Genetic aspects of Alzheimer disease

The Critical Role of Nurr1 as a Mediator and Therapeutic Target in Alzheimer's Disease-related Pathogenesis

Several studies have revealed that the transcription factor nuclear receptor related 1 (Nurr1) plays several roles not only in the regulation of gene expression related to dopamine synthesis, but also in alternative splicing, and miRNA targeting. Moreover, it regulates cognitive functions and protects against inflammation-induced neuronal death. In particular, the role of Nurr1 in the pathogenesis of Parkinson’s disease (PD) has been well investigated; for example, it has been shown that it restores behavioral and histological impairments in PD models. Although many studies have evaluated the connection between Nurr1 and PD pathogenesis, the role of Nurr1 in Alzheimer’s disease (AD) remain to be studied. There have been several studies describing Nurr1 protein expression in the AD brain. However, only a few studies have examined the role of Nurr1 in the context of AD. Therefore, in this review, we highlight the overall effects of Nurr1 under the neuropathologic conditions related to AD. Furthermore, we suggest the possibility of using Nurr1 as a therapeutic target for AD or other neurodegenerative disorders.

Cognitive Health of Nonagenarians in Southern Italy: A Descriptive Analysis from a Cross-Sectional, Home-Based Pilot Study of Exceptional Longevity (Cilento Initiative on Aging Outcomes Or CIAO)

Background: Nonagenarians and centenarians (NCs) are an extremely fragile population, particularly in regard to their physical and cognitive function. The aim of this study was to define the neurocognitive profiles among 29 NCs and their 49 younger cohabitants aged 50-75 years from The Cilento Initiative on Aging Outcomes (CIAO) Pilot study in the South of Italy that had provided initial hypotheses regarding positive psychological traits related to exceptional longevity. Methods: During the home visits, lifestyle information with specific questionnaires, functional autonomy and the neuropsychological Mini Mental Scale Examination (MMSE), and the Alzheimer's Disease Assessment Scale-Cognitive (ADAS-Cog) scale were obtained by qualified study personnel. The total blood oxidative capacity was also determined by testing the reactive derivative of oxygen metabolites (d-ROM) and by the Biological Antioxidant Potential (BAP). In all individuals, the APOE genotype determination was also performed. Results: All the subjects in both groups showed high adherence to the Mediterranean Diet. None of the NCs had severe cognitive impairment, and a very low incidence of dementia was found. The data obtained on the Activities ed Instrumental Activities of Daily Living (ADL-IADL) scale showed that the majority of NCs (16/29) were autonomous in daily life activities. The comparative assessment of NCs and cohabitants showed no significant differences in the laboratory assessment of oxidative stress and APOE genotype. Conclusion: In the Cilento Region of Southern Italy, NCs seemed to have good cognitive status when compared to younger cohabitants aging 50-65 years without significant differences in oxidative stress markers or APOE genotype. These results might be related to optimal adherence to the Mediterranean diet, although other lifestyle factors and positive personality traits may also contribute to their healthy aging. Further studies on a larger population should be performed to confirm the results of this pilot study.

The Genetics of Alzheimer's Disease in the Chinese Population

Alzheimer’s disease (AD) is a neurodegenerative disease characterized by progressive cognitive dysfunction and behavioral impairment. In China, the number of AD patients is growing rapidly, which poses a considerable burden on society and families. In recent years, through the advancement of genome-wide association studies, second-generation gene sequencing technology, and their application in AD genetic research, more genetic loci associated with the risk for AD have been discovered, including KCNJ15, TREM2, and GCH1, which provides new ideas for the etiology and treatment of AD. This review summarizes three early-onset AD causative genes (APP, PSEN1, and PSEN2) and some late-onset AD susceptibility genes and their mutation sites newly discovered in China, and briefly introduces the potential mechanisms of these genetic susceptibilities in the pathogenesis of AD, which would help in understanding the genetic mechanisms underlying this devastating disease.

Rational design of novel benzisoxazole derivatives with acetylcholinesterase inhibitory and serotoninergic 5-HT4 receptors activities for the treatment of Alzheimer's disease

A rigidification strategy was applied to the preclinical candidate donecopride, an acetylcholinesterase inhibitor possessing 5-HT₄R agonist activity. Inspired by promising bioactive benzisoxazole compounds, we have conducted a pharmacomodulation study to generate a novel series of multitarget directed ligands. The chemical synthesis of the ligand was optimized and compounds were evaluated in vitro against each target and in cellulo. Structure-activity relationship was supported by docking analysis in human acetylcholinesterase binding site. Among the synthesized compounds, we have identified a novel hybrid 32a (3-[2-[1-(cyclohexylmethyl)-4-piperidyl]ethyl]-4-methoxy-1,2-benzoxazole) able to display nanomolar acetylcholinesterase inhibitory effects and nanomolar Ki for 5-HT₄R.

Shannon entropy approach reveals relevant genes in Alzheimer's disease

Alzheimer’s disease (AD) is the most common type of dementia and affects millions of people worldwide. Since complex diseases are often the result of combinations of gene interactions, microarray data and gene co-expression analysis can provide tools for addressing complexity. Our study aimed to find groups of interacting genes that are relevant in the development of AD. In this perspective, we implemented a method proposed in a previous work to detect gene communities linked to AD. Our strategy combined co-expression network analysis with the study of Shannon entropy of the betweenness. We analyzed the publicly available GSE1297 dataset, achieved from the GEO database in NCBI, containing hippocampal gene expression of 9 control and 22 AD human subjects. Co-expressed genes were clustered into different communities. Two communities of interest (composed by 72 and 39 genes) were found by calculating the correlation coefficient between communities and clinical features. The detected communities resulted stable, replicated on two independent datasets and mostly enriched in pathways closely associated with neuro-degenative diseases. A comparison between our findings and other module detection techniques showed that the detected communities were more related to AD phenotype. Lastly, the hub genes within the two communities of interest were identified by means of a centrality analysis and a bootstrap procedure. The communities of the hub genes presented even stronger correlation with clinical features. These findings and further explorations on the detected genes could shed light on the genetic aspects related with physiological aspects of Alzheimer’s disease.

Inhibition of acetylcholinesterase activity and β-amyloid oligomer formation by 6-bromotryptamine A, a multi-target anti-Alzheimer's molecule

Alzheimer's disease (AD) is a neurodegenerative disorder characterized by learning and memory impairments. Recent studies have suggested that AD can be induced by multiple factors, such as cholinergic system dysfunction and β-amyloid (Aβ) neurotoxicity. It was reported that 6-bromo-N-propionyltryptamine could treat neurological diseases, including AD. In the present study, 6-bromotryptamine A, a derivative of 6-bromo-N-propionyltryptamine, was synthesized by the condensation of 2-(6-bromo-1H-indol-3-yl)ethan-1-amine and 2-(4-bromophenyl)acetic acid, and was used as a potential anti-AD molecule. Furthermore, scopolamine can induce impairments of learning and memory, and was widely used to establish AD animal models. The results demonstrated that 6-bromotryptamine A significantly prevented scopolamine-induced short-term cognitive impairments, as revealed by various behavioral tests in mice. Furthermore, an acetylcholinesterase (AChE) activity assay revealed that 6-bromotryptamine A directly inhibited AChE activity. Notably, it was observed that 6-bromotryptamine A blocked the formation of Aβ oligomer, as evaluated by the dot blot assay. All these results suggested that 6-bromotryptamine A may be used to prevent impairments in short-term learning and memory ability possibly via the inhibition of AChE and the blockade of Aβ oligomer formation.

Ghrelin in Alzheimer's disease: Pathologic roles and therapeutic implications

Ghrelin, which has many important physiological roles, such as stimulating food intake, regulating energy homeostasis, and releasing insulin, has recently been studied for its roles in a diverse range of neurological disorders. Despite the several functions of ghrelin in the central nervous system, whether it works as a therapeutic agent for neurological dysfunction has been unclear. Altered levels and various roles of ghrelin have been reported in Alzheimer's disease (AD), which is characterized by the accumulation of misfolded proteins resulting in synaptic loss and cognitive decline. Interestingly, treatment with ghrelin or with the agonist of ghrelin receptor showed attenuation in several cases of AD-related pathology. These findings suggest the potential therapeutic implications of ghrelin in the pathogenesis of AD. In the present review, we summarized the roles of ghrelin in AD pathogenesis, amyloid beta (Aβ) homeostasis, tau hyperphosphorylation, neuroinflammation, mitochondrial deficit, synaptic dysfunction and cognitive impairment. The findings from this review suggest that ghrelin has a novel therapeutic potential for AD treatment. Thus, rigorously designed studies are needed to establish an effective AD-modifying strategy.

GSK-3β and ERK1/2 incongruously act in tau hyperphosphorylation in SPS-induced PTSD rats

Post-traumatic stress disorder (PTSD) manifests in neurocognitive deficits in association with increased tau deposition, which mainly consist of phosphorylated tau in Alzheimer disease (AD) brain. However, the exact mechanism of PTSD inducing tau hyperphosphorylation remains unclear and therefore no effective treatment options are currently available. We here show that employing single prolonged stress (SPS), as a consensus PTSD model, induced a typical anxiety and abnormal hyperphosphorylation of tau at Ser202/Thr205 (AT8) and Ser404 but not at Ser199 and Ser396 in the hippocampus compared to the control rats. Furthermore, there was a decrease in the level of inactivated phosphorylated GSK-3β at Ser9, an increase in the level of activated phosphorylated GSK-3β at Thr216 and an obvious decrease in the level of activated phosphorylated ERK1/2, but no alterations in CaMKII and PP2A in hippocampus of SPS rats. On the other hand, the levels of both phosphorylated AKT and total SGK1, stress- and GSK-3β/ERK1/2-related proteins, were down-regulated. Interestingly, Overexpression of SGK1 increased the level of phosphorylated ERK1/2 and led to tau hyperphosphorylation at Ser199 and Ser396. These findings suggest that SPS exposure results in differential tau phosphorylation at different sites probably due to incongruous action between AKT-related GSK-3β activation and SGK1-related ERK1/2 inactivation, suggesting a link between SPS-induced PTSD and AD-associated tau pathogenic mechanisms.

Computational insight into the anticholinesterase activities and electronic properties of physostigmine analogs

Aim: Alzheimer's disease (AD) is known to be themajor cause of dementia among the elderly. The structural properties and binding interactions of the AD drug physostigmine (-)-phy, and its analogues (-)-hex and (-)-phe and (+)-phe, were examined, as well as their impact on the conformational changes of two different AD target enzymes AChE and BChE. Materials & methods: The conformational changes were studied using molecular dynamics and structural properties using Quantum mechanics. Results & conclusions: The binding free energy (ΔGbind) and the change in the free energy surface (FES) computed from the funnel metadynamics (FMD) simulation, both support the idea that inhibitors (-)-phe and (-)-hex have better binding activities toward enzyme AChE, and that (-)-phe is stronger in binding than the present AD drug (-)-phy.

A Novel Therapeutic Approach to Treat Alzheimer's Disease by Neurotrophic Support During the Period of Synaptic Compensation

Alzheimer’s disease (AD), at present, is considered an incurable disease and a major dilemma with no drug to stop or slow down its progression. Drugs that are currently available in the market are able to only transiently improve the clinical symptoms. The repeated failures in developing an effective drug has led to the suggestion that the medical intervention was probably too late to be effective since the pathology starts many years before the appearance of the clinical symptoms. Probably, at the time of the appearance of clinical symptoms the brain has undergone major neuronal and synaptic loss. Because of the uncertainty on when to use a prevention therapy, especially targeting amyloid-β (Aβ) and tau pathologies, interventions that rely on the regenerative capacity of the brain such as the modulation of the inherent neurogenesis and neuronal plasticity represent a promising therapeutic strategy. Such an approach can act both at early as well as late stages of the disease and remove the barrier of the time of intervention. In this article, we review studies mainly from our laboratory that show the merit of early intervention during the synaptic and neuronal compensation period where the brain still has the capacity to self-repair by offering neurotrophic support in reversing cognitive impairment, neuronal and synaptic deficits, Aβ, and tau pathologies and decreasing mortality in a transgenic mouse model of AD.

Binding between Prion Protein and Aβ Oligomers Contributes to the Pathogenesis of Alzheimer's Disease

A plethora of evidence suggests that protein misfolding and aggregation are underlying mechanisms of various neurodegenerative diseases, such as prion diseases and Alzheimer's disease (AD). Like prion diseases, AD has been considered as an infectious disease in the past decades as it shows strain specificity and transmission potential. Although it remains elusive how protein aggregation leads to AD, it is becoming clear that cellular prion protein (PrP^C) plays an important role in AD pathogenesis. Here, we briefly reviewed AD pathogenesis and focused on recent progresses how PrP^C contributed to AD development. In addition, we proposed a potential mechanism to explain why infectious agents, such as viruses, conduce AD pathogenesis. Microbe infections cause Aβ deposition and upregulation of PrP^C, which lead to high affinity binding between Aβ oligomers and PrP^C. The interaction between PrP^C and Aβ oligomers in turn activates the Fyn signaling cascade, resulting in neuron death in the central nervous system (CNS). Thus, silencing PrP^C expression may turn out be an effective treatment for PrP^C dependent AD.

Effect of Worry Level on Recall Memory for Odors in ApoE-ε4 Carriers and Non-Carriers

OBJECTIVE

Increased levels of worry, age, and presence of the apolipoprotein-E (ApoE)-ε4 allele are associated with the risk of developing cognitive declines and Alzheimer's disease (AD). Odor memory performance has been shown to vary as a function of age and ApoE genotype, and odor memory tests are sensitive to preclinical AD. Worry is known to influence verbal memory; however, its effects on odor memory are unknown. This study aimed to assess the relationships between worry, age, and ε4 status on odor memory.

METHOD

Worry was evaluated for young (n = 53) and older (n = 45) adults using the Penn State Worry Questionnaire. Odor memory was assessed using the California Odor Learning Test, an olfactory analogue to the California Verbal Learning Test.

RESULTS

A significant main effect of worry on long-delay free recall was found, such that increasing worry was associated with better recall across age and ε4 status. A significant interaction effect between ε4 status and worry on both short-and long-delay cued recall was found, such that across age, higher worry was associated with increased cued recall scores among ε4-negative adults, and decreased scores among ε4-positive adults.

CONCLUSIONS

Findings demonstrated that worry influences odor memory and exerts a particular effect on cued recall among ε4 carriers who are at a greater risk of developing AD. Worry is a modifiable predictor of cognitive decline and risk of dementia in aging. Future studies on the effects of treatments aimed at reducing worry (e.g., cognitive behavioral therapies for anxiety) on changes in cognitive functioning are warranted.

Association Between Periodontitis and Cognitive Impairment in Adults: A Systematic Review

Periodontitis is an oral inflammatory disease and may contribute to low-grade systemic inflammation. Based on the contribution of periodontitis to systemic inflammation and the potential role of systemic inflammation in neuroinflammation, many epidemiological studies have investigated a possible association between periodontitis and mild cognitive impairment or dementia. The purpose of this study was to evaluate the clinical/epidemiological evidence regarding the association between periodontitis and cognitive decline in adult patients. A search conducted between September and October 2018 was performed in the electronic databases PubMed, Scopus, Web of Science, The Cochrane Library, LILACS, OpenGrey, and Google Scholar, with no publication date or language restrictions. Analytical observational studies in adults (P—Participants), with (E—Exposure) and without periodontitis (C—Comparison) were included in order to determine the association between periodontitis and cognitive decline (O—Outcome). The search identified 509 references, of which eight observational studies were accorded with the eligibility criteria and evaluated. The results should, however, be interpreted cautiously due to the limited number of studies. This systematic review points to the need for further well-designed studies, such as longitudinal observational studies with control of modifiable variables, as diagnostic criteria and time since diagnosis of periodontitis and cognitive impairment, to confirm the proposed association.

Improvements of symptoms of Alzheimer`s disease by inhibition of the angiotensin system

With ageing of the global society, the frequency of ageing-related neurodegenerative diseases such as Alzheimer`s disease (AD) is on the rise worldwide. Currently, there is no cure for AD, and the four drugs approved for AD only have very small effects on AD symptoms. Consequently, there are enormous efforts worldwide to identify new targets for treatment of AD. Approaches that interfere with classical neuropathologic features of AD, such as extracellular senile plaques formed of aggregated amyloid-beta (Abeta), and intracellular neurofibrillary tangles of hyperphosphorylated tau have not been successful so far. In search for a treatment approach of AD, we found that inhibition of the angiotensin-converting enzyme (ACE) by a centrally acting ACE inhibitor retards symptoms of neurodegeneration, Abeta plaque formation and tau hyperphosphorylation in experimental models of AD. Our approach is currently being investigated in a clinical setting. Initial evidence with AD patients shows that a brain-penetrating ACE inhibitor counteracts the process of neurodegeneration and dementia. Moreover, centrally acting ACE inhibitors given in addition to the standard therapy, cholinesterase inhibition, can improve cognitive function of AD patients for several months. This is one of the most promising results for AD treatment since more than a decade.

Subacute to chronic Alzheimer-like alterations after controlled cortical impact in human tau transgenic mice

Repetitive traumatic brain injury (TBI) has been linked to late life development of chronic traumatic encephalopathy (CTE), a neurodegenerative disorder histopathologically characterized by perivascular tangles of hyperphosphorylated tau at the depth of sulci to later widespread neurofibrillary pathology. Although tau hyperphosphorylation and neurofibrillary-like pathology have been observed in the brain of transgenic mice overexpressing human tau with aggregation-prone mutation after TBI, they have not been consistently recapitulated in rodents expressing wild-type tau only. Here, we characterized Alzheimer-like alterations behaviorally, biochemically and immunohistochemically 6 weeks and 7 months after unilateral mild-to-moderate controlled cortical impact (CCI) in 5–7-month-old Tg/htau mice, which express all six isoforms of non-mutated human tau in a mouse tau null background. We detected hyperphosphorylation of tau at multiple sites in ipsilateral hippocampus 6 weeks but not 7 months after CCI. However, neuronal accumulation of AT8 positive phospho-tau was sustained in the chronic phase, in parallel to prolonged astrogliosis, and decreased neural and synaptic markers. The mice with CCI also exhibited cognitive and locomotor impairment. These results indicate subacute to chronic Alzheimer-like alterations after CCI in Tg/htau mice. This is the first known study providing insight into the role of CCI in Alzheimer-like brain alterations in young adult mice expressing only non-mutated human tau.

Genome-wide analysis of genetic predisposition to Alzheimer's disease and related sex disparities

BACKGROUND

Alzheimer's disease (AD) is the most common cause of dementia in the elderly and the sixth leading cause of death in the United States. AD is mainly considered a complex disorder with polygenic inheritance. Despite discovering many susceptibility loci, a major proportion of AD genetic variance remains to be explained.

METHODS

We investigated the genetic architecture of AD in four publicly available independent datasets through genome-wide association, transcriptome-wide association, and gene-based and pathway-based analyses. To explore differences in the genetic basis of AD between males and females, analyses were performed on three samples in each dataset: males and females combined, only males, or only females.

RESULTS

Our genome-wide association analyses corroborated the associations of several previously detected AD loci and revealed novel significant associations of 35 single-nucleotide polymorphisms (SNPs) outside the chromosome 19q13 region at the suggestive significance level of p < 5E-06. These SNPs were mapped to 21 genes in 19 chromosomal regions. Of these, 17 genes were not associated with AD at genome-wide or suggestive levels of associations by previous genome-wide association studies. Also, the chromosomal regions corresponding to 8 genes did not contain any previously detected AD-associated SNPs with p < 5E-06. Our transcriptome-wide association and gene-based analyses revealed that 26 genes located in 20 chromosomal regions outside chromosome 19q13 had evidence of potential associations with AD at a false discovery rate of 0.05. Of these, 13 genes/regions did not contain any previously AD-associated SNPs at genome-wide or suggestive levels of associations. Most of the newly detected AD-associated SNPs and genes were sex specific, indicating sex disparities in the genetic basis of AD. Also, 7 of 26 pathways that showed evidence of associations with AD in our pathway-bases analyses were significant only in females.

CONCLUSIONS

Our findings, particularly the newly discovered sex-specific genetic contributors, provide novel insight into the genetic architecture of AD and can advance our understanding of its pathogenesis.

Relationship between long non-coding RNAs and Alzheimer's disease: a systematic review

Alzheimer disease (AD), is a typical progressive and destructive neurodegenerative disease. It is the leading cause of senile dementia that is mainly represented as neurocognitive symptoms, including progressive memory impairment, cognitive disorder, personality change and language barrier, etc. The pathogeny and nosogenesis of AD have not been clearly explained. AD is characterized by extracellular senile plaques (SP) formed by beta amyloid (Aβ) deposition and neurofibrillary tangles in neuronal cells formed by hyperphosphorylation of tau, as well as the deficiency of neuronal with gliosis. However, the complete spectrum of regulating factors in molecular level that affect the pathogenesis of AD is unclear. Long non-coding RNAs (lncRNAs) are involved in numerous neurodegenerative diseases, such as Parkinson's disease (PD) and AD. It is increasingly recognized that lncRNAs is tightly related to the pathogenesis and prevention and cure of AD. In the review, we highlighted the roles of lncRNAs in AD pathways and discussed increasing interest in targeting and regulating lncRNAs for the therapeutics of AD.

Clinical implications of APOE genotyping for late-onset Alzheimer's disease (LOAD) risk estimation: a review of the literature

Alzheimer's disease is a genetically complex neurodegenerative disorder representing the leading cause of dementia. Advances in personal genomics are increasing the public uptake of genetic susceptibility testing for complex diseases such as late-onset Alzheimer's disease (LOAD). For LOAD, the discovery of the major risk ε4 allele of the APOE gene has prompted a debate on the ethics and utility of presymptomatic (i.e., predictive) testing. Although the mechanistic contribution of APOE to disease onset remains uncertain, presymptomatic genetic testing provides a relative risk of developing LOAD. Presymptomatic testing for complex disorders, such as LOAD is much less conclusive than early-onset Alzheimer's disease (EOAD) which follows a Mendelian inheritance pattern. Given the lack of preventive strategies available for EOAD or LOAD, APOE genotyping offers limited clinical utility, thus, raising ethical and practical questions. We conducted a systematic search of five electronic databases or primary studies published during January 2008-January 2018 which investigated practical and ethical issues of presymptomatic APOE genotyping for LOAD risk estimation. We identified 31 articles which suggested that APOE genotyping for LOAD susceptibility provides potential benefits to at-risk patients and can guide changes in positive health-related behaviors. However, other individuals may experience test-related anxiety, depression and psychological distress. Future research should focus on developing an integrated risk assessment tool to enhance the utility of APOE genotyping. Furthermore, empirical research is required to understand actual psychological and social implications associated with testing.

Genetic underpinnings in Alzheimer's disease - a review

In this review, we discuss the genetic etiologies of Alzheimer's disease (AD). Furthermore, we review genetic links to protein signaling pathways as novel pharmacological targets to treat AD. Moreover, we also discuss the clumps of AD-m ediated genes according to their single nucleotide polymorphism mutations. Rigorous data mining approaches justified the significant role of genes in AD prevalence. Pedigree analysis and twin studies suggest that genetic components are part of the etiology, rather than only being risk factors for AD. The first autosomal dominant mutation in the amyloid precursor protein (APP) gene was described in 1991. Later, AD was also associated with mutated early-onset (presenilin 1/2, PSEN1/2 and APP) and late-onset (apolipoprotein E, ApoE) genes. Genome-wide association and linkage analysis studies with identified multiple genomic areas have implications for the treatment of AD. We conclude this review with future directions and clinical implications of genetic research in AD.

Phyto-Therapeutic and Nanomedicinal Approaches to Cure Alzheimer's Disease: Present Status and Future Opportunities

Alzheimer's disease (AD) is characterized by cognitive inability manifested due to the accumulation of β-amyloid, formation of hyper phosphorylated neurofibrillary tangles, and a malfunctioned cholinergic system. The degeneration integrity of the neuronal network can appear long after the onset of the disease. Nanotechnology-based interventions have opened an exciting area via theranostics of AD in terms of tailored nanomedicine, which are able to target and deliver drugs across the blood-brain barrier (BBB). The exciting interface existing between medicinal plants and nanotechnology is an emerging marvel in medicine, which has delivered promising results in the treatment of AD. In order to assess the potential applications of the medicinal plants, their derived components, and various nanomedicinal approaches, a review of literature was deemed as necessary. In the present review, numerous phytochemicals and various feats in nanomedicine for the treatment of AD have been discussed mechanistically for the first time. Furthermore, recent trends in nanotechnology such as green synthesis of metal nanoparticles with reference to the treatment of AD have been elaborated. Foreseeing the recent progress, we hope that the interface of medicinal plants and nanotechnology will lead to highly effective theranostic strategies for the treatment of AD in the near future.

Features and outcomes of drugs for combination therapy as multi-targets strategy to combat Alzheimer's disease

ETHNOPHARMACOLOGICAL RELEVANCE

Alzheimer's disease (AD), a deleterious neurodegenerative disorder that impairs memory, cognitive functions and may lead to dementia in late stage of life. The pathogenic cause of AD remains incompletely understood and FDA approved drugs are partial inhibitors rather than curative. Most of drugs are synthetic or natural products as galanthamine is an alkaloid obtained from Galanthus spp. Huperzine A, an alkaloid found in Huperzia spp., gingkolides a diterpenoids from Gingko biloba and many ethnobotanicals like Withania somnifera (L.) Dunal., Physostigma venenosum Balf., Bacopa monnieri (L.) Wettst., Centella asiatica (L.) Urb. have been used by traditional Indian, Chinese, and European system of medicines in AD. Clinical significance opioid alkaloid in Papaver somniferum has shown another dimension to this study. Over exploitation of medicinal plants with limited bioactive principles has provided templates to design synthetic drugs in AD e.g. rivastigmine, phenserine, eptastigmine based on chemical structure of physostigmine of Physostigma venenosum Balf. Even ZT-1 a prodrug of Hup A and memogain a prodrug of galantamine has achieved new direction in drug development in AD. All these first-line cholinesterase-inhibitors are used as symptomatic treatments in AD. Single modality of "One-molecule-one-target" strategy for treating AD has failed and so future therapies on "Combination-drugs-multi-targets" strategy (CDMT) will need to address multiple aspects to block the progression of pathogenesis of AD. Besides, cholinergic and amyloid drugs, in this article we summarize proteinopathy-based drugs as AD therapeutics from a variety of biological sources. In this review, an attempt has been made to elucidate the molecular mode of action of various plant products, and synthetic drugs investigated in various preclinical and clinical tests in AD. It also discusses current attempts to formulate a comprehensive CDMT strategy to counter complex pathogenesis in AD.

MATERIALS AND METHODS

Information were collected from classical books on medicinal plants, pharmacopoeias and scientific databases like PubMed, Scopus, GoogleScholar, Web of Science and electronic searches were performed using Cochrane Library, Medline and EMBASE. Also published scientific literatures from Elsevier, Taylor and Francis, Springer, ACS, Wiley publishers and reports by government bodies and documentations were assessed.

RESULTS

60 no. of natural and synthetic drugs have been studied with their significant bioactivities. A decision matrix designed for evaluation of drugs for considering to the hypothetic "CDMT" strategy in AD. We have introduced the scoring pattern of individual drugs and based on scoring pattern, drugs that fall within the scoring range of 18-25 are considered in the proposed CDMT. It also highlights the importance of available natural products and in future those drugs may be considered in CDMT along with the qualified synthetic drugs.

CONCLUSION

A successful validation of the CDMT strategy may open up a debate on health care reform to explore other possibilities of combination therapy. In doing so, it should focus on clinical and molecular relationships between AD and CDMT. A better understanding of these relationships could inform and impact future development of AD-directed treatment strategies. This strategy also involves in reducing costs in treatment phases which will be affordable to a common man suffering from AD.

Bayesian Cox Proportional Hazards Model in Survival Analysis of HACE1 Gene with Age at Onset of Alzheimer's Disease

Alzheimer's disease (AD), the most common form of dementia, is a chronic neurodegenerative disease. The HECT domain and ankyrin repeat containing E3 ubiquitin protein ligase 1 (HACE1) gene is expressed in human brain and may play a role in the pathogenesis of neurodegenerative disorders. Till now, no previous study has reported the association of the HACE1 gene with the risk and age at onset (AAO) of AD; while few studies have checked the proportional hazards assumption in the survival analysis of AAO of AD using Cox proportional hazards model. In this study, we examined the associations of 14 single nucleotide polymorphisms (SNPs) in the HACE1 gene with the risk and the AAO of AD using 791 AD patients and 782 controls. Multiple logistic regression model identified one SNP (rs9499937 with p = 1.8×10^-3) to be associated with the risk of AD. For survival analysis of AAO, both classic Cox regression model and Bayesian survival analysis using the Cox proportional hazards model were applied to examine the association of each SNP with the AAO. The hazards ratio (HR) with its 95% confidence interval (CI) was estimated. Survival analysis using the classic Cox regression model showed that 4 SNPs were significantly associated with the AAO (top SNP rs9499937 with HR=1.33, 95%CI=1.13-1.57, p=5.0×10^-4). Bayesian Cox regression model showed similar but a slightly stronger associations (top SNP rs9499937 with HR=1.34, 95%CI=1.11-1.55) compared with the classic Cox regression model. Using an independent family-based sample, one SNP rs9486018 was associated with the risk of AD (p=0.0323) and the T-T-G haplotype from rs9786015, rs9486018 and rs4079063 showed associations with both the risk and AAO of AD (p=2.27×10^-3 and 0.0487, respectively). The findings of this study provide first evidence that several genetic variants in the HACE1 gene were associated with the risk and AAO of AD.

An exploratory investigation of brain-selective estrogen treatment in males using a mouse model of Alzheimer's disease

Estrogens are neuroprotective, and studies suggest that they may mitigate the pathology and symptoms of Alzheimer's disease (AD) in female models. However, central estrogen effects have not been examined in males in the context of AD. The purpose of this follow-up study was to assess the benefits of a brain-selective 17β-estradiol estrogen prodrug, 10β,17β-hydroxyestra-1,4-dien-3-one (DHED), also in the male APPswe/PS1dE9 double-transgenic mouse model of the disease. After continuously exposing 6-month old animals to DHED for two months, their brains showed decreased amyloid precursor and amyloid-β protein levels. The DHED-treated APPswe/PS1dE9 double transgenic subjects also exhibited enhanced performance in a cognitive task, while 17β-estradiol treatment did not reach statistical significance. Taken together, data presented here suggest that DHED may also have therapeutic benefit in males and warrant further investigations to fully elucidate the potential of targeted estrogen therapy for a gender-independent treatment of early-stage AD.

Novel Mutation (Gly212Val) in the PS2 Gene Associated with Early-Onset Familial Alzheimer's Disease

Mutations in the presenilin 2 gene (PS2) are an extremely rare cause of early-onset autosomal dominant Alzheimer's disease (AD), accounting for only 5% of these families. These cases represent a particular model of AD, and the scarcity of reports on their clinical phenotypes makes them of great interest. We report a family with early-onset autosomal dominant AD in four members, where the two living siblings were found to carry the novel PS2 mutation Gly212Val (exon 7, transmembrane domain IV) with highly predicted pathogenicity. Age at onset ranged from 60 to 65 years and three of the cases died between ages 74 and 76 years. Clinical phenotype was quite homogeneous among affected members of the family, and overall features, including cognitive decline, tau/p-tau and amyloid-β cerebrospinal fluid markers, neuroimaging, and neuropathology were consistent with typical AD. Lewy bodies were present but restricted to the amygdala.

Potential Link Between Proprotein Convertase Subtilisin/Kexin Type 9 and Alzheimer's Disease

Alzheimer's disease [AD] is not only the most common neurodegenerative disease but is also currently incurable. Proprotein convertase subtilisin/kexin-9 [PCSK9] is an indirect regulator of plasma low density lipoprotein [LDL] levels controlling LDL receptor expression at the plasma membrane. PCSK9 also appears to regulate the development of glucose intolerance, insulin resistance, abdominal obesity, inflammation, and hypertension, conditions that have been identified as risk factors for AD. PCSK9 levels also depend on age, sex, and ethnic background, factors associated with AD. Herein, we will review indirect evidence that suggests a link between PCSK9 levels and AD.

Analysis of PTPRK polymorphisms in association with risk and age at onset of Alzheimer's disease, cancer risk, and cholesterol

The human receptor-type protein-tyrosine phosphatase kappa (PTPRK) gene is highly expressed in human brain and was previously associated with an increased risk of neuropsychiatric disorders and cancer. This study investigated the association of 52 single nucleotide polymorphisms (SNPs) in PTPRK with the risk and age at onset (AAO) of Alzheimer's disease (AD) in 791 AD patients and 782 controls. Our data analysis showed that five SNPs (top SNP rs4895829 with p = 0.0125) were associated with the risk of AD based on a multiple logistic regression (p < 0.05); while six SNPs (top SNP rs1891150 with p = 8.02 × 10^-6) were associated with AAO by using a multiple linear regression analysis. Interestingly, rs2326681 was associated with both the risk and AAO of AD (p = 4.65 × 10^-2 and 5.18 × 10^-3, respectively). In a replication study, the results from family-based association test - generalized estimating equation (GEE) statistics and Wilcoxon test showed that seven SNPs were associated with the risk of AD (top SNP rs11756545 with p = 1.02 × 10^-2) and 12 SNPs were associated with the AAO (top SNP rs11966128 with p = 1.39 × 10^-4), respectively. One additional sample showed that four SNPs were associated with risk of cancer (top SNP rs1339197 with p = 4.1 × 10^-3), 12 SNPs associated with LDL-cholesterol (top SNP rs4544930 with p = 3.47 × 10^-3), and eight SNPs associated with total cholesterol (top SNP rs1012049 with p = 6.09 × 10^-3). In addition, the AD associated rs4895829 was associated with the gene expression level in the cerebellum (p = 7.3 × 10^-5). The present study is the first study providing evidence of several genetic variants within the PTPRK gene associated with the risk and AAO of AD, risk of cancer, LDL and total cholesterol levels.

Diabetes Mellitus and Alzheimer's Disease: The Protection of Epigallocatechin-3-gallate in Streptozotocin Injection-Induced Models

Diabetes mellitus is considered as a risk factor of Alzheimer’s disease (AD), the front runner of neurodegenerative disorders. Streptozotocin (STZ) is a toxin for pancreatic β-cell, which can construct a model of insulin deficient diabetes through intraperitoneal or intravenous injection. A model generated by intracerebroventricular STZ (icv-STZ) also shows numerous aspects of sporadic AD. The protective roles of tea polyphenols epigallocatechin-3-gallate (EGCG) on both two diseases were researched by some scientists. This review highlights the link between diabetes and AD and recent studies on STZ injection-induced models, and also discusses the protection of EGCG to clarify its treatment in STZ-induced diabetes and AD.

Family-based association analysis of NAV2 gene with the risk and age at onset of Alzheimer's disease

The neuron navigator 2 (NAV2) gene is highly expressed in brain and involved in the nervous system development and may play a role in Alzheimer's disease (AD). We aimed to investigate the associations of 317 single-nucleotide polymorphisms (SNPs) in the NAV2 gene with the risk and age at onset (AAO) of AD using a family-based sample (1266 AD cases and 1279 healthy relatives). Association with the risk of AD was assessed using family-based association test -generalized estimating equations (FBAT- GEE) statistics while the association with AAO as a quantitative trait was evaluated using the FBAT-Wilcoxon statistic. Single marker analysis showed that 20 SNPs were significantly associated with the risk of AD (top SNP rs7112354 with p=8.46×10-4) and 11 SNPs were associated with AAO (top SNP rs1354269 with p=2.87×10-3). Interestingly, two SNPs rs17614100 and rs12364788 were associated with both the risk (p=1.7×10-2 and 2.71×10-2; respectively) and AAO (p=1.85×10-3 and 6.06×10-3; respectively). Haplotype analyses further supported the results of single marker analyses. In addition, functional analysis showed that NAV2 mRNA had significant expression across ten human brain regions examined and significantly correlated with APOE expression in four of ten regions. The present study is the first study providing evidence of several genetic variants within the NAV2 gene influencing the risk and AAO of AD.

Early-Onset Alzheimer Disease and Candidate Risk Genes Involved in Endolysosomal Transport

Importance

Mutations in APP, PSEN1, and PSEN2 lead to early-onset Alzheimer disease (EOAD) but account for only approximately 11% of EOAD overall, leaving most of the genetic risk for the most severe form of Alzheimer disease unexplained. This extreme phenotype likely harbors highly penetrant risk variants, making it primed for discovery of novel risk genes and pathways for AD.

Objective

To search for rare variants contributing to the risk for EOAD.

Design, Setting, and Participants

In this case-control study, whole-exome sequencing (WES) was performed in 51 non-Hispanic white (NHW) patients with EOAD (age at onset <65 years) and 19 Caribbean Hispanic families previously screened as negative for established APP, PSEN1, and PSEN2 causal variants. Participants were recruited from John P. Hussman Institute for Human Genomics, Case Western Reserve University, and Columbia University. Rare, deleterious, nonsynonymous, or loss-of-function variants were filtered to identify variants in known and suspected AD genes, variants in multiple unrelated NHW patients, variants present in 19 Hispanic EOAD WES families, and genes with variants in multiple unrelated NHW patients. These variants/genes were tested for association in an independent cohort of 1524 patients with EOAD, 7046 patients with late-onset AD (LOAD), and 7001 cognitively intact controls (age at examination, >65 years) from the Alzheimer's Disease Genetics Consortium. The study was conducted from January 21, 2013, to October 13, 2016.

Main Outcomes and Measures

Alzheimer disease diagnosed according to standard National Institute of Neurological and Communicative Disorders and Stroke and the Alzheimer Disease and Related Disorders Association criteria. Association between Alzheimer disease and genetic variants and genes was measured using logistic regression and sequence kernel association test-optimal gene tests, respectively.

Results

Of the 1524 NHW patients with EOAD, 765 (50.2%) were women and mean (SD) age was 60.0 (4.9) years; of the 7046 NHW patients with LOAD, 4171 (59.2%) were women and mean (SD) age was 77.4 (8.6) years; and of the 7001 NHW controls, 4215 (60.2%) were women and mean (SD) age was 77.4 (8.6) years. The gene PSD2, for which multiple unrelated NHW cases had rare missense variants, was significantly associated with EOAD (P = 2.05 × 10-6; Bonferroni-corrected P value [BP] = 1.3 × 10-3) and LOAD (P = 6.22 × 10-6; BP = 4.1 × 10-3). A missense variant in TCIRG1, present in a NHW patient and segregating in 3 cases of a Hispanic family, was more frequent in EOAD cases (odds ratio [OR], 2.13; 95% CI, 0.99-4.55; P = .06; BP = 0.413), and significantly associated with LOAD (OR, 2.23; 95% CI, 1.37-3.62; P = 7.2 × 10-4; BP = 5.0 × 10-3). A missense variant in the LOAD risk gene RIN3 showed suggestive evidence of association with EOAD after Bonferroni correction (OR, 4.56; 95% CI, 1.26-16.48; P = .02, BP = 0.091). In addition, a missense variant in RUFY1 identified in 2 NHW EOAD cases showed suggestive evidence of an association with EOAD as well (OR, 18.63; 95% CI, 1.62-213.45; P = .003; BP = 0.129).

Conclusions and Relevance

The genes PSD2, TCIRG1, RIN3, and RUFY1 all may be involved in endolysosomal transport-a process known to be important to development of AD. Furthermore, this study identified shared risk genes between EOAD and LOAD similar to previously reported genes, such as SORL1, PSEN2, and TREM2.

Effects of Renal Impairment on Steady-State Plasma Concentrations of Rivastigmine: A Population Pharmacokinetic Analysis of Capsule and Patch Formulations in Patients with Alzheimer's Disease

Introduction

The glomerular filtration rate (GFR), a measure of renal function, decreases by approximately 10 mL/min every 10 years after the age of 40 years, which could lead to the accumulation of drugs and/or renal toxicity. Pharmacokinetic studies of drugs excreted both renally and non-renally are desirable in patients with impaired renal function, defined by parameters including estimated GFR (eGFR) and creatinine clearance (CL_CR).

Objective

We describe here a population pharmacokinetic analysis of the possible effects of renal impairment on steady-state plasma concentrations of rivastigmine and its metabolite NAP226-90 after rivastigmine patch (5 cm² [4.6 mg/24 h], 10 cm² [9.5 mg/24 h], 15 cm² [13.3 mg/24 h], and 20 cm² [17.4 mg/24 h]) and capsule (1.5, 3, 4.5, and 6 mg/12 h) treatment in patients with Alzheimer’s disease.

Methods

The data used to conduct the current pharmacokinetic analysis were obtained from the pivotal phase III, 24-week, multicenter, randomized, double-blind, placebo- and active-controlled, parallel-group study (IDEAL). One blood sample was collected from each patient at steady-state to measure plasma concentrations of rivastigmine and NAP226-90 using a liquid chromatography–tandem mass spectrometry (LC–MS/MS) method. The steady-state plasma concentrations of rivastigmine and NAP226-90 were plotted against CL_CR and eGFR data, and boxplots were constructed after stratification by renal function.

Results

The two groups (mild/no renal impairment vs. moderate/severe/end-stage renal impairment) showed comparable demographic covariates for all patch sizes and capsule doses. No correlation was observed between CL_CR or eGFR and plasma concentrations of rivastigmine or NAP226-90. Boxplots of concentrations of rivastigmine or NAP226-90 for each dose largely overlapped for patch and capsule. Additionally, model-based estimates of plasma concentrations adjusted for body weight yielded similar results.

Conclusion

The results of this study show that renal function does not affect rivastigmine or NAP226-90 steady-state plasma concentrations, and no dose adjustment in patients with renal impairment is required.

ClinicalTrials.gov

NCT00099242.

NADPH oxidase contributes to streptozotocin-induced neurodegeneration

Alzheimer's disease (AD) is a neurodegenerative disorder characterized by the progressive loss of memory. The neurodegeneration induced by AD has been linked to oxidative damage. However, little is known about the involvement of NADPH oxidase 2 (Nox2), a multisubunit enzyme that catalyzes the reduction of oxygen to produce reactive oxygen species, in the pathogenesis of AD. The main purpose of this study was to investigate the involvement of Nox2 in memory, in AD-related brain abnormalities, oxidative damage, inflammation and neuronal death in the hippocampus in the streptozotocin (STZ)-induced AD-like state by comparing the effects of that drug on mice lacking gp91^phox-/- and wild-type (Wt) mice. Nox2 gene expression was found increased in Wt mice after STZ injection. In object recognition test, Wt mice injected with STZ presented impairment in short- and long-term memory, which was not observed following Nox2 deletion. STZ treatment induced increased phosphorylation of Tau and increased amyloid-β, apoptosis-inducing factor (AIF) and astrocyte and microglial markers expression in Wt mice but not in gp91^phox-/-. STZ treatment increased oxidative damage and pro-inflammatory cytokines' release in Wt mice, which was not observed in gp91^phox-/- mice. Nox2 deletion had a positive effect on the IL-10 baseline production, suggesting that this cytokine might contribute to the neuroprotection mechanism against STZ-induced neurodegeneration. In summary, our data suggest that the Nox2-dependent reactive oxygen species (ROS) generation contributes to the STZ-induced AD-like state.

Is heart disease a risk factor for low dementia test battery scores in older persons with Down syndrome? Exploratory, pilot study, and commentary

OBJECTIVES

Certain heart conditions and diseases are common in Down syndrome (DS; trisomy 21), but their role in early onset dementia that is prevalent in older adults with DS has not been evaluated. To address this knowledge gap, we conducted a study of risk factors for low neurocognitive/behavioral scores obtained with a published dementia test battery (DTB). Participants were adults with DS living in New York (N = 29; average age 46 years). We asked three questions. 1. Does having any type of heart disease affect the association between DTB scores and chronological age? 2. Does thyroid status affect the association between heart disease and DTB scores? 3. Are the E4 or E2 alleles of apolipoprotein E (APOE) associated with DTB scores or with heart disease?

METHOD

The study was retrospective, pilot, and exploratory. It involved analysis of information in a database previously established for the study of aging in DS. Participants had moderate intellectual disability on average. Information for each person included: gender, age, a single DTB score obtained by combining results from individual subscales of the DTB, the presence or absence of heart disease, thyroid status (treated hypothyroidism or normal), and APOE genotype. Trends were visualized by inspection of graphs and contingency tables. Statistical methods used to evaluate associations included Pearson correlation analysis, Fisher's exact tests (2-tailed), and odds ratio analysis. P values were interpreted at the 95% confidence level without Bonferroni correction. P values >.05<.1 were considered trends.

RESULTS

The negative correlation between DTB scores and age was significant in those with heart disease but not in those without. Heart disease was significantly associated with DTB scores >1 SD below the sample mean; there was a strong association between heart disease and low DTB scores in those with treated hypothyroidism but not in those with normal thyroid status. The APOE genotype was weakly associated with heart disease (E4, predisposing; E2, protective) in males.

CONCLUSIONS

On the basis of the potentially important findings from the present study, large prospective studies are warranted to confirm and extend the observations. In these, particular heart conditions or diseases and other medical comorbidities in individuals should be documented.

Drosophila melanogaster: Deciphering Alzheimer's Disease

Alzheimer's disease (AD) is the most widespread neurodegenerative disorder worldwide. Its pathogenesis involves two hallmarks: aggregation of amyloid beta (Aβ) and occurrence of neurofibrillary tangles (NFTs). The mechanism behind the disease is still unknown. This has prompted the use of animal models to mirror the disease. The fruit fly, Drosophila melanogaster has garnered considerable attention as an organism to recapitulate human disorders. With the ability to monopolise a multitude of traditional and novel genetic tools, Drosophila is ideal for studying not only cellular aspects but also physiological and behavioural traits of human neurodegenerative diseases. Here, we discuss the use of the Drosophila model in understanding AD pathology and the insights gained in discovering drug therapies for AD.

Modulation of APOE and SORL1 genes on hippocampal functional connectivity in healthy young adults

Apolipoprotein E (APOE) and sortilin-related receptor (SORL1) genes act on the same metabolic pathway and have been associated with Alzheimer's disease (AD) characterized by hippocampal impairment. Although the effects of APOE on hippocampal resting-state functional connectivity (rsFC) have been reported, the main effects of SORL1 and SORL1 × APOE interactions on hippocampal rsFC in healthy subjects remain largely unknown. Here, we systematically investigated the main effects of SORL1 rs2070045, and APOE, and their interaction effects on hippocampal rsFC in healthy young adults. The main effect of APOE showed that risk ε4 carriers had decreased positive hippocampal rsFC with the precuneus/posterior cingulate cortex and subgenual anterior cingulate cortex, and increased positive hippocampal rsFC with the sensorimotor cortex compared with non-ε4 carriers. The main effect of SORL1 showed that risk G-allele carriers had decreased positive rsFC between the hippocampus and middle temporal gyrus compared with TT carriers. No significant additive interaction was observed. Instead, significant SORL1 × APOE non-additive interaction was found in negative rsFC between the hippocampus and inferior frontal gyrus. Compared with subjects with TT genotype, SORL1 G-allele carriers had a stronger negative rsFC in APOE ε4 carriers, but a weaker negative rsFC in APOE non-ε4 carriers. These findings suggest that SORL1 and APOE genes modulate different hippocampal rsFCs and have a complex interaction. The SORL1- and APOE-dependent hippocampal connectivity changes may at least partly account for their association with AD.

Effects of medicinal plants on Alzheimer's disease and memory deficits

Alzheimer's disease is an age-related neurodegenerative disorder characterized by memory deficits. Various studies have been carried out to find therapeutic approaches for Alzheimer's disease. However, the proper treatment option is still not available. There is no cure for Alzheimer's disease, but symptomatic treatment may improve the memory and other dementia related problems. Traditional medicine is practiced worldwide as memory enhancer since ancient times. Natural therapy including herbs and medicinal plants has been used in the treatment of memory deficits such as dementia, amnesia, as well as Alzheimer's disease since a long time. Medicinal plants have been used in different systems of medicine, particularly Unani system of medicines and exhibited their powerful roles in the management and cure of memory disorders. Most of herbs and plants have been chemically evaluated and their efficacy has also been proven in clinical trials. However, the underlying mechanisms of actions are still on the way. In this paper, we have reviewed the role of different medicinal plants that play an important role in the treatment of Alzheimer's disease and memory deficits using conventional herbal therapy.

The Role of Reactive Oxygen Species in the Pathogenesis of Alzheimer's Disease, Parkinson's Disease, and Huntington's Disease: A Mini Review

Neurodegenerative diseases affect not only the life quality of aging populations, but also their life spans. All forms of neurodegenerative diseases have a massive impact on the elderly. The major threat of these brain diseases includes progressive loss of memory, Alzheimer's disease (AD), impairments in the movement, Parkinson's disease (PD), and the inability to walk, talk, and think, Huntington's disease (HD). Oxidative stress and mitochondrial dysfunction are highlighted as a central feature of brain degenerative diseases. Oxidative stress, a condition that occurs due to imbalance in oxidant and antioxidant status, has been known to play a vital role in the pathophysiology of neurodegenerative diseases including AD, PD, and HD. A large number of studies have utilized oxidative stress biomarkers to investigate the severity of these neurodegenerative diseases and medications are available, but these only treat the symptoms. In traditional medicine, a large number of medicinal plants have been used to treat the symptoms of these neurodegenerative diseases. Extensive studies scientifically validated the beneficial effect of natural products against neurodegenerative diseases using suitable animal models. This short review focuses the role of oxidative stress in the pathogenesis of AD, PD, and HD and the protective efficacy of natural products against these diseases.

Genetic Counseling and Testing for Alzheimer's Disease and Frontotemporal Lobar Degeneration: An Italian Consensus Protocol

BACKGROUND

Genetic testing of familial Alzheimer's disease (AD) and frontotemporal lobar degeneration (FTLD) is attracting interest thanks to innovative primary prevention clinical trials and increased request for information by at-risk individuals. However, ethical, social, and psychological implications are paramount and genetic testing must be supported by structured genetic counseling. In Italy, practice parameters and guidelines for genetic counseling in dementia are not available.

OBJECTIVE

To develop a nationally harmonized protocol for genetic counseling and testing of familial AD and FTLD.

METHODS

Activities were carried out in the context of the Italian Dominantly Inherited Alzheimer's and Frontotemporal Network (IT-DIAfN) project, a national network of centers of excellence with expertise in managing patients with familial AD and FTLD. A survey of the literature on genetic counseling protocols and guidelines was conducted. Local protocols for genetic counseling were surveyed. Differences and commonalities among protocols were identified and discussed among project partners. Consensus was reached following implicit aggregation methods.

RESULTS

Consensus was reached on a protocol for patients with clinically diagnosed familial AD or FTLD and a distinct protocol for their at-risk relatives. Genetic counseling should be provided by a multidisciplinary team including a geneticist, a neurologist/geriatrician, and a psychologist/psychiatrist, according to the following schedule: (i) initial consultation with tailored information on the genetics of the dementias; (ii) clinical, psychological, and cognitive assessment; if deemed appropriate (iii) genetic testing following a structured decision tree for gene mutation search; (iv) genetic testing result disclosure; (v) psychological support follow-up.

CONCLUSION

This genetic counseling protocol provides Italian centers with a line of shared practice for dealing with the requests for genetic testing for familial AD and FTLD from patients and at-risk relatives, who may also be eligible participants for novel prevention clinical trials.

Non-parametric Survival Analysis of EPG5 Gene with Age at Onset of Alzheimer's Disease

Non-parametric methods such as Wilcoxon test have the advantages of no assumptions for the underlying survival distributions. Alzheimer's disease (AD) is a chronic neurodegenerative disease while the ectopic P-granules autophagy protein 5 homolog (EPG5 gene) is highly expressed in human brain and may implicate in the pathogenesis of neurodegenerative disorders. The present study explored the associations of 26 single-nucleotide polymorphisms (SNPs) in the EPG5 gene with the age at onset (AAO) of AD using a family-based association test (FBAT)-Wilcoxon statistic in a family-based study. Then a replication study using a case-control sample was conducted to perform Wilcoxon test in Kaplan-Meier survival analysis of AAO. The results from FBAT-generalized estimating equations (FBAT-GEE) statistics and FBAT-Wilcoxon test showed that seven SNPs (top SNP rs495078 with p = 1.29 × 10-3) were significantly associated with the risk of AD, and eight SNPs (top SNP rs11082498 with p = 3.55 × 10-4) were associated with the AAO of AD in the family-based study (p < 0.05). In the replicated data, three SNPs were associated with AAO by using the Wilcoxon test, where the mean AAO was approximately 2.2 years earlier in individuals who had at least one minor allele of the top AAO-associated SNP rs9963463 (p = 0.0018) compared with those who were homozygous for the major allele. These findings from non-parametric survival analyses provide evidence for several genetic variants in EPG5 influencing the AAO of AD and will serve as a resource for replication in other populations.

Fus1 KO Mouse As a Model of Oxidative Stress-Mediated Sporadic Alzheimer's Disease: Circadian Disruption and Long-Term Spatial and Olfactory Memory Impairments

Insufficient advances in the development of effective therapeutic treatments of sporadic Alzheimer's Disease (sAD) to date are largely due to the lack of sAD-relevant animal models. While the vast majority of models do recapitulate AD's hallmarks of plaques and tangles by virtue of tau and/or beta amyloid overexpression, these models do not reflect the fact that in sAD (unlike familial AD) these genes are not risk factors per se and that other mechanisms like oxidative stress, metabolic dysregulation and inflammation play key roles in AD etiology. Here we characterize and propose the Fus1 KO mice that lack a mitochondrial protein Fus1/Tusc2 as a new sAD model. To establish sAD relevance, we assessed sAD related deficits in Fus1 KO and WT adult mice of 4-5 months old, the equivalent human age when the earliest cognitive and olfactory sAD symptoms arise. Fus1 KO mice showed oxidative stress (increased levels of ROS, decreased levels of PRDX1), disruption of metabolic homeostasis (decreased levels of ACC2, increased phosphorylation of AMPK), autophagy (decreased levels of LC3-II), PKC (decreased levels of RACK1) and calcium signaling (decreased levels of Calb2) in the olfactory bulb and/or hippocampus. Mice were behaviorally tested using objective and accurate video tracking (Noldus), in which Fus1 KO mice showed clear deficits in olfactory memory (decreased habituation/cross-habituation in the short and long term), olfactory guided navigation memory (inability to reduce their latency to find the hidden cookie), spatial memory (learning impairments on finding the platform in the Morris water maze) and showed more sleep time during the diurnal cycle. Fus1 KO mice did not show clear deficits in olfactory perception (cross-habituation), association memory (passive avoidance) or in species-typical behavior (nest building) and no increased anxiety (open field, light-dark box) or depression/anhedonia (sucrose preference) at this relatively young age. These neurobehavioral deficits of the Fus1 KO mice at this relatively young age are highly relevant to sAD, making them suitable for effective research on pharmacological targets in the context of early intervention of sAD.

Clinical characterization of an APP mutation (V717I) in five Han Chinese families with early-onset Alzheimer's disease

The missense mutation V717I in amyloid precursor protein (APP) gene has been reported in many early-onset familial Alzheimer's disease (EOFAD) families. However, no detailed clinical picture regarding this mutation has ever been described for Chinese EOFAD. We investigate the age at onset (AAO), initial clinical features and non-cognitive neurological symptoms in 34 affected subjects from five Han Chinese EOFAD families with the APPV717I mutation to characterize the clinical phenotype. The AAO was 54.7±4.9years (n=34), with the APOE ɛ4 allele correlating with a decreased AAO. Prominent early affective symptoms, executive dysfunction and disorientation at onset were exhibited in 26 (76.5%), 18 (52.9%) and 16 (47%) cases, respectively. Spastic paraparesis and cerebellar ataxia occurred frequently in 13 (38.2%) and 12 (35.3%) cases, respectively, during the late stages of disease. The specific clinical phenotype of the APPV717I mutation for Chinese families is characterized by prominent early affective symptoms, executive dysfunction and disorientation as well as frequent late spastic paraparesis and cerebellar ataxia as compared to Western reports. We conclude that ethnic differences, environment or additional unknown factors may challenge the homogeneity of EOFAD with identical APP mutations.

Genome-wide haplotype association study identify TNFRSF1A, CASP7, LRP1B, CDH1 and TG genes associated with Alzheimer's disease in Caribbean Hispanic individuals

Alzheimer's disease (AD) is an acquired disorder of cognitive and behavioral impairment. It is considered to be caused by variety of factors, such as age, environment and genetic factors. In order to identify the genetic affect factors of AD, we carried out a bioinformatic approach which combined genome-wide haplotype-based association study with gene prioritization. The raw SNP genotypes data was downloaded from GEO database (GSE33528). It contains 615 AD patients and 560 controls of Caribbean Hispanic individuals. Firstly, we identified the linkage disequilibrium (LD) haplotype blocks and performed genome-wide haplotype association study to screen significant haplotypes that were associated with AD. Then we mapped these significant haplotypes to genes and obtained candidate genes set for AD. At last, we prioritized AD candidate genes based on their similarity with 36 known AD genes, so as to identify AD related genes. The results showed that 141 haplotypes on 134 LD blocks were significantly associated with AD (P<1E-4), and these significant haplotypes were mapped to 132 AD candidate genes. After prioritizing these candidate genes, we found seven AD related genes: APOE, APOC1, TNFRSF1A, LRP1B, CDH1, TG and CASP7. Among these genes, APOE and APOC1 are known AD risk genes. For the other five genes TNFRSF1A, CDH1, CASP7, LRP1B and TG, this is the first genetic association study which showed the significant association between these five genes and AD susceptibility in Caribbean Hispanic individuals. We believe that our findings can provide a new perspective to understand the genetic affect factors of AD.

Inverse effect of the APOE epsilon4 allele in late- and early-onset Alzheimer's disease

In Alzheimer's disease patients (AD), the age at onset (AAO) ranges from 40 to 90. Usually, AD patients who develop symptoms before the age of 65 are classified as early onset (EO). The best known genetic risk factor for AD is the ε4 allele of the apolipoprotein E (APOE). In this study, 474 subjects with AD were consecutively recruited in the memory clinic of the Santa Lucia Foundation in Rome. The best fitting model  for the discrimination between EO and late onset (LO) was chosen based on lowest value of the Bayesian Information Criterion, which suggests the theoretical model with minimal deviation from the empirical distribution function of AAO in our sample. The FMM was used to compare EO and LO groups with respect to the following demographic and clinical variables: gender, age, education, MMSE and NPI. Furthermore a quantitative assessment of ADL and IADL was performed. Finally, the frequency of the APOE ε4 allele was compared in EO and LO groups. Using the admixture analysis, we established that the AAO discriminating EO from LO-AD was 63-64. Higher education was associated with earlier onset in the EO but not in LO, and duration of illness was associated with earlier onset only in LO. The ε4 allele was associated with later onset in EO but earlier onset in LO. Finally, increased impairment in ADL, IADL and NPI was associated with later onset only in the LO subgroup. Thus, the ε4 allele of the APOE gene was significantly associated with both EO and LO distributions but with opposite effect, suggesting genetic heterogeneity. Additional studies are needed to further clarify the genetic mechanisms differentiating EO- and LO-AD.

Neurotrophic factor small-molecule mimetics mediated neuroregeneration and synaptic repair: emerging therapeutic modality for Alzheimer's disease

Alzheimer's disease (AD) is an incurable and debilitating chronic progressive neurodegenerative disorder which is the leading cause of dementia worldwide. AD is a heterogeneous and multifactorial disorder, histopathologically characterized by the presence of amyloid β (Aβ) plaques and neurofibrillary tangles composed of Aβ peptides and abnormally hyperphosphorylated tau protein, respectively. Independent of the various etiopathogenic mechanisms, neurodegeneration is a final common outcome of AD neuropathology. Synaptic loss is a better correlate of cognitive impairment in AD than Aβ or tau pathologies. Thus a highly promising therapeutic strategy for AD is to shift the balance from neurodegeneration to neuroregeneration and synaptic repair. Neurotrophic factors, by virtue of their neurogenic and neurotrophic activities, have potential for the treatment of AD. However, the clinical therapeutic usage of recombinant neurotrophic factors is limited because of the insurmountable hurdles of unfavorable pharmacokinetic properties, poor blood-brain barrier (BBB) permeability, and severe adverse effects. Neurotrophic factor small-molecule mimetics, in this context, represent a potential strategy to overcome these short comings, and have shown promise in preclinical studies. Neurotrophic factor small-molecule mimetics have been the focus of intense research in recent years for AD drug development. Here, we review the relevant literature regarding the therapeutic beneficial effect of neurotrophic factors in AD, and then discuss the recent status of research regarding the neurotrophic factor small-molecule mimetics as therapeutic candidates for AD. Lastly, we summarize the preclinical studies with a ciliary neurotrophic factor (CNTF) small-molecule peptide mimetic, Peptide 021 (P021). P021 is a neurogenic and neurotrophic compound which enhances dentate gyrus neurogenesis and memory processes via inhibiting leukemia inhibitory factor (LIF) signaling pathway and increasing brain-derived neurotrophic factor (BDNF) expression. It robustly inhibits tau abnormal hyperphosphorylation via increased BDNF mediated decrease in glycogen synthase kinase-3β (GSK-3β, major tau kinase) activity. P021 is a small molecular weight, BBB permeable compound with suitable pharmacokinetics for oral administration, and without adverse effects associated with native CNTF or BDNF molecule. P021 has shown beneficial therapeutic effect in several preclinical studies and has emerged as a highly promising compound for AD drug development.