Effect of GLP-1 (glucagon-like peptide 1:7-36 amide) on porcine pancreatic endocrine cell proliferation and insulin secretion.

Abstract

We have established a method of isolation and primary monolayer culture of porcine pancreatic endocrine (PE) cells using nicotinamide. Recently, several insulin-stimulating factors have been recognized as modifying the function of endocrine cells. Glucagon-like peptide 1 (GLP-1), derived from intestinal cells, is one of the substances that may regulate insulin secretion and cell proliferation. The aim of the current study was to examine the effect of GLP-1 on PE cell proliferation and insulin secretion in our culture system. The PE cells were prepared by nonenzymatic digestion and cultured in media with or without 10 nmol/L GLP-1 and maintained for 15 days. Basal insulin secretion and the glucose stimulated-response were observed by enzyme assay. PE-cell proliferation was assessed using 5-bromo 2' deoxyuridine (BrdU). beta-Cell specificity was confirmed by double staining with anti-BrdU and insulin antibody. mRNA expression in PE cells for insulin and pancreatic and duodenal homeobox gene 1 (PDX-1), a transcription factor, was semiquantitated by a real-time PCR method. Neither baseline nor glucose-stimulated insulin secretion differed significantly with or without the addition of 10 nmol/L GLP-1. However, significant changes of insulin secretion were observed in doses up to 100 nmol/L of GLP-1. BrdU incorporation increased with 10 nmol/L GLP-1 from 2.35+/- 0.16% to 9.11+/- 0.53% as compared with the control (from 2.17 +/- 0.57% to 6.13 +/- 0.35%). This increase was observed after a 12-day culture period. Double staining identified well-preserved insulin-containing cells, but neither the number of positive cells nor staining intensity differed significantly between the 2 groups during the 15-day culture period. The level of mRNA expression for both insulin and PDX-1 increased slightly but significantly. GLP-1 has a proliferative effect on PE cells and affects gene expression in short-term culture.