Endocrine Abstracts

Background: Cystic fibrosis is an autosomal recessive disease characterised by mutations in the cystic fibrosis transmembrane conductance regulator (CFTR) gene. The mutations alter fluid secretion in the lungs and digestive systems and the vast majority of patients die from pulmonary disease. CF-related diabetes (CFRD) is the most significant co-morbidity for patients with CF and accelerates lung decline. Recent evidence from animal and cell models has implicated a role for CFTR in the development, organisation and function of the endocrine pancreas and specifically, of the insulin-producing β-cell. This study will address the hypothesis that loss of functional CFTR contributes to the development of CFRD through β-cell dysfunction and apoptosis.

Methods: BRIN–BD11 cells (β-cell line of rat origin) were used for all experiments. Native CFTR was silenced using a siRNA against CFTR (Qiagen). Cell viability was assessed using an MTT assay. Acute glucose-induced insulin secretion was evaluated by exposing cells to rising D-glucose concentrations (1.1, 5.6 and 16.7 mM) for 20 min. Insulin release into the supernatants was measured by ELISA.

Results: Transfection efficiencies of 74±8.2% were achieved (n=3). MTT assays found no significant difference in cellular viability between WT and CFTR-deficient cells (n=4). WT cells displayed a dose-dependent increase in glucose-induced insulin release. While a significant difference in glucose-induced insulin secretion was not observed at basal glucose concentrations (1.1 mM glucose), CFTR-deficient cells displayed a significant impairment in insulin release in response to intermediate and stimulatory concentrations of glucose (5.6 and 16.7 mM glucose respectively), when compared with WT cells (n=4, P<0.01–0.001).

Conclusion: CFTR appears to play a significant role in the normal function of pancreatic β-cells. Future work will examine how specific CFTR mutations affect β-cell function and survival.