INS and obesity due to melanocortin 4 receptor deficiency: During further estimating causal effects on glycemic-related traits, the MR analysis results did not support any causal effect of genetically predicted NAFLD on fasting insulin levels; nevertheless, a significantly positive causal effect was observed (beta: 0.0152, 95% CI: 0.0087–0.0216; P < 0.001) after excluding the pleiotropic obesity-related SNP (Fig. 3, panel d).