Association of the MAOB rs1799836 Single Nucleotide Polymorphism and APOE ε4 Allele in Alzheimer’s Disease

Background: The dopaminergic system is functionally compromised in Alzheimer’s Disease (AD). The activity of Monoamine Oxidase B (MAOB), the enzyme involved in the degradation of dopamine, is increased during AD. Also, increased expression of MAOB occurs in the postmortem hippocampus and neocortex of patients with AD. The MAOB rs1799836 polymorphism modulates MAOB transcription, consequently influencing protein translation and MAOB activity. We recently showed that cerebrospinal fluid levels of amyloid β1-42 are decreased in patients carrying the A allele in MAOB rs1799836 polymorphism. Objective: The present study compares MAOB rs1799836 polymorphism and APOE, the only confirmed genetic risk factor for sporadic AD. Methods: We included 253 participants, 127 of whom had AD, 57 had mild cognitive impairment, 11 were healthy controls, and 58 suffered from other primary causes of dementia. MAOB and APOE polymorphisms were determined using TaqMan SNP Genotyping Assays. Results: We observed that the frequency of APOE ε4/ε4 homozygotes and APOE ε4 carriers is significantly increased among patients carrying the AA MAOB rs1799836 genotype. Conclusion: These results indicate that the MAOB rs1799836 polymorphism is a potential genetic biomarker of AD and a potential target for the treatment of decreased dopaminergic transmission and cognitive deterioration in AD.