2487-P: Loss of Mitochondrial Fuel Flexibility in Liver Sinusoidal Endothelial Cells Marks Advanced Diabetes-Related MASLD

Introduction and Objective: In type 2 diabetes, metabolic dysfunction-associated steatotic liver disease (MASLD) shows higher risk of progression to steatohepatitis (MASH) and fibrosis. We previously showed that mitochondrial respiration in sinusoidal endothelial cells (LSEC) is increased at early disease stages but declines with MASLD progression. How LSECs adapt their metabolism during disease progression remains unclear. We hypothesize that this mitochondrial flexibility is substrate-dependent and differs between fatty acid oxidation (FAO)- and tricarboxylic acid (TCA)-linked metabolism in the course of MASLD progression. Methods: Two-day-old male C57BL/6J mice received streptozotocin and were fed a high-fat diet from week 4 until week 8 or 16 to induce early or advanced diabetes-associated MASH; controls received vehicle and standard chow. Mouse LSECs were isolated by CD146-based magnetic sorting. Mitochondrial respiration was assessed by extracellular flux analysis in permeabilized cells using pyruvate or palmitate, and fuel restriction assays forcing reliance on glucose, glutamine, or fatty acids. Proteomic profiling was performed by liquid chromatography-mass spectrometry. Results: At week 8, LSECs from MASH showed increased basal respiration and mitochondrial ATP production for both TCA-linked (40-44%) and FAO-linked respiration (102-108%) compared with controls (all p0.01). At week 16, TCA-linked respiration and ATP production were reduced, whereas FAO-linked respiration was preserved. Spare respiratory capacity increased only at week 8 with forced fatty acid utilization. Proteomic analysis revealed extensive remodeling at both stages, predominantly involving lipid metabolic pathways. Conclusion: Diabetes-related MASLD exhibit enhanced mitochondrial flexibility with preferential fatty acid utilization in LSEC, whereas advanced MASH shows selective loss of TCA-linked respiration, identifying impaired endothelial fuel flexibility as feature of MASLD progression. Disclosure B. Dewidar: None. D. Ouwens: None. E. Rohbeck: None. S. Hartwig: None. M. Reina do Fundo: None. S. Lehr: None. J. Meister: None. H. Al-Hasani: None. M. Roden: Advisory Panel; Current; AstraZeneca, Boehringer Ingelheim International GmbH, Lilly, Madrigal Pharmaceuticals, Inc., Novo Nordisk, Sanofi, Echosens. Funding Grants of the German Federal Ministry for Research (BMBF) to the German Center for Diabetes Research (DZD e. V.)