Proceedings of The Physiological Society

University of Manchester (2010) Proc Physiol Soc 19, PC292

Poster Communications

Differences in islets architecture in focal and diffuse forms of congenital hyperinsulinism

M. S. Skae1,2, I. Banerjee2, R. Amin2, L. Patel2, C. M. Hall2, P. E. Clayton2,3, M. J. Dunne1, K. Cosgrove1

1. Faculty of Life Sciences, University of Manchester, Manchester, United Kingdom. 2. Paediatric Endocrinology and Diabetes, Royal Manchester Children's Hospital, Manchester, United Kingdom. 3. Faculty of Medicine and Human Sciences, University of Manchester, Manchester, United Kingdom.

Congenital Hyperinsulinism (CHI) is a disorder of dysregulated insulin release and recurrent hypoglycaemia caused by mutations in ABCC8 or KCNJ11 genes encoding subunits of ATP-sensitive potassium (KATP) channels. The pathology of CHI is subdivided into focal or diffuse disease; the former characterized by islet cell proliferation with normal nuclei and the latter showing islet cell hyperplasia and enlarged nuclei. It has been recently shown that the architecture of endocrine cells within islets is different in rodent and human islets1. We aimed to study the distribution of α- and β-cells in islet tissue isolated from patients with focal or diffuse CHI. Resected pancreatic tissue from 10 patients with focal or diffuse CHI was collected and prepared for histological procedures. α- and β-cells were identified by standard immunofluorescence (IF) protocols using glucagon and insulin antibodies. To quantify differences in islet cell distributions, IF images were analyzed for antibody optical density (OD) values across the diameter of multiple individual islets using ImageJ software. To compare OD values quantitatively between islet peripheries and central core areas, OD values across each islet were divided into quartiles and averaged. Data are expressed as mean ± SEM. KATP channel mutations were identified in 9/10 patients (7 ABCC8, 2 KCNJ11). 5 patients had focal disease and 5 patients had diffuse CHI. IF image analysis showed insulin-positive β-cells distributed throughout islets in all patients with no differences between OD values of insulin staining between core and peripheral islet regions (n=30 islets from 10 patients). However, differences in distributions of glucagon-positive α-cells were noted. In focal tissue, mean glucagon OD values for islet core areas were significantly lower than in islet peripheries (18.1±2.7 vs. 30.0±5.1 OD units; Student’s paired t-test; p<0.001; n=12 islets) demonstrating predominant α-cell distributions in islet peripheries. In diffuse cases of CHI α-cells were distributed similarly (54.2±5.5 vs. 66.1±7.5 OD units for core vs periphery respectively; Student’s paired t-test; p<0.05; n=15 islets). Comparison of the ratios of peripheral:core OD values between focal and diffuse tissue revealed a more marked pattern of peripheral α-cell distribution in the focal tissue (1.8±0.2 vs 1.2±0.1 for focal vs diffuse respectively; Student’s t-test p<0.01; n= 12 and n=15 for focal and diffuse respectively). Our data indicate that in contrast to control human islets, glucagon producing α-cells have a peripheral islet distribution in CHI tissue. This finding may reflect differences in the ontogeny of pancreatic islet cell development in CHI and could have functional consequences in glucose counter-regulatory responses.

Where applicable, experiments conform with Society ethical requirements