UCP3 and obesity due to melanocortin 4 receptor deficiency: The relationship between UCP1-3 loci and susceptibility to obesity has been investigated in several genetic studies and particular attention has been focused on the -3826A/G (rs1800592) polymorphism in the UCP1 gene, the -866G/A polymorphism (rs659366), the Ala55Val (C/T; rs660339) polymorphism and the Ins/Del polymorphism in the UCP2 gene, and the -55C/T (rs1800849) polymorphism in the UCP3 gene [5], [10], [11].