Glucagon-Like Peptide 1 Induces Differentiation of Islet Duodenal Homeobox-1–Positive Pancreatic Ductal Cells Into Insulin-Secreting Cells
- 1Division of Diabetes, Endocrinology and Metabolism, Cedars-Sinai Medical Center
- 2Division of Cell Biology, Vanderbilt University
- 3University of California Los Angeles, Los Angeles, California
Glucagon-like peptide-1 (GLP-1) is an incretin hormone capable of restoring normal glucose tolerance in aging glucose-intolerant Wistar rats. Whether the antidiabetic properties of GLP-1 are exclusively due to its insulin secretory activity remains to be determined. A GLP-1–dependent differentiation of pancreatic precursor cells into mature β-cells has recently been proposed. The aim of this study was to investigate whether pancreatic ductal epithelial cells could be differentiated into insulin-secreting cells by exposing them to GLP-1. Rat (ARIP) and human (PANC-1) cell lines, both derived from the pancreatic ductal epithelium, were used to test this hypothesis. A major difference distinguishes these two cell lines: whereas ARIP cells spontaneously express the β-cell differentiation factor islet duodenal homeobox-1 (IDX-1), PANC-1 cells are characteristically IDX-1 negative. GLP-1 induced the differentiation of ARIP cells into insulin-synthesizing cells, although it did not affect the phenotype of PANC-1 cells, as determined by fluorescence-activated cell sorting (FACS) analysis. Differentiation of ARIP cells by exposure to human GLP-1 occurs in a time- and dose-dependent manner, and this is associated with an increase in IDX-1 and insulin mRNA levels. Secretion of insulin was also induced in a parallel manner, and it was regulated by the concentration of glucose in the culture medium. Interestingly, PANC-1 cells, when stably transfected with human IDX-1, gained responsiveness to GLP-1 and were able to differentiate into β-cells, as determined by FACS analysis, insulin gene expression, intracellular insulin content, and insulin accumulation in the culture medium. Finally, we demonstrated that the receptor for GLP-1 is constitutively expressed by ARIP and PANC-1 cells and that the mRNA level for this transcript was increased by cellular transfection with human IDX-1. In summary, our study provides evidence that GLP-1 is a differentiation factor for pancreatic ductal cells and that its effect requires the expression of IDX-1.
- ANOVA, analysis of variance
- FACS, fluorescence-activated cell sorting
- FCS, fetal calf serum
- FITC, fluorescein isothiocyanate
- GLP, glucagon-like peptide
- GLP-R, GLP-1 receptor
- IDX-1, islet duodenal homeobox-1
- PBS, phosphate-buffered saline
- PCR, polymerase chain reaction
- RIA, radioimmunoassay
- RT, reverse transcription
Address correspondence and reprint requests to Riccardo Perfetti, MD, Div. Endocrinology and Metabolism, Becker Building, Room B-131, Department of Medicine, Cedars-Sinai Medical Center, 8700 Beverly Blvd., Los Angeles, CA 90048. E-mail:.
Received for publication 21 April 2000 and accepted in revised form 12 December 2000.