Positive association of a Sirt1 variant and parameters of oxidative stress on Alzheimer's disease.

Alzheimer's disease (AD) is a complex neurodegenerative disorder and the most common type of dementia in the elderly. Although its cause is not completely known, several studies suggest that oxidative stress plays an important role in the etiology of this disease. The SIRT1 and SOD2 proteins are linked to pathways that may impair oxidative stress. In this study, we analyzed the association between polymorphisms in these genes and in the APOE gene, through RT-PCR, as well as between environmental factors and the risk of AD. Additionally, the thiobarbituric acid reactive substance assay was performed to estimate the plasma level of malondialdehyde (MDA), a biomarker of lipid peroxidation. Furthermore, some cytogenetic studies indicate that cells of AD patients show increased chromosomal damage; thus, we performed the micronucleus cytome assay to assess cytogenetic damage in AD patients. As expected, the APOE polymorphisms were found to be highly associated with AD. Additionally, the CT genotype of the SIRT1 gene showed a positive association with the disease. The frequencies of genomic damage (micronucleus, buds, nucleoplasmic bridges and binucleated cells), the presence of cell death biomarkers (condensed chromatin, karyorrhexis and pyknosis), and the plasma level of MDA were significantly greater in AD patients than in controls. Our results support the hypothesis that AD is a condition with increased oxidative stress and genomic instability, which may contribute to the neurodegeneration in AD.

The combined risk effect among BIN1, CLU, and APOE genes in Alzheimer's disease.

Genome-wide associations studies (GWAS) are detecting new variants associated with late-onset of Alzheimer's disease (LOAD), a multifactorial neurodegenerative disorder. The variants rs744373 BIN1, rs11136000 CLU and rs3764650 ABCA7 uncovered by GWAS led to different AD pathways, such as metabolism, trafficking and endocytosis of lipids and inflammation. However, most of the association studies did not replicate these variants with significance. This could be due to a small power effect evident when these variants are tested independently with LOAD. Therefore, we aimed to investigate whether the combination of different variants would additively modify the risk of association with LOAD that is observed in GWAS. We performed an association study testing pairwise variants in metabolism, trafficking and endocytosis of lipid (rs429358 and rs7412 APOE, rs744373 BIN1, rs3764650 ABCA7 and rs11136000 CLU) pathways with LOAD in samples from southeastern Brazil. Our data suggest a risk effect for LOAD between APOE with CLU and APOE with BIN1 genes.

Updated Meta-Analysis of BIN1, CR1, MS4A6A, CLU, and ABCA7 Variants in Alzheimer's Disease.

Genome-wide association studies (GWAS) have associated several genetic variants with late-onset Alzheimer's disease (LOAD), a neurodegenerative disease. Among those, rs3764650 ABCA7, rs6656401 CR1, and rs744373 BIN1 were associated as risk factors for LOAD, while rs11136000 CLU and rs610932 MS4A6A were protective. Recently, several case-control studies have investigated the association of these polymorphisms with AD. However, not all meta-analyses analyzed these variants across different ethnic groups. Therefore, we performed an updated meta-analysis of rs3764650 ABCA7, rs6656401 CR1, rs744373 BIN1, rs11136000 CLU, and rs610932 MS4A6A variants associated with LOAD, considering different ethnic populations. We utilized samples from 38 articles, comprising a total of 24,771 patients and 35,324 controls obtained through the PubMed database. Odds ratios (ORs) with 95% confidence intervals (CI) for polymorphisms were calculated by allelic comparison as an additive genetic model. We validated the risk for LOAD with BIN1 (rs744373), CR1 (rs6656401), and ABCA7 (rs376465), as well as the protective association for MS4A6A (rs610932) and CLU (rs11136000) variants.