Initial short-term studies that found that exogenous GIP barely stimulates insulin secretion in people with type 2 diabetes (Fig. 3) [21–23] and does not induce a substantial reduction in plasma glucose concentrations in hyperglycaemic individuals with type 2 diabetes (Fig. 4) [41, 82] did not support the idea that GIP has therapeutic potential for the treatment of type 2 diabetes. This evidence concerns the gene INS and type 2 diabetes mellitus.