Strategic Reduction of Hybrid Insulin Peptide Formation Significantly Delays Diabetes Onset in NOD Mice

Hybrid insulin peptides (HIPs) have been identified as targets of autoreactive T cells in type 1 diabetes, although their causal role in disease pathogenesis has remained unclear. We demonstrated that a single leucine-to-isoleucine substitution in insulin C-peptide significantly disrupts cathepsin D-mediated HIP formation in nonobese diabetic (NOD) mouse islets. NOD mice engineered with this precise modification (NOD INS2I/I) showed significantly reduced HIP content, decreased T-cell reactivity, and significantly delayed diabetes onset (43% disease-free at 1 year vs. 10% in controls). These findings establish a mechanistic link between HIP formation and disease progression, revealing cathepsin D-mediated transpeptidation as a potential therapeutic target for intervention in at-risk individuals.