Gastric inhibitory polypeptide and insulin release in response to oral and intravenous glucose in coeliac disease.

Eight patients with biopsy-verified coeliac disease were investigated after remission on a gluten-free diet. A 50-g oral glucose load (OGTT) and an intravenous glucose infusion (IVGI) giving the same plasma glucose profile as the OGTT were carried out. The relation between gastric inhibitory polypeptide (GIP) plasma levels after oral glucose and the insulin release during OGTT and IVGI were studied. Plasma GIP concentration in the fasting state and the increase in plasma GIP during OGTT were significantly lower than in a group of eight healthy volunteers. However, the insulin potentiation during OGTT, the incretin effect, was normal. The results indicate the existence of other incretins than GIP. These are probably released from the distal small bowel in patients with coeliac disease.