With regard to epidemiological evidence, high concentrations of leptin [10], resistin [11], visfatin [12], and PAI-1 [8, 13] have been associated with an increased risk of type 2 diabetes, whereas high adiponectin concentrations have been associated with a decreased risk of obesity [6] and type 2 diabetes [14, 15]. This evidence concerns the gene LEP and type 2 diabetes mellitus.