ESPE Abstracts

Backgound: There is insufficient knowledge about the characterisation of insulin, glucagon, amylin, pancreatic polypeptide (PP) and Pancreas/Duodenum Homeobox Protein 1 (PDX-1) in pancreatic tissue of children with diffuse (DCHI) and focal (FCHI) congenital hyperinsulinism (CHI).

Objective(s): To understand the expression profile and localisation of insulin, glucagon, amylin, PP and PDX-1 in pancreatic tissue of children with DCHI and FCHI.

Methods: Human paediatric pancreatic samples from normal (N: 2), FCHI (N: 2) and DCHI (N: 2) were obtained. For localisation of hormones, same-slide double staining immunohistochemistry was performed and images visualised under fluorescent microscopy. PDX-1 was chosen as a marker of endocrine tissue as it stains the nuclei of β-cells. Gene expression was analysed with SybrGreen quantitative Real-Time polymerase chain reaction (RTqPCR) in the same groups. RPL19 was used as the endogenous control gene.

Results: Immunohistochemistry did not show differences in localisation of the 5 peptides between controls, FCHI and DCHI. Amylin stains the same cells as PDX-1 in normal and all forms of CHI, therefore limited to the endocrine component of the pancreas. In all three groups of patients, insulin and amylin had a different distribution within the β-cell so they did not co-localise. In CHI tissue, amylin shows comparable fluorescence to controls, and so does PP that is localised in scarce amount in the islets. Gene expression studies (RTqPCR) showed higher expression of insulin and lower of glucagon in all CHI forms, as compared to controls; consistent with known plasma hormone concentrations. In CHI forms, the expression of amylin and PDX-1 do not parallel that of insulin. PP expression is comparable in controls and all CHI cases. Gene expression of both amylin and PP, demonstrated high variability between DCHI subjects, compared to FCHI and normal pancreas.

Conclusions: As opposed to previous reports in the literature that had not used same-slide double staining, our study shows no co-localisation of amylin and insulin in the β-cell. Localisation and expression of amylin in CHI is independent to that of insulin, potentially indicating a β-cell preserved mechanism to minimise hypoglycaemia. Based on the expression studies PP may not have an important role in glucose regulation in CHI.