CCK and diabetes mellitus: Particularly relevant to the control of nutrient metabolism and food intake are the cells producing the hormones glucagon‐like peptide‐1 (GLP‐1), which forms the basis for the new class of injectable diabetes and weight loss drugs (Drucker & Holst, 2023), cholecystokinin (CCK), peptideYY (PYY) and glucose‐dependent insulinotropic polypeptide (GIP).