In clinical practice, recombinant leptin is an important experimental and therapeutic tool: recent studies on metreleptin (recombinant methionyl human leptin) have suggested its efficacy in patients with T2DM (Vasandani et al., 2017) as leptin acts directly on liver cells to reduce the production of glucose and to increase the sensitivity of insulin (Rehman et al., 2018). This evidence concerns the gene LEP and type 2 diabetes mellitus.