A polymorphism of the brain-derived neurotrophic factor (BDNF) is associated with Alzheimer's disease in patients lacking the Apolipoprotein E ε4 allele

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Abstract
Because of its implication in neuroprotection, formation of long lasting memories and a disturbed function in Alzheimer's disease (AD), brain-derived neurotrophic factor (BDNF) may represent an appropriate candidate gene conferring risk to AD. Recently, a single nucleotide polymorphism (C-270T) within the BDNF gene has been associated with late onset AD in a Japanese population giving an odds ratio (OR) of 3.8. Because of the importance of this finding we analysed the BDNF polymorphism in a German sample consisting of 210 patients with AD and 188 cognitively healthy controls. The T-allele frequency was higher in patients with AD (11.9%) compared to controls (6.9%) (P = 0.035; OR = 2.26; 95% CI: 1.04–4.48). The risk conferred by the T-allele was stronger in patients who lack the ApoE ε4 allele giving an OR of 2.61 (1.21–5.64) P = 0.015, particularly in patients with early onset of the disease; OR 3.13 (1.32–7.43); P= 0.01. Due to the small number of patients showing both, lack of the ApoE ε4 allele and the BDNF T allele (n = 18), the result needs to be confirmed in a larger sample. The results suggest that the BDNF C-270T polymorphism is a relevant risk factor for AD particularly in patients lacking the ApoE ε4 allele in this German sample.