GCG and type 2 diabetes mellitus: Type 2 diabetes mellitus (T2DM) is caused by a number of factors namely gene mutations that lead to “underexpression” or overexpression of the GK, GKRP, glucagon, insulin, and PDX-1; β-cell dysfunction, hepatic inflammation, unusual excitability of sympathetic nerves, and diet-inducing factors like taking high fat content.