Contribution of various substrates to total citric acid cycle flux and anaplerosis as determined by13C isotopomer analysis and O2 consumption in the heart

Craig R Malloy, John G. Jones, F. Mark Jeffrey, Michael E Jessen, Dean Sherry

Research output: Contribution to journalArticlepeer-review

64 Scopus citations


A simple relationship between parameters derived from a 13C NMR isotopomer analysis and O2 consumption is presented that allows measurement of the absolute rate of acetyl-CoA oxidation and anaplerotic flux in tissues oxidizing a mixture of four substrates. The method was first applied in a study of the effects of work state and β-adrenergic stimulation on net acetate oxidation and anaplerosis in the isolated working rat heart. The results demonstrate that the anticipated ratio of 2 between O2 consumption and TCA cycle flux for hearts oxidizing only acetate holds at low workload when anaplerosis is low, but deviates toward a factor of 3 under high workload conditions when anaplerosis is increased. This analysis was also extended to hearts that oxidize a more physiological mixture of substrates including long-chain fatty acids, acetoacetate, lactate, pyruvate, and glucose. We show that the contribution each substrate makes to total TCA cycle flux can be determined by combined 13C NMR and O2 consumption measurements. The present study also demonstrates that stimulation of anaplerosis (by addition of propionate) can significantly alter the relative contribution each substrate makes to total TCA cycle flux. We conclude that if 13C labeling patterns are selected appropriately, a comprehensive picture of flux through all major metabolic pathways feeding the cycle can be determined in a single experiment even when complex physiological mixtures of substrates are provided.

Original languageEnglish (US)
Pages (from-to)35-46
Number of pages12
JournalMagnetic Resonance Materials in Physics, Biology and Medicine
Issue number1
StatePublished - 1996


  • C NMR isotopomer analysis
  • Heart metabolism
  • Krebs citric acid cycle
  • Oconsumption

ASJC Scopus subject areas

  • Biophysics
  • Radiological and Ultrasound Technology
  • Radiology Nuclear Medicine and imaging


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