BDNF and type 2 diabetes mellitus: MR analysis indicated that genetically predicted higher serum BDNF levels werecausally associated with reduced risks of type 2 diabetes (odds ratio (OR) =0.85, 95% confidence interval (95% CI): 0.74–0.97, p value = 0.02),hyperlipidemia (OR = 0.89, 95% CI: 0.81–0.99, p value = 0.03) andhypertension (OR = 0.97, 95% CI: 0.94–1.00, p value = 0.04; Fig. 6).There was no significant causal relationship observed between serum BDNF levelsand HDL cholesterol and waist circumference (p valueall> 0.05;Fig. 6).