Several genetic variants in the UCP2-UCP3 gene cluster have been examined in multiple studies, including −866G/A (rs659366), Ala55Val (rs660339), a 45-bp insertion/deletion (I/D) in the 3′ untranslated region (UTR) of exon 8 in UCP2, and the −55C/T (rs1800849) polymorphism in UCP3, and the associations with obesity and/or diabetes were also reported. This evidence concerns the gene UCP3 and diabetes mellitus.