249-LB: Effects of Oxidative Phosphorylation Complex Defects on Beta-Cell Biology

Abstract

Background: The insulin-secreting pancreatic beta cell is a highly metabolic cell type relying on mitochondrial metabolism for stimulus-secretion coupling. Specifically, the ATP-producing oxidative phosphorylation (OXPHOS) pathway is central to insulin secretion. Although disruptions in ATP production occur in beta cell dysfunction, the exact mechanisms remain unknown. We have generated beta cell specific OXPHOS complex inducible knock out mouse models of Complex I, III, and IV to determine the direct effects OXPHOS complexes on beta cell function. We hypothesize that individual complexes contribute distinctly to beta cell function. Methods: Eight-week-old, male OXPHOSf/f - MIPcreERT mice were administered tamoxifen (150mg/kg) or vehicle by I.P. injection for 5 consecutive days. Non-fasting glycemia and body weight were measured one week prior and once per week up to 5 weeks after induction. Glucose tolerance was assessed by glucose tolerance tests (IP-GTT) 1 week before and 3 weeks after induction for all groups. Mice were anesthetized with ketamine/xylazine and perfused with sterile PBS followed by 4% PFA. Pancreata were dissected, embedded in OCT, and cut at 40µM sections for immunofluorescent staining of insulin, glucagon, and somatostatin. Results: No changes in body weight were observed throughout the experimental period for any group. Complex III knockout animals developed severe hyperglycemia and significant glucose intolerance at 3 weeks after induction. Although the other models display a minor trend towards hyperglycemia starting at 5 weeks after induction, they retain their ability to regulate glucose at 3 weeks as seen by IP-GTT. Interestingly, no changes in islet cytoarchitecture are observed in any of the groups at the 3-week timepoint. Conclusions: Mice with Complex III deficient beta cells show a robust diabetic phenotype compared to Complex I and IV models. These results support the hypothesis that specific OXPHOS complexes contribute differentially to beta cell function. Disclosure A.L. Lang: None. A. Caicedo: None. Funding National Institute of Environmental Health Sciences (R21ES025673-01)