Apolipoprotein E -491 promoter polymorphism is an independent risk factor for Alzheimer's disease in the Chinese population

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.

The SNPs rs429358 and rs7412 of APOE gene are association with cerebral infarction but not SNPs rs2306283 and rs4149056 of SLCO1B1 gene in southern Chinese Hakka population

Background

Apolipoprotein E (ApoE) and solute carrier organic anion transporter family member 1B1 (SLCO1B1) regulate lipid metabolism. However, the relationship between genetic polymorphisms of APOE and SLCO1B1 and cerebral infarction (CI) remains unclear.

Methods

A total of 938 CI patients and 1028 control participants were included in the study. The rs429358 and rs7412 single nucleotide polymorphisms (SNPs) in the APOE gene and rs2306283 and rs4149056 SNPs in the SLCO1B1 gene were analyzed by fluorescence polymerase chain reaction (PCR).

Results

The genotype ɛ3/ɛ3 was the most common APOE genotype, with ɛ3 being the allele with the highest frequency, followed by ɛ4 and ɛ2. Statistically significant differences of genotype ɛ2/ɛ2 (χ² = 3.866, P = 0.049), ɛ2/ɛ3 (χ² = 20.030, P < 0.001), ɛ3/ɛ4 (χ² = 16.960, P < 0.001), and ɛ4/ɛ4 (χ² = 4.786, P = 0.029) between CI patients and controls were detected. The SLCO1B1 genotype *1b/*1b and haplotype *1b showed the highest frequency in the study sample. There was no statistically significant difference in the frequencies of SLCO1B1 genotypes and haplotypes among CI patients comparing with controls. Moreover, ε4 carriers had significantly higher low-density lipoprotein-cholesterol (LDL-C) and apolipoprotein B (Apo-B) and lower apolipoprotein A1 (Apo-A1)/Apo-B levels than ε2 and ε3 carriers, but ε2 carriers showed lower LDL-C and Apo-B and higher Apo-A1/Apo-B than ε3 and ε4 carriers. Further, logistic regression analysis revealed that high LDL-C, high ApoB, smoking, hypertension and the ε4 allele were risks for the presence of CI.

Conclusions

This study indicated that the APOE SNPs rs429358 and rs7412 may be associated with susceptibility to cerebral infarction in southern Chinese Hakka population.

Analysis of apolipoprotein E genetic polymorphism in a large ethnic Hakka population in southern China

There is currently no data about the genetic variations of APOE in Hakka population in China. The aim of this study was to analyze the allelic and genotypic frequencies of APOE gene polymorphisms in a large ethnic Hakka population in southern China. The APOE genes of 6,907 subjects were genotyped by the gene chip platform. The allele and genotype frequencies were analyzed. Results showed that the ∊3 allele had the greatest frequency (0.804) followed by ∊2 (0.102), and ∊4 (0.094), while genotype ∊3/∊3 accounted for 65.43% followed by ∊2/∊3 (15.85%), ∊3/∊4 (14.13%), ∊2/∊4 (3.01%), ∊4/∊4 (0.84%), and ∊2/∊2 (0.74%) in all subjects. The frequencies of the ∊4 allele in Chinese populations were lower than Mongolian and Javanese, while the frequencies of the ∊2 allele were higher and ∊4 allele lower than Japanese, Koreans, and Iranian compared with the geographically neighboring countries. The frequencies of ∊2 and ∊4 alleles in Hakka population were similar to the Vietnamese, Chinese-Shanghai, Chinese-Kunming Han and Chinese-Northeast, and French. The frequency of ∊2 in Hakka population was higher than Chinese-Dehong Dai and Chinese-Jinangsu Han. The low frequency of the APOE ∊4 allele may suggest a low genetic risk of Hakka population for cardiovascular disease, Alzheimer's disease, and other diseases.

Analysis of SLCO1B1 and APOE genetic polymorphisms in a large ethnic Hakka population in southern China

OBJECTIVE

Statins are the most widely used lipid-lowering drugs, which have a significant effect on the inhibition of cardiovascular disease. The efficacy and side effects of statins are associated with the polymorphisms of SLCO1B1 and APOE genes. The purpose of this study was to analyze the SLCO1B1 and APOE gene polymorphisms in the Hakka population of southern China.

METHODS

A total of 3249 subjects including 2019 males and 1230 females participated in this study. Polymerase chain reaction (PCR)-fluorescence probe technique for polymorphisms analysis and analyzed the genotypes frequencies of SLCO1B1 and APOE genes.

RESULTS

The frequencies of SLCO1B1 521T>C between men and women were statistically significant (SLCO1B1 521TT, χ2  = 8.431, P = .004; SLCO1B1 521TC, χ2  = 7.436, P = .007). The frequencies of haplotypes *1b/*1b (40.07%) and *1a/*1b (32.56%) of SLCO1B1 gene accounted for 72.63%, followed by *1b/*15(14.40%), *1a/*1a (5.82%), *1a/*15 (5.57%), *15/*15 (1.45%), and *1a/*5 (0.12%). The frequencies of haplotypes *1a/*15 and *1b/*1b of SLCO1B1 gene between men and women were statistically significant (*1a/*15, χ2  = 6.789, P = .009; *1b/*1b, χ2  = 3.998, P = .004). In this study, genotype ɛ3/ɛ3 accounted for 69.04%, followed by ɛ3/ɛ4 (16.19%), ɛ2/ɛ3 (11.60%), ɛ2/ɛ4 (1.35%), ɛ4/ɛ4 (1.08%), and ɛ2/ɛ2 (0.74%) in all subjects, in which ɛ3 had the greatest allele frequency (82.93%), followed by ɛ4 (9.85%) and ɛ2 (7.22%). We found that 47 subjects carrying the SLCO1B1 521 (CC) polymorphism who had not any myopathy caused by statins.

CONCLUSIONS

We analyzed the SLCO1B1 and APOE gene polymorphisms in the Hakka population of southern China. This study provides a reference for the individualized meditation for Hakka population in this area.

Association between polymorphisms in the promoter region of the apolipoprotein E (APOE) gene and Alzheimer's disease: A meta-analysis

Several studies have evaluated the role of polymorphisms in the promoter region of APOE gene that encodes apolipoprotein E (APOE) and the susceptibility to Alzheimer's disease (AD). The aim of this literature review and meta-analysis was to investigate the relationship between the APOE promoter region single nucleotide polymorphisms (SNPs) (rs449647, -491A/T; rs769446, -427T/C and rs405509 -219T/G) and the risk of developing AD. Eligible controlled studies published up to November 2016 were retrieved from main online scientific and medical databases. Odds ratio (OR) and 95 % confidence interval (CI) were used to calculate the strength of the relationship. A total of 23 publications (19 for rs449647, ten for rs769446 and ten for rs405509) were retrieved that included 5,703 patients with AD and 5,692 controls. The C allele of the rs769446 variant of the promoter region of APOE gene was significantly associated with an increase of risk of AD (OR = 1.271, 95 % CI = 1.114-1.449, P < 0.0001), while other genetic models of this variant were not related with susceptibility to AD. Rs449647 and rs405509 polymorphisms of APOE gene were not associated with an increase of risk of AD. The findings of this literature review and meta-analysis have shown that rs769446 polymorphism in the promoter region of APOE gene could be a risk factor for AD. Future large-scale studies on the role of polymorphisms in the promoter region of APOE gene in AD are still awaited.

The algorithm for Alzheimer risk assessment based on APOE promoter polymorphisms

Background

Over the past two decades, the APOE gene and its polymorphisms have been among the most studied risk factors of Alzheimer disease (AD) development; yet, there are discrepancies between various studies regarding their impact. For this reason, the evaluation of the APOE genotype has not been included in the current European Federation of Neurological Societies guidelines for AD diagnosis and management. This aim of this study was to add to this discussion by assessing the possible influence of multiple polymorphisms in the promoter region of the APOE gene and genotypes of its allele E on the risk for dementia.

Methods

We performed a comprehensive analysis of APOE gene polymorphisms, assessed the detected genotypes and correlated molecular findings with serum apolipoprotein E concentrations. The study comprised 110 patients with AD and 110 age-matched healthy individuals from the Polish population.

Results

Four polymorphisms of the APOE gene had minor allele frequency exceeding 5 % and were included in the analysis: −491A/T (rs449647), −427T/C (rs769446), −219T/G (rs405509) in the promoter region and +113G/C (rs440446) in intron 1. A protective effect of the −219G allele on AD development was observed. Also, the −491T and −219G alleles were found to be underrepresented in the carriers of the APOE E4 variant. On the basis of the genotype and linkage disequilibrium studies, a relative score was attributed to given genotypes with respect to the estimated probability of their protective effects against AD, giving rise to the ‘preventive score’. This ‘preventive score’, based on the total sums of the relative scores, expresses the protective effect deriving from the synergistic action of individual single-nucleotide polymorphisms. The ‘preventive score’ was identified as an independent predictive factor.

Conclusions

We propose a novel, more complex approach to AD risk assessment based on the additive effect of multiple polymorphic loci within the APOE promoter region, which on their own may have too weak an impact to reach the level of significance. This has potentially practical implications, as it may help to improve the informative potential of APOE testing in a clinical setting. Subsequent studies of the proposed system in large, multi-ethnic cohorts are necessary for its validation and to assess its potential practical value for clinical applications.

Electronic supplementary material

The online version of this article (doi:10.1186/s13195-016-0187-9) contains supplementary material, which is available to authorized users.

Association between APOC1 polymorphism and Alzheimer's disease: a case-control study and meta-analysis

Background

Previous association studies examining the relationship between the APOC1 polymorphism and susceptibility to Alzheimer’s disease (AD) have shown conflicting results, and it is not clear if an APOC1 variant acts as a genetic risk factor in AD etiology across multiple populations.

Methods

To confirm the risk association between APOC1 and AD, we designed a case-control study and also performed a meta-analysis of previously published studies.

Results

Seventy-nine patients with AD and one hundred fifty-six unrelated controls were included in case-control study. No association was found between the variation of APOC1 and AD in stage 1 of our study. However, our meta-analysis pooled a total of 2092 AD patients and 2685 controls. The APOC1 rs11568822 polymorphism was associated with increased AD risk in Caucasians, Asians and Caribbean Hispanics, but not in African Americans. APOE ε4 carriers harboring the APOC1 insertion allele, were more prevalent in AD patients than controls (χ² = 119.46, OR = 2.79, 95% CI = 2.31–3.36, P<0.01).

Conclusions

The APOC1 insertion allele, in combination with APOE ε4, likely serves as a potential risk factor for developing AD.

Association between Alzheimer disease and the -491T allele of regulatory region polymorphism of Apolipoprotein E in a Tunisian population

The apolipoprotein E (APOE) is a well-established risk factor for late-onset Alzheimer's disease (AD). Several studies have attempted to confirm the association between the polymorphism located at position -491 in the transcriptional regulatory region of the APOE gene and AD. We examined in 85 AD patients and 90 control subjects of a Tunisian population the potential involvement of this polymorphism as a risk factor for AD, either through an independent effect or through interaction with the existing APOE ε4 allele risk. The T allele frequency was significantly higher in the AD patients group (45.3 %) than in the controls group (32.78 %) and may possibly constitute a significant risk factor for AD. The APOE ε4 allele did not influence the distribution of the -491 polymorphism after stratification.

The complex interaction between APOE promoter and AD: an Italian case-control study

The single nucleotide polymorphisms (SNPs) rs449647, rs769446 and rs405509 in the promoter region of the APOE gene have been variously suggested to be epsilon 4-independent risk factors for Alzheimer's disease (AD). A previous Italian study found that the rs449647 was significantly associated with late-onset AD. The aim of this study was to verify whether these APOE promoter SNPs are genetic risk factors for AD and to investigate their interaction with the common APOE polymorphism. A total of 169 clinically diagnosed AD patients and 99 cognitively intact age-matched controls were included in the study. Significant associations with AD independent from sex, age and APOE/epsilon 4 status were found for rs449647 A/A and rs405509 G/G genotypes (positive), and rs449647 A/T and rs405509 T/T genotypes (negative). Haplotype frequency estimation at the APOE locus showed significant associations for the ATG4, ATT4 and ACG3 (positive) and ATT2, ATT3 and TCG3 (negative) haplotypes. Therefore this study confirms the role of the rs449647 A/A genotype as risk factor for AD in Italy and suggests that promoter genotypes and APOE haplotypes might have a complex function in AD-associated genetic risk factors.

Association of Apolipoprotein E Polymorphisms With Normal Tension Glaucoma in a Chinese Population

PURPOSE

To evaluate the role of apolipoprotein E (APOE) polymorphisms in primary open angle glaucoma (POAG).

METHODS

A cohort of 400 unrelated Chinese POAG patients was examined, including 294 cases of high tension glaucoma (HTG) and 106 with normal tension glaucoma (NTG). Also studied were 300 unrelated Chinese control subjects. The genotypes of the APOE polymorphisms in exon 4 and in the promoter at positions -491, -427, and -219 were determined by polymerase chain reaction and restriction endonuclease analysis. Frequencies of the genotypes were compared between patients and controls by chi test or Fisher exact test. The association of APOE polymorphisms with POAG phenotypes including age at diagnosis, intraocular pressure (IOP) at diagnosis, highest IOP, cup-disc ratio, and visual field score was investigated by the Kruskal-Wallis test.

RESULTS

No significant difference was detected in the frequencies of APOE promoter polymorphisms between POAG patients and control subjects (P>0.0125). For the exon 4 polymorphism, when compared with control subjects, the frequency of epsilon 4 carriers was significantly lower in patients with NTG (P=0.008; odds ratio=0.36, 95% confidence interval=0.17, 0.79) but not in HTG (P=0.07). Compared with -219TT, the -219G carriers had a significant higher age at diagnosis (P=0.0046). No significant association was found between other APOE polymorphisms and POAG phenotypes (P>0.07).

CONCLUSIONS

Our findings suggest that the APOE epsilon 4 allele confers a protective effect against NTG, whereas the APOE promoter polymorphisms do not contribute to POAG risk. However, the APOE -219G carriers tended to have later-onset POAG.

Commonalities between genetics of cardiovascular disease and neurodegenerative disorders

PURPOSE OF REVIEW

Numerous epidemiological and clinical data suggest that neurodegenerative disorders, such as Alzheimer's disease, may be related directly or indirectly to cardiovascular risk. Genetic studies have demonstrated that they share at least one common susceptibility gene, encoding apolipoprotein E, a modulator of cardiac risk and of cognitive impairment. Several studies have suggested that other genes involved in the development of cardiovascular diseases may be involved. Previous studies indicated that additional genes contribute to Alzheimer's disease, in particular to the sporadic, more common late-onset form. In this review, the authors focus on recent findings concerning the modulation of the risk of Alzheimer's disease by genes also involved in the development of cardiovascular diseases.

RECENT FINDINGS

The intensive search conducted in the past year gave rise to many publications, more than half of which were related to genes common to cardiovascular and neurodegenerative disorders. The majority of the genes studied are involved in cholesterol metabolism, hypertension, lipid oxidation and detoxication, or inflammatory processes.

SUMMARY

In the past year, approximately 100 studies concerning the genetics of Alzheimer's disease were published around the world. Results suggest that the risk of Alzheimer's disease is modulated by various genes encoding proteins involved in cholesterol metabolism, in the detoxication of lipoprotein oxidation or encoding cytokines.