Pancreatic beta-cells expressing GLP-1 are resistant to the toxic effects of immunosuppressive drugs.

Abstract	Glucose intolerance is often observed after pancreatic islet cell transplantation. The administration of immunosuppressive agents (ISD), necessary to avoid tissue rejection, is in part responsible for hyperglycemia. To investigate whether mouse insulinoma (MIN6) cells transfected with the glucagon like peptide-1 (GLP-1) fragment of the proglucagon gene (RIP/GLP-1 MIN6 cells) are resistant to the toxicity derived from the administration of ISD. RIP/GLP-1 MIN6 cells, as well as parental MIN6 cells, were exposed to a cocktail of ISD. The secretion of insulin and the expression of apoptosis-related proteins were investigated by RIA and western blot analysis. Cell apoptosis was quantified by FACS analysis. Finally, to study whether the antiapoptotic action of GLP-1 was a function of its effect on insulin secretion, or rather it was a direct effect of GLP-1, cells were cultured with or without diazoxide or exendin-9. GLP-1 improved the functional activity and the viability of cells exposed to ISD. The insulin secretion of RIP/GLP-1 MIN6 cells after exposure to ISD was preserved. The expression of GLP-1 by beta-cells reduced the number of apoptotic cells and increased the expression of the antiapoptotic protein Bcl-2. GLP-1 also decreased the abundance of the proapoptotic markers PARP-p85 and Smac/Diablo. Treatment of cells with the diazoxide did not abolish the protective advantage that cells transfected with GLP-1 had; conversely the exposure of cells to exendin-9 was associated with a restored susceptibility to apoptosis. This report demonstrates that GLP-1 is capable of preserving beta-cell function and protecting cells from apoptotic cell death.
Authors	Eugenio D'Amico, Hongxiang Hui, Nasif Khoury, Umberto Di Mario, Riccardo Perfetti
Journal	Journal of molecular endocrinology (J Mol Endocrinol) Vol. 34 Issue 2 Pg. 377-90 (Apr 2005) ISSN: 0952-5041 [Print] England
PMID	15821104 (Publication Type: Journal Article, Research Support, Non-U.S. Gov't)
Chemical References	Antihypertensive Agents Apoptosis Regulatory Proteins Carrier Proteins DIABLO protein, human Diablo protein, mouse Immunosuppressive Agents Insulin Intracellular Signaling Peptides and Proteins Mitochondrial Proteins Peptide Fragments Protein Precursors Proto-Oncogene Proteins c-bcl-2 exendin (9-39) Glucagon-Like Peptide 1 Glucagon CASP3 protein, human Casp3 protein, mouse Caspase 3 Caspases Glucose Diazoxide
Topics	Animals Antihypertensive Agents (pharmacology) Apoptosis Apoptosis Regulatory Proteins Carrier Proteins (metabolism) Caspase 3 Caspases (metabolism) Cell Line, Tumor Cell Survival DNA Fragmentation Diazoxide (pharmacology) Dose-Response Relationship, Drug Glucagon (genetics, metabolism, pharmacology) Glucagon-Like Peptide 1 Glucose (metabolism) Humans Immunosuppressive Agents (toxicity) Insulin (metabolism) Insulin Secretion Intracellular Signaling Peptides and Proteins Islets of Langerhans (cytology, drug effects, metabolism) Mice Mitochondrial Proteins (metabolism) Peptide Fragments (genetics, metabolism, pharmacology) Protein Precursors (genetics, metabolism, pharmacology) Proto-Oncogene Proteins c-bcl-2 (metabolism)

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