Longitudinal epidemiologic clinical-pathologic studies of aging and Alzheimer's disease

Proteomic signaling of dual specificity phosphatase 4 (DUSP4) in Alzheimer's disease

DUSP4 is a member of the DUSP (Dual-Specificity Phosphatase) subfamily that is selective to the mitogen-activated protein kinases (MAPK) and has been implicated in a range of biological processes and functions in Alzheimer's disease (AD). In this study, we utilized stereotactic delivery of adeno-associated virus (AAV)-DUSP4 to overexpress DUSP4 in the dorsal hippocampus of 5xFAD and wildtype (WT) mice, then used mass spectrometry (MS)-based proteomics along with label-free quantification to profile the proteome and phosphoproteome in the hippocampus. We identified patterns of protein expression and phosphorylation that are modulated in 5xFAD mice and examined the sex-specific impact of DUSP4 overexpression on the 5xFAD proteome/phosphoproteome. In 5xFAD mice, a substantial number of proteins were up- or down-regulated in both male and female mice in comparison to age and sex-matched WT mice, many of which are involved in AD-related biological processes, such as the activated immune response or suppression of synaptic activities. Upon DUSP4 overexpression, significantly regulated proteins were found in pathways that were suppressed, such as the immune response, in male 5xFAD mice. In contrast, such a shift was absent in female mice. For the phosphoproteome, we detected an array of phosphorylation sites that are regulated in 5xFAD compared to WT, and are modulated by DUSP4 overexpression in each sex. Interestingly, the changes in 5xFAD- and DUSP4-associated phosphorylation occurred in opposite directions. Strikingly, both the 5xFAD- and DUSP4-associated phosphorylation changes were found for the most part in neurons, and play key roles in neuronal processes and synaptic function. Site-centric pathway analysis revealed that both the 5xFAD- and DUSP4-associated phosphorylation sites were enriched for a number of kinase sets in female, but only a limited number of sets of kinases in male mice. Taken together, our results suggest that male and female 5xFAD mice respond to DUSP4 overexpression via shared and sex-specific molecular mechanisms, which might underly similar reductions in amyloid pathology in both sexes, while learning deficits were reduced in only females with DUSP4 overexpression. Finally, we validated our findings with the sex-specific AD-associated proteomes in human cohorts and further developed DUSP4-centric proteomic network models and signaling maps for each sex.

Proteomic signaling of dual specificity phosphatase 4 (DUSP4) in Alzheimer's disease

DUSP4 is a member of the DUSP (Dual-Specificity Phosphatase) subfamily that is selective to the mitogen-activated protein kinases (MAPK) and has been implicated in a range of biological processes and functions in Alzheimer's disease (AD). In this study, we utilized stereotactic delivery of adeno-associated virus (AAV)-DUSP4 to overexpress DUSP4 in the dorsal hippocampus of 5×FAD and wildtype (WT) mice, then used mass spectrometry (MS)-based proteomics along with label-free quantification to profile the proteome and phosphoproteome in the hippocampus. We identified patterns of protein expression and phosphorylation that are modulated in 5×FAD mice and examined the sex-specific impact of DUSP4 overexpression on the 5×FAD proteome/phosphoproteome. In 5×FAD mice, a substantial number of proteins were up- or down-regulated in both male and female mice in comparison to age and sex-matched WT mice, many of which are involved in AD-related biological processes, such as the activated immune response or suppression of synaptic activities. Upon DUSP4 overexpression, significantly regulated proteins were found in pathways that were suppressed, such as the immune response, in male 5×FAD mice. In contrast, such a shift was absent in female mice. For the phosphoproteome, we detected an array of phosphorylation sites that are regulated in 5×FAD compared to WT, and are modulated by DUSP4 overexpression in each sex. Interestingly, the changes in 5×FAD- and DUSP4-associated phosphorylation occurred in opposite directions. Strikingly, both the 5×FAD- and DUSP4-associated phosphorylation changes were found for the most part in neurons, and play key roles in neuronal processes and synaptic function. Site-centric pathway analysis revealed that both the 5×FAD- and DUSP4-associated phosphorylation sites were enriched for a number of kinase sets in female, but only a limited number of sets of kinases in male mice. Taken together, our results suggest that male and female 5×FAD mice respond to DUSP4 overexpression via shared and sex-specific molecular mechanisms, which might underly similar reductions in amyloid pathology in both sexes, while learning deficits were reduced in only females with DUSP4 overexpression. Finally, we validated our findings with the sex-specific AD-associated proteomes in human cohorts and further developed DUSP4-centric proteomic network models and signaling maps for each sex.

Multi-omic atlas of the parahippocampal gyrus in Alzheimer's disease

Alzheimer's disease (AD) is the most common form of dementia worldwide, with a projection of 151 million cases by 2050. Previous genetic studies have identified three main genes associated with early-onset familial Alzheimer's disease, however this subtype accounts for less than 5% of total cases. Next-generation sequencing has been well established and holds great promise to assist in the development of novel therapeutics as well as biomarkers to prevent or slow the progression of this devastating disease. Here we present a public resource of functional genomic data from the parahippocampal gyrus of 201 postmortem control, mild cognitively impaired (MCI) and AD individuals from the Mount Sinai brain bank, of which whole-genome sequencing (WGS), and bulk RNA sequencing (RNA-seq) were previously published. The genomic data include bulk proteomics and DNA methylation, as well as cell-type-specific RNA-seq and assay for transposase-accessible chromatin with high-throughput sequencing (ATAC-seq) data. We have performed extensive preprocessing and quality control, allowing the research community to access and utilize this public resource available on the Synapse platform at https://doi.org/10.7303/syn51180043.2 .

Genome-wide methylomic regulation of multiscale gene networks in Alzheimer's disease

INTRODUCTION

Recent studies revealed the association of abnormal methylomic changes with Alzheimer's disease (AD) but there is a lack of systematic study of the impact of methylomic alterations over the molecular networks underlying AD.

METHODS

We profiled genome-wide methylomic variations in the parahippocampal gyrus from 201 post mortem control, mild cognitive impaired, and AD brains.

RESULTS

We identified 270 distinct differentially methylated regions (DMRs) associated with AD. We quantified the impact of these DMRs on each gene and each protein as well as gene and protein co-expression networks. DNA methylation had a profound impact on both AD-associated gene/protein modules and their key regulators. We further integrated the matched multi-omics data to show the impact of DNA methylation on chromatin accessibility, which further modulates gene and protein expression.

DISCUSSION

The quantified impact of DNA methylation on gene and protein networks underlying AD identified potential upstream epigenetic regulators of AD.

HIGHLIGHTS

A cohort of DNA methylation data in the parahippocampal gyrus was developed from 201 post mortem control, mild cognitive impaired, and Alzheimer's disease (AD) brains. Two hundred seventy distinct differentially methylated regions (DMRs) were found to be associated with AD compared to normal control. A metric was developed to quantify methylation impact on each gene and each protein. DNA methylation was found to have a profound impact on not only the AD-associated gene modules but also key regulators of the gene and protein networks. Key findings were validated in an independent multi-omics cohort in AD. The impact of DNA methylation on chromatin accessibility was also investigated by integrating the matched methylomic, epigenomic, transcriptomic, and proteomic data.

A Longitudinal Study of Acculturation in Context and Cardiovascular Health and Their Effects on Cognition Among Older Latino Adults

Background We previously outlined the importance of considering acculturation within the context of older Latino adults' lived experience (ie, acculturation in context) to better capture contributors to cognitive aging. We now examine this conceptual framework as related to level of and change in cardiovascular health, and whether cardiovascular health modifies previously documented associations of acculturation in context with cognition. Methods and Results Acculturation in context data from 192 Latino participants without dementia at baseline (age ~70 years) were compiled into 3 separate composite scores: acculturation-related (nativity, language-, and social-based preferences), contextually related socioenvironmental (experiences of discrimination, social isolation, social networks), and familism-related (Latino-centric family ethos). A modified American Heart Association's Life's Simple 7 (mLS7; ie, smoking, physical activity, body mass index, blood pressure, total cholesterol, blood glucose) was used to measure cardiovascular health. Mixed effects regressions simultaneously tested the association of all 3 composite scores with total mLS7 adjusting for confounders. Separate models tested whether mLS7 modified associations of the 3 composite scores and cognition. The contextually related socioenvironmental composite score reflecting higher discrimination, higher social isolation, and smaller social networks (estimate=0.22, SE=0.10, P=0.02) and the familism score (estimate=0.16, SE=0.07, P=0.02) both significantly associated with change in total mLS7. The acculturation-related composite was not significantly associated with change in mLS7. No composite was significantly associated with level of mLS7. Total mLS7, however, significantly modified associations between the acculturation-related composite and change in working memory (estimate=-0.02, SE=0.01, P=0.043). Conclusions Acculturation within the context of older Latino adults' lived experience is important for maintaining cardiovascular health, relationships that also affect domain-specific cognitive decline.

White matter correlates of scam susceptibility in community-dwelling older adults

Scam susceptibility places older adults - even those with intact cognition - at great risk. Lower grey matter volumes, particularly within right medial temporal regions, are associated with higher scam susceptibility; however, very little is known about white matter associates. We investigated associations between white matter integrity measured using diffusion tensor imaging (DTI) and scam susceptibility in 302 non-demented older adults (75% female; mean years: age = 81.3 + 7.5, education = 15.7 + 2.9). Participants completed comprehensive neuroimaging (including DTI, T1- and T2-weighted imaging), a self-report measure of scam susceptibility, and neuropsychological testing. Tract-Based Spatial Statistics (TBSS) investigated associations of DTI-derived measures of fractional anisotropy (FA), trace of the diffusion tensor, axial and radial diffusivity (separately) with scam susceptibility adjusting for age, sex, education, and white matter hyperintensities (WMH; total volume and voxelwise separately). Statistical significance was determined at p < 0.05, Family Wise Error corrected. TBSS revealed significant negative associations between FA in tracts connecting a number of right hemisphere white matter regions and scam susceptibility, particularly after additional adjustment for global cognitive functioning. The pathways implicated were mainly in right temporal-parietal and temporal-occipital regions. Association of trace, axial, and radial diffusivity with scam susceptibility were not significant in fully-adjusted models. Lower white matter integrity within right hemisphere tracts was associated with higher scam susceptibility independent of relevant confounds including global cognition. Thus, a right hemisphere brain network that includes key structures implicated in multi-sensory processing of immediate and future consequences may serve as a neurobiologic substrate of scam susceptibility in vulnerable older adults.

Loneliness Interacts With Cognition in Relation to Healthcare and Financial Decision Making Among Community-Dwelling Older Adults

BACKGROUND AND OBJECTIVES

Cognition is a known determinant of healthcare and financial decision making in old age. Social vulnerabilities also might play a role in such decisions; however, the evidence for this is less clear. Here, we examined the association of loneliness with decision making and tested the hypothesis that loneliness is associated with decision making via its interaction with global cognition.

RESEARCH DESIGN AND METHODS

Participants were 1,121 nondemented older adults from the Rush Memory and Aging Project. Healthcare and financial decision making was assessed via a performance-based measure; loneliness was assessed via the De Jong Gierveld Loneliness Scale; and cognition was assessed via a 19-test neuropsychological battery.

RESULTS

In a regression model adjusted for age, sex, and education, global cognition was associated with decision making (B = 2.43, SE = 0.14, p < .001) but loneliness was not (B = -0.04, SE = 0.11, p = .72). However, in a model including the interaction of loneliness with global cognition, the interaction was significant (B = 0.44, SE = 0.20, p = .03), such that the detrimental effect of loneliness on decision making was stronger when cognition was low. In secondary analyses examining the interaction of loneliness with 5 specific cognitive domains, the interaction between loneliness and working memory with decision making was significant (B = 0.35, SE = 0.15, p = .02).

DISCUSSION AND IMPLICATIONS

Our results suggest that loneliness compromises healthcare and financial decision making among older adults with lower global cognition and, more specifically, lower working memory.

Factors associated with the onset of Alzheimer's disease: Data mining in the French nationwide discharge summary database between 2008 and 2014

INTRODUCTION

Identifying modifiable risk factors for Alzheimer's disease (AD) is critical for research. Data mining may be a useful tool for finding new AD associated factors.

METHODS

We included all patients over 49 years of age, hospitalized in France in 2008 (without dementia) and in 2014. Dependent variable was AD or AD dementia diagnosis in 2014. We recoded the diagnoses of hospital stays (in ICD-10) into 137 explanatory variables.To avoid overweighting the "age" variable, we divided the population into 7 sub-populations of 5 years.

RESULTS

We analyzed 1,390,307 patients in the PMSI in 2008 and 2014: 55,997 patients had coding for AD or AD dementia in 2014 (4.04%). We associated Alzheimer disease in 2014 with about 20 variables including male sex, stroke, diabetes mellitus, mental retardation, bipolar disorder, intoxication, Parkinson disease, depression, anxiety disorders, alcohol, undernutrition, fall and 3 less explored variables: intracranial hypertension (odd radio [95% confidence interval]: 1.16 [1.12-1.20] in 70-80 years group), psychotic disorder (OR: 1.09 [1.07-1.11] in 70-75 years group) and epilepsy (OR: 1.06 [1.05-1.07] after 70 years).

DISCUSSION

We analyzed 137 variables in the PMSI identified some well-known risk factors for AD, and highlighted a possible association with intracranial hypertension, which merits further investigation. Better knowledge of associations could lead to better targeting (identifying) at-risk patients, and better prevention of AD, in order to reduce its impact.

Brain-derived neurotrophic factor (BDNF) and TrkB hippocampal gene expression are putative predictors of neuritic plaque and neurofibrillary tangle pathology

INTRODUCTION

Downregulation of brain-derived neurotrophic factor (BDNF) and its cognate neurotrophin receptor, TrkB, were observed during the progression of dementia, but whether the Alzheimer's disease (AD) pathological lesions diffuse plaques, (DPs), neuritic plaques (NPs), and neurofibrillary tangles (NFTs) are related to this alteration remains to be clarified.

METHODS

Negative binomial (NB) regressions were performed using gene expression data accrued from a single population of CA1 pyramidal neurons and regional hippocampal dissections obtained from participants in the Rush Religious Orders Study (RROS).

RESULTS

Downregulation of Bdnf is independently associated with increased entorhinal cortex NPs. Downregulation of TrkB is independently associated with increased entorhinal cortex NFTs and CA1 NPs during the progression of AD.

DISCUSSION

Results indicate that BDNF and TrkB dysregulation contribute to AD neuropathology, most notably hippocampal NPs and NFTs. These data suggest attenuating BDNF/TrkB signaling deficits either at the level of BDNF, TrkB, or downstream of TrkB signaling may abrogate NPs and/or NFTs.

Associations of literacy with diabetes indicators in older adults

BACKGROUND

Literacy, the ability to access, understand and utilise information and concepts from diverse sources in ways that promote good outcomes is key to successful ageing. Domain-specific health and financial literacy are particularly relevant to older adults as they face increasingly complex health and financial demands including those related to chronic conditions like type 2 diabetes. We therefore investigated the associations of literacy, including health and financial literacy, with diabetes indicators (ie, haemoglobin A1c and blood glucose) in a community-based cohort study of ageing.

METHODS

Participants were 908 non-demented older adults (age ~81 years;75% women) from the Rush Memory and Aging Project. Literacy was measured using questions designed to assess comprehension of health and financial information and concepts and yielded a total score and domain-specific health and financial literacy scores. Non-fasting haemoglobin A1c and blood glucose samples were collected, participants were queried about diabetes status and medications for diabetes were visually inspected and coded. Participants also underwent a cognitive assessment, medical history and depressive symptom screening.

RESULTS

In separate multivariable linear regression models, total (p values <0.03) and health (p values <0.009) literacy were inversely associated with haemoglobin A1c and blood glucose levels after adjusting for age, sex, education, hypertension, global cognitive functioning and depressive symptoms. Financial literacy was inversely associated with haemoglobin A1c levels in adjusted models (p=0.04). Sensitivity analyses conducted among individuals without diabetes revealed similar results.

CONCLUSION

Lower literacy levels are associated with higher diabetes indicators, particularly haemoglobin A1c which is suggestive of longer-term glycaemic instability.

Relationship between frailty and Alzheimer's disease biomarkers: A scoping review

Introduction

Frailty and dementia appear to be closely linked, although mechanisms remain unclear. The objective was to conduct a scoping review of the association between frailty and Alzheimer's disease (AD) biomarkers in humans.

Methods

Three databases, PubMed, PsycINFO, and Embase, were searched for articles using the following search terms: “frail elderly”, “Alzheimer's disease”, “dementia biomarkers” and their synonyms. Inclusion was limited to original research in humans published before 2017, which included a frailty measure and AD biomarker (fluid markers, neuroimaging, and neuropathology).

Results

Five hundred twenty-two articles were identified and screened; 10 were included. Most were cross-sectional (n = 6), measured the frailty phenotype (n = 6), and included people with dementia (n = 7). Biomarkers examined were postmortem AD pathology (n = 3), brain atrophy (n = 5), and in vivo fluid markers (n = 2). Eight studies reported that increased frailty was associated with at least one biomarker abnormality.

Discussion

Evidence is limited and suffers from design limitations but suggests that frailty and AD biomarkers are closely linked. Longitudinal research examining multiple biomarkers and frailty is warranted.

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Very few studies examined links between frailty and Alzheimer's disease biomarkers.

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Generally, increased frailty was linked to increased Alzheimer's disease biomarker levels.

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Studies investigating this topic were largely cross sectional and underpowered.

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Future work should include longitudinal studies of frailty and multiple biomarkers.

Transition Between the Timed up and Go Turn to Sit Subtasks: Is Timing Everything?

OBJECTIVE

The Timed Up and Go (TUG), one of the most widely used tests of mobility, has been validated and associated with adverse outcomes in the community, acute care, and nursing home setting. It is composed of several distinct subtasks; however, the temporal relationship when transitioning between subtasks has not been well-studied. We tested the hypothesis that longer transition durations between the final turn to the sitting subtasks are associated with worse motor and cognitive performance in older adults.

METHODS

A total of 1055 participants (80.33 ± 7.57 years, 76.96% female) performed the TUG while wearing a 3-dimensional inertial sensor on their lower back. We employed a series of linear regressions to examine the association of the duration between the turn and sitting subtasks with clinical characteristics including motor and cognitive functions.

RESULTS

Participants employed 2 different strategies when they transitioned from turning to sitting. (1) Distinct transition strategy: 816 participants (77.34%) first completed the turn before starting to sit. The average duration between these distinct subtasks (D-interval) was 715 ± 980 ms. (2) Overlapping transition strategy: 239 participants (22.65%) started to sit before completing the turn. The average overlap duration between these tasks (O-interval) was 237 ± 269 ms. Participants who employed the distinct transition strategy were slightly younger than those who employed the overlapping transition strategy (P ≤ .013). Higher D-intervals and O-intervals were associated with worse TUG performance (P ≤ .02), with poorer motor and cognitive function, [ie, worse parkinsonian gait (P ≤ .001), lower level of perceptual speed (P ≤ .03), and with worse mobility disability (P ≤ .001)]. A longer D-interval was associated with worse gait speed and bradykinesia (P ≤ .001), whereas a longer O-interval was associated with increased rigidity (P = .004).

CONCLUSIONS

Older adults apparently employ 2 different strategies when transitioning from turning to sitting. The instrumented TUG can characterize additional gait and balance aspects that cannot be derived from traditional TUG assessments. These new measures offer novel targets for intervention to decrease the burden of late-life gait impairment.

Selective decline of neurotrophin and neurotrophin receptor genes within CA1 pyramidal neurons and hippocampus proper: Correlation with cognitive performance and neuropathology in mild cognitive impairment and Alzheimer's disease

Hippocampal CA1 pyramidal neurons, a major component of the medial temporal lobe memory circuit, are selectively vulnerable during the progression of Alzheimer's disease (AD). The cellular mechanism(s) underlying degeneration of these neurons and the relationship to cognitive performance remains largely undefined. Here, we profiled neurotrophin and neurotrophin receptor gene expression within microdissected CA1 neurons along with regional hippocampal dissections from subjects who died with a clinical diagnosis of no cognitive impairment (NCI), mild cognitive impairment (MCI), or AD using laser capture microdissection (LCM), custom-designed microarray analysis, and qPCR of CA1 subregional dissections. Gene expression levels were correlated with cognitive test scores and AD neuropathology criteria. We found a significant downregulation of several neurotrophin genes (e.g., Gdnf, Ngfb, and Ntf4) in CA1 pyramidal neurons in MCI compared to NCI and AD subjects. In addition, the neurotrophin receptor transcripts TrkB and TrkC were decreased in MCI and AD compared to NCI. Regional hippocampal dissections also revealed select neurotrophic gene dysfunction providing evidence for vulnerability within the hippocampus proper during the progression of dementia. Downregulation of several neurotrophins of the NGF family and cognate neurotrophin receptor (TrkA, TrkB, and TrkC) genes correlated with antemortem cognitive measures including the Mini-Mental State Exam (MMSE), a composite global cognitive score (GCS), and Episodic, Semantic, and Working Memory, Perceptual Speed, and Visuospatial domains. Significant correlations were found between select neurotrophic expression downregulation and neuritic plaques (NPs) and neurofibrillary tangles (NFTs), but not diffuse plaques (DPs). These data suggest that dysfunction of neurotrophin signaling complexes have profound negative sequelae within vulnerable hippocampal cell types, which play a role in mnemonic and executive dysfunction during the progression of AD.

Selective acetyl- and butyrylcholinesterase inhibitors reduce amyloid-β ex vivo activation of peripheral chemo-cytokines from Alzheimer's disease subjects: exploring the cholinergic anti-inflammatory pathway

Increasing evidence suggests that elevated production and/or reduced clearance of amyloid-β peptide (Aβ) drives the early pathogenesis of Alzheimer's disease (AD). Aβ soluble oligomers trigger a neurotoxic cascade that leads to neuronal dysfunction, neurodegeneration and, ultimately, clinical dementia. Inflammation, both within brain and systemically, together with a deficiency in the neurotransmitter acetylcholine (ACh) that underpinned the development of anticholinesterases for AD symptomatic treatment, are invariable hallmarks of the disease. The inter-relation between Aβ, inflammation and cholinergic signaling is complex, with each feeding back onto the others to drive disease progression. To elucidate these interactions plasma samples and peripheral blood mononuclear cells (PBMCs) were evaluated from healthy controls (HC) and AD patients. Plasma levels of acetylcholinesterase (AChE), butyrylcholinesterase (BuChE) and Aβ were significantly elevated in AD vs. HC subjects, and ACh showed a trend towards reduced levels. Aβ challenge of PBMCs induced a greater release of inflammatory cytokines interleukin-1β (IL-1β), monocyte chemotactic protein-1 (MCP-1) and tumor necrosis factor-alpha (TNF-α) from AD vs. HC subjects, with IL-10 being similarly affected. THP-1 monocytic cells, a cell culture counterpart of PBMCs and brain microglial cells, responded similarly to Aβ as well as to phytohaemagglutinin (PHA) challenge, to allow preliminary analysis of the cellular and molecular pathways underpinning Aβ-induced changes in cytokine expression. As amyloid-β precursor protein expression, and hence Aβ, has been reported regulated by particular cytokines and anticholinesterases, the latter were evaluated on Aβ- and PHA-induced chemocytokine expression. Co-incubation with selective AChE/BuChE inhibitors, (-)-phenserine (AChE) and (-)-cymserine analogues (BuChE), mitigated the rise in cytokine levels and suggest that augmentation of the cholinergic anti-inflammatory pathway may prove valuable in AD.

Neuropathologic assessment of dementia markers in identical and fraternal twins

Twin studies are an incomparable source of investigation to shed light on genetic and non-genetic components of neurodegenerative diseases, as Alzheimer's disease (AD). Detailed clinicopathologic correlations using twin longitudinal data and post-mortem examinations are mostly missing. We describe clinical and pathologic findings of seven monozygotic (MZ) and dizygotic (DZ) twin pairs. Our findings show good agreement between clinical and pathologic diagnoses in the majority of the twin pairs, with greater neuropathologic concordance in MZ than DZ twins. Greater neuropathologic concordance was found for β-amyloid than tau pathology within the pairs. ApoE4 was associated with higher β-amyloid and earlier dementia onset, and importantly, higher frequency of other co-occurring brain pathologies, regardless of the zygosity. Dementia onset, dementia duration, difference between twins in age at dementia onset and at death, did not correlate with AD pathology. These clinicopathologic correlations of older identical and fraternal twins support the relevance of genetic factors in AD, but not their sufficiency to determine the pathology, and consequently the disease, even in monozygotic twins. It is the interaction among genetic and non-genetic risks which plays a major role in influencing, or probably determining, the degeneration of those brain circuits associated with pathology and cognitive deficits in AD.