Cognitive phenotypes in Alzheimer's disease and genetic variants in ACE and IDE

Long-term characterization of cognitive phenotypes in children with seizures over 36 months

RATIONALE

Children with new-onset epilepsies often exhibit co-morbidities including cognitive dysfunction, which adversely affects academic performance. Application of unsupervised machine learning techniques has demonstrated the presence of discrete cognitive phenotypes at or near the time of diagnosis, but there is limited knowledge of their longitudinal trajectories. Here we investigate longitudinally the presence and progression of cognitive phenotypes and academic status in youth with new-onset seizures as sibling controls.

METHODS

282 subjects (6-16 years) were recruited within 6 weeks of their first recognized seizure along with 167 unaffected siblings. Each child underwent a comprehensive neuropsychological assessment at baseline, 18 and 36 months later. Factor analysis of the neuropsychological tests revealed four underlying domains - language, processing speed, executive function, and verbal memory. Latent trajectory analysis of the mean factor scores over 36 months identified clusters with prototypical cognitive trajectories.

RESULTS

Three unique phenotypic groups with distinct cognitive trajectories over the 36-month period were identified: Resilient, Average, and Impaired phenotypes. The Resilient phenotype exhibited the highest neuropsychological factor scores and academic performance that were all similar to controls; while the Impaired phenotype showed the polar opposite with the worst performances across all test metrics. These findings remained significant and stable over 36 months. Multivariate logistic regression indicated that age of onset, EEG, neurological examination, and sociodemographic disadvantage were associated with phenotype classification.

CONCLUSIONS

This study demonstrates the presence of diverse latent cognitive trajectory phenotypes over 36 months in youth with new-onset seizures that are associated with a stable neuropsychological and academic performance longitudinally.

Overlapping and distinct phenotypic profiles in Alzheimer's disease and late onset epilepsy: a biologically-based approach

Due to shared hippocampal dysfunction, patients with Alzheimer's dementia and late-onset epilepsy (LOE) report memory decline. Multiple studies have described the epidemiological, pathological, neurophysiological, and behavioral overlap between Alzheimer's Disease and LOE, implying a bi-directional relationship. We describe the neurobiological decline occurring at different spatial in AD and LOE patients, which may explain why their phenotypes overlap and differ. We provide suggestions for clinical recognition of dual presentation and novel approaches for behavioral testing that reflect an "inside-out," or biologically-based approach to testing memory. New memory and language assessments could detect-and treat-memory impairment in AD and LOE at an earlier, actionable stage.

Deep phenotyping of Alzheimer's disease leveraging electronic medical records identifies sex-specific clinical associations

Alzheimer's Disease (AD) is a neurodegenerative disorder that is still not fully understood. Sex modifies AD vulnerability, but the reasons for this are largely unknown. We utilize two independent electronic medical record (EMR) systems across 44,288 patients to perform deep clinical phenotyping and network analysis to gain insight into clinical characteristics and sex-specific clinical associations in AD. Embeddings and network representation of patient diagnoses demonstrate greater comorbidity interactions in AD in comparison to matched controls. Enrichment analysis identifies multiple known and new diagnostic, medication, and lab result associations across the whole cohort and in a sex-stratified analysis. With this data-driven method of phenotyping, we can represent AD complexity and generate hypotheses of clinical factors that can be followed-up for further diagnostic and predictive analyses, mechanistic understanding, or drug repurposing and therapeutic approaches.

Associations of cerebrovascular metabolism genotypes with neuropsychiatric symptoms and age at onset of Alzheimer's disease dementia

Objective:

To study associations of cerebrovascular metabolism genotypes and haplotypes with age at Alzheimer’s disease dementia (AD) onset and with neuropsychiatric symptoms according to each dementia stage.

Methods:

Consecutive outpatients with late-onset AD were assessed for age at dementia onset and Neuropsychiatric Inventory scores according to Clinical Dementia Rating scores, apolipoprotein E gene (APOE) haplotypes, angiotensin-converting enzyme gene (ACE) variants rs1800764 and rs4291, low-density lipoprotein cholesterol receptor gene (LDLR) variants rs11669576 and rs5930, cholesteryl ester transfer protein gene (CETP) variants I422V and TaqIB, and liver X receptor beta gene (NR1H2) polymorphism rs2695121.

Results:

Considering 201 patients, only APOE-ɛ4 carriers had earlier dementia onset in multiple correlations, as well as less apathy, more delusions, and more aberrant motor behavior. Both ACE polymorphisms were associated with less intense frontally mediated behaviors. Regarding LDLR variants, carriers of the A allele of rs11669576 had less anxiety and more aberrant motor behavior, whereas carriers of the A allele of rs5930 had less delusions, less anxiety, more apathy, and more irritability. CETP variants that included G alleles of I422V and TaqIB were mostly associated with less intense frontally mediated behaviors, while severely impaired carriers of the T allele of rs2695121 had more anxiety and more aberrant motor behavior.

Conclusion:

Though only APOE haplotypes affected AD onset, cerebrovascular metabolism genotypes were associated with differences in several neuropsychiatric manifestations of AD.

Association of Increased Serum ACE Activity with Logical Memory Ability in Type 2 Diabetic Patients with Mild Cognitive Impairment

Background: Angiotensin-converting enzyme (ACE) is involved in the chronic complications of type 2 diabetes mellitus (T2DM) and Alzheimer's disease. This study aimed to assess the pathogenetic roles of ACE and the genetic predisposition of its insertion/deletion (I/D) polymorphism in mild cognitive impairment (MCI) among T2DM patients.

Methods: A total of 210 T2DM patients were enrolled. Among these patients, 116 satisfied the MCI diagnostic criteria and 94 exhibited healthy cognition. The cognitive functions of the patients were extensively assessed. The serum level and activity of ACE were measured via enzyme-linked immunosorbent assay and ultraviolet spectrophotography. The single-nucleotide polymorphisms of I/D gene of ACE were analyzed.

Results: The serum level and activity of ACE in diabetic MCI patients (p = 0.022 and p = 0.008, respectively) were both significantly higher than those in the healthy controls. A significant negative correlation was found between their ACE activity and logical memory test score (LMT) (p = 0.002). Multiple stepwise regression iterated the negative correlation between ACE activity and LMT score (p = 0.035). Although no significant difference was found in the genotype or allele distribution of ACE I/D polymorphism between the groups, the serum levels and activity of ACE were higher in the DD group than in the ID and II groups (p < 0.05).

Conclusions: Serum ACE activity could better predict logical memory in T2DM patients than ACE level. Further investigations on a large population size are necessary to test whether the D-allele of the ACE gene polymorphism is susceptible to memory deterioration.

Association between ACE polymorphism, cognitive phenotype and APOE E4 allele in a Tunisian population with Alzheimer disease

Angiotensin-converting enzyme (ACE) has shown altered activity in patients with neurological diseases. An insertion/deletion (I/D) polymorphism of the ACE gene encoding angiotensin-converting enzyme has been reported to be associated with the risk for Alzheimer's disease (AD), and is generally considered to be a disorder primarily affecting memory. We conducted a case-control study in a sample composed of 85 sporadic AD patients and 90 age- and sex-matched controls to investigate the possible effect of the polymorphism and cognitive profile. Our data revealed an association between the ACE polymorphism and AD risk. There was a significant difference in the ACE allele or genotype frequencies between cases and controls. The D/D genotype showed an increased risk for AD and in the amnestic group and the effect was independent on ApoE genotypes.

Distinct cognitive phenotypes in Alzheimer's disease in older people

BACKGROUND

Alzheimer's disease (AD) is considered to be a disorder predominantly affecting memory. It is increasingly recognized that the cognitive profile may be heterogeneous. We hypothesized that it would be possible to define distinct “cognitive phenotypes” in older people with AD.

METHODS

Participants from three individual studies were included, consisting of 109 patients with a diagnosis of probable AD, and 91 age- and gender-matched control participants. All had demographic and cognitive assessment data available, including the Cambridge Cognitive Examination of the Elderly (CAMCOG). The CAMCOG scores and sub-scores were further analyzed using hierarchical cluster analysis and factor analysis.

RESULTS

Three clusters were identified. The scores loaded onto three factors representing the domains of attention, praxis, calculation, and perception; memory; and language comprehension and executive function. The main difference between the clusters related to degree of memory impairment. The composite score for memory between the clusters remained significantly different despite adjustment for illness duration and age of onset (p < 0.001).

CONCLUSIONS

These data suggest clinical heterogeneity within an older group of people with AD. This may have implications for diagnosis, prognosis, response to currently available treatments, and the development of novel therapies.

IDE (rs6583817) polymorphism and type 2 diabetes differentially modify executive function in older adults

We tested independent and interactive contributions of a recently noted and promising insulin degrading enzyme polymorphism (IDE; rs6583817) and type 2 diabetes (T2D) to executive function performance, concurrently and longitudinally. Regarding normal neurocognitive decline and Alzheimer's disease, T2D is a known risk factor and this IDE variant might contribute risk or risk reduction via the minor (A) or major (G) allele. We compared normal aging and T2D groups (baseline n = 574; ages 53-95 years) over 2 longitudinal waves (mean interval = 4.4 years). We used confirmatory factor analysis, latent growth curve modeling, and path analysis. A confirmed single-factor model of 4 executive function tasks established the cognitive phenotype. This IDE variant predicted concurrent group differences and differential change in cognitive performance. Furthermore, the IDE major allele reduced risk of cognitive decline. T2D predicted performance only concurrently. Both IDE and T2D are associated with executive function levels in older adults, but only IDE moderated 2-wave change. Previously linked to Alzheimer's disease, this IDE variant should be further explored for its potential influence on cognitive phenotypes of normal aging.

Are amyloid-degrading enzymes viable therapeutic targets in Alzheimer's disease?

: The amyloid cascade hypothesis of Alzheimer's disease envisages that the initial elevation of amyloid β-peptide (Aβ) levels, especially of Aβ(1-42) , is the primary trigger for the neuronal cell death specific to onset of Alzheimer's disease. There is now substantial evidence that brain amyloid levels are manipulable because of a dynamic equilibrium between their synthesis from the amyloid precursor protein and their removal by amyloid-degrading enzymes (ADEs) providing a potential therapeutic strategy. Since the initial reports over a decade ago that two zinc metallopeptidases, insulin-degrading enzyme and neprilysin (NEP), contributed to amyloid degradation in the brain, there is now an embarras de richesses in relation to this category of enzymes, which currently number almost 20. These now include serine and cysteine proteinases, as well as numerous zinc peptidases. The experimental validation for each of these enzymes, and which to target, varies enormously but up-regulation of several of them individually in mouse models of Alzheimer's disease has proved effective in amyloid and plaque clearance, as well as cognitive enhancement. The relative status of each of these enzymes will be critically evaluated. NEP and its homologues, as well as insulin-degrading enzyme, remain as principal ADEs and recently discovered mechanisms of epigenetic regulation of NEP expression potentially open new avenues in manipulation of AD-related genes, including ADEs.