Genetic factors associated with the predisposition to late onset Alzheimer's disease.

Background: Alzheimer's disease is a progressive, irreversible neurodegenerative disorder characterized by loss of memory and cognitive skills. More than 90% of cases are sporadic and have later age of onset. Many studies have shown a genetic predisposition for late onset Alzheimer's disease (LOAD). The most studied genetic predisposition factor is apolipoprotein E gene besides other susceptibility genes involved in vascular pathologies, homocysteine metabolism, and neuronal growth and differentiation such as methylenetetrahydrofolate reductase (MTHFR), angiotensin-converting enzyme (ACE), APOB and brain derived neurotrophic factor (BDNF).

Methods: In this study Factor V Leiden (G1691A) and H1299R, prothrombin G20210A, Factor XIII V34L, B-fibrinogen -455G>A, PAI-1 5G/4G, HPA1 b/a, MTHFR C677T, MTHFR A1298C, APOE, ACE I/D, BDNF C270T and G196A polymorphisms were evaluated in 100 LOAD patients and 100 age matched healthy controls.

Results: APOE4 allele, MTHFR CC and BDNF TT genotypes were significantly higher in LOAD patients compared to the control group (p < 0.001, p = 0.04, p = 0.03, respectively). There were no significant associations between other genotypes and allele frequencies. Mini-Mental State Examination (MMSE) scores and age at onset of the patients were also evaluated for each and combined genotypes. Age at onset was significantly lowered by about approximately 4 and 5 years in patients carrying BDNF TT and MTHFR TT genotypes, respectively.

Conclusion: APOE, MTHFR A1298C and BDNF C270T polymorphisms may be associated with LOAD and BDNF and MTHFR alleles may play a role in the age at onset of the LOAD.