GCGR and type 2 diabetes mellitus: They not only normalize blood glucose levels in insulin-naive T1D mice and patients but also show potent hypoglycemic effects in T2D mice and monkeys.494–496 GCGRmAbs were also able to induce δ-cell proliferation and transdifferentiation into β cells along with ductal cells.497 Also, anti-GCGR antibodies were shown to promote β cell proliferation and α cell transdifferentiation into β cells.498 The underlying molecular mechanisms remain to be explored.