Effect of APOE genotype and promoter polymorphism on risk of Alzheimer's disease

OBJECTIVE: To verify the association between APOE gene promoter polymorphisms and the development of AD and to determine whether the effect of promoter polymorphisms on AD is independent of the APOE epsilon4 allele. BACKGROUND: Three polymorphisms in the APOE promoter have been shown to modify APOE expression in vitro. Several studies have suggested that these polymorphisms may also modulate risk for AD, either independently or by modifying the effect of the APOE coding polymorphism. METHODS: The authors analyzed allele and genotype distributions for APOE and all three known APOE promoter polymorphisms (-491 A/T, -427 T/C, and -219 G/T) in a study group consisting of 237 subjects with AD and 274 age-matched controls. They then used log-linear and logistic regression analyses to test for possible interactions between APOE genotype and the promoter polymorphisms on risk of AD. CONCLUSION: A strong association between the APOE epsilon 4 allele and AD was detected regardless of promoter polymorphism status. In addition, the -491 AA genotype appears to be an independent genetic risk factor for AD. The -427 T/C polymorphism and the -219 T/G polymorphism were not directly associated with AD.     

Polymorphisms in the apolipoprotein E (APOE) gene in gerontopsychiatric patients

Two recently described polymorphisms in the promoter region of the apolipoprotein E (APOE), the −491A7T and Th1/E47csT/G polymorphism, have been suggested to be associated with an increased risk for Alzheimer's disease (AD) independent from the APOE ɛ4 carrier status. We studied the association between the APOE ɛ4 polymorphism and the −491A/T and Th1E47csT/G polymorphisms in a sample of 118 healthy, non-demented controls and 239 consecutively recruited gerontopsychiatric patients diagnosed as: Alzheimer's disease (N = 89), age mild cognitive impairment (N = 32), memory complainers without any congitive deficit (N = 54) and depression/other psychiatric disorders (N = 64), to test whether the investigated polymorphisms have a high enough selectivity and specificity to distinguish between the different gerontopsychiatric disorders to differentiate AD genetically from other forms of dementia, respectively. Also a possible association with the APOE ɛ4 polymorphism was examined. We found a statistically significant association between the APOE ɛ4 allele and Alzheimer's disease (p = 0.0001) and age associated memory impairment (p = 0.006). Our study failed to show an association between the promoter polymorphisms −491A/T and Th1E47csT/G in the APOE gene and gerontopsychiatric disorders either alone or in relationship to the APOE ɛ4 polymorphism. However, if we combine our results with three previous published positive reports there seems to be an association between the −491A/T polymorphism and AD, though its size is less than found in the original publication. Accepted: 3 February 2001     

Cognitive impairment in patients with multiple sclerosis: association with the APOE gene and promoter polymorphisms

BACKGROUND: Studies examining the epsilon4 allele of the APOE gene as a factor affecting the severity of multiple sclerosis (MS) have yielded conflicting results. The focus of these studies on physical disability to the neglect of cognitive impairment is surprising in light of the associations between the epsilon4 allele and other dementia conditions. Only two studies examine the relationship between the epsilon4 allele and cognitive impairment. METHODS: A neuropsychological test battery was administered to 263 MS patients, and their current disability status was evaluated. Genotypes were determined for APOE epsilon and for two promoter region polymorphisms (-219 G/T and -491 A/T). RESULTS: Although effects were generally weak, female patients with the -491 AA genotype had a later age of disease onset, lower disability scores, and somewhat higher scores on the cognitive battery. Male patients with the epsilon2 allele had lower disability and higher scores on the cognitive battery. The epsilon4 allele was not related to physical disability, and there was no difference between epsilon4+ and epsilon4--patients in overall cognitive performance. However, when patients with severe cognitive impairment were identified, a greater proportion (52%) of these patients had the epsilon4 allele than those in the unimpaired group (27%). CONCLUSION: An association with the epsilon4 allele was evident in this study, but only in cases of severe cognitive impairment.     

Polymorphisms of APOE and LRP genes in Brazilian individuals with Alzheimer disease

Alzheimer disease (AD) is the most frequent cause of dementia in Western countries. Putative genetic risk factors for AD are polymorphisms in the apolipoprotein E (APOE) gene and in the low-density lipoprotein receptor-related protein (LRP) gene. Our objective was to investigate the role of the APOE coding region polymorphisms epsilon 2, epsilon 3, and epsilon 4 and APOE promoter variants A/T at position -491 and G/T at -219, as well as LRP polymorphism C/T, as risk factors for AD in Brazilian individuals. One hundred and twenty patients with probable AD, along with 120 controls were analyzed. A significant difference between patients and controls for epsilon 4 alleles was observed: frequency of this allele in AD was 0.31, and 0.10 in controls. Individuals with 2 epsilon 4 alleles had a higher risk for AD than subjects with only 1 such allele; presence of 1 epsilon 2 allele proved protective. The presence of the T allele of the -219 polymorphism was also associated with an increased risk of AD, but this polymorphism is in linkage disequilibrium with APOE epsilon polymorphisms. No significant differences between patients and controls were observed for -491 APOE or LRP polymorphisms. In this Brazilian population, both the epsilon 4 allele and T -219 polymorphism were associated with an increased risk for AD.     

No evidence of association between apolipoprotein E gene regulatory region polymorphism and Alzheimer's disease in Japanese

The reported association between -491 A/T polymorphism in the regulatory region of the apolipoprotein E gene (APOE) and increased risk for Alzheimer's disease (AD) is controversial: Studies of different racial and ethnic populations have found both positive and negative associations. Examination of -491 A/T polymorphism in 216 patients with sporadic AD and 157 age- and gender-matched controls from the Japanese population revealed that, in contrast to findings for Caucasian populations, the -491 T allele, but not the A allele, was significantly more prevalent in patients with AD than in controls. This difference disappeared when the subjects were stratified by the gene dose of the APOE epsilon4 allele. Moreover, logistic regression analysis, controlling for age, sex, and the presence of the APOE epsilon4 allele, showed no association between the -491 polymorphism and AD. These results suggest that -491 polymorphism does not independently confer susceptibility to AD, but that this polymorphism is in partial linkage disequilibrium with the APOE epsilon2/3/4 polymorphism.     

Contribution of APOE promoter polymorphisms to Alzheimer's disease risk

OBJECTIVE: To determine whether the effects of APOE promoter polymorphisms on AD are independent of the APOE-epsilon4 allele. BACKGROUND: Recently, the -491 A-->T and -219 G-->T polymorphisms located in the APOE promoter have been suggested to be risk factors for AD. However, the effects of these polymorphisms have not always been reproduced in case-control studies, possibly because of the strong linkage disequilibrium existing at this locus or the characteristics of the populations studied. METHODS: Data collection was performed from six independent samples (1,732 patients with AD and 1,926 control subjects) genotyped for APOE exon 4 and the two APOE promoter polymorphisms. The risks associated with the APOE polymorphisms for developing AD were estimated using logistic regression procedures and calculation of odds ratios with 95% CI adjusted by age, sex, and collection center. Independence of the APOE promoter polymorphisms was tested by stratification for APOE-epsilon4 and tertile design was used for age stratification. RESULTS: The independence of the -491 AA genotype was observed in the whole sample whereas the independence of the -219 TT genotype was observed only in the oldest population. CONCLUSION: The -491 and -219 APOE promoter polymorphisms incur risk for AD in addition to risk associated with the APOE-epsilon4 allele, with age accentuating the effect of the -219 TT genotype. Because these polymorphisms appear to influence apoE levels, these results suggest that APOE expression is an important determinant of AD pathogenesis.     

The -491AA polymorphism in the APOE gene is associated with increased plasma apoE levels in Alzheimer's disease

Recent evidence suggests that a polymorphism in the regulatory region of the apolipoprotein E gene (APOE) is associated with an increased risk for developing Alzheimer's disease (AD) independent of that conveyed by the epsilon4 allele of APOE. Previous work by our group indicated that plasma apolipoprotein E (apoE) levels were elevated in AD, raising the possibility that the -491 genotype might modify AD risk by increasing expression of the APOE gene. In a total of 638 individuals the -491AA genotype was significantly associated with AD (P < 0.005) while the TT genotype was associated with controls (P < 0.005). In 138 individuals the AA genotype showed significantly higher plasma apoE levels, independent of epsilon4 and AD status (P < 0.01) as well as within control and AD groups (P < 0.05). Within the AD group the AA genotype showed increased apoE levels when compared to AA controls (P < 0.0001). These results suggest that the -491 AA genotype is associated with increased plasma apoE levels, providing a potential basis for elucidating how that genotype increases the risk for developing AD.     

Apolipoprotein E genotype does not influence the progression of multiple sclerosis

Objective: To investigate the association between apolipoprotein E (APOE) polymorphisms and the progression of MS.Methods: We investigated 428 subjects affected by clinically defined MS, with a disease duration of at least three years. We collected data concerning the age at onset of MS, clinical type, disease duration and disability according to the expanded disability status scale (EDSS). We also calculated the progression index (PI) to evaluate disease progression. APOE genotyping and the –491 A/T polymorphism of the APOE promoter were determined.Results: No association was observed between the APOE 4 allele and clinical characteristics of our study population. We also investigated the –491 A/T APOE promoter polymorphism in 236 MS subjects and did not find any association between the –491 A/T polymorphism and the selected clinical variables.Conclusions: In our population the APOE 4 allele and the –491 A/T APOE promoter polymorphism are not associated with a more rapid course of MS.     

Promoter polymorphism (–491A/T) in the APOE gene of Finnish Alzheimer’s disease patients and control individuals

Apolipoprotein E (APOE) ɛ4 allele is a major risk factor for the development of Alzheimer’s disease (AD). It has been suggested that the quantitative expression of APOE alleles results from mutations in the promoter region of this gene. We studied the –491A/T promoter polymorphism and whether it is dependent on the APOE ɛ4 allele in clinic-based AD (n = 106) and community-based control (n = 123) samples. The –491A/T and APOE polymorphisms were analyzed using the polymerase chain reaction method and restriction fragment length polymorphism analysis. The APOE ɛ4 allele was strongly associated with AD when compared with controls, P < 0.001 (odds ratio 5.85, 95% CI 3.29– 10.41). The genotype distribution of the –491A/T polymorphism did not significantly differ between the study groups (P = 0.063), and the –491A allele was not associated with any significant risk in the AD group when compared to controls (odds ratio 1.82, 95% CI 0.95–3.49). However, haplotype estimation analysis indicated linkage disequilibrium between APOE –491A/T polymorphism and the APOE ɛ4 allele. Our findings confirm APOE polymorphism still to be the most efficient predictor of risk in AD. Received: 2 November 1998 Received in revised form: 28 January 1999 Accepted: 5 February 1999     

Cerebral β-amyloid deposition is augmented by the –491AA promoter polymorphism in non-demented elderly individuals bearing the apolipoprotein E ε4 allele

The apolipoprotein E epsilon4 allele (APOE, gene; apoE, protein) is widely accepted as a risk factor for Alzheimer's disease (AD). Our previous studies found that APOEepsilon4 promotes AD pathogenesis by fostering the early deposition of the amyloidogenic peptide Abeta in the aging brain. Recent reports suggest that polymorphisms in the upstream promoter region of APOE differentially affect the production of apoE and also may have an important influence on the probability of developing AD. In this study, we asked whether APOE promoter -491 (A/T) variants interact with APOE polymorphisms to modulate the degree of beta-amyloid- and tau-related pathology in the medial temporal lobe of the non-demented elderly. Our results confirm that APOEepsilon4 is associated with increased formation of senile plaques, cerebrovascular amyloid, and neurofibrillary tangles in the medial temporal lobe. We also found that homozygosity for A at position -491 of the APOE promoter (-491AA) correlates with increased Abeta17-24 and Abeta42 deposition in APOEepsilon4-positive cases, but not in cases lacking the epsilon4 allele. In comparison, Abeta burden is significantly less in epsilon4 carriers with the -491AT and -491TT promoter allelotypes. There was no effect of -491 polymorphisms on Abeta40 deposition (which is relatively sparse in the non-demented elderly), on the number of activated microglia, or on the amount of neurofibrillary tangles. We conclude that the amyloidogenic effects of apoE4 are exacerbated by polymorphisms in the APOE promoter that enhance apoE production.     

Association of APOE promoter but not A2M polymorphisms with risk of developing Alzheimer's disease

The APOE4 allele is widely accepted as a major risk factor for late-onset Alzheimer's disease (AD). Recently, it has been reported that polymorphisms in the APOE promoter and in the alpha2-macroglobulin gene (A2M) are associated with AD. We have analyzed the distribution of APOE alleles, -219T/G APOE promoter polymorphism, and A2M/A2Mdel polymorphism in a large case-control study. Our results showed that APOE genotype was the only informative marker of AD risk contrary to -219T/G and A2M/A2Mdel polymorphism. In AD patients however, a strong linkage disequilibrium was observed between the T allele of -219T/G polymorphism and APOE4 allele. This result indicates that -219T/G APOE promoter polymorphism is a risk factor for AD by increasing the APOE4-associated risk.     

Gender-related effect of clinical and genetic variables on the cognitive impairment in multiple sclerosis

Abstract. Background: Cognitive impairment may occur at any time during the course of multiple sclerosis (MS), and it is often a major cause of disability in patients with the disease. The APOE-4 allele is the major known genetic risk factor for late onset familial and sporadic Alzheimers Disease (AD), and it seems to be implicated in cognitive decline in normal elderly persons. Objective: To investigate the clinical and genetic variables that can be associated with the cognitive decline in patients with MS. Methods: Five-hundred and three patients with clinically definite MS underwent a battery of neuropsychological tests and, according to the number of failed tests, were divided into cognitively normal and impaired. All patients were genotyped for APOE gene polymorphisms. Results: Fifty-six percent of MS patients showed, to different extents, cognitive impairment. Cognitive decline was predominant in men and was associated with disease duration, Kurtzke Expanded Disability Status Scale (EDSS) score, a low level of education, and, interestingly, the 4 allele of the APOE gene. By contrast, cognitive impairment in women was independent of any investigated variable. Conclusion: The findings demonstrate that clinical and genetic factors play a role in men affected by MS developing cognitive impairment.This work was supported in part by a grant from FISM (Federazione Italiana Sclerosi Multipla).     

Cytokine IL‐1 beta but not IL‐1 alpha promoter polymorphism is associated with Alzheimer disease in a population from the Canary Islands,Spain

Aims: Previous studies have reported the presence of low‐grade inflammation in Alzheimer disease (AD). Based on these data, our work attempts to investigate the effects of some promoter polymorphisms of pro‐inflammatory cytokines [interleukin (IL)‐1 alpha and IL‐1 beta] on AD. Patients and methods: A PCR‐RFLP technique was used to analyze the promoter polymorphisms of both IL‐1 alpha (?889 C/T) and IL‐1 beta (?511 C/T) and the APOE genotype from the DNA samples of 282 patients (according to NINCDS‐ADRDA criteria) and 312 control subjects. Results: (i) The risk of developing AD in our population was associated with the IL‐1 beta (?511 C/T) promoter polymorphism; (ii) such risk was independent of the risk factor allele in the APOE gene (APOE4); and (iii) the IL‐1 alpha promoter polymorphism (?889 C/T) was not associated with the disease. Conclusion: In our population, IL‐1 beta promoter polymorphism (?511 C/T) is an independent risk factor for AD.     

APOE is associated with age-of-onset, but not cognitive functioning, in late-life depression

OBJECTIVE: There is a recognized but poorly understood relationship between late-life depression (LLD) and progressive dementia. Both cognitive impairment co-occurring with LLD and a late age-of-onset of first lifetime depressive episode appear to be associated with subsequent progressive dementia. A history of major depression, especially when the first onset occurs in late-life, has been identified as a risk factor for Alzheimer's disease (AD). The major genetic risk factor for sporadic AD is carrying one or more apolipoprotein E4 (APOE4) alleles. We hypothesized that the association between LLD and dementia risk would be mediated by APOE4, specifically that APOE4 allele frequency would be associated with cognitive impairment and later age-of-depression-onset. We also predicted that APOE4 allele frequency would be increased among subjects with LLD. METHODS: We compared the distribution of APOE2, APOE3, and APOE4 alleles in groups of LLD (n=160), AD (n=568) and elderly control (EC; n=156) subjects. RESULTS: The allele distribution of the cognitively impaired LLD subgroup was not different from either the cognitively normal subgroup or the EC group but was different from the AD group. However, mean age-of-onset of depression in APOE4 carriers (51.4+/-20.7) was significantly lower than non-carriers (58.8+/-16.8). The allele distribution in LLD overall was significantly different from the AD but not the EC group. CONCLUSIONS: The finding that neither LLD, accompanying cognitive impairment, nor late age-of-onset was associated with an increased APOE4 allele frequency suggests that LLD acts as a risk factor for developing AD as well as non-AD dementia through mechanisms independent of APOE4. The unexpected finding that age-of-onset of LLD was significantly reduced in APOE4 carriers is similar to the association between APOE4 and age-of-onset in AD. Replication of the association of APOE4 with earlier age-of-depression-onset is indicated.     

APOE and APOC1 promoter polymorphisms and the risk of Alzheimer disease in African American and Caribbean Hispanic individuals

BACKGROUND: The APOE epsilon4 allele is a genetic risk factor for Alzheimer disease (AD), though the strength of the association varies by ethnic group. Polymorphisms in regulatory sequences of APOE have also been related to AD, but the effects are inconsistent across studies. METHODS: We examined the association between AD and variants in 3 APOE promoters and in the promoter of the adjacent APOC1 gene in African American and Caribbean Hispanic individuals. Polymorphisms tested were the -491A/T, -427T/C, and -219G/T (Th1/E47cs) in the APOE promoter and the HpaI variant in the APOC1 promoter. Using standard research criteria for AD, overall odds ratios were computed and repeated stratified by presence or absence of APOE epsilon4. RESULTS: The APOC1 HpaI+ variant was associated with AD in Caribbean Hispanic individuals, but strong linkage disequilibrium with the APOE epsilon4 allele indicated that this was not an independent effect. No promoter variant in APOE or APOC1 was associated with AD before or after adjusting for age, education, sex, and multiple comparisons. Estimated haplotypes including -219G/T, APOE, and APOC1 differed significantly in Caribbean Hispanic patients and controls but not in African American participants. This effect was primarily owing to the -219G/T-APOE haplotype, but we did not detect significant allele-specific differences in promoter activity comparing reporter constructs containing the APOE -219G and -219 T alleles. CONCLUSION: These findings exclude a strong or independent influence of APOE or APOC1 promoter polymorphisms on the variation in APOE-related risk of AD in African American and Caribbean Hispanic individuals.     

T102C and -1438 G/A polymorphisms of the 5-HT2A receptor gene in Turkish patients with obsessive-compulsive disorder.

OBJECTIVE: This study aimed to investigate the possible association between T102C and -1438 G/A polymorphism in the 5-HT2A receptor gene and susceptibility to and clinical features of obsessive-compulsive disorder (OCD). METHOD: Fifty-eight patients with OCD and 83 healthy controls were included in the study. All patients were interviewed and rated by Yale-Brown Obsessive-Compulsive Scale. T102C and -1438 G/A polymorphisms of 5-HT2A receptor gene were determined by PCR technique in DNAs of peripheral leucocytes. RESULTS: OCD patients and healthy controls did not show significant differences in genotype distribution for both polymorphisms investigated. We found that frequencies of the TT genotype for T102C polymorphism and the AA genotype for -1438 G/A polymorphism were significantly higher in patients with severe OCD compared to those with moderate or moderate-severe OCD. CONCLUSION: The -1438 G/A and T102C polymorphisms of the 5-HT2A receptor gene are not associated with an increased risk of OCD. Our data suggest that the TT genotype of T102C and the AA genotype of -1438 G/A polymorphism might be a factor in clinical severity of OCD.     

Apolipoprotein E polymorphisms and the risk of nonlesional temporal lobe epilepsy

PURPOSE: To evaluate whether the inheritance of the apolipoprotein E (ApoE) epsilon4 allele is a risk factor for nonlesional temporal lobe epilepsy (TLE), and to determine whether the newly described -491 A/T ApoE polymorphism may independently affect the risk of nonlesional TLE. METHODS: The study group consisted of 63 patients (35 women and 28 men; age at onset of epilepsy, 30.6 +/- 19.6 years; mean (+/-SD). All of them had received a diagnosis of nonlesional TLE after a detailed clinical, electroencephalographic, and brain magnetic resonance investigation. The ApoE polymorphisms were determined from blood samples by standard methods. The molecular study also was performed in 220 age- and sex-matched normal individuals. RESULTS: There were no differences between TLE patients and controls in either allelic or genotypic frequencies of the ApoE and -491A/T polymorphisms. Moreover, no effect of ApoE or -491A/T polymorphisms was found on the age at onset and severity of epilepsy. CONCLUSIONS: The allelic and genotypic frequencies of ApoE polymorphisms in Italian patients with nonlesional TLE are comparable to control values, indicating that ApoE polymorphisms are not a significant genetic risk factor for the occurrence of nonlesional TLE.