Background: Brain-derived neurotrophic factor (BDNF) is the most abundant neurotrophin, which contributes to the neuronal survival and synaptic plasticity. This study investigated the associations of BDNF  polymorphisms at the 3ʹ-untranslated region with risk and outcome of ischemic stroke in a Chinese Han population.
Methods: 500 patients and 520 controls were enrolled for BDNF  rs7124442 genotyping. The binding of miR-922 to BDNF  rs7124442 was examined by luciferase assay; BDNF  expression was assessed using qRT-PCR.
Results: Alcohol consumption, cigarette smoking, diabetes, hypertension (all P < 0.001) and higher serum triglycerides concentration (P = 0.009) were associated with an increased risk of developing ischemic stroke. After adjusted for age and sex, logistic regression analysis showed that IS patients harbored with rs7124442 TC genotype had a milder initial stroke (Dominant model: OR = 0.45, 95% CI = 0.25–0.81, P = 0.015), and also showed a better short-term recovery (Dominant model: OR = 0.39, 95% CI =0.24–0.68, P = 0.003). Furthermore, we found that co-transfection of hsa-miR-922 mimics with BDNF  3ʹ-UTR containing the mutated allele C changed luciferase activity when compared to co-transfection with BDNF  3ʹ-UTR containing the wild-type allele. Besides, patients carrying BDNF  rs712444 TC or CC genotype had an increased level of BDNF  compared with patients with the TT genotype.
Conclusion: Our study demonstrates that the SNP rs7124442 in BDNF  3ʹ-UTR, through affecting the regulatory role of miR-922 in BDNF  expression, might act as a protective factor for the outcome of patients with ischemic stroke.
Keywords: ischemic stroke, polymorphism, brain-derived neurotrophic factor, BDNF , miR-922, outcome