Exp Clin Endocrinol Diabetes 2007; 115 - P02_038
DOI: 10.1055/s-2007-972445

Glucose-dependent expansion of pancreatic beta-cells by the protein p8 in vitro and in vivo

G Päth 1, A Opel 2, M Gehlen 2, V Rothhammer 2, X Niu 1, C Limbert 1, L Romfeld 2, S Hügl 2, A Knoll 2, MD Brendel 3, RG Bretzel 3, J Seufert 1
  • 1University Hospital of Freiburg, Division of Endocrinology and Diabetology, Department of Internal Medicine II, Freiburg, Germany
  • 2University Hospital of Würzburg, Division of Metabolism, Endocrinology and Molecular Medicine, Department of Internal Medicine I, Würzburg, Germany
  • 3University Hospital of Gießen and Marburg, Department of Internal Medicine III, Gießen, Germany

Objectives: p8 protein expression is upregulated during pancreatitis in the exocrine pancreas. Since own previous work detected p8 expression also in endocrine pancreatic beta-cells, we here investigate the role of p8 in beta-cell proliferation.

Methods: RT-PCR, Western blot, IPTG-inducible p8 overexpression in INS-1 beta-cells (p8-INS1), adenoviral p8 overexpression in human pancreatic islets, BrdU incorporation (proliferation), ELISA (insulin and C-peptide), and transplantation of human pancreatic islets into streptozotocin (STZ)-diabetic mice.

Results: Glucose-induced INS-1 beta-cell expansion is preceded by p8 protein expression. IPTG-induced p8 overexpression in p8-INS1 beta-cells enhances cell proliferation and expansion in the presence of glucose only. This is accompanied by slightly decreased beta-cell-related gene expression (PDX-1, proinsulin I, GLUT2, glucokinase, amylin) and function (insulin content and secretion). But removal of IPTG reverses beta-cell function within 24h to normal levels and IPTG-pretreated p8-INS1 beta-cells demonstrate fully functional insulin response to 0–25 mM glucose. Further, adenovirally transduced p8 overexpression in primary human pancreatic islets increases proliferation, expansion, and cumulative insulin secretion in vitro. Transplantation of mock-transduced control islets under the kidney capsule of immunosuppressed STZ-diabetic mice reduces blood glucose and increases human C-peptide serum concentrations to stable levels after 3 days. In contrast, transplantation of equal numbers of p8-transduced islets results in a continuous decrease of blood glucose and increase of human C-peptide beyond 3 days indicating p8-induced expansion of transplanted human beta-cells in vivo. This is underlined by a doubling of insulin content in kidneys containing p8-transduced islet grafts explanted on day 9.

Conclusions: These results establish p8 as a novel molecular mediator of glucose-induced pancreatic beta-cell expansion in vitro and in vivo and support the notion of existing beta-cell replication in the adult organism.