Oxidative stress and impaired insulin secretion in cystic fibrosis pig pancreas

Cystic fibrosis-related diabetes (CFRD) is one the most common comorbidities in cystic fibrosis (CF). Pancreatic oxidative stress has been postulated in the pathogenesis of CFRD, but no studies have been done to show an association. The main obstacle is the lack of suitable animal models and no immediate availability of pancreas tissue in humans. In the CF porcine model, we found increased pancreatic total glutathione (GSH), glutathione disulfide (GSSG), 3-nitrotyrosine- and 4-hydroxynonenal-modified proteins, and decreased copper zinc superoxide dismutase (CuZnSOD) activity, all indicative of oxidative stress. CF pig pancreas demonstrated increased DHE oxidation (as a surrogate marker of superoxide) in situ compared to non-CF and this was inhibited by a SOD-mimetic (GC4401). Catalase and glutathione peroxidase activities were not different between CF and non-CF pancreas. Isolated CF pig islets had significantly increased DHE oxidation, peroxide production, reduced insulin secretion in response to high glucose and diminished secretory index compared to non-CF islets. Acute treatment with apocynin or an SOD mimetic failed to restore insulin secretion. These results are consistent with the hypothesis that CF pig pancreas is under significant oxidative stress as a result of increased O₂^●− and peroxides combined with reduced antioxidant defenses against reactive oxygen species (ROS). We speculate that insulin secretory defects in CF may be due to oxidative stress.