Ushering in the study and treatment of preclinical Alzheimer disease

Successful Object Encoding Induces Increased Directed Connectivity in Presymptomatic Early-Onset Alzheimer's Disease

BACKGROUND

Recent studies report increases in neural activity in brain regions critical to episodic memory at preclinical stages of Alzheimer's disease (AD). Although electroencephalography (EEG) is widely used in AD studies, given its non-invasiveness and low cost, there is a need to translate the findings in other neuroimaging methods to EEG.

OBJECTIVE

To examine how the previous findings using functional magnetic resonance imaging (fMRI) at preclinical stage in presenilin-1 E280A mutation carriers could be assessed and extended, using EEG and a connectivity approach.

METHODS

EEG signals were acquired during resting and encoding in 30 normal cognitive young subjects, from an autosomal dominant early-onset AD kindred from Antioquia, Colombia. Regions of the brain previously reported as hyperactive were used for connectivity analysis.

RESULTS

Mutation carriers exhibited increasing connectivity at analyzed regions. Among them, the right precuneus exhibited the highest changes in connectivity.

CONCLUSION

Increased connectivity in hyperactive cerebral regions is seen in individuals, genetically-determined to develop AD, at preclinical stage. The use of a connectivity approach and a widely available neuroimaging technique opens the possibility to increase the use of EEG in early detection of preclinical AD.

Upward drift in cerebrospinal fluid amyloid β 42 assay values for more than 10 years

INTRODUCTION

The best-established cerebrospinal fluid (CSF) biomarkers for Alzheimer's disease are levels of amyloid β 42 (Aβ42), total tau (tau), and phosphorylated tau 181 (ptau). We examined whether a widely used commercial immunoassay for CSF Aβ42, tau, and ptau provided stable measurements for more than ∼10 years.

METHODS

INNOTEST assay values for CSF Aβ42, tau, and ptau from Washington University in St. Louis and VU Medical Center, Amsterdam, were evaluated.

RESULTS

Aβ42 values as measured by the INNOTEST assay drifted upward by approximately 3% per year over the past decade. Tau values remained relatively stable, whereas results for ptau were mixed.

DISCUSSION

Assay drift may reduce statistical power or even confound analyses. The drift in INNOTEST Aβ42 values may reduce diagnostic accuracy for Alzheimer's disease in the clinic. We recommend methods to account for assay drift in existing data sets and to reduce assay drift in future studies.

Static and Dynamic Cognitive Reserve Proxy Measures: Interactions with Alzheimer's Disease Neuropathology and Cognition

OBJECTIVE

Years of education are the most common proxy for measuring cognitive reserve (CR) when assessing the relationship between Alzheimer's disease (AD) neuropathology and cognition. However, years of education may be limited as a CR proxy given that it represents a specific timeframe in early life and is static. Studies suggest that measures of intellectual function provide a dynamic estimate of CR that is superior to years of education since it captures the effect of continued learning over time. The present study determined whether dynamic measures of CR were better predictors of episodic memory and executive function in the presence of AD pathology than a static measure of CR.

METHODS

Subjects examined died with a pre-mortem clinical diagnosis of no cognitive impaired, mild cognitive impairment and mild to moderate AD. CERAD and Braak stage were used to stratify the sample by AD pathology severity. Linear regression analyses using CR by CERAD and CR by Braak stage interaction terms were used to determine whether Extended Range Vocabulary Test (ERVT) scores or years of education were significantly associated with episodic memory composite (EMC) and executive function composite (EFC) performance. All models were adjusted for clinical diagnosis, age at death, gender, APOE e4 carrier status and Braak stage.

RESULTS

For episodic memory, years of education by CERAD interaction were not statistically significant (β=-0.01, SE=0.01, p=0.53). By contrast, ERVT interaction with CERAD diagnosis was statistically significant (β=-0.03, SE=0.01, p=0.004). Among the models using Braak stages, none of the CR by pathology interactions were associated with EMC or EFC.

CONCLUSION

Results suggest that a dynamic rather than a static measure is a better indicator of CR and that the relationship between CR and cognition is dependent upon the severity of select AD criteria.

Circadian wheel running behavior is altered in an APP/E4 mouse model of late onset Alzheimer's disease

Circadian rhythms are altered in several diseases associated with aging, one of which is Alzheimer's disease (AD). One example of a circadian rhythm is the rest-activity cycle, which can be measured in mice by monitoring their wheel-running. The present study sought to investigate differences in light phase/dark phase activity between a mouse model of late onset AD (APP/E4) and control (C57Bl6J) mice, in both the pre-plaque and post-plaques stages of the disease. To assess activity level, 24-h wheel running behavior was monitored at six months (pre-plaque) and twelve months (post-plaque) for a period of nine days. The following measures were analyzed: counts (wheel rotations) during the dark phase, counts during the light phase, hour of activity onset, and hour of activity offset. Key findings indicate that activity onset is delayed in APP/E4 mice at six and twelve months, and activity profiles for APP/E4 and C57Bl6J mice differ during the light and dark phase in such a way that APP/E4 mice run less in the early hours of the dark phase and more in the later hours of the dark phase compared to C57Bl6J mice. These findings imply that rest-activity cycle is altered in the pre-plaque stages of AD in APP/E4 mice, as they show impairments as early as six months of age.

A Review of Biomarkers for Neurodegenerative Disease: Will They Swing Us Across the Valley?

Measures of the severity of cognitive impairment or parkinsonism are the usual endpoints in clinical trials for Alzheimer’s disease (AD) and Parkinson’s disease (PD), but are critically hampered by their lack of disease sensitivity and specificity. Due to the high failure rate of clinical trials, the rate of regulatory approval for efficacious new drugs has stagnated in the past few decades, with the gap between basic science discovery and clinical application metaphorically termed the “Valley of Death”. While the causes for this are probably multiple and complex, the usage of biomarkers as surrogate endpoints, particularly when they are molecularly-specific for the disease, has achieved some success in cancer trials, and it is likely that neurodegenerative disease trials would benefit from the same approach. As dementia and parkinsonism are not disease-specific clinical syndromes, both AD and PD trials have been flawed by reliance on clinical diagnosis and clinical endpoints. Clinical improvement has been a requirement for regulatory approval, but molecularly-specific biomarkers should improve both diagnostic accuracy and tracking of disease progression, allowing quicker screening of drug candidates. However, even when a molecularly-specific biomarker is found, such as amyloid imaging for AD, it may not reflect the entire extant molecular disease repertoire and may not serve equally well in the different roles of preclinical detection, diagnostic confirmation and surrogate endpoint, necessitating the usage of two, three or more biomarkers, deployed in series or in parallel.

Precuneus Failures in Subjects of the PSEN1 E280A Family at Risk of Developing Alzheimer's Disease Detected Using Quantitative Electroencephalography

BACKGROUND

Presenilin-1 (PSEN1) mutations are the most common cause of familial early onset Alzheimer's disease (AD). The PSEN1 E280A (E280A) mutation has an autosomal dominant inheritance and is involved in the production of amyloid-β. The largest family group of carriers with E280A mutation is found in Antioquia, Colombia. The study of mutation carriers provides a unique opportunity to identify brain changes in stages previous to AD. Electroencephalography (EEG) is a low cost and minimally invasiveness technique that enables the following of brain changes in AD.

OBJECTIVE

To examine how previous reported differences in EEG for Theta and Alpha-2 rhythms in E280A subjects are related to specific regions in cortex and could be tracked across different ages.

METHODS

EEG signals were acquired during resting state from non-carriers and carriers, asymptomatic and symptomatic subjects from E280A kindred from Antioquia, Colombia. Independent component analysis (ICA) and inverse solution methods were used to locate brain regions related to differences in Theta and Alpha-2 bands.

RESULTS

ICA identified two components, mainly related to the Precuneus, where the differences in Theta and Alpha-2 exist simultaneously at asymptomatic and symptomatic stages. When the ratio between Theta and Alpha-2 is used, significant correlations exist with age and a composite cognitive scale.

CONCLUSION

Theta and Alpha-2 rhythms are altered in E280A subjects. The alterations are possible to track at Precuneus regions using EEG, ICA, and inverse solution methods.

Sub-Clinical Cognitive Decline and Resting Cerebral Blood Flow in Middle Aged Men

BACKGROUND

Although dementia is associated with both global and regional cerebral blood flow (CBF) changes, little is known about cerebral perfusion in the early pre-clinical stages of cognitive decline preceding overt cognitive dysfunction. The aim of this study was to investigate the association of early sub-clinical cognitive decline with CBF.

MATERIALS AND METHODS

The study participants were recruited from a cohort of Danish men born in 1953. Based on a regression model we selected men who performed better (Group A, n = 94) and poorer (Group B, n = 95) on cognitive testing at age 57 than expected from testing at age 20. Participants underwent supplementary cognitive testing, blood sampling and MRI including measurements of regional and global CBF.

RESULTS

Regional CBF was lower in group B than in group A in the posterior cingulate gyrus and the precuneus. The associations were attenuated when corrected for global atrophy, but remained significant in regions of interest based analysis adjusting for regional gray matter volume and vascular risk factors. No influence of group on global CBF was observed.

CONCLUSIONS

We conclude that early sub-clinical cognitive decline is associated with reduced perfusion in the precuneus and posterior cingulate gyrus independently of regional atrophy and vascular risk factors, but cannot be statistically separated from an association with global atrophy.

Widespread temporo-occipital lobe dysfunction in amyotrophic lateral sclerosis

Recent studies suggest that amyotrophic lateral sclerosis (ALS) and frontotemporal dementia (FTD) lie on a single clinical continuum. However, previous neuroimaging studies have found only limited involvement of temporal lobe regions in ALS. To better delineate possible temporal lobe involvement in ALS, the present study aimed to examine changes in functional connectivity across the whole brain, particularly with regard to extra-motor regions, in a group of 64 non-demented ALS patients and 38 healthy controls. To assess between-group differences in connectivity, we computed edge-level statistics across subject-specific graphs derived from resting-state functional MRI data. In addition to expected ALS-related decreases in functional connectivity in motor-related areas, we observed extensive changes in connectivity across the temporo-occipital cortex. Although ALS patients with comorbid FTD were deliberately excluded from this study, the pattern of connectivity alterations closely resembles patterns of cerebral degeneration typically seen in FTD. This evidence for subclinical temporal dysfunction supports the idea of a common pathology in ALS and FTD.

Plasma Cortisol, Brain Amyloid-β, and Cognitive Decline in Preclinical Alzheimer's Disease: A 6-Year Prospective Cohort Study

BACKGROUND

Hypothalamic-pituitary-adrenal axis dysregulation, which is typically assessed by measuring cortisol levels, is associated with cognitive dysfunction, hippocampal atrophy, and increased risk for mild cognitive impairment and Alzheimer's disease (AD). However, little is known about the role of hypothalamic-pituitary-adrenal axis dysregulation in moderating the effect of high levels of amyloid-β (Aβ+) on cognitive decline in the preclinical phase of AD, which is often protracted, and thus offers opportunities for prevention and early intervention.

METHODS

Using data from a 6-year multicenter prospective cohort study, we evaluated the relation between Aβ level, plasma cortisol level, and cognitive decline in 416 cognitively normal older adults.

RESULTS

Results revealed that Aβ+ older adults experienced faster decline than Aβ- older adults in all cognitive domains (Cohen's d at 6-year assessment = 0.37-0.65). They further indicated a significant interaction between Aβ and cortisol levels for global cognition (d = 0.32), episodic memory (d = 0.50), and executive function (d = 0.59) scores, with Aβ+ older adults with high cortisol levels having significantly faster decline in these domains compared with Aβ+ older adults with low cortisol levels. These effects were independent of age, sex, APOE genotype, anxiety symptoms, and radiotracer type.

CONCLUSIONS

In cognitively healthy older adults, Aβ+ is associated with greater cognitive decline and high plasma cortisol levels may accelerate the effect of Aβ+ on decline in global cognition, episodic memory, and executive function. These results suggest that therapies targeted toward lowering plasma cortisol and Aβ levels may be helpful in mitigating cognitive decline in the preclinical phase of AD.

Characterization of AD-like phenotype in aged APPSwe/PS1dE9 mice

Transgenic APPSwe/PS1dE9 (APP/PS1) mice that overproduce amyloid beta (Aβ) are extensively used in the studies of pathogenesis and experimental therapeutics and new drug screening for Alzheimer's disease (AD). However, most of the current literature uses young or adult APP/PS1 mice. In order to provide a broader view of AD-like phenotype of this animal model, in this study, we systematically analyzed behavioral and pathological profiles of 24-month-old male APP/PS1 mice. Aged APP/PS1 mice had reference memory deficits as well as anxiety, hyperactivity, and social interaction impairment. Consistently, there was obvious deposition of amyloid plaques in the dorsal hippocampus with decreased expression of insulin-degrading enzyme, a proteolytic enzyme responsible for degradation of intracellular Aβ. Furthermore, decreases in hippocampal volume, neuronal number and synaptophysin expression, and astrocyte atrophy were also observed in aged APP/PS1 mice. This finding suggests that aged APP/PS1 mice can well replicate cognitive and noncognitive behavioral abnormalities, hippocampal atrophy, and neuronal and astrocyte degeneration in AD patients, to enable more objective and refined preclinical evaluation of therapeutic drugs and strategies for AD treatment.

Neuritic and Diffuse Plaque Associations with Memory in Non-Cognitively Impaired Elderly

The presence of Alzheimer's disease (AD)-related neuropathology among cognitively normal individuals has been well documented. It has been proposed that these individuals may represent a pre-clinical AD population. Previous studies have demonstrated a negative association between the presence of both amyloid-β (Aβ) plaques and neurofibrillary tangles with ante-mortem cognitive performance, a relationship which is likely influenced by a number of factors including age and APOE ɛ4 carrier status. The present study determined whether the presence of neuritic plaques (NPs) and diffuse plaques (DPs) are associated with performance in a number of cognitive domains after accounting for APOE ɛ4 carrier status and neurofibrillary tangle presence in a cohort of 123 older participants from the Rush Religious Order Study who died with a premortem clinical diagnosis of no cognitive impairment (NCI). After adjusting for age at death, education, gender, Braak stage, and APOE ɛ4 carrier status, the presence of NPs was associated with lower performance in the cognitive domains of Global Cognition (p = 0.002), Episodic Memory (p = 0.03), Semantic Memory (p = 0.009), and Visuospatial performance (p = 0.006), while DPs showed no association with any cognitive domain examined. These results suggest that decreases in cognition in elderly NCI individuals are associated with an increase in NPs and not DPs when age at death, education, gender, APOE ɛ4 status, and Braak stage are taken into consideration.

Influence of APOE Genotype on Hippocampal Atrophy over Time - An N=1925 Surface-Based ADNI Study

The apolipoprotein E (APOE) e4 genotype is a powerful risk factor for late-onset Alzheimer’s disease (AD). In the Alzheimer’s Disease Neuroimaging Initiative (ADNI) cohort, we previously reported significant baseline structural differences in APOE e4 carriers relative to non-carriers, involving the left hippocampus more than the right—a difference more pronounced in e4 homozygotes than heterozygotes. We now examine the longitudinal effects of APOE genotype on hippocampal morphometry at 6-, 12- and 24-months, in the ADNI cohort. We employed a new automated surface registration system based on conformal geometry and tensor-based morphometry. Among different hippocampal surfaces, we computed high-order correspondences, using a novel inverse-consistent surface-based fluid registration method and multivariate statistics consisting of multivariate tensor-based morphometry (mTBM) and radial distance. At each time point, using Hotelling’s T² test, we found significant morphological deformation in APOE e4 carriers relative to non-carriers in the full cohort as well as in the non-demented (pooled MCI and control) subjects at each follow-up interval. In the complete ADNI cohort, we found greater atrophy of the left hippocampus than the right, and this asymmetry was more pronounced in e4 homozygotes than heterozygotes. These findings, combined with our earlier investigations, demonstrate an e4 dose effect on accelerated hippocampal atrophy, and support the enrichment of prevention trial cohorts with e4 carriers.

The Alzheimer's Disease Neuroimaging Initiative 2 PET Core: 2015

INTRODUCTION

This article reviews the work done in the Alzheimer's Disease Neuroimaging Initiative positron emission tomography (ADNI PET) core over the past 5 years, largely concerning techniques, methods, and results related to amyloid imaging in ADNI.

METHODS

The PET Core has used [(18)F]florbetapir routinely on ADNI participants, with over 1600 scans available for download. Four different laboratories are involved in data analysis, and have examined factors such as longitudinal florbetapir analysis, use of [(18)F]fluorodeoxyglucose (FDG)-PET in clinical trials, and relationships between different biomarkers and cognition.

RESULTS

Converging evidence from the PET Core has indicated that cross-sectional and longitudinal florbetapir analyses require different reference regions. Studies have also examined the relationship between florbetapir data obtained immediately after injection, which reflects perfusion, and FDG-PET results. Finally, standardization has included the translation of florbetapir PET data to a centiloid scale.

CONCLUSION

The PET Core has demonstrated a variety of methods for the standardization of biomarkers such as florbetapir PET in a multicenter setting.

Anxiety is associated with increased risk of dementia in older Swedish twins

INTRODUCTION

We asked whether anxiety is associated with prospective risk of dementia, and the extent to which genetic influences mediate this association.

METHODS

Nondemented twins (n = 1082) from the Swedish Adoption Twin Study of Aging completed an assessment of anxiety symptoms in 1984 and were followed for 28 years.

RESULTS

Baseline anxiety score, independent of depressive symptoms, was significantly associated with incident dementia over follow-up (hazard ratio [HR] = 1.04; 95% confidence interval [CI] = 1.01-1.06). There was 48% increased risk of becoming demented for those who had experienced high anxiety at any time compared with those who had not. In co-twin analyses, the association between anxiety symptoms and dementia was greater for dizygotic (HR = 1.11; 95% CI = 1.02-1.20) compared with monozygotic twins (HR = 1.06; 95% CI = 0.95-1.20), indicating genetic mediation.

DISCUSSION

Anxiety symptoms were associated with increased risk of dementia. Genetic factors common to dementia and anxiety partially mediated this association.

Occupational cognitive requirements and late-life cognitive aging

OBJECTIVE

To examine whether occupational cognitive requirements, as a marker of adulthood cognitive activity, are associated with late-life cognition and cognitive decline.

METHODS

Main lifetime occupation information for 7,637 participants aged >65 years of the Chicago Health and Aging Project (CHAP) was linked with standardized data on worker attributes and job characteristics from the Occupational Information Network (O*NET). Ratings of cognitive processes required in 10 work-related tasks were used to create a summary measure of occupational cognitive requirements (possible range 0-7). Multivariable-adjusted linear mixed models were used to estimate the association of occupational cognitive requirements score (OCRS) with cognitive function and rate of cognitive decline.

RESULTS

Higher OCRS corresponded to significantly better late-life cognitive performance at baseline in 1993 (p < 0.001) and to slower decline in global cognitive function over time (p = 0.004). Within a genotyped subsample (n = 4,104), the associations of OCRS with rate of cognitive decline did not differ significantly by APOE ε4 carriership (p = 0.11).

CONCLUSIONS

Findings suggest that occupational cognitive requirements are associated with better cognition and a slower rate of cognitive decline in older age. Adulthood cognitive activity may contribute to cognitive reserve in late life.

Novel verbal fluency scores and structural brain imaging for prediction of cognitive outcome in mild cognitive impairment

INTRODUCTION

The objective of this study was to assess the utility of novel verbal fluency scores for predicting conversion from mild cognitive impairment (MCI) to clinical Alzheimer's disease (AD).

METHOD

Verbal fluency lists (animals, vegetables, F, A, and S) from 107 MCI patients and 51 cognitively normal controls were transcribed into electronic text files and automatically scored with traditional raw scores and five types of novel scores computed using methods from machine learning and natural language processing. Additional scores were derived from structural MRI scans: region of interest measures of hippocampal and ventricular volumes and gray matter scores derived from performing ICA on measures of cortical thickness. Over 4 years of follow-up, 24 MCI patients converted to AD. Using conversion as the outcome variable, ensemble classifiers were constructed by training classifiers on the individual groups of scores and then entering predictions from the primary classifiers into regularized logistic regression models. Receiver operating characteristic curves were plotted, and the area under the curve (AUC) was measured for classifiers trained with five groups of available variables.

RESULTS

Classifiers trained with novel scores outperformed those trained with raw scores (AUC 0.872 vs 0.735; P < .05 by DeLong test). Addition of structural brain measurements did not improve performance based on novel scores alone.

CONCLUSION

The brevity and cost profile of verbal fluency tasks recommends their use for clinical decision making. The word lists generated are a rich source of information for predicting outcomes in MCI. Further work is needed to assess the utility of verbal fluency for early AD.

Frontotemporal Lobar Degeneration and MicroRNAs

Frontotemporal lobar degeneration (FTLD) includes a spectrum of disorders characterized by changes of personality and social behavior and, often, a gradual and progressive language dysfunction. In the last years, several efforts have been fulfilled in identifying both genetic mutations and pathological proteins associated with FTLD. The molecular bases undergoing the onset and progression of the disease remain still unknown. Recent literature prompts an involvement of RNA metabolism in FTLD, particularly microRNAs (miRNAs). Dysregulation of miRNAs in several disorders, including neurodegenerative diseases, and increasing importance of circulating miRNAs in different pathologies has suggested to implement the study of their possible application as biological markers and new therapeutic targets; moreover, miRNA-based therapy is becoming a powerful tool to deepen the function of a gene, the mechanism of a disease, and validate therapeutic targets. Regarding FTLD, different studies showed that miRNAs are playing an important role. For example, several reports have evaluated miRNA regulation of the progranulin gene suggesting that it is under their control, as described for miR-29b, miR-107, and miR-659. More recently, it has been demonstrated that TMEM106B gene, which protein is elevated in FTLD-TDP brains, is repressed by miR-132/212 cluster; this post-transcriptional mechanism increases intracellular levels of progranulin, affecting its pathways. These findings if confirmed could suggest that these microRNAs have a role as potential targets for some related-FTLD genes. In this review, we focus on the emerging roles of the miRNAs in the pathogenesis of FTLD.

The FDA-approved natural product dihydroergocristine reduces the production of the Alzheimer's disease amyloid-β peptides

Known γ-secretase inhibitors or modulators display an undesirable pharmacokinetic profile and toxicity and have therefore not been successful in clinical trials for Alzheimer's disease (AD). So far, no compounds from natural products have been identified as direct inhibitors of γ-secretase. To search for bioactive molecules that can reduce the amount of amyloid-beta peptides (Aβ) and that have better pharmacokinetics and an improved safety profile, we completed a screen of ~400 natural products by using cell-based and cell-free γ-secretase activity assays. We identified dihydroergocristine (DHEC), a component of an FDA- (Food and Drug Administration)-approved drug, to be a direct inhibitor of γ-secretase. Micromolar concentrations of DHEC substantially reduced Aβ levels in different cell types, including a cell line derived from an AD patient. Structure-activity relationship studies implied that the key moiety for inhibiting γ-secretase is the cyclized tripeptide moiety of DHEC. A Surface Plasmon Resonance assay showed that DHEC binds directly to γ-secretase and Nicastrin, with equilibrium dissociation constants (Kd) of 25.7 nM and 9.8 μM, respectively. This study offers DHEC not only as a new chemical moiety for selectively modulating the activity of γ-secretase but also a candidate for drug repositioning in Alzheimer's disease.

Alzheimer's disease

Alzheimer's disease is a chronic illness with long preclinical and prodromal phases (20 years) and an average clinical duration of 8-10 years. The disease has an estimated prevalence of 10-30% in the population >65 years of age with an incidence of 1-3%. Most patients with Alzheimer's disease (>95%) have the sporadic form, which is characterized by a late onset (80-90 years of age), and is the consequence of the failure to clear the amyloid-β (Aβ) peptide from the interstices of the brain. A large number of genetic risk factors for sporadic disease have been identified. A small proportion of patients (<1%) have inherited mutations in genes that affect processing of Aβ and develop the disease at a much younger age (mean age of ∼45 years). Detection of the accumulation of Aβ is now possible in preclinical and prodromal phases using cerebrospinal fluid biomarkers and PET. Several approved drugs ameliorate some of the symptoms of Alzheimer's disease, but no current interventions can modify the underlying disease mechanisms. Management is focused on the support of the social networks surrounding the patient and the treatment of any co-morbid illnesses, such as cerebrovascular disease.

Gadolinium-complexed Aβ-binding contrast agents for MRI diagnosis of Alzheimer's Disease

MRI contrast agents, containing peptide sequences that bind β-amyloid and gadolinium ions ligated to DOTA have been synthesized for evaluation in early diagnosis of Alzheimer's Disease in transgenic mice models. A number of brain penetration modifications were incorporated and sufficient amounts of contrast agent in the brain were achieved only by addition of a cationic cell penetration sequence along with the use of microparticle assisted ultrasound activation. In the T1 mode of a MRI scan, the peptide (R2) illuminated areas of brain rich in amyloid plaques.

Genetic Analysis of Association Between Calcium Signaling and Hippocampal Activation, Memory Performance in the Young and Old, and Risk for Sporadic Alzheimer Disease

IMPORTANCE

Human episodic memory performance is linked to the function of specific brain regions, including the hippocampus; declines as a result of increasing age; and is markedly disturbed in Alzheimer disease (AD), an age-associated neurodegenerative disorder that primarily affects the hippocampus. Exploring the molecular underpinnings of human episodic memory is key to the understanding of hippocampus-dependent cognitive physiology and pathophysiology.

OBJECTIVE

To determine whether biologically defined groups of genes are enriched in episodic memory performance across age, memory encoding-related brain activity, and AD.

DESIGN, SETTING, AND PARTICIPANTS

In this multicenter collaborative study, which began in August 2008 and is ongoing, gene set enrichment analysis was done by using primary and meta-analysis data from 57 968 participants. The Swiss cohorts consisted of 3043 healthy young adults assessed for episodic memory performance. In a subgroup (n = 1119) of one of these cohorts, functional magnetic resonance imaging was used to identify gene set-dependent differences in brain activity related to episodic memory. The German Study on Aging, Cognition, and Dementia in Primary Care Patients cohort consisted of 763 elderly participants without dementia who were assessed for episodic memory performance. The International Genomics of Alzheimer's Project case-control sample consisted of 54 162 participants (17 008 patients with sporadic AD and 37 154 control participants). Analyses were conducted between January 2014 and June 2015. Gene set enrichment analysis in all samples was done using genome-wide single-nucleotide polymorphism data.

MAIN OUTCOMES AND MEASURES

Episodic memory performance in the Swiss cohort and German Study on Aging, Cognition, and Dementia in Primary Care Patients cohort was quantified by picture and verbal delayed free recall tasks. In the functional magnetic resonance imaging experiment, activation of the hippocampus during encoding of pictures served as the phenotype of interest. In the International Genomics of Alzheimer's Project sample, diagnosis of sporadic AD served as the phenotype of interest.

RESULTS

In the discovery sample, we detected significant enrichment for genes constituting the calcium signaling pathway, especially those related to the elevation of cytosolic calcium (P = 2 × 10-4). This enrichment was replicated in 2 additional samples of healthy young individuals (P = .02 and .04, respectively) and a sample of healthy elderly participants (P = .004). Hippocampal activation (P = 4 × 10-4) and the risk for sporadic AD (P = .01) were also significantly enriched for genes related to the elevation of cytosolic calcium.

CONCLUSIONS AND RELEVANCE

By detecting consistent significant enrichment in independent cohorts of young and elderly participants, this study identified that calcium signaling plays a central role in hippocampus-dependent human memory processes in cognitive health and disease, contributing to the understanding and potential treatment of hippocampus-dependent cognitive pathology.

Potentials and limits to enhance cognitive functions in healthy and pathological aging by tDCS

Transcranial direct current stimulation (tDCS) is a non-invasive brain stimulation technique that is increasingly used in research and clinical settings to enhance the effects of cognitive training. In our present review, we will first summarize studies using tDCS alone and in combination with cognitive training in older adults and patients with Alzheimer’s dementia (AD). We will also review one study (Meinzer et al., 2014c) that showed an improvement in cognitive performance during anodal tDCS over the left inferior frontal cortex in patients with mild cognitive impairment (MCI) which is regarded as a prodromal stage of AD. Although promising short-term results have been reported, evidence from randomized controlled trials (RCTs) with sufficient sample sizes is scarce. In addition, stimulation protocols (in terms of intensity, duration, and repetition of stimulation) that lead to sustained improvements in outcome measures relevant for daily life still remain to be established. Following, we will discuss modulating factors such as technical parameters as well as the question whether there are specific cognitive functions (e.g., learning, memory consolidation, executive control) which are more amenable to tDCS enhancement than others. Finally, we will highlight future directions and limitations in this field and emphasize the need to conduct RCTs to establish efficacy of interventions for activities of daily life for a given patient population.

Protein aggregation and neurodegeneration in prototypical neurodegenerative diseases: Examples of amyloidopathies, tauopathies and synucleinopathies

Alzheimer's and Parkinson's diseases are the most prevalent neurodegenerative diseases that generate important health-related direct and indirect socio-economic costs. They are characterized by severe neuronal losses in several disease-specific brain regions associated with deposits of aggregated proteins. In Alzheimer's disease, β-amyloid peptide-containing plaques and intraneuronal neurofibrillary tangles composed of hyperphosphorylated microtubule-associated protein tau are the two main neuropathological lesions, while Parkinson's disease is defined by the presence of Lewy Bodies that are intraneuronal proteinaceous cytoplasmic inclusions. α-Synuclein has been identified as a major protein component of Lewy Bodies and heavily implicated in the pathogenesis of Parkinson's disease. In the past few years, evidence has emerged to explain how these aggregate-prone proteins can undergo spontaneous self-aggregation, propagate from cell to cell, and mediate neurotoxicity. Current research now indicates that oligomeric forms are probably the toxic species. This article discusses recent progress in the understanding of the pathogenesis of these diseases, with a focus on the underlying mechanisms of protein aggregation, and emphasizes the pathophysiological molecular mechanisms leading to cellular toxicity. Finally, we present the putative direct link between β-amyloid peptide and tau in causing toxicity in Alzheimer's disease as well as α-synuclein in Parkinson's disease, along with some of the most promising therapeutic strategies currently in development for those incurable neurodegenerative disorders.

A fresh perspective from immunologists and vaccine researchers: active vaccination strategies to prevent and reverse Alzheimer's disease

Traditional vaccination against infectious diseases relies on generation of cellular and humoral immune responses that act to protect the host from overt disease even though they do not induce sterilizing immunity. More recently, attempts have been made with mixed success to generate therapeutic vaccines against a wide range of noninfectious diseases including neurodegenerative disorders. After the exciting first report of successful vaccine prevention of progression of an Alzheimer's disease (AD) animal model in 1999, various epitope-based vaccines targeting amyloid beta (Aβ) have proceeded to human clinical trials, with varied results. More recently, AD vaccines based on tau protein have advanced into clinical testing too. This review seeks to put perspective to the mixed results obtained so far in clinical trials of AD vaccines and discusses the many pitfalls and misconceptions encountered on the path to a successful AD vaccine, including better standardization of immunologic efficacy measures of antibodies, immunogenicity of platform/carrier and adjuvants.

Let Food Be Thy Medicine: Diet, Nutrition, and Biomarkers' Risk of Alzheimer's Disease

Epidemiological evidence linking diet-one of the most important modifiable lifestyle factors-and risk of Alzheimer's disease (AD)-the most common cause of dementia-is rapidly increasing. However, the biological mechanisms underlying the relationship between dietary nutrients, brain aging, and risk of AD are largely unexplored. Recent studies using brain imaging and biological markers of AD have begun to clarify how diet and nutrition modulate risk of AD in cognitively normal individuals, especially those at increased genetic risk. Such knowledge is critical prior to implementing dietary recommendations for prevention and treatment of disease.

Catecholamine-Based Treatment in AD Patients: Expectations and Delusions

In Alzheimer disease, the gap between excellence of diagnostics and efficacy of therapy is wide. Despite sophisticated imaging and biochemical markers, the efficacy of available therapeutic options is limited. Here we examine the possibility that assessment of endogenous catecholamine levels in cerebrospinal fluid (CSF) may fuel new therapeutic strategies. In reviewing the available literature, we consider the effects of levodopa, monoamine oxidase inhibitors, and noradrenaline (NE) modulators, showing disparate results. We present a preliminary assessment of CSF concentrations of dopamine (DA) and NE, determined by HPLC, in a small dementia cohort of either Alzheimer’s disease (AD) or frontotemporal dementia patients, compared to control subjects. Our data reveal detectable levels of DA, NE in CSF, though we found no significant alterations in the dementia population as a whole. AD patients exhibit a small impairment of the DA axis and a larger increase of NE concentration, likely to represent a compensatory mechanism. While waiting for preventive strategies, a pragmatic approach to AD may re-evaluate catecholamine modulation, possibly stratified to dementia subtypes, as part of the therapeutic armamentarium.

A novel cortical thickness estimation method based on volumetric Laplace-Beltrami operator and heat kernel

Cortical thickness estimation in magnetic resonance imaging (MRI) is an important technique for research on brain development and neurodegenerative diseases. This paper presents a heat kernel based cortical thickness estimation algorithm, which is driven by the graph spectrum and the heat kernel theory, to capture the gray matter geometry information from the in vivo brain magnetic resonance (MR) images. First, we construct a tetrahedral mesh that matches the MR images and reflects the inherent geometric characteristics. Second, the harmonic field is computed by the volumetric Laplace-Beltrami operator and the direction of the steamline is obtained by tracing the maximum heat transfer probability based on the heat kernel diffusion. Thereby we can calculate the cortical thickness information between the point on the pial and white matter surfaces. The new method relies on intrinsic brain geometry structure and the computation is robust and accurate. To validate our algorithm, we apply it to study the thickness differences associated with Alzheimer's disease (AD) and mild cognitive impairment (MCI) on the Alzheimer's Disease Neuroimaging Initiative (ADNI) dataset. Our preliminary experimental results on 151 subjects (51 AD, 45 MCI, 55 controls) show that the new algorithm may successfully detect statistically significant difference among patients of AD, MCI and healthy control subjects. Our computational framework is efficient and very general. It has the potential to be used for thickness estimation on any biological structures with clearly defined inner and outer surfaces.

Circulating Biomarker Panels in Alzheimer's Disease

The early diagnosis of diseases frequently represents an important unmet clinical need supporting in-time treatment of pathologies. This also applies to neurodegenerative diseases such as Alzheimer's disease (AD), the most common form of dementia, estimated to affect millions of individuals worldwide. The respective diagnostic and prognostic markers, especially for the preclinical stages of AD, are expected to improve patients' outcome significantly. In the last decades, many approaches to detecting AD have been developed, including markers to discover changes in amyloid-β levels [from cerebrospinal fluid (CSF) or using positron emission tomography] or other brain imaging technologies such as structural magnetic resonance imaging (MRI), functional-connectivity MRI or task-related functional MRI. A major challenge is the detection of AD using minimally or even noninvasive biomarkers from body fluids such as plasma or serum. Circulating biomarker candidates based on mRNAs or proteins measured from blood cells, plasma or serum have been proposed for various pathologies including AD. As for other diseases, there is a tendency to use marker signatures obtained by high-throughput approaches, which allow the generation of profiles of hundreds to thousands of biomarkers simultaneously [microarrays, mass spectrometry or next-generation sequencing (NGS)]. Beyond mRNAs and proteins, recent approaches have measured small noncoding RNA (so-called microRNA) profiles in AD patients' blood samples using NGS or array-based technologies. Generally, the development of marker panels is in its early stages and requires further, substantial clinical validation. In this review, we provide an overview of different circulating AD biomarkers, starting with a brief summary of CSF markers and focusing on novel biomarker signatures such as small noncoding RNA profiles.

The role of proteotoxic stress in vascular dysfunction in the pathogenesis of Alzheimer’s disease

Alzheimer’s disease (AD) is the principal cause of dementia in the elderly; however, its prevalence is increasing due to the fact that current pharmaceuticals used to manage the symptoms are not capable of preventing, halting, or reversing disease progression. In the last decade, evidence has accumulated to support the hypothesis that a primary cerebral vascular dysfunction initiates the cascade of events that leads to neuronal injury and the subsequent cognitive decline observed in AD. The mechanisms underlying these vascular defects and their relationship with neurodegeneration are still poorly understood however. It is pathologically known that cerebrovascular dysfunctions can induce the deposition of amyloid-β (Aβ), an amyloidogenic and toxic peptide that in turn causes cerebrovascular degeneration. Mammalian cells regulate proteostasis and the functioning of intracellular organelles through diverse mechanisms such as the Unfolded Protein Response, the Ubiquitin-Proteasome System and autophagy; however, when these mechanisms cannot compensate for perturbations in homeostasis, the cell undergoes programmed death via apoptosis. This review summarizes recent studies that together correlate the deregulation of protein quality control pathways with dysfunction of vascular endothelial cells of the brain in AD, thus supporting the hypothesis that it is the vicious, progressive failure of the proteostatic network and endothelial activation that underlies the cerebrovascular changes that symptomize AD.

Circulating microRNAs in Neurodegenerative Diseases

Neurodegenerative diseases, such as Alzheimer's disease (AD), Parkinson's disease (PD), and amyotrophic lateral sclerosis (ALS), are caused by a combination of events that impair normal neuronal function. Although they are considered different disorders, there are overlapping features among them from the clinical, pathological, and genetic points of view. Synaptic dysfunction and loss, neurite retraction, and the appearance of other abnormalities such as axonal transport defects normally precede the neuronal loss that is a relatively late event. The diagnosis of many neurodegenerative diseases is mainly based on patient's cognitive function analysis, and the development of diagnostic methods is complicated by the brain's capacity to compensate for neuronal loss over a long period of time. This results in the late clinical manifestation of symptoms, a time when successful treatment is no longer feasible. Thus, a noninvasive diagnostic method based on early events detection is particularly important. In the last years, some biomarkers expressed in human body fluids have been proposed. microRNAs (miRNAs), with their high stability, tissue- or cell type-specific expression, lower cost, and shorter time in the assay development, could constitute a good tool to obtain an early disease diagnosis for a wide number of human pathologies, including neurodegenerative diseases. The possibilities and challenges of using these small RNA molecules as a signature for neurodegenerative disorders is a highly promising approach for developing minimally invasive screening tests and to identify new therapeutic targets.

Studying ventricular abnormalities in mild cognitive impairment with hyperbolic Ricci flow and tensor-based morphometry

Mild Cognitive Impairment (MCI) is a transitional stage between normal aging and dementia and people with MCI are at high risk of progression to dementia. MCI is attracting increasing attention, as it offers an opportunity to target the disease process during an early symptomatic stage. Structural magnetic resonance imaging (MRI) measures have been the mainstay of Alzheimer's disease (AD) imaging research, however, ventricular morphometry analysis remains challenging because of its complicated topological structure. Here we describe a novel ventricular morphometry system based on the hyperbolic Ricci flow method and tensor-based morphometry (TBM) statistics. Unlike prior ventricular surface parameterization methods, hyperbolic conformal parameterization is angle-preserving and does not have any singularities. Our system generates a one-to-one diffeomorphic mapping between ventricular surfaces with consistent boundary matching conditions. The TBM statistics encode a great deal of surface deformation information that could be inaccessible or overlooked by other methods. We applied our system to the baseline MRI scans of a set of MCI subjects from the Alzheimer's Disease Neuroimaging Initiative (ADNI: 71 MCI converters vs. 62 MCI stable). Although the combined ventricular area and volume features did not differ between the two groups, our fine-grained surface analysis revealed significant differences in the ventricular regions close to the temporal lobe and posterior cingulate, structures that are affected early in AD. Significant correlations were also detected between ventricular morphometry, neuropsychological measures, and a previously described imaging index based on fluorodeoxyglucose positron emission tomography (FDG-PET) scans. This novel ventricular morphometry method may offer a new and more sensitive approach to study preclinical and early symptomatic stage AD.

Brain insulin resistance in Alzheimer's disease and its potential treatment with GLP-1 analogs

The prevalence of Alzheimer's disease is increasing rapidly in the absence of truly effective therapies. A promising strategy for developing such therapies is the treatment of brain insulin resistance, a common and early feature of Alzheimer's disease, closely tied to cognitive decline and capable of promoting many biological abnormalities in the disorder. The proximal cause of brain insulin resistance appears to be neuronal elevation in the serine phosphorylation of IRS-1, most likely due to amyloid-β-triggered microglial release of proinflammatory cytokines. Preclinically, the first line of defense is behavior-lowering peripheral insulin resistance (e.g., physical exercise and a Mediterranean diet supplemented with foods rich in flavonoids, curcumin and ω-3 fatty acids). More potent remediation is required, however, at clinical stages. Fortunately, the US FDA-approved antidiabetics exenatide (Byetta; Amylin Pharmaceuticals, Inc., CA, USA) and liraglutide (Victoza; Novo Nordisk A/S, Bagsvaerd, Denmark) are showing much promise in reducing Alzheimer's disease pathology and in restoring normal brain insulin responsiveness and cognitive function.

An empirically derived composite cognitive test score with improved power to track and evaluate treatments for preclinical Alzheimer's disease

BACKGROUND

There is growing interest in the evaluation of preclinical Alzheimer's disease (AD) treatments. As a result, there is a need to identify a cognitive composite that is sensitive to track preclinical AD decline to be used as a primary endpoint in treatment trials.

METHODS

Longitudinal data from initially cognitively normal, 70- to 85-year-old participants in three cohort studies of aging and dementia from the Rush Alzheimer's Disease Center were examined to empirically define a composite cognitive endpoint that is sensitive to detect and track cognitive decline before the onset of cognitive impairment. The mean-to-standard deviation ratios (MSDRs) of change over time were calculated in a search for the optimal combination of cognitive tests/subtests drawn from the neuropsychological battery in cognitively normal participants who subsequently progressed to clinical stages of AD during 2- and 5-year periods, using data from those who remained unimpaired during the same period to correct for aging and practice effects. Combinations that performed well were then evaluated for representation of relevant cognitive domains, robustness across individual years before diagnosis, and occurrence of selected items within top performing combinations.

RESULTS

The optimal composite cognitive test score comprised seven cognitive tests/subtests with an MSDR = 0.964. By comparison, the most sensitive individual test score was Logical Memory Delayed Recall with an MSDR = 0.64.

CONCLUSIONS

We have identified a composite cognitive test score representing multiple cognitive domains that has improved power compared with the most sensitive single test item to track preclinical AD decline and evaluate preclinical AD treatments. We are confirming the power of the composite in independent cohorts and with other analytical approaches, which may result in refinements, have designated it as the primary endpoint in the Alzheimer's Prevention Initiative's preclinical treatment trials for individuals at high imminent risk for developing symptoms due to late-onset AD.

Advances in MRI biomarkers for the diagnosis of Alzheimer's disease

With the prevalence of Alzheimer's disease (AD) predicted to increase substantially over the coming decades, the development of effective biomarkers for the early detection of the disease is paramount. In this short review, the main neuroimaging techniques which have shown potential as biomarkers for AD are introduced, with a focus on MRI. Structural MRI measures of the hippocampus and medial temporal lobe are still the most clinically validated biomarkers for AD, but newer techniques such as functional MRI and diffusion tensor imaging offer great scope in tracking changes in the brain, particularly in functional and structural connectivity, which may precede gray matter atrophy. These new advances in neuroimaging methods require further development and crucially, standardization; however, before they are used as biomarkers to aid in the diagnosis of AD.

An object location memory paradigm for older adults with and without mild cognitive impairment

BACKGROUND

Object-location memory is critical in every-day life and known to deteriorate early in the course of neurodegenerative disease.

NEW METHOD

We adapted the previously established learning paradigm "LOCATO" for use in healthy older adults and patients with mild cognitive impairment (MCI). Pictures of real-life buildings were associated with positions on a two-dimensional street map by repetitions of "correct" object-location pairings over the course of five training blocks, followed by a recall task. Correct/incorrect associations were indicated by button presses. The original two 45-item sets were reduced to 15 item-sets, and tested in healthy older adults and MCI for learning curve, recall, and re-test effects.

RESULTS

The two 15-item versions showed comparable learning curves and recall scores within each group. While learning curves increased linearly in both groups, MCI patients performed significantly worse on learning and recall compared to healthy controls. Re-testing after 6 month showed small practice effects only.

COMPARISON WITH EXISTING METHODS

LOCATO is a simple standardized task that overcomes several limitation of previously employed visuospatial task by using real-life stimuli, minimizing verbal encoding, avoiding fine motor responses, combining explicit and implicit statistical learning, and allowing to assess learning curve in addition to recall.

CONCLUSIONS

Results show that the shortened version of LOCATO meets the requirements for a robust and ecologically meaningful assessment of object-location memory in older adults with and without MCI. It can now be used to systematically assess acquisition of object-location memory and its modulation through adjuvant therapies like pharmacological or non-invasive brain stimulation.

CSF Biomarkers of Alzheimer’s Disease: Impact on Disease Concept, Diagnosis, and Clinical Trial Design

Data from clinicopathologic and biomarker studies have converged to support the view of Alzheimer’s disease (AD) as a continuum, with pathology developing decades prior to the onset of cognitive symptoms which culminate as dementia at the end stage of the disease. This concept is impacting disease nomenclature, diagnostic criteria, prognostic potential, and clinical trial design. Revisions to diagnostic criteria to incorporate biomarker results have recently been proposed in order to increase the confidence of AD as the underlying etiology of a clinical impairment and to permit a diagnosis of AD across the disease continuum, eventually perhaps in the asymptomatic period. Individuals in this preclinical stage are receiving intense focus as a targeted population for secondary prevention trials aimed at identifying disease-modifying therapies that have the best chance of preserving normal cognitive function. The goal is to bring validated biomarkers to clinical practice for the purpose of disease diagnosis, prognosis, and evaluation of therapeutic efficacy once disease-modifying treatments become available. Realization of this goal requires worldwide biomarker standardization efforts, consensus among researchers and clinicians regarding the clinical utility of assessing biomarkers in patient care settings, and eventually the endorsement and adoption of such procedures and practices into global health care systems.

Testing Aβ toxicity on primary CNS cultures using drug-screening microfluidic chips

Open microscale cultures of primary central nervous system (CNS) cells have been implemented in microfluidic chips that can expose the cells to physiological fluidic shear stress conditions. Cells in the chips were exposed to differently aggregated forms of beta-amyloid (Aβ), i.e. conditions mimicking an Alzheimer's Disease environment, and treated with CNS drugs in order to assess the contribution of glial cells during pharmacological treatments. FTY720, a drug approved for the treatment of Multiple Sclerosis, was found to play a marked neuroprotective role in neuronal cultures as well as in microglia-enriched neuronal cultures, preventing neurodegeneration after cell exposure to neurotoxic oligomers of Aβ.

Alzheimer's disease: relevant molecular and physiopathological events affecting amyloid-β brain balance and the putative role of PPARs

Alzheimer’s disease (AD) is the most common form of age-related dementia. With the expected aging of the human population, the estimated morbidity of AD suggests a critical upcoming health problem. Several lines of research are focused on understanding AD pathophysiology, and although the etiology of the disease remains a matter of intense debate, increased brain levels of amyloid-β (Aβ) appear to be a critical event in triggering a wide range of molecular alterations leading to AD. It has become evident in recent years that an altered balance between production and clearance is responsible for the accumulation of brain Aβ. Moreover, Aβ clearance is a complex event that involves more than neurons and microglia. The status of the blood-brain barrier (BBB) and choroid plexus, along with hepatic functionality, should be considered when Aβ balance is addressed. Furthermore, it has been proposed that exposure to sub-toxic concentrations of metals, such as copper, could both directly affect these secondary structures and act as a seeding or nucleation core that facilitates Aβ aggregation. Recently, we have addressed peroxisomal proliferator-activated receptors (PPARs)-related mechanisms, including the direct modulation of mitochondrial dynamics through the PPARγ-coactivator-1α (PGC-1α) axis and the crosstalk with critical aging- and neurodegenerative-related cellular pathways. In the present review, we revise the current knowledge regarding the molecular aspects of Aβ production and clearance and provide a physiological context that gives a more complete view of this issue. Additionally, we consider the different structures involved in AD-altered Aβ brain balance, which could be directly or indirectly affected by a nuclear receptor (NR)/PPAR-related mechanism.

A neurodegenerative vascular burden index and the impact on cognition

A wide range of vascular burden factors has been identified to impact vascular function and structure as indicated by carotid intima–media thickness (IMT). On the basis of their impact on IMT, vascular factors may be selected and clustered in a vascular burden index (VBI). Since many vascular factors increase the risk of Alzheimer’s disease (AD), a multifactorial neurodegenerative VBI may be related to early pathological processes in AD and cognitive decline in its preclinical stages. We investigated an elderly cohort at risk for neurodegeneration (TREND study, n = 1102) for the multifactorial influence of vascular burden factors on IMT measured by ultrasound. To create a VBI for this cohort, vascular factors and their definitions (considering medical history, medication, and/or blood marker data) were selected based on their statistical effects on IMT in multiple regressions including age and sex. The impact of the VBI on cognitive performance was assessed using the Trail-Making Test (TMT) and the consortium to establish a registry for Alzheimer’s disease (CERAD) neuropsychological battery. IMT was significantly predicted by age (standardized β = 0.26), sex (0.09; males > females) and the factors included in the VBI: obesity (0.18), hypertension (0.14), smoking (0.08), diabetes (0.07), and atherosclerosis (0.05), whereas other cardiovascular diseases or hypercholesterolemia were not significant. Individuals with 2 or more VBI factors compared to individuals without had an odds ratio of 3.17 regarding overly increased IMT ( ≥ 1.0 mm). The VBI showed an impact on executive control [log(TMT B−A), p = 0.047] and a trend toward decreased global cognitive function (CERAD total score, p = 0.057) independent of age, sex, and education. A VBI established on the basis of IMT may help to identify individuals with overly increased vascular burden linked to decreased cognitive function indicating neurodegenerative processes. The longitudinal study of this risk cohort will reveal the value of the VBI as prodromal marker for cognitive decline and AD.

Nutrient intake and brain biomarkers of Alzheimer's disease in at-risk cognitively normal individuals: a cross-sectional neuroimaging pilot study

OBJECTIVE

There is increasing evidence to suggest that diet, one of the most important modifiable environmental factors, may play a role in preventing or delaying cognitive decline and Alzheimer's disease (AD). This study examines the relationship between dietary nutrients and brain biomarkers of AD in cognitively normal individuals (NL) with and without AD risk factors.

DESIGN

As part of an ongoing brain imaging study, participants received clinical and laboratory examinations, a neurocognitive test battery, positron emission tomography (PET) with (11)C-Pittsburgh Compound-B (PiB; a measure of amyloid-β (Aβ) load) and (18)F-fluorodeoxyglucose (FDG; a proxy of neuronal activity), and completed semiquantitative food frequency questionnaires.

SETTING

Research centre affiliated with the Alzheimer's disease Core Center at New York University School of Medicine.

PARTICIPANTS

49 NL individuals (age 25-72 years, 69% women) with dietary information, (11)C-PiB and (18)F-FDG PET scans were examined.

RESULTS

Controlling for age and total caloric intake, higher intake of vitamin B12, vitamin D and ω-3 polyunsaturated fatty acid (PUFA) was associated with lower Aβ load in AD regions on PiB-PET, while higher intake of β-carotene and folate was associated with higher glucose metabolism on FDG-PET. β-carotene and folate were associated with reduced glucose metabolism for women, apolipoprotein E epsilon 4 (APOE4) carriers and participants with positive AD family history, but not for their risk-free counterparts. The associations of vitamin B12, vitamin D and ω-3 PUFA with PiB retention were independent of gender, APOE and family history. The identified nutrient combination was associated with higher intake of vegetables, fruit, whole grains, fish and legumes, and lower intake of high-fat dairies, meat and sweets.

CONCLUSIONS

Our data provide a potential pathophysiological mechanism for epidemiological findings showing that dietary interventions may play a role in the prevention of AD. Longitudinal studies are needed to determine whether there is a direct link between nutrient intake, brain biomarkers and risk of AD.

Circulating miRNAs as biomarkers for neurodegenerative disorders

Neurodegenerative disorders, such as Alzheimer’s disease (AD), Parkinson’s disease (PD) and frontotemporal dementias (FTD), are considered distinct entities, however, there is increasing evidence of an overlap from the clinical, pathological and genetic points of view. All neurodegenerative diseases are characterized by neuronal loss and death in specific areas of the brain, for example, hippocampus and cortex for AD, midbrain for PD, frontal and temporal lobes for FTD. Loss of neurons is a relatively late event in the progression of neurodegenerative diseases that is typically preceded by other events such as metabolic changes, synaptic dysfunction and loss, neurite retraction, and the appearance of other abnormalities, such as axonal transport defects. The brain’s ability to compensate for these dysfunctions occurs over a long period of time and results in late clinical manifestation of symptoms, when successful pharmacological intervention is no longer feasible. Currently, diagnosis of AD, PD and different forms of dementia is based primarily on analysis of the patient’s cognitive function. It is therefore important to find non-invasive diagnostic methods useful to detect neurodegenerative diseases during early, preferably asymptomatic stages, when a pharmacological intervention is still possible. Altered expression of microRNAs (miRNAs) in many disease states, including neurodegeneration, and increasing relevance of miRNAs in biofluids in different pathologies has prompted the study of their possible application as neurodegenerative diseases biomarkers in order to identify new therapeutic targets. Here, we review what is known about the role of miRNAs in the pathogenesis of neurodegeneration and the possibilities and challenges of using these small RNA molecules as a signature for neurodegenerative conditions.

Building a pipeline to discover and validate novel therapeutic targets and lead compounds for Alzheimer's disease

Cognitive decline, Alzheimer's disease (AD) and other causes are major public health problems worldwide. With changing demographics, the number of persons with dementia will increase rapidly. The treatment and prevention of AD and other dementias, therefore, is an urgent unmet need. There have been considerable advances in understanding the biology of many age-related disorders that cause dementia. Gains in understanding AD have led to the development of ante-mortem biomarkers of traditional neuropathology and the conduct of several phase III interventions in the amyloid-β cascade early in the disease process. Many other intervention strategies are in various stages of development. However, efforts to date have met with limited success. A recent National Institute on Aging Research Summit led to a number of requests for applications. One was to establish multi-disciplinary teams of investigators who use systems biology approaches and stem cell technology to identify a new generation of AD targets. We were recently awarded one of three such grants to build a pipeline that integrates epidemiology, systems biology, and stem cell technology to discover and validate novel therapeutic targets and lead compounds for AD treatment and prevention. Here we describe the two cohorts that provide the data and biospecimens being exploited for our pipeline and describe the available unique datasets. Second, we present evidence in support of a chronic disease model of AD that informs our choice of phenotypes as the target outcome. Third, we provide an overview of our approach. Finally, we present the details of our planned drug discovery pipeline.

The end of Alzheimer's disease--from biochemical pharmacology to ecopsychosociology: a personal perspective

The future of the Alzheimer's disease (AD) field involves a more complete understanding not only the state of current scientific approaches, but also the linguistic and cultural context of preclinical and clinical research and policy activities. The challenges surrounding dementia are large and growing but are only part of broader social and health concerns. In this latter context, the current state of research in the AD area is reviewed together with necessary priorities in moving forward. Creating a more optimistic future will depend less on genetic and reductionist approaches and more on environmental and intergenerative approaches that will aid in recalibrating the study of AD from an almost exclusive focus on biochemical, molecular and genetic aspects to better encompass "real world" ecological and psychosocial models of health.