Review of the advances in treatment for Alzheimer disease: strategies for combating β-amyloid protein

Sleep duration, sleep efficiency, and amyloid β among cognitively healthy later-life adults: a systematic review and meta-analysis

BACKGROUND

Abnormal amyloid β (Aβ) deposits in the brain are a hallmark of Alzheimer's disease (AD). Insufficient sleep duration and poor sleep quality are risk factors for developing AD. Sleep may play a role in Aβ regulation, but the magnitude of the relationship between sleep and Aβ deposition remains unclear. This systematic review examines the relationship between sleep (i.e., duration and efficiency) with Aβ deposition in later-life adults.

METHODS

A search of PubMed, CINAHL, Embase, and PsycINFO generated 5,005 published articles. Fifteen studies met the inclusion criteria for qualitative syntheses; thirteen studies for quantitative syntheses related to sleep duration and Aβ; and nine studies for quantitative syntheses related to sleep efficiency and Aβ.

RESULTS

Mean ages of the samples ranged from 63 to 76 years. Studies measured Aβ using cerebrospinal fluid, serum, and positron emission tomography scans with two tracers: Carbone 11-labeled Pittsburgh compound B or fluorine 18-labeled. Sleep duration was measured subjectively using interviews or questionnaires, or objectively using polysomnography or actigraphy. Study analyses accounted for demographic and lifestyle factors. Based on 13 eligible articles, our synthesis demonstrated that the average association between sleep duration and Aβ was not statistically significant (Fisher's Z = -0.055, 95% CI = -0.117 ~ 0.008). We found that longer self-report sleep duration is associated with lower Aβ (Fisher's Z = -0.062, 95% CI = -0.119 ~ -0.005), whereas the objectively measured sleep duration was not associated with Aβ (Fisher's Z = 0.002, 95% CI = -0.108 ~ 0.113). Based on 9 eligible articles for sleep efficiency, our synthesis also demonstrated that the average association between sleep efficiency and Aβ was not statistically significant (Fisher's Z = 0.048, 95% CI = -0.066 ~ 0.161).

CONCLUSION

The findings from this review suggest that shorter self-reported sleep duration is associated with higher Aβ levels. Given the heterogeneous nature of the sleep measures and outcomes, it is still difficult to determine the exact relationship between sleep and Aβ. Future studies with larger sample sizes should focus on comprehensive sleep characteristics and use longitudinal designs to better understand the relationship between sleep and AD.

Targets, trials and tribulations in Alzheimer therapeutics

Alzheimer's disease (AD) is a progressive neurodegenerative disorder characterized by abnormal accumulation of extracellular amyloid beta senile plaques and intracellular neurofibrillary tangles in the parts of the brain responsible for cognition. The therapeutic burden for the management of AD relies solely on cholinesterase inhibitors that provide only symptomatic relief. The urgent need for disease-modifying drugs has resulted in intensive research in this domain, which has led to better understanding of the disease pathology and identification of a plethora of new pathological targets. Currently, there are over a hundred and seventy clinical trials exploring disease modification, cognitive enhancement, and reduction of neuro-psychiatric complications. However, the path to developing safe and efficacious AD therapeutics has not been without challenges. Several clinical trials have been terminated in advanced stages due to lack of therapeutic translation or increased incidence of adverse events. This review presents an in-depth look at the various therapeutic targets of AD and the lessons learnt during their clinical assessment. Comprehensive understanding of the implication of modulating various aspects of Alzheimer brain pathology is crucial for development of drugs with potential to halt disease progression in Alzheimer therapeutics.

Acousto-optic stimuli to promote coherent 40-Hz frequency entrainment effect

BACKGROUND

 Research has shown that a fundamental frequency of 40 Hz in continuous neural oscillation is indicative of normal brain activity; in Alzheimer disease (AD) patients, these oscillations either disappear or are significantly interrupted. Research has also indicated that the degenerative impacts of AD in mice were mitigated by the synchronization of 40-Hz acousto-optic stimulation (AOS).

OBJECTIVE

 To examine the impact of employing a 40-Hz AOS intervention on the induction of a substantial 40-Hz frequency entrainment and improvement in working memory performance among a sample of young individuals in good health. We conduct an analysis of event-related potentials (ERPs) derived from electroencephalogram (EEG) data following the presentation of AOS.

METHODS

 We recruited 20 healthy volunteers (median age: 25 years; 8 female subjects). Following the administration of various stimuli, including no stimuli, 40-Hz AOS, pink noise, and 40Hz acoustic stimuli (AS), the participants were required to complete a working memory task. A total of 62 electrodes were used to record EEG data, which was subsequently analyzed to investigate the impact of AOS on the activity of working memory. We also aimed to determine if AOS lead to a more pronounced 40-Hz frequency entrainment.

RESULTS

 Following the administration of AOS, a notable enhancement in the 40-Hz power of pertinent cerebral areas was observed, accompanied by a substantial improvement in the performance of the subjects on working memory tests subsequent to the stimulation.

CONCLUSION

 The findings unequivocally establish the efficacy of using AOS to enhance the 40-Hz power and working memory.

Alzheimer's Disease: Innovative Therapeutic Approaches Based on Peptides and Nanoparticles

Alzheimer's disease (AD) is the main cause of dementia in the world and its etiology is not yet fully understood. The pathology of AD is primarily characterized by intracellular neurofibrillary tangles and extracellular amyloid-β plaques. Unfortunately, few treatment options are available, and most treat symptoms, as is the case of acetylcholinesterase inhibitors (IAChE) and N-methyl-d-aspartate receptor antagonists. For more than 20 years pharmaceutical research has targeted the "amyloid cascade hypothesis," but this has not produced meaningful results, leading researchers to focus now on other characteristics of the disease and on multitarget approaches. This review aims to evaluate some new treatments that are being developed and studied. Among these are new treatments based on peptides, which have high selectivity and low toxicity; however, these compounds have a short half-life and encounter challenges when crossing the blood-brain barrier. The present review discusses up-and-coming peptides tested as treatments and explores some nanotechnological strategies to overcome the downsides. These compounds are promising, as they not only act on the symptoms but also aim to prevent progressive neuronal loss.

Dietary polyphenols and their relationship to the modulation of non-communicable chronic diseases and epigenetic mechanisms: A mini-review

Chronic Non-Communicable Diseases (NCDs) have been considered a global health problem, characterized as diseases of multiple factors, which are developed throughout life, and regardless of genetics as a risk factor of important relevance, the increase in mortality attributed to the disease to environmental factors and the lifestyle one leads. Although the reactive species (ROS/RNS) are necessary for several physiological processes, their overproduction is directly related to the pathogenesis and aggravation of NCDs. In contrast, dietary polyphenols have been widely associated with minimizing oxidative stress and inflammation. In addition to their antioxidant power, polyphenols have also drawn attention for being able to modulate both gene expression and modify epigenetic alterations, suggesting an essential involvement in the prevention and/or development of some pathologies. Therefore, this review briefly explained the mechanisms in the development of some NCDs, followed by a summary of some evidence related to the interaction of polyphenols in oxidative stress, as well as the modulation of epigenetic mechanisms involved in the management of NCDs.

Linking the Amyloid, Tau, and Mitochondrial Hypotheses of Alzheimer's Disease and Identifying Promising Drug Targets

Damage or loss of brain cells and impaired neurochemistry, neurogenesis, and synaptic and nonsynaptic plasticity of the brain lead to dementia in neurodegenerative diseases, such as Alzheimer's disease (AD). Injury to synapses and neurons and accumulation of extracellular amyloid plaques and intracellular neurofibrillary tangles are considered the main morphological and neuropathological features of AD. Age, genetic and epigenetic factors, environmental stressors, and lifestyle contribute to the risk of AD onset and progression. These risk factors are associated with structural and functional changes in the brain, leading to cognitive decline. Biomarkers of AD reflect or cause specific changes in brain function, especially changes in pathways associated with neurotransmission, neuroinflammation, bioenergetics, apoptosis, and oxidative and nitrosative stress. Even in the initial stages, AD is associated with Aβ neurotoxicity, mitochondrial dysfunction, and tau neurotoxicity. The integrative amyloid-tau-mitochondrial hypothesis assumes that the primary cause of AD is the neurotoxicity of Aβ oligomers and tau oligomers, mitochondrial dysfunction, and their mutual synergy. For the development of new efficient AD drugs, targeting the elimination of neurotoxicity, mutual potentiation of effects, and unwanted protein interactions of risk factors and biomarkers (mainly Aβ oligomers, tau oligomers, and mitochondrial dysfunction) in the early stage of the disease seems promising.

Nanoparticles in Combating Neuronal Dysregulated Signaling Pathways: Recent Approaches to the Nanoformulations of Phytochemicals and Synthetic Drugs Against Neurodegenerative Diseases

As the worldwide average life expectancy has grown, the prevalence of age-related neurodegenerative diseases (NDDs) has risen dramatically. A progressive loss of neuronal function characterizes NDDs, usually followed by neuronal death. Inflammation, apoptosis, oxidative stress, and protein misfolding are critical dysregulated signaling pathways that mainly orchestrate neuronal damage from a mechanistic point. Furthermore, in afflicted families with genetic anomalies, mutations and multiplications of α-synuclein and amyloid-related genes produce some kinds of NDDs. Overproduction of such proteins, and their excessive aggregation, have been proven in various models of neuronal malfunction and death. In this line, providing multi-target therapies carried by novel delivery systems would pave the road to control NDDs through simultaneous modulation of such dysregulated pathways. Phytochemicals are multi-target therapeutic agents, which employ several mechanisms towards neuroprotection. Besides, the blood-brain barrier (BBB) is a critical issue in managing NDDs since it inhibits the accessibility of drugs to the brain in sufficient concentration. Besides, discovering novel delivery systems is vital to improving the efficacy, bioavailability, and pharmacokinetic of therapeutic agents. Such novel formulations are also employed to improve the drug's biodistribution, allow for the co-delivery of several medicines, and offer targeted intracellular delivery against NDDs. The present review proposes nanoformulations of phytochemicals and synthetic agents to combat NDDs by modulating neuroinflammation, neuroapoptosis, neuronal oxidative stress pathways and protein misfolding.

A Revisit to Etiopathogenesis and Therapeutic Strategies in Alzheimer's Disease

Dementia is a cluster of brain abnormalities that trigger progressive memory deficits and other cognitive abilities such as skills, language, or executive function. Alzheimer's disease (AD) is the foremost type of age-associated dementia that involves progressive neurodegeneration accompanied by profound cognitive deficits in advanced stages that severely hamper social or occupational abilities with or without the involvement of any other psychiatric condition. The last two decades witnessed a sharp increase (~123%) in mortality due to AD type dementia, typically owing to a very low disclosure rate (~45%) and hence, the prophylactic, as well as the therapeutic cure of AD, has been a huge challenge. Although understanding of AD pathogenesis has witnessed a remarkable growth (e.g., tauopathy, oxidative stress, lipid transport, glucose uptake, apoptosis, synaptic dysfunction, inflammation, and immune system), still a dearth of an effective therapeutic agent in the management of AD prompts the quest for newer pharmacological targets in the purview of its growing epidemiological status. Most of the current therapeutic strategies focus on modulation of a single target, e.g., inhibition of acetylcholinesterase, glutamate excitotoxicity (memantine), or nootropics (piracetam), even though AD is a multifaceted neurological disorder. There is an impedance urgency to find not only symptomatic but effective disease-modifying therapies. The present review focuses on the risk / protective factors and pathogenic mechanisms involved in AD. In addition to the existing symptomatic therapeutic approach, a diverse array of possible targets linked to pathogenic cascades have been re-investigated to envisage the pharmacotherapeutic strategies in AD.

Unraveling the Speciation of β-Amyloid Peptides during the Aggregation Process by Taylor Dispersion Analysis

Aggregation mechanisms of amyloid β peptides depend on multiple intrinsic and extrinsic physicochemical factors (e.g., peptide chain length, truncation, peptide concentration, pH, ionic strength, temperature, metal concentration, etc.). Due to this high number of parameters, the formation of oligomers and their propensity to aggregate make the elucidation of this physiopathological mechanism a challenging task. From the analytical point of view, up to our knowledge, few techniques are able to quantify, in real time, the proportion and the size of the different soluble species during the aggregation process. This work aims at demonstrating the efficacy of the modern Taylor dispersion analysis (TDA) performed in capillaries (50 μm i.d.) to unravel the speciation of β-amyloid peptides in low-volume peptide samples (∼100 μL) with an analysis time of ∼3 min per run. TDA was applied to study the aggregation process of Aβ(1-40) and Aβ(1-42) peptides at physiological pH and temperature, where more than 140 data points were generated with a total volume of ∼1 μL over the whole aggregation study (about 0.5 μg of peptides). TDA was able to give a complete and quantitative picture of the Aβ speciation during the aggregation process, including the sizing of the oligomers and protofibrils, the consumption of the monomer, and the quantification of different early- and late-formed aggregated species.

Journey on Naphthoquinone and Anthraquinone Derivatives: New Insights in Alzheimer's Disease

Alzheimer's disease (AD) is a progressive neurodegenerative disease that is characterized by memory loss, cognitive impairment, and functional decline leading to dementia and death. AD imposes neuronal death by the intricate interplay of different neurochemical factors, which continue to inspire the medicinal chemist as molecular targets for the development of new agents for the treatment of AD with diverse mechanisms of action, but also depict a more complex AD scenario. Within the wide variety of reported molecules, this review summarizes and offers a global overview of recent advancements on naphthoquinone (NQ) and anthraquinone (AQ) derivatives whose more relevant chemical features and structure-activity relationship studies will be discussed with a view to providing the perspective for the design of viable drugs for the treatment of AD. In particular, cholinesterases (ChEs), β-amyloid (Aβ) and tau proteins have been identified as key targets of these classes of compounds, where the NQ or AQ scaffold may contribute to the biological effect against AD as main unit or significant substructure. The multitarget directed ligand (MTDL) strategy will be described, as a chance for these molecules to exhibit significant potential on the road to therapeutics for AD.

Survival Analysis of Patients with Alzheimer's Disease: A Study Based on Data from the Korean National Health Insurance Services' Senior Cohort Database

BACKGROUND

Korea's rapidly aging population has experienced a sharp rise in the prevalence of dementia. Patients with Alzheimer's disease (AD), which is estimated to be about three-quarters of all patients with dementia, tend to have higher mortality rates compared with patients without Alzheimer's disease. In this study, a survival analysis of patients with AD was conducted in order to provide knowledge to those who provide medical care to these patients.

METHODS

Data on individuals over 65 years old in 2004 were extracted from the Korean National Health Insurance Services' Senior Cohort database (2002-2013). The subjects were 209,254 patients, including 2,695 who were first diagnosed with AD (the AD group) and 206,559 that had not been diagnosed with the disease (non-AD group). To investigate the independent effect of AD on survival, the Cox proportional-hazards model, hazard ratios (confidence interval of 95%), and the Kaplan-Meier method were used.

RESULTS

Mean survival time in the AD group was 5.3±3.3 years, which was about 2.5 years shorter than that in the non-AD group (7.8±2.4 years). The mortality rate in the AD group (66.3%) was higher than that in the non-AD group (26.3%). The adjusted hazard ratio in the AD group was 2.5 and, therefore, it was found that the AD group had a 2.5-fold higher risk of death than the non-AD group.

CONCLUSION

Overall, AD has a large, independent impact on survival. Survival time was shorter, and the mortality rate and risk were generally higher in the AD group, compared with the non-AD group.

Pharmacotherapy of Alzheimer's Disease: Seeking Clarity in a Time of Uncertainty

Alzheimer's disease (AD) is recognized as a major health hazard that mostly affects people older than 60 years. AD is one of the biggest medical, economic, and social concerns to patients and their caregivers. AD was ranked as the 5th leading cause of global deaths in 2016 by the World Health Organization (WHO). Many drugs targeting the production, aggregation, and clearance of Aβ plaques failed to give any conclusive clinical outcomes. This mainly stems from the fact that AD is not a disease attributed to a single-gene mutation. Two hallmarks of AD, Aβ plaques and neurofibrillary tangles (NFTs), can simultaneously induce other AD etiologies where every pathway is a loop of consequential events. Therefore, the focus of recent AD research has shifted to exploring other etiologies, such as neuroinflammation and central hyperexcitability. Neuroinflammation results from the hyperactivation of microglia and astrocytes that release pro-inflammatory cytokines due to the neurological insults caused by Aβ plaques and NFTs, eventually leading to synaptic dysfunction and neuronal death. This review will report the failures and side effects of many anti-Aβ drugs. In addition, emerging treatments targeting neuroinflammation in AD, such as nonsteroidal anti-inflammatory drugs (NSAIDs) and receptor-interacting serine/threonine protein kinase 1 (RIPK1), that restore calcium dyshomeostasis and microglia physiological function in clearing Aβ plaques, respectively, will be deliberately discussed. Other novel pharmacotherapy strategies in treating AD, including disease-modifying agents (DMTs), repurposing of medications used to treat non-AD illnesses, and multi target-directed ligands (MTDLs) are also reviewed. These approaches open new doors to the development of AD therapy, especially combination therapy that can cater for several targets simultaneously, hence effectively slowing or stopping AD.