LEP and obesity due to melanocortin 4 receptor deficiency: Different gene SNPs have been shown to affect leptin and melanocortin pathways, promoting the development of clinical markers of obesity; the polymorphism rs7799039 of the leptin gene has been associated with obesity, and the SNP rs1137101 of the LEPR gene has been associated with a risk for the development of type 2 diabetes mellitus in the Turkish population [14].