GCG and Hyperglycemia: Activation of GLP-1 signaling by in vivo administration of GLP-1, GLP-1 analogs resistant to DPP-4, or DPP-4 inhibitors can ameliorate hyperglycemia in murine models and stimulate ⍺-cell proliferation, as well as ⍺- to β-cell transdifferentiation [49,65,66,67].