Association Between Alzheimer Disease and APOE Gene Polymorphisms in Turkish Population

Alzheimer’s disease (AD) is a progressive neurodegenerative disease and the most common form of the dementia which is characterized by the accumulation of amyloid plaques at the extracellular compartment and formation of neurofibriller tangles at the intracellular compartment which results in the degeneration of the neuron bodies and synapses. APOE gene polymorphisms in late-onset AD have a significant effect on cellular levels and also have been associated with neuropathological conditions. To determine the effect of APOE gene polymorphisms on Alzheimer's patients, we have included 629 AD patients between 45-90 years and 200 healthy subjects into the study. APOE gene isoforms were determined by real-time PCR method. APOE genotype distributions were significantly different between the patient and control groups (p <0.001). There was a statistically significant difference in allele frequencies between patient and control groups (p <0.001). At ε4 allele carriers there was a 5.49 times higher risk of AD than the subjects that lack the ε4 allele (OR= 5.49, %95 CI: 3.86-7.81, p<0.001). The MMSE (Mini-Mental State Examination) score was lower among APOE ε4-carriers when compared to the non-carriers (p<0.001). On the basis of all these data it can be concluded that the APOE ε4 allele increases the risk of development of AD. Our results confirmed that the APOE genotype is a risk factor for AD. However, considering the importance of the geographic location and ethnicity, it is a fact that larger molecular studies are needed to clearly determine the contribution of the APOE gene to the development of AD