CONICET | Buscador de Institutos y Recursos Humanos

Background/Aims: Islet neogenesis-associated protein (INGAP) enhances insulin secretion elicited by several secretagogues, induces islet neogenesis and reduces β-cell apoptosis. Here we investigate the potential physiological modulatory role of INGAP in insulin secretion using two different mechanistic experimental approaches. Methods: Islets isolated from normal male hamsters were cultured for 4 days and transfected either with INGAP-small interfering RNA (INGAP-siRNA) or with a non-targeting siRNA carrying green-fluorescence-protein (GFP). Transfection efficiency was checked by fluorescence microscopy (GFP detection) and by measuring INGAP expression (real-time PCR). Both groups of islets were thereafter incubated with 3.3 or 16.7 mmol/L glucose. In another set of experiments, freshly isolated islets from normal hamsters were incubated with low and high glucose in the presence of the same concentration of either a specific anti-INGAP rabbit serum or normal rabbit serum in the medium. In both cases, insulin in the medium was measured by RIA. Results: Non-targeting GFP-siRNA was present only in cells located in the periphery of whole transfected islets, precisely in cells immunostained with the specific INGAP antibody. INGAP mRNA decreased by 35.4% in INGAP-siRNA transfected islets and released 40% less insulin than control islets in response to 16.7 mmol/L glucose. INGAP antibody in the medium also decreased significantly (37%) the high glucose-induced insulin secretion. Conclusion: These results indicate that INGAP would play a physiological and positive modulatory role in insulin secretion; thus, its addition to islets maintained in culture previous to their transplant could optimize their secretory function. Conclusion: These results indicate that INGAP would play a physiological and positive modulatory role in insulin secretion; thus, its addition to islets maintained in culture previous to their transplant could optimize their secretory function.