GLP-1 REGULATES PROLIFERATION OF GLP-1 SECRETING CELLS THROUGH A FEEDBACK MECHANISM

Abstract Background and aim: Diabetes mellitus (DM) is a chronic and progressive illness that affects all type of populations and ages. According to World health organization (WHO) by 2030 it will be 366 million people effected world wild. Many new drugs are Glucagon-like peptide-1 (GLP-1) based therapy for treatment of type 2diabetes. GLP-1 is released from the intestinal L-cells, and is a potent stimulator of glucose-dependent insulin secretion. The aim of this study was to investigate the effect of GLP-1 and its stable analogs on cell proliferation of GLP-1 secreting GLUTag cells. Material and methods: GluTag cells were incubated for 48h in DMEM medium containing (0.5% fetal bovine serum and 100 IU/ml penicillin and 100 μg/ml streptomycin and 3mM glucose concentration) in the present or absence of the agents. DNA synthesis was measured using 3H- thymidine incorporation and Ki67 antigen staining. Western blot were performed to investigate the present of GLP-1 receptor in GLUTag cells. Results/conclusions: These results suggest that GLP-1 regulates proliferation of the GLP-1-secreting cell through a feedback mechanism via its receptor. Since serum GLP-1 levels are decreased in type 2 diabetic patients, the effect of GLP-1 on the GLP-1-secreting cell proliferation suggested here provides a novel beneficial long-term effect of the incretin-based drugs in clinical practice i.e. through increase of the GLP-1-secreting cell mass, augmenting the incretin effect. In addition, the feedback mechanism action of GLP-1 reveals a new insight in regulation manner of the L-cell proliferation. GLP-1(7-36) increased cell proliferation in GLUTag cells, an effect which was blocked by the GLP-1 receptor antagonist exendin(9-39). The GLP-1 receptor was expressed in GluTag cells. Keywords: Incretin hormone, GLP-1, GLP-1 receptor, Exendin-4, Diabete