Brain-derived neurotrophic factor (Val66Met) polymorphism and olfactory ability in young adults

Background: Brain- derived neurotrophic factor (BDNF) is linked to neurodegenerative diseases (e.g. Alzheimer disease and Parkinson disease) which are often characterized by olfactory impairment. A specific single nucleotide polymorphism of the BDNF gene, the Val66Met, modulates intracellular trafficking and activity-dependent secretion of BDNF protein. The aim of this study was to investigate a possible association between brain- derived neurotrophic factor Val66Met polymorphism and olfactory function, a well-known biomarker for neurodegeneration, in healthy young adults. A total of 101 subjects (45 males, age 38.7 +/- 9.4 years) were assessed using the Sniffin' Sticks Extended Test, a highly reliable commercial olfactory test composed of three sub-parts, calculating olfactory threshold (sensitivity), odor discrimination and odor identification. The Val66Met polymorphism was determined by polymerase chain reaction -restriction fragment length polymorphism (PCR-RFLP) analysis. Results: An impaired function in Met carriers was found, especially when compared to subjects with Val/Val genotype, in the threshold (5.5 +/- 2.0 vs 6.5 +/- 1.8, p = 0.009), discrimination (10.3 +/- 2.5 vs 11.9 +/- 2.2, p = 0.002), and identification task (13.3 +/- 1.6 vs 14.1 +/- 1.3, p = 0.007), as well as in the overall TDI Score (29.1 +/- 4.5 vs 32.6 +/- 3.9, p < 0.001). Conclusions: These findings appear to have implications for the evaluation of olfactory function and the relation of its impairment to cognitive decline and neurodegenerative disease.