Lack of association between BDNF rs6265 polymorphism and risk of type 2 diabetes: A protocol for meta-analysis and trial sequential analysis

BACKGROUND: Brain-derived neurotrophic factor (BDNF) rs6265 polymorphism has been previously suggested to be associated with the susceptibility of type 2 diabetes mellitus (T2DM), but results remained controversial. We aim to provide a more reliable conclusion about the association between BDNF rs6265 polymorphism and T2DM risk by using a meta-analysis. METHODS: Electronic databases such as Pubmed, Embase, CNKI, and Wanfang were searched for relevant articles published up to May 06, 2020. Pooled odds ratios (ORs) with 95% confidence intervals (CIs) were used to evaluate the strength of the associations. Subgroup analysis was carried out according to source of controls and quality score of included studies. A trial sequential analysis was conducted to reduce the risk of type I error. RESULTS: A total of 8 case-control studies (7 conducted in China) with 1576 T2DM patients and 1866 controls were included. Overall, our results indicated no significant association between BDNF rs6265 polymorphism and T2DM risk with the random-effects model (allele model: pooled OR = 1.14, 95% CI = 0.79–1.65, homozygote model: pooled OR = 1.13, 95% CI = 0.57–2.21, heterozygote model: pooled OR = 1.07, 95% CI = 0.78–1.48, dominant model: pooled OR = 1.14, 95% CI = 0.74–1.75 and recessive model: pooled OR = 1.10, 95% CI = 0.67–1.80). Subgroup analysis by source of controls and quality score also showed no significant association between BDNF rs6265 polymorphism and T2DM risk. Trial sequential analysis results confirmed the null association and further studies were unnecessary. CONCLUSION: This meta-analysis study indicated that no significant association between BDNF rs6265 polymorphism and T2DM risk.