In T2DM, IR is strongly determined by α cells (hyperglucagonemia), adipocytes (fat lipolysis), kidneys (high glycemic reabsorption), the gastro-intestinal system (resistance and/or deficiency of incretin), the brain (IR), and by complicated associations of these metabolic dysfunctions with genes linked with T2DM [9]. Here, GCG is linked to type 2 diabetes mellitus.