GIP and type 2 diabetes mellitus: Although the exact mechanisms underlying the loss of incretin activity in type 2 diabetes patients are unclear, it is evident that while the effects of GLP-1 are largely preserved [9–11], the insulinotropic effect of GIP is almost lost in type 2 diabetes, potentially due to a defective expression of GIP receptors, a downregulation of GIP signaling, or a general reduction of beta cell function and mass [11–18].