• J Girard.
• CNRS UMR8104, InsermU567, département endocrinologie, métabolisme et cancer, université Paris-Descartes, institut Cochin, 24, rue du Faubourg-Saint-Jacques, 75014 Paris, France. gean.girard@inserm.fr
• Diabetes Metab. 2008 Dec 1;34(6 Pt 1):550-9.

AbstractThis paper briefly reviews the concept of incretins and describes the biological effects of the two incretins identified so far: the glucose-dependent insulinotropic polypeptide (GIP); and the glucagon-like peptide-1 (GLP-1). GIP is released by the Kcells of the duodenum, while GLP-1 is released by the Lcells of the distal ileum, in response to nutrient absorption. GIP and GLP-1 stimulate insulin biosynthesis and insulin secretion in a glucose-dependent manner. In addition, they increase beta-cell mass. GIP has a specific effect on adipose tissue to facilitate the efficient disposal of absorbed fat and, thus, may be involved in the development of obesity. GLP-1 has specific effects on pancreatic alpha cells, the hypothalamus, and gastrointestinal and cardiovascular systems. By inhibiting glucagon secretion and delaying gastric-emptying, GLP-1 plays an important role in glucose homoeostasis and, by inhibiting food intake, prevents the increase in body weight. As the metabolic effects of GIP are blunted in type 2 diabetes, this peptide cannot be used as an efficient therapy for diabetes. In contrast, GLP-1 effects are preserved at high concentrations in type 2 diabetes, making this peptide of great interest for the treatment of diabetes, a topic that will be discussed in the second part of this review.

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