The Association between Sporadic Alzheimer's Disease and the Human ABCA1 and APOE Gene Polymorphisms in Iranian Population

Background: Apolipoprotein E (APOE), which its epsilon 4 allele has been reported as a risk factor in late onset Alzheimer's disease (AD), is the main cholesterol carrier in the brain. ATP-binding cassette transporter A1 (ABCA1) gene on chromosome 9, which has been known by genome-wide AD linkage study, has an important role in cellular cholesterol efflux. This study determines the association between sporadic AD and the human ABCA1 and APOE gene polymorphisms in Iranian population. Methods: 154 AD cases and 162 control subjects from Iranian population were genotyped for APOE genotypes and ABCA1 polymorphism (R219K). Results: The frequency of epsilon 2 epsilon 3 genotype was higher in control subjects comparing AD patients but was not significant (13% versus 5.8%) and epsilon 3 epsilon 4 genotype frequency was significantly higher in AD cases comparing with control subjects. APOE-epsilon 2 allele frequency in cases was lower than control subjects but this difference was not significant (4.5% versus 8%). Individuals carrying epsilon 4 allele, developed AD 6.5 times more than non-carriers (OR=6.52, 95%CI=2.63-16.17). There was no significant association between ABCA1 polymorphism and AD. Conclusion: Unlike other studies, R219K polymorphism was not dependent on gender and APOE-epsilon 4 allele and there was no association between APOE and ABCA1 in AD patients compared to controls.