Apolipoprotein E in Taiwan Chinese patients with dementia

Genetic Susceptibility Variants of Vascular Dementia among Asians: A Systematic Review and Meta-Analysis

INTRODUCTION

Vascular dementia (VaD), a neurocognitive impairment directly related to vascular injury, is the second most common cause of age-related dementia. Although numerous studies have investigated candidate genetic polymorphisms associated with VaD in Asia, the genetics of VaD remains unclear.

METHODS

This review provides an updated meta-analysis of genetic polymorphisms associated with VaD in Asians, using the PRISMA guidelines. Published literature up to May 2021 was extracted from the PubMed, Scopus, Ovid, and EBSCOhost databases. Meta-analysis was conducted using the Open Meta analyst, Review Manager, and MedCalc® Statistical Software. Trial sequential analysis (TSA) was performed using TSA viewer software.

RESULTS

A total of 46 eligible studies, comprising 23 genes and 35 single nucleotide polymorphisms, were retrieved. The meta-analysis was conducted on the following genetic polymorphisms, APOE ε2/3/4, MTHFR rs1801131, ACE rs4340 (I/D) gene polymorphism, and a PSEN1 intron 8 variant. The pooled odds ratio (ORs) revealed a significant increase in the risk of VaD in the apolipoprotein E (APOE) ε4 allelic model (OR, 1.79, p < 0.001), and the methylenetetrahydrofolate reductase (MTHFR) rs1801133 polymorphism T allele in the allelic model (OR, 1.23, p = 0.013).

CONCLUSION

Our findings provide evidence that genetic polymorphisms of the APOE ε4 allele and MTHFR rs1801133 T allele increase the risk of developing VaD in Asians. However, future large-scale investigations examining particularly on South-Eastern and West-Asian populations are highly recommended.

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.

Utilizing apolipoprotein E genotypes and associated comorbidities for the assessment of the risk for dementia

Introduction

Dementia is associated with many comorbidities while being related to Apolipoprotein E (ApoE) polymorphism. However, it is unclear how these clinical illnesses and genetic factors modify the dementia risk.

Methods

We enrolled 600 dementia cases and 6000 matched non-dementia controls, with identified ApoE genotype (ε4/ε4, ε4/ε3, and ε3/ε3). Eight comorbidities were selected by medical records, and counted if occurring within 3 years of enrollment.

Results

The dementia group had a higher ratio of carrying ε4 allele and prevalence of comorbidities than the non-dementia group. Homozygous ε4 carriers presented the broken line of dementia risk with the peak age at 65-75 years and odds ratio (OR) up to 6.6. The risk only emerged after 65 years of age in ε3/ε4 subjects with OR around 1.6-2.4 when aged > 75 years. Cerebrovascular accident (CVA) is the commonest comorbidity (14.6%). CVA, sleep disorder, and functional gastrointestinal disorders remained as significant risk comorbidities for dementia throughout all age groups (OR = 1.7-5.0). When functional gastrointestinal disorder and ε4 allele both occurred, the dementia risk exceeded the summation of individual risks (OR = 3.7 and 1.9 individually, OR = 6.0 for the combination). Comorbidities could also be predictors of dementia.

Conclusion

Combining the genetic and clinical information, we detected cognitive decline and optimize interventions early when the patients present a specific illness in a particular age and carry a specific ApoE allele. Of comorbidities, functional gastrointestinal disorder is the strongest predicting factor for dementia in ε4 allele carriers.

Protective effect of apolipoprotein E epsilon 3 on sporadic Alzheimer's disease in the Chinese population: a meta-analysis

Alzheimer's disease (AD) is fast becoming one of the most expensive, deadly and burdensome diseases in this century. It has the fastest-growing disease burden in China. Apolipoprotein E (APOE) polymorphic alleles are generally considered to be the primary genetic determinant of AD risk: individuals with the E4 allele are at increased risk of AD compared with individuals with the more common E3 allele. Since the intensity of the association varies among different ethnic groups, a separate meta-analysis of the Chinese population is needed. We searched Chinese and English databases to sift through literature over the past 20 years. Data on the APOE genotype and AD were collected for correlation analysis. OR was calculated according to APOE allele and genotype. A publication bias analysis and sensitivity analysis were performed, and the main results were further verified by subgroup analysis. The 116 eligible studies enrolled 23,396 patients with AD and 25,568 healthy controls. The study subjects covered at least 30 of the 34 provincial-level administrative regions (including Taiwan). The partial sex ratio was as follows: AD male/female; 10,291/11,240; control male/female, 11,304/12,428, [Formula: see text] = 0.122, P = 0.727. The results of the meta-analysis of alleles showed that I² > 50% and Q statistics were significant for all genotypes; therefore, the random effect model was selected. The frequency of the ApoE ε4 allele in AD was higher than that in healthy controls, and the difference was statistically significant (OR 2.847, 95% CI [2.611-3.101], P < 0.001). The frequencies of ApoE ε3 and ε2 in AD were lower than those in healthy controls, and the differences were statistically significant (ε3: OR 0.539, 95% CI [0.504-0.576], P < 0.001; ε2: OR 0.771, 95% CI [0.705-0.843], P < 0.001). The results of the meta-analysis of AD genotype showed that ApoE ε2/ε4 (OR 1.521, 95% CI [1.270-1.823], P < 0.001), ε3/ε4 (OR 2.491, 95% CI [2.267-2.738], P < 0.001) and ε4/ε4 (OR 5.481, 95% CI [4.801-6.257], P < 0.001) allele genotype frequencies were higher than those of the healthy controls. The differences were all statistically significant. Moreover, the ApoE ε2/ε2 (OR 0.612, 95% CI [0.504-0.743], P < 0.001), ε2/ε3 (OR 0.649, 95% CI [0.585-0.714], P < 0.001) and ε3/ε3 (OR 0.508, 95% CI [0.468-0.551], P < 0.001) genotypes were less frequent in patients with AD than in healthy controls, and the differences were statistically significant. The results of the sensitivity analysis and subgroup analysis were consistent with those of the whole model. These results provide support for the protective effect of the ApoE ε3/ε3 genotype against the development of AD. This research is the most comprehensive meta-analysis of the correlation between APOE and AD in the Chinese population by analysing the distribution of the APOE gene in patients with AD reported in the last 20 years. It was concluded that the APOE ε3 allele had a protective effect against sporadic AD in the Chinese population, with great significance, and that its protective effect was stronger than that of the ε2 allele.

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.

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

BACKGROUND

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

Effects of apolipoprotein E-epsilon4 and -epsilon2 in amnestic mild cognitive impairment and dementia in Shanghai: SCOBHI-P

OBJECTIVE

To determine apolipoprotein E (APOE)-epsilon4 and -epsilon2 frequencies and risk of mild cognitive impairment (MCI) and dementia in Shanghai, China.

METHODS

A total of 34 MCI and 34 dementia cases were recruited from an urban Memory Disorders Clinic and 32 controls were recruited from a residential community served by the clinic. Apolipoprotein E was genotyped using standard methods.

RESULTS

Among controls, frequencies were epsilon2, 0.11; epsilon3, 0.84; and epsilon4, 0.05; among MCI, 0.05, 0.77, and 0.18; and for dementia, 0.02, 0.84, and 0.15, respectively. In education-adjusted models, the odds ratio (OR) = 5.6 for dementia (95% CI = 1.09-29.3) and 4.7 for MCI (95% CI = 0.90-25.2) associated with any epsilon4 allele. The epsilon2 allele was inversely associated with dementia (OR = 0.12, 95% CI = 0.013-0.997) and MCI (OR = 0.38, 95% CI = 0.08-1.61).

CONCLUSIONS

APOE-epsilon4 increases and -epsilon2 decreases the risk of dementia vs normal cognition. Similar trends were observed for amnestic mild cognitive impairment (aMCI).

Lack of association between apolipoprotein E polymorphism and vascular dementia in Koreans

To investigate an association of vascular dementia (VD) with the apolipoprotein E (APOE) polymorphism, the APOE polymorphism of 100 VD patients, 100 age- and gender-matched Alzheimer disease (AD) patients, and 200 age- and gender-matched nondemented control (NC) subjects was genotyped. The distribution of APOE polymorphism was compared. Neither the APOE epsilon4 allele nor the APOE epsilon2 allele was more prevalent in the VD patients compared with the NC subjects (P > .1 by the chi 2 test), which was the case when both men and women were analyzed separately (P > .1 by the chi2 test) and when young patients (75 years old or less) and old patients (more than 75 years old) were analyzed separately (P > .1 by the chi2 test). The estimated statistical power was over 0.80 when the odds ratios (OR) for VD conferred to the APOE epsilon4 are assumed to be higher than 2.2 and the type I error probability is set at 0.05, which is much higher than the power of the previous studies on the VD/APOE association. In conclusion, the results suggested that APOE epsilon4 allele does not confer the risk for VD, and even if it does, it does so very modestly.

Apolipoprotein E, angiotensin-converting enzyme and kallikrein gene polymorphisms and the risk of Alzheimer's disease and vascular dementia

Lipoproteins and vascular factors may play roles in the development of Alzheimer's disease (AD) and/or vascular dementia (VaD). In this study, odd ratios (ORs) and 95% confidence intervals (CIs) for apolipoprotein E (APOE), angiotensin-converting enzyme (ACE), and kallikrein (KLK1) polymorphisms were computed to test their association with the disease by a case-control study. The risk of AD was significantly increased for individuals with APOE varepsilon4 allele (OR = 3.73, 95% CI = 2.38-5.98). The risk of AD was also significant for people with ACE DD genotype, D allele, or T-D haplotype [OR (95% CI) = 4.29 (1.96-10.23), 1.90 (1.35-2.70), or 2.91 (1.71-5.10), respectively]. The above association between ACE-VaD was also strong (p = 0.0012, 0.0050, 0.0007, respectively). Reporter constructs containing the -240 A or T allele displayed similar transcriptional activity in both HEK-293 and IMR-32 cells. Thus, another putative pathogenic marker that is linked with the Alu D allele might affect the risk of AD and VaD in Taiwan.

Poststroke Dementia in the Elderly

Risk of dementia increases after stroke, and poststroke dementia (PSD) is an important cause of disability in the elderly. The prevalence rates of PSD vary from 12.2% to 31.8% within 3 months to 1 year after stroke, depending on patient populations and the diagnostic criteria used in the numerous studies. Incidence rates of PSD increase with time after the stroke. Although vascular lesions and white matter changes can explain the cognitive disorders seen in stroke patients, an underlying neurodegenerative disorder may contribute to the development of PSD. Cognitive decline may pre-date the stroke and follow a progressive course after the stroke. The vascular and degenerative processes involved share common environmental and genetic risk factors. This review explains the mechanisms of dementia in stroke patients and identifies predictive factors for PSD. The following points are successively considered: (i) demographic characteristics of the patients, including age and level of education; (ii) prestroke cognitive decline; (iii) vascular risk factors, including diabetes mellitus and prior strokes; (iv) stroke characteristics, including severity and location of the vascular lesion; (v) co-morbid disorders; and (vi) abnormalities on brain imaging, including location, size and number of vascular lesions, white matter changes and cerebral atrophy. Older age, prestroke cognitive decline, stroke recurrence, hypoxic-ischaemic disorders, left-side infarcts, strategic infarcts and white matter lesions appear to be the main predictive factors of PSD. Prevention of stroke should reduce the morbidity and mortality associated with PSD. In addition, management of PSD with secondary prevention treatments could reduce occurrence of further strokes. Cholinesterase inhibitors may be beneficial not only in Alzheimer's disease associated with cerebrovascular lesions, but also for the treatment of cholinergic dysfunction arising from pure vascular dementia. Better knowledge of the risk factors for PSD, including environmental and genetic factors, should increase the effectiveness of preventive strategies in patients with this condition.