Apolipoprotein E (APOE) allele frequencies in late-onset sporadic Alzheimer's disease (AD), mixed dementia and vascular dementia: lack of association of epsilon 4 allele with AD in Italian octogenarian patients

Genome-wide DNA methylation profiling in nonagenarians suggests an effect of PM20D1 in late onset Alzheimer's disease

Background

The aim of this study is to identify differentially methylated regions (DMRs) in the genomes of a sample of cognitively healthy individuals and a sample of individuals with LOAD, all of them nonagenarians from Costa Rica.

Methods

In this study, we compared whole blood DNA methylation profiles of 32 individuals: 21 cognitively healthy and 11 with LOAD, using the Infinium MethylationEPIC BeadChip. First, we calculated the epigenetic age of the participants based on Horvath’s epigenetic clock. DMRcate and Bumphunter were used to identify DMRs. After in silico and knowledge-based filtering of the DMRs, we performed a methylation quantitative loci (mQTL) analysis (rs708727 and rs960603).

Results

On average, the epigenetic age was 73 years in both groups, which represents a difference of over 20 years between epigenetic and chronological age in both affected and unaffected individuals. Methylation analysis revealed 11 DMRs between groups, which contain six genes and two pseudogenes. These genes are involved in cell cycle regulation, embryogenesis, synthesis of ceramides, and migration of interneurons to the cerebral cortex. One of the six genes is PM20D1, for which altered expression has been reported in LOAD. After genotyping previously reported mQTL SNPs for the gene, we found that average methylation in the PM20D1 DMR differs between genotypes for rs708727, but not for rs960603.

Conclusions

This work supports the possible role of PM20D1 in protection against AD, by showing differential methylation in blood of affected and unaffected nonagenarians. Our results also support the influence of genetic factors on PM20D1 methylation levels.

Allelic Distribution of Genes for Apolipoprotein E and MTHFR in Patients with Alzheimer's Disease and Their Epistatic Interaction

Background:

Genetic risk factors play an important role in the pathogenesis of Alzheimer’s disease (AD). However, the gene-gene interaction (epistasis) between specific allelic variants is only partially understood.

Objective:

In our study, we examined the presence of the ɛ4 allele of apolipoprotein E (APOE) and the presence of C677T and A1298C (rs1801133 and rs1801131) polymorphisms in the methylenetetrahydrofolate reductase (MTHFR) gene in patients with AD and controls. We also evaluated the epistatic interaction between MTHFR and the APOE variants.

Methods:

A total of 564 patients with AD and 534 cognitively unimpaired age-matched controls were involved in the study.

Results:

The presence of the ɛ4 allele of APOE increases the risk of developing AD in a dose-dependent manner (OR 32.7: homozygotes, 15.6: homozygotes + heterozygotes, 14.3: heterozygotes). The combination of genotypes also increases the risk of developing AD in a dose-dependent manner: OR 18.3 (APOE 4/X and 4/4 + CT rs1801133), OR 19.4 (APOE 4/X and 4/4 + CT rs1801133 + AC rs1801131), OR 22.4 (APOE 4/X and 4/4 + TT rs1801133), and OR 21.2 (APOE 4/X and 4/4 + CC rs1801131). Homozygotes for variant alleles of MTHFR as well as patients with AD had significantly higher levels of homocysteine than homozygotes for standard alleles or controls.

Conclusion:

Homozygotes for APOE4 and carriers of APOE4 with TT genotype of rs1801133 were found to be at the highest risk of developing AD. These findings suggest that the epistatic interaction of specific gene variants can have a significant effect on the development of AD.

COVID-19 enters the expanding network of apolipoprotein E4-related pathologies

COVID-19 incidence and case fatality rates (CFR) differ among ethnicities, stimulating efforts to pinpoint genetic factors that could explain these phenomena. In this regard, the multiallelic apolipoprotein E (APOE) gene has recently been interrogated in the UK biobank cohort, demonstrating associations of the APOE ε4/ε4 genotype with COVID-19 severity and mortality. The frequency of the ε4 allele and thus the distribution of APOE ε4/ε4 genotype may differ among populations. We have assessed APOE genotypes in 1638 Greek individuals, based on haplotypes derived from SNP rs7412 and rs429358 and found reduced frequency of ε4/ε4 compared to the British cohort. Herein we discuss this finding in relation to CFR and hypothesize on the potential mechanisms linking APOE ε4/ε4 to severe COVID-19. We postulate that the metabolic deregulation ensued by APOE4, manifested by elevated cholesterol and oxidized lipoprotein levels, may be central to heightened pneumocyte susceptibility to infection and to exaggerated lung inflammation associated with the ε4/ε4 genotype. We also discuss putative dietary and pharmacological approaches for the prevention and management of COVID-19 in APOE ε4/ε4 individuals.

Inflammation: Bridging Age, Menopause and APOEε4 Genotype to Alzheimer's Disease

Neuro-inflammatory processes that contribute to development of Alzheimer’s are evident early in the latent prodromal phase and worsen during the course of the disease. Despite substantial mechanistic and clinical evidence of inflammation, therapeutic approaches targeting inflammation have failed to alter the course of the disease. Disparate results from epidemiological and clinical trials targeting inflammation, highlight the complexity of the inflammatory process. Herein we review the dynamics of the inflammatory process across aging, midlife endocrine transitions, and the APOEε4 genotype and their contribution to progression of Alzheimer’s disease (AD). We discuss the chronic inflammatory processes that are activated during midlife chronological and endocrine aging, which ultimately limit the clearance capacity of microglia and lead to immune senescence. Aging, menopause, and APOEε4 combine the three hits of a compromised bioenergetic system of menopause with the chronic low grade innate inflammation of aging with the APOEε4 dyslipidemia and adaptive immune response. The inflammatory immune response is the unifying factor that bridges across each of the risk factors for AD. Immune system regulators that are specific to stage of disease and inflammatory phenotype would provide a therapeutic strategy to disconnect the bridge that drives disease. Outcomes of this analysis provide plausible mechanisms underlying failed clinical trials of anti-inflammatory agents in Alzheimer’s patients. Further, they highlight the need for stratifying AD clinical trial cohorts based on inflammatory phenotype. Combination therapies that include targeted use of anti-inflammatory agent’s specific to the immune phenotype are considered.

Evaluation of Amyloid Protective Factors and Alzheimer Disease Neurodegeneration Protective Factors in Elderly Individuals

Importance

While amyloid and neurodegeneration are viewed together as Alzheimer disease pathophysiology (ADP), the factors that influence amyloid and AD-pattern neurodegeneration may be considerably different. Protection from these ADP factors may be important for aging without significant ADP.

Objective

To identify the combined and independent protective factors for amyloid and AD-pattern neurodegeneration in a population-based sample and to test the hypothesis that "exceptional agers" with advanced ages do not have significant ADP because they have protective factors for amyloid and neurodegeneration.

Design, Setting, and Participants

This cohort study conducted a prospective analysis of 942 elderly individuals (70-≥90 years) with magnetic resonance imaging and Pittsburgh compound B-positron emission tomography scans enrolled in the Mayo Clinic Study of Aging, a longitudinal population-based study of cognitive aging in Olmsted County, Minnesota. We operationalized "exceptional aging" without ADP by considering individuals 85 years or older to be without significant evidence of ADP.

Main Outcomes and Measures

We evaluated predictors including demographics, APOE, intellectual enrichment, midlife risk factors (physical inactivity, obesity, smoking, diabetes, hypertension, and dyslipidemia), and the total number of late-life cardiac and metabolic conditions. We used multivariate linear regression models to identify the combined and independent protective factors for amyloid and AD-pattern neurodegeneration. Using a subsample of the cohort 85 years of age or older, we computed Cohen d-based effect size estimations to compare the quantitative strength of each predictor variable in their contribution with exceptional aging without ADP.

Results

The study participants included 423 (45%) women and the average age of participants was 79.7 (5.9) years. Apart from demographics and the APOE genotype, only midlife dyslipidemia was associated with amyloid deposition. Obesity, smoking, diabetes, hypertension, and cardiac and metabolic conditions, but not intellectual enrichment, were associated with greater AD-pattern neurodegeneration. In the 85 years or older cohort, the Cohen d results showed small to moderate effects (effect sizes > 0.2) of several variables except job score and midlife hypertension in predicting exceptional aging without ADP.

Conclusions and Relevance

The protective factors that influence amyloid and AD-pattern neurodegeneration are different. "Exceptional aging" without ADP may be possible with a greater number of protective factors across the lifespan but warrants further investigation.

Apolipoprotein ɛ4 is Associated with Dementia and Cognitive Impairment Predominantly Due to Alzheimer's Disease and Not with Vascular Cognitive Impairment: A Singapore-Based Cohort

BACKGROUND AND OBJECTIVE

While the association for apolipoprotein ɛ4 allele (APOE4) with Alzheimer's disease (AD) has been consistently confirmed, the association with vascular cognitive impairment (VCI) is unclear. We therefore explored the relationship of APOE with both AD and cerebrovascular disease (CeVD) by examining the prevalence of APOE4 in AD, AD with CeVD and vascular dementia (VaD), as well as in cognitive impairment no dementia (CIND) with and without CeVD.

METHODS

We performed a case-control study with subjects recruited from memory clinics and the community. All subjects underwent standardized brain neuroimaging, clinical and neuropsychological assessments, following which they were classified using research criteria.

RESULTS

A total of 411 subjects; 92 controls with no cognitive impairment (NCI), 77 CIND without CeVD, 87 CIND with CeVD, 55 AD without CeVD, 68 AD with CeVD, and 32 VaD patients were recruited. Compared to NCI (16.3%), the prevalence of APOE4 carriers was significantly higher only in CIND (37.7%) and AD in the absence of CeVD (45.5%), but not in the three subgroups of VCI, namely CIND with CeVD (20.7%), AD with CeVD (27.9%) and VaD (25.0%). Logistic regression analyses also showed that APOE4 carriers were more likely to have CIND without CeVD (Odds Ratio [OR]: 3.34; 95% Confidence Interval [CI]: 1.59-7.03) and AD without CeVD (OR: 7.21; 95% CI: 2.74-18.98), but no such association was observed in the VCI subgroups.

CONCLUSION

APOE4 is significantly associated with dementia and CIND due to AD pathology, but not with VCI.

Genetics of Vascular Dementia: Systematic Review and Meta-Analysis

BACKGROUND

Vascular dementia (VaD) is the second most common type of dementia. So far, little is known about the contribution of genetic polymorphisms to the risk of VaD. Many candidate genetic polymorphisms have been examined in a large number of studies. However, due to the conflicting results, the genetics of VaD is still behind the shadow.

OBJECTIVE

We conducted a comprehensive meta-analysis on associations between genetic polymorphisms of any gene and VaD to investigate the genetics of VaD.

METHOD

We sought the published studies of associations between any genetic polymorphism and VaD and critically appraised them. We assessed the effects of genetic models by calculating pooled odds ratios (ORs), investigating the origin of heterogeneity by subgroup analysis, and testing the robustness by random effect model and sensitivity analysis.

RESULTS

69 studies with 4,462 cases and 11,583 controls were included. We identified APOE ɛ2/ɛ3/ɛ4 and additional four genetic polymorphisms including MTHFR C677T, PON1 L55M, TGF-β1 +29C/T, and TNF-α -850C/T associated with VaD. Tested by random effect model and sensitivity analysis, the pooled results show nice robustness.

CONCLUSIONS

Our comprehensive meta-analysis highlighted the genetic contribution to sporadic VaD. Because of the small amount of data on associations between genetic polymorphisms, except for APOE, and VaD, more studies are needed to test the existing genetic polymorphisms and detect other related genetic variants.

A genome-wide screening and SNPs-to-genes approach to identify novel genetic risk factors associated with frontotemporal dementia

Frontotemporal dementia (FTD) is the second most prevalent form of early onset dementia after Alzheimer's disease (AD). We performed a case-control association study in an Italian FTD cohort (n = 530) followed by the novel single nucleotide polymorphisms (SNPs)-to-genes approach and functional annotation analysis. We identified 2 novel potential loci for FTD. Suggestive SNPs reached p-values ∼10⁻⁷ and odds ratio > 2.5 (2p16.3) and 1.5 (17q25.3). Suggestive alleles at 17q25.3 identified a disease-associated haplotype causing decreased expression of –cis genes such as RFNG and AATK involved in neuronal genesis and differentiation and axon outgrowth, respectively. We replicated this locus through the SNPs-to-genes approach. Our functional annotation analysis indicated significant enrichment for functions of the brain (neuronal genesis, differentiation, and maturation), the synapse (neurotransmission and synapse plasticity), and elements of the immune system, the latter supporting our recent international FTD–genome-wide association study. This is the largest genome-wide study in Italian FTD to date. Although our results are not conclusive, we set the basis for future replication studies and identification of susceptible molecular mechanisms involved in FTD pathogenesis.

Apolipoprotein E allelotype is associated with neuropathological findings in Alzheimer's disease

In a consecutive hospital-based autopsy series, we examined the relationship between apolipoprotein E (apoE) and Alzheimer's disease (AD) and investigated the clinicopathological relationship in AD. The study population included 99 patients (mean age 81 years) with AD-related neuropathological findings at death, of whom 83 were diagnosed with AD according to the Consortium to Establish a Registry for Alzheimer's Disease (CERAD) classification, and a control group of patients without neurodegenerative disease (n = 1429). The patients were apoE genotyped and the density of β-amyloid senile plaques, neuritic plaques and neurofibrillary tangles was estimated in the cortex and hippocampus. The utility of immunohistochemical staining using an antibody directed against apoE4 in paraffin-embedded tissue was also evaluated. Among patients with "definite AD" according to CERAD, 65 % were ε4 carriers, compared to 32 % among controls (p < 0.001). The risk of ε4 carriers to develop AD was higher (odds ratio = 4.65, p = 0.001) than for non-ε4 carriers. The amount of β-amyloid deposition and neurofibrillary pathology differed significantly (p < 0.01) between the genotypes, with increasing densities from ε2 carriers to homozygous ε4 carriers. The effect of ε4 on the presence of clinical symptoms was attenuated and non-significant after adjusting for AD-related neuropathological findings. There was an association between these findings and the presence of clinical symptoms of AD, with neurofibrillary tangles separating patients with and without symptoms of AD markedly better than β-amyloid. In addition, we found a strong relationship between genotype and immunohistochemical apoE4-staining intensity. In conclusion, this Scandinavian autopsy study shows that the apoE polymorphism is associated with the probability of AD and influences the deposition of β-amyloid and neurofibrillary pathology. Our findings suggest that the association between apoE and clinical manifestations of AD is mediated mainly through the neuropathological features of AD. Further, we found a relationship between AD-related findings and clinical symptoms of AD with neurofibrillary tangles associating most strongly with clinical symptoms. Finally, immunohistochemical staining in brain specimens is useful for determining ε4- or non-ε4-carrier status.

Ceruloplasmin/Transferrin ratio changes in Alzheimer's disease

The link between iron and Alzheimer's disease (AD) has been mainly investigated with a focus on the local accumulation of this metal in specific areas of the brain that are critical for AD. In the present study, we have instead looked at systemic variations of markers of iron metabolism. We measured serum levels of iron, ceruloplasmin, and transferrin and calculated the transferrin saturation and the ceruloplasmin to transferrin ratio (Cp/Tf). Cp/Tf and transferrin saturation increased in AD patients. Cp/Tf ratios also correlated positively with peroxide levels and negatively with serum iron concentrations. Elevated values of ceruloplasmin, peroxides, and Cp/Tf inversely correlated with MMSE scores. Isolated medial temporal lobe atrophy positively correlated with Cp/Tf and negatively with serum iron. All these findings indicate that the local iron accumulation found in brain areas critical for AD should be viewed in the frame of iron systemic alterations.

BuChE K variant is decreased in Alzheimer's disease not in fronto-temporal dementia

Alzheimer's disease (AD) is characterized by a significant reduction in AcetylCholinesterase and an increase in ButyrylCholinesterase (BuChE) activity. The existence of polymorphic regions on the BuChE gene has been previously described; the most frequently found polymorphism is the so-called K variant, which leads to a 30% decreased enzymatic activity. Different studies reported a positive association between K variant and AD, strongest among late-onset AD and Apolipoprotein E (APOE) e4 carriers. We analyzed APOE and BuChE polymorphisms in 167 AD and 59 fronto-temporal dementia (FTD) patients compared with 129 healthy controls (HC). We reported a significantly lower frequency of the BuChE K variant in AD compared with HC and FTD and a significant increased frequency of the K variant in FTD. These results are in agreement with the known increase of the BuChE activity in AD and support the evidence of different molecular pathways involved in the pathogenesis of AD and FTD.

A comparative study to screen dementia and APOE genotypes in an ageing East African population

Previous studies have established cross-cultural methods to screen for ageing- related dementia and susceptibility genes, in particular Alzheimer's disease (AD) among the Canadian Cree, African Americans and Yoruba in Nigeria. We determined whether the Community Screening Interview for Dementia (CSID), translated into Kikuyu, a major language of Kenya, could be used to evaluate dementia of the Alzheimer type. Using two sets of coefficients of cognitive and informant scores, two discriminant function (DF) scores were calculated for each of 100 elderly (>65 years) Nyeri Kenyans. When the cut-off points were selected for 100% sensitivities, the specificities of the DF scores were remarkably similar (93.75%) in the Kenyan sample. We propose the adapted CSID can be utilised to detect dementia among East Africans. We also show that apolipoprotein E epsilon 4 allele frequencies were high (approximately 30%) and not different between normal subjects and those with probable AD. There was no evidence to suggest years of education or vascular factors were associated with dementia status.

Apolipoprotein E genotype is related to plasma levels of C-reactive protein and lipids and to longevity in nonagenarians

OBJECTIVE

Apolipoprotein E (APOE) genotype is a regulator of hepatic lipoprotein metabolisms and has been linked with longevity. The relationship between APOE genotype and plasma C-reactive protein (CRP), which is produced by the liver during inflammation, has not been studied in nonagenarians. The aim of the present study was to establish whether APOE genotype is related to plasma concentrations of CRP and lipids, or longevity among nonagenarians.

DESIGN AND PATIENTS

This cross-sectional study consisted of 291 Finnish nonagenarians and three previously described and genotyped control populations from the same area (i.e. newborns, 40-year-olds, and 70-year-olds).

RESULTS

In all nonagenarians and especially in women (P= 0.038), CRP level decreased linearly in the genotype order of epsilon2/2, epsilon2/3, epsilon3/3, epsilon2/4, epsilon3/4 and epsilon4/4. Total (P= 0.009) and low-density lipoprotein (LDL) cholesterol (P = 0.076) levels, in turn, were increased in the epsilon4 allele carriers. In newborns, the epsilon4 frequency was 0.192, in 40-year-olds 0.181, in 70-year-olds 0.179 and in nonagenarians 0.095 (P < 0.0001). The decrease in the epsilon4 allele frequency in the elderly was more clearly seen in women than in men.

CONCLUSIONS

APOEepsilon4 allele seems to be associated with decreased inflammatory response as measured by CRP among nonagenarians. This finding may partly explain why some epsilon4 allele carriers can reach very old age despite increased risk of hypercholesterolaemia.

Allele ɛ4 of APOE is a stronger predictor of Alzheimer risk in Sicily than in continental South Italy

The genotype of apolipoprotein E was examined in 173 sporadic Alzheimer's disease (AD) patients, 132 with late onset (LOAD) and 41 with early onset (EOAD), and in 174 healthy matched controls from Sicily. Despite a low frequency of the epsilon 4 allele (6.3%, 95% CI: 4.2--9.4) in controls, epsilon 4 allele was a stronger predictor of AD risk (odds ratio: 5.8, 95% CI: 3.5--9.4; p<0.0001) than in most of the studies performed in other regions of Italy, and it has no influence on age at onset. epsilon 4/epsilon 4 and epsilon 4/epsilon 3 genotypes were similar predictors of AD risk. Conversely, a decreased risk was found in epsilon 3 allele carriers (odds ratio: 0.3, 95% CI: 0.2--0.4; p<0.0001), which remained significant when considering EOAD cases only (odds ratio: 0.2, 95% CI: 0.1--0.4, p<0.0001). In conclusion, differences in association strength of epsilon 4 allele with AD between Sicily and other regions of Italy suggest an influence of complex gene-gene and gene-environment interactions.

Plasma α1-antichymotrypsin in Alzheimer’s disease; relationships with APOE genotypes

Inflammatory processes are thought to be important contributors to the pathogenesis of Alzheimer's disease (AD). alpha1-antichymotrypsin (ACT) is a proteinase inhibitor characteristic of acute-phase inflammation and has been identified in amyloid plaques. We analyzed the plasma ACT levels in a sample of subjects with late-onset AD and correspondent controls. Plasma ACT was higher in AD patients (62.8 +/- 20.2 mg/dl) than in controls (58.8 +/- 18.1 mg/dl), but not significantly (P = 0.13). In the AD patients regression analysis showed a positive linear relationship between ACT levels and duration of the disease (P = 0.037). Increased ACT concentrations (64.6 +/- 21.2 mg/dl) were also found in patients with greater cognitive impairment (MMSE scores < 20), but since this factor depends on the duration of the disease as well, our present data seem to indicate a complex relationship involving elevated ACT levels, disease duration and cognitive impairment. Plasma ACT was found to differ significantly according to APOE genotypes (P = 0.017), the highest levels being associated to E3-E3 homozygotes (66.1 +/- 17.8 mg/dl) and the lowest to E4-E3 subjects (53.1 +/- 18.2 mg/dl). In patients not carrying APOE*4 allele the ACT levels were higher than in controls (P = 0.014), and the relationship between ACT and disease duration was stronger than that observed in the total AD sample (P = 0.003), but it was absent in those carrying APOE*4 (P = 0.67). Taken together our results seem to suggest that inflammation is a relevant factor in AD pathogenesis for subjects with E3-E3 and E3-E2 genotypes but less important for APOE*4 carrying subjects.

Apolipoprotein E in Southern Italy: protective effect of epsilon 2 allele in early- and late-onset sporadic Alzheimer's disease

Apolipoprotein E (apoE) polymorphism was evaluated in 81 sporadic late onset Alzheimer's disease (LOAD) patients, 28 sporadic early-onset Alzheimer's disease (EOAD) and 92 sex- and age-matched healthy controls from Apulia, Southern Italy. ApoE genotypes were determined by the polymerase chain reaction-restriction fragment length polymorphism method. The frequency of apoE epsilon 4 allele was significantly higher in EOAD patients than in the control group, but not in LOAD patients. Furthermore, EOAD patients carrying epsilon 4 allele had lower age at onset of AD symptoms (about 4. 5 years). In the whole sample, epsilon 4 was associated to AD by an odds ratio of 2.14, while it increased up to 6.55 in < 65 years old subjects. Finally, in both < 65 and > or = 65 subgroups of subjects, epsilon 2 played a protective role against the development of AD. It is concluded that the geographic decreasing trend of epsilon 4 allele and the age at onset may influence the association of apoE polymorphism with sporadic AD in a Southern Italian sample.

Butyrylcholinesterase K variant is genetically associated with late onset Alzheimer's disease in Northern Ireland

Alzheimer's disease (AD) is a progressive neurodegenerative disorder that has been associated, sometimes controversially, with polymorphisms in a number of genes. Recently the butyrylcholinesterase K variant (BCHE K) allele has been shown to act in synergy with the apolipoprotein E epsilon4 (APOE epsilon4) allele to promote risk for AD. Most subsequent replicative studies have been unable to confirm these findings. We have conducted a case-control association study using a clinically well defined group of late onset AD patients (n=175) and age and sex matched control subjects (n=187) from the relatively genetically homogeneous Northern Ireland population to test this association. The BCHE genotypes of patients were found to be significantly different from controls (chi(2)=23.68, df=2, p<<0.001). The frequency of the K variant allele was also found to differ significantly in cases compared to controls (chi(2)=16.39, df=1, p<<0.001) leading to an increased risk of AD in subjects with this allele (OR=3.50, 95% CI 2. 20-6.07). This risk increased in subjects 75 years and older (OR=5. 50, 95% CI 2.56-11.87). At the same time the APOE epsilon4 associated risk was found to decrease from 6.70 (95% CI 2.40-19.04) in 65-74 year olds to 3.05 (95% CI 1.34-6.95) in those subjects 75 years and older. However, we detected no evidence of synergy between BCHE K and APOE epsilon4. The results from this study suggest that possession of the BCHE K allele constitutes a significant risk for AD in the Northern Ireland population and, furthermore, this risk increases with increasing age.

Identifying families with likely genetic protective factors against Alzheimer disease

Elderly individuals who lived beyond the age of 90 years without dementia were hypothesized to have increased concentrations of genetic protective factors against Alzheimer disease (AD), conferring a reduced liability for this disease relative to less-aged nondemented elderly. However, testing this hypothesis is complicated by having to distinguish such a group from those who may lack genetic risk factors for AD, have had protective environmental exposures, or have escaped dementia for other reasons. Probands carrying genetic protective factors, however, should have relatives with lower illness rates not only for earlier-onset disease, when genetic risk factors are a strong contributing factor to the incidence of AD, but also for later-onset disease, when the role of these factors appears to be markedly diminished. AD dementia was assessed through family informants in 6,660 first-degree relatives of 1,049 nondemented probands aged 60-102 years. The probands were grouped by age (60-74, 75-89, and 90-102 years), and the cumulative survival from AD and 10-year-age-interval hazard rates of AD were calculated in their first-degree relatives. Cumulative survival from AD was significantly greater in the relatives of the oldest proband group (aged 90-102 years) than it was in the two younger groups. In addition, the reduction in the rate of illness for this group was relatively constant across the entire late life span. The results suggest that genetic factors conferring a lifelong reduced liability of AD may be more highly concentrated among nondemented probands aged >/=90 years and their relatives. Efforts to identify protective allele-bearing genes that are associated with very late-onset AD should target the families of nonagenarians and centenarians.

Increased apolipoprotein E4 allele frequency is associated with vascular dementia in the Hungarian population

INTRODUCTION

The regulatory role of apolipoprotein E in lipid transport and metabolism was utilized to investigate the allelic association between the apolipoprotein E4 (apoE4) allele and vascular dementia (VD) in a selected sample of Hungarian patients with multiple deep subcortical infarcts and leukoaraiosis.

MATERIAL AND METHODS

Thirty-four Caucasian VD cases and 79 healthy control probands were involved in this study according to the criteria of ICD-10 and NINDS-AIREN International Workshop Diagnostic Criteria. The genomic DNA was isolated from whole blood and the apoE alleles were determined by polymerase chain reaction.

RESULTS

The E2, E3 and E4 allele frequencies in the VD group were 5%, 76%, and 19%, respectively; and significant (P<0.03) differences were found in comparison with the data on the healthy controls (E2, 6%; E3, 87%; E4, 8%). The apoE4 allele frequency was intermediate between HC and Alzheimer's dementia group (28%).

CONCLUSION

These results indicate that the apoE4 allele could be a risk factor not only for certain primary degenerative, but also for vascular dementias.

The relationship between apolipoprotein E, dementia, and vascular illness

The purpose of this study was to concurrently assess the relationship of Apolipoprotein E (APOE) with both dementias and vascular illnesses in the very old. Nine hundred and fifty nine subjects (mean age 85 years) in a long-term care facility were genotyped and cognitively tested with the Mini Mental State Exam. All subjects were studied for the relationship of APOE with atherosclerotic heart disease, hypertension, or stroke without concomitant dementia. Four hundred fifty individuals met criteria for inclusion into one of the following groups: Alzheimer's disease (n = 318), vascular dementia (n = 49), or not demented controls (n = 83) and were investigated for the relationship between APOE and these diagnostic categories. APOE epsilon4 was not associated with atherosclerotic heart disease, hypertension, or stroke without concomitant dementia. The APOE epsilon3 allele was more common in men with atherosclerotic heart disease. In contrast, the APOE epsilon4 allele was more common in patients with Alzheimer's disease (22%) and vascular dementia (26%) than in not demented controls (7%). APOE epsilon4 is associated with dementias in the very old, whereas its relationship with either peripheral or central nervous system vascular disease without dementia is not as robust.

ACE, MTHFR, factor V Leiden, and APOE polymorphisms in patients with vascular and Alzheimer's dementia

BACKGROUND AND PURPOSE

There is a growing interest in the use of genetic markers in the differential diagnosis of dementia. In the current study we examined the usefulness of genetic risk factors for vascular disease as markers for vascular dementia (VD).

METHODS

The groups included 41 patients with VD, 49 patients with dementia of the Alzheimer's type, and 40 age-matched control subjects without dementia. These patients were genotyped for vascular disease-associated polymorphisms in the genes coding for methylenetetrahydrofolate reductase (MTHFR), angiotensin-converting enzyme (ACE), factor V Leiden (FVL), and a common genetic risk factor for AD, apolipoprotein E epsilon4 (APOE epsilon4).

RESULTS

There was no significant association between ACE, MTHFR, and FVL genotypes with VD whether compared with subjects with AD or with control subjects. There was a higher frequency of APOE epsilon4 alleles in patients with AD (30%, P=0.016) and VD (26%, P=0.07) compared with control subjects (15%).

CONCLUSIONS

VD is not associated with the genetic risk factors for vascular disease examined in this study, indicating that the pathogenesis of VD may differ from other vascular diseases.