Analysis of apolipoprotein E genetic variation in patients with Alzheimer disease referred to Imam Reza Clinic, Rasht, Iran, in 2015

Background: Alzheimer disease (AD) is a progressive neurological degenerative disorder and the most common form of dementia. There are about 100 genes linked to AD including apolipoprotein E (ApoE). This gene exists in the form of three allele polymorphisms of ε(2), ε(3) and ε(4) and six genotypes of ε(2)ε(3), ε(2)ε(2), ε(3)ε(3), ε(2)ε(4), ε(3)ε(4), and ε(4)ε(4). We aimed to study the association of ApoE polymorphism with AD in Guilan province, Iran. Methods: The study group consisted of 70 AD patients and 100 healthy individuals as a control group. All subjects were recruited from 21 March to 22 September 2015 at Imam Reza Clinic, Rasht, Iran. The genomic deoxyribonucleic acid (DNA) was extracted from peripheral blood leucocytes, and subsequently, subjects were genotyped for ApoE using tetra-primer amplification refractory mutation system-polymerase chain reaction (ARMS-PCR). The association between the risk allele and AD was assessed using the MedCalc software. Results: The distributions of ε(3)ε(3), ε(3)ε(4), ε(2)ε(2), ε(2)ε(4), ε(4)ε(4) and ε(2)ε(3) Genotypes among patients were 55.7%, 30.0%, 1.4%, 2.9%, 8.6%, 1.4% and in the controls were 79.0%, 8.0%, 0%, 1.0%, 1.0%, 11.0%, respectively. The genotype frequencies were significantly different between cases and the controls (P < 0.001). The individuals with the ε(4)ε(4) and ε(3)ε(4) genotypes had a greater risk for AD as compared to others; odds ratio (OR) = 12.15, 95% confidence interval (CI): 1.41-104.50, P = 0.020; OR = 5.32, 95% CI: 2.16-13.08, P = 0.003. In addition, the ε(4) allele is significantly associated with higher AD risk among the studied population (OR = 5.63, 95% CI: 2.74-11.58, P < 0.001). Conclusion: This case-control study suggests that the subjects with ε(4)ε(4) and ε(3)ε(4) genotypes had an increased risk for AD in Iranian population.