In studies of individuals with long-standing T2DM, in whom physiological GIP infusions were completely without effect, a 4-week period of intensive, basal-bolus insulin therapy, which nearly normalized glucose levels, there was some restoration of GIP’s insulinotropic effect, but the responses were still very far from normal levels or levels observed after pharmacological GLP-1 therapy (33). Here, GIP is linked to type 2 diabetes mellitus.