Epsilon 4 allele of apolipoprotein E increases risk of Alzheimer's disease in a Chinese population

Age and sex differences in the association between APOE genotype and Alzheimer's disease in a Taiwan Chinese population

Introduction

The Apolipoprotein E (APOE) epsilon (ε) 4 allele is a well-established risk factor for late-onset Alzheimer's disease (AD). Reports on white ancestry populations have showed that age, sex, and ethnicity have different effects on the association between APOE genotype and AD. However, studies on Asian populations such as Taiwan Chinese populations are limited. This study aimed to evaluate the association between APOE genotype and AD in a Taiwan Chinese population, and to explore if the association varies by age and sex.

Methods

We conducted a case-control study in 725 patients with AD and 1,067 age- and sex- matched controls without dementia from a Taiwan Chinese population. Logistic regression models were used to test the association between AD and APOE genotypes. Secondary analyses considered age (<75 or ≥75 years old), and sex stratified models.

Results

The risk of AD was significantly increased for people with at least one copy of APOE ε4 (OR = 2.52, 95% CI = 2.01-3.17, p < 0.001) and in a dose-dependent manner. Our results did not show an statistically significance different in AD risk when women and men carrying APOEε4 were compared. Despite not reaching statistical significance, the risk of APOE ε4 for AD was higher among younger participants (OR = 3.21, 95% CI = 2.26-4.56, p < 0.001) compared to older ones (OR = 2.13, 95% CI = 1.53-2.97, p < 0.001). When considering both sex and age, the risk of AD was higher among older men carrying APOE ε4 (OR = 2.64, 95% CI = 1.51-4.60 in men; OR = 1.90, 95% CI = 1.26-2.86 in women), while women carrying APOE ε4 appeared to have an increased risk at a younger age (OR = 3.29, 95% CI = 2.20-4.93 in women; OR = 2.91, 95% CI = 1.40-6.05 in men).

Discussion

The APOE ε4 allele represents a major risk factor for AD in the Taiwanese population. The effect of APOE ε4 allele on AD risk appeared to be stronger among men aged 75 years or more and among younger women.

The multi-domain exercise intervention for memory and brain function in late middle-aged and older adults at risk for Alzheimer's disease: A protocol for Western-Eastern Brain Fitness Integration Training trial

Background

Aging is associated with cognitive decline, increased risk for dementia, and deterioration of brain function. Modifiable lifestyle factors (e.g., exercise, meditation, and social interaction) have been proposed to benefit memory and brain function. However, previous studies have focused on a single exercise modality or a single lifestyle factor. Consequently, the effect of a more comprehensive exercise program that combines multiple exercise modalities and lifestyle factors, as well as examines potential mediators and moderators, on cognitive function and brain health in late middle-aged and older adults remains understudied. This study's primary aim is to examine the effect of a multi-domain exercise intervention on memory and brain function in cognitively healthy late middle-aged and older adults. In addition, we will examine whether apolipoprotein E (ApoE) genotypes, physical fitness (i.e., cardiovascular fitness, body composition, muscular fitness, flexibility, balance, and power), and brain-derived neurotrophic factor (BDNF) moderate and mediate the exercise intervention effects on memory and brain function.

Methods

The Western-Eastern Brain Fitness Integration Training (WE-BFit) is a single-blinded, double-arm, 6-month randomized controlled trial. One hundred cognitively healthy adults, aged 45-70 years, with different risks for Alzheimer's disease (i.e., ApoE genotype) will be recruited and randomized into either a multi-domain exercise group or an online educational course control group. The exercise intervention consists of one 90-min on-site and several online sessions up to 60 min per week for 6 months. Working memory, episodic memory, physical fitness, and BDNF will be assessed before and after the 6-month intervention. The effects of the WE-BFit on memory and brain function will be described and analyzed. We will further examine how ApoE genotype and changes in physical fitness and BDNF affect the effects of the intervention.

Discussion

WE-BFit is designed to improve memory and brain function using a multi-domain exercise intervention. The results will provide insight into the implementation of an exercise intervention with multiple domains to preserve memory and brain function in adults with genetic risk levels for Alzheimer's disease.

Clinical trial registration

ClinicalTrials.gov, identifier: NCT05068271.

Apolipoprotein E Gene Revisited: Contribution of Rare Variants to Alzheimer's Disease Susceptibility in Southern Chinese

BACKGROUND

APOE ε4 is the best-known risk factor for late-onset alzheimer's disease (AD). Population studies have demonstrated a relatively low prevalence of APOE ε4 among Chinese population, implying additional risk factors that are Chinese-specific may exist. Apart from - alleles, genetic variation profile along the full-length APOE has rarely been investigated.

OBJECTIVE

In this study, we filled this gap by comprehensively determining all genetic variations in APOE and investigated their potential associations with late-onset AD and mild cognitive impairment (MCI) in southern Chinese.

METHODS

Two hundred and fifty-seven southern Chinese participants were recruited, of whom 69 were AD patients, 83 had MCI, and 105 were normal controls. Full-length APOE from promoter to 3'UTR regions were sequenced. Genetic variants were identified and compared among the three groups.

RESULTS

While APOE ε4 was more significantly found in AD patients, the prevalence of APOE ε4 in southern Chinese AD patients was the lowest when compared to other areas of China and nearby regions, as well as other countries worldwide. We further identified 13 rare non-singleton variants in APOE. Significantly more AD patients carried any of the rare non-singleton variants than MCI and normal subjects. Such difference was observed in the non-carriers of ε4-allele only. Among the identified rare variants, the potential functional impact was predicted for rs532314089, rs553874843, rs533904656 and rs370594287.

CONCLUSION

Our study suggests an ethnic difference in genetic risk composition of AD in southern Chinese. Rare variants on APOE are a potential candidate for AD risk stratification biomarker in addition to APOE-ε4.

The association between the ApoE polymorphisms and the MRI-defined intracranial lesions in a cohort of southern China population

Background

The apolipoprotein E (APOE) ε4 allele is considered as a risk factor for Alzheimer's disease (AD). However, the association of APOE allele with MRI evidence of intracranial lesions has not been well understood.

Methods

Quantitative real‐time PCR was performed to detect the APOE genotype; MRI was examined for intracranial lesions. Their association was evaluated in a cohort of 226 AD patients and 2607 healthy individuals in southern China.

Results

The frequencies of ε2, ε3, and ε4 alleles were 8.0%, 82.9%, and 9.1% in the whole study population. The frequency of APOE‐ε4 allele was significantly higher in the AD subjects than that in the control group (14.4% vs 8.6%, P < 0.001). We found that brain atrophy occurred at a rate of 12.3% in ε4 allele group vs 8.5% in non‐ε4 genotype group, with a significance of P = 0.008. Severe brain atrophy occurred at a rate of 1.0% in ε4 allele group vs 0.2% in non‐ε4 genotype group (P = 0.011). The individuals carrying APOE ε4/ε4 had an odds ratio (OR) of 7.64 (P < 0.01) for developing AD, while the APOE ε3/ε4 gene carriers had an OR of 1.47 (P = 0.031) and the OR in APOE ε2/ε3 carriers is 0.81 (P = 0.372). Interestingly, we found that the risk of ε4/ε4 allele carrier developing AD was significantly higher in male (P < 0.001) than female (P = 0.478).

Conclusion

Compared to ε2 and ε3 alleles, the presence of APOE‐ε4 allele might increase the risk for AD in a dose‐dependent manner in southern China. Moreover, the presence of APOE‐ε4 allele results in a higher incidence of brain atrophy.

Apolipoprotein ε4 is associated with lower brain volume in cognitively normal Chinese but not white older adults

Studying ethnically diverse groups is important for furthering our understanding of biological mechanisms of disease that may vary across human populations. The ε4 allele of apolipoprotein E (APOE ε4) is a well-established risk factor for Alzheimer's disease (AD), and may confer anatomic and functional effects years before clinical signs of cognitive decline are observed. The allele frequency of APOE ε4 varies both across and within populations, and the size of the effect it confers for dementia risk may be affected by other factors. Our objective was to investigate the role APOE ε4 plays in moderating brain volume in cognitively normal Chinese older adults, compared to older white Americans. We hypothesized that carrying APOE ε4 would be associated with reduced brain volume and that the magnitude of this effect would be different between ethnic groups. We performed whole brain analysis of structural MRIs from Chinese living in America (n = 41) and Shanghai (n = 30) and compared them to white Americans (n = 71). We found a significant interaction effect of carrying APOE ε4 and being Chinese. The APOE ε4xChinese interaction was associated with lower volume in bilateral cuneus and left middle frontal gyrus (Puncorrected<0.001), with suggestive findings in right entorhinal cortex and left hippocampus (Puncorrected<0.01), all regions that are associated with neurodegeneration in AD. After correction for multiple testing, the left cuneus remained significantly associated with the interaction effect (PFWE = 0.05). Our study suggests there is a differential effect of APOE ε4 on brain volume in Chinese versus white cognitively normal elderly adults. This represents a novel finding that, if verified in larger studies, has implications for how biological, environmental and/or lifestyle factors may modify APOE ε4 effects on the brain in diverse populations.

APOE and APOC1 gene polymorphisms are associated with cognitive impairment progression in Chinese patients with late-onset Alzheimer's disease

Current evidence shows that apolipoprotein E (APOE), apolipoprotein CI (APOC1) and low density lipoprotein receptor-related protein (LRP) variations are related to late-onset Alzheimer's disease. However, it remains unclear if genetic polymorphisms in these genes are associated with cognitive decline in late-onset Alzheimer's disease patients. We performed a 30-month longitudinal cohort study to investigate the relationship between Alzheimer's disease and APOE, APOC1, and LRP. In this study, 78 Chinese Han patients with late-onset Alzheimer's disease were recruited form Guangxi Zhuang Autonomous Region in China. APOE, APOC1, and LRP genotyping was performed using polymerase chain reaction-restriction fragment length polymorphisms. The Mini-Mental State Examination and Clinical Dementia Rating Scale were used to assess patients’ cognitive function. After a 30-month follow-up period, we found a significant reduction in Mini-Mental State Examination total score, a higher proportion of patients fulfilling cognitive impairment progression criteria, and a higher proportion of APOC1 H2 carriers in APOE ε4 carriers compared with non-carriers. In addition, the APOE ε4 allele frequency was significantly higher in the cognitive impairment progression group compared with the non-cognitive impairment progression group. In conclusion, APOE ε4 plays an important role in augmenting cognitive decline, and APOC1 H2 may act synergistically with APOE ε4 in increasing the risk of cognitive decline in Chinese patients with late-onset Alzheimer's disease.

The APOE ɛ4 allele affects complexity and functional connectivity of resting brain activity in healthy adults

The apolipoprotein E (APOE) gene is associated with structural and functional brain changes. We have used multiscale entropy (MSE) analysis to detect changes in the complexity of resting blood oxygen level-dependent (BOLD) signals associated with aging and cognitive function. In this study, we further hypothesized that the APOE genotype may affect the complexity of spontaneous BOLD activity in younger and older adults, and such altered complexity may be associated with certain changes in functional connectivity. We conducted a resting-state functional magnetic resonance imaging experiment in a cohort of 100 younger adults (aged 20-39 years; mean 27.2 ± 4.3 years; male/female: 53/47) and 112 older adults (aged 60-79 years; mean 68.4 ± 6.5 years; male/female: 54/58), and applied voxelwise MSE analysis to assess the main effect of APOE genotype on resting-state BOLD complexity and connectivity. Although the main effect of APOE genotype on BOLD complexity was not observed in younger group, we observed that older APOE ɛ4 allele carriers had significant reductions in BOLD complexity in precuneus and posterior cingulate regions, relative to noncarriers. We also observed that reduced BOLD complexity in precuneus and posterior cingulate regions was associated with increased functional connectivity to the superior and inferior frontal gyrus in the older group. These results support the compensatory recruitment hypothesis in older APOE ɛ4 carriers, and confer the impact of the APOE genotype on the temporal dynamics of brain activity in older adults.

Apolipoprotein E genotypes associated with Alzheimer disease and concomitant stroke

BACKGROUND

The ɛ4 allele of the apolipoprotein E (APOE) gene is a well-characterized genetic risk factor for Alzheimer disease (AD). The association between stroke and a higher risk for AD has also been reported. Our study sought to determine the relationship between the APOE gene and AD and the comorbid risk of stroke.

METHODS

The subjects of this study consisted of 48 patients with AD and 48 members of a control group. All subjects were genotyped for APOE.

RESULTS

The results clearly show a significant increased risk of AD in carriers of the APOE ε3/ε4 genotype (P = .003, odds ratio [OR] = 4.1) or ε4 allele (P = .001, OR = 4.2). The risk for stroke in AD patients was also increased for carriers of the APOE ε3/ε4 genotype (P = .02, OR = 9.0) and for carriers of the APOE ε4 allele (P = .004, OR = 5.5).

CONCLUSIONS

The present study is the first to establish a relationship between APOE ε4 and concomitant AD and stroke in the Tunisian population.

Potential blood biomarker for disease severity in the Taiwanese population with Alzheimer's disease

The identification of blood biomarkers for Alzheimer's disease (AD) could contribute for improvement in early diagnosis. To define AD biomarkers, we compared serum/plasma levels of amyloid β (Aβ), tau, cytokines, and biometals between AD and non-AD groups. Cognitive impairment was assessed by Mini-Mental Status Examination (MMSE) and Clinical Dementia Rating scales. Plasma concentrations of total Aβ, Aβ(42), tumor necrosis factor α (TNF-α), and interleukin 6 were quantified by immunoassays. Serum biometal concentrations were determined using flame atomic absorption spectrometry. We found that serum zinc (Zn) was lower in patients with AD. After controlling for age, the MMSE score correlated with both TNF-α and total Aβ levels in the AD group, while the MMSE score correlated with iron only in the non-AD group. Our finding that blood Zn, TNF-α, and total Aβ are possible biomarkers for AD diagnosis and prognosis validates the pervious publication on potential biomarker in the Taiwanese population.

Association of apolipoproteins e4 and c1 with onset age and memory: a study of sporadic Alzheimer disease in Taiwan

OBJECTIVE

To identify clinical manifestations and neuropsychological effects of Alzheimer disease (AD) in apolipoprotein (ApoE) e4 carriers and to investigate the relationships between ApoE HhaI polymorphism and apolipoprotein C1 (APOC1) HpaI polymorphism in Taiwanese patients with AD.

PARTICIPANTS AND METHODS

A total of 127 patients with AD and 191 elderly individuals were screened for ApoE and APOC1 polymorphism. All patients underwent neuropsychological testing, including a Mini-Mental Status Examination (MMSE), Clinical Dementia Rating (CDR), and/or the Visual Association Memory Test (VAMT) with Cognitive Abilities Screening Instrument.

RESULTS

The frequencies of the e4 and A alleles were significantly higher in the AD group. In the patients with AD, the e4 and A allele effects on those with an age-of-onset of 60 to 79 years were stronger than those with an age-of-onset of 80 years or higher. Visual Association Memory Test performance was significantly worse in e4-allele carriers but not in A-allele carriers, in the early AD, particularly in those affected with AD for less than 2 years. Although there was no statistically significant difference in genotypic frequency between patients and controls, the 2 genes were linked. In addition, the presence of the AA genotype concomitant with the e4 allele may be better associated with AD diagnosis than either factor alone.

CONCLUSION

We conclude that the e4 allele affects neuropsychological performance and illness morbidity. Concomitantly, ApoE e4 and APOC1 A alleles have a better association with AD than ApoE e4 alone. In addition, APOC1 may partially contribute to the pathogenesis of AD, but the nature of its relationship with e4 requires further investigation.

Reduced physiological complexity in robust elderly adults with the APOE epsilon4 allele

BACKGROUND

It is unclear whether the loss of physiological complexity during the aging process is due to genetic variations. The APOE gene has been studied extensively in regard to its relationship with aging-associated medical illness. We hypothesize that diminished physiological complexity, as measured by heart rate variability, is influenced by polymorphisms in the APOE allele among elderly individuals.

METHODOLOGY/PRINCIPAL FINDINGS

A total of 102 robust, non-demented, elderly subjects with normal functions of daily activities participated in this study (97 males and 5 females, aged 79.2+/-4.4 years, range 72-92 years). Among these individuals, the following two APOE genotypes were represented: epsilon4 non-carriers (n = 87, 85.3%) and epsilon4 carriers (n = 15, 14.7%). Multi-scale entropy (MSE), an analysis used in quantifying complexity for nonlinear time series, was employed to analyze heart-rate dynamics. Reduced physiological complexity, as measured by MSE, was significantly associated with the presence of the APOE epsilon4 allele in healthy elderly subjects, as compared to APOE epsilon4 allele non-carriers (24.6+/-5.5 versus 28.9+/-5.2, F = 9.429, p = 0.003, respectively).

CONCLUSIONS/SIGNIFICANCE

This finding suggests a role for the APOE gene in the diminished physiological complexity seen in elderly populations.

Accelerated hippocampal atrophy rates in stable and progressive amnestic mild cognitive impairment

Studies suggest that smaller hippocampal volume predicts Alzheimer's disease (AD) in mild cognitive impairment (MCI). However, few studies have demonstrated decline rates in cognition and hippocampal volume in MCI subjects with stable clinical presentation. Furthermore, the effects of apolipoprotein E (ApoE) on the change rates of medial temporal structures and cognition in MCI are rarely investigated. Fifty-eight subjects with amnestic MCI and 20 normal aging elderly controls received annual neuropsychological and magnetic resonance imaging (MRI) assessments. Annual decline rates in neuropsychological test scores, hippocampal and amygdalar volumes were calculated. ApoE genotypes were examined. Nineteen (32.7%) MCI subjects converted to AD during an average 22.5-month follow-up period. The annual hippocampal atrophy rate was correlated with a decline in memory test scores. The presence of the ApoE varepsilon4 allele did not affect the change rates in neuropsychological test scores and medial temporal structures volume. Compared to subjects with stable MCI (MCI-S) and normal aging, progressive MCI (MCI-P) had the highest annual decline rates in cognition and hippocampal volume. Logistic regression analysis showed that higher annual decline rates in hippocampal volume and global cognitive test scores were associated with conversion to AD. Furthermore, although MCI-S subjects had little cognitive decline, their hippocampal atrophy rates were higher than those of normal aging controls. Therefore, accelerated hippocampal atrophy rates may be an early and important presentation in MCI subjects.

The prevalence of dementia in the People's Republic of China: a systematic analysis of 1980-2004 studies

BACKGROUND

Dementia has been a major public health problem. However, there has not yet been a nationwide investigation or systematic analysis of the prevalence of dementia in China from 1980 to 2004.

OBJECTIVES

The aim of this study was to analyse the prevalence of dementia and its major subtypes [Alzheimer disease (AD), vascular dementia (VD)] among the population aged 60 years and older in China from 1980 to 2004.

METHODS

Epidemiological investigations on dementia in China published in journals and covering the period from 1980 to 2004 were identified manually and on-line by using CBMDISK, Chongqing VIP database and CNKI database. Those reported in English journals were identified using MEDLINE. Selected studies had to describe an original study defined by strict screening and diagnostic criteria. The fixed effects model or random effects model was employed according to statistical test for homogeneity.

RESULTS

Twenty-five studies were selected, the statistical information of which was collected for systematic analysis. Our results showed that AD and VD were the two major subtypes of dementia in China, and the pooled prevalence of AD and VD for the population aged 60 years and older was 1.6 and 0.8%, respectively. There was a higher prevalence of AD in the illiterate elderly population (3.2%) than in those who received years of education. The chronological prevalence of AD increased significantly from 1980 to 2004. In southern and northern China, the prevalence of AD was 2.0 and 1.2%, respectively, while VD was 0.6 and 1.1%, respectively.

CONCLUSIONS

In the last 24 years, AD and VD were the two major subtypes of dementia in China. The prevalence of AD may be affected by sex, education, occupation or age. The prevalence of VD, which was higher in northern than in southern China, seems not to be affected by age, sex or education.

Survival of ethnic Chinese with Alzheimer's disease: a 5-year longitudinal study in Taiwan

Survival time and mortality risk factors in patients with Alzheimer's disease (AD) have been documented in Western countries, but comparable information on the ethnic Chinese is scarce. We consecutively recruited 159 AD patients and 145 control subjects from the Memory Clinic of Taipei Veterans General Hospital. After admission to the study, each subject received clinical, neuropsychological, and psychiatric evaluation and apolipoprotein E genotyping. Survival status was followed for 5 years. Forty-six AD patients (28.9%) and 3 control subjects (2.1%) died during the 5-year follow-up period. The mean survival time for AD patients was 4.48 years (SD = 0.1 years) after the time of enrollment. Among individuals with AD, those with severe disease, older patients, and those experiencing hallucinations were at greater risk for increased mortality. As expected, AD shortened life expectancy in these patients. The factors found to correlate with a shorter life span may suggest effective health care strategies for AD patients.

Prediction of Alzheimer's disease in mild cognitive impairment: a prospective study in Taiwan

The relationship between apolipoprotein E (ApoE) and clinical manifestations of mild cognitive impairment (MCI) has not been investigated in non-Caucasian populations. This prospective study was conducted in an ethnic Chinese population to evaluate the correlations of ApoE genotype, cognitive performance, medial temporal structure volumes, and clinical outcome in amnestic MCI. Twenty normal elders, 58 MCI, and 20 mild Alzheimer's disease (AD) patients received neuropsychological, MRI, and ApoE genotype assessments at baseline. Patients with MCI had intermediate cognitive performance and hippocampal volumes between those in normal and AD groups. In each diagnostic group, epsilon4 carriers (E4+) consistently had smaller hippocampal volume than non-carriers (E4-) did. Nineteen MCI subjects (32.7%) converted to AD during the 3-year study period. Compared with MCI non-converters and E4- MCI converters, E4+ MCI converters had the smallest hippocampal volume. However, epsilon4 was not a predictor for AD. Both cognitive performance and hippocampal volume were predictive for progression to AD. However, stepwise Cox regression model integrating both neuropsychological and radiological variables showed that global cognitive performance was the only significant predictor for AD. A poor global cognitive score may be more crucial than a small hippocampal volume in the prediction of AD.

Association between acyl-coenzyme A: cholesterol acyltransferase gene and risk for Alzheimer's disease in Chinese

There is a compelling body of evidence indicating an association between cholesterol and Alzheimer's disease (AD). Acyl-coenzyme A: cholesterol acyltransferase 1 (ACAT1), an endoplasmic-reticulum-resident enzyme that catalyses the formation of cholesteryl esters (CEs) from cholesterol and long-chain fatty acids, modulates the generation of beta amyloid peptide (Abeta). A single nucleotide polymorphism rs1044925 in the sterol O-acyltransferase 1 (SOAT1), the gene encoding ACAT1, has been reported to be association with an increased risk for sporadic AD (SAD) in European population. In the present study, we examined the association of the SOAT1 rs1044925 polymorphism with SAD in our northern Han-Chinese (107 cases, 118 age and gender-matched controls) sample using polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) analysis. There was no genotypic (chi(2)=0.030, OR 0.942, 95% CI=0.478-1.857) or allelic (chi(2)=0.021, OR 0.955, 95% CI=0.508-1.794) association between SAD and controls, even when the data were stratified by APOEvarepsilon4 carrier status. Our results indicate that the polymorphism rs1044925 in the 3'UTR of SOAT1 gene does not affect the risk of SAD in the northern Han-Chinese.

Estrogen-metabolizing gene COMT polymorphism synergistic APOE epsilon4 allele increases the risk of Alzheimer disease

Alzheimer disease (AD) is a polygenic multifactorial disorder. Several studies suggested that the neuroprotective effect of estrogen was based on an APOE-dependent mechanism. The goals of the current study were to determine if the genes involved in estrogen metabolism were linked to the risk of AD and find out if there was an interaction between estrogen-metabolizing gene polymorphisms and the APOE epsilon4 allele in the risk of prevalent AD. We investigated 66 patients with AD and 86 age- and gender-matched normal subjects. The polymorphisms of APOE and estrogen-metabolizing genes CYP17, CYP1A1 and COMT were examined. No association was found between each estrogen-metabolizing gene polymorphism and AD. However, the COMT HH genotype and APOE epsilon4 allele had a synergistic effect on the risk of AD. Taking subjects with epsilon4-epsilon4-/HH- as reference, the risk of developing AD in subjects with one epsilon4 allele (epsilon4+epsilon4-/HH-) was 2.6 (95% confidence interval, CI, 0.7- 9.1); however, the risk in subjects with both HH and one epsilon4 (epsilon4+epsilon4-/HH+) increased to 3.6 (95% CI 1.2-10.6). The subjects with homozygous epsilon4 still had the highest risk in developing AD (odds ratio 6.6, 95% CI 0.6-69.6). The p value of the linear trend test for this regression model was 0.004. It is possible that a high metabolism of estrogen by COMT may have reduced the protective effect of estrogen in AD. Further studies to clarify this interaction may improve our understanding of the generic risks for AD.

Association analysis for the muscarinic M1 receptor genetic polymorphisms and Alzheimer's disease

In the ongoing search to reveal the pathophysiology of Alzheimer's disease (AD), the cholinergic system is important due to its role in cognitive function and its significance with respect to the results of postmortem pathology and animal model studies. For this investigation, we tested the hypothesis that the allelic variant (C267A) of the cholinergic receptor muscarinic 1 (CHRM1) confers susceptibility to AD or is related to its age of onset, in a sample population of 232 AD patients and 169 normal controls. The distribution of the CHRM1 genotypes (p = 0.919) and alleles (p = 0.327) did not differ significantly comparing AD patients and controls, even after stratification according to apolipoprotein E genotype. The onset age was not significantly different comparing the CHRM1 genotype groups. Our negative findings suggest that it is unlikely that the CHRM1 C267A polymorphism plays a substantial role in conferring susceptibility to AD. We propose that other genetic variations of CHRM1, relating either to AD or to the therapeutic response for AD, may need further investigation.

Association between apolipoprotein E polymorphism and Alzheimer disease in Tehran, Iran

Epsilon 4 allele of apolipoprotein E (APOE-epsilon4) is a major risk factor for Alzheimer's disease (AD). The association of APOE allele frequencies with AD remains unknown in developing countries. We examined the frequency of APOE alleles in 105 patients with AD and 129 cognitively normal subjects of similar age and sex (control group), in Tehran, Iran. The APOE-epsilon4 allele frequency was significantly higher in the AD subjects than in the control group (21% versus 6.2%, p < 0.001). In addition, the OR for APOE-epsilon4 heterozygous and homozygous subjects were 3.2 (p = 0.001) and 12.75 (p = 0.01), respectively. The OR was not uniform across age groups. The AD subjects carrying one or two APOE-epsilon4 allele showed earlier age-at-onset (p < 0.001). These data suggest that the APOE-epsilon4 allele increase the risk for AD in Tehran population in a dose and age-dependent manner. Although the APOE-epsilon2 allele frequency was lower in the AD subjects than in the control group (0.95% versus 2.7%, p = 0.15), APOE-epsilon2 was not associated with the onset of AD in Tehran's population. The OR for epsilon2 allele in AD subjects was 0.34 (p = 0.21). The genotype frequencies for epsilon3, epsilon4, and epsilon2 alleles in control subjects were 91.2, 6.1, and 2.7%, respectively. These values were similar to that reported for Turkish, Greece, Japanese, Spanish, and Moroccan populations, but they were significantly different from the reported values for the other ethnic populations. This observation emphasizes the importance of geographical location and ethnical background of the subjects in the study of APOE genotypes and their association with AD.

The allele interaction between apolipoprotein epsilon2 and epsilon4 in Taiwanese Alzheimer's disease patients

OBJECTIVE

This study aimed to determine the impact of the present of apolipoprotein epsilon (Apoepsilon) 2 on the relationship between Apoepsilon4 and Alzheimer's disease (AD).

METHOD

We examined ApoE genotypes in 428 Taiwanese patients with AD and 807 controls; all participants were older than 65 years.

RESULTS

The allele frequency of Apoepsilon4 was greater in AD patients than controls, but significantly lower than in Caucasians. The presence of an epsilon2 allele alone was not associated with lower risk for AD, but the presence of an epsilon2 allele was associated with an epsilon4 allele frequency similar to that of controls.

CONCLUSION

The low allele frequency of epsilon4 in persons with an epsilon2 allele suggests that this may be part of the protective effect of epsilon2 against AD.

Association between apolipoprotein CI HpaI polymorphism and sporadic Alzheimer's disease in Chinese

OBJECTIVE

To investigate into the relationship of apolipoprotein CI (ApoCI) polymorphism with sporadic Alzheimer's disease (AD) in Chinese.

SUBJECTS AND METHODS

A total of 257 AD patients and 242 age-matched elderly individuals were genotyped for the ApoCI HpaI and apolipoprotein E (ApoE) HhaI polymorphisms.

RESULTS

The ApoCI A allele was associated with AD of moderate to severe dementia when patients were divided into two subgroups according to Clinical Dementia Rating scale, and the AA genotype was strongly associated with moderate to severe AD in ApoE epsilon4 allele carriers [odds ratio (OR) = 8.19, 95% confidential interval: 1.28-52.30, after adjusting for age and gender by logistic regression analysis], although in total no significant differences of allele or genotype frequency between patients and controls were found.

CONCLUSION

The present study partially confirmed the previous findings, suggesting that the ApoCI A allele might contribute to the susceptibility to moderate to severe sporadic AD in Chinese.

Apolipoprotein E in schizophrenia: a French association study and meta-analysis

Schizophrenic disorders are complex genetic disorders that may involve multiple genes of small effect. Apolipoprotein E (ApoE) gene variants are associated with alterations in brain function and an increased risk of Alzheimer's disease (AD). However, conflicting results have been reported in schizophrenia. We compared the ApoE genotypes of 114 French Caucasian schizophrenic patients and 91 normal controls. No differences in ApoE allele or genotype frequencies were observed between the two groups. However, we observed a possible association between male schizophrenic patients and the ApoE epsilon 2 epsilon 3 genotype. In addition, a meta-analysis of all published case-control studies on ApoE and schizophrenia did not support a major role for ApoE gene variants in schizophrenia as a whole. However, ApoE may be associated with particular forms of schizophrenia.

Lack of association between the apolipoprotein E genotype and depression in Alzheimer's disease

The epsilon4 allele of apolipoprotein (apo E) is one of the risk factors for late-onset Alzheimer's disease (AD). We evaluated the association between apo E genotypes and depression in patients with AD. A psychiatrist interviewed all patients and their caregivers for depression using a Chinese version of the Structured Clinical Interview for the Diagnostic and Statistical Manual of Mental Disorders, Third Edition, Revised, and for the severity of depression using the Hamilton Depression Rating Scale (HDRS). Twenty-five of the 149 patients with AD were diagnosed with depressive disorders. The numbers of patients in each apo E genotype were 10 in epsilon2/3, 2 in epsilon2/4, 74 in epsilon3/3, 46 in epsilon3/4, and 17 in epsilon4/4. We did not find an association between depression and the presence or absence of the epsilon4 or epsilon2 allele. The HDRS scores were not different in patients with AD with the epsilon4 or epsilon2 allele or in those patients without them. Our study did not find an association between depression and the apo E epsilon4 or epsilon2 allele in AD.

A study of apolipoproteins E and A-I in cutaneous amyloids

BACKGROUND

Apolipoprotein E (apoE) is present in a variety of biochemically different amyloid deposits, including Alzheimer's disease, systemic amyloidosis and primary cutaneous amyloidosis (PCA). Among the three closely related alleleic forms of apoE, the epsilon4 allele is linked to Alzheimer's disease. Apolipoprotein A-I (apoA-I), another apolipoprotein, is also found in senile plaques of Alzheimer's disease and in amyloid of aortic atherosclerotic plaques. Furthermore, apoA-I has recently been found to be associated with hereditary cutaneous and cardiac amyloidosis.

OBJECTIVES

To determine whether the apoE epsilon4 allele is associated with increased risk of PCA and whether apoE and apoA-I are present in PCA and common secondary cutaneous amyloidosis (SCA) (i.e. basal cell carcinoma, Bowen's disease and seborrhoeic keratosis).

METHODS

We examined the apoE genotype in 57 Chinese patients with PCA and 58 normal healthy control subjects of similar age. In addition, immunohistochemical staining was performed to determine the localization of apoE and apoA-I in skin tissues from 15 patients with SCA and 15 with PCA.

RESULTS

The frequency of the epsilon4 allele in the PCA group was not significantly higher than that in the control group (8.8% vs. 6.9%, P > 0.05). ApoE was present in amyloid deposits in both PCA and SCA, but apoA-I was not detected in these cutaneous amyloid deposits.

CONCLUSIONS

ApoE is also a component of amyloid deposits in SCA. Although the genetic susceptibility of certain apoE isoforms may not be a crucial factor in the development of PCA and, although apoA-I is not associated with amyloid deposits of PCA and SCA, the role of apolipoproteins in amyloidogenesis deserves further scrutiny.

Genetic risk factors of sporadic Alzheimer's disease among Chinese in Taiwan

To evaluate the genetic factors for AD among a Chinese population in Taiwan, we studied the polymorphisms of six candidate genes of Alzheimer's disease (AD), including the regulatory region of apolipoprotein E (Apo-E, G-186T), the promoter of apolipoprotein E (Apo-E, A-491T), the bleomycin hydrolase gene (BH, A1450G), a mutation of alpha(2)-macroglobulin gene (A2M G2998A), low-density lipoprotein receptor-related protein gene (LRP, C766T), and alpha(1)-antichymotrypsin gene (ACT, -15Ala/Thr) in AD patients and non-affected elder individuals among Taiwanese Chinese. Eighty-two AD patients and 110 non-affected individuals were recruited for this study. We used polymerase chain reaction (PCR) and restriction enzyme digestion to identify their genotypes. The statistical examination was performed by combining the results of our previous reports - apolipoprotein E epsilon4 (ApoE-4), presenilin-1 intronic polymorphism (PS-1, allele 1/2), and the five-nucleotide deletion of alpha(2)-macroglobulin gene (A2M). Among these nine candidate genes of AD, the ApoE-4 allele is the only independent genetic risk factor for AD. The other candidate genes in this study were not associated with the occurrence of AD. In addition, there are no gene-gene interactions.

Genotypes and Phenotypes for Apolipoprotein E and Alzheimer Disease in the Honolulu-Asia Aging Study

Background: The utility of apolipoprotein E (ApoE) type as an indicator of genetic susceptibility to Alzheimer disease (AD) depends on the reliability of typing. Although ApoE protein isoform phenotyping is generally assumed equivalent to genotyping from DNA, phenotype-genotype differences have been reported.

Methods: ApoE genotype and phenotype results were examined for 3564 older (ages 71–93 years) Japanese-American male participants of the Honolulu-Asia Aging Study, an ongoing population-based study of aging and dementia.

Results: Both methods demonstrated similar associations of ApoE type with AD: a direct association with ApoE4 and a less dramatic inverse association ApoE2. Advanced age did not appear to influence the ApoE4-AD association. The association with AD among ApoE4 homozygotes [odds ratio (OR) = 14.7] was higher than expected based on an observed OR of 2.0 in heterozygotes. Phenotype-genotype nonconcordance was more frequent for ApoE2 than for ApoE4. The ApoE2 phenotype occurred at a frequency of 7.9% vs a genotype frequency of 4.9%, corresponding to a probability of 56% that an individual with ApoE2 phenotype had the same genotype.

Conclusions: Whereas E4 and E2 phenotypes and genotypes were comparably associated with AD, neither method would be expected to substantially improve the efficiency of case finding in the context of population screening beyond prediction based on age and education. Nonconcordance of phenotype and genotype was substantial for E2 and modest for E4 in this population. The ApoE4-AD association was independent of age.

Association between apolipoprotein E polymorphism and Alzheimer's disease in Koreans

We analyzed the aplolipoprotein E (APOE) genotypes of 110 probable AD patients and 226 cognitively normal controls in Koreans. The APOE epsilon4 allele was more prevalent in both early- and late-onset AD patients (P < 0.01) than in controls. The odds for the APOE epsilon4-heterozygous subjects were 2.7 (95% CI = 1.6-4.5), and those for the APOE epsilon4-homozygous subjects were 17.4 (95% CI = 2.0-147.3). But the odds were not uniform across age groups, and were higher in women than in men. Although the APOE epsilon2 allele frequency did not differ by diagnosis, the patients carrying an APOE epsilon2 allele showed delayed age-at-onset (P = 0.02). In conclusion, the APOE e4 allele increased the risk for AD in dose-dependent manner, and the APOE epsilon4-conferred AD risk was age- and sex-dependent in Koreans.

Association of apolipoprotein E genotype and intronic polymorphism of the presenilin-1 gene with Alzheimer's disease in elderly Taiwan Chinese

We studied the apoliprotein E (apo-E) allele frequencies and intronic polymorphism of the presenilin-1 (PS-1) gene in 55 patients with late-onset Alzheimer's disease (AD) and 93 age- and sex-matched controls. The apoE epsilon4 allele frequency was significantly higher in the AD group than in the control group (0.255 versus 0.070, P<0.0001). The odds ratio for AD in individuals with either one or two epsilon4 alleles was 5.22 (95% confidence interval: 2.32-11.70). The polymorphism within the region composing intron 3' to exon 8 of the PS-1 gene showed a similar distribution between AD patients and controls. This is the first study on the intronic polymorphism of the PS-1 gene in Chinese. Our results support an association between apoE epislon4 and AD in Chinese, but not between the intronic polymorphism of the PS-1 gene and AD. However, the allele frequency of apo-E epsilon4 among Chinese is lower than that among Caucasians. The interaction between apo-E and PS-1 genotypes is still unclear.

Evaluation of risk factors for Alzheimer's disease in elderly east Africans

A number of biological risk factors have been implicated for Alzheimer's disease (AD). The investigation of prevalence rates of AD in crosscultural populations has much potential in validating these factors. We previously assessed brain amyloid beta (A beta) protein deposition and other lesions associated with AD as possible markers for preclinical AD in elderly nondemented East Africans. In further analysis, we demonstrate that 17-19% of elderly East African subjects without clinical neurological disease exhibited neocortical A beta deposits and minimal neurofibrillary changes at necropsy that was qualitatively and quantitatively similar to that in an age-matched elderly control sample from Cleveland, OH. A beta deposits varied from numerous diffuse to highly localized neuritic plaques and were predominantly reactive for the longer A beta 42 species. In parallel studies, we evaluated another recently implicated factor in AD, the apolipoprotein E genotype. We found relatively high frequencies of the apolipoprotein E-epsilon 4 allele in elderly nondemented East Africans. The frequencies were comparable to those in other African populations but higher than in subjects from developed countries. Our limited study suggests that elderly East Africans acquire cerebral lesions found in AD subjects but the apolipoprotein E-epsilon 4 allele may not be a highly specific factor for the disease among East Africans.