Bdnf variant is associated with milder motor symptom severity in early-stage Parkinson's disease

Parkinson's disease (PD) progression is heterogeneous. Variants in PD-related genes may alter disease progression or severity. We examined if the single nucleotide variant rs6265 in the gene Bdnf alters clinical phenotype in early-stage, unmedicated PD. A retrospective analysis was conducted using data collected in the Deprenyl And Tocopherol Antioxidative Therapy Of Parkinsonism (DATATOP) study. DNA samples (n = 217) were genotyped for the Bdnf rs6265 variant, and the primary endpoint was time to initiate levodopa. The Parkinson's Progression Markers Initiative (PPMI) was used for validation (n = 383). The primary endpoint of time to initiate levodopa was associated with a delay in subjects with two copies of the rs6265 minor (Met66) allele (HR: 4.9; 95% CI: 1.3–18.8). Secondary endpoints were not different among genotypes. PPMI subjects with two Met66 alleles demonstrated significantly lower total and part III Movement Disorder Society – United Parkinson's Disease Rating Scale (MDS-UPDRS) scores at baseline, as well as more tremor-related symptoms, but not a delay in initiation of maintenance pharmacotherapy. Data from two distinct, unmedicated, early-stage PD cohorts suggest that carrying two copies of the rs6265 Met66 allele (∼4% of the population) is associated with less severity in motor symptoms and potentially a slower rate of progression. •The Bdnf rs6265 variant extends the unmedicated stage of Parkinson's disease.•Met/Met subjects have lower MDS-UPDRS scores in the unmedicated state.•Met/Met subjects have more tremor-related symptoms.•Genotyping for the rs6265 variant may be useful in clinical trial design.