Alpha-1 antichymotrypsin and alpha-2 macroglobulin gene polymorphisms are not associated with Korean late-onset Alzheimer's disease

Alpha 2-Macroglobulin Polymorphisms and Susceptibility to Alzheimer's Disease: A Comprehensive Meta-Analysis Based on 62 Studies

Background

The relationship between alpha 2-macroglobulin (A2M) gene and Alzheimer's disease (AD) has been widely studied across populations; however, the results are inconsistent.

Objective

This study aimed to evaluate the association of A2M gene with AD by the application of meta-analysis.

Methods

Relevant studies were identified by comprehensive searches. The quality of each study was assessed using the Newcastle-Ottawa Scale. Allele and genotype frequencies were extracted from each of the included studies. Odds ratio (OR) with corresponding 95% confidence intervals (CI) was calculated using a random-effects or fixed-effects model. The Cochran Q statistic and I2 metric was used to evaluate heterogeneity, and Egger's test and Funnel plot were used to assess publication bias.

Results

A total of 62 studies were identified and included in the current meta-analysis. The G allele of rs226380 reduced AD risk (OR: 0.64, 95% CI: 0.47-0.87, pFDR = 0.012), but carrier with the TT genotype was more likely to develop AD in Asian populations (OR: 1.56, 95% CI: 1.12-2.19, pFDR = 0.0135). The V allele of the A2M-I/V (rs669) increased susceptibility to AD in female population (OR, 95% CI: 2.15, 1.38-3.35, pFDR = 0.0024); however, the II genotype could be a protective factor in these populations (OR, 95% CI: 0.43, 0.26-0.73, pFDR = 0.003). Sensitivity analyses confirmed the reliability of the original results.

Conclusions

Existing evidence indicate that A2M single nucleotide polymorphisms (SNPs) may be associated with AD risk in sub-populations. Future studies with larger sample sizes will be necessary to confirm the results.

Polymorphic SERPINA3 prolongs oligomeric state of amyloid beta

Molecular chaperon SERPINA3 colocalizes with accumulated amyloid peptide in Alzheimer’s disease (AD) patient’s brain. From the QTL analysis, we narrowed down Serpina3 with two SNPs in senescence-accelerated mouse prone (SAMP) 8 strain. Our study showed SAMP8 type Serpina3 prolonged retention of oligomeric Aβ 42 for longer duration (72 hr) while observing under transmission electron microscope (TEM). From Western blot results, we confirmed presence of Aβ 42 oligomeric forms (trimers, tetramers) were maintained for longer duration only in the presences of SAMP8 type Serpina3. Using SH-SY5Y neuroblastoma cell line, we observed until 36 hr preincubated Aβ 42 with SAMP8 type Serpina3 caused neuronal cell death compared to 12 hr preincubated Aβ 42 with SAMR1 or JF1 type Serpina3 proteins. Similar results were found by extending this study to analyze the effect of polymorphism of SERPINA3 gene of the Japanese SNP database for geriatric research (JG-SNP). We observed that polymorphic SERPINA3 I308T (rs142398813) prolonged toxic oligomeric Aβ 42 forms till 48 hr in comparison to the presence wild type SERPINA3 protein, resulting neuronal cell death. From this study, we first clarified pathogenic regulatory role of polymorphic SERPINA3 in neurodegeneration.

Meta-analyses of 8 polymorphisms associated with the risk of the Alzheimer's disease

Aims

The aim of this study was to evaluate the combined contribution of 8 polymorphisms to the risk of Alzheimer's disease (AD).

Methods

Through a comprehensive literature search for genetic variants involved in the AD association study, we harvested a total of 6 genes (8 polymorphisms) for the current meta-analyses. These genes consisted of A2M (5bp I/D and V1000I), ABCA2 (rs908832), CHAT (1882G >A, 2384G >A), COMT (Val158Met), HTR6 (267C >T) and LPL (Ser447Ter).

Results

A total of 33 studies among 9,453 cases and 10,833 controls were retrieved for the meta-analyses of 8 genetic variants. It was showed that A2M V1000I (odd ratio (OR) = 1.26, 95% confidence interval (CI) = 1.07–1.49, P = 0.007), rs908832 allele of ABCA2 (OR = 1.55, 95% CI = 1.12–2.16, P = 0.009), 2384G >A of CHAT (OR = 1.22, 95% CI = 1.00–1.49, P = 0.05) and Ser447Ter of LPL in the Northern-American population (OR = 0.56, 95% CI = 0.35–0.91, P = 0.02) were significantly associated with the risk of AD. No association was found between the rest of the 5 polymorphisms and the risk of AD.

Conclusion

Our results showed that A2M V1000I polymorphism in German, Korean, Chinese, Spanish, Italian and Polish populations, rs90883 of ABCA2 gene in French, American, Swiss, Greek and Japanese populations, 2384G >A of CHAT gene in British and Korean populations and LPL Ser447Ter in the Northern-American population were associated with the risk of AD.

Association between α1-antichymotrypsin signal peptide -15A/T polymorphism and the risk of Alzheimer's disease: a meta-analysis

No consensus has been recently reached at the relationship between the α1-antichymotrypsin (ACT) signal peptide -15A/T polymorphism and Alzheimer’s disease (AD) risk. Thus, our study aimed to better assess this association by performing a meta-analysis, including 4,212 cases and 4,039 controls from 29 studies. Odds ratios (ORs) with the 95% confidence interval (CI) were used to assess the strength of relationship between ACT -15A/T polymorphism and AD risk. Overall, a borderline statistically significant association was detected under recessive model comparison in all subjects (AA vs. AT+TT: OR 1.12, 95% CI 1.01-1.25, P = 0.04). But in subgroup analysis by ethnicity, no significant association was found in Caucasians, Asians, or Africans. Moreover, after exclusion of one study which affect the heterogeneity, the ACT A allele and AA genotype were statistically associated with late-onset AD (LOAD) risk (AA vs. TT: OR 1.25, 95% CI 1.06-1.48, P = 0.007, A vs. T: OR 1.12, 95% CI 1.03-1.21, P = 0.008), especially in Caucasians. In conclusion, our study suggests that the common α1-antichymotrypsin signal peptide -15A/T polymorphism may not be a major risk factor for AD. However, the polymorphism is capable of increasing LOAD risk.

Identification of PSEN1 and APP gene mutations in Korean patients with early-onset Alzheimer's disease

Although mutations in three genes, amyloid precursor protein (APP), presenilin 1 (PSEN1), and presenilin 2 (PSEN2), have been identified as genetic causes of early-onset Alzheimer s disease (EOAD), there has been a single report on a PSEN1 mutation in Koreans. In the present study, we performed a genetic analysis of six Korean patients with EOAD. Direct sequencing analysis of the APP, PSEN1 and PSEN2 genes revealed two different mutations of the PSEN1 gene (G206S and M233T) and one mutation of the APP gene (V715M) in three patients with age-at-onset of 34, 35, and 42 yr, respectively. In addition, two patients with age-at-onset of 55 and 62 yr, respectively, were homozygous for APOE epsilon 4 allele. One woman had no genetic alterations. These findings suggest that PSEN1 and APP gene mutations may not be uncommon in Korean patients with EOAD and that genetic analysis should be provided to EOAD patients not only for the identification of their genetic causes but also for the appropriate genetic counseling.

Meta-analysis of genetic variability in the beta-amyloid production, aggregation and degradation metabolic pathways and the risk of Alzheimer's disease

BACKGROUND

Variants in genes encoding enzymes involved in production, aggregation or degradation of beta-amyloid are potential risk factors for sporadic Alzheimer's disease (AD).

METHODS

Meta-analyses on AD association with BACE1 exon 5, BACE1 intron 5, FE65 intron 13, CYP46 intron 2, alpha(1)-antichymotrypsine Ala17Thr, bleomycin hydrolase I443V, lectin-like oxidized low-density lipoprotein receptor (OLR1) 3'-UTR (+1071) and (+1073), and very-low-density lipoprotein receptor (VLDLR) 5'-UTR (CGG-repeat) polymorphisms.

RESULTS

In BACE1 exon 5, genotype CC+CT acts as a protective factor in Apolipoprotein E (ApoE) epsilon 4 carriers [odds ratio (OR) = 0.57; 95% confidence interval (CI): 0.38-0.88], and as a risk factor in ApoE epsilon 4 non-carriers (OR = 1.33; 95% CI: 1.00-1.78). OLR1 3'-UTR (+1073) allele C is associated with increased risk (OR = 1.23; 95% CI: 1.01-1.50). VLDLR 5'-UTR genotype 2 is associated with increased risk (OR = 1.70; 95% CI: 1.09-2.63) in the Asian population and is protective (OR = 0.48; 95% CI: 0.26-0.86) in the non-Asian population. Other studied polymorphisms are not associated with AD.

CONCLUSIONS

The overall impact on AD risk of the genes for which meta-analyses are now available is rather limited. Additional meta-analyses of other different genes encoding for A beta production, aggregation and degradation mediators might help in determining the risk profile for AD.

The genetic association between alpha-2-macroglobulin (A2M) gene deletion polymorphism and low serum A2M concentration in overweight/obese Thais

The study subjects were 192 overweight and obese Thais (BMI > 25.00 kg/m2), and 103 Thai controls (BMI = 18.50-24.99 kg/m2), whose ages ranged from 18-60 years. All subjects were evaluated for serum Alpha-2-macroglobulin (A2M), globulin, albumin concentration, and polymorphic variation in the A2M gene. Serum A2M and albumin were significantly lower in the overweight/obese group (P < 0.05). For the overweight/obese and control group, the median ages were 38 and 37 years, serum A2M 200.2; 252.0 (mg/L), albumin 4.4; 4.5 (g/dL), and globulin 3.0; 2.95 (g/dL), respectively. A2M deletion polymorphism genotyping showed no association between A2M deletion polymorphism and the two groupings. At serum A2M concentration < 250 mg/L, there was no relationship between A2M deletion polymorphism and age. Serum A2M had a significant negative correlation with age in all subjects (R = 0.09, P < 0.05). The results did not support the hypothesis that A2M deletion polymorphism is associated with a low A2M concentration in overweight/obese subjects. However, serum A2M had a significant negative correlation with age; serum A2M can possibly be used to indicate the aging of cells in vivo, including the brain. Further studies are needed to investigate other A2M genes located on chromosome 12 to prove A2M gene polymorphism's association with low serum A2M and aging.

Candidate genes for late-onset Alzheimer's disease: Focus on chromosome 12

In recent years, there was an increasing interest on candidate genes may play an important role in the development of Alzheimer's disease (AD). Several genome wide screens have undertaken so far or expanded recently, and suggested a number of genomic areas that may contain novel susceptibility genes for AD, in particular most compelling have been the findings on chromosome 12. Polymorphisms in different susceptibility genes on chromosome 12 (A2M, LRP1, CP2 and OLR1) are now being suggested as possible genetic markers for increased risk of developing AD. However, many of these studies are controversial and have shown conflicting results. Thus far, the search for the chromosome 12 Alzheimer's gene must continue and there are several other genes in this region that we are looking at. In this article, we focused on the current knowledge of the genetics of familial late-onset and sporadic AD linked to the chromosome 12, and the future search for other candidate genes.

Current knowledge of chromosome 12 susceptibility genes for late-onset Alzheimer's disease

In the last decade, it has become more apparent the important role genes play in the development of late-onset Alzheimer's disease (AD). Great efforts, involving human genome scans and candidate gene studies, have been given towards identifying susceptibility genes for AD. A number of regions on different chromosomes have been reported to demonstrate linkage for AD. Of these, findings on chromosome 12 are some of the most compelling. Worldwide genetic association studies pre-dating and subsequent to recent linkage studies have identified and focused upon a number of genes that map to the areas of reported linkage on chromosome 12, however, analyses of those genes studied to date, on the whole, remain inconclusive and ambiguous. This paper reviews studies that have provided evidence of linkage for AD on chromosome 12 and in turn discusses the work conducted to date on candidate genes that have been identified and map to the chromosome 12 regions of interest.

Genetic studies of A2M and BACE1 genes in Chinese Han Alzheimer??s disease patients

We investigated insertion (Ins)/deletion(Del) polymorphism in alpha-2-macroglobulin (A2M), G/C variant in the beta-site amyloid precursor protein-cleaving enzyme 1 (BACE1) and apolipoprotein E (APOE) gene epsilon2/epsilon3/epsilon4 polymorphism in 387 Chinese Han ethnic patients with Alzheimer's disease and healthy study participants. After stratification for APOEepsilon4 status, only the BACE1-G allele with APOEepsilon4 was significantly associated with Alzheimer's disease. Through meta-analysis of the Del or G allele by pooling Asian studies, only BACE1-G allele appeared to increase risk of developing Alzheimer's disease. Through combination-analysis of the data about the A2M-I/D and the A2M-Ile1000Val variants, the A2M gene was suggested to be associated with Alzheimer's disease.

Joint analysis of candidate genes related to Alzheimer's disease in a Spanish population

BACKGROUND

Besides the repeated association between the epsilon 4 allele of the apolipoprotein E and Alzheimer's disease, several candidate genes have been analysed with inconsistent results. Most of these studies have examined only one or two polymorphisms in a defined population, which provides a lack of a general view of the Alzheimer's disease genetic component.

OBJECTIVE

To overcome this limitation, nine polymorphisms in seven different candidate genes (A2M, ACT, APOE, APP, BH, HSP70-2, and IL1-A) were genotyped.

METHODS

The sample comprised 112 Alzheimer's disease patients and 89 controls from Spain. Since haplotype reconstruction may add power to association studies, we also tested for linkage disequilibrium within the A2M and APOE genes.

RESULTS

Except for the APOE gene, allele and genotype frequencies were not different between cases and controls, even when stratifying for the APOE genotype.

CONCLUSION

The present results suggest that future association studies should be performed using a battery of polymorphisms in different and new candidate genes, taking into account the linkage disequilibrium in the region.

Distributions of ACE and APOE polymorphisms and their relations with dementia status in Korean centenarians

BACKGROUND

Genetic polymorphisms of angiotensin-converting enzyme (ACE) and apolipoprotein E (APOE) have been reported to be associated with human longevity and dementia in the elderly. However, whether such putative longevity genes exert the same effects on different ethnic groups living in different environments is not well known.

METHODS

We investigated the distributions of the ACE and APOE genotypes and their relations with dementia status in Korean centenarians by cross-sectional study. A total of 103 centenarians (13 men and 90 women, mean age 102.4 +/- 2.6 years) were included in this study. The allele frequencies of the genes were compared with those of two control groups: 7232 apparently healthy adults (4100 men and 3132 women) of mean age 48.5 +/- 9.6 years for the ACE genotyping, and 6435 adults (5008 men and 1427 women) of mean age 50.7 +/- 7.9 years for the APOE genotyping. The dementia status of the centenarians was assessed by clinical psychologist using the Clinical Dementia Rating (CDR) score.

RESULTS

The frequencies of genotypes and alleles of the ACE and APOE genes of the centenarians were not significantly different from those of the control groups. There was a lack of association between presence of the D allele on the ACE gene and dementia status. However, the frequency of the epsilon4 allele of the APOE gene was significantly higher in centenarians with dementia than in centenarians without definitive dementia (9.1% versus 1.5%, p <.05).

CONCLUSIONS

These results suggest that neither the ACE nor the APOE gene is significantly associated with longevity in the Korean population, but that the APOE epsilon4 allele is still related with dementia even at age 100 and older.