The interaction of the haplotypes AAG (PPARGC1A gene) and CTCG (UCP1 gene) increased the susceptibility of IFG or T2DM, while that of AAG (PPARGC1A gene) and CTCA (UCP1 gene) lowered risk of IFG or T2DM. This evidence concerns the gene UCP1 and type 2 diabetes mellitus.