Short-term effects of INGAP and Reg family peptides on the appearance of small β-cells clusters in non-diabetic mice

Islets. 2012 Jan-Feb;4(1):40-8. doi: 10.4161/isl.18659. Epub 2012 Jan 1.

Abstract

The Reg3 peptides INGAP-PP and human Reg3α/β (HIP) have been hypothesized to stimulate β-cell neogenesis in the pancreas. Administration of INGAP-PP has been shown to cause an increase in β-cell mass in multiple animal models, reverse streptozotocin (STZ) induced diabetes in mice and reduces HbA1c levels in type 2 diabetic humans. In this study, we have examined the ability of the INGAP-PP and HIP peptides to induce β-cell formation in vivo in normal mice through short-term administration of the peptides. We assessed the peptides ability to induce an increase in extra-islet insulin-positive cell clusters by looking at β-cell number by point counting morphometry on pancreata that had been randomized using the smooth fractionator principle in non-diabetic NMRI mice after short-term injections of the peptides (5 d). Five day continuous BrdU labeling was used to determine if the new β-cells were derived from replicating β-cells. Real time quantitative RT-PCR and immuno-histochemistry was used to analyze changes in pancreatic transcription factor expression. A 1.5- to 2-fold increase in the volume of small extra-islet insulin-positive clusters post 5 d treatment with INGAP-PP and HIP as compared with mice treated with a non-peptide control or scrambled peptide (p<0.05) (n = 7) was found. Five day continuous BrdU infusion during the 5 d period showed little or no incorporation in islets or small insulin clusters. Five days of treatment with INGAP-PP or HIP, showed a tendency toward increased levels of pancreatic progenitor markers such as Ngn3, Nkx6.1, Sox9 and Ins. These are the first studies to compare and indicate that the human Reg3 α/β (HIP) peptide has similar bioactivity in vivo as INGAP by causing formation of small β-cell clusters in extra-islet pancreatic tissue after only 5 d of treatment. Upregulation of pancreatic transcription factors may be part of the mechanism of action.

Keywords: INGAP; Reg3; insulin; ngn3; regeneration; sox9; transcription factors.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Antigens, Neoplasm / pharmacology*
  • Basic Helix-Loop-Helix Transcription Factors / analysis
  • Basic Helix-Loop-Helix Transcription Factors / genetics
  • Biomarkers, Tumor / pharmacology*
  • Cell Count
  • Female
  • Gene Expression
  • Homeodomain Proteins / analysis
  • Homeodomain Proteins / genetics
  • Insulin / analysis
  • Insulin / genetics
  • Insulin-Secreting Cells / chemistry
  • Insulin-Secreting Cells / cytology*
  • Insulin-Secreting Cells / drug effects*
  • Lectins, C-Type
  • Mice
  • Nerve Tissue Proteins / analysis
  • Nerve Tissue Proteins / genetics
  • Pancreatitis-Associated Proteins
  • SOX9 Transcription Factor / analysis
  • SOX9 Transcription Factor / genetics
  • Time Factors
  • Transcription Factors / analysis
  • Up-Regulation

Substances

  • Antigens, Neoplasm
  • Basic Helix-Loop-Helix Transcription Factors
  • Biomarkers, Tumor
  • Homeodomain Proteins
  • Insulin
  • Lectins, C-Type
  • Nerve Tissue Proteins
  • Neurog3 protein, mouse
  • Nkx6-1 protein, mouse
  • Pancreatitis-Associated Proteins
  • REG3A protein, human
  • SOX9 Transcription Factor
  • Sox9 protein, mouse
  • Transcription Factors