Apolipoprotein ɛ4 and neuropsychological performance in Alzheimer's disease and vascular dementia

APOE ε4 influences cognitive decline positively in APP and negatively in PSEN1 mutation carriers with autosomal-dominant Alzheimer's disease

BACKGROUND AND PURPOSE

The aim was to investigate the effect of APOE ε4 allele on cognitive decline in adAD. Presence of the APOE ε4 allele reduces age of symptom onset, increases disease progression, and lowers cognitive performance in sporadic Alzheimer's disease (AD), while the impact of the APOE ε4 allele in autosomal-dominant AD (adAD) is incompletely known.

METHODS

Mutation carriers (MCs; n = 39) and non-carriers (NCs; n = 40) from six adAD families harbouring a mutation in the APP (28 MCs and 25 NCs) or the PSEN1 genes (11 MCs and 15 NCs) underwent repeated cognitive assessments. A timeline of disease course was defined as years to expected age of clinical onset (YECO) based on history of disease onset in each family. The MC and NC groups were comparable with regard to demographics and prevalence of the APOE ε4 allele. The relationship between cognitive decline and YECO, YECO2 , education, APOE, and APOE-by-YECO interaction was analysed using linear mixed-effects models.

RESULTS

The trajectory of cognitive decline was significantly predicted by linear and quadratic YECO and education in MCs and was determined by age and education in NCs. Adding APOE ε4 allele (presence/absence) as a predictor did not change the results in the MC and NC groups. The outcome also remained the same for MCs and NCs after adding the APOE-by-YECO interaction as a predictor. Analyses of APP and PSEN1 MCs separately showed favourable APOE-by-YECO interaction in APP (less steep decline) and unfavourable interaction in PSEN1 (steeper decline), linked to the APOE ε4 allele.

CONCLUSION

The APOE ε4 allele influences cognitive decline positively in APP and negatively in PSEN1 mutation carriers with adAD, indicating a possible antagonistic pleiotropy.

APOE genotype, hippocampus, and cognitive markers of Alzheimer's disease in American Indians: Data from the Strong Heart Study

BACKGROUND

The apolipoprotein E (APOE) ε4 allele confers higher risk of neurodegeneration and Alzheimer's disease (AD), but differs by race/ethnicity. We examined this association in American Indians.

METHODS

The Strong Heart Study is a population-based cohort of American Indians who were 64 to 95 years of age in 2010 to 2013. APOE ε4 status, brain imaging, and neuropsychological testing was collected in N = 811 individuals. Summary statistics, graphics, and generalized linear regressions-adjusted for sociodemographics, clinical features, and intracranial volume with bootstrap variance estimator-compared APOE ε4 carriers with non-carriers.

RESULTS

APOE ε4 carriers comprised 22% of the population (0.7% homozygotes). Participants were mean 73 years, 67% female, and 54% had some college education. The majority were obese (>50%), hypertensive (>80%), and diabetic (>50%). Neither imaging findings nor multidomain cognitive testing showed any substantive differences between APOE ε4 carriers and non-carriers.

CONCLUSION

We found no evidence of neurodegenerative risk from APOE ε4 in American Indians. Additional studies are needed to examine potential protective features.

Benefit of phonemic cueing on confrontation naming in Alzheimer's disease

Objective: Deficits in confrontation naming vary among persons with Alzheimer's disease (AD), including the extent to which phonemic cueing is helpful in generating the target word. This study examined neuropsychological correlates of phonemic cueing benefit and the influential effects of AD severity, estimated premorbid intellectual functioning, and apolipoprotein E genotype status.Method: Participants were 1104 individuals with mild to moderate AD who were administered the Boston Naming Test (BNT) as part of their initial neuropsychological evaluation.Results: Mild AD subjects benefited from phonemic cues significantly more than moderate AD subjects. Individuals with higher estimated premorbid IQ benefited more from phonemic cueing. Differences in phonemic cueing benefit between carriers and noncarriers of the ApoE ε4 allele were accounted for by naming ability, with carriers performing better on naming tasks compared to noncarriers. Phonemic cueing benefit uniquely contributed to cognitive performance on some semantic measures, phonemic fluency, and one nonsemantic visuospatial task.Conclusion: Individuals with probable AD who benefit more from phonemic cueing during confrontation naming tend to have higher estimated premorbid IQ and are milder in dementia severity. There is a positive association between phonemic cueing benefit and performance on select semantic measures and verbal fluency. Differences in phonemic cueing benefit between carriers and noncarriers of APOE ε4 allele can be explained by spontaneous naming performance. Results suggest complexity of underlying mechanisms involving confrontation naming, phonemic cueing, and lexical access and the factors that influence them.

Cognitive Dysfunction and Single Nucleotide Polymorphisms in Hepatitis C Virus-Infected Persons: A Systematic Review

The aim of this study was to realize a systematic review to identify data reported in the literature involving people infected by hepatitis C virus (HCV) with cognitive dysfunctions and single nucleotide polymorphisms (SNPs). The research was realized in six databases and the selection of studies was performed in two stages. Initially, we searched indexed articles from the following electronic databases: SciELO, MEDLINE, PubMed, HighWire, LILACS, and ScienceDirect. Then the articles were completely read and those that did not meet the eligibility criteria were excluded. Therefore, 5,669 articles were obtained and, of these, 25 were selected. Finally, one article involving people with HCV and cognitive impairment was included in the review. The frequency of the APOE-ɛ4 allele in people with HCV and mild liver disease was significantly lower in those with work memory impairment (p = 0.003) and attention (p = 0.008). This situation differs from other studies that showed an association between ɛ4 allele high frequency and cognitive decline. Thus, studies with larger samples involving people with HCV, cognitive alterations, and SNPs are necessary, in view of the lack of this theme in the literature and the divergences in the findings.

Analysis of genetics and risk factors of Alzheimer's Disease

Alzheimer's Disease is the leading neurodegenerative cause of dementia. The pathogenesis is not clearly understood yet, is believed to be the complex interaction between genetic and environmental factors. Consequently vascular risk factors and Apolipoprotein E genotyping are increasingly gaining importance. This study aimed at assessing the relationships between Alzheimer's Disease and Apolipoprotein E phenotype and vascular risk factors. Patients diagnosed with "possible Alzheimer's Disease" in the Gazi University, Department of Neurology, were included in the study and age-matched volunteer patients who attended the polyclinic were included as a control group. In this study, the risk factors including low education level, smoking, hyperlipidemia, higher serum total cholesterol levels, and hyperhomocysteinemia were found to be statistically significantly more common in the Alzheimer's Disease group in comparison to the Control Group, while all Apolipoprotein E ε4/ε4 genotypes were found in the Alzheimer's Disease group. The presence of the Apolipoprotein E ε4 allele is believed to increase vascular risk factors as well as to affect Alzheimer's Disease directly. The biological indicators which are used in identifying the patients' genes will be probably used in the treatment plan of the patients in the future.

Apolipoprotein E polymorphisms increase the risk of post-stroke depression

Recent reports have shown that apolipoprotein E (APOE) polymorphisms are involved in neurodegenerative disease. However, it is unclear whether APOE affects post-stroke depression. Accordingly, we hypothesized that APOE polymorphisms modify the risk of post-stroke depression. Here, we performed a hospital-based case-control study (including 76 cerebral infarction cases with post-stroke depression, 88 cerebral infarction cases without post-stroke depression, and 109 controls without any evidence of post-stroke depression or cerebral infarction) to determine possible association between APOE rs429358 and rs7412 polymorphisms and risk of post-stroke depression. Our findings show no difference among the groups with regards genotype distribution of the rs7412 polymorphism. In contrast, APOE genotypes with rs429358-C alleles increased the risk of post-stroke depression. Further, the rs429358 polymorphism was associated with significantly decreased regional cerebral blood flow values in the left temporal lobe of post-stroke depression cases. Additionally, the rs429358 polymorphism was not only associated with depression severity, but with increasing serum levels of total cholesterol. These results suggest that the APOE rs429358 polymorphism is associated with increased risk of developing post-stroke depression, and that APOE rs429358-C allele genotypes may be detrimental to recovery of nerve function after stoke. Indeed, these findings provide clinical data for future post-stroke depression gene interventions.

Lack of reliable evidence for a distinctive ε4-related cognitive phenotype that is independent from clinical diagnostic status: findings from the Australian Imaging, Biomarkers and Lifestyle Study

Individuals who carry the apolipoprotein E ε4 polymorphism have an increased risk of late-onset Alzheimer's disease. However, because possession of the ε4 allele confers an increased risk for the diagnosis of dementia, it has proven problematic in older individuals to dissociate the influence of ε4 on cognitive capacity per se as distinct from its influence on clinical diagnostic status. We report a statistical approach that attempts to partial out the influence of diagnostic group membership (Alzheimer's disease, mild cognitive impairment, healthy control) from the influence of apolipoprotein ε4 genetic status on cognitive functioning. The cognitive phenotype hypothesis predicts that ε4-positive individuals will show cognitive deficits (relative to matched ε4-negative individuals) independent of the development of Alzheimer's disease. By contrast, the prodromal/preclinical Alzheimer's disease hypothesis proposes that the effect of apolipoprotein E status on cognitive performance is a function of the increased risk of dementia in individuals with the ε4 allele. We evaluated these hypotheses in the Australian Imaging, Biomarkers and Lifestyle cohort (n = 1112). We first determined whether previously reported findings concerning ε4 status and age-related neuropsychological performance could be explained by the inadvertent recruitment of people with mild cognitive impairment into the healthy control group. We then tested each diagnostic group in isolation to identify any neuropsychological patterns that may be attributed to the ε4 allele. Finally, as interactions between the ε4 allele and age have previously been reported in cognitive functioning within healthy elderly populations, we attempted to determine whether the inclusion of mild cognitively impaired individuals in the sample may drive this relationship. An extensive battery of standardized, well-validated neuropsychological tasks was administered to a final sample of 764 healthy control subjects, 131 individuals with mild cognitive impairment and 168 individuals with Alzheimer's disease. The effect of the ε4 allele on cognitive performance was assessed using a statistical mediation analysis and supplemented with Bayesian methods to address a number of the limitations associated with Fisherian/Neyman-Pearsonian significance testing. Our findings support the prodromal/preclinical Alzheimer's disease hypothesis and do not support the concept of a distinctive ε4-related cognitive phenotype.

Normative data for healthy older adults and an abbreviated version of the Stroop test

Normative data for the Kaplan version of the Stroop Test are presented for 153 healthy, cognitively intact older adults aged 50-89 years. Increasing age was associated with decreased performance on all three subtests (Stroop A, Stroop B, and Stroop C), while years of education was only associated with Stroop B performance. Hence the normative data were stratified by age into three groups (50-64, 65-74, 75-89). Completion times for the first half of each trial (half-time scores) were found to have good split-half reliability and correlated highly with the original full administration scores. Means and standard deviations for the half-time administration are also presented for this sample. The current study provides more comprehensive normative data for older adults than previously available, as well as normative information for half-time scores that may have future clinical utility as an alternative, abbreviated version of the Kaplan Stroop Test.

Apolipoprotein E gene polymorphism in a Chinese population with vascular dementia: a meta-analysis

BACKGROUND

Apolipoprotein E (ApoE) gene has been reported to be associated with the development of vascular dementia (VD); however, results from observational studies are conflicting.

METHODS

We surveyed all case-control studies on ApoE gene and VD patients with comprehensive search and review of the references. A meta-analysis was performed to demonstrate the association of ApoE gene with VD by random effects models. The association was assessed by odds ratio (OR) with 95% confidence intervals (CI).

RESULTS

A total of 18 studies including 935 patients and 1,686 controls were eligible and abstracted. ApoE ε3/4 and ε4/4 genotype, as well as ε4 allele (OR = 1.95, 95% CI: 1.52-2.49; OR = 3.47, 95% CI: 1.85-6.51 and OR = 2.12, 95% CI: 1.64-2.74, respectively) were associated with an increased risk of VD, while ApoE ε3/3 genotype and ε3 allele (OR = 0.65, 95% CI: 0.53-0.79 and OR = 0.65, 95% CI: 0.53-0.80, respectively) trended to protect against VD. There was no significant difference in ApoE ε2 allele frequency, ε2/2, ε2/3 or ε2/4 genotype between VD and controls (OR = 0.85, 95% CI: 0.61-1.17; OR = 0.89, 95% CI: 0.39-2.01; OR = 0.82, 95% CI: 0.61-1.09 and OR = 1.03, 95% CI: 0.57-1.84, respectively).

CONCLUSIONS

Our results support a genetic association between ApoE polymorphism and VD in the Chinese population.