1279-OR: Targeting Complex I-Reverse Electron Transport Protects against Palmitic Acid–Induced Endothelial Dysfunction

Introduction and Objective: Lipotoxicity causes diabetic vascular injury. While mitochondrial ROS (mtROS) are key, the role of complex I reverse electron transport (RET) is unclear. We aimed to define RET's mechanistic role. Methods: We used palmitic acid (PA)-treated endothelial cells and high-fat diet (HFD)-fed mice. Assays included mtROS, NAD+/NADH, metabolism, and RNA-seq. RET was probed using rotenone and NDUFS4 knockdown. Results: PA caused endothelial dysfunction (↑mtROS, ↓angiogenesis, inflammation). Transcriptomics showed downregulated vascular genes and activated inflammatory pathways. PA lowered NAD+/NADH and upregulated NDUFS4, promoting complex I-RET. Inhibiting RET (rotenone or NDUFS4 knockdown) suppressed mtROS, restored NAD+/NADH balance, and rescued endothelial function. Glycolysis/TCA suppression persisted post-inhibition, indicating metabolic-function dissociation. In vivo, rotenone reduced HFD-induced vascular oxidative stress and improved endothelial integrity and angiogenesis. Conclusion: Complex I-mediated RET is a major driver of lipotoxic endothelial injury. RET inhibition rescues endothelial health despite ongoing metabolic reprogramming, identifying it as a distinct therapeutic target for diabetic vascular complications. Disclosure C. Zhou: None. D. Chen: None. R. Li: None. Z. Li: None. J. Song: None. Funding the Special Care Program for Obesity in Pudong Health Bureau of Shanghai (PWYq2025-01) and Academic Leaders Training Program of Pudong Health Bureau of Shanghai (PWRd2023-03)