Activation of GLP-1R is involved in regulation of hyperglycemia, and GLP-1R agonists including exenatide, liraglutide, and lixisenatide are important therapeutics for type II diabetes (Burcelin et al., 2014) Especially, GLP-1 secreted from intestinal cells activates glucose-dependent insulin secretion and inhibits glucagon release (MacDonald et al., 2002). Here, GCG is linked to type 2 diabetes mellitus.