BDNF Val66Met polymorphism is associated with cognitive impairment in Italian patients with Parkinson's disease

Background and purpose:
A possible association between Parkinson's disease (PD) and the polymorphism of Brain Derived Neurotrophic Factor (BDNF) G196A (Val66Met) has been suggested by different studies that nevertheless yielded-contrasting result. The purpose of this study was to analyze such possible association in a cohort of Italian PD patients.
Methods:
The BDNF polymorphisms were analyzed in 294 Italian patients with PD; results were compared to those obtained in 233 age- and sex-matched healthy controls (HC) enrolled from two tertiary centres in Italy. Polymorphisms were determined by Restriction Fragment Length Polymorphism (RFLP) analysis; correlations between BDNF G196A polymorphism, and cognitive function were established by sub analyzing the results upon dividing PD patients based on their Mini Mental State Examination (MMSE) score.
Results:
Univariate analysis showed a highly significant correlation between the BDNF(AA) genotype and a MMSE score < 24. Hence, the distribution of this genotype in PD individuals with a MMSE score < 24 was significantly increased compared to PD patients with an MMSE score > 24 and HC (P < 0.001 in both cases). Multivariate analyses showed that BDNF (AA) genotype was associated to a sixfold risk of cognitive impairment.
Conclusions:
The BDNF(AA) homozygote genotype is over-represented in PD patients compared with normal individuals; this genotype was significantly correlated to cognitive impairment, age and disease severity. These results, although preliminary, could be important in establishing novel diagnostic and therapeutic approaches to PD.