Novel aspects of fatty acid oxidation uncovered by the combination of mass isotopomer analysis and metabolomics.
Year: 2006
Type: article
Abstract: Mass isotopomer analysis provides a wealth of information on the pathways of intermediary metabolism, and on their regulation.The tracing of single or multiple 13 C atoms in metabolites allows the identification of the fates of a given substrate and its partitioning between divergent pathways.Metabolomics, a new strategy of data-driven research, identifies unexpected correlations between areas of metabolism which are not known to interact.Therefore, metabolomics widens the field in which hypotheses can be formulated.I hypothesized that the association of metabolomics and mass isotopomer analysis could reveal the existence of unknown reactions in the metabolic fates of uniformly 13 C-labeled substrate.In my thesis research, I first compared the efficiency of various fatty acids and of dicarboxylates as precursors of peroxisomal and mitochondrial acetyl-CoA.The mass isotopomer distributions of the acetyl moiety of citrate showed that the efficiency of the contribution of C 2 -C 18 fatty acids to mitochondrial acetyl-CoA negatively correlates with the fatty acid chain length in heart.My data also revealed that octanoate undergoes one xvii cycle of peroxisomal oxidation in the heart.This was evidenced by a higher 13 C-labeling of malonyl-CoA than the acetyl of citrate.Second, I studied the competition between short and long-chain fatty acids for the supply of acetyl-CoA to the citric acid cycle.My data clearly showed that acetate strongly inhibits the degradation of oleate to acetyl-CoA in the heart.This inhibition is not mediated by an increased malonyl-CoA concentration, but very likely by the competition for free CoA between the very active acetyl-CoA synthetase and carnitine palmitoyltransferase II.Third, associating metabolomics and mass isotopomer analysis, I found evidence of a new anaplerotic pathway branching out from the metabolism of azelate, an odd chain dicarboxylate.In livers perfused with [U-13 C 9 ]azelate, the mass isotopomer distribution of selected areas of the metabolome revealed that this compound (i) is initially betaoxidized in peroxisomes, (ii) undergoes complete beta-oxidation to [U-13 C 3 ]malonyl-CoA and [U-13 C 2 ]acetyl-CoA in the mitochondria, (iii) is a major contributor to mitochondrial acetyl-CoA, and (iv) is a precursor of anaplerotic methylmalonyl-CoA.This process does not involve propionyl-CoA, the only known precursor of methylmalonyl-CoA in mammalian cells.sarcolemma acylcarnitine acyl-CoA carnitine FFA anion +
Author: Fang Bian
Institution: Case Western Reserve University
Language: English
Subfield: Biochemistry
Domain: Life Sciences
Open Access status: green
Funder: National Institutes of Health
Award: G9000105388
OpenAlex ID: W2212902690