliminarily elucidated the mechanism of cardiovascular toxicity induced by IDE using zebrafish as the model organism. In this study, wild-type AB zebrafish, and transgenic zebrafish Tg(cmcl2:EGFP) with green fluorescence-labelled cardiomyocytes were used as the research objects. We evaluated the effects of IDE on the sinus venosus-bulbus arteriosus (SV-BA) distance, ejection fraction, ventricular short-axis shortening rate, blood flow rate, and the staining area and intensity of cardiac erythrocytes. The toxic mechanism of IDE was elucidated using transcriptomics and Quantitative real-time PCR (qRT-PCR). We found that high concentrations of IDE could cause acute poisoning of some zebrafish within a short period (6 h), mainly characterized by severe cardiac venous stasis. IDE decreased the blood flow and reduced the red blood cell stained area in the heart region of some zebrafish. The results of transcriptome analysis and qRT-PCR showed that the expression of genes related to drug metabolism and lipid metabolism was significantly down-regulated in zebrafish with IDE-induced cardiovascular toxicity. We believe that IDE may be more likely to cause acute cardiovascular toxicity in organisms with weak metabolic enzyme function. The present study investigated the mechanism of the toxic effects of IDE using a zebrafish model and laid the foundation for a more comprehensive understanding of the cardiovascular toxicity of IDE.

Modeling biomarker kinetics of Aβ levels in serum following blast

Elucidating the unique neuropathological response to blast exposure remains a barrier towards the development of diagnostic approaches for those with blast-induced traumatic brain injury (bTBI). Quantification of biomarker concentrations in the blood post-injury is typically used to inform brain injury severity. However, injury progression and associated changes in biomarker concentrations are sensitive to parameters such as the blast overpressure (BOP) magnitude and frequency of blast exposure. Through this work, a blast-dose biomarker kinetics (BxK) platform was developed and validated for Aβ42 as a promising predictor of injury post-blast. Blast-dose responses accounting for BOP magnitude and frequency were integrated into a mathematical model accounting for whole-body Aβ peptide kinetics. Validation of the developed model was performed through comparison with acute monomer levels in the blood serum of 15 service members exposed to repeated low-level blast while undergoing three-day weapons training. Amyloid precursor protein (APP) synthesis was assumed to be proportional to blast magnitude and additive effects within a window of recovery were applied to account for cumulative exposure. Aβ42 concentrations in the blood serum were predicted within 6.5 ± 5.2% on average, demonstrating model feasibility and biomarker sensitivity to blast. Outcomes discuss how modulation of patient-specific factors (age, weight, genetic factors, years of exposure, sleep) and pathophysiological factors (BBB permeability, amyloidogenic pathology, neuroinflammation) can reveal potential sources of variability in experimental data and be incorporated into the blast-dose BxK platform in future iterations. Advancements in model complexity accounting for sex-specific factors, weapon system, stress levels, risk of symptom onset, and pharmacological treatment strategies are anticipated to improve model calibration. Utilization of this blast-dose BxK model to identify drivers of pathophysiological mechanisms and predict chronic outcomes has the potential to transform bTBI diagnostic, prognostic, and therapeutic strategies.

Multi-target approach to Alzheimer's disease prevention and treatment: antioxidant, anti-inflammatory, and amyloid- modulating mechanisms

Alzheimer's disease (AD) is characterized by amyloid-β (Aβ) plaque accumulation, neurofibrillary tangles, neuroinflammation, and progressive cognitive decline, posing a significant global health challenge. Growing evidence suggests that dietary polyphenols may reduce the risk and progression of AD through multifaceted neuroprotective mechanisms. Polyphenols regulate amyloid proteostasis by inhibiting β/γ-secretase activity, preventing Aβ aggregation, and enhancing clearance pathways. Their strong antioxidant properties neutralize reactive oxygen species, chelate redox-active metals, and activate cytoprotective enzymes via Nrf2 signaling. This review examines the potential therapeutic targets, signaling pathways, and molecular mechanisms by which dietary polyphenols exert neuroprotective effects in AD, focusing on their roles in modulating amyloid proteostasis, oxidative stress, neuroinflammation, and cerebrovascular health. Polyphenols mitigate neuroinflammation by suppressing NF-κB signaling and upregulating brain-derived neurotrophic factor, supporting neuroplasticity and neurogenesis. They also enhance cerebrovascular health by improving cerebral blood flow, maintaining blood-brain barrier integrity, and modulating angiogenesis. This review examines the molecular and cellular pathways through which polyphenols exert neuroprotective effects, focusing on their antioxidant, anti-inflammatory, and amyloid-modulating roles. We also discuss their influence on key AD pathologies, including Aβ deposition, tau hyperphosphorylation, oxidative stress, and neuroinflammation. Insights from clinical and preclinical studies highlight the potential of polyphenols in preventing or slowing AD progression. Future research should explore personalized dietary strategies that integrate genetic and lifestyle factors to optimize the neuroprotective effects of polyphenols.

Curious Dichotomies of Apolipoprotein E Function in Alzheimer's Disease and Cancer-One Explanatory Mechanism of Inverse Disease Associations?

An apparent "inverse" relationship exists between two seemingly unconnected conditions, Alzheimer's disease (AD) and cancer, despite sharing similar risk factors, like increased age and obesity. AD is associated with amyloid beta (Aβ) plaques and neurofibrillary tau tangles that cause neural degeneration; cancer, in contrast, is characterized by enhanced cell survival and proliferation. Apolipoprotein E (ApoE) is the main lipoprotein found in the central nervous system and via its high affinity with lipoprotein receptors plays a critical role in cholesterol transport and uptake. ApoE has 3 protein isoforms, ApoE E2, ApoE E3, and ApoE E4, respectively encoded for by 3 allelic variants of APOE (ε2, ε3, and ε4). This review examines the characteristics and function of ApoE described in both AD and cancer to assimilate evidence for its potential contribution to mechanisms that may underly the reported inverse association between the two conditions. Of the genetic risk factors relevant to most cases of AD, the most well-known with the strongest contribution to risk is APOE, specifically the ε4 variant, whereas for cancer risk, APOE has not featured as a significant genetic contributor to risk. However, at the protein level in both conditions, ApoE contributes to disease pathology via affecting lipid physiology and transport. In AD, Aβ-dependent and -independent interactions have been suggested, whereas in cancer, ApoE plays a role in immunoregulation. Understanding the mechanism of action of ApoE in these diametrically opposed diseases may enable differential targeting of therapeutics to provide a beneficial outcome for both.

Apolipoprotein E in Alzheimer's Disease: Focus on Synaptic Function and Therapeutic Strategy

Synaptic dysfunction is a critical pathological feature in the early phase of Alzheimer's disease (AD) that precedes typical hallmarks of AD, including beta-amyloid (Aβ) plaques and neurofibrillary tangles. However, the underlying mechanism of synaptic dysfunction remains incompletely defined. Apolipoprotein E (APOE) has been shown to play a key role in the pathogenesis of AD, and the ε4 allele of APOE remains the strongest genetic risk factor for sporadic AD. It is widely recognized that APOE4 accelerates the development of Aβ and tau pathology in AD. Recent studies have indicated that APOE affects synaptic function through a variety of pathways. Here, we summarize the mechanism of modulating synapses by various APOE isoforms and demonstrate the therapeutic potential by targeting APOE4 for AD treatment.

Preventive, ameliorative, and therapeutic effects of steamed mature silkworms on metabolic disorders caused by loss of apolipoprotein E

Metabolic disorders encompass various dysregulations, such as dyslipidemia, hypertension, central obesity, atherogenic hyperlipidemia, and insulin resistance. Dyslipidemia refers to elevated levels of total cholesterol, low-density lipoprotein cholesterol, and triglycerides, along with decreased high-density lipoprotein cholesterol levels in the blood. Dyslipidemia is closely associated with hypertension, which is one of the important risk factors for cardiovascular disease.In this study, an apolipoprotein E-deficient (apoE-/-) mouse model was utilized to investigate whether supplementation with steamed mature silkworm, known as HongJam, might ameliorate and have therapeutic effects on metabolic disorders and behavioral abnormalities observed in apoE-/- mice. The Golden Silk HongJam-supplemented feed-consuming (GSf)-apoE-/- mice showed recovery from the reduced spatial memory, social memory, and postural control ability observed in the normal feed-consuming (Nf)-apoE-/- mice. They also exhibited similar blood pressure to those in the normal feed-consuming C57BL/6J control (Nf-Con) group. Additionally, the significantly reduced activities of glutathione-S-transferase, superoxide dismutase, acetylcholinesterase, and mitochondrial complexes I-IV in the Nf-apoE-/- group were restored in all GSf-apoE-/- groups. Furthermore, the amount of ATP in all GSf-apoE-/- mice was similar to or higher than that in the Nf-Con group.Taken together, GS HongJam supplementation may have preventive, ameliorative, and therapeutic effects on the symptoms of metabolic disorders caused by the loss of ApoE.

Quantifying natural amyloid plaque accumulation in the continuum of Alzheimer's disease using ADNI

Brain amyloid beta neuritic plaque accumulation is associated with an increased risk of progression to Alzheimer's disease (AD) [Pfeil, J., et al. in Neurobiol Aging 106: 119-129, 2021]. Several studies estimate rates of change in amyloid plaque over time in clinically heterogeneous cohorts with different factors impacting amyloid plaque accumulation from ADNI and AIBL [Laccarino, L., et al. in Annals Clin and Trans Neurol 6: 1113 1120, 2019, Vos, S.J., et al. in Brain 138: 1327-1338, 2015, Lim, Y.Y., et al. in Alzheimer's Dementia 9: 538-545, 2013], but there are no reports using non-linear mixed effect model for amyloid plaque progression over time similar to that existing of disease-modifying biomarkers for other diseases [Cook, S.F. and R.R. Bies in Current Pharmacol Rep 2: 221-230, 2016, Gueorguieva, I., et al. in Alzheimer's Dementia 19: 2253-2264, 2023]. This study describes the natural progression of amyloid accumulation with population mean and between-participant variability for baseline and intrinsic progression rates quantified across the AD spectrum. 1340 ADNI participants were followed over a 10-year period with 18F-florbetapir PET scans used for amyloid plaque detection. Non-linear mixed effect with stepwise covariate modelling (scm) was used. Change in natural amyloid plaque levels over 10 year period followed an exponential growth model with an intrinsic rate of approx. 3 centiloid units/year. Age, gender, APOE4 genotype and disease stage were important factors on the baseline in the natural amyloid model. In APOE4 homozygous carriers mean baseline amyloid was increased compared to APOE4 non carriers. These results demonstrate natural progression of amyloid plaque in the continuum of AD.

Resilience mechanisms underlying Alzheimer's disease

Alzheimer's disease (AD) consists of two main pathologies, which are the deposition of amyloid plaque as well as tau protein aggregation. Evidence suggests that not everyone who carries the AD-causing genes displays AD-related symptoms; they might never acquire AD as well. These individuals are referred to as non-demented individuals with AD neuropathology (NDAN). Despite the presence of extensive AD pathology in their brain, it was found that NDAN had better cognitive function than was expected, suggesting that they were more resilient (better at coping) to AD due to differences in their brains compared to other demented or cognitively impaired patients. Thus, identification of the mechanisms underlying resilience is crucial since it represents a promising therapeutic strategy for AD. In this review, we will explore the molecular mechanisms underpinning the role of genetic and molecular resilience factors in improving resilience to AD. These include protective genes and proteins such as APOE2, BDNF, RAB10, actin network proteins, scaffolding proteins, and the basal forebrain cholinergic system. A thorough understanding of these resilience mechanisms is crucial for not just comprehending the development of AD but may also open new treatment possibilities for AD by enhancing the neuroprotective pathway and targeting the pathogenic process.

Quantitative Blood Serum IVDr NMR Spectroscopy in Clinical Metabolomics of Cancer, Neurodegeneration, and Internal Medicine

Despite more than two decades of metabolomics having joined the "omics" scenery, to date only a few novel blood metabolite biomarkers have found their way into the clinic. This is changing now by massive large-scale population metabolic phenotyping for both healthy and disease cohorts. Here, nuclear magnetic resonance (NMR) spectroscopy is a method of choice, as typical blood serum markers can be easily quantified and by knowledge of precise reference concentrations, more and more NMR-amenable biomarkers are established, moving NMR from research to clinical application. Besides customized approaches, to date two major commercial platforms have evolved based on either 600 MHz (14.1 Tesla) or 500 MHz (11.7 Tesla) high-field NMR systems. This chapter provides an introduction into the field of quantitative in vitro diagnostics research (IVDr) NMR at 600 MHz and its application within clinical research of cancer, neurodegeneration, and internal medicine.

Lower neurovascular coupling response despite higher cerebral blood flow at rest in apolipoprotein ɛ4 positive adults

Cerebral blood flow at rest declines with age. However, age-related changes in functional measures of cerebrovascular health including cerebrovascular reactivity and neurovascular coupling are not well understood. Additionally, the effect of apolipoprotein E (APOE) ε4, a strong genetic risk factor for Alzheimer's disease, on cerebral blood flow and cerebrovascular function remains unclear. APOEε4 positive (APOEε4+; n = 37, age = 63±4y) and APOEε4 negative (APOEε4-; n = 50, age = 63±4y) cognitively unimpaired adults participated in this study. Macrovascular cerebral blood flow and microvascular cerebral perfusion were measured using 4D flow MRI and pseudo-continuous arterial spin labeling MRI, respectively. Cerebrovascular reactivity and neurovascular coupling were assessed by measuring middle cerebral artery blood velocity in response to hypercapnia and the n-back test, respectively. Neurovascular coupling was lower in APOEε4+ compared with APOEε4- adults (P<0.05), despite higher cerebral blood flow and cerebrovascular reactivity to hypercapnia. Alterations in neurovascular coupling may occur early, prior to changes in cognition, in aging APOEε4 carriers.

Alzheimer's Disease: Exploring the Landscape of Cognitive Decline

Alzheimer's disease (AD) is a progressive neurodegenerative disorder characterized by cognitive decline, memory loss, and impaired daily functioning. The pathology of AD is marked by the accumulation of amyloid beta plaques and tau protein tangles in the brain, along with neuroinflammation and synaptic dysfunction. Genetic factors, such as mutations in APP, PSEN1, and PSEN2 genes, as well as the APOE ε4 allele, contribute to increased risk of acquiring AD. Currently available treatments provide symptomatic relief but do not halt disease progression. Research efforts are focused on developing disease-modifying therapies that target the underlying pathological mechanisms of AD. Advances in identification and validation of reliable biomarkers for AD hold great promise for enhancing early diagnosis, monitoring disease progression, and assessing treatment response in clinical practice in effort to alleviate the burden of this devastating disease. In this paper, we analyze data from the CAS Content Collection to summarize the research progress in Alzheimer's disease. We examine the publication landscape in effort to provide insights into current knowledge advances and developments. We also review the most discussed and emerging concepts and assess the strategies to combat the disease. We explore the genetic risk factors, pharmacological targets, and comorbid diseases. Finally, we inspect clinical applications of products against AD with their development pipelines and efforts for drug repurposing. The objective of this review is to provide a broad overview of the evolving landscape of current knowledge regarding AD, to outline challenges, and to evaluate growth opportunities to further efforts in combating the disease.

Contrasting association pattern of plasma low-density lipoprotein with white matter integrity in APOE4 carriers versus non-carriers

Apolipoprotein E ε4 (APOE4) is a strong genetic risk factor of Alzheimer's disease and metabolic dysfunction. However, whether APOE4 and markers of metabolic dysfunction synergistically impact the deterioration of white matter (WM) integrity in older adults remains unknown. In the UK Biobank data, we conducted a multivariate analysis to investigate the interactions between APOE4 and 249 plasma metabolites (measured using nuclear magnetic resonance spectroscopy) with whole-brain WM integrity (measured by diffusion-weighted magnetic resonance imaging) in a cohort of 1917 older adults (aged 65.0-81.0 years; 52.4 % female). Although no main association was observed between either APOE4 or metabolites with WM integrity (adjusted P > 0.05), significant interactions between APOE4 and metabolites with WM integrity were identified. Among the examined metabolites, higher concentrations of low-density lipoprotein and very low-density lipoprotein were associated with a lower level of WM integrity (b=-0.12, CI=-0.14,-0.10) among APOE4 carriers. Conversely, among non-carriers, they were associated with a higher level of WM integrity (b=0.05, CI=0.04,0.07), demonstrating a significant moderation role of APOE4 (b =-0.18, CI=-0.20,-0.15, P<0.00001).

Deciphering the role of miRNAs in Alzheimer's disease: Predictive targeting and pathway modulation - A systematic review

Alzheimer's Disease (AD), a multifaceted neurodegenerative disorder, is increasingly understood through the regulatory lens of microRNAs (miRNAs). This review comprehensively examines the pivotal roles of miRNAs in AD pathogenesis, shedding light on their influence across various pathways. We delve into the biogenesis and mechanisms of miRNAs, emphasizing their significant roles in brain function and regulation. The review then navigates the complex landscape of AD pathogenesis, identifying key genetic, environmental, and molecular factors, with a focus on hallmark pathological features like amyloid-beta accumulation and tau protein hyperphosphorylation. Central to our discussion is the intricate involvement of miRNAs in these processes, highlighting their altered expression patterns in AD and subsequent functional implications, from amyloid-beta metabolism to tau pathology, neuroinflammation, oxidative stress, and synaptic dysfunction. The predictive analysis of miRNA targets using computational methods, complemented by experimental validations, forms a crucial part of our discourse, unraveling the contributions of specific miRNAs to AD. Moreover, we explore the therapeutic potential of miRNAs as biomarkers and in miRNA-based interventions, while addressing the challenges in translating these findings into clinical practice. This review aims to enhance understanding of miRNAs in AD, offering a foundation for future research directions and novel therapeutic strategies.

Transient receptor potential channels as an emerging target for the treatment of Alzheimer's disease: Unravelling the potential of pharmacological interventions

Alzheimer's disease (AD) is a devastating disorder with a multifaceted aetiology characterized by dementia, which later progresses to cognitive impairment. Significant efforts have been made to develop pharmacological interventions that slow down the pathogenesis of AD. However, conventional drugs have failed to satisfactorily treat AD and are more focussed towards symptomatic management. Thus, there is a gap in the literature regarding novel targets and modulators targeting them for the effective treatment of AD. Recent studies have demonstrated that modulation of transient receptor potential (TRP) channels has the potential to halt AD pathogenesis at an early stage and rescue hippocampal neurons from death. Amongst several members, TRP channels like TRPA1, TRPC6, TRPM2 and TRPV2 have shown promising results in the attenuation of neurobehavioural cognitive deficits as well as signalling pathways governing such cognitive decline. Furthermore, as these channels govern the ionic balance in the cell, their beneficial effects have also been known to maintain the homeostasis of Ca2+, which is the major culprit eliciting the vicious cycle of excitotoxicity, mitochondrial dysfunction, ROS generation and neurodegeneration. Despite such tremendous potential of TRP channel modulators, their clinical investigation remains elusive. Therefore, in the present review, we have discussed such agents in the light of TRP channels as molecular targets for the amelioration of AD both at the preclinical and clinical levels.

MicroRNAs: pioneering regulators in Alzheimer's disease pathogenesis, diagnosis, and therapy

This article delves into Alzheimer's disease (AD), a prevalent neurodegenerative condition primarily affecting the elderly. It is characterized by progressive memory and cognitive impairments, severely disrupting daily life. Recent research highlights the potential involvement of microRNAs in the pathogenesis of AD. MicroRNAs (MiRNAs), short non-coding RNAs comprising 20-24 nucleotides, significantly influence gene regulation by hindering translation or promoting degradation of target genes. This review explores the role of specific miRNAs in AD progression, focusing on their impact on β-amyloid (Aβ) peptide accumulation, intracellular aggregation of hyperphosphorylated tau proteins, mitochondrial dysfunction, neuroinflammation, oxidative stress, and the expression of the APOE4 gene. Our insights contribute to understanding AD's pathology, offering new avenues for identifying diagnostic markers and developing novel therapeutic targets.

Drugs targeting APOE4 that regulate beta-amyloid aggregation in the brain: Therapeutic potential for Alzheimer's disease

Alzheimer's disease is characterized by progressive cognitive decline, and behavioural and psychological symptoms of dementia are common. The APOE ε4 allele, a genetic risk factor, significantly increases susceptibility to the disease. Despite efforts to effectively treat the disease, only seven drugs are approved for its treatment, and only two of these prevent its progression. This highlights the need to identify new pharmacological options. This review focuses on mimetic peptides, small molecule correctors and HAE-4 antibodies that target ApoE. These drugs reduce β-amyloid-induced neurodegeneration in preclinical models. In addition, loop diuretics such as bumetanide and furosemide show the potential to reduce the prevalence of Alzheimer's disease in humans, and antidepressants such as imipramine improve cognitive function in individuals diagnosed with Alzheimer's disease. Consistent with this, both classes of drugs have been shown to exert neuroprotective effects by inhibiting ApoE4-catalysed Aβ aggregation in preclinical models. Moreover, peroxisome proliferator-activated receptor ligands, particularly pioglitazone and rosiglitazone, reduce ApoE4-induced neurodegeneration in animal models. However, they do not prevent the cognitive decline in APOE ε4 allele carriers. Finally, ApoE4 impairs the integrity of the blood-brain barrier and haemostasis. On this basis, ApoE4 modulation is a promising avenue for the treatment of late-onset Alzheimer's disease.

The reciprocal relationship between amyloid precursor protein and mitochondrial function

Amyloid precursor protein (APP), secretase enzymes, and amyloid beta (Aβ) have been extensively studied in the context of Alzheimer's disease (AD). Despite this, the function of these proteins and their metabolism is not understood. APP, secretase enzymes, and APP processing products (Aβ and C-terminal fragments) localize to endosomes, mitochondria, endoplasmic reticulum (ER), and mitochondrial/ER contact sites. Studies implicate significant relationships between APP, secretase enzyme function, APP metabolism, and mitochondrial function. Mitochondrial dysfunction is a key pathological hallmark of AD and is intricately linked to proteostasis. Here, we review studies examining potential functions of APP, secretase enzymes, and APP metabolites in the context of mitochondrial function and bioenergetics. We discuss implications and limitations of studies and highlight knowledge gaps that remain in the field.

Alzheimer's disease approaches - Focusing on pathology, biomarkers and clinical trial candidates

The strategy for the development of new drugs for Alzheimer's disease (AD) recognizes that an effective therapy requires early therapeutic intervention and a multifactorial approach that considers the individual initiators of AD development. Current knowledge of AD includes the understanding of pathophysiology, risk factors, biomarkers, and the evolving patterns of biomarker abnormalities. This knowledge is essential in identifying potential molecular targets for new drug development. This review summarizes promising AD drug candidates, many of which are currently in phase 2 or 3 clinical trials. New agents are classified according to the Common Alzheimer's Disease Research Ontology (CADRO). The main targets of new drugs for AD are processes related to amyloid beta and tau neurotoxicity, neurotransmission, inflammation, metabolism and bioenergetics, synaptic plasticity, and oxidative stress. These interventions are aimed at preventing disease onset and slowing or eliminating disease progression. The efficacy of pharmacotherapy may be enhanced by combining these drugs with other treatments, antioxidants, and dietary supplements. Ongoing research into AD pathophysiology, risk factors, biomarkers, and the dynamics of biomarker abnormalities may contribute to the understanding of AD and offer hope for effective therapeutic strategies in the near future.

Recent advances in Alzheimer's disease: Mechanisms, clinical trials and new drug development strategies

Alzheimer's disease (AD) stands as the predominant form of dementia, presenting significant and escalating global challenges. Its etiology is intricate and diverse, stemming from a combination of factors such as aging, genetics, and environment. Our current understanding of AD pathologies involves various hypotheses, such as the cholinergic, amyloid, tau protein, inflammatory, oxidative stress, metal ion, glutamate excitotoxicity, microbiota-gut-brain axis, and abnormal autophagy. Nonetheless, unraveling the interplay among these pathological aspects and pinpointing the primary initiators of AD require further elucidation and validation. In the past decades, most clinical drugs have been discontinued due to limited effectiveness or adverse effects. Presently, available drugs primarily offer symptomatic relief and often accompanied by undesirable side effects. However, recent approvals of aducanumab (1) and lecanemab (2) by the Food and Drug Administration (FDA) present the potential in disrease-modifying effects. Nevertheless, the long-term efficacy and safety of these drugs need further validation. Consequently, the quest for safer and more effective AD drugs persists as a formidable and pressing task. This review discusses the current understanding of AD pathogenesis, advances in diagnostic biomarkers, the latest updates of clinical trials, and emerging technologies for AD drug development. We highlight recent progress in the discovery of selective inhibitors, dual-target inhibitors, allosteric modulators, covalent inhibitors, proteolysis-targeting chimeras (PROTACs), and protein-protein interaction (PPI) modulators. Our goal is to provide insights into the prospective development and clinical application of novel AD drugs.

Modulation of cholesterol metabolism with Phytoremedies in Alzheimer's disease: A comprehensive review

Alzheimer's disease (AD) is a complex neurological ailment that causes cognitive decline and memory loss. Cholesterol metabolism dysregulation has emerged as a crucial element in AD pathogenesis, contributing to the formation of amyloid-beta (Aβ) plaques and tau tangles, the disease's hallmark neuropathological characteristics. Thus, targeting cholesterol metabolism has gained attention as a potential therapeutic method for Alzheimer's disease. Phytoremedies, which are generated from plants and herbs, have shown promise as an attainable therapeutic option for Alzheimer's disease. These remedies contain bioactive compounds like phytochemicals, flavonoids, and polyphenols, which have demonstrated potential in modulating cholesterol metabolism and related pathways. This comprehensive review explores the modulation of cholesterol metabolism by phytoremedies in AD. It delves into the role of cholesterol in brain function, highlighting disruptions observed in AD. Additionally, it examines the underlying molecular mechanisms of cholesterol-related pathology in AD. The review emphasizes the significance of phytoremedies as a potential therapeutic intervention for AD. It discusses the drawbacks of current treatments and the need for alternative strategies addressing cholesterol dysregulation and its consequences. Through an in-depth analysis of specific phytoremedies, the review presents compelling evidence of their potential benefits. Molecular mechanisms underlying phytoremedy effects on cholesterol metabolism are examined, including regulation of cholesterol-related pathways, interactions with Aβ pathology, influence on tau pathology, and anti-inflammatory effects. The review also highlights challenges and future perspectives, emphasizing standardization, clinical evidence, and personalized medicine approaches to maximize therapeutic potential in AD treatment. Overall, phytoremedies offer promise as a potential avenue for AD management, but further research and collaboration are necessary to fully explore their efficacy, safety, and mechanisms of action.

Might Diet, APOE-APOA1 Axis, and Iron Metabolism Provide Clues About the Discrepancy in Alzheimer's Disease Occurrence Between Humans and Chimpanzees? A Bioinformatics-Based Re-Analysis of Gene Expression Data on Mice Fed with Human and Chimpanzee Diets

The emergence of conflicting reports on the natural occurrence of Alzheimer's disease (AD) in non-human primates has prompted research on the comparison of the role of diet-associated changes in gene expression between humans and non-human primates. This article analyzes the effects of different human and chimpanzee diets and their link with apolipoproteins, lipid, and iron (Fe) metabolism, starting from available data, to find out any gap in the existing knowledge. By using a system biology approach, we have re-analyzed the liver and brain RNA seq data of mice fed with either human or chimpanzee diet for 2 weeks to look for genetic differences that may explain the differences in AD occurrence between those two classes. In liver samples of mice fed with the chimpanzee diet in comparison to the human diet, apolipoprotein A-1, ceruloplasmin, and 10 other genes were upregulated while 21 genes were downregulated. However, brain apolipoprotein E4 gene expression was not changed upon diet. Genetic, structural, and functional differences in apolipoprotein E protein, along with differences in Fe metabolisms and a longer lifespan of humans during evolution may account for the observed disparity.

The duality of amyloid-β: its role in normal and Alzheimer's disease states

Alzheimer's disease (AD) is a degenerative neurological condition that gradually impairs cognitive abilities, disrupts memory retention, and impedes daily functioning by impacting the cells of the brain. A key characteristic of AD is the accumulation of amyloid-beta (Aβ) plaques, which play pivotal roles in disease progression. These plaques initiate a cascade of events including neuroinflammation, synaptic dysfunction, tau pathology, oxidative stress, impaired protein clearance, mitochondrial dysfunction, and disrupted calcium homeostasis. Aβ accumulation is also closely associated with other hallmark features of AD, underscoring its significance. Aβ is generated through cleavage of the amyloid precursor protein (APP) and plays a dual role depending on its processing pathway. The non-amyloidogenic pathway reduces Aβ production and has neuroprotective and anti-inflammatory effects, whereas the amyloidogenic pathway leads to the production of Aβ peptides, including Aβ40 and Aβ42, which contribute to neurodegeneration and toxic effects in AD. Understanding the multifaceted role of Aβ, particularly in AD, is crucial for developing effective therapeutic strategies that target Aβ metabolism, aggregation, and clearance with the aim of mitigating the detrimental consequences of the disease. This review aims to explore the mechanisms and functions of Aβ under normal and abnormal conditions, particularly in AD, by examining both its beneficial and detrimental effects.

Monoclonal antibodies and aptamers: The future therapeutics for Alzheimer's disease

Alzheimer's disease (AD) is considered the most common and prevalent form of dementia of adult-onset with characteristic progressive impairment in cognition and memory. The cure for AD has not been found yet and the treatments available until recently were only symptomatic. Regardless of multidisciplinary approaches and efforts made by pharmaceutical companies, it was only in the past two years that new drugs were approved for the treatment of the disease. Amyloid beta (Aβ) immunotherapy is at the core of this therapy, which is one of the most innovative approaches looking to change the course of AD. This technology is based on synthetic peptides or monoclonal antibodies (mAb) to reduce Aβ levels in the brain and slow down the advance of neurodegeneration. Hence, this article reviews the state of the art about AD neuropathogenesis, the traditional pharmacologic treatment, as well as the modern active and passive immunization describing approved drugs, and drug prototypes currently under investigation in different clinical trials. In addition, future perspectives on immunotherapeutic strategies for AD and the rise of the aptamer technology as a non-immunogenic alternative to curb the disease progression are discussed.

Matrix Remodeling Enzymes as Potential Fluid Biomarkers of Neurodegeneration in Alzheimer's Disease

This study investigated the diagnostic accuracy of plasma biomarkers-specifically, matrix metalloproteinase (MMP-9), tissue inhibitor of metalloproteinase (TIMP-1), CD147, and the MMP-/TIMP-1 ratio in patients with Alzheimer's disease (AD) dementia. The research cohort comprised patients diagnosed with probable AD dementia and a control group of cognitively unimpaired (CU) individuals. Neuroradiological assessments included brain magnetic resonance imaging (MRI) following dementia protocols, with subsequent volumetric analysis. Additionally, cerebrospinal fluid (CSF) AD biomarkers were classified using the A/T/N system, and apolipoprotein E (APOE) ε4 carrier status was determined. Findings revealed elevated plasma levels of MMP-9 and TIMP-1 in AD dementia patients compared to CU individuals. Receiver operating characteristic (ROC) curve analysis demonstrated significant differences in the areas under the curve (AUC) for MMP-9 (p < 0.001) and TIMP-1 (p < 0.001). Notably, plasma TIMP-1 levels were significantly lower in APOE ε4+ patients than in APOE ε4- patients (p = 0.041). Furthermore, APOE ε4+ patients exhibited reduced hippocampal volume, particularly in total, right, and left hippocampal measurements. TIMP-1 levels exhibited a positive correlation, while the MMP-9/TIMP-1 ratio showed a negative correlation with hippocampal volume parameters. This study sheds light on the potential use of TIMP-1 as a diagnostic marker and its association with hippocampal changes in AD.

Alzheimer's Disease: A Suitable Case for Treatment with Precision Medicine?

Alzheimer's disease (AD) is the most common cause of neurodegenerative impairment in elderly people. Clinical characteristics include short-term memory loss, confusion, hallucination, agitation, and behavioural disturbance. Owing to evolving research in biomarkers AD can be discovered at early onset, but the disease is currently considered a continuum, which suggests that pharmacotherapy is most efficacious in the preclinical phase, possibly 15 - 20 years before discernible onset. Present developments in AD therapy aim to respond to this understanding and go beyond the drug families that relieve clinical symptoms. Another important factor in this development is the emergence of precision medicine that aims to tailor treatment to specific patients or patient subgroups. This relatively new platform would categorize AD patients on the basis of parameters like clinical aspects, brain imaging, genetic profiling, clinical genetics and epidemiological factors. This review enlarges on recent progress in the design and clinical use of antisense molecules, antibodies, antioxidants, small molecules and gene editing to stop AD progress and possibly reverse the disease on the basis of relevant biomarkers.

Induced-pluripotent stem cells and neuroproteomics as tools for studying neurodegeneration

The investigation of neurodegenerative diseases advanced significantly with the advent of cell-reprogramming technology, leading to the creation of new models of human illness. These models, derived from induced pluripotent stem cells (iPSCs), facilitate the study of sporadic as well as hereditary diseases and provide a comprehensive understanding of the molecular mechanisms involved with neurodegeneration. Through proteomics, a quantitative tool capable of identifying thousands of proteins from small sample volumes, researchers have attempted to identify disease mechanisms by detecting differentially expressed proteins and proteoforms in disease models, biofluids, and postmortem brain tissue. The integration of these two technologies allows for the identification of novel pathological targets within the realm of neurodegenerative diseases. Here, we highlight studies from the past 5 years on the contributions of iPSCs within neuroproteomic investigations, which uncover the molecular mechanisms behind these illnesses.

Tauroursodeoxycholic acid: a bile acid that may be used for the prevention and treatment of Alzheimer's disease

Alzheimer's disease (AD) is a prevalent neurodegenerative disease that has become one of the main factors affecting human health. It has serious impacts on individuals, families, and society. With the development of population aging, the incidence of AD will further increase worldwide. Emerging evidence suggests that many physiological metabolic processes, such as lipid metabolism, are implicated in the pathogenesis of AD. Bile acids, as the main undertakers of lipid metabolism, play an important role in the occurrence and development of Alzheimer's disease. Tauroursodeoxycholic acid, an endogenous bile acid, has been proven to possess therapeutic effects in different neurodegenerative diseases, including Alzheimer's disease. This review tries to find the relationship between bile acid metabolism and AD, as well as explore the therapeutic potential of bile acid taurocursodeoxycholic acid for this disease. The potential mechanisms of taurocursodeoxycholic acid may include reducing the deposition of Amyloid-β protein, regulating apoptotic pathways, preventing tau hyperphosphorylation and aggregation, protecting neuronal synapses, exhibiting anti-inflammatory properties, and improving metabolic disorders. The objective of this study is to shed light on the use of tauroursodeoxycholic acid preparations in the prevention and treatment of AD, with the aim of identifying effective treatment targets and clarifying various treatment mechanisms involved in this disease.

CoQ10 and Mitochondrial Dysfunction in Alzheimer's Disease

The progress in understanding the pathogenesis and treatment of Alzheimer's disease (AD) is based on the recognition of the primary causes of the disease, which can be deduced from the knowledge of risk factors and biomarkers measurable in the early stages of the disease. Insights into the risk factors and the time course of biomarker abnormalities point to a role for the connection of amyloid beta (Aβ) pathology, tau pathology, mitochondrial dysfunction, and oxidative stress in the onset and development of AD. Coenzyme Q10 (CoQ10) is a lipid antioxidant and electron transporter in the mitochondrial electron transport system. The availability and activity of CoQ10 is crucial for proper mitochondrial function and cellular bioenergetics. Based on the mitochondrial hypothesis of AD and the hypothesis of oxidative stress, the regulation of the efficiency of the oxidative phosphorylation system by means of CoQ10 can be considered promising in restoring the mitochondrial function impaired in AD, or in preventing the onset of mitochondrial dysfunction and the development of amyloid and tau pathology in AD. This review summarizes the knowledge on the pathophysiology of AD, in which CoQ10 may play a significant role, with the aim of evaluating the perspective of the pharmacotherapy of AD with CoQ10 and its analogues.

Apolipoprotein E Gene in α-Synucleinopathies: A Narrative Review

In this narrative review, we delved into the intricate interplay between Apolipoprotein E (APOE) alleles (typically associated with Alzheimer's disease-AD) and alpha-synucleinopathies (aS-pathies), involving Parkinson's disease (PD), Parkinson's disease dementia (PDD), dementia with Lewy bodies (DLB), and multiple-system atrophy (MSA). First, in-vitro, animal, and human-based data on the exacerbating effect of APOE4 on LB pathology were summarized. We found robust evidence that APOE4 carriage constitutes a risk factor for PDD-APOE2, and APOE3 may not alter the risk of developing PDD. We confirmed that APOE4 copies confer an increased hazard towards DLB, as well. Again APOE2 and APOE3 appear unrelated to the risk of conversion. Of note, in individuals with DLB APOE4, carriage appears to be intermediately prevalent between AD and PDD-PD (AD > DLB > PDD > PD). Less consistency existed when it came to PD; APOE-PD associations tended to be markedly modified by ethnicity. Finally, we failed to establish an association between the APOE gene and MSA. Phenotypic associations (age of disease onset, survival, cognitive-neuropsychiatric- motor-, and sleep-related manifestations) between APOE alleles, and each of the aforementioned conditions were also outlined. Finally, a synopsis of literature gaps was provided followed by suggestions for future research.

APOE genotype dictates lipidomic signatures in primary human hepatocytes

Apolipoprotein E (APOE) genetic variants are most notably known for their divergent impact on the risk of developing Alzheimer's disease. While APOE genotype has been consistently shown to modulate lipid metabolism in a variety of cellular contexts, the effect of APOE alleles on the lipidome in hepatocytes is unknown. In this study, we investigated the contribution of APOE alleles to lipidomic profiles of donor-derived primary human hepatocytes from 77 subjects. Lipidomic data obtained by liquid chromatography-mass spectrometry were analyzed across ε2/ε3, ε3/ε3, and ε3/ε4 genotypes to reveal how APOE modulates lipid relative levels over age and between groups. Hepatic APOE concentration, measured by ELISA, was assessed for correlation with lipid abundance in subjects grouped as per APOE genotype and sex. APOE genotype-specific differential lipidomic signatures associated with age for multiple lipid classes but did not differ between sexes. Compared to ε2/ε3, ε3/ε4 hepatocytes had higher abundance of acylcarnitines (AC) and acylphosphatidylglycerol (AcylPG) as a class, as well as higher medium and long-chain ACs, AcylPG, phosphatidylglycerol (PG), bis(monoacylglycerol)phosphate (BMP), monoacylglycerol (MG) and diacylglycerol (DG) species. The ε3/ε4 hepatocytes also exhibited a higher abundance of medium and long-chain ACs compared to the ε3/ε3 hepatocytes. Only in the ε3/ε4 hepatocytes, APOE concentration was lower and showed a negative correlation with BMP levels, specifically in females. APOE genotype dictates a differential lipidome in primary human hepatocytes. The lipids involved suggest mitochondrial dysfunction with accompanying alterations in neutral lipid storage, reflective of a general disturbance of free fatty acid metabolism in human hepatocytes with the ε4 allele.

Alzheimer's disease and clinical trials

Alzheimer's disease (AD) is spreading its root disproportionately among the worldwide population. Many genes have been identified as the hallmarks of AD. Based upon the knowledge, many clinical trials have been designed and conducted. Attempts have been made to alleviate the pathology associated with AD by targeting the molecular products of these genes. Irrespective of the understanding on the genetic component of AD, many clinical trials have failed and imposed greater challenges on the path of drug discovery. Therefore, this review aims to identify research and review articles to pinpoint the limitations of drug candidates (thiethylperazine, CT1812, crenezumab, CNP520, and lecanemab), which are under or withdrawn from clinical trials. Thorough analysis of the cross-talk pathways led to the identification of many confounding factors, which could interfere with the success of clinical trials with drug candidates such as thiethylperazine, CT1812, crenezumab, and CNP520. Though these drug candidates were enrolled in clinical trials, yet literature review shows many limitations. These limitations raise many questions on the rationale behind the enrollments of these drug candidates in clinical trials. A meticulous prior assessment of the outcome of clinical studies may stop risky clinical trials at their inceptions. This may save time, money, and resources.

Effects of DHA on cognitive dysfunction in aging and Alzheimer's disease: The mediating roles of ApoE

The prevalence of Alzheimer's disease (AD) continues to rise due to the increasing aging population. Among the various genetic factors associated with AD, apolipoprotein E (ApoE), a lipid transporter, stands out as the primary genetic risk factor. Specifically, individuals carrying the ApoE4 allele exhibit a significantly higher risk. However, emerging research indicates that dietary factors play a prominent role in modifying the risk of AD. Docosahexaenoic acid (DHA), a prominent ω-3 fatty acid, has garnered considerable attention for its potential to ameliorate cognitive function. The intricate interplay between DHA and the ApoE genotype within the brain, which may influence DHA's utilization and functionality, warrants further investigation. This review meticulously examines experimental and clinical studies exploring the effects of DHA on cognitive decline. Special emphasis is placed on elucidating the role of ApoE gene polymorphism and the underlying mechanisms are discussed. These studies suggest that early DHA supplementation may confer benefits to cognitively normal older adults carrying the ApoE4 gene. However, once AD develops, ApoE4 non-carriers may experience greater benefits compared to ApoE4 carriers, although the overall effectiveness of DHA supplementation at this stage is limited. Potential mechanisms underlying these differential effects may include accelerated DHA catabolism in ApoE4 carriers, impaired transport across the blood-brain barrier (BBB), and compromised lipidation and circulatory function in ApoE4 carriers. Thus, the supplementation of DHA may represent a potential intervention strategy aimed at compensating for these deficiencies in ApoE4 carriers prior to the onset of AD.

The role of N-methyl-D-aspartate glutamate receptors in Alzheimer's disease: From pathophysiology to therapeutic approaches

N-Methyl-D-aspartate glutamate receptors (NMDARs) are involved in multiple physiopathological processes, including synaptic plasticity, neuronal network activities, excitotoxic events, and cognitive impairment. Abnormalities in NMDARs can initiate a cascade of pathological events, notably in Alzheimer's disease (AD) and even other neuropsychiatric disorders. The subunit composition of NMDARs is plastic, giving rise to a diverse array of receptor subtypes. While they are primarily found in neurons, NMDAR complexes, comprising both traditional and atypical subunits, are also present in non-neuronal cells, influencing the functions of various peripheral tissues. Furthermore, protein-protein interactions within NMDAR complexes has been linked with Aβ accumulation, tau phosphorylation, neuroinflammation, and mitochondrial dysfunction, all of which potentially served as an obligatory relay of cognitive impairment. Nonetheless, the precise mechanistic link remains to be fully elucidated. In this review, we provided an in-depth analysis of the structure and function of NMDAR, investigated their interactions with various pathogenic proteins, discussed the current landscape of NMDAR-based therapeutics, and highlighted the remaining challenges during drug development.

Alzheimer's disease: The role of proteins in formation, mechanisms, and new therapeutic approaches

Alzheimer's disease (AD) is a progressive neurological disorder that affects the central nervous system (CNS), leading to memory and cognitive decline. In AD, the brain experiences three main structural changes: a significant decrease in the quantity of neurons, the development of neurofibrillary tangles (NFT) composed of hyperphosphorylated tau protein, and the formation of amyloid beta (Aβ) or senile plaques, which are protein deposits found outside cells and surrounded by dystrophic neurites. Genetic studies have identified four genes associated with autosomal dominant or familial early-onset AD (FAD): amyloid precursor protein (APP), presenilin 1 (PS1), presenilin 2 (PS2), and apolipoprotein E (ApoE). The formation of plaques primarily involves the accumulation of Aβ, which can be influenced by mutations in APP, PS1, PS2, or ApoE genes. Mutations in the APP and presenilin (PS) proteins can cause an increased amyloid β peptides production, especially the further form of amyloidogenic known as Aβ42. Apart from genetic factors, environmental factors such as cytokines and neurotoxins may also have a significant impact on the development and progression of AD by influencing the formation of amyloid plaques and intracellular tangles. Exploring the causes and implications of protein aggregation in the brain could lead to innovative therapeutic approaches. Some promising therapy strategies that have reached the clinical stage include using acetylcholinesterase inhibitors, estrogen, nonsteroidal anti-inflammatory drugs (NSAIDs), antioxidants, and antiapoptotic agents. The most hopeful therapeutic strategies involve inhibiting activity of secretase and preventing the β-amyloid oligomers and fibrils formation, which are associated with the β-amyloid fibrils accumulation in AD. Additionally, immunotherapy development holds promise as a progressive therapeutic approach for treatment of AD. Recently, the two primary categories of brain stimulation techniques that have been studied for the treatment of AD are invasive brain stimulation (IBS) and non-invasive brain stimulation (NIBS). In this article, the amyloid proteins that play a significant role in the AD formation, the mechanism of disease formation as well as new drugs utilized to treat of AD will be reviewed.

Clinical and biological relevance of glial fibrillary acidic protein in Alzheimer's disease

INTRODUCTION

There is a tremendous need for identifying reliable blood-based biomarkers for Alzheimer's disease (AD) that are tied to the biological ATN (amyloid, tau and neurodegeneration) framework as well as clinical assessment and progression.

METHODS

One hundred forty-four elderly participants underwent 18F-AV45 positron emission tomography (PET) scan, structural magnetic resonance imaging (MRI) scan, and blood sample collection. The composite standardized uptake value ratio (SUVR) was derived from 18F-AV45 PET to assess brain amyloid burden, and the hippocampal volume was determined from structural MRI scans. Plasma glial fibrillary acidic protein (GFAP), phosphorylated tau-181 (ptau-181), and neurofilament light (NfL) measured by single molecular array (SIMOA) technology were assessed with respect to ATN framework, genetic risk factor, age, clinical assessment, and future functional decline among the participants.

RESULTS

Among the three plasma markers, GFAP best discriminated participants stratified by clinical diagnosis and brain amyloid status. Age was strongly associated with NfL, followed by GFAP and ptau-181 at much weaker extent. Brain amyloid was strongly associated with plasma GFAP and ptau-181 and to a lesser extent with plasma NfL. Moderate association was observed between plasma markers. Hippocampal volume was weakly associated with all three markers. Elevated GFAP and ptau-181 were associated with worse cognition, and plasma GFAP was the most predictive of future functional decline. Combining GFAP and ptau-181 together was the best model to predict brain amyloid status across all participants (AUC = 0.86) or within cognitively impaired participants (AUC = 0.93); adding NfL as an additional predictor only had a marginal improvement.

CONCLUSION

Our findings indicate that GFAP is of potential clinical utility in screening amyloid pathology and predicting future cognitive decline. GFAP, NfL, and ptau-181 were moderately associated with each other, with discrepant relevance to age, sex, and AD genetic risk, suggesting their relevant but differential roles for AD assessment. The combination of GFAP with ptau-181 provides an accurate model to predict brain amyloid status, with the superior performance of GFAP over ptau-181 when the prediction is limited to cognitively impaired participants.

Pathophysiological Aspects and Therapeutic Armamentarium of Alzheimer's Disease: Recent Trends and Future Development

Alzheimer's disease (AD) is the primary cause of dementia and is characterized by the death of brain cells due to the accumulation of insoluble amyloid plaques, hyperphosphorylation of tau protein, and the formation of neurofibrillary tangles within the cells. AD is also associated with other pathologies such as neuroinflammation, dysfunction of synaptic connections and circuits, disorders in mitochondrial function and energy production, epigenetic changes, and abnormalities in the vascular system. Despite extensive research conducted over the last hundred years, little is established about what causes AD or how to effectively treat it. Given the severity of the disease and the increasing number of affected individuals, there is a critical need to discover effective medications for AD. The US Food and Drug Administration (FDA) has approved several new drug molecules for AD management since 2003, but these drugs only provide temporary relief of symptoms and do not address the underlying causes of the disease. Currently, available medications focus on correcting the neurotransmitter disruption observed in AD, including cholinesterase inhibitors and an antagonist of the N-methyl-D-aspartate (NMDA) receptor, which temporarily alleviates the signs of dementia but does not prevent or reverse the course of AD. Research towards disease-modifying AD treatments is currently underway, including gene therapy, lipid nanoparticles, and dendrimer-based therapy. These innovative approaches aim to target the underlying pathological processes of AD rather than just managing the symptoms. This review discusses the novel aspects of pathogenesis involved in the causation of AD of AD and in recent developments in the therapeutic armamentarium for the treatment of AD such as gene therapy, lipid nanoparticles, and dendrimer-based therapy, and many more.

Elevated ApoE, ApoJ and lipoprotein-bound α-synuclein levels in cerebrospinal fluid from Parkinson's disease patients - Validation in the BioFIND cohort

BACKGROUND

The progressive accumulation, aggregation, and spread of α-synuclein (aSN) are common hallmarks of Parkinson's disease (PD) pathology. The genotype of apolipoprotein E (ApoE) influences PD progression. Recently we found that aSN co-localize with apolipoproteins on lipoprotein vesicles. We reported an increased level of ApoE, ApoJ and lipoprotein-bound aSN in CSF from early PD patients compared to matched controls. We also found reduced plasma ApoAI in PD patients.

OBJECTIVE

In this study, we used the same approach on the BioFIND cohort to validate our previous results and extended the studies to examine correlations with ApoE genotype, demographic variables, clinical symptoms and other biochemical findings reported in the BioFIND cohort.

METHODS

For the assessment, we used Western-Blot (WB) technique for apolipoproteins measurements in CSF and plasma from PD patients and healthy controls. Further, for measurement of aSN bound to lipoproteins, we combined immunodepletion with the enzyme-linked immunosorbent assay (ELISA).

RESULTS

Levels of ApoE, ApoJ and lipoprotein bound aSN were significantly increased in CSF from PD patients compared to controls. We also observed decreased levels of ApoAI and ApoJ in plasma from PD patients compared to controls.

CONCLUSIONS

Concluding, the present data validated our previous findings. Altered lipoproteins appear to be important in early PD pathology and may be involved in mechanisms underlying aSN cell-to-cell transfer in the nervous system and be developed in algorithms for early diagnosis of PD.

Metrologically Traceable Quantification of 3 Apolipoprotein E Isoforms in Cerebrospinal Fluid

BACKGROUND

APOE genotype is associated with Alzheimer disease. Thus, the concentration of apolipoprotein E (apoE) isoforms in cerebrospinal fluid (CSF) could be altered in dementia. However, conflicting results have been obtained in different studies. Carefully validated and standardized assays could improve the interpretation of research findings, allow their replication in other laboratories, and generalize their application.

METHODS

To evaluate this hypothesis, we aimed to develop, validate, and standardize a new measurement procedure using LC-MS/MS. Purified recombinant apoE protein standards (E2, E3, E4) were thoroughly characterized and used to assign the concentration of a matrix-matched calibration material that contained each apoE isoform, which ensured the metrological traceability of results.

RESULTS

The assay of each isoform in human CSF was precise (≤11%CV) and of moderate throughput (approximately 80 samples per day). It demonstrated good linearity and parallelism for lumbar CSF, ventricular CSF, and bovine CSF. The use of an SI-traceable matrix-matched calibrator enabled precise and accurate measurements. There was no association observed between total apoE concentration and the number of Ɛ4 alleles in a cohort of 322 participants. However, the concentration of each isoform was significantly different in heterozygotes, with E4 > E3 > E2. Isoform concentrations were associated with cognitive and motor symptoms but contributed negligibly to a predictive model of cognitive impairment that included established CSF biomarkers.

CONCLUSIONS

Our method simultaneously measures each apoE isoform in human CSF with excellent precision and accuracy. A secondary matrix-matched material has been developed and is available to other laboratories to improve interlaboratory agreement.

Brain metabolism in Alzheimer's disease: biological mechanisms of exercise

Alzheimer's disease (AD) is a major subtype of neurodegenerative dementia caused by long-term interactions and accumulation of multiple adverse factors, accompanied by dysregulation of numerous intracellular signaling and molecular pathways in the brain. At the cellular and molecular levels, the neuronal cellular milieu of the AD brain exhibits metabolic abnormalities, compromised bioenergetics, impaired lipid metabolism, and reduced overall metabolic capacity, which lead to abnormal neural network activity and impaired neuroplasticity, thus accelerating the formation of extracellular senile plaques and intracellular neurofibrillary tangles. The current absence of effective pharmacological therapies for AD points to the urgent need to investigate the benefits of non-pharmacological approaches such as physical exercise. Despite the evidence that regular physical activity can improve metabolic dysfunction in the AD state, inhibit different pathophysiological molecular pathways associated with AD, influence the pathological process of AD, and exert a protective effect, there is no clear consensus on the specific biological and molecular mechanisms underlying the advantages of physical exercise. Here, we review how physical exercise improves crucial molecular pathways and biological processes associated with metabolic disorders in AD, including glucose metabolism, lipid metabolism, Aβ metabolism and transport, iron metabolism and tau pathology. How metabolic states influence brain health is also presented. A better knowledge on the neurophysiological mechanisms by which exercise improves AD metabolism can contribute to the development of novel drugs and improvement of non-pharmacological interventions.

Neuronal ApoE4 in Alzheimer's disease and potential therapeutic targets

The most prevalent genetic risk factor for Alzheimer's disease (AD) is Apolipoprotein E (ApoE), a gene located on chromosome 19 that encodes three alleles (e2, e3, and e4) that give rise to the ApoE subtypes E2, E3, and E4, respectively. E2 and E4 have been linked to increased plasma triglyceride concentrations and are known to play a critical role in lipoprotein metabolism. The prominent pathological features of AD mainly include senile plaques formed by amyloid β (Aβ₄₂) aggregation and neuronal fibrous tangles (NFTs), and the deposited plaques are mainly composed of Aβ hyperphosphorylation and truncated head. In the central nervous system, the ApoE protein is primarily derived from astrocytes, but ApoE is also produced when neurons are stressed or affected by certain stress, injury, and aging conditions. ApoE4 in neurons induces Aβ and tau protein pathologies, leading to neuroinflammation and neuronal damage, impairing learning and memory functions. However, how neuronal ApoE4 mediates AD pathology remains unclear. Recent studies have shown that neuronal ApoE4 may lead to greater neurotoxicity, which increases the risk of AD development. This review focuses on the pathophysiology of neuronal ApoE4 and explains how neuronal ApoE4 mediates Aβ deposition, pathological mechanisms of tau protein hyperphosphorylation, and potential therapeutic targets.

Microvascular Contributions to Alzheimer Disease Pathogenesis: Is Alzheimer Disease Primarily an Endotheliopathy?

Alzheimer disease (AD) models are based on the notion that abnormal protein aggregation is the primary event in AD, which begins a decade or longer prior to symptom onset, and culminates in neurodegeneration; however, emerging evidence from animal and clinical studies suggests that reduced blood flow due to capillary loss and endothelial dysfunction are early and primary events in AD pathogenesis, which may precede amyloid and tau aggregation, and contribute to neuronal and synaptic injury via direct and indirect mechanisms. Recent data from clinical studies suggests that endothelial dysfunction is closely associated with cognitive outcomes in AD and that therapeutic strategies which promote endothelial repair in early AD may offer a potential opportunity to prevent or slow disease progression. This review examines evidence from clinical, imaging, neuropathological, and animal studies supporting vascular contributions to the onset and progression of AD pathology. Together, these observations support the notion that the onset of AD may be primarily influenced by vascular, rather than neurodegenerative, mechanisms and emphasize the importance of further investigations into the vascular hypothesis of AD.

Development and validation of a 13-gene signature associated with immune function for the detection of Alzheimer's disease

Current knowledge of Alzheimer's disease (AD) etiology and effective therapy remains limited. Thus, the identification of biomarkers is crucial to improve the detection and treatment of patients with AD. Using robust rank aggregation method to analyze the microarray data from Gene Expression Omnibus database, we identified 1138 differentially expressed genes in AD. We then explored 13 hub genes by weighted gene co-expression network analysis, least absolute shrinkage, and selection operator, and logistic regression in the training dataset. The detection model, which composed of CD163, CDC42SE1, CECR6, CSF1R, CYP27A1, EIF4E3, H2AFJ, IFIT2, IL10RA, KIAA1324, PSTPIP1, SLA, and TBC1D2 genes, along with APOE gene, showed that the area under the curve for detecting AD was 0.821 (95% confidence interval [CI] = 0.782-0.861) and the model was validated in ADNI dataset (area under the curve = 0.776; 95%CI = 0.686-0.865). Notably, the 13 genes in the model were highly enriched in immune function. These findings have implications for the detection and therapeutic target of AD.

Modern Approaches to the Diagnosis of Cognitive Impairment and Alzheimer's Disease: A Narrative Literature Review

BACKGROUND

The aging of the worlds population leads to an increase in the prevalence of age-related diseases, including cognitive impairment. At the stage of dementia, therapeutic interventions become usually ineffective. Therefore, researchers and clinical practitioners today are looking for methods that allow for early diagnosis of cognitive impairment, including techniques that are based on the use of biological markers.

AIM

The aim of this literature review is to delve into scientific papers that are centered on modern laboratory tests for Alzheimers disease, including tests for biological markers at the early stages of cognitive impairment.

METHODS

The authors have carried out a descriptive review of scientific papers published from 2015 to 2023. Studies that are included in the PubMed and Web of Science electronic databases were analyzed. A descriptive analysis was used to summarized the gleaned information.

RESULTS

Blood and cerebrospinal fluid (CSF) biomarkers, as well as the advantages and disadvantages of their use, are reviewed. The most promising neurotrophic, neuroinflammatory, and genetic markers, including polygenic risk models, are also discussed.

CONCLUSION

The use of biomarkers in clinical practice will contribute to the early diagnosis of cognitive impairment associated with Alzheimers disease. Genetic screening tests can improve the detection threshold of preclinical abnormalities in the absence of obvious symptoms of cognitive decline. The active use of biomarkers in clinical practice, in combination with genetic screening for the early diagnosis of cognitive impairment in Alzheimers disease, can improve the timeliness and effectiveness of medical interventions.

Protein Interactome of Amyloid-β as a Therapeutic Target

The amyloid concept of Alzheimer's disease (AD) assumes the β-amyloid peptide (Aβ) as the main pathogenic factor, which injures neural and other brain cells, causing their malfunction and death. Although Aβ has been documented to exert its cytotoxic effect in a solitary manner, there is much evidence to claim that its toxicity can be modulated by other proteins. The list of such Aβ co-factors or interactors includes tau, APOE, transthyretin, and others. These molecules interact with the peptide and affect the ability of Aβ to form oligomers or aggregates, modulating its toxicity. Thus, the list of potential substances able to reduce the harmful effects of the peptide should include ones that can prevent the pathogenic interactions by specifically binding Aβ and/or its partners. In the present review, we discuss the data on Aβ-based complexes in AD pathogenesis and on the compounds directly targeting Aβ or the destructors of its complexes with other polypeptides.

Direct Conversion of Fibroblast into Neurons for Alzheimer's Disease Research: A Systematic Review

BACKGROUND

Alzheimer's disease (AD) is a prevalent neurodegenerative disorder without a cure. Innovative disease models, such as induced neurons (iNs), could enhance our understanding of AD mechanisms and accelerate treatment development. However, a review of AD human iN studies is necessary to consolidate knowledge.

OBJECTIVE

The objective of this review is to examine the current body of literature on AD human iN cells and provide an overview of the findings to date.

METHODS

We searched two databases for relevant studies published between 2010 and 2023, identifying nine studies meeting our criteria.

RESULTS

Reviewed studies indicate the feasibility of generating iNs directly from AD patients' fibroblasts using chemical induction or viral vectors. These cells express mature neuronal markers, including MAP-2, NeuN, synapsin, and tau. However, most studies were limited in sample size and primarily focused on autosomal dominant familial AD (FAD) rather than the more common sporadic forms of AD. Several studies indicated that iNs derived from FAD fibroblasts exhibited abnormal amyloid-β metabolism, a characteristic feature of AD in humans. Additionally, elevated levels of hyperphosphorylated tau, another hallmark of AD, were reported in some studies.

CONCLUSION

Although only a limited number of small-scale studies are currently available, AD patient-derived iNs hold promise as a valuable model for investigating AD pathogenesis. Future research should aim to conduct larger studies, particularly focusing on sporadic AD cases, to enhance the clinical relevance of the findings for the broader AD patient population. Moreover, these cells can be utilized in screening potential novel treatments for AD.