BDNF G196A (Val66Met) polymorphism associated with cognitive impairment in Parkinson's disease.

Brain-derived neurotrophic factor (BDNF) is a neurotrophin widely expressed in the mammalian brain, regulating neuronal survival and known to influence dopaminergic neurons and cognitive processes. The present study investigated the BDNF Val66Met polymorphism associations with PD risk, and cognitive impairment in PD. A total of 486 study subjects (244 PD and 242 age and sex matched controls) were included in the study. UPDRS score, Hoehn-Yahr staging and the Schwab-England scale were used to assess motor abilities and activity during daily life. The patients were classified into groups with dementia (PDD, n=69) and without it (nPDD, n=166) on the basis of neuropsychological assessment. The most common functional polymorphism in BDNF Val66Met (rs6265, G196A) gene was determined using TaqMan real-time PCR assay. Frequencies of evaluated BDNF alleles and genotypes were similar in PD and the controls. The mean age of disease onset among BDNF Met/Met carriers was later (65.00±6.13) in comparison to Val/Val (57.45±10.68) and Val/Met (56.33±10.91) subjects (p=0.077). The studied BDNF polymorphism was not associated with cognitive status in PD patients. However, patients with Met/Met alleles demonstrated better delayed recall of information than patients with Val/Val alleles. The results of multivariate logistic regression analysis revealed age (p=0.0003) and the disease stage (p=0.002) as independent risk factors predisposing to PD dementia.