AstraZeneca.

No abstract

The regeneration of pancreatic islet ␤ cells is important for the prevention and cure of diabetes mellitus. We have demonstrated that the administration of poly(ADP-ribose) synthetase͞polymerase (PARP) inhibitors such as nicotinamide to 90% depancreatized rats induces islet regeneration. From the regenerating islet-derived cDNA library, we have isolated Reg (regenerating gene) and demonstrated that Reg protein induces ␤-cell replication via the Reg receptor and ameliorates experimental diabetes. However, the mechanism by which Reg gene is activated in ␤ cells has been elusive. In this study, we found that the combined addition of IL-6 and dexamethasone induced the expression of Reg gene in ␤ cells and that PARP inhibitors enhanced the expression. Reporter gene assays revealed that the ؊81 Ϸ ؊70 region (TGCCCCTCCCAT) of the Reg gene promoter is a cis-element for the expression of Reg gene. Gel mobility shift assays showed that the active transcriptional DNA͞protein complex was formed by the stimulation with IL-6 and dexamethasone. Surprisingly, PARP bound to the cis-element and was involved in the active transcriptional DNA͞protein complex. The DNA͞protein complex formation was inhibited depending on the autopoly(ADP-ribosyl)ation of PARP in the complex. Thus, PARP inhibitors enhance the DNA͞ protein complex formation for Reg gene transcription and stabilize the complex by inhibiting the autopoly(ADP-ribosyl)ation of PARP.P ancreatic ␤ cells of the islets of Langerhans are the only cells that produce insulin in humans as well as in almost all animals, but they have a limited capacity for regeneration, which is a predisposing factor for the development of diabetes mellitus. Strategies for influencing the replication and growth of the ␤-cell mass are therefore important for the prevention and͞or treatment of diabetes (1). We have established a model for islet regeneration in 90% depancreatized rats treated with poly(ADP-ribose) synthetase͞ polymerase (PARP) inhibitors such as nicotinamide and 3-aminobenzamide: Regenerating islets in the pancreatic remnants of PARP inhibitor-treated rats were markedly enlarged and consisted largely of insulin-producing ␤ cells, preventing the development of diabetes that would otherwise have been caused by the 90% pancreatectomy (2). In screening the regenerating islet-derived cDNA library, we found a novel gene and named it Reg (regenerating gene) (3-5). The rat Reg cDNA encoded a 165-amino acid protein with a 21-amino acid signal peptide. We also isolated the human REG cDNA, which encoded a 166-amino acid protein with a 68% amino acid sequence identity to the rat Reg protein (3). Rat and human Reg proteins stimulated the replication of pancreatic ␤ cells and increased the ␤-cell mass in 90% depancreatized rats and in nonobese diabetic mice, resulting in the amelioration of diabetes (6, 7). We have recently identified a Reg protein receptor that mediates a growth signal of Reg protein for ␤-cell regeneration (8). The expression of the Reg receptor, however, was not increased in reg...

No abstract

Reg (regenerating gene) was isolated as a gene specifically expressed in regenerating islets. We have demonstrated in vitro and in vivo that the exogenous addition of rat and human Reg gene products, Reg/REG proteins, induced ␤-cell replication via the Reg receptor and thereby ameliorated experimental diabetes. In the present study, we produced Reg knockout mice by homologous recombination. The Reg gene disruption resulted in a null mutation. Knockout mice developed normally. Islets from the Reg knockout mice appeared morphologically indistinguishable from those of normal controls. However, [3 H]thymidine incorporation in isolated islets from Reg knockout mice was decreased. When hyperplastic islets were induced by the injection of goldthioglucose, the average islet size in Reg knockout mice was significantly smaller than that of control