Molecular Epidemiological Study On Alox5ap Gene And Risk Of Stroke In Eastern Chinese Han Population

Stroke is an important health problem worldwide, and it is still a leading cause of mortality and morbidity in Chinese. It has been established that the underlying pathogenesis is likely to be mediated by both genetic and environmental risk factors.Leukotrienes has play an important role for the progression of atherosclerosis, which is a chronic inflammatory disease that underlies the pathogenesis of cardiovascular disease and stroke . Whereas the 5-lipoxygenase activating protein (FLAP) producted by ALOX5AP gene is a regulator in the biosynthesis of proinflammatory leukotrienes. The FLAP was required for leukotriene biosynthesis by ALOX5 (5-lipoxygenase), anchored ALOX5 to the membrane, bind arachidonic acid, and could play an essential role in the transfer of arachidonic acid to ALOX5.The human ALOX5AP gene is mapped to chromosome 13q12.3 and consists of five exons. Based on its important physiological functions, ALOX5AP can be considered a good candidate gene for stroke risk. To date, the association between genetic variations in the ALOX5AP gene and risk of stroke in Eastern Chinese population has not been reported.Haplotype-based association testing offers several advantages over the standard"one-SNP-at-a-time"approach. Because many single-nucleotide polymorphisms (SNPs) are in linkage disequilibrium (LD) with other nearby SNPs in the genome, it is feasible to select a small number of genetic markers, also called tagging single-nucleotide polymorphisms (tSNPs), to capture the common variants of a gene. The use of tSNPs is expected to increase power relative to single-SNP approaches because tSNPs provide information about nearby SNPs that are not genotyped. The international HapMap Project is a great resource that provides genome-wide data to support such tSNP analyses. In the present study, we selected 13 tSNPs from the data for Chinese in the HapMap to investigate the association between common genetic variants across ALOX5AP sequence and risk of stroke in our ongoing hospital-based case–control study in an Eastern Chinese Han population.[Objective] The aim of the present study is to investigate the association between the ALOX5AP gene polymorphism and stroke in Eastern Chinese in a haplotype-based analysis.[Methods] We recruited only patients with 1 of 3 subtypes of stroke: cerebral thrombosis(thrombosis), lacunar infarction(lacunar), and intracerebral hemorrhage(hemorrhage). Those cases who had other types of stroke (transient ischemic attack, subarachnoid hemorrhage, embolic brain infarction, brain tumors, and cerebrovascular malformation) and severe systemic diseases (collagenosis, endocrine, and metabolic disease (except for diabetes mellitus, DM), inflammation, neoplastic, or renal diseases) were excluded. Diagnosis of stroke was based on the results of strict neurological examination—CT, MRI, or both—according to the International Classification of Diseases, Ninth Revision (ICD-9). Controls were selected simultaneously from the same demographic area and frequency-matched to the cases by age, sex. We conducted a comprehensive association study of 507 stroke patients and 510 controls to assess the associations between the ALOX5AP tagging single-nucleotide polymorphisms (tSNPs) and stroke risk. Genotyping was performed by using the PCR-RFLP assay.[Results]1.Basic characteristics of the subjectsThe mean age was 68.9±10.9 years for the cases and 67.6±9.7 years for the controls (P= 0.074); (61.3%) cases and (66.1%) controls were male (P=0.116). There was no significant difference in the distribution of age and sex between the cases and controls. As expected, cases had a higher prevalence of conventional risk factors for vascular disease, including BMI, family history of CVD, self-history of CAD, hypertension and DM, higher blood pressure, glucose, TG, TC and lower level of HDL cholesterol. However, some risk factors did not differ. For example, smoking and alcohol intake were not statistically significant (P=0.354 and P=0.063, respectively) between our two groups. Interestingly, we found either white blood count or neutrophil ratio in first time test of blood routine levels were significantly higher in overall stroke cases than in controls (P<0.001, both).2.Individual tSNP association analysisNone of the 13 tSNPs had significant different allele frequencies between the cases and controls. The genotype distributions of the ALOX5AP polymorphisms in cases and controls are summarized in Table. The single-SNP analysis indicated that the genotype frequency of SNP1 SG13S106-rs9579646 was significantly different between the overall cases and controls (P=0.034). Multivariate logistic regression analyses revealed that a marginal decreased risk was associated with the AG genotype (adjusted OR, 0.66; 95% CI, 0.45-0.97), compared with the wildtype AA.3.Haplotype analysisIn these within-block regions of ALOX5AP with a high LD and limited haplotype diversity, there might be haplotype effects among these SNPs in each block. Because we could not replicate associations with HapA, we expected that there might be other unidentified haplotypes in ALOX5AP that confer risk to stroke in our population. Therefore, haplotype analysis was performed in each haplotype block. We formed three haplotype structures of our data. Block1 including SNP1, SNP2, block2 including SNP5, SNP6, and block 3 including SNP8, SNP10, SNP11, SNP12, SNP13, and other tSNPs were not part of the haplotype due to shortage in linkage disequilibrium with the other tSNPs. In block 3, haplotypes with a frequency <0.05 in both the cases and controls were pooled into a single"other"haplotype category, and in each block, the haplotypes were analyzed with Haplo. stats. As shown in Table5. Overall, The risk of stroke was decreased among individuals carrying the haplotype"AA"in block 2 (OR, 0.66; 95% CI, 0.46-0.95), as compared with those carrying the most common haplotype"TA". Interestingly, the only difference between the protection haplotype"AA"and the most common haplotype"TA"was the SNP5 rs10507391A allele, which had been part of the Icelandic at-risk haplotype suggesting that the SNP5 rs10507391T allele ( wild allele ) may be the risk allele for stroke conversely, which was not showed in the individual SNP association analysis.[Conclusion] Our findings suggested that rs9579646 polymorphism may contribute to stroke susceptibility in Eastern China. Haplotype"AA", constructed by rs10507391A and rs12429692A may contribute to stroke susceptibility in Eastern China. Racial differences in the frequencies of allele and genotypes as well as LD structure may account partially for the different association findings between studies. Larger studies and functional studies are needed to confirm our findings.