They examined the serum concentrations and found significantly lower serum concentrations of GIP in the PDAC patients with NOD or pre-diabetes (n = 76) or normal glycemic regulation (n = 18) compared with the patients with type 2 diabetes without PDAC and the control group (15.5 (3.7–64.5) or 6.5 (1.7–24.5) versus 39.8 (15.1–104.7) or 28.8 (7.4–112.2) ng/L, respectively; p < 0.001). This evidence concerns the gene GIP and diabetes mellitus.