Prevalence of ApoE Alleles in a Spanish Population of Patients with a Clinical Diagnosis of Alzheimer’s Disease: An Observational Case-Control Study

<i>Background and Objectives</i>: Alzheimer's dementia is a progressive neurodegenerative disease that affects memory abilities due to genetic and environmental factors. A well-known gene that influences the risk of Alzheimer's disease is the apolipoprotein E (APOE) gene. The APOE gene is involved in the production of a protein that helps transport cholesterol and other types of fat in the bloodstream. Problems in this process are thought to contribute to the development of Alzheimer's disease. APOE comes in several forms, which are called alleles (ε2, ε3, ε4). <i>Materials and Methods</i>: Therefore, our study aims to identify those subjects with a higher genetic risk through the polymorphism of the APOE gene, using a population screening in patients with a clinical diagnosis of AD in a region of Spain, Castilla y León, as potential biomarkers and to identify individuals at increased genetic risk by polymorphism of the APOE gene. An observational case-control study was conducted in Castilla y León (Spain). Saliva samples were collected and the ApoE gene was analyzed by PCR and agarose gel electrophoresis, respecting ethical criteria. <i>Results</i>: In the Alzheimer's population in Castilla y León, a high prevalence of ApoE3 (74%) was found, followed by ApoE4 (22%); in addition, a higher presence of the ε4 allele was found in the Alzheimer's disease (AD) group than in the control group. It was also observed that the ε2/ε2 genotype was not found in any individual with AD but was found in healthy subjects and that the opposite was observed for the ε4/ε4 genotype. The odds ratio (OR) indicated a risk four times greater of having AD if having the ε4 allele. <i>Conclusions</i>: The demonstrated relation between the different isoforms and the likelihood of developing AD has led to its consideration as a biomarker and a potential pre-symptomatic therapy. The molecular mechanisms that confer a disruptive and protective role to ApoE4 and ApoE2, respectively, are still being studied.