DPP4 and type 2 diabetes mellitus: Thus, in mice, significant antihyperglycaemic effects of DPP-4 inhibition are still apparent in animals lacking the GLP-1 receptor (43), while in clinical studies, GLP-1 receptor antagonism (using exendin 9-39) eliminates only approximately half of the glucose-lowering effect in patients with T2DM treated with DPP-4 inhibitors (44, 45).