APOE and CYP2E1 polymorphisms, alcohol consumption, and Parkinson's disease in a Japanese population

Apolipoprotein E (APOE) is associated with increased oxidative stress, which is caused by reactive oxygen species (ROS). Enhanced cytochrome P450 2E1 (CYP2E1) activity may also increase formation of neurotoxins such as ROS. As Parkinson's disease (PD) is a neurodegenerative disorder, both the APOE and CYP2E1 genes that are involved in neurodegeneration by oxidative stress may be associated with PD risk. We investigated the relationship of the APOE and CYP2E1 rs2864987 polymorphisms and PD risk with special attention to the interaction with alcohol consumption among 238 patients with PD and 296 controls in a Japanese population. The frequencies of the E > 2, E > 3, and E > 4 alleles of the APOE polymorphism among controls were 3.72, 86.7, and 9.63%, respectively. As compared with the APOE epsilon 3/epsilon 3 genotype, the 2/epsilon 4 genotype was associated with an increased risk of PD (adjusted odds ratio (OR) = 9.50, 95% (confidence interval) CI = 1.12-80.6). The presence of the epsilon 3 allele was associated with a decreased risk of PD. Meanwhile, CYP2E1 rs2864987 was not associated with PD risk. Although CYP2E1 is involved in the metabolism of alcohol, there was no evidence of interaction between alcohol consumption and CYP2E1 rs2864987. Our results suggested that the APOE polymorphism might play an important role in PD susceptibility in our Japanese population. Future studies involving larger control and case populations and better alcohol consumption histories will undoubtedly lead to a more thorough understanding of the role of polymorphisms of genes related to the generation of ROS in PD development.