GASTRIC-INHIBITORY POLYPEPTIDE - ITS PHYS IOLOGY AND PATHOLOGY

The main effects of gastric inhibitory polypeptide (GIP) are to reduce the rate of nutrient absorption, by its actions on the digestive trac t, and to stimulate nutrient utilisation, by its actions on metabolism e. The participation of GIP in the development of obesity and type II diabetes is difficult to show, even in genetically obese animal models which exhibit hypersecretion of GIP. In fact, it is possible to preve nt hypersecretion of GIP without influencing the development of obesit y. In this review, the best model for the involvement of GIP in obesit y is described: where hypersecretion of GIP is secondary to hyperphagi a (particularly of fat) which itself causes a hyperplasia of the endoc rine cells of the digestive tract (eg. GIP secreting cells) and hypers ecretion of insulin and resistance to insulin. The participation of GI P in obesity is perhaps related to its effects on fat metabolism. In t he future, the role of GIP in obesity may be clarified by studies of f at and glucose metabolism at the cellular level. Studies in ruminants may be another fruitful subject of research. GIP is present in the sma ll intestine of the ruminant but its importance is not known, particul arly bearing in mind that the feedstuffs given to ruminants are modifi ed considerably by the microflora.