Islet Function in the Pathogenesis of Cystic Fibrosis-Related Diabetes Mellitus

Cystic fibrosis-related diabetes mellitus (CFRD) is the most common non-pulmonary co-morbidity in cystic fibrosis (CF). CF is caused by mutations in the cystic fibrosis transmembrane conductance regulator gene (CFTR), which leads to aberrant luminal fluid secretions in organs such as the lungs and pancreas. How dysfunctional CFTR leads to CFRD is still under debate. Both intrinsic effects of dysfunctional CFTR in hormone secreting cells of the islets and effects of exocrine damage have been proposed. In the current review, we discuss these non-mutually exclusive hypotheses with a special focus on how dysfunctional CFTR in endocrine cells may contribute to an altered glucose homeostasis. We outline the proposed role of CFTR in the molecular pathways of beta-cell insulin secretion and alpha-cell glucagon secretion, and touch upon the importance of the exocrine pancreas and intra-pancreatic crosstalk for proper islet function.