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

The function of sphingolipids in different pathogenesis of Alzheimer's disease: A comprehensive review

Sphingolipids (SPLs) represent a highly diverse and structurally complex lipid class. The discussion of SPL metabolism-related issues is of importance in understanding the neuropathological progression of Alzheimer's disease (AD). AD is characterized by the accumulation of extracellular deposits of the amyloid β-peptide (Aβ) and intraneuronal aggregates of the microtubule-associated protein tau. Critical roles of Aβ oligomer deposited and ganglioside GM1 could be formed as "seed" from insoluble GAβ polymer in initiating the pathogenic process, while tau might also mediate SPLs and their toxicity. The interaction between ceramide and α-Synuclein (α-Syn) accelerates the aggregation of ferroptosis and exacerbates the pathogenesis of AD. For instance, reducing the levels of SPLs can mitigate α-Syn accumulation and inhibit AD progression. Meanwhile, loss of SPLs may inhibit the expression of APOE4 and confer protection against AD, while the loss of APOE4 expression also disrupts SPLs homeostasis. Moreover, the heightened activation of sphingomyelinase promotes the ferroptosis signaling pathway, leading to exacerbated AD symptoms. Ferroptosis plays a vital role in the pathological progression of AD by influencing Aβ, tau, APOE, and α-Syn. Conversely, the development of AD also exacerbates the manifestation of ferroptosis and SPLs. We are compiling the emerging techniques (Derivatization and IM-MS) of sphingolipidomics, to overcome the challenges of AD diagnosis and treatment. In this review, we examined the intricate neuro-mechanistic interactions between SPLs and Aβ, tau, α-Syn, APOE, and ferroptosis, mediating the onset of AD. Furthermore, our findings highlight the potential of targeting SPLs as underexplored avenue for devising innovative therapeutic strategies against AD.

Association between Thyroid Hormones, Apolipoprotein E, and Cognitive Function among Cognitively-Normal Elderly Dwellers

OBJECTIVE

The correlation among the thyroid-related hormones, Apolipoprotein E ε4 (APOE ε4) and cognitive function has been reported despite controversial results. This study was designed to investigate this correlation among cognitively-normal elderly dwellers.

METHODS

This study assessed 507 cognitively normal individuals aged over 60 who underwent comprehensive hematological and neuropsychological assessments including the quantification of serum free thyroxine and thyroid stimulating hormone (TSH) as well as the Korean version of the Consortium Establish a Registry for Alzheimer's disease. The Korean version of Geriatric Depression Scale was also employed to evaluate the severity of depression. Age, gender, education, and the presence of APOE ε4 were taken into account as covariates.

RESULTS

There was a significant positive association between verbal fluency test (VFT), Word List Memory Test (WLMT), and Word List Recall Test (WLRT) score and serum TSH levels (p=0.007, 0.031, and 0.023 respectively). The further analysis adding the interaction between APOE ε4 and TSH level, however, revealed only VFT score was significantly influenced by this interaction (p=0.026).

CONCLUSION

Lower serum TSH levels had impacts on both semantic memory (VFT) and episodic memory (WLMT, WLRT) among cognitively-normal elderly, whereas the interaction of TSH and APOE ε4 influenced only the task of semantic memory (VFT) in this group.

Distribution and clinical impact of apolipoprotein E4 in subjective memory impairment and early mild cognitive impairment

The apolipoprotein E (APOE) e4 allele is the most common genetic variant associated with Alzheimer’s disease (AD). We sought to investigate the distribution of APOE genotypes across the full clinical AD spectrum including AD, late-stage amnestic mild cognitive impairment (L-aMCI), early-stage aMCI (E-aMCI), subjective memory impairment (SMI), and controls. We prospectively recruited 713 AD patients, 735 aMCI patients, 575 SMI patients, and 8,260 individuals as controls. The frequency of the APOE e4 allele revealed an ordered fashion in the AD (30.8%), L-aMCI (24.0%), E-aMCI (15.1%), SMI (11.7%), and control (9.1%) groups. APOE e3/e4 and e4/e4 genotype frequencies also appeared in an ordered fashion in the AD group (39.1% of e3/e4 and 10.9% of e4/e4), as well as the L-aMCI (28.3% and 9.4%), E-aMCI (22.3% and 3.7%), SMI (18.3% and 1.9%), and control (15.1% and 0.8%) groups. In the comparisons of APOE e3/e3 vs. e3/e4 genotypes, all patient groups had a higher frequency of APOE e3/e4 relative to the control group. Relative to the SMI and E-aMCI groups, the AD and L-aMCI groups had higher frequency of the APOE e3/e4 genotype, and the AD group had a higher frequency relative to the L-aMCI group. However, there was no significant difference between the E-aMCI and SMI groups. In our longitudinal data, APOE e4 carrier showed a steeper incline slope in a clinical dementia rating sum of boxes (CDR-SB) score than APOE e4 non-carrier in SMI (B = 0.0066, p = 0.0104), E-aMCI (B = 0.0313, p < 0.0001), and L-aMCI (B = 0.0178, p = 0.0007). APOE e4 carrier showed a steeper decline slope in the CDR-SB than APOE e4 non-carrier in AD (B = − 0.0309, p = 0.0003). These findings suggest that E-aMCI and SMI are associated with a similarly increased frequency of the APOE e4 allele compared to controls, suggesting a greater genetic risk for AD and the importance of monitoring the allele more closely.

"Choosing Wisely": Apolipoprotein E Genetic Testing for the Diagnosis of Alzheimer's Disease in Dementia Clinics

BACKGROUND

Apolipoprotein E (APOE) ɛ4 allele carriers have an increased risk of late-onset Alzheimer's disease (AD). However, in the "Choosing Wisely" campaign for avoiding unnecessary medical tests, treatments, and procedures, APOE genetic testing is not recommended as a predictive test for AD.

OBJECTIVE

The aim of this study was to investigate the potential value of APOE genetic testing in a specific clinical context.

METHODS

Subjects with poor performance in the Korean version of the Mini-Mental Status Examination for dementia screening (MMSE-DS) with a Z-score of less than -1.5 were recruited from the public health centers. All participants underwent APOE genetic testing. Family history of dementia (FHx) was confirmed if one or more first-degree relatives had dementia.

RESULTS

Among 349 subjects, 162 (46.4%) were diagnosed with AD. APOEɛ4 allele carriers had a much higher risk of AD in the group with FHx than in the group without FHx (OR = 15.81, 95% CI = 2.74-91.21 versus OR = 1.82, 95% CI = 1.00-3.27, z = 2.293, p = 0.011). The sensitivity, specificity, positive predictive value, and negative predictive value for the APOEɛ4 allele were 47.7%, 90.9%, 91.3%, and 46.5% in the group with FHx.

CONCLUSION

It would be a wise choice to perform the APOE genetic testing for the diagnosis of AD in subjects with poor performance in a screening test and a family history of dementia.

Apolipoprotein E, cognitive function, and cognitive decline among older Taiwanese adults

Apolipoprotein E (APOE) genotype is believed to play a role in the onset of dementia, though less is known about its relationship with non-pathogenic age-related cognitive decline. We assessed whether APOE was a risk factor for cognitive decline among older Taiwanese adults using nationally representative data. General cognition was measured longitudinally over eleven years; domain-specific cognitive assessments of working memory, declarative learning and three aspects of attention (executive function, alerting, and orientation) were performed once. Having at least one risky APOE allele was associated with more rapid longitudinal cognitive decline compared to those with no risky alleles. Some evidence from the cross-sectional analysis of domain-specific cognitive assessments suggested that APOE genotype may be more closely associated with working memory and declarative learning than with attention. Most genetic studies of cognition include only populations of European descent; extension is crucial. This study confirmed the association between APOE genotype and the rate of cognitive decline in a predominantly Han Chinese population. Additional studies on diverse populations are warranted.

Synergistic interaction between APOE and family history of Alzheimer's disease on cerebral amyloid deposition and glucose metabolism

Background

Recently, the field of gene-gene or gene-environment interaction research appears to have gained growing interest, although it is seldom investigated in Alzheimer’s disease (AD). Hence, the current study aims to investigate interaction effects of the key genetic and environmental risks—the apolipoprotein ε4 allele (APOE4) and family history of late-onset AD (FH)—on AD-related brain changes in cognitively normal (CN) middle-aged and older adults.

Methods

[¹¹C] Pittsburg compound-B (PiB) positron emission tomography (PET) imaging as well as [¹⁸F] fluoro-2-deoxyglucose (FDG) PET that were simultaneously taken with T1-weighted magnetic resonance imaging (MRI) were obtained from 268 CNs from the Korean Brain Aging Study for Early Diagnosis and Prediction of AD (KBASE). Composite standardized uptake value ratios were obtained from PiB-PET and FDG-PET images in the AD signature regions of interests (ROIs) and analyzed. Voxel-wise analyses were also performed to examine detailed regional changes not captured by the ROI analyses.

Results

A significant synergistic interaction effect was found between the APOE4 and FH on amyloid-beta (Aβ) deposition in the AD signature ROIs as well as other regions. Synergistic interaction effects on cerebral glucose metabolism were observed in the regions not captured by the AD signature ROIs, particularly in the medial temporal regions.

Conclusions

Strong synergistic effects of APOE4 and FH on Aβ deposition and cerebral glucose metabolism in CN adults indicate possible gene-to-gene or gene-to-environment interactions that are crucial for pathogenesis of AD involving Aβ. Other unspecified risk factors—genes and/or environmental—that are captured by the positive FH status might either coexpress or interact with APOE4 to alter AD-related brain changes in CN. Healthy people with both FH and APOE4 need more attention for AD prevention.

Electronic supplementary material

The online version of this article (10.1186/s13195-018-0411-x) contains supplementary material, which is available to authorized users.

APOE and Alzheimer's Disease: Evidence Mounts that Targeting APOE4 may Combat Alzheimer's Pathogenesis

Alzheimer's disease (AD) is an immutable neurodegenerative disease featured by the two hallmark brain pathologies that are the extracellular amyloid ß (Aß) and intraneuronal tau protein. People carrying the APOE4 allele are at high risk of AD concerning the ones carrying the ε3 allele, while the ε2 allele abates risk. ApoE isoforms exert a central role in controlling the transport of brain lipid, neuronal signaling, mitochondrial function, glucose metabolism, and neuroinflammation. Regardless of widespread indispensable studies, the appropriate function of APOE in AD etiology stays ambiguous. Existing proof recommends that the disparate outcomes of ApoE isoforms on Aβ accretion and clearance have a distinct function in AD pathogenesis. ApoE-lipoproteins combine diverse cell-surface receptors to transport lipids and moreover to lipophilic Aβ peptide, that is believed to begin deadly events that generate neurodegeneration in the AD. ApoE has great influence in tau pathogenesis, tau-mediated neurodegeneration, and neuroinflammation, as well as α-synucleinopathy, lipid metabolism, and synaptic plasticity despite the presence of Aβ pathology. ApoE4 shows the deleterious effect for AD while the lack of ApoE4 is defensive. Therapeutic strategies primarily depend on APOE suggest to lessen the noxious effects of ApoE4 and reestablish the protective aptitudes of ApoE. This appraisal represents the critical interactions of APOE and AD pathology, existing facts on ApoE levels in the central nervous system (CNS), and the credible active stratagems for AD therapy by aiming ApoE. This review also highlighted utmost ApoE targeting therapeutic tactics that are crucial for controlling Alzheimer's pathogenesis.

Subjective memory complaint as a useful tool for the early detection of Alzheimer's disease

PURPOSE

Despite their high prevalence in Alzheimer's disease (AD), and the increasing level of concern they have generated, subjective memory complaints (SMCs) are poorly understood. This study investigated the accuracy with which SMC can separate mild cognitive impairment (MCI) and early AD from cognitive normal (CN), and explored whether the discrimination ability is similar to or better than that of the Mini-Mental State Exam (MMSE).

PATIENTS AND METHODS

This study recruited 175 CN subjects, 52 with MCI, and 66 with probable AD aged 60 years or older. To test the independent contributions of SMC and MMSE scores to the classification of cognitive status (CN vs MCI or early AD), logistic regression analyses were performed, adjusting for the following potential confounding variables: age, gender, Frontal Assessment Battery score, modified Hachinski Ischemic Scale score, and apolipoprotein E ε4 status. Receiver operating characteristic (ROC) curve analyses were used to determine the discrimination accuracy of SMC and MMSE scores, and area under the ROC curve (AUROC) was also calculated.

RESULTS

In the highly educated (≥7 years), nondepressed (Geriatric Depression Scale ≤15) subgroup, SMC showed good accuracy in discriminating cognitively impaired subjects from CN after adjusting for potential confounding variables (the AUROC of the adjusted SMC was 0.841 for MCI discrimination, and it was 0.858 for MCI plus early AD discrimination). Both SMC and MMSE scores significantly contributed to differentiating between CN and MCI (OR=2.372, 95% CI=1.086-5.177; OR=0.730, 95% CI=0.566-0.941, respectively) after adjusting for the same covariates. However, in the highly educated and nondepressed subgroups, SMC showed significant predictive power for MCI from CN (OR=3.119, 95% CI=1.190-8.176; OR=3.328, 95% CI=1.320-8.396, respectively), whereas MMSE scores did not.

CONCLUSION

Our findings support the usefulness of SMC, which was comparable or even superior to MMSE scores, for detecting MCI or early AD.

Bosnian study of APOE distribution (BOSAD): a comparison with other European populations

BACKGROUND

The ε2, ε3 and ε4 alleles of APOE gene have been associated with several diseases in different populations. Data on the frequency of alleles are used in both a clinical and evolutionary context. Although the data on frequency of these alleles are numerous, there are no reports for the population of Bosnia and Herzegovina.

AIM

To estimate the frequency of APOE alleles in a healthy Bosnian population and compare it to data for other European populations.

SUBJECTS AND METHODS

Overall, 170 unrelated Bosnian subjects (108 female and 62 male), aged 53.0 (±5.0) years were included in this study. Genotypes were determined by real-time PCR.

RESULTS

In our group the prevalence of heterozygotes E2/E3, E2/E4 and E3/E4 was 20.6%, 3.5% and 12.9%, respectively, while the prevalence of homozygotes E2/E2, E3/E3, E4/E4 was 0.6%, 61.2% and 1.2%, respectively, with a mean frequency of ε2, ε3 and ε4 alleles of 12.6%, 78.0% and 9.4%, respectively.

CONCLUSIONS

In studied European populations we observed a linear, gradually increasing trend in the frequency of ε4 allele from South to North (Pearson's test 0,7656, p value <0.00001), and the Bosnian population fits into this pattern perfectly.

Apolipoprotein ε7 allele in memory complaints: insights through protein structure prediction

PURPOSE

APOE ε7 gene is a rare mutant form of APOE ε3. The mutation occurs in the lipid-binding domain of APOE. Based on the protein's structure, APOE ε7 is expected to function in lipid and β-amyloid metabolism, similar to APOE ε4. However, unlike that for APOE ε4, the mechanisms responsible for Alzheimer's disease (AD) cases associated with APOE ε7 expression have not been elucidated. The present study aims to investigate the association between APOE ε7 expression and cognitive impairment.

METHODS

APOE was sequenced in DNA samples collected from 344 memory-complaint patients who visited the memory clinic, and from 345 non-memory-complaint individuals from the health promotion center. The protein structures of ApoE3, ApoE4, and ApoE7 were predicted.

RESULTS

Three ε3/ε7 heterozygote individuals who were all classified under the memory-complaint group were identified. Of these, two subjects were clinically diagnosed with AD with small vessel disease, and the remaining individual was diagnosed with subjective cognitive impairment. This study predicted the protein structures of ApoE3, ApoE4, and ApoE7 and determined the three-dimensional structure of the carboxy terminus of ApoE7, which participates in an electrostatic domain interaction similar to that of APOE ε4. APOE K244 or K245 mutations for APOE ε7 were not found in the Korean reference genome database, which contains information (http://152.99.75.168/KRGDB/browser/mainBrowser.jsp) from 622 healthy individuals.

CONCLUSION

As verified by the results of structural prediction, APOE ε7 could serve as another risk factor for cognitive impairment and is particularly associated with vascular disease. However, additional studies are required to validate the pathogenic nature of APOE ε7.

Apolipoprotein E as a Therapeutic Target in Alzheimer's Disease: A Review of Basic Research and Clinical Evidence

Alzheimer's disease (AD) is a devastating neurodegenerative disorder that causes progressive cognitive decline. The majority of AD cases are sporadic and late-onset (>65 years old) making it the leading cause of dementia in the elderly. While both genetic and environmental factors contribute to the development of late-onset AD (LOAD), APOE polymorphism is a major genetic risk determinant for LOAD. In humans, the APOE gene has three major allelic variants: ε2, ε3, and ε4, of which APOE ε4 is the strongest genetic risk factor for LOAD, whereas APOE ε2 is protective. Mounting evidence suggests that APOE ε4 contributes to AD pathogenesis through multiple pathways including facilitated amyloid-β deposition, increased tangle formation, synaptic dysfunction, exacerbated neuroinflammation, and cerebrovascular defects. Since APOE modulates multiple biological processes through its corresponding protein apolipoprotein E (apoE), APOE gene and apoE properties have been a promising target for therapy and drug development against AD. In this review, we summarize the current evidence regarding how the APOE ε4 allele contributes to the pathogenesis of AD and how relevant therapeutic approaches can be developed to target apoE-mediated pathways in AD.

Multicenter, randomized, placebo-controlled, double-blind clinical trial of escitalopram on the progression-delaying effects in Alzheimer's disease

OBJECTIVES

A series of preclinical studies have suggested that selective serotonin reuptake inhibitor antidepressants not only stimulate neurogenesis but also have neuroprotective effects. The present study primarily aimed to investigate whether escitalopram would decelerate the brain atrophy of patients with mild-to-moderate Alzheimer's disease (AD). We also assessed the effects of escitalopram on the cognitive function and neuropsychiatric symptoms of these participants.

METHODS

Seventy-four probable AD patients without major depression were recruited from four dementia clinics of university hospitals and randomly assigned in a 1:1 ratio. Each group received 20 mg/day of escitalopram or placebo for 52 weeks. The primary outcome measures were the change rates of hippocampal and whole brain volume on magnetic resonance imaging for 52 weeks. The Alzheimer's Disease Assessment Scale-cognitive subscale, Mini-Mental State Examination, Neuropsychiatric Inventory, and Cornell Scale for Depression in Dementia (CSDD) were also applied.

RESULTS

We did not find any significant differences in the changes of hippocampal or whole brain volume between the groups. Escitalopram showed significant beneficial effects on the CSDD score at 28 weeks compared with placebo (t = -2.17, df = 50.42, p = 0.035), but this finding did not persist throughout the study.

CONCLUSION

The findings of the present study do not support the role of escitalopram as a progression-delaying treatment for AD. However, the negative results of the present trial should be interpreted cautiously because of the relatively small sample size. Further large-scale escitalopram trials targeting the earlier stages of AD, even prodromal AD, are still needed. Copyright © 2015 John Wiley & Sons, Ltd.

Genetic and Transcriptomic Profiles of Inflammation in Neurodegenerative Diseases: Alzheimer, Parkinson, Creutzfeldt-Jakob and Tauopathies

Polymorphisms in certain inflammatory-related genes have been identified as putative differential risk factors of neurodegenerative diseases with abnormal protein aggregates, such as sporadic Alzheimer’s disease (AD) and sporadic Parkinson’s disease (sPD). Gene expression studies of cytokines and mediators of the immune response have been made in post-mortem human brain samples in AD, sPD, sporadic Creutzfeldt-Jakob disease (sCJD) subtypes MM1 and VV2, Pick’s disease (PiD), progressive supranuclear palsy (PSP) and frontotemporal lobar degeneration linked to mutation P301L in MAPT Frontotemporal lobar degeneration-tau (FTLD-tau). The studies have disclosed variable gene regulation which is: (1) disease-dependent in the frontal cortex area 8 in AD, sPD, sCJD MM1 and VV2, PiD, PSP and FTLD-tau; (2) region-dependent as seen when comparing the entorhinal cortex, orbitofrontal cortex, and frontal cortex area 8 (FC) in AD; the substantia nigra, putamen, FC, and angular gyrus in PD, as well as the FC and cerebellum in sCJD; (3) genotype-dependent as seen considering sCJD MM1 and VV2; and (4) stage-dependent as seen in AD at different stages of disease progression. These observations show that regulation of inflammation is much more complicated and diverse than currently understood, and that new therapeutic approaches must be designed in order to selectively act on specific targets in particular diseases and at different time points of disease progression.

The nitric oxide synthase 3 G894T polymorphism associated with Alzheimer's disease risk: a meta-analysis

The association between the G894T polymorphism (Glu298Asp) of nitric oxide synthase 3 (NOS3) and risk of Alzheimer’s disease (AD) was explored by performing a meta-analysis of case-control studies. Bibliographical searches were conducted in the MEDLINE, EMBASE, and China National Knowledge Infrastructure (CNKI) databases without any language limitations. Two investigators independently assessed abstracts for relevant studies, and reviewed all eligible studies. We adopted regrouping in accordance with the most probably appropriate genetic model. Odds ratios (ORs) with 95% confidence intervals (CIs) were used to assess the strength of this association. We performed a meta-analysis including 21 published articles with 23 case-control studies (5,670 cases and 5,046 controls). In the analyses, we found significant association between G894T polymorphism and AD risk under a complete overdominant model (GG + TT vs. GT) (OR = 1.18; 95%CI, 1.04–1.35; P = 0.010). When stratified by time of AD onset, we found the association between this polymorphism and AD susceptibility to be more substantial among late onset patients than among early onset patients (OR for late vs. early onset: 1.33 vs. 1.02, P interaction = 0.049). The meta-analysis showed that the polymorphism G894T of NOS3 was associated with risk of AD.

The Effect of Choline Acetyltransferase Genotype on Donepezil Treatment Response in Patients with Alzheimer's Disease

Objective

We examined the difference in responses to donepezil between carriers and non-carriers of the A allele at the +4 position of the choline acetyltransferase (ChAT) gene in Koreans.

Methods

Patients who met the criteria for probable Alzheimer’s disease (AD) (n=199) were recruited. Among these, 145 completed the 12-week follow-up evaluation and 135 completed the 26-week scheduled course. Differences and changes in the Korean version of the mini-mental state examination (MMSE-KC) score, Korean version of the Consortium to Establish a Registry for Alzheimer’s Disease Neuropsychological Assessment Battery (CERAD-K[N]) wordlist subtest score (WSS), CERAD-K(N) total score (TS), and the Korean version of geriatric depression scale (GDS-K) score between baseline and 12 weeks or 26 weeks were assessed by the Student’s t-test.

Results

At 12 weeks, the changes in the MMSE-KC score, CERAD-K(N) WSS, and CERAD-K(N) TS from baseline were not significant between ChAT A allele carriers and non-carriers; however, at 26 weeks, these changes were significantly larger in ChAT A allele carriers than in non-carriers (p=0.02 for MMSE-KC and p=0.03 for CERAD-K(N) WSS respectively).

Conclusion

Our findings in this study suggested that presence of the A allele at the +4 position of ChAT might positively influence the treatment effect of donepezil in the early stages of AD in Koreans.

Association of apolipoprotein E genetic variation in Alzheimer's disease in Indian population: a meta-analysis

BACKGROUND

Dementia is an age-related disorder associated with elderly population, resulting from interaction of lifestyle risk factors with genetic, vascular, and other risk factors to affect risk of disease. Alzheimer's disease (AD) is the most common form of dementia, estimated to be affecting 4.4% of the population older than 65 years of age. Apolipoprotein E (ApoE) ε4 allele is a known genetic risk factor for AD, which not only predisposes and influences the severity of pathological changes in the brain, thereby modifying the age at onset, but also promotes cognitive decline early in nondemented older people.

OBJECTIVES

To review the published evidence on ApoE polymorphism with the susceptibility to AD and frequency of ApoE ε4 genotype (ε4/-) and homozygotes (ε4/4) among patients diagnosed with AD as compared to controls in Indian Population.

MATERIALS AND METHODS

In the present study, MEDLINE was reviewed for articles published till June 2013 supplemented by citation analysis from retrieved articles to select case-control studies. A meta-analysis was performed to demonstrate the association of ApoE gene with vascular dementia by random effects to demonstrate models. The association was assessed by odds ratio (OR) with 95% confidence intervals (CIs).

STUDY SELECTION

Case-control studies, using clinical criteria for AD with ApoE polymorphism determined for allele and genotype in both cases and controls.

STATISTICAL ANALYSIS

A meta-analysis was performed to demonstrate the association of ApoE gene with AD by random effects to demonstrate models. The association was assessed by OR with 95% CIs. We also looked for publication bias and performed sensitivity analysis to investigate the influence of each individual study.

RESULTS

A total of 7 studies representing data from 417 patients with AD and 651 controls in the Indian population were eligible. The ApoE ε2/4, ε3/4, and ε4/4 genotypes (OR = 3.93, 95% CI: 1.60-9.68; OR = 4.18, 95% CI: 2.54-6.87; OR = 4.81, 95% CI: 1.95-11.86, respectively) as well as ApoE ε4 allele (OR = 5.90, 95% CI: 3.44-10.13) were associated with an increased risk of AD, whereas ApoE ε2/3, ε3/3 genotypes (OR = 0.52, 95% CI: 0.32-0.83; OR = 0.28, 95% CI: 0.19-0.42), and ApoE ε3 allele (OR = 0.29, 95% CI: 0.17-0.50) were found to be marginally significant protective factors for AD. There was no significant difference in ApoE ε2/2 genotype and ApoE ε2 allele frequency (OR = 0.42; 95% CI: 0.11-1.68; OR = 0.69, 95% CI: 0.37-1.31, respectively) in patients with AD and controls.

CONCLUSIONS

These results indicate that all genotypes of ApoE ε4 allele, that is, ε2/4, ε3/4, and ε4/4, are associated with an increased risk of AD, whereas ApoE ε2/2, ε2/3, and ε3/3 are protective for AD.

The genetics of Alzheimer's disease

Alzheimer’s disease (AD) is a complex and heterogeneous neurodegenerative disorder, classified as either early onset (under 65 years of age), or late onset (over 65 years of age). Three main genes are involved in early onset AD: amyloid precursor protein (APP), presenilin 1 (PSEN1), and presenilin 2 (PSEN2). The apolipoprotein E (APOE) E4 allele has been found to be a main risk factor for late-onset Alzheimer’s disease. Additionally, genome-wide association studies (GWASs) have identified several genes that might be potential risk factors for AD, including clusterin (CLU), complement receptor 1 (CR1), phosphatidylinositol binding clathrin assembly protein (PICALM), and sortilin-related receptor (SORL1). Recent studies have discovered additional novel genes that might be involved in late-onset AD, such as triggering receptor expressed on myeloid cells 2 (TREM2) and cluster of differentiation 33 (CD33). Identification of new AD-related genes is important for better understanding of the pathomechanisms leading to neurodegeneration. Since the differential diagnoses of neurodegenerative disorders are difficult, especially in the early stages, genetic testing is essential for diagnostic processes. Next-generation sequencing studies have been successfully used for detecting mutations, monitoring the epigenetic changes, and analyzing transcriptomes. These studies may be a promising approach toward understanding the complete genetic mechanisms of diverse genetic disorders such as AD.

Exercise, APOE genotype, and the evolution of the human lifespan

Humans have exceptionally long lifespans compared with other mammals. However, our longevity evolved when our ancestors had two copies of the apolipoprotein E (APOE) ɛ4 allele, a genotype that leads to a high risk of Alzheimer's disease (AD), cardiovascular disease, and increased mortality. How did human aging evolve within this genetic constraint? Drawing from neuroscience, anthropology, and brain-imaging research, we propose the hypothesis that the evolution of increased physical activity approximately 2 million years ago served to reduce the amyloid plaque and vascular burden of APOE ɛ4, relaxing genetic constraints on aging. This multidisciplinary approach links human evolution with health and provides a complementary perspective on aging and neurodegenerative disease that may help identify key mechanisms and targets for intervention.

High APOE epsilon 4 allele frequencies associated with Alzheimer disease in a Tunisian population

The goal of the study was to examine the Apolipoprotein E (APOE) genotypes in a Tunisian sample of patients with Alzheimer disease (AD) and normal controls, and to compare the results with the findings from the literature. A hospital-based case-control study of two groups (58 patients with AD, 71 controls) was conducted. Patients received a detailed clinical history, neurological examination, neuropsychological testing and brain imaging. A neurological examination and the Arabic version of the Mini-Mental State Examination were made for controls. Genotyping was performed using the PCR restriction fragment length polymorphism (PCR-RFLP) method. There were no statistical differences in age (p = 0.05) and gender (p = 0.046) between the two groups. The APOE ε4/4 genotype was over represented in the AD group in comparison with the controls (13.3 vs. 2.8%). A significant increased risk of AD among APOE ε4 allele carriers was observed. The odds ratio for the association of AD patients with homozygous and heterozygous ε4 allele was, respectively, 5.40 (1.35-21.48) and 2.90 (1.27-6.62). Our results in addition to previously published genetic studies suggest that AD disease is multifactor in origin. Ethnicity, genetic and environmental factors contribute to AD risk in different ethnic groups.

Apolipoprotein E gene polymorphism and serum lipid levels in the Guangxi Hei Yi Zhuang and Han populations

Hei Yi Zhuang is an isolated subgroup of the Zhuang minority in China. Little is known about the distribution of apolipoprotein (apo) E genetic variations and its role in lipid metabolism in this population. The present study was undertaken to compare the effect of apoE gene polymorphism on serum lipid levels between the Guangxi Hei Yi Zhuang and Han populations. A total of 873 subjects of Hei Yi Zhuang and 867 participants of Han Chinese were surveyed by a stratified randomized cluster sampling. Genotyping of apoE was performed using polymerase chain reaction and restriction fragment length polymorphism. The frequencies of 2, 3, and 4 alleles were 15.23%, 79.84%, and 4.93% in Hei Yi Zhuang, and 9.23%, 81.43%, and 9.34% in Han (P < 0.001); respectively. The frequencies of 2/ 2, 2/ 3, 2/ 4, 3/ 3, 3/ 4, and 4/ 4 genotypes were 4.70%, 17.86%, 3.21%, 68.16%, 5.50%, and 0.57% in Hei Yi Zhuang, and 2.54%, 9.23%, 4.15%, 70.70%, 12.23%, and 1.15% in Han (P < 0.001); respectively. Total cholesterol (TC), triglyceride (TG), low-density lipoprotein cholesterol (LDL-C), and apoB levels were lower in Hei Yi Zhuang than in Han (P < 0.01-0.001), but high-density lipoprotein cholesterol (HDL-C) levels and the ratio of apoA-I to apoB were higher in Hei Yi Zhuang than in Han (P < 0.001 for each). There were significant differences in TC, HDL-C, LDL-C, and apoB levels among the six genotypes in both ethnic groups (P < 0.01-0.001). Hyperlipidemia was positively correlated with age, body mass index, hypertension, alcohol consumption, and apoE allele in both populations (P < 0.05-0.001). TC, LDL-C, and apoB levels were positively correlated, and HDL-C levels were negatively associated with apoE genotypes in both ethnic groups (P < 0.001 for all). The differences in the lipid profiles between Hei Yi Zhuang and Han Chinese might partly attribute to the differences in apoE genotypic and allelic frequencies.

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.

ApoE-ε 4-dependent association of the choline acetyltransferase gene polymorphisms (2384G>A and 1882G>A) with Alzheimer's disease

BACKGROUND

One of the characteristic features of Alzheimer's disease (AD) is the degeneration of the cholinergic system. The gene encoding choline acetyltransferase (ChAT), a key enzyme in cholinergic function, is a candidate gene conferring risk for AD. But the genetic association of the enzyme with AD has been controversial. We analyzed 2 ChAT single nucleotide polymorphisms (SNPs), 2384G>A (rs3810950; Ala120Thr) and 1882G>A (rs1880676; Asp7Asn) and the ApoE polymorphisms in Korean population.

METHODS

The samples from 316 AD patients and 264 age-matched healthy controls were analyzed. The differences in genotype frequencies were assessed.

RESULTS

The 2 ChAT SNPs were almost completely linked with each other (r2=0.99, |D'|=1.0). No significant difference in the ChAT genotype distribution was observed between the patients and the controls. However, in non-ApoE-epsilon4 allele carriers, multiple logistic regression analysis showed that both the GA and the GA/AA genotypes were associated with AD (OR=1.639, 95% CI, 1.050-2.559, p=0.0297 for GA; OR=1.630, 95% CI, 1.049-2.532, p=0.0297 for GA/AA), suggesting a dominant effect of A allele.

CONCLUSION

There is considerable effect of the ChAT polymorphisms on AD in Korean population and this effect is dependent on ApoE genotypes.

Combination of clinical and neuropsychologic information as a better predictor of the progression to Alzheimer disease in questionable dementia individuals

OBJECTIVES

This study aimed to examine the clinical outcomes of questionable dementia (QD) elderly subjects after three years of follow-up and to compare the ability of a standardized clinical assessment, neuropsychologic tests, the ApoE genotyping, and possible combinations of these methods to predict their progression to Alzheimer disease (AD).

METHODS

One hundred six elderly subjects with QD were evaluated with a standardized clinical assessment, neuropsychologic tests, and ApoE genotyping and followed up annually. The Clinical Dementia Rating Sum of Boxes (CDR-SOB) score was used as a quantitative summary score of the standardized clinical assessment on the overall functioning of the subjects.

RESULTS

Among the individuals remaining in the study after the 3-year follow-up period, 8.3% had improved to a state of normal cognition, 72.7% were still in the QD state. and 19.4% had progressed to clinically evident AD. Although each of CDR-SOB, Word List Recall (WLR), and ApoE epsilon4 genotype was predictive for AD, the combination of CDR-SOB and WLR was found to predict AD better than any single variable. However, the addition of the ApoE epsilon4 genotype information to CDR-SOB or WLR did not improve their predictive ability.

CONCLUSION

The combination of clinical assessment on function and episodic memory test can improve the predictive ability of each measure for progression to AD in QD individuals. However, ApoE genotyping dose not make an additional contribution to AD prediction in QD individuals when used in combination with clinical assessment or memory test.

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.

Choline acetyltransferase G +4 A polymorphism confers a risk for Alzheimer’s disease in concert with Apolipoprotein E ε4

To examine whether the single nucleotide polymorphism at position +4 of the choline acetyltransferase (ChAT) confers a risk for Alzheimer's disease (AD), we determined the ChAT and the Apolipoprotein (APOE) genotypes of the 246 AD patients and 561 non-demented controls. The ChAT AA genotype was found to confer the risk for AD in concert with the APOE epsilon4 by stochastic search variable selection (SSVS) approach. The odds of the ChAT AA for AD were 3.25 (95% CI = 1.17-9.03). The mean ages-at-onset of AD were lower in those carrying the ChAT AA than those carrying the ChAT AG or ChAT GG, regardless to the occurrence of the APOE epsilon4. The ChAT AA is a novel genetic risk factor AD, and the SSVS is a useful approach for analyzing association with multiple candidate genes simultaneously.

Apolipoprotein E epsilon 4 allele is not associated with the cognitive impairment in community-dwelling normal elderly individuals

OBJECTIVES

The aim of this study was to examine whether the APOE epsilon 4 allele also confers a risk for the cognitive impairment in normal aging.

METHODS

We administered all the eight neuropsychological tests from the CERAD neuropsychological battery to the CVD-free, community-dwelling normal elderly individuals, and compared their performance by the occurrence of the APOE epsilon 4 allele.

RESULTS

Either the impact of APOE epsilon 4 allele itself or its interaction terms with age and gender of the subjects did not influence the performance of the eight neuropsychological tests (epsilon p > 0.1 by ANCOVA).

CONCLUSIONS

The APOE epsilon 4 allele is not a risk factor for the cognitive decline in normal elderly individuals regardless of age and gender.

The domain-specific, stage-limited impact of the apolipoprotein E epsilon-4 allele on cognitive functions in Alzheimer's disease

To examine the impact of the APOE epsilon4 allele on the cognitive functions of Alzheimer's disease (AD) patients, we administered the eight neuropsychological tests from the Consortium to Establish a Registry for Alzheimer's Disease Neuropsychological Assessment Battery to 118 Korean AD patients. The impact of the APOE epsilon4 allele was significant in the Word List Recall Test (WLRT) and the Word List Recognition Test (WLRcT) only, and its impact was confined to the very mild AD (VMAD) patients (F = 7.65, d.f. = 2, p < 0.01 for WLRT; F = 3.27, d.f. = 2, p = 0.04 for WLRcT). In the VMAD group, the performance on the two tests of the APOE-epsilon4-positive patients was poorer than that of the APOE-epsilon4-negative patients. Our findings suggest that the impact of the APOE epsilon4 allele on cognitive functions in AD may be domain specific and confined to the early stage of AD.

Transferrin C2 variant does not confer a risk for Alzheimer's disease in Koreans

We analyzed the transferrin (TF) and apolipoprotein E (APOE) genotypes of 164 probable Alzheimer's disease (AD) patients and 239 cognitively normal elderly controls in Koreans. We failed to detect a significant difference in genotypic frequencies and allelic frequencies of the TF polymorphism between the AD group and control group (P>0.1 by Chi square test). The frequency of the TF C2 variant did not differ by the diagnosis when the APOE epsilon4-positive subjects and APOE epsilon4-negative subjects were analyzed separately (P>0.1 by Chi square test). The TF C2 variant did not influence the age-at-onset of AD independently or synergistically with the occurrence of the APOE epsilon4 allele (P>0.1 by ANOVA). The TF C2 variant did not confer a risk for AD in Koreans.

Relation of apolipoprotein E polymorphism to clinically diagnosed Alzheimer's disease in the Korean population

The gene for human apolipoprotein E (APOE) is found on the long arm of chromosome 19 (19q13.2) and exists in three common allelic forms, epsilon2, epsilon3, and epsilon4. The APOE epsilon4 allele is overrepresented in Alzheimer's disease (AD) and is accepted as a genetic risk factor. Some studies reported a protective effect of the APOE epsilon2 allele for AD. However, there are some ethnic variations in the proportion of different APOE alleles and their relationship to AD. We examine the distribution of APOE alleles from 30 AD patients and 158 controls in Korea. The control subjects were all cognitively intact unrelated Koreans. The frequencies of APOE alleles in AD patients were 18.3% (epsilon2), 58.3% (epsilon3), and 23.3% (epsilon4). The corresponding frequencies in controls were 13.3% (epsilon2), 72.5% (epsilon3), and 14.2% (epsilon4). The frequency of the APOE epsilon2 allele in AD patients was not significantly different from that in controls. When statistical analysis was conducted after the exclusion of the APOE epsilon2 allele, the frequency of the APOE epsilon4 allele in AD patients was significantly higher than that in controls (P < 0.05). These results support that the APOE epsilon4 allele plays a role as a risk factor for AD in Koreans and suggest that the APOE epsilon2 allele may not play a protective role in the development of AD in Koreans.

Association of alpha-2-macroglobulin deletion polymorphism with sporadic Alzheimer's disease in Koreans

Alpha-2-macroglobulin (A2M) deletion polymorphism was recently reported to be associated with Alzheimer's disease (AD) in a way comparable to apolipoprotein E (APOE) polymorphism in a family-based study. However, the association of A2M deletion polymorphism with AD has not been consistently replicated in successive case-controlled studies. In order to evaluate whether this A2M polymorphism is associated with AD in Koreans, we examined the frequencies of the A2M deletion (D) allele and D-bearing genotypes in a group of Koreans composed of 100 sporadic AD patients and 203 control subjects. The frequency of the deletion (D) allele (P=0.046) was significantly different between the total group of AD patients and the controls, although the frequency of the D-bearing genotypes did not attain significance (P=0.078). When the subjects were stratified according to age at onset, there was significant difference in the frequencies of the D allele (P=0.044) and D-bearing genotypes (P=0.041) between late-onset AD patients (> or =65 years) and the controls. However, no significant difference was observed between early-onset AD patients (<65 years) and the control group. Additionally, when we divided the late-onset AD and control subjects by APOE epsilon4 status, the difference of the A2M D allelic frequency was significant only in the APOE epsilon4 negative subjects (P=0.015). In conclusion, our data suggests that the A2M D allele is a modest risk factor for late-onset sporadic AD in Koreans, and the AD risk conferred by the A2M D allele increases in APOE epsilon4 negative subjects.