Reduced apolipoprotein epsilon 4 allele frequency in the oldest old Alzheimer's patients and cognitively normal individuals

The clinical epidemiology of Alzheimer's disease

Alzheimer's disease is a more common and malignant illness than was appreciated just 2 decades ago. In addition to being a major cause of mortality, it is costly and uniquely distressing for patients and their families. All indications are that the problem will grow as elderly populations expand. Fatalism regarding AD is premature, however. Much has been learned about this disease in only a few years, and it is hoped that this rate of discovery can be maintained or even accelerated in the future.

Apolipoprotein E ϵ4 allele, skin vessel reactivity and vascular risk factors in Alzheimer's disease

The apolipoprotein E (ApoE) epsilon4 allele is strongly associated with Alzheimer's disease (AD), and is, at the same time, a risk factor for cardiovascular disease. Recently, it has also been suggested that skin vessel reactivity is impaired in AD. The aim of this study was to assess the impact of the ApoE epsilon4 allele on the results of skin vessel reactivity tests and vascular risk factors such as cholesterol and blood pressure in AD. Fourteen non-smoking patients, who were in good general health and took no medicines, were tested. Three vasodilating substances with different modes of action, acetylcholine (ACh), isoprenaline and nitroprusside, were iontophoresed into the skin and the resultant vasodilation of the skin vessels was evaluated with the aid of a newly developed laser Doppler perfusion imager. The results of the tests did not differ significantly between the patient group with (n=10) and without (n=4) the ApoE epsilon4 allele, perhaps due to the small number of patients. The results of the skin vessel reactivity tests of the patient subgroups were also compared to those of healthy, non-smoking, non-medicating, age-matched controls. The findings of that comparison suggest, that the presence of the epsilon4 allele in AD might have an impact on skin vessel reactivity to the cholinergic agonist ACh.

Influence of apolipoprotein E genotype on cerebral amyloid angiopathy in the elderly

BACKGROUND AND PURPOSE

The inheritance of the epsilon 4 allele of the apolipoprotein E gene (APOE) is associated with increased risk of developing dementia of the Alzheimer type (DAT). We have investigated whether the APOE genotype influences the severity of cerebral amyloid angiopathy (CAA) in elderly individuals with or without DAT.

METHODS

From a consecutive autopsy series, we studied 88 patients (85.2 +/- 8.1 years) without degenerative disorders other than DAT. The percentages of amyloid-laden vessels in the occipital lobes were calculated and compared between APOE genotypes.

RESULTS

For epsilon 3/3 and epsilon 3/4 genotypes, there was a trend toward increased CAA in epsilon 3/4 individuals for non-DAT and conversely in epsilon 3/3 individuals for DAT patients, but these did not achieve significance.

CONCLUSIONS

The present study suggests that the epsilon 4 allele is not a strong risk factor for CAA in elderly people.

Prevalence of dementia and distribution of ApoE alleles in Japanese centenarians: an almost-complete survey in Yamanashi Prefecture, Japan

OBJECTIVE

To determine the prevalence and types of dementia in centenarians and to examine whether the ApoE epsilon 4 allele has significant impact on the development of Alzheimer's disease (AD) in the population.

DESIGN

Cross-sectional study and a 6-month prospective study.

SETTING

Yamanashi Prefecture, Japan.

PARTICIPANTS

Forty-seven centenarians participated in the study to determine the prevalence and types of dementia. Thirty-three of the 47 participated in the study of ApoE genotyping. As controls, 224 demented older adults participated in the genetic study. Their age at onset was < 90 years.

OUTCOMES

Prevalence of dementia based on DSM-III-R; types of dementia based on NINCDS-ADRDA and ICD-10; distribution on ApoE alleles in the centenarians and in the controls; and the 6-month mortality rate of the subjects.

MAIN RESULTS

Of 47 centenarians, 70.2% had dementia, and AD accounted for the majority (75.8%) of the dementia cases. The distribution of ApoE alleles in all the subjects and the AD subjects was epsilon 2: 4.6% vs. 0%; epsilon 3: 90.1% vs. 94.1%; epsilon 4: 4.6% vs. 5.9%. The frequency of the epsilon 4 allele in the AD patients showed a tendency to decrease with increasing age, ranging from 38% for those with an age at onset of < 60 years to 22% for those with an age at onset of ranging from 80 to 89 years. The 6-month mortality rate was 27% (9/33) for the demented centenarians, whereas none of the 14 nondemented centenarians died.

CONCLUSION

This almost-complete survey, conducted in a prefecture of Japan, revealed a high prevalence of dementia in centenarians. The ApoE epsilon 4 allele does not have an impact on the development of AD in centenarians.

Allele doses of apolipoprotein E type epsilon 4 in sporadic late-onset Alzheimer's disease

Apoliprotein E, type epsilon 4 allele (ApoE-epsilon 4) is associated with late-onset sporadic Alzheimer's disease (AD). We have found that the cumulative probability of remaining unaffected over time decreases for each dose of ApoE-epsilon 4 in sporadic, late-onset French AD. The effect of genotypes on age at onset of AD was analyzed using the product limit method, to compare unaffected groups during aging.

Apolipoprotein E, synaptic plasticity and Alzheimer's disease

Apolipoprotein E (apoE) has been studied extensively with regard to its role in plasma lipoprotein lipid transport. A role for apoE in the transport of membrane cholesterol and phospholipid in the central and peripheral nervous system has also been studied. Entorhinal cortex-lesioned rats have been used extensively to examine the molecular mechanisms associated with deafferentation and reinnervation in the CNS; studies of the role of apoE in this process using this animal model are described. In all human populations examined, three common apoE isoforms, apoE2, apoE3 and apoE4, result from multiple alleles epsilon 2, epsilon 3 and epsilon 4 at a single apoE genetic locus. These isoforms impart well-characterized functional differences in plasma lipoprotein transport, which are reviewed herein. Also discussed are less well-studied possible apoE-isoform specific differences in central nervous system function. These are currently of critical importance due to numerous recent studies showing an association of epsilon 4 with increased risk for Alzheimer's disease. Diverse hypotheses as to the molecular basis for this association, as well as the supporting experimental evidence, are reviewed.

A case-control study of apolipoprotein E genotypes in Alzheimer's disease associated with Down's syndrome. Dutch Study Group on Down's Syndrome and Ageing

The prevalence of clinical signs and neuropathological findings of Alzheimer's disease (AD) is high in Down's syndrome (DS). In the general population, the apolipoprotein E (ApoE) epsilon 4 isoform is an important risk for AD. We studied the allelic frequencies of ApoE in 26 DS cases fulfilling clinical diagnostic criteria for AD and in 26 DS controls matched for age, sex, and premorbid level of mental retardation. A meta-analysis of data available in the literature was used for comparison with allele frequencies in other AD and control populations. ApoE type 2, 3, or 4 allele frequencies were not significantly different in AD-DS cases and DS controls. The ApoE epsilon 4 frequency in DS cases with AD (0.14; CI, 0.06-0.26) was significantly lower than in any other AD population studied so far and it is within the range of nondemented controls from the general population. These findings suggest that ApoE epsilon 4 does not significantly affect the pathogenesis of AD in DS patients.

Epistatic effect of APP717 mutation and apolipoprotein E genotype in familial Alzheimer's disease

We found a new familial Alzheimer's disease kindred in which the disease cosegregates with the APP717Val-->Ile mutation and in which all of the three most common apolipoprotein E (ApoE) alleles are represented. We studied the relationship between ApoE genotype and the clinical expression of the disease and found that in this amyloid precursor protein-mutated family, ApoE genotype influences the age at onset of the disease. Three mutated subjects heterozygous for the epsilon 4 allele had the earliest age at onset in this family, subjects heterozygous for the epsilon 2 allele had the latest age at onset, and subjects homozygous for the epsilon 3 allele had an intermediate age at onset. In this large kindred we also found an amyloid precursor protein-mutated subject 2.4 standard deviations older than the mean age at onset without clinical signs and symptoms of the disease and carrying the epsilon 2/epsilon 3 genotype.

Cerebrospinal fluid levels of amyloid beta-protein in Alzheimer's disease: inverse correlation with severity of dementia and effect of apolipoprotein E genotype

Alzheimer's disease (AD) is characterized by formation in brain of neurofibrillary tangles and of amyloid deposits. The major protein component of the former is tau, while the latter are composed of amyloid beta-peptides (A beta), which are derived by proteolytic cleavage of the amyloid beta-protein precursor (APP). Both tau and various secretory APP derivatives including A beta and APPS are present in human cerebrospinal fluid (CSF). To investigate whether clinical signs of AD are paralleled by changes in CSF levels of these proteins, we correlated quantitative measures of dementia severity with CSF concentrations of A beta, of APPS, and of tau. We found that levels of A beta in CSF of AD patients were inversely correlated both to cognitive and to functional measures of dementia severity. In contrast, levels of APPS and of tau did not correlate with dementia severity. Apolipoprotein E (apoE) genotype did not influence CSF levels of A beta, APPS, or tau, which were similar among AD patients with Apo E epsilon 3/3, epsilon 3/4, and epsilon 4/4 alleles. These data indicate that CSF levels of A beta decrease with advancing severity of dementia in AD and suggest that they are independent of a patient's Apo E genotype.

Apolipoprotein E in animal models of CNS injury and in Alzheimer's disease

Recent evidence indicates that apolipoprotein E (ApoE) plays a central role in the hippocampal response to injury. The co-ordinated expression of ApoE and its receptor, the ApoE/ApoB [low density lipoprotein (LDL)] receptor, appears to regulate the transport of cholesterol and phospholipids during the early and intermediate phases of the reinnervation process. During dendritic remodeling and synaptogenesis, neurons progressively repress the synthesis of cholesterol in favor of cholesterol internalization through the ApoE/LDL receptor pathway. The discovery that the epsilon 4 allele is strongly linked to both sporadic and familial late-onset Alzheimer's disease (AD) raises the possibility that a dysfunction of the lipid-transport system associated with compensatory sprouting and synaptic remodeling could be central to the AD process. The role of ApoE in the CNS is particularly important in relation to the function of the cholinergic system, which relies to a certain extent on the integrity of phospholipid homeostasis in neurons. Recent evidence suggests that the epsilon 4 allele has a direct impact on cholinergic function in AD.