During recent years, metformin, which is an effective oral biguanide insulin sensitizer, has been widely used for treating type 2 diabetes mellitus (T2DM) as an antihyperglycemic agent [13], by improving tissue sensitivity to insulin while inhibiting hepatic glucose production, enhancing peripheral glucose uptake, and decreasing insulin levels [14, 15], and approved by the United States Food and Drug Administration (FDA) [16]. This evidence concerns the gene INS and type 2 diabetes mellitus.