Translational Metabolism Research Laboratory

Excess fat intake can increase lipid oxidation and expression of mitochondrial proteins, indicating remodeling of the mitochondrial proteome. Yet intermediates of lipid oxidation also accumulate and indicate a relative insufficiency to completely oxidize lipids. We investigated remodeling of the mitochondrial proteome to determine mechanisms of changes to lipid oxidation following high-fat feeding. C57BL/6J mice consumed either a high-fat diet (HFD, 60% fat from lard) or low fat diet (LFD, 10% fat) for 12 weeks. Mice were fasted 4 hours then anaesthetized by sodium pentobarbital for tissue collection. A mitochondrial-enriched fraction was prepared from gastrocnemius muscles and underwent proteomic analysis by high-resolution mass spectrometry. Mitochondrial respiratory efficiency was measured as ATP production per oxygen consumption (P:O). Intramuscular acyl-carnitines were measured by liquid-chromatography mass spectrometry. A total of 658 mitochondrial proteins were identified with 40 having higher and 14 having lower abundance in mice consuming a HFD compared to LFD. Individual proteins that changed with HFD were primarily related to β-oxidation with fewer changes to the electron transfer system. Gene set enrichment analysis identified HFD increased pathways of lipid metabolism and β-oxidation. Intramuscular concentrations of select acyl-carnitines (C18:0) were greater with HFD and reflected dietary lipid composition. Mitochondrial respiratory P:O for lipids was not different between LFD and HFD. Following the 60% fat diet, remodeling of the mitochondrial proteome revealed up-regulation of proteins regulating lipid oxidation that was not evident for all mitochondrial pathways. The accumulation of lipid metabolites with obesity may occur without intrinsic dysfunction to mitochondrial lipid oxidation.