Association between Val66Met polymorphism of Brain-Derived Neurotrophic Factor (BDNF) gene and a deficiency of colour vision in alcohol-dependent male patients.

Brain-derived neurotrophic factor (BDNF) is a protein encoded, in humans, by BDNF gene on chromosome 11. BDNF protects adult neurons and promotes growth and differentiation during ontogenetic development but the nature and magnitude of its effects could be influenced by functional polymorphisms. The BDNF polymorphism Val66Met (rs6265) has been studied in the context of etiology of mental diseases including alcoholism. Alcoholism - a complex disorder known to be linked to several genes - has multiple manifestations, including sensory deficits such as those affecting vision. In the present study we examined a relationship between the Val66Met polymorphism, alcohol dependence and colour vision deficiency (CVD) in 167 alcohol-dependent men and 289 control male subjects. Statistical analysis revealed that almost half (about 48%) of the alcohol dependent men had a CVD. In addition we found that CVD was significantly associated (P=0.005) with the Val66Met polymorphism. The A allele containing 66Met promotes BDNF expression and this may protect humans against CVD induced by long-term excessive alcohol intake. The present findings indicate that alcohol-induced CVD does not depend solely on excessive alcohol consumption but is significantly influenced by genetic predisposition in the form of a specific BDNF polymorphism.