2686-P: Protein Carbonylation Impairs DNA Damage Response in Beta Cells in Type 2 Diabetes

Introduction and Objective: Type 2 diabetes (T2D) is characterized by a loss of functional β-cell mass driven by mechanisms that remain incompletely understood. Oxidative stress, to which β-cells are particularly vulnerable due to low antioxidant capacity, leads to accumulation of reactive lipid aldehydes such as 4-hydroxynonenal (4HNE), which is increased in human islets from T2D donors or in islets exposed to glucolipotoxic conditions. These aldehydes can covalently attach to proteins through protein carbonylation, causing protein dysfunction. However, the identity of carbonylated proteins in human islets under basal and diabetic conditions remains unknown. This study aims to identify carbonylated proteins in T2D human islets and determine their contribution to the loss of functional β-cell mass in T2D. Methods: Islets from T2D and non-diabetic (ND) human donors (n=3/condition) were collected. Carbonylated proteins were enriched using biotin hydrazide and identified by label-free LC-MS/MS. Protein carbonylation profiles were compared between T2D and ND islets. Results: We identified 197 proteins that were significantly more carbonylated in T2D islets compared with ND islets (p<0.05). Pathway analysis identified DNA damage response (DDR) as the major target of protein carbonylation in T2D islets. We uncovered Damage-specific DNA binding protein 1 (DDB1) and structural maintenance of chromosomes 3 (SMC3), whose inactivation has been associated with β-cell dysfunction in diabetes, as two of the top carbonylated DDR proteins. Increased DDR protein carbonylation was also observed in MIN6 β-cells exposed to 4HNE, and human islets exposed to 4-HNE exhibit increased DNA damage (γH2AX marker) in β-cells (8-fold vs. control). Conclusion: DDR is a vital cellular process that detects DNA damage, halts the cell cycle, signals for repair, and triggers cell death if damage is too severe. Our findings suggest that carbonylation modifies DDR proteins which can participate in the reduced functional β-cell mass observed in T2D. Future therapeutics should target protein carbonylation to reduce β-cell dysfunction in diabetes. Disclosure A.C. Ling: None. C.T. Shearn: None. S. Bhattacharya: None. S. Dhawan: None. S. Shuck: None. J. Knight: None. S. Baumel-Alterzon: None. Funding National Institutes of Health (K01DK128387)