Reduced peroxisomal function increases insulin secretion, promotes insulin oxidation, and impairs β cell maturity

Given the central role of peroxisomes in lipid metabolism and redox homeostasis, we hypothesized that peroxisomal activity is critical for sustaining β cell function and identity. Pex5 deletion models were employed to investigate loss of peroxisomal function on glucose-stimulated insulin secretion (GSIS), oxidative stress, and β cell maturity markers. Peroxisome deficiency in male mice resulted in elevated GSIS. Glucose intolerance developed despite increased insulin secretion. Ion mobility mass spectrometry revealed oxidation of insulin proteins, and a truncated insulin 2-derived peptide, in islets from mice with a tissue-specific deficiency in peroxisomes. Peroxisome loss of function increased multiple markers of oxidative stress, including altered metabolite profiles, lipid peroxidation, and protein carbonylation. These findings reveal that increased secretion of oxidized insulin protein is insufficient to regulate whole-body glucose homeostasis. Peroxisome deficiency also reduced markers of β cell maturity. Based on these outcomes, we identified the peroxisome organelle as a key regulatory component of glucose homeostasis by protecting insulin from oxidative modification and degradation and by supporting maintenance of mature β cells.