Butyrylcholinesterase K and Apolipoprotein E-ɛ4 Reduce the Age of Onset of Alzheimer’s Disease, Accelerate Cognitive Decline, and Modulate Donepezil Response in Mild Cognitively Impaired Subjects

Onset of Alzheimer disease in apolipoprotein ɛ4 carriers is earlier in butyrylcholinesterase K variant carriers

BACKGROUND

The authors sought to examine the impact of the K-variant of butyrylcholinesterase (BCHE-K) carrier status on age-at-diagnosis of Alzheimer disease (AD) in APOE4 carriers.

METHODS

Patients aged 50-74 years with cerebrospinal fluid (CSF) biomarker-confirmed AD, were recruited to clinical trial (NCT03186989 since June 14, 2017). Baseline demographics, disease characteristics, and biomarkers were evaluated in 45 patients according to BCHE-K and APOE4 allelic status in this post-hoc study.

RESULTS

In APOE4 carriers (N = 33), the mean age-at-diagnosis of AD in BCHE-K carriers (n = 11) was 6.4 years earlier than in BCHE-K noncarriers (n = 22, P < .001, ANOVA). In APOE4 noncarriers (N = 12) there was no observed influence of BCHE-K. APOE4 carriers with BCHE-K also exhibited slightly higher amyloid and tau accumulations compared to BCHE-K noncarriers. A predominantly amyloid, limited tau, and limbic-amnestic phenotype was exemplified by APOE4 homozygotes with BCHE-K. In the overall population, multiple regression analyses demonstrated an association of amyloid accumulation with APOE4 carrier status (P < .029), larger total brain ventricle volume (P < .021), less synaptic injury (Ng, P < .001), and less tau pathophysiology (p-tau181, P < .005). In contrast, tau pathophysiology was associated with more neuroaxonal damage (NfL, P = .002), more synaptic injury (Ng, P < .001), and higher levels of glial activation (YKL-40, P = .01).

CONCLUSION

These findings have implications for the genetic architecture of prognosis in early AD, not the genetics of susceptibility to AD. In patients with early AD aged less than 75 years, the mean age-at-diagnosis of AD in APOE4 carriers was reduced by over 6 years in BCHE-K carriers versus noncarriers. The functional status of glia may explain many of the effects of APOE4 and BCHE-K on the early AD phenotype.

TRIAL REGISTRATION

NCT03186989 since June 14, 2017.

Alzheimer's disease phenotype based upon the carrier status of the apolipoprotein E ɛ4 allele

The apolipoprotein E ɛ4 allele (APOE4) is universally acknowledged as the most potent genetic risk factor for Alzheimer's disease (AD). APOE4 promotes the initiation and progression of AD. Although the underlying mechanisms are unclearly understood, differences in lipid-bound affinity among the three APOE isoforms may constitute the basis. The protein APOE4 isoform has a high affinity with triglycerides and cholesterol. A distinction in lipid metabolism extensively impacts neurons, microglia, and astrocytes. APOE4 carriers exhibit phenotypic differences from non-carriers in clinical examinations and respond differently to multiple treatments. Therefore, we hypothesized that phenotypic classification of AD patients according to the status of APOE4 carrier will help specify research and promote its use in diagnosing and treating AD. Recent reviews have mainly evaluated the differences between APOE4 allele carriers and non-carriers from gene to protein structures, clinical features, neuroimaging, pathology, the neural network, and the response to various treatments, and have provided the feasibility of phenotypic group classification based on APOE4 carrier status. This review will facilitate the application of APOE phenomics concept in clinical practice and promote further medical research on AD.

Pharmacogenomics of Dementia: Personalizing the Treatment of Cognitive and Neuropsychiatric Symptoms

Dementia is a syndrome of global and progressive deterioration of cognitive skills, especially memory, learning, abstract thinking, and orientation, usually affecting the elderly. The most common forms are Alzheimer's disease, vascular dementia, and other (frontotemporal, Lewy body disease) dementias. The etiology of these multifactorial disorders involves complex interactions of various environmental and (epi)genetic factors and requires multiple forms of pharmacological intervention, including anti-dementia drugs for cognitive impairment, antidepressants, antipsychotics, anxiolytics and sedatives for behavioral and psychological symptoms of dementia, and other drugs for comorbid disorders. The pharmacotherapy of dementia patients has been characterized by a significant interindividual variability in drug response and the development of adverse drug effects. The therapeutic response to currently available drugs is partially effective in only some individuals, with side effects, drug interactions, intolerance, and non-compliance occurring in the majority of dementia patients. Therefore, understanding the genetic basis of a patient's response to pharmacotherapy might help clinicians select the most effective treatment for dementia while minimizing the likelihood of adverse reactions and drug interactions. Recent advances in pharmacogenomics may contribute to the individualization and optimization of dementia pharmacotherapy by increasing its efficacy and safety via a prediction of clinical outcomes. Thus, it can significantly improve the quality of life in dementia patients.

Predictors of response to acetylcholinesterase inhibitors in dementia: A systematic review

Background

The mainstay of therapy for many neurodegenerative dementias still relies on acetylcholinesterase inhibitors (AChEI); however, there is debate on various aspects of such treatment. A huge body of literature exists on possible predictors of response, but a comprehensive review is lacking. Therefore, our aim is to perform a systematic review of the predictors of response to AChEI in neurodegenerative dementias, providing a categorization and interpretation of the results.

Methods

We conducted a systematic review of the literature up to December 31st, 2021, searching five different databases and registers, including studies on rivastigmine, donepezil, and galantamine, with clearly defined criteria for the diagnosis of dementia and the response to AChEI therapy. Records were identified through the string: predict * AND respon * AND (acetylcholinesterase inhibitors OR donepezil OR rivastigmine OR galantamine). The results were presented narratively.

Results

We identified 1,994 records in five different databases; after exclusion of duplicates, title and abstract screening, and full-text retrieval, 122 studies were finally included.

Discussion

The studies show high heterogeneity in duration, response definition, drug dosage, and diagnostic criteria. Response to AChEI seems associated with correlates of cholinergic deficit (hallucinations, fluctuating cognition, substantia innominate atrophy) and preserved cholinergic neurons (faster alpha on REM sleep EEG, increased anterior frontal and parietal lobe perfusion after donepezil); white matter hyperintensities in the cholinergic pathways have shown inconsistent results. The K-variant of butyrylcholinesterase may correlate with better response in late stages of disease, while the role of polymorphisms in other genes involved in the cholinergic system is controversial. Factors related to drug availability may influence response; in particular, low serum albumin (for donepezil), CYP2D6 variants associated with reduced enzymatic activity and higher drug doses are the most consistent predictors, while AChEI concentration influence on clinical outcomes is debatable. Other predictors of response include faster disease progression, lower serum cholesterol, preserved medial temporal lobes, apathy, absence of concomitant diseases, and absence of antipsychotics. Short-term response may predict subsequent cognitive response, while higher education might correlate with short-term good response (months), and long-term poor response (years). Age, gender, baseline cognitive and functional levels, and APOE relationship with treatment outcome is controversial.

Pharmacogenetic studies in Alzheimer disease

INTRODUCTION

Alzheimer disease (AD) is the most common cause of dementia and is considered one of the main causes of disability and dependence affecting quality of life in elderly people and their families. Current pharmacological treatment includes acetylcholinesterase inhibitors (donepezil, galantamine, rivastigmine) and memantine; however, only one-third of patients respond to treatment. Genetic factors have been shown to play a role in this inter-individual variability in drug response.

DEVELOPMENT

We review pharmacogenetic reports of AD-modifying drugs, the pharmacogenetic biomarkers included, and the phenotypes evaluated. We also discuss relevant methodological considerations for the design of pharmacogenetic studies into AD. A total of 33 pharmacogenetic reports were found; the majority of these focused on the variability in response to and metabolism of donepezil. Most of the patients included were from Caucasian populations, although some studies also include Korean, Indian, and Brazilian patients. CYP2D6 and APOE are the most frequently studied biomarkers. The associations proposed are controversial.

CONCLUSIONS

Potential pharmacogenetic biomarkers for AD have been identified; however, it is still necessary to conduct further research into other populations and to identify new biomarkers. This information could assist in predicting patient response to these drugs and contribute to better treatment decision-making in a context as complex as aging.

Role of Pharmacogenomics in Individualizing Treatment for Alzheimer's Disease

The development of Alzheimer's disease therapeutics has been challenging, with 99% of clinical trials failing to find a significant difference between drug and placebo. While the quest continues for more effective treatments, there is emerging evidence that pharmacogenetic considerations are important factors in regard to metabolism, efficacy, and toxicity of drugs. Currently, there are five US Food and Drug Administration-approved drugs for the treatment of Alzheimer's disease; three acetylcholinesterase inhibitors, memantine, and aducanumab. Introducing a limited genetic panel consisting of APOE4, CYP2D6*10, and BChE*K would optimize acetylcholinesterase inhibitor therapy, facilitate immunotherapy risk assessment, and inform an amyloid-related imaging abnormality surveillance schedule. In view of the genetic heterogeneity of Alzheimer's disease identified in genome-wide association studies, pharmacogenetics is expected to play an increasing role in mechanism-specific treatment strategies and personalized medicine.

Induced Pluripotent Stem Cells for Treatment of Alzheimer’s and Parkinson’s Diseases

Neurodegenerative diseases are a group of debilitating pathologies in which neuronal tissue dies due to the buildup of neurotoxic plaques, resulting in detrimental effects on cognitive ability, motor control, and everyday function. Stem cell technology offers promise in addressing this problem on multiple fronts, but the conventional sourcing of pluripotent stem cells involves harvesting from aborted embryonic tissue, which comes with strong ethical and practical concerns. The keystone discovery of induced pluripotent stem cell (iPSC) technology provides an alternative and endless source, circumventing the unfavorable issues with embryonic stem cells, and yielding fundamental advantages. This review highlights iPSC technology, the pathophysiology of two major neurodegenerative diseases, Alzheimer’s and Parkinson’s, and then illustrates current state-of-the-art approaches towards the treatment of the diseases using iPSCs. The technologies discussed in the review emphasize in vitro therapeutic neural cell and organoid development for disease treatment, pathological modeling of neurodegenerative diseases, and 3D bioprinting as it applies to both.

The Role of Vitamin E in Slowing Down Mild Cognitive Impairment: A Narrative Review

With the aging population, dementia emerges as a public health concern. In 2012, the Health and Retirement Study found that 8.8% of adults over 65 years suffered from dementia. The etiopathogenesis and treatment of dementia are not well understood. Antioxidant properties of Vitamin E and its major elements tocopherols and tocotrienols have been reported to be effective in slowing down the progression of dementia from its initial stage of Mild cognitive impairment (MCI). Therefore, the current review aims to explore the role of vitamin E on MCI. A literature search using the key words "Vitamin E, tocopherols, tocotrienols, and mild cognitive impairment" was conducted in MEDLINE (PubMed), CINAHL, and Google Scholar. The inclusion criteria were: (1) articles published in the past ten years; (2) published in English language; (3) published in peer-reviewed journals; and (4) descriptive and epidemiological or evaluation studies. Articles published prior to 2010, focused on other forms of dementia than MCI, grey literature and non-peer-reviewed articles were excluded. A total of 22 studies were included in the narrative synthesis. The results were equivocal. Eleven studies showed some level of the neuroprotective effect of Vitamin E, tocopherols and tocotrienols on the progression of MCI. The mixed results of this review suggest further exploration of the possible protective effects of Vitamin E on the development of dementia. Future studies can be conducted to decipher antioxidant properties of vitamin E and its association with slowing down the cognitive decline.

Open science datasets from PREVENT-AD, a longitudinal cohort of pre-symptomatic Alzheimer's disease

To move Alzheimer Disease (AD) research forward it is essential to collect data from large cohorts, but also make such data available to the global research community. We describe the creation of an open science dataset from the PREVENT-AD (PResymptomatic EValuation of Experimental or Novel Treatments for AD) cohort, composed of cognitively unimpaired older individuals with a parental or multiple-sibling history of AD. From 2011 to 2017, 386 participants were enrolled (mean age 63 years old ± 5) for sustained investigation among whom 349 have retrospectively agreed to share their data openly. Repositories are findable through the unified interface of the Canadian Open Neuroscience Platform and contain up to five years of longitudinal imaging data, cerebral fluid biochemistry, neurosensory capacities, cognitive, genetic, and medical information. Imaging data can be accessed openly at https://openpreventad.loris.ca while most of the other information, sensitive by nature, is accessible by qualified researchers at https://registeredpreventad.loris.ca. In addition to being a living resource for continued data acquisition, PREVENT-AD offers opportunities to facilitate understanding of AD pathogenesis.

Genetic Variants and Oxidative Stress in Alzheimer's Disease

In an aging society, the number of people suffering from Alzheimer's Disease (AD) is still growing. Currently, intensive research is being carried out on the pathogenesis of AD. The results of these studies indicated that oxidative stress plays an important role in the onset and development of this disease. Moreover, in AD oxidative stress is generated by both genetic and biochemical factors as well as the functioning of the systems responsible for their formation and removal. The genetic factors associated with the regulation of the redox system include TOMM40, APOE, LPR, MAPT, APP, PSEN1 and PSEN2 genes. The most important biochemical parameters related to the formation of oxidative species in AD are p53, Homocysteine (Hcy) and a number of others. The formation of Reactive Oxygen Species (ROS) is also related to the efficiency of the DNA repair system, the effectiveness of the apoptosis, autophagy and mitophagy processes as well as the antioxidant potential. However, these factors are responsible for the development of many disorders, often with similar clinical symptoms, especially in the early stages of the disease. The discovery of markers of the early diagnosis of AD may contribute to the introduction of pharmacotherapy and slow down the progression of this disease.

Therapeutic considerations for APOE and TOMM40 in Alzheimers disease: A tribute to Allen Roses MD

Introduction: Four years ago this Autumn, pioneering neurologist Prof. Allen. D. Roses passed away. Hence, we have taken time to reflect on his work and legacy in Alzheimer's disease (AD) research. Prof. Roses rejected the widely accepted amyloid hypothesis, which identifies amyloid beta (Aβ) protein accumulation within the brain as the cause of AD. Instead, he proposed that the epsilon type 4 allele of apolipoprotein (APOE- Ɛ4) and translocase of outer mitochondrial membrane 40 homolog (TOMM40) were preeminent factors in the pathogenesis and progression of AD, particularly in late-onset AD (LOAD). This rejection of the amyloid hypothesis has generated new investigations into APOE and TOMM40 as risk factors for AD. Areas covered: We discuss the contributions of Prof. Roses to AD research, describe how APOE-Ɛ4 and TOMM40 have been posited to trigger neuropathological changes leading to AD, and explore paths to future clinical applications built on the foundations of his research. Expert opinion: The unconventional methodology of targeting APOE and TOMM40 offers great potential for the development of effective preventive and disease-modifying AD interventions. Future preclinical and clinical investigations will greatly benefit from the groundbreaking scientific discoveries of Prof. Roses.

Structure and therapeutic uses of butyrylcholinesterase: Application in detoxification, Alzheimer's disease, and fat metabolism

Structural information of butyrylcholinesterase (BChE) and its variants associated with several diseases are discussed here. Pure human BChE has been proved safe and effective in treating organophosphorus (OPs) poisoning and has completed Phase 1 and 2 pharmacokinetic (PK) and safety studies. The introduction of specific mutations into native BChE to endow it a self-reactivating property has gained much progress in producing effective OPs hydrolases. The hydrolysis ability of native BChE on cocaine has been confirmed but was blocked to clinical application due to poor PK properties. Several BChE mutants with elevated cocaine hydrolysis activity were published, some of which have shown safety and efficiency in treating cocaine addiction of human. The increased level of BChE in progressed Alzheimer's disease patients made it a promising target to elevate acetylcholine level and attenuate cognitive status. A variety of selective BChE inhibitors with high inhibitory activity published in recent years are reviewed here. BChE could influence the weight and insulin secretion and resistance of BChE knockout (KO) mice through hydrolyzing ghrelin. The BChE-ghrelin pathway could also regulate aggressive behaviors of BChE-KO mice.

Management of mild cognitive impairment (MCI): The need for national and international guidelines

Objectives: To review available evidence of pharmacological and non-pharmacological treatment for MCI and analyse information and limitations in national and international guidelines.Methods: Experts from several European countries conducted a qualitative review of the literature on MCI and treatments for MCI, as well as respective chapters in national and international guidelines on dementia/MCI. Psychotherapeutic/psychosocial treatments were excluded from the review.Results: Consensus diagnostic criteria for MCI are available, making early recognition and accurate classification of MCI subtypes possible. MCI can be identified in a primary care setting. Further corroboration and differential diagnosis should be done at specialist level. Mixed pathologies are the rule in MCI, thus a multi-target treatment approach is a rational strategy. Promising evidence has been generated for multi-domain interventions. Limited evidence is available for different pharmacological classes that have been investigated in MCI clinical trials (e.g. acetylcholinesterase inhibitors). EGb 761^® improved symptoms in some clinical trials; it is the only pharmacological treatment recommended in existing guidelines for the symptomatic treatment of MCI.Conclusions: MCI is recognised as an important treatment target and some recent national guidelines have considered symptomatic treatment recommendations for MCI. However, more needs to be done, especially at an international level.

Diagnoses of Pathological States Based on Acetylcholinesterase and Butyrylcholinesterase

Two cholinesterases exist: Acetylcholinesterase (AChE) and butyrylcholinesterase (BChE). While AChE plays a crucial role in neurotransmissions, BChE has no specific function apart from the detoxification of some drugs and secondary metabolites from plants. Thus, both AChE and BChE can serve as biochemical markers of various pathologies. Poisoning by nerve agents like sarin, soman, tabun, VX, novichok and overdosing by drugs used in some neurodegenerative disorders like Alzheimer´s disease and myasthenia gravis, as well as poisoning by organophosphorus pesticides are relevant to this issue. But it appears that changes in these enzymes take place in other processes including oxidative stress, inflammation, some types of cancer and genetically conditioned diseases. In this review, the cholinesterases are introduced, the mechanism of inhibitors action is explained and the relations between the cholinesterases and pathologies are explained.

Pharmacogenetic considerations when prescribing cholinesterase inhibitors for the treatment of Alzheimer's disease

INTRODUCTION

Cholinergic dysfunction, demonstrated in the late 1970s and early 1980s, led to the introduction of acetylcholinesterase inhibitors (AChEIs) in 1993 (Tacrine) to enhance cholinergic neurotransmission as the first line of treatment against Alzheimer's disease (AD). The new generation of AChEIs, represented by Donepezil (1996), Galantamine (2001) and Rivastigmine (2002), is the only treatment for AD to date, together with Memantine (2003). AChEIs are not devoid of side-effects and their cost-effectiveness is limited. An option to optimize the correct use of AChEIs is the implementation of pharmacogenetics (PGx) in the clinical practice.

AREAS COVERED

(i) The cholinergic system in AD, (ii) principles of AD PGx, (iii) PGx of Donepezil, Galantamine, Rivastigmine, Huperzine and other treatments, and (iv) practical recommendations.

EXPERT OPINION

The most relevant genes influencing AChEI efficacy and safety are APOE and CYPs. APOE-4 carriers are the worst responders to AChEIs. With the exception of Rivastigmine (UGT2B7, BCHE-K), the other AChEIs are primarily metabolized via CYP2D6, CYP3A4, and UGT enzymes, with involvement of ABC transporters and cholinergic genes (CHAT, ACHE, BCHE, SLC5A7, SLC18A3, CHRNA7) in most ethnic groups. Defective variants may affect the clinical response to AChEIs. PGx geno-phenotyping is highly recommended prior to treatment.

Gene Polymorphisms Affecting the Pharmacokinetics and Pharmacodynamics of Donepezil Efficacy

Donepezil (DNP) is the first-line drug used for Alzheimer's disease (AD). However, the therapeutic response rate of patients to DNP varies from 20 to 60%. The main reason for the large differences in the clinical efficacy of DNP therapy is genetic factors, some of which affect pharmacokinetics (PK), while others affect pharmacodynamics (PD). Thus, much emphasis has been placed on the investigation of an association between PK- and PD-related gene polymorphisms and therapeutic response to DNP, but a consistent view does not yet exist. In this review, we summarize recent findings regarding genetic factors influencing the clinical efficacy of DNP, including substantial differences in individual responses as a consequence of polymorphisms in Cytochrome P450 (CYP) 2D6, CY3A4, CY3A5, APOE, ABCA1, ABCB1, ESR1, BCHE, PON-1, CHRNA7, and CHAT. We also discuss possible strategies for the evaluation of the clinical efficacy of DNP, with a specific focus on possible biomarkers of PK/PD parameters, and provide perspectives and limitations within the field, which will also be beneficial for understanding the multiple mechanisms of DNP therapy in AD.

Pharmacogenomics of Cognitive Dysfunction and Neuropsychiatric Disorders in Dementia

Symptomatic interventions for patients with dementia involve anti-dementia drugs to improve cognition, psychotropic drugs for the treatment of behavioral disorders (BDs), and different categories of drugs for concomitant disorders. Demented patients may take >6–10 drugs/day with the consequent risk for drug–drug interactions and adverse drug reactions (ADRs >80%) which accelerate cognitive decline. The pharmacoepigenetic machinery is integrated by pathogenic, mechanistic, metabolic, transporter, and pleiotropic genes redundantly and promiscuously regulated by epigenetic mechanisms. CYP2D6, CYP2C9, CYP2C19, and CYP3A4/5 geno-phenotypes are involved in the metabolism of over 90% of drugs currently used in patients with dementia, and only 20% of the population is an extensive metabolizer for this tetragenic cluster. ADRs associated with anti-dementia drugs, antipsychotics, antidepressants, anxiolytics, hypnotics, sedatives, and antiepileptic drugs can be minimized by means of pharmacogenetic screening prior to treatment. These drugs are substrates, inhibitors, or inducers of 58, 37, and 42 enzyme/protein gene products, respectively, and are transported by 40 different protein transporters. APOE is the reference gene in most pharmacogenetic studies. APOE-3 carriers are the best responders and APOE-4 carriers are the worst responders; likewise, CYP2D6-normal metabolizers are the best responders and CYP2D6-poor metabolizers are the worst responders. The incorporation of pharmacogenomic strategies for a personalized treatment in dementia is an effective option to optimize limited therapeutic resources and to reduce unwanted side-effects.

Interaction between Apolipoprotein E and Butyrylcholinesterase Genes on Risk of Alzheimer's Disease in a Prospective Cohort Study

BACKGROUND

An epistatic interaction between the ɛ4 allele of apolipoprotein E (APOEɛ4) gene and the K-variant of butyrylcholinesterase (BCHE-K) genes has been previously reported to increase risk of Alzheimer's disease (AD). However, these observations were largely from case-control studies with small sample sizes.

OBJECTIVE

To examine the interaction between APOEɛ4 and BCHE-K on: 1) the risk of incident AD and 2) rates of change in brain volumes and cognitive performance during the preclinical stages of AD in a prospective cohort study.

METHODS

The study sample for survival analysis included 691 Caucasian participants (age at baseline, 58.4±9.9 years; follow-up time,16.9±9.7 years) from the Baltimore Longitudinal Study of Aging. The neuroimaging sample included 302 participants with 1,388 magnetic resonance imaging (MRI) scans. Cognitive performance was assessed in 703 participants over 4,908 visits.

RESULTS

A total of 122 diagnoses (79 AD, 43 mild cognitive impairment [MCI]) were identified. Participants with both APOEɛ4 and BCHE-K variants had a 3.7-fold greater risk of AD (Hazard ratio [HR] 95% CI=1.99-6.89, p < 0.001) compared to non-carriers of both genes (APOE ɛ4 x BCHE-K interaction p = 0.025). There was no APOE ɛ4-BCHE-K interaction effect on rate of cognitive decline and brain atrophy.

CONCLUSION

The APOE and BCHE genes interact to influence risk of incident AD/MCI but not rates of brain atrophy and decline in cognitive performance before onset of cognitive impairment. This may suggest the epistatic interaction between APOE ɛ4 and BCHE-K on AD risk is disease stage-dependent.

The Alzheimer's Disease Assessment Scale-Cognitive Subscale (ADAS-Cog): Modifications and Responsiveness in Pre-Dementia Populations. A Narrative Review

The Alzheimer’s Disease Assessment Scale–Cognitive Subscale (ADAS-Cog) was developed in the 1980s to assess the level of cognitive dysfunction in Alzheimer’s disease. Advancements in the research field have shifted focus toward pre-dementia populations, and use of the ADAS-Cog has extended into these pre-dementia studies despite concerns about its ability to detect important changes at these milder stages of disease progression. If the ADAS-Cog cannot detect important changes, our understanding of pre-dementia disease progression may be compromised and trials may incorrectly conclude that a novel treatment approach is not beneficial. The purpose of this review was to assess the performance of the ADAS-Cog in pre-dementia populations, and to review all modifications that have been made to the ADAS-Cog to improve its measurement performance in dementia or pre-dementia populations. The contents of this review are based on bibliographic searches of electronic databases to locate all studies using the ADAS-Cog in pre-dementia samples or subsamples, and to locate all modified versions. Citations from relevant articles were also consulted. Overall, our results suggest the original ADAS-Cog is not an optimal outcome measure for pre-dementia studies; however, given the prominence of the ADAS-Cog, care must be taken when considering the use of alternative outcome measures. Thirty-one modified versions of the ADAS-Cog were found. Modification approaches that appear most beneficial include altering scoring methodology or adding tests of memory, executive function, and/or daily functioning. Although modifications improve the performance of the ADAS-Cog, this is at the cost of introducing heterogeneity that may limit between-study comparison.

Formaldehyde, Epigenetics, and Alzheimer's Disease

Alzheimer's disease (AD) is the most common form of dementia. The accumulation of β-amyloid plaques and intracellular neurofibrillary tangles of hyperphosphorylated tau protein are two hallmarks of AD. The β-amyloid and tau proteins have been at the center of AD research and drug development for decades. However, most of the clinical trials targeting β-amyloid have failed. Whereas the safety and efficacy of most tau-targeting drugs have not yet been completely assessed, the first tau aggregation inhibitor, LMTX, failed in a late-stage trial, leading to further recognition of the complexities of AD and reconsideration of the amyloid hypothesis and perhaps the tau hypothesis as well. Multilevel complex interactions between genetic, epigenetic, and environmental factors contribute to the occurrence and progression of AD. Formaldehyde (FA) is a widespread environmental organic pollutant. It is also an endogenous metabolite in the human body. Recent studies suggest that elevation of FA in the body by endogenous and/or exogenous exposure may play important roles in AD development. We have demonstrated that FA reduces lysine acetylation of cytosolic histones, thereby compromising chromatin assembly and resulting in the loss of histone content in chromatin, a conserved feature of aging from yeast to humans. Aging is an important factor for AD progression. Therefore, FA-induced inhibition of chromatin assembly and the loss of histones may contribute to AD initiation and/or development. This review will briefly summarize current knowledge on mechanistic insights into AD, focusing on epigenetic alterations and the involvement of FA in AD development. The exploration of chemical exposures as contributing factors to AD may provide new insights into AD mechanisms and could identify potential novel therapeutic targets.

Reconsideration of Anticholinesterase Therapeutic Strategies against Alzheimer's Disease

Alzheimer's disease (AD) is well-known as a severe neurodegeneration disease involving complicated etiologies, and cholinesterase inhibition remain the prevailing mode of clinical intervention in AD management. Although most clinically applied cholinesterase inhibitors (ChEIs) achieve limited clinical outcomes, research on the central cholinergic system is still thriving. Recently, an impressive amount of knowledge regarding novel acetylcholinesterase functions, as well as the close association between the central cholinergic system and other key elements for AD pathogenesis, has accumulated, highlighting that this field still has great potential for future drug development. In contrast to the overwhelmingly disappointing clinical therapeutic effects of various disease-modifying drug candidates, interesting evidence has continued to emerge over the past 20 years from the wealth of preclinical and clinical data on the usage of ChEIs, indicating underestimated clinical benefits due to physician ambivalence, a lack of persistent treatment, and inappropriate medication times or doses. Here we pinpoint several topics fit for future attention, focusing on the updated cholinergic hypothesis, especially the pleiotropic relationships with key pathogenetic signaling pathways and functions in AD, as well as possible novel therapeutic strategies, including novel ChEIs and cholinesterase inhibition-based innovative multifunctional therapeutic candidates. We intend to strengthen the future value of the precise application of cholinergic drugs, especially novel ChEIs, as a cornerstone pharmacological approach to AD treatment, either alone or in combination with other targets, to relieve symptoms and to modify disease progression.

The clinical significance of plasma clusterin and Aβ in the longitudinal follow-up of patients with Alzheimer's disease

Background

Clusterin and beta-amyloid (Aβ) are involved in the pathogenesis of Alzheimer’s disease (AD). The clinical significance of plasma clusterin and Aβ in AD progression remains controversial.

Methods

We recruited 322 patients with AD and 88 controls between August 2012 and June 2013. All participants were evaluated at baseline with a clinical assessment, Mini-Mental State Examination (MMSE), and Clinical Dementia Rating (CDR) scales. Patients with AD were evaluated annually with the MMSE and Neuropsychiatric Inventory (NPI) scale during the 2-year follow-up period. The levels of plasma clusterin, Aβ1–40, and Aβ1–42 at baseline were analyzed to study the longitudinal changes in the patient scores on the MMSE and NPI during the follow-up period.

Results

Patients in the highest tertile of plasma clusterin levels showed significantly lower MMSE scores than those in the lowest tertile (p = 0.04). After adjustment for multiple covariates using the generalized estimating equation analysis, there was a significant decrease in the MMSE scores over the 2-year follow-up period among AD patients in the highest tertile of plasma clusterin levels compared with those in the lowest tertile (−2.09, 95% confidence interval (CI) = −3.67 to −0.51, p = 0.01). In apolipoprotein E (ApoE)4-positive AD patients, baseline measurements of the ratio of plasma Aβ1–42/Aβ1–40 in the highest tertile predicted an increase in NPI agitation/aggression scores over the 2-year follow-up period (6.06, 95% CI = 1.20–10.62, p = 0.02).

Conclusions

Plasma clusterin could serve as a biomarker for the severity of cognitive decline. Plasma Aβ in ApoE4-positive AD could predict long-term agitation/aggression symptoms.

Adverse Effects of the Apolipoprotein E ε4 Allele on Episodic Memory, Task Switching and Gray Matter Volume in Healthy Young Adults

Many studies have shown that healthy elderly subjects and patients with Alzheimer’s disease (AD) who carry the apolipoprotein E (ApoE) ε4 allele have worse cognitive function and more severe brain atrophy than non-carriers. However, it remains unclear whether this ApoE polymorphism leads to changes of cognition and brain morphology in healthy young adults. In this study, we used an established model to measure verbal episodic memory and core executive function (EF) components (response inhibition, working memory and task switching) in 32 ApoE ε4 carriers and 40 non-carriers between 20 years and 40 years of age. To do this, we carried out an adapted auditory verbal learning test and three computerized EF tasks. High-resolution head magnetic resonance scans were performed in all participants and voxel-based morphometry (VBM) was used for image processing and analysis. Multivariate analysis of variance (ANOVA) performed on memory measures showed that the overall verbal episodic memory of ApoE ε4 carriers was significantly worse than non-carriers (Wilk’s λ = 4.884, P = 0.004). No significant differences were detected in overall EF between the two groups. Post hoc analyses revealed group differences in terms of immediate recall, recognition and task switching, which favored non-carriers. VBM analysis showed gray matter (GM) bilateral reductions in the medial and dorsolateral frontal, parietal and left temporal cortices in the carrier group relative to the non-carrier group, which were most significant in the bilateral anterior and middle cingulate gyri. However, these changes in GM volume were not directly associated with changes in cognitive function. Our data show that the ApoE ε4 allele is associated with poorer performance in verbal episodic memory and task switching, and a reduction in GM volume in healthy young adults, suggesting that the effects of ApoE ε4 upon cognition and brain morphology exist long before the possible occurrence of AD.

Six psychotropics for pre-symptomatic & early Alzheimer's (MCI), Parkinson's, and Huntington's disease modification

The quest for neuroprotective drugs to slow the progression of neurodegenerative diseases (NDDs), including Alzheimer's disease (AD), Parkinson's disease (PD), and Huntington's disease (HD), has been largely unrewarding. Preclinical evidence suggests that repurposing quetiapine, lithium, valproate, fluoxetine, donepezil, and memantine for early and pre-symptomatic disease-modification in NDDs may be promising and can spare regulatory barriers. The literature of these psychotropics in early stage and pre-symptomatic AD, PD, and HD is reviewed and propitious findings follow. Mild cognitive impairment (MCI) phase of AD: salutary human randomized controlled trial findings for low-dose lithium and, in selected patients, donepezil await replication. Pre-symptomatic AD: human epidemiological data indicate that lithium reduces AD risk. Animal model studies (AMS) reveal encouraging results for quetiapine, lithium, donepezil, and memantine. Early PD: valproate AMS findings show promise. Pre-symptomatic PD: lithium and valproate AMS findings are encouraging. Early HD: uncontrolled clinical data indicate non-progression with lithium, fluoxetine, donepezil, and memantine. Pre-symptomatic HD: lithium and valproate are auspicious in AMS. Many other promising findings awaiting replication (valproate in MCI; lithium, valproate, fluoxetine in pre-symptomatic AD; lithium in early PD; lithium, valproate, fluoxetine in pre-symptomatic PD; donepezil in early HD; lithium, fluoxetine, memantine in pre-symptomatic HD) are reviewed. Dose- and stage-dependent effects are considered. Suggestions for signal-enhancement in human trials are provided for each NDD stage.