The genetics of Alzheimer's disease

Structural insights into human ABCA7-mediated lipid transport

The human ATP-binding cassette (ABC) transporter ABCA7 participates in the lipidation of apolipoprotein ApoE, a commonly recognized risk factor for Alzheimer's disease (AD). How ABCA7 is involved in the molecular pathogenesis of AD remains poorly understood. Using cryoelectron microscopy (cryo-EM), we determined ABCA7 structures in the apo and substrate-bound forms, respectively. Combined with activity assays, we assigned the residues that specifically bind two molecules of phosphatidylserine (PS) that are arranged in a "tail-to-tail" manner. Pull-down assays confirmed that ApoE directly interacts with ABCA7; and moreover, both ATPase and lipid transport activities of ABCA7 were significantly enhanced in the presence of ApoE. We also measured the activities of a familial AD variant and a protective clinically reported variant in the ABCA7 gene. Our findings not only give structural insights into ABCA7-mediated PS translocation, but we also provide first biochemical evidence for its link to AD by forwarding lipids to ApoE.

1H NMR-Based Metabolomic Signatures in Rodent Models of Sporadic Alzheimer's Disease and Metabolic Disorders

Alzheimer's disease (AD) is a chronic neurological disorder that impacts the elderly population all over the globe. Evidence suggests association between AD and metabolic disorders such as diabetes mellitus (DM) and obesity (OB). The present study is an attempt to evaluate metabolic alterations in the serum and brain through NMR spectroscopy with the aim to identify shared metabolic signatures. AD was induced in rats by stereotactic intracerebroventricular injection of oligomerized Aβ-42 peptide into the brain. DM and OB were induced by intraperitoneal injection of streptozotocin and feeding rats on a high-fat diet, respectively. The metabolic alterations obtained through 1H NMR spectroscopy were further subjected to multivariate analysis by principal component analysis and partial least-squares discrimination for identification of metabolic signatures. In the serum, the levels of lactate and betaine were increased in AD, DM, and OB rats. On the other hand, the metabolite profile of brain indicated increase in the levels of lactate, N-acetylaspartate, and creatinine in AD, DM, and OB rats. Additionally, the concentration of neurochemicals such as glutamate, GABA, N-acetylglutamate, and myo-inositol were also elevated. The alterations in neurotransmitters and cerebral energy metabolism were accompanied by deficits in cognition assessed by Morris water maze in AD, DM, and OB rats. The perturbed metabolic profiles were accompanied by the presence of pathogenic amyloid deposits visualized by Congo red stain in the brains of AD, DM, and OB rats. Overall, the study identifies common metabolic signatures in AD, DM, and OB that may be involved in etiopathogenesis and also suggests linkages between these three conditions.

Identification of novel risk genes for Alzheimer's disease by integrating genetics from hippocampus

Alzheimer's disease (AD) stands as the most prevalent neurodegenerative ailment, presently lacking a definitive cure. Given that primary medications for AD patients in the early or middle stages demonstrate optimal efficacy, it becomes crucial to delve into the identification of risk genes associated with early onset. In our study, we compiled and integrated three transcriptomics datasets (GSE48350, GSE36980, GSE5281) originating from the hippocampus of 37 AD patients and 66 healthy controls (CTR) for comprehensive bioinformatics analysis. Comparative analysis with CTR revealed 25 up-regulated genes and 291 down-regulated genes in AD. Those down-regulated genes were notably enriched in processes related to the transmission and transport of synaptic signals. Intriguingly, 27 differentially expressed genes implicated in AD were also correlated with the Braak stage, establishing a connection with various immune cell types that exhibit differences in AD, including cytotoxic T cells, neutrophils, CD4 T cells, Th1, Th2, and Tfh. Significantly, a Cox model, constructed using nine feature genes, effectively stratified AD samples (HR = 2.72, 95% CI 1.94 ~ 3.81, P = 3.6e-10), highlighting their promising potential for risk assessment. In conclusion, our investigation sheds light on novel genes intricately linked to the onset and progression of AD, offering potential biomarkers for the early detection of this debilitating condition. This study contributes valuable insights toward enhancing the strategies for preventing and treating AD.

Pharmacological inhibition of PLK2 kinase activity mitigates cognitive decline but aggravates APP pathology in a sex-dependent manner in APP/PS1 mouse model of Alzheimer's disease

Converging evidence from clinical and experimental studies suggest the potential significance of Polo-like kinase 2 (PLK2) in regulating the phosphorylation and toxicity of the Alzheimer's disease (AD)-related protein, amyloid precursor protein (APP). These findings have prompted various experimental trials aimed at inhibiting PLK2 kinase activity in different transgenic mouse models of AD. While positive impacts on cognitive decline were reported in these studies, the cellular effects remained controversial. In the present study, we sought to assess the cognitive and cellular consequences of chronic PLK2 inhibitor treatment in the APP/PS1 transgenic mouse model of AD. First, we confirmed that inhibiting PLK2 prevented cognitive decline in a sex-dependent manner, particularly by enhancing working memory in male APP/PS1 mice. Surprisingly, cellular analysis revealed that treatment with PLK2 inhibitor increased the load of amyloid plaques and elevated levels of soluble amyloid β (Aβ) 40 and Aβ42 in the cortex, as well as insoluble Aβ42 in the hippocampus of female mice, without affecting APP pathology in males. These results underscore the potential of PLK2 inhibition to mitigate cognitive symptoms in males. However, paradoxically, it intensifies amyloid pathology in females by enhancing APP amyloidogenic processing, creating a controversial aspect to its therapeutic impact. Overall, these data highlight the sex-dependent nature of the effects of PLK2 inhibition, which may also be influenced by the genetic background of the transgenic mouse model utilized.

Mechanistic Approach to Immunity and Immunotherapy of Alzheimer's Disease: A Review

Alzheimer's disease (AD) is a debilitating neurodegenerative condition characterized by progressive cognitive decline and memory loss, affecting millions of people worldwide. Traditional treatments, such as cholinesterase inhibitors and NMDA receptor antagonists, offer limited symptomatic relief without addressing the underlying disease mechanisms. These limitations have driven the development of more potent and effective therapies. Recent advances in immunotherapy present promising avenues for AD treatment. Immunotherapy strategies, including both active and passive approaches, harness the immune system to target and mitigate AD-related pathology. Active immunotherapy stimulates the patient's immune response to produce antibodies against AD-specific antigens, while passive immunotherapy involves administering preformed antibodies or immune cells that specifically target amyloid-β (Aβ) or tau proteins. Monoclonal antibodies, such as aducanumab and lecanemab, have shown potential in reducing Aβ plaques and slowing cognitive decline in clinical trials, despite challenges related to adverse immune responses and the need for precise targeting. This comprehensive review explores the role of the immune system in AD, evaluates the current successes and limitations of immunotherapeutic approaches, and discusses future directions for enhancing the treatment efficacy.

Rodent Models of Alzheimer's Disease: Past Misconceptions and Future Prospects

Alzheimer's disease (AD) is a progressive neurodegenerative disease with no effective treatments, not least due to the lack of authentic animal models. Typically, rodent models recapitulate the effects but not causes of AD, such as cholinergic neuron loss: lesioning of cholinergic neurons mimics the cognitive decline reminiscent of AD but not its neuropathology. Alternative models rely on the overexpression of genes associated with familial AD, such as amyloid precursor protein, or have genetically amplified expression of mutant tau. Yet transgenic rodent models poorly replicate the neuropathogenesis and protein overexpression patterns of sporadic AD. Seeding rodents with amyloid or tau facilitates the formation of these pathologies but cannot account for their initial accumulation. Intracerebral infusion of proinflammatory agents offer an alternative model, but these fail to replicate the cause of AD. A novel model is therefore needed, perhaps similar to those used for Parkinson's disease, namely adult wildtype rodents with neuron-specific (dopaminergic) lesions within the same vulnerable brainstem nuclei, 'the isodendritic core', which are the first to degenerate in AD. Site-selective targeting of these nuclei in adult rodents may recapitulate the initial neurodegenerative processes in AD to faithfully mimic its pathogenesis and progression, ultimately leading to presymptomatic biomarkers and preventative therapies.

Therapeutic implications of glycogen synthase kinase-3β in Alzheimer's disease: a novel therapeutic target

Alzheimer's disease (AD) is an extremely popular neurodegenerative condition associated with dementia, responsible for around 70% of the cases. There are presently 50 million people living with dementia in the world, but this number is anticipated to increase to 152 million by 2050, posing a substantial socioeconomic encumbrance. Despite extensive research, the precise mechanisms that cause AD remain unidentified, and currently, no therapy is available. Numerous signalling paths related to AD neuropathology, including glycogen synthase kinase 3-β (GSK-3β), have been investigated as potential targets for the treatment of AD in current years.GSK-3β is a proline-directed serine/threonine kinase that is linked to a variety of biological activities, comprising glycogen metabolism to gene transcription. GSK-3β is also involved in the pathophysiology of sporadic as well as familial types of AD, which has led to the development of the GSK3 theory of AD. GSK-3β is a critical performer in the pathology of AD because dysregulation of this kinase affects all the main symbols of the disease such as amyloid formation, tau phosphorylation, neurogenesis and synaptic and memory function. The current review highlights present-day knowledge of GSK-3β-related neurobiology, focusing on its role in AD pathogenesis signalling pathways. It also explores the possibility of targeting GSK-3β for the management of AD and offers an overview of the present research work in preclinical and clinical studies to produce GSK-3β inhibitors.

Impaired Skeletal Development by Disruption of Presenilin-1 in Pigs and Generation of Novel Pig Models for Alzheimer's Disease

Background

Presenilin 1 (PSEN1) is one of the genes linked to the prevalence of early onset Alzheimer's disease. In mice, inactivation of Psen1 leads to developmental defects, including vertebral malformation and neural development. However, little is known about the role of PSEN1 during the development in other species.

Objective

To investigate the role of PSEN1 in vertebral development and the pathogenic mechanism of neurodegeneration using a pig model.

Methods

CRISPR/Cas9 system was used to generate pigs with different mutations flanking exon 9 of PSEN1, including those with a deleted exon 9 (Δexon9). Vertebral malformations in PSEN1 mutant pigs were examined by X-ray, micro-CT and micro-MRI. Neuronal cells from the brains of PSEN1 mutant pigs were analyzed by immunoflourescence, followed by image analysis including morphometric evaluation via image J and 3D reconstruction.

Results

Pigs with a PSEN1 null mutation (Δexon9-12) died shortly after birth and had significant axial skeletal defects, whereas pigs carrying at least one Δexon9 allele developed normally and remained healthy. Effects of the null mutation on abnormal skeletal development were also observed in fetuses at day 40 of gestation. Abnormal distribution of astrocytes and microglia in the brain was detected in two PSEN1 mutant pigs examined compared to age-matched control pigs. The founder pigs were bred to establish and age PSEN1ΔE9/+ pigs to study their relevance to clinical Alzheimer's diseases.

Conclusions

PSEN1 has a critical role for normal vertebral development and PSEN1 mutant pigs serves as novel resources to study Alzheimer's disease.

Altered Motor Activity Patterns within 10-Minute Timescale Predict Incident Clinical Alzheimer's Disease

Background

Fractal motor activity regulation (FMAR), characterized by self-similar temporal patterns in motor activity across timescales, is robust in healthy young humans but degrades with aging and in Alzheimer's disease (AD).

Objective

To determine the timescales where alterations of FMAR can best predict the clinical onset of AD.

Methods

FMAR was assessed from actigraphy at baseline in 1,077 participants who had annual follow-up clinical assessments for up to 15 years. Survival analysis combined with deep learning (DeepSurv) was used to examine how baseline FMAR at different timescales from 3 minutes up to 6 hours contributed differently to the risk for incident clinical AD.

Results

Clinical AD occurred in 270 participants during the follow-up. DeepSurv identified three potential regions of timescales in which FMAR alterations were significantly linked to the risk for clinical AD: <10, 20-40, and 100-200 minutes. Confirmed by the Cox and random survival forest models, the effect of FMAR alterations in the timescale of <10 minutes was the strongest, after adjusting for covariates.

Conclusions

Subtle changes in motor activity fluctuations predicted the clinical onset of AD, with the strongest association observed in activity fluctuations at timescales <10 minutes. These findings suggest that short actigraphy recordings may be used to assess the risk of AD.

An optimized method for PCR-based genotyping to detect human APOE polymorphisms

Background

Apolipoprotein E (APOE) is one of the most polymorphic genes at two single nucleotides (rs429358 and rs7412). The various isoforms of APOE have been associated with a variety of diseases, including neurodegenerative, type 2 diabetes, etc. Hence, predicting the APOE genotyping is critical for disease risk evaluation. The purpose of this study was to optimize the tetra amplification refractory mutation system (Tetra-ARMS) PCR method for the detection of APOE mutations.

Material and methods

Here, in our optimized Tetra-ARMS PCR method, different factors like cycle conditions, using HiFidelity enzyme instead of Taq polymerase and setting its best concentration, and the lack of using dimethylsulfoxide (DMSO) for amplifying the GC-regions were set up for all primer pairs. The sensitivity and accuracy were tested. For validation of the assay, the results were compared with known genotypes for the APOE gene that were previously obtained by two independent methods, RFLP and Chip-typing.

Results

Successful Tetra-ARMS PCR and genotyping are influenced by multiple factors. Our developed method enabled us to amplify the DNA fragment by 25 cycles without adding any hazardous reagent, like DMSO. Our findings showed 100 % accuracy and sensitivity of the optimized Tetra-ARMS PCR while both criteria were 95 % for RFLP and 100 % for the chip-typing method. In addition, our results showed 91 % and 100 % consistency with RFLP and chip typing methods, respectively.

Conclusions

Our current method is a simple and accurate approach for detecting APOE polymorphisms within a large sample size in a short time and can be performed even in low-tech laboratories.

Gamma-secretase modulators: a promising route for the treatment of Alzheimer's disease

Recent clinical data with three therapeutic anti-Aβ antibodies have demonstrated that removal of Aβ-amyloid plaques in early Alzheimer's disease (AD) can attenuate disease progression. This ground-breaking progress in AD medicine has validated both the amyloid cascade hypothesis and Aβ-amyloid as therapeutic targets. These results also strongly support therapeutic approaches that aim to reduce the production of amyloidogenic Aβ to prevent the formation of Aβ-pathology. One such strategy, so-called gamma-secretase modulators (GSM), has been thoroughly explored in preclinical settings but has yet to be fully tested in clinical trials. Recent scientific progress has shed new light on the role of Aβ in Alzheimer's disease and suggests that GSMs exhibit specific pharmacological features that hold great promise for the prevention and treatment of Alzheimer's disease. In this short review, we discuss the data that support why it is important to continue to progress in this class of compounds.

Antimutagenicity and Antioxidant Activity of Castanea sativa Mill. Bark Extract

Castanea sativa Mill. (Cs), a plant traditionally employed in nutrition and to treat various respiratory and gastrointestinal infections, possesses cancer chemopreventive characteristics. In particular, Cs bark extract previously demonstrated antiproliferative and pro-apoptotic activities against a leukemic lymphoblastic cell line. Starting from this evidence, the aim of this paper was to investigate the possibility to affect also the earlier phases of the carcinogenic process by evaluating Cs bark extract's antimutagenic properties, in particular using the "In Vitro Mammalian Cell Micronucleus Test" on TK6 cells performed by flow cytometry. For this purpose, since an ideal chemopreventive agent should be virtually nontoxic, the first step was to exclude the extract's genotoxicity. Afterwards, the antimutagenic effect of the extract was evaluated against two known mutagens, the clastogen mitomycin C (MMC) and the aneugen vinblastine (VINB). Our results indicate that Cs bark extract protected cells from MMC-induced damage (micronuclei frequency fold increase reduction from 2.9 to 1.8) but not from VINB. Moreover, we demonstrated that Cs bark extract was a strong antioxidant and significantly reduced MMC-induced ROS levels by over 2 fold. Overall, our research supports the assumption that Cs bark extract can counteract MMC mutagenicity by possibly scavenging ROS production.

Effect of apolipoprotein genotype and educational attainment on cognitive function in autosomal dominant Alzheimer's disease

Autosomal dominant Alzheimer's disease (ADAD) is genetically determined, but variability in age of symptom onset suggests additional factors may influence cognitive trajectories. Although apolipoprotein E (APOE) genotype and educational attainment both influence dementia onset in sporadic AD, evidence for these effects in ADAD is limited. To investigate the effects of APOE and educational attainment on age-related cognitive trajectories in ADAD, we analyzed data from 675 Presenilin-1 E280A mutation carriers and 594 non-carriers. Here we show that age-related cognitive decline is accelerated in ADAD mutation carriers who also have an APOE e4 allele compared to those who do not and delayed in mutation carriers who also have an APOE e2 allele compared to those who do not. Educational attainment is protective and moderates the effect of APOE on cognition. Despite ADAD mutation carriers being genetically determined to develop dementia, age-related cognitive decline may be influenced by other genetic and environmental factors.

Intervention of next-generation sequencing in diagnosis of Alzheimer's disease: challenges and future prospects

Clinical diagnosis of several neurodegenerative disorders based on clinical phenotype is challenging due to its heterogeneous nature and overlapping disease manifestations. Therefore, the identification of underlying genetic mechanisms is of paramount importance for better diagnosis and therapeutic regimens. With the emergence of next-generation sequencing, it becomes easier to identify all gene variants in the genome simultaneously, with a system-wide and unbiased approach. Presently various bioinformatics databases are maintained on discovered gene variants and phenotypic indications are available online. Since individuals are unique in their genome, evaluation based on their genetic makeup helps evolve the diagnosis, counselling, and treatment process at the personal level. This article aims to briefly summarize the utilization of next-generation sequencing in deciphering the genetic causes of Alzheimer's disease and address the limitations of whole genome and exome sequencing.

Dietary Patterns and Alzheimer's Disease: An Updated Review Linking Nutrition to Neuroscience

Alzheimer's disease (AD) is a growing concern for the aging population worldwide. With no current cure or reliable treatments available for AD, prevention is an important and growing area of research. A range of lifestyle and dietary patterns have been studied to identify the most effective preventive lifestyle changes against AD and related dementia (ADRD) pathology. Of these, the most studied dietary patterns are the Mediterranean, DASH, MIND, ketogenic, and modified Mediterranean-ketogenic diets. However, there are discrepancies in the reported benefits among studies examining these dietary patterns. We herein compile a narrative/literature review of existing clinical evidence on the association of these patterns with ADRD symptomology and contemplate their preventive/ameliorative effects on ADRD neuropathology in various clinical milieus. By and large, plant-based dietary patterns have been found to be relatively consistently and positively correlated with preventing and reducing the odds of ADRD. These impacts stem not only from the direct impact of specific dietary components within these patterns on the brain but also from indirect effects through decreasing the deleterious effects of ADRD risk factors, such as diabetes, obesity, and cardiovascular diseases. Importantly, other psychosocial factors influence dietary intake, such as the social connection, which may directly influence diet and lifestyle, thereby also impacting ADRD risk. To this end, prospective research on ADRD should include a holistic approach, including psychosocial considerations.

Barbigerone prevents scopolamine-induced memory impairment in rats by inhibiting oxidative stress and acetylcholinesterase levels

The current study was designed for the evaluation of barbigerone on memory loss. In this experimental study, 24 Wistar rats (n = 6) were used. Control rats and scopolamine (SCOP)-treated control group rats were orally administered with 3 ml of 0.5% sodium carboxymethyl cellulose (vehicle), whereas barbigerone was (10 and 20 mg kg-1) administered orally to the rats from the test group. During the 14-day treatment, control group rats were given 3 ml kg-1 day-1 saline, and all other groups were administered SCOP (1 mg kg-1 day-1, i.p.) 1 h after barbigerone p.o. treatment. The spontaneous alternation activities, learning capacities of a rat's memory were tested with Morris water maze and Y-maze. Reduced glutathione, malondialdehyde, acetylcholine esterase (AChE) and catalase (CAT) levels were measured in rat brain tissue as oxidative stress/antioxidant markers. Moreover, the levels of tumour necrosis factor, interleukin-6 (IL-6) and IL-1β were also estimated. Treatment with barbigerone in SCOP-administered rats dramatically reduced SCOP-induced neurobehavioural deficits, oxidative stress and neuroinflammatory markers, improved endogenous antioxidants, and restored AChE activity. By improving cholinergic function and reducing oxidative damage, barbigerone could mitigate the effects of SCOP-induced changes in the brain.

Intrahippocampal Inoculation of Aβ1-42 Peptide in Rat as a Model of Alzheimer's Disease Identified MicroRNA-146a-5p as Blood Marker with Anti-Inflammatory Function in Astrocyte Cells

Circulating microRNAs (miRNAs) have aroused a lot of interest as reliable blood diagnostic biomarkers of Alzheimer's disease (AD). Here, we investigated the panel of expressed blood miRNAs in response to aggregated Aβ_1-42 peptides infused in the hippocampus of adult rats to mimic events of the early onset of non-familial AD disorder. Aβ_1-42 peptides in the hippocampus led to cognitive impairments associated with an astrogliosis and downregulation of circulating miRNA-146a-5p, -29a-3p, -29c-3p, -125b-5p, and-191-5p. We established the kinetics of expression of selected miRNAs and found differences with those detected in the APP_swe/PS1_dE9 transgenic mouse model. Of note, miRNA-146a-5p was exclusively dysregulated in the Aβ-induced AD model. The treatment of primary astrocytes with Aβ_1-42 peptides led to miRNA-146a-5p upregulation though the activation of the NF-κB signaling pathway, which in turn downregulated IRAK-1 but not TRAF-6 expression. As a consequence, no induction of IL-1β, IL-6, or TNF-α was detected. Astrocytes treated with a miRNA-146-5p inhibitor rescued IRAK-1 and changed TRAF-6 steady-state levels that correlated with the induction of IL-6, IL-1β, and CXCL1 production, indicating that miRNA-146a-5p operates anti-inflammatory functions through a NF-κB pathway negative feedback loop. Overall, we report a panel of circulating miRNAs that correlated with Aβ_1-42 peptides' presence in the hippocampus and provide mechanistic insights into miRNA-146a-5p biological function in the development of the early stage of sporadic AD.

TRPV1 regulates ApoE4-disrupted intracellular lipid homeostasis and decreases synaptic phagocytosis by microglia

Although the ε4 allele of the apolipoprotein E (ApoE4) gene has been established as a genetic risk factor for many neurodegenerative diseases, including Alzheimer's disease, the mechanism of action remains poorly understood. Transient receptor potential vanilloid 1 (TRPV1) was reported to regulate autophagy to protect against foam cell formation in atherosclerosis. Here, we show that ApoE4 leads to lipid metabolism dysregulation in microglia, resulting in enhanced MHC-II-dependent antigen presentation and T-cell activation. Lipid accumulation and inflammatory reactions were accelerated in microglia isolated from TRPV1^flox/flox; Cx3cr1^cre-ApoE4 mice. We showed that metabolic boosting by treatment with the TRPV1 agonist capsaicin rescued lipid metabolic impairments in ApoE4 neurons and defects in autophagy caused by disruption of the AKT-mTOR pathway. TRPV1 activation with capsaicin reversed ApoE4-induced microglial immune dysfunction and neuronal autophagy impairment. Capsaicin rescued memory impairment, tau pathology, and neuronal autophagy in ApoE4 mice. Activation of TRPV1 decreased microglial phagocytosis of synapses in ApoE4 mice. TRPV1 gene deficiency exacerbated recognition memory impairment and tau pathology in ApoE4 mice. Our study suggests that TRPV1 regulation of lipid metabolism could be a therapeutic approach to alleviate the consequences of the ApoE4 allele.

Circadian dysregulation and Alzheimer’s disease: A comprehensive review

Alzheimer’s disease (AD), the foremost variant of dementia, has been associated with a menagerie of risk factors, many of which are considered to be modifiable. Among these modifiable risk factors is circadian rhythm, the chronobiological system that regulates sleep‐wake cycles, food consumption timing, hydration timing, and immune responses amongst many other necessary physiological processes. Circadian rhythm at the level of the suprachiasmatic nucleus (SCN), is tightly regulated in the human body by a host of biomolecular substances, principally the hormones melatonin, cortisol, and serotonin. In addition, photic information projected along afferent pathways to the SCN and peripheral oscillators regulates the synthesis of these hormones and mediates the manner in which they act on the SCN and its substructures. Dysregulation of this cycle, whether induced by environmental changes involving irregular exposure to light, or through endogenous pathology, will have a negative impact on immune system optimization and will heighten the deposition of Aβ and the hyperphosphorylation of the tau protein. Given these correlations, it appears that there is a physiologic association between circadian rhythm dysregulation and AD. This review will explore the physiology of circadian dysregulation in the AD brain, and will propose a basic model for its role in AD‐typical pathology, derived from the literature compiled and referenced throughout.

Network reconstruction for trans acting genetic loci using multi-omics data and prior information

BACKGROUND

Molecular measurements of the genome, the transcriptome, and the epigenome, often termed multi-omics data, provide an in-depth view on biological systems and their integration is crucial for gaining insights in complex regulatory processes. These data can be used to explain disease related genetic variants by linking them to intermediate molecular traits (quantitative trait loci, QTL). Molecular networks regulating cellular processes leave footprints in QTL results as so-called trans-QTL hotspots. Reconstructing these networks is a complex endeavor and use of biological prior information can improve network inference. However, previous efforts were limited in the types of priors used or have only been applied to model systems. In this study, we reconstruct the regulatory networks underlying trans-QTL hotspots using human cohort data and data-driven prior information.

METHODS

We devised a new strategy to integrate QTL with human population scale multi-omics data. State-of-the art network inference methods including BDgraph and glasso were applied to these data. Comprehensive prior information to guide network inference was manually curated from large-scale biological databases. The inference approach was extensively benchmarked using simulated data and cross-cohort replication analyses. Best performing methods were subsequently applied to real-world human cohort data.

RESULTS

Our benchmarks showed that prior-based strategies outperform methods without prior information in simulated data and show better replication across datasets. Application of our approach to human cohort data highlighted two novel regulatory networks related to schizophrenia and lean body mass for which we generated novel functional hypotheses.

CONCLUSIONS

We demonstrate that existing biological knowledge can improve the integrative analysis of networks underlying trans associations and generate novel hypotheses about regulatory mechanisms.

PSEN2 Thr421Met Mutation in a Patient with Early Onset Alzheimer’s Disease

Presenilin-2 (PSEN2) mutation Thr421Met was identified from a 57-years old patient with early onset Alzheimer’s disease (EOAD) for the first time in Korea. Previously, this mutation was discovered in an EOAD patient in Japan without a change on amyloid production from the cellular study. Both Korean and Japanese patients developed the disease in their 50s. Memory loss was prominent in both cases, but no additional clinical information was available on the Japanese patient. Magnetic resonance imaging (MRI) images of the Korean patient revealed asymmetric atrophies in both temporo-parietal lobes. In addition, amyloid positron emission tomography (PET) also revealed amyloid deposits in the gray matter of the temporo-parietal lobes asymmetrically. PSEN2 Thr421 was conserved among a majority of vertebrates (such as zebras, elephants, and giant pandas); hence, Thr421 could play an important role in its functions and any mutations could cause detrimental ramifications in its interactions. Interestingly, PSEN2 Thr421 could have homology with PSEN1 Thr440, as PSEN1 T440del mutations were reported from patients with AD or dementia with Lewy bodies. Hence, the changed amino acid from threonine to methionine of PSEN2 Thr421 could cause significant structural alterations in causing local protein dynamics, leading to its pathogenicity in EOAD. Lastly, PSEN2 Thr421Met may interact with other mutations in neurodegenerative disease related genes, which were found in the proband patient, such as ATP binding cassette subfamily A member 7 (ABCA7), Notch Receptor 3 (NOTCH3), or Leucine-rich repeat kinase 2 (LRRK2). These interactions of pathway networks among PSEN2 and other disease risk factors could be responsible for the disease phenotype through other pathways. For example, PSEN2 and ABCA7 may impact amyloid processing and reduce amyloid clearance. Interaction between PSEN2 and NOTCH3 variants may be associated with abnormal NOTCH signaling and a lower degree of neuroprotection. Along with LRRK2 variants, PSEN2 Thr421Met may impact neurodegeneration through Wnt related pathways. In the future, cellular studies of more than one mutation by CRISPR-Cas9 method along with biomarker profiles could be helpful to understand the complicated pathways.

Diet in the Prevention of Alzheimer's Disease: Current Knowledge and Future Research Requirements

Alzheimer's disease is a progressive brain disease that is becoming a major health problem in today's world due to the aging population. Despite it being widely known that diet has a significant impact on the prevention and progression of Alzheimer's disease, the literature data are still scarce and controversial. The application of the principles of rational nutrition for the elderly is suggested for Alzheimer's disease. The diet should be rich in neuroprotective nutrients, i.e., antioxidants, B vitamins, and polyunsaturated fatty acids. Some studies suggest that diets such as the Mediterranean diet, the DASH (Dietary Approaches to Stop Hypertension) diet, and the MIND (Mediterranean-DASH Intervention for Neurodegenerative Delay) diet have a beneficial effect on the risk of developing Alzheimer's disease.

Prediction of Alzheimer’s Disease by a Novel Image-Based Representation of Gene Expression

Early intervention can delay the progress of Alzheimer’s Disease (AD), but currently, there are no effective prediction tools. The goal of this study is to generate a reliable artificial intelligence (AI) model capable of detecting the high risk of AD, based on gene expression arrays from blood samples. To that end, a novel image-formation method is proposed to transform single-dimension gene expressions into a discriminative 2-dimensional (2D) image to use convolutional neural networks (CNNs) for classification. Three publicly available datasets were pooled, and a total of 11,618 common genes’ expression values were obtained. The genes were then categorized for their discriminating power using the Fisher distance (AD vs. control (CTL)) and mapped to a 2D image by linear discriminant analysis (LDA). Then, a six-layer CNN model with 292,493 parameters were used for classification. An accuracy of 0.842 and an area under curve (AUC) of 0.875 were achieved for the AD vs. CTL classification. The proposed method obtained higher accuracy and AUC compared with other reported methods. The conversion to 2D in CNN offers a unique advantage for improving accuracy and can be easily transferred to the clinic to drastically improve AD (or any disease) early detection.

Gene expression profiling and protein-protein interaction analysis reveals the dynamic role of MCM7 in Alzheimer's disorder and breast cancer

The interrelation of cancer and Alzheimer's disorder (AD)-associated molecular mechanisms, reported last decade, paved the path for drug discoveries. In this direction, while chemotherapy is well established for breast cancer (BC), the detection and targeted therapy for AD is not advanced due to a lack of recognized peripheral biomarkers. The present study aimed to find diagnostic and prognostic molecular signature markers common to both BC and AD for possible drug targeting and repurposing. For these disorders, two corresponding microarray datasets (GSE42568, GSE33000) were used for identifying the differentially expressed genes (DEGs), resulting in recognition of CD209 and MCM7 as the two common players. While the CD209 gene was upregulated in both disorders and has been studied vastly, the MCM7 gene showed a strikingly reverse pattern of expression level, downregulated in the case of BC while upregulated in the case of AD. Thus, the MCM7 gene was further analyzed for expression, predictions, and validations of its structure and protein-protein interaction (PPI) for the possible development of new treatment methods for AD. The study concluded with indicative drug repurposing studies to check the effect of existing clinically approved drugs for BC for rectifying the expression levels of the mutated MCM7 gene in AD.

Supplementary Information

The online version contains supplementary material available at 10.1007/s13205-022-03207-1.

Whole Exome Sequencing Reveals a Novel APOE Mutation in a Patient With Sporadic Early-Onset Alzheimer's Disease

Apolipoprotein (APOE) is implicated and verified as the main risk factor for early-onset Alzheimer's disease (AD). APOE is a protein that binds to lipids and is involved in cholesterol stability. Our paper reports a case of a sporadic early-onset AD (sEOAD) patient of a 54-year-old Korean man, where a novel APOE Leu159Pro heterozygous mutation was revealed upon Whole Exome Sequence analysis. The proband's CSF showed downregulated levels of Aβ42, with unchanged Tau levels. The mutation is in the Low-Density Lipoprotein Receptor (LDLR) region of the APOE gene, which mediates the clearance of APOE lipoproteins. LDLR works as a high-affinity point for APOE. Studies suggest that APOE-LDLR interplay could have varying effects. The LDLR receptor pathway has been previously suggested as a therapeutic target to treat tauopathy. However, the APOE-LDLR interaction has also shown a significant correlation with memory retention. Leu159Pro could be an interesting mutation that could be responsible for a less damaging pattern of AD by suppressing tau-association neurodegeneration while affecting the patient's memory retention and cognitive performance.

Reducing PDK1/Akt Activity: An Effective Therapeutic Target in the Treatment of Alzheimer's Disease

Alzheimer’s disease (AD) is a common age-related neurodegenerative disease that leads to memory loss and cognitive function damage due to intracerebral neurofibrillary tangles (NFTs) and amyloid-β (Aβ) protein deposition. The phosphoinositide-dependent protein kinase (PDK1)/protein kinase B (Akt) signaling pathway plays a significant role in neuronal differentiation, synaptic plasticity, neuronal survival, and neurotransmission via the axon–dendrite axis. The phosphorylation of PDK1 and Akt rises in the brain, resulting in phosphorylation of the TNF-α-converting enzyme (TACE) at its cytoplasmic tail (the C-terminal end), changing its internalization as well as its trafficking. The current review aimed to explain the mechanisms of the PDK1/Akt/TACE signaling axis that exerts its modulatory effect on AD physiopathology. We provide an overview of the neuropathological features, genetics, Aβ aggregation, Tau protein hyperphosphorylation, neuroinflammation, and aging in the AD brain. Additionally, we summarized the phosphoinositide 3-kinase (PI3K)/PDK1/Akt pathway-related features and its molecular mechanism that is dependent on TACE in the pathogenesis of AD. This study reviewed the relationship between the PDK1/Akt signaling pathway and AD, and discussed the role of PDK1/Akt in resisting neuronal toxicity by suppressing TACE expression in the cell membrane. This work also provides a perspective for developing new therapeutics targeting PDK1/Akt and TACE for the treatment of AD.

Biomarker Candidates for Alzheimer’s Disease Unraveled through In Silico Differential Gene Expression Analysis

Alzheimer’s disease (AD) is neurodegeneration that accounts for 60–70% of dementia cases. Symptoms begin with mild memory difficulties and evolve towards cognitive impairment. The underlying risk factors remain primarily unclear for this heterogeneous disorder. Bioinformatics is a relevant research tool that allows for identifying several pathways related to AD. Open-access databases of RNA microarrays from the peripheral blood and brain of AD patients were analyzed after background correction and data normalization; the Limma package was used for differential expression analysis (DEA) through statistical R programming language. Data were corrected with the Benjamini and Hochberg approach, and genes with p-values equal to or less than 0.05 were considered to be significant. The direction of the change in gene expression was determined by its variation in the log2-fold change between healthy controls and patients. We performed the functional enrichment analysis of GO using goana and topGO-Limma. The functional enrichment analysis of DEGs showed upregulated (UR) pathways: behavior, nervous systems process, postsynapses, enzyme binding; downregulated (DR) were cellular component organization, RNA metabolic process, and signal transduction. Lastly, the intersection of DEGs in the three databases showed eight shared genes between brain and blood, with potential use as AD biomarkers for blood tests.

Combination Therapy in Alzheimer’s Disease: Is It Time?

Alzheimer’s disease (AD) is the most common cause of dementia globally. There is increasing evidence showing AD has no single pathogenic mechanism, and thus treatment approaches focusing only on one mechanism are unlikely to be meaningfully effective. With only one potentially disease modifying treatment approved, targeting amyloid-β (Aβ), AD is underserved regarding effective drug treatments. Combining multiple drugs or designing treatments that target multiple pathways could be an effective therapeutic approach. Considering the distinction between added and combination therapies, one can conclude that most trials fall under the category of added therapies. For combination therapy to have an actual impact on the course of AD, it is likely necessary to target multiple mechanisms including but not limited to Aβ and tau pathology. Several challenges have to be addressed regarding combination therapy, including choosing the correct agents, the best time and stage of AD to intervene, designing and providing proper protocols for clinical trials. This can be achieved by a cooperation between the pharmaceutical industry, academia, private research centers, philanthropic institutions, and the regulatory bodies. Based on all the available information, the success of combination therapy to tackle complicated disorders such as cancer, and the blueprint already laid out on how to implement combination therapy and overcome its challenges, an argument can be made that the field has to move cautiously but quickly toward designing new clinical trials, further exploring the pathological mechanisms of AD, and re-examining the previous studies with combination therapies so that effective treatments for AD may be finally found.

Circular RNAs: Emblematic Players of Neurogenesis and Neurodegeneration

In the fascinating landscape of non-coding RNAs (ncRNAs), circular RNAs (circRNAs) are peeping out as a new promising and appreciated class of molecules with great potential as diagnostic and prognostic biomarkers. They come from circularization of single-stranded RNA molecules covalently closed and generated through alternative mRNA splicing. Dismissed for many years, similar to aberrant splicing by-products, nowadays, their role has been regained. They are able to regulate the expression of linear mRNA transcripts at different levels acting as miRNA sponges, interacting with ribonucleoproteins or exerting a control on gene expression. On the other hand, being extremely conserved across phyla and stable, cell and tissue specific, mostly abundant than the linear RNAs, it is not surprising that they should have critical biological functions. Curiously, circRNAs are particularly expressed in brain and they build up during aging and age-related diseases. These extraordinary peculiarities make circRNAs potentially suitable as promising molecular biomarkers, especially of aging and neurodegenerative diseases. This review aims to explore new evidence on circRNAs, emphasizing their role in aging and pathogenesis of major neurodegenerative disorders, Alzheimer's disease, frontotemporal dementia, and Parkinson's diseases with a look toward their potential usefulness in biomarker searching.

Influence of the Microbiota-Gut-Brain Axis on Cognition in Alzheimer’s Disease

The gut microbiota is made up of trillions of microbial cells including bacteria, viruses, fungi, and other microbial bodies and is greatly involved in the maintenance of proper health of the host body. In particular, the gut microbiota has been shown to not only be involved in brain development but also in the modulation of behavior, neuropsychiatric disorders, and neurodegenerative diseases including Alzheimer’s disease. The precise mechanism by which the gut microbiota can affect the development of Alzheimer’s disease is unknown, but the gut microbiota is thought to communicate with the brain directly via the vagus nerve or indirectly through signaling molecules such as cytokines, neuroendocrine hormones, bacterial components, neuroactive molecules, or microbial metabolites such as short-chain fatty acids. In particular, interventions such as probiotic supplementation, fecal microbiota transfer, and supplementation with microbial metabolites have been used not only to study the effects that the gut microbiota has on behavior and cognitive function, but also as potential therapeutics for Alzheimer’s disease. A few of these interventions, such as probiotics, are promising candidates for the improvement of cognition in Alzheimer ’s disease and are the focus of this review.

Alzheimer's Disease: Pathogenesis and Therapeutic Interventions

BACKGROUND

Alzheimer's Disease (AD) is the most common cause of dementia. Genetics, excessive exposure to environmental pollutants, as well as unhealthy lifestyle practices are often linked to the development of AD. No therapeutic approach has achieved complete success in treating AD; however, early detection and management with appropriate drugs are key to improving prognosis.

INTERVENTIONS

The pathogenesis of AD was extensively discussed in order to understand the reasons for the interventions suggested. The interventions reviewed include the use of different therapeutic agents and approaches, gene therapy, adherence to healthy dietary plans (Mediterranean diet, Okinawan diet and MIND diet), as well as the use of medicinal plants. The potential of nanotechnology as a multidisciplinary and interdisciplinary approach in the design of nano-formulations of AD drugs and the use of Superparamagnetic Iron Oxide Nanoparticles (SPIONs) as theranostic tools for early detection of Alzheimer's disease were also discussed.

A functional variant of SHARPIN confers increased risk of late-onset Alzheimer's disease

Late-onset Alzheimer's disease (LOAD) is the most common form of dementia, and its pathogenesis is multifactorial. We previously reported a rare functional variant of SHARPIN (rs572750141, NP_112236.3:p.Gly186Arg) that was significantly associated with LOAD. In addition, several recent studies have suggested the potential role of SHARPIN in AD pathogenesis. In this study, we sought to identify additional functional variants of SHARPIN in Japanese population. Six highly deleterious variants of SHARPIN, comprising four missense variants, one frameshift variant, and one stop-gain variant were detected from whole-genome sequencing data for 180 patients with LOAD and 184 with mild cognitive impairment. One of these candidate variants (rs77359862, NP_112236.3:p.Arg274Trp) was significantly associated with an increased risk of LOAD in 5043 LOAD cases and 11984 controls (P = 0.0016, odds ratio = 1.43). Furthermore, this variant SHARPIN showed aberrant cellular localization and reduced the activation of NF-κB, a central mediator of inflammatory and immune responses. Further investigation of the physiologic role of SHARPIN may reveal the mechanism of onset of LOAD.

Automatic Detection of K-Complexes Using the Cohen Class Recursiveness and Reallocation Method and Deep Neural Networks with EEG Signals

Evoked and spontaneous K-complexes are thought to be involved in sleep protection, but their role as biomarkers is still under debate. K-complexes have two major functions: first, they suppress cortical arousal in response to stimuli that the sleeping brain evaluates to avoid signaling danger; and second, they help strengthen memory. K-complexes also play an important role in the analysis of sleep quality, in the detection of diseases associated with sleep disorders, and as biomarkers for the detection of Alzheimer’s and Parkinson’s diseases. Detecting K-complexes is relatively difficult, as reliable methods of identifying this complex cannot be found in the literature. In this paper, we propose a new method for the automatic detection of K-complexes combining the method of recursion and reallocation of the Cohen class and the deep neural networks, obtaining a recursive strategy aimed at increasing the percentage of classification and reducing the computation time required to detect K-complexes by applying the proposed methods.

Inhibition of GSK_3β by Iridoid Glycosides of Snowberry (Symphoricarpos albus) Effective in the Treatment of Alzheimer's Disease Using Computational Drug Design Methods

The inhibition of glycogen synthase kinase-3β (GSK-3β) activity prevents tau hyperphosphorylation and binds it to the microtubule network. Therefore, a GSK-3β inhibitor may be a recommended drug for Alzheimer's treatment. In silico methods are currently considered as one of the fastest and most cost-effective available alternatives for drug/design discovery in the field of treatment. In this study, computational drug design was conducted to introduce compounds that play an effective role in inhibiting the GSK-3β enzyme by molecular docking and molecular dynamics simulation. The iridoid glycosides of the common snowberry (Symphoricarpos albus), including loganin, secologanin, and loganetin, are compounds that have an effect on improving memory and cognitive impairment and the results of which on Alzheimer's have been studied as well. In this study, in the molecular docking phase, loganin was considered a more potent inhibitor of this protein by establishing a hydrogen bond with the ATP-binding site of GSK-3β protein and the most negative binding energy to secologanin and loganetin. Moreover, by molecular dynamics simulation of these ligands and GSK-3β protein, all structures were found to be stable during the simulation. In addition, the protein structure represented no change and remained stable by binding ligands to GSK-3β protein. Furthermore, loganin and loganetin have higher binding free energy than secologanin; thus, these compounds could effectively bind to the active site of GSK-3β protein. Hence, loganin and loganetin as iridoid glycosides can be effective in Alzheimer's prevention and treatment, and thus, further in vitro and in vivo studies can focus on these iridoid glycosides as an alternative treatment.

A Pathogenic Presenilin-1 Val96Phe Mutation from a Malaysian Family

Presenilin-1 (PSEN1) is one of the causative genes for early onset Alzheimer's disease (EOAD). Recently, emerging studies have reported several novel PSEN1 mutations among Asians. In this study, a PSEN1 Val96Phe mutation was discovered in two siblings from Malaysia with a strong family history of disease. This is the second report of PSEN1 Val96Phe mutation among EOAD patients in Asia and in the world. Patients presented symptomatic changes in their behaviors and personality, such as apathy and withdrawal in their 40s. Previous cellular studies with COS1 cell lines revealed the mutation increased the amyloid-β42 (Aβ42) productions. In the present study, whole-exome sequencing was performed on the two siblings with EOAD, and they were analyzed against the virtual panel of 100 genes from various neurodegenerative diseases. In silico modeling was also performed on PSEN1 Val96Phe mutation. This mutation was located on the first transmembrane helix of PSEN1 protein, resulting significant intramolecular stresses in the helices. This helical domain would play a significant role in γ-secretase cleavage for the increased Aβ42 productions. Several other adjacent mutations were reported in this helical domain, including Ile83Thr or Val89Leu. Our study suggested that perturbations in TMI-HLI-TMII regions could also be associated with C-terminal fragment accumulation of APP and enhanced amyloid productions.

Presenilin 1 Regulates Membrane Homeostatic Pathways that are Dysregulated in Alzheimer's Disease

Mutations in the PSEN1 gene, encoding presenilin 1 (PS1), are the most common cause of familial Alzheimer's disease (fAD). Since the first mutations in the PSEN1 gene were discovered more than 25 years ago, many postulated functions of PS1 have been investigated. The majority of earlier studies focused on its role as the catalytic component of the γ-secretase complex, which in concert with β site amyloid precursor protein cleaving enzyme 1 (BACE1), mediates the formation of Aβ from amyloid-β protein precursor (AβPP). Though mutant PS1 was originally considered to cause AD by promoting Aβ pathology through its protease function, it is now becoming clear that PS1 is a multifunctional protein involved in regulating membrane dynamics and protein trafficking. Therefore, through loss of these abilities, mutant PS1 has the potential to impair numerous cellular functions such as calcium flux, organization of proteins in different compartments, and protein turnover via vacuolar metabolism. Impaired calcium signaling, vacuolar dysfunction, mitochondrial dysfunction, and increased ER stress, among other related membrane-dependent disturbances, have been considered critical to the development and progression of AD. Given that PS1 plays a key regulatory role in all these processes, this review will describe the role of PS1 in different cellular compartments and provide an integrated view of how PS1 dysregulation (due to mutations or other causes) could result in impairment of various cellular processes and result in a "multi-hit", integrated pathological outcome that could contribute to the etiology of AD.

Risk Factors for Alzheimer's Disease: An Epidemiological Study

INTRODUCTION

Dementia becomes a major public health challenge in both the Czech Republic and worldwide. The most common form of dementia is Alzheimer's disease (AD).

OBJECTIVE

We conducted two successive epidemiological projects in 2012-2015 and 2016-2019. Their aim was to study the effect of selected potential genetic, vascular and psychosocial risk factors on the development of AD by comparing their frequencies in AD patients and controls.

METHODS

Epidemiological case-control studies were conducted. In total, data from 2106 participants (1096 cases, 1010 controls) were analyzed.

RESULTS

Three times more females than males suffered from AD. The highest proportion of cases were those with primary education, unlike controls. There were statistically significantly more manual workers among cases than among controls. Of selected vascular risk factors, coronary heart disease was found to be statistically significantly more frequent in cases than in controls. The onset of hypertension and diabetes mellitus was earlier in controls than in cases. As for hobbies and interests, there were statistically significant differences in physical activity, reading and solving crosswords between the groups, with these activities being more common in controls.

CONCLUSION

The prevalence of chronic neurodegenerative diseases, in particular AD, is currently increasing. Given the aging of the population, these conditions may be expected to rise in prevalence. Potential risk of AD needs to be studied, analyzed and confirmed; a detailed knowledge of the risks of AD and early detection of the pathology may therefore be very beneficial for prevention and early treatment of this condition.

Inflammatory gene expression profiling in peripheral blood from patients with Alzheimer's disease reveals key pathways and hub genes with potential diagnostic utility: a preliminary study

BACKGROUND

Alzheimer's disease (AD) is an age-related neurodegenerative disease caused by central nervous system disorders. Late-onset Alzheimer disease (LOAD) is the most common neurodegenerative disorder worldwide. Differences at the expression level of certain genes, resulting from either genetic variations or environmental interactions, might be one of the mechanisms underlying differential risks for developing AD. Peripheral blood genome transcriptional profiling may provide a powerful and minimally invasive tool for the identification of novel targets beyond Aβ and tau for AD research.

METHODS

This preliminary study explores molecular pathogenesis of LOAD-related inflammation through next generation sequencing, to assess RNA expression profiles in peripheral blood from five patients with LOAD and 10 healthy controls.

RESULTS

The analysis of RNA expression profiles revealed 94 genes up-regulated and 147 down-regulated. Gene function analysis, including Gene Ontology (GO) and KOBAS-Kyoto Encyclopedia of DEGs and Genomes (KEGG) pathways indicated upregulation of interferon family (INF) signaling, while the down-regulated genes were mainly associated with the cell cycle process. KEGG metabolic pathways mapping showed gene expression alterations in the signaling pathways of JAK/STAT, chemokines, MAP kinases and Alzheimer disease. The results of this preliminary study provided not only a comprehensive picture of gene expression, but also the key processes associated with pathology for the regulation of neuroinflammation, to improve the current mechanisms to treat LOAD.

Effect of Age on Clinical Trial Outcome in Participants with Probable Alzheimer's Disease

Background:

Age may affect treatment outcome in trials of mild probable Alzheimer’s disease (AD).

Objective:

We examined age as a moderator of outcome in an exploratory study of deep brain stimulation targeting the fornix (DBS-f) region in participants with AD.

Methods:

Forty-two participants were implanted with DBS electrodes and randomized to double-blind DBS-f stimulation (“on”) or sham DBS-f (“off”) for 12 months.

Results:

The intervention was safe and well tolerated. However, the selected clinical measures did not differentiate between the “on” and “off” groups in the intent to treat (ITT) population. There was a significant age by time interaction with the Alzheimer’s Disease Assessment Scale; ADAS-cog-13 (p = 0.028). Six of the 12 enrolled participants < 65 years old (50%) markedly declined on the ADAS-cog-13 versus only 6.7%of the 30 participants≥65 years old regardless of treatment assignment (p = 0.005). While not significant, post-hoc analyses favored DBS-f “off” versus “on” over 12 months in the < 65 age group but favored DBS-f “on” versus “off” in the≥65 age group on all clinical metrics. On the integrated Alzheimer’s Disease rating scale (iADRS), the effect size contrasting DBS-f “on” versus “off” changed from +0.2 (favoring “off”) in the < 65 group to –0.52 (favoring “on”) in the≥65 age group.

Conclusion:

The findings highlight issues with subject selection in clinical trials for AD. Faster disease progression in younger AD participants with different AD sub-types may influence the results. Biomarker confirmation and genotyping to differentiate AD subtypes is important for future clinical trials.

Alzheimer's Disease in the Down Syndrome: An Overview of Genetics and Molecular Aspects

The overexpression of the amyloid precursor protein (APP) gene, encoded on chromosome 21, has been associated in Down syndrome (DS) with the development of early-onset Alzheimer's disease (EOAD). The increase in APP levels leads to an overproduction of amyloid-β (Aβ) peptide that accumulates in the brain. In response to this deposition, microglial cells are active and generate cascade events that include release cytokines and chemokine. The prolonged activation microglial cells induce neuronal loss, production of reactive oxygen species, neuron death, neuroinflammation, and consequently the development of Alzheimer's disease (AD). The intrinsically deficient immune systems in people with DS result in abnormalities in cytokine levels, which possibly contribute to the development of neurodegenerative disorders such as AD. Knowledge about the biomarkers involved in the process of neurodegeneration and neuroinflamation is important for understanding the mechanisms involved in the incidence and the precocity of AD in individuals with DS.

Ameliorative effects of astaxanthin on brain tissues of alzheimer's disease-like model: cross talk between neuronal-specific microRNA-124 and related pathways

Alzheimer's disease (AD) is a chronic, progressive, multifactorial, and the most common neurodegenerative disease which causes dementia and mental deterioration in the elderly. The available treatments for AD are not disease-modifying drugs and only provide symptomatic relief. Astaxanthin (ATX), a second-generation antioxidant, is a dark red carotenoid and exhibits the highest antioxidant capacity, anti-inflammatory, neuroprotective, and antiapoptotic effects. In this study, we investigated the therapeutic effect of different doses of ATX on the cerebral cortex and hippocampus of AD-like rats. The AD-like model was induced in rats using hydrated aluminum chloride (AlCl₃.6H₂O) solution that was given orally at a dose of 75 mg/kg daily for 6 weeks. Morris water maze (MWM) behavioral test was performed to confirm the cognitive dysfunction then AD-like rats were orally treated with different doses of ATX (5, 10, and 15 mg/kg) dissolved in dimethyl sulfoxide (DMSO) for six weeks. The results indicated that ATX significantly and dose-dependently improved the performance of AD-like rats treated with ATX during MWM and suppress the accumulation of amyloid β_1-42 and malondialdehyde. Also, significantly inhibit acetylcholinesterase and monoamine oxidase activities and the expression of β-site amyloid precursor protein cleaving enzyme 1 (BACE 1). ATX also significantly elevated the content of acetylcholine, serotonin, and nuclear factor erythroid-2-related factor 2 (Nrf2) and miRNA-124 expression. The effect of ATX treatment was confirmed by histopathological observations using H&E stain and morphometric tissue analysis. From this study, we concluded that ATX may be a promising therapeutic agent for AD through targeting different pathogenic pathways.

Differentially Expressed Circular RNAs in Peripheral Blood Mononuclear Cells of Patients with Parkinson's Disease

Background

New noninvasive and affordable molecular approaches that will complement current practices and increase the accuracy of Parkinson's disease (PD) diagnosis are urgently needed. Circular RNAs (circRNAs) are stable noncoding RNAs that accumulate with aging in neurons and are increasingly shown to regulate all aspects of neuronal development and function.

Objectives

Τhe aims of this study were to identify differentially expressed circRNAs in blood mononuclear cells of patients with idiopathic PD and explore the competing endogenous RNA networks affected.

Methods

Eighty‐seven circRNAs were initially selected based on relatively high gene expression in the human brain. More than half of these were readily detectable in blood mononuclear cells using real‐time reverse transcription‐polymerase chain reaction. Comparative expression analysis was then performed in blood mononuclear cells from 60 control subjects and 60 idiopathic subjects with PD.

Results

Six circRNAs were significantly down‐regulated in patients with PD. The classifier that best distinguished PD consisted of four circRNAs with an area under the curve of 0.84. Cross‐linking immunoprecipitation‐sequencing data revealed that the RNA‐binding proteins bound by most of the deregulated circRNAs include the neurodegeneration‐associated FUS, TDP43, FMR1, and ATXN2. MicroRNAs predicted to be sequestered by most deregulated circRNAs have the Gene Ontology categories “protein modification” and “transcription factor activity” mostly enriched.

Conclusions

This is the first study that identifies specific circRNAs that may serve as diagnostic biomarkers for PD. Because they are highly expressed in the brain and are derived from genes with essential brain functions, they may also hint on the PD pathways affected. © 2021 Biomedical Research Foundation, Academy of Athens. Movement Disorders published by Wiley Periodicals LLC on behalf of International Parkinson and Movement Disorder Society.

Novel Psychoactive Phenethylamines: Impact on Genetic Material

Psychedelic and stimulating phenethylamines belong to the family of new psychoactive substances (NPS). The acute toxicity framework has begun to be investigated, while studies showing genotoxic potential are very limited or not available. Therefore, in order to fill this gap, the aim of the present work was to evaluate the genotoxicity by treating TK6 cells with 2C-H, 2C-I, 2C-B, 25B-NBOMe, and the popular 3,4-Methylenedioxymethylamphetamine (MDMA). On the basis of cytotoxicity and cytostasis results, we selected the concentrations (6.25–35 µM) to be used in genotoxicity analysis. We used the micronucleus (MN) as indicator of genetic damage and analyzed the MNi frequency fold increase by an automated flow cytometric protocol. All substances, except MDMA, resulted genotoxic; therefore, we evaluated reactive oxygen species (ROS) induction as a possible mechanism at the basis of the demonstrated genotoxicity. The obtained results showed a statistically significant increase in ROS levels for all genotoxic phenethylamines confirming this hypothesis. Our results highlight the importance of genotoxicity evaluation for a complete assessment of the risk associated also with NPS exposure. Indeed, the subjects who do not have hazardous behaviors or require hospitalization by using active but still “safe” doses could run into genotoxicity and in the well-known long-term effects associated.

Local Sleep and Alzheimer's Disease Pathophysiology

Even prior to the onset of the prodromal stages of Alzheimer's disease (AD), a constellation of sleep disturbances are apparent. A series of epidemiological studies indicate that multiple forms of these sleep disturbances are associated with increased risk for developing mild cognitive impairment (MCI) and AD, even triggering disease onset at an earlier age. Through the combination of causal manipulation studies in humans and rodents, as well as targeted examination of sleep disturbance with respect to AD biomarkers, mechanisms linking sleep disturbance to AD are beginning to emerge. In this review, we explore recent evidence linking local deficits in brain oscillatory function during sleep with local AD pathological burden and circuit-level dysfunction and degeneration. In short, three deficits in the local expression of sleep oscillations have been identified in relation to AD pathophysiology: (1) frequency-specific frontal deficits in slow wave expression during non-rapid eye movement (NREM) sleep, (2) deficits in parietal sleep spindle expression, and (3) deficits in the quality of electroencephalographic (EEG) desynchrony characteristic of REM sleep. These deficits are noteworthy since they differ from that seen in normal aging, indicating the potential presence of an abnormal aging process. How each of these are associated with β-amyloid (Aβ) and tau pathology, as well as neurodegeneration of circuits sensitive to AD pathophysiology, are examined in the present review, with a focus on the role of dysfunction within fronto-hippocampal and subcortical sleep-wake circuits. It is hypothesized that each of these local sleep deficits arise from distinct network-specific dysfunctions driven by regionally-specific accumulation of AD pathologies, as well as their associated neurodegeneration. Overall, the evolution of these local sleep deficits offer unique windows into the circuit-specific progression of distinct AD pathophysiological processes prior to AD onset, as well as their impact on brain function. This includes the potential erosion of sleep-dependent memory mechanisms, which may contribute to memory decline in AD. This review closes with a discussion of the remaining critical knowledge gaps and implications of this work for future mechanistic studies and studies implementing sleep-based treatment interventions.

Review of beneficial effects of resveratrol in neurodegenerative diseases such as Alzheimer's disease

PURPOSE

The prevalence of Alzheimer's Disease is rising, in part due to increase in the medium age of residents in developed countries. The aim of the study has been to determine whether resveratrol (RSV) can be effective in the prevention or treatment of Alzheimer's Disease, providing its antioxidant, anti-inflammatory, and SIRT1-activating properties.

METHODS

A systematic review of some experimental and clinical studies has been made. The eligibility criteria have comprised: maximum 10 years passed from the study publication, geographical diversity of the studies performed, and - as much as possible - pertaining of the reviewed study results both to animal models of AD, and to humans.

RESULTS

After the final assessment of the eligibility criteria, 96 research studies have been included in the review. Overall results suggest that RSV can be effectively used in the prevention of AD, especially in reference to its familial forms with an early onset. At the same time, efficacy of RSV in the treatment of AD needs further studies, aimed at: improving its transport through the blood-brain barrier (BBB), performing prospective clinical in vivo trials on large groups of patients, and determining the optimal RSV dosage.

DISCUSSION

Providing RSV mechanisms of action, inhibitory in reference to many pathomechanisms of AD, it seems very likely that RSV could be effective in AD prevention. The main limitations referring to such presumption include: limited permeability of BBB to RSV, and scarcity of clinical studies on RSV pertaining to large groups of humans.

Revisiting the blood-brain barrier: A hard nut to crack in the transportation of drug molecules

Barriers are the hallmark of a healthy physiology, blood-brain barrier (BBB) being a tough nut to crack for most of the antigens and chemical substances. The presence of tight junctions plays a remarkable role in defending the brain from antigenic and pathogenic attacks. BBB constitutes a diverse assemblage of multiple physical and chemical barriers that judiciously restrict the flux of blood solutes into and out of the brain. Restrictions through the paracellular pathway and the tight junctions between intercellular clefts, together create well regulated metabolic and transport barricades, critical to brain pathophysiology. The brain being impermeable to many essential metabolites and nutrients regulates transportation via specialized transport systems across the endothelial abluminal and luminal membranes. The epithelial cells enveloping capillaries of the choroid plexus regulates the transport of complement, growth factors, hormones, microelements, peptides and trace elements into ventricles. Nerve terminals, microglia, and pericytes associated with the endothelium support barrier induction and function, ensuring an optimally stable ionic microenvironment that facilitates neurotransmission, orchestrated by multiple ion channels (Na⁺, K⁺ Mg²⁺, Ca²⁺) and transporters. Brain pathology which can develop due to genetic mutations or secondary to other cerebrovascular, neurodegenerative diseases can cause aberration in the microvasculature of CNS which is the uniqueness of BBB. This can also alter BBB permeation and result in BBB breakdown and other neurodegenerative disorders such as Alzheimer's disease, Parkinson's disease, amyotrophic lateral sclerosis, and multiple sclerosis. The concluding section outlines contemporary trends in drug discovery, focusing on molecular determinants of BBB permeation and novel drug-delivery systems, such as dendrimers, liposomes, nanoparticles, nanogels, etc.

Transcriptome Profile of Nicotinic Receptor-Linked Sensitization of Beta Amyloid Neurotoxicity

Understanding the specific gene changes underlying the prodromic stages of Alzheimer’s disease pathogenesis will aid the development of new, targeted therapeutic strategies for this neurodegenerative disorder. Here, we employed RNA-sequencing to analyze global differential gene expression in a defined model nerve cell line expressing α4β2 nicotinic receptors (nAChRs), high-affinity targets for beta amyloid (Aβ). The nAChR-expressing neuronal cells were treated with nanomolar Aβ_1–42 to gain insights into the molecular mechanisms underlying Aβ-induced neurotoxicity in the presence of this sensitizing target receptor. We identified 15 genes (out of 15,336) that were differentially expressed upon receptor-linked Aβ treatment. Genes up-regulated with Aβ treatment were associated with calcium signaling and axonal vesicle transport (including the α4 nAChR subunit, the calcineurin regulator RCAN3, and KIF1C of the kinesin family). Downregulated genes were associated with metabolic, apoptotic or DNA repair pathways (including APBA3, PARP1 and RAB11). Validation of the differential expression was performed via qRT-PCR and immunoblot analysis in the defined model nerve cell line and primary mouse neurons. Further verification was performed using immunocytochemistry. In conclusion, we identified apparent changes in gene expression on Aβ treatment in the presence of the sensitizing nAChRs, linked to early-stage Aβ-induced neurotoxicity, which may represent novel therapeutic targets.

Next Generation Sequencing Analysis in Early Onset Dementia Patients

Background:

Early onset dementias (EOD) are rare neurodegenerative dementias that present before 65 years. Genetic factors have a substantially higher pathogenetic contribution in EOD patients than in late onset dementia.

Objective:

To identify known and/or novel rare variants in major candidate genes associated to EOD by high-throughput sequencing. Common-risk variants of apolipoprotein E (APOE) and prion protein (PRNP) genes were also assessed.

Methods:

We studied 22 EOD patients recruited in Memory Clinics, in the context of studies investigating genetic forms of dementia. Two methodological approaches were applied for the target-Next Generation Sequencing (NGS) analysis of these patients. In addition, we performed progranulin plasma dosage, C9Orf72 hexanucleotide repeat expansion analysis, and APOE genotyping.

Results:

We detected three rare known pathogenic mutations in the GRN and PSEN2 genes and eleven unknown-impact mutations in the GRN, VCP, MAPT, FUS, TREM2, and NOTCH3 genes. Six patients were carriers of only common risk variants (APOE and PRNP), and one did not show any risk mutation/variant. Overall, 69% (n = 9) of our early onset Alzheimer’s disease (EAOD) patients, compared with 34% (n = 13) of sporadic late onset Alzheimer’s disease (LOAD) patients and 27% (n = 73) of non-affected controls (ADNI, whole genome data), were carriers of at least two rare/common risk variants in the analyzed candidate genes panel, excluding the full penetrant mutations.

Conclusion:

This study suggests that EOD patients without full penetrant mutations are characterized by higher probability to carry polygenic risk alleles that patients with LOAD forms. This finding is in line with recently reported evidence, thus suggesting that the genetic risk factors identified in LOAD might modulate the risk also in EOAD.

Genetic Study of Alzheimer's Disease in Saudi Population

BACKGROUND

Alzheimer's disease (AD) is a chronic neurological disorder associated with mental decline and dementia. Several studies focused on investigating the molecular basis of the disease that led to the identification of several causative genes and risk associated alleles. Replication of these studies and findings from different populations is very important.

OBJECTIVE

Molecular assessment of a cohort of 117 familial and sporadic AD cases from Saudi Arabia.

METHODS

Comprehensive screening for point mutations was carried out by direct sequencing of coding regions in the three known AD causative genes: PSEN1, PSEN2, APP, as well as the AD associated gene SORL1. All patients were also genotyped for APOE alleles. In silico 3D protein structure analysis was performed for two novel SORL1 variants.

RESULTS

We identified a total of eight potential pathogenic missense variants in all studied genes. Five of these variants were not previously reported including four in SORL1 (p.Val297Met, p.Arg1084Cys, p.Asp1100Asn, and p.Pro1213Ser) and one in APP (p.Glu380Lys). The frequency of APOE-ɛ4 allele was 21.37% of total investigated cases. In silico 3D protein structure analysis of two SORL1 novel missense variants (p.Pro1213Ser and p.Arg1084Cys) suggested that these variants may affect the folding of the proteins and disturb their structure.

CONCLUSIONS

Our comprehensive analysis of the open reading frame of the known genes have identified potential pathogenic rare variants in 18/117 cases. We found that point mutations in AD main genes (PSEN1, PSEN2, and APP) were underrepresented in our cohort of patients. Our results confirm involvement of SORL1 in familial and sporadic AD cases.

Pathogenic PSEN1 Glu184Gly Mutation in a Family from Thailand with Probable Autosomal Dominant Early Onset Alzheimer's Disease

A pathogenic mutation in PSEN1 p.Glu184Gly was discovered in a Thai family with early onset Alzheimer's disease (EOAD) as the first case in Asia. Proband patient presented memory impairment and anxiety at the age of 41 years. Family history was positive, since several family members were also diagnosed with dementia (father and grandfather). MRI in the patient revealed global cortical atrophy without specific lesions or lacuna infarctions. Extensive genetic profiling for 50 neurodegenerative disease related genes was performed by next generation sequencing (NGS) on the patient. PSEN1 Glu184Gly was previously reported in French families with frontal variant Alzheimer's disease (AD). Interestingly, this mutation is located near the splicing site and could possibly result in abnormal cleavage of PSEN1 transcript. Furthermore, 3D models from protein structural predictions revealed significant structural changes, since glycine may result in increased flexibility of TM-III helix. Inter/intra-helical interactions could also be altered. In the future, functional studies should be performed to verify the probable role PSEN1 Glu184Gly in amyloid beta processing and pathogenicity.