Reactive oxidants are generated during the metabolism of glucose and serve as important signaling messengers to trigger insulin secretion and beta cell expansion in response to elevated levels of glucose. However, chronic exposure to oxidants under hyperglycemic conditions causes chronic oxidative stress which results in cellular damage, impaired glucose-stimulated insulin secretion, and, eventually, cell death. Importantly, oxidative stress stimulates uncontrolled protein oxidation and destruction. This is further aggravated by a strong inflammatory component due to the innate immune response and formation of inflammatory mediators. We (Nissim, Strollo) previously demonstrated that most individuals with type 1 diabetes (T1D) as well as children at risk of T1D have circulating autoantibodies to oxidative post-translationally modified insulin (oxPTM-INS); we also reported that oxidized insulin epitopes stimulate both CD4+ and CD8+ T cells of individuals with T1D. While this work is suggestive that oxPTM-INS is a novel target of islet autoimmunity and a disease biomarker, we have not yet shown that oxPTM-INS is present in beta cells of human organ donors with T1D or at risk for T1D. This project aims to determine whether oxidized insulin is present in the beta cells, and to what extent, in the islets of organ donors with T1D or those with autoantibodies representing preclinical disease stages. We have developed antibody reagents to address this question. In further studies, circulating levels of oxPTM-INS neoepitopes may be also be exploited as biomarkers of beta cells stress and T1D. Antibodies against oxidized insulin may potentially be exploited to deliver therapeutic cargo to stressed beta cells, and hence the determination of the abundance of oxidized insulin in the pancreas of T1D and autoantibody-positive donors may support the development of nvoel therapeutics.
