GIP

Glucose-Dependent Insulinotropic Polypeptide

GIP (glucose-dependent insulinotropic polypeptide, formerly called gastric inhibitory polypeptide) is an incretin hormone released by K-cells in the lining of the duodenum and upper jejunum. Like GLP-1, it is released when you eat and boosts glucose-dependent insulin release from pancreatic beta cells. But GIP’s effects reach well beyond the pancreas.

GIP receptors are found in fat tissue, bone, the brain and the cardiovascular system, among other organs. In fat tissue, GIP promotes fat storage and affects how fat cells work, which long made it a contested target in obesity research. Some early studies suggested blocking GIP could reduce fat build-up. More recent evidence, including data from tirzepatide (a GIP/GLP-1 dual agonist), shows that activating the GIP receptor can, surprisingly, increase weight loss when combined with GLP-1 receptor activation. Exactly why is still being studied. Leading ideas include stronger fullness signals in the brain and better fat tissue function.

GIP receptor activation is one of retatrutide’s three receptor pathways. It is thought to complement GLP-1’s effects on appetite and blood sugar while adding metabolic benefits through its effects on fat tissue and energy balance. Like natural GLP-1, the body’s own GIP is quickly broken down by DPP-4 and has a half-life of about seven minutes in its active form.

Researchers are still working out GIP’s role in metabolic disease, and GIP receptor activation is one of the newer areas of incretin drug research. Its inclusion in multi-receptor drugs such as retatrutide and tirzepatide reflects a growing understanding that hitting several hormone pathways at once can produce synergistic metabolic benefits.