Intramuscular injection of islet neogenesis-associated protein peptide stimulates pancreatic islet neogenesis in healthy dogs

Objectives: Diabetes is a serious health problem. It has been proposed that islet neogenesis from pancreatic progenitor cells may restore insulin secretion in diabetic mammals. Islet neogenesis-associated protein (INGAP) stimulates islet neogenesis; therefore, we hypothesized that it would stimulate islet neogenesis in dogs. Methods: Forty nondiabetic beagle dogs were randomly divided into 4 groups. Group I received daily intramuscular injections of vehicle, whereas the other 3 groups received daily INGAP(104-118) injections of 0.5, 1.5, or 10 mg/kg. After 30 days, pancreatic tissues were collected, and RNA and histological sections were analyzed. Results: In dogs treated with 1.5 mg/kg INGAP(104-118), there was a significant (P < 0.001) increase in the percentage of insulin-positive cells (P < 0.001) and insulin gene expression. There was a trend to increased insulin-positive cells and gene expression with treatments of 0.5 and 10 mg/kg peptide. Protein gene product 9.5-positive cells were increased with treatment. Conclusions: These results indicate that INGAP stimulates cells in the pancreatic duct epithelium of healthy dogs (putative islet progenitor cells) to develop along a neuroendocrine pathway and form new islets in response to INGAP peptide. The INGAP might be an effective therapy for diabetes.