The Role of the Incretin Hormones GIP and GLP-1 in the Pathogenesis of Type 2 Diabetes

The incretin effect, i.e. the postprandial augmentation of insulin secretion by gastrointestinal hormones, mediates similar to 50-70% of the meal-related increments in insulin secretion in healthy individuals. In contrast, the incretin effect is almost completely absent in patients with type 2 diabetes. The impaired incretin effect in type 2 diabetes has been mainly attributed to the reduced insulinotropic activity of GIP, whereas the actions of GLP-1 are largely preserved. Furthermore, a diminished secretion of GLP-1 has been suggested to contribute to the impaired incretin effect in type 2 diabetes, but this finding has not been confirmed in the majority of studies. This article aims to compare the secretion and action of the incretins GIP and GLP-1 between patients with type 2 diabetes and healthy individuals. In addition, the importance of alterations in the entero-insular axis for the pathogenesis of type 2 diabetes will be discussed.