Apolipoprotein E genotypes associated with Alzheimer disease and concomitant stroke

The link between Alzheimer's disease and stroke: A detrimental synergism

Being age-related disorders, both Alzheimer's disease (AD) and stroke share multiple risk factors, such as hypertension, smoking, diabetes, and apolipoprotein E (APOE) Ɛ4 genotype, and coexist in patients. Accumulation of amyloid-β plaques and neurofibrillary tangled impair cognitive potential, leading to AD. Blocked blood flow in the neuronal tissues, causes neurodegeneration and cell death in stroke. AD is commonly characterized by cerebral amyloid angiopathy, which significantly elevates the risk of hemorrhagic stroke. Patients with AD and stroke have been both reported to exhibit greater cognitive impairment, followed by multiple pathophysiological mechanisms shared between the two. The manuscript aims to elucidate the relationship between AD and stroke, as well as the common pathways and risk factors while understanding the preventive therapies that might limit the negative impacts of this correlation, with diagnostic modalities and current AD treatments. The authors provide a comprehensive review of the link and aid the healthcare professionals to identify suitable targets and risk factors, that may retard cognitive decline and neurodegeneration in patients. However, more intricate research is required in this regard and an interdisciplinary approach that would target both the vascular and neurodegenerative factors would improve the quality of life in AD patients.

Common Genetic Factors and Pathways in Alzheimer's Disease and Ischemic Stroke: Evidences from GWAS

Alzheimer's disease (AD) and ischemic stroke (IS) are common neurological disorders, and the comorbidity of these two brain diseases is often seen. Although AD and IS were regarded as two distinct disease entities, in terms of different etiologies and clinical presentation, recent genome-wide association studies (GWASs) revealed that there were common risk genes between AD and IS, indicating common molecular pathways and their common pathophysiology. In this review, we summarize AD and IS risk single nucleotide polymorphisms (SNPs) and their representative genes from the GWAS Catalog database, and find thirteen common risk genes, but no common risk SNPs. Furthermore, the common molecular pathways associated with these risk gene products are summarized from the GeneCards database and clustered into inflammation and immunity, G protein-coupled receptor, and signal transduction. At least seven of these thirteen genes can be regulated by 23 microRNAs identified from the TargetScan database. Taken together, the imbalance of these molecular pathways may give rise to these two common brain disorders. This review sheds light on the pathogenesis of comorbidity of AD and IS, and provides molecular targets for disease prevention, manipulation, and brain health maintenance.

Apolipoprotein E ε4 Polymorphism as a Risk Factor for Ischemic Stroke: A Systematic Review and Meta-Analysis

Introduction

Rising studies indicate that the apolipoprotein E (APOE) gene is related to the susceptibility of ischemic stroke (IS). However, certain consensus is limited by the lack of a large sample size of researches. This meta-analysis was performed to explore the potential association between the APOE gene and IS.

Methods

To identify relevant case control studies in English publications by October 2020, we searched PubMed, Embase, Web of Science, and the Cochrane Library. Pooled odds ratios (ORs) with fixed- or random-effect models and corresponding 95% confidence intervals (CIs) were calculated to analyze potential associations.

Results

A total of 55 researches from 32 countries containing 12207 IS cases and 27742 controls were included. The association between APOE gene ε4 mutation and IS was confirmed (ε4 vs. ε3 allele: pooled OR = 1.374, 95% CI, 1.214-1.556; ε2/ε4 vs. ε3/ε3: pooled OR = 1.233, 95% CI, 1.056-1.440; ε3/ε4 vs. ε3/ε3: pooled OR = 1.340, 95% CI, 1.165-1.542; ε4/ε4 vs. ε3/ε3: pooled OR = 1.833, 95% CI, 1.542-2.179; and APOE ε4 carriers vs. non-ε4 carriers: pooled OR = 1.377; 95% CI, 1.203-1.576). Interestingly, APOE ε4 mutation showed a dose-response correlation with IS risk (ε4/ε4 vs. ε2/ε4: pooled OR = 1.625; 95% CI, 1.281-2.060; ε4/ε4 vs. ε3/ε4: pooled OR = 1.301; 95% CI, 1.077-1.571). Similar conclusions were drawn in the small artery disease (SAD) subtype, but not in large artery atherosclerosis (LAA) or in cardioaortic embolism (CE), by subgroup analysis.

Conclusions

These observations reveal that specific APOE ε4 mutation was significantly associated with the risk of IS in a dose-dependent manner, while APOE ε4 mutation was related to SAD subtype onset without a cumulative effect.

Genetic Variants Associated With Alzheimer Disease in the 22 Arab Countries: A Systematic Review

BACKGROUND AND AIMS

Alzheimer disease (AD) is a progressive and complex neurodegenerative disease. Approximately 70% of AD risk is attributed to genetic risk factors, including variants in amyloid precursor protein (APP), presenilin 1 (PSEN1), and presenilin 2 (PSEN2) genes. Several studies have revealed a considerable number of candidate loci and genes for AD among different ethnic populations. However, the outcomes of these studies have been inconsistent. In this study, we aimed to investigate the spectrum of variants that are associated with the onset and development of AD among 22 Arab countries.

METHODOLOGY

We systematically searched 4 literature databases (Science Direct, Scopus, PubMed, and Web of Science) from the date of inception until July 2020 using various search terms to obtain all the reported genetic data on Arab AD cases.

RESULTS

In total, 18 studies were included, comprising a total of 2173 individuals, of whom 888 were clinically diagnosed AD patients and were genetically tested for genes and variants associated with AD. A total of 27 variants in 8 genes were found to be associated with AD. Of these variants, 17 were unique to the Arab population and 10 were shared with other ethnic groups.

CONCLUSIONS

There is a dearth of studies on the genetics of AD in the Arab world. There seems to be distinctive genetic and clinical susceptibility profiles for Arab patients with AD.

Absolute 10-year risk of dementia by age, sex and APOE genotype: a population-based cohort study

BACKGROUND

Dementia is a major cause of disability, and risk-factor reduction may have the potential to delay or prevent the disease. Our aim was to determine the absolute 10-year risk of dementia, by age, sex and apolipoprotein E (APOE) genotype.

METHODS

We obtained data from the Copenhagen General Population Study (from 2003 to 2014) and the Copenhagen City Heart Study (from 1991 to 1994 and 2001 to 2003). Participants underwent a questionnaire, physical examination and blood sampling at baseline. Diagnoses of dementia and cerebrovascular disease were obtained from the Danish National Patient Registry up to Nov. 10, 2014.

RESULTS

Among 104 537 individuals, the absolute 10-year risk of Alzheimer disease in 3017 women and men who were carriers of the APOE ɛ44 genotype was, respectively, 7% and 6% at age 60-69 years, 16% and 12% at age 70-79 years, and 24% and 19% at age 80 years and older. Corresponding values for all dementia were 10% and 8%, 22% and 19%, and 38% and 33%, respectively. Adjusted hazard ratios (HRs) for all dementia increased by genotype, from genotype ɛ22 to ɛ32 to ɛ33 to ɛ42 to ɛ43 to ɛ44 (p for trend < 0.001). Compared with ɛ33 carriers, ɛ44 carriers were more likely to develop Alzheimer disease (adjusted HR 8.74, 95% confidence interval [CI] 7.08-10.79), vascular dementia (adjusted HR 2.87, 95% CI 1.54-5.33), unspecified dementia (adjusted HR 4.68, 95% CI 3.74-5.85) and all dementia (adjusted HR 5.77, 95% CI 4.89-6.81).

INTERPRETATION

Age, sex and APOE genotype robustly identify high-risk groups for Alzheimer disease and all dementia. These groups can potentially be targeted for preventive interventions.

The relationship between genetic polymorphisms in apolipoprotein E (ApoE) gene and osteonecrosis of the femoral head induced by steroid in Chinese Han population

Previous studies suggested that apolipoprotein E (ApoE) genetic polymorphisms (SNPs) may result in abnormal lipid metabolism. Therefore, genetic polymorphisms in ApoE may be associated with the occurrence of osteonecrosis of the femoral head (ONFH). A case control study was designed to include 580 patients with steroid-induced ONFH and 560 age- and sex-matched non steroid-induced ONFH control subjects to analyze the association between ApoE polymorphisms and susceptibility of steroid-induced ONFH. Polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) method was utilized to differentiate two genotypes SNPs (rs7412 C/T and rs429358 T/C) in ApoE gene. Both rs7412 C/T and rs429358 T/C were found to be associated with the risk of steroid-induced ONFH. However, no significant association was observed between the haplotypes T-T, T-C and C-C in ONFH. Furthermore, T allele of rs7412 and C allele of rs429358 carriers were associated with higher levels of TG in steroid-induced ONFH patients (P < 0.05). The study suggested that ApoE genetic polymorphisms conferred susceptibility to steroid-induced ONFH in Chinese Han population. However, the results need further investigation with large sample size and various populations.

Serum Aβ is predictive for short-term neurological deficits after acute ischemic stroke

Mounting evidence suggests that ischemic stroke (IS) is associated with Alzheimer's disease (AD). IS and vascular risk factors increase the risk for AD. However, whether AD pathologies exist in IS and the effects of these pathologies on stroke remain unknown. In the present study, we aimed to investigate the alterations of serum Aβ after acute IS (AIS), and its correlations with the neurological deficits, infarction volume, and site after stroke. AIS patients (n = 35) were recruited within 24 h of symptom onset. Age- and gender-matched AD patients (n = 48) and cognitively normal controls (NC, n = 37) were also enrolled. Serum Aβ40 and Aβ42 and the National Institute of Health Stroke Scale Score (NIHSS) were measured on day 1, 3, and 7 after stroke onset. We found that serum Aβ40 and Aβ42 levels were increased at day 1 and reached peak levels at day 3, and decreased to pre-stroke levels at day 7. Serum Aβ40 levels at day 1 were correlated with the NIHSS scores and infarction volume of AIS patients. Serum Aβ42 levels at day 1 were significantly higher in IS patients with dominant gray matter infarction. Serum Aβ40 levels at day 1 were predictive for NIHSS at day 7. Our results indicate that AIS can induce the generation of Aβ in the brain, which may in turn be involved in the pathogenesis of neurological deficits after stroke. Serum Aβ might be predictive for the short-term neurological deficits after AIS.