Hyperpolarized 13C allows a direct measure of flux through a single enzyme-catalyzed step by NMR

Matthew E. Merritt, Crystal Harrison, Charles Storey, F. Mark Jeffrey, A. Dean Sherry, Craig R. Malloy

Research output: Contribution to journalArticlepeer-review

209 Scopus citations

Abstract

13C NMR is a powerful tool for monitoring metabolic fluxes in vivo. The recent availability of automated dynamic nuclear polarization equipment for hyperpolarizing 13C nuclei now offers the potential to measure metabolic fluxes through select enzyme-catalyzed steps with substantially improved sensitivity. Here, we investigated the metabolism of hyperpolarized [1-13C1]pyruvate in a widely used model for physiology and pharmacology, the perfused rat heart. Dissolved 13CO2, the immediate product of the first step of the reaction catalyzed by pyruvate dehydrogenase, was observed with a temporal resolution of ≈1 s along with H13CO3-, the hydrated form of 13CO2 generated catalytically by carbonic anhydrase. In hearts presented with the medium-chain fatty acid octanoate in addition to hyperpolarized [1-13C1]pyruvate, production of 13CO2 and H13CO3- was suppressed by ≈90%, whereas the signal from [1-13C 1]lactate was enhanced. In separate experiments, it was shown that O2 consumption and tricarboxylic acid (TCA) cycle flux were unchanged in the presence of added octanoate. Thus, the rate of appearance of 13CO2 and H13CO3- from [1-13C1]pyruvate does not reflect production of CO 2 in the TCA cycle but rather reflects flux through pyruvate dehydrogenase exclusively.

Original languageEnglish (US)
Pages (from-to)19773-19777
Number of pages5
JournalProceedings of the National Academy of Sciences of the United States of America
Volume104
Issue number50
DOIs
StatePublished - Dec 11 2007

Keywords

  • Carbon dioxide
  • Heart
  • Hyperpolarization
  • NMR spectroscopy
  • Pyruvate

ASJC Scopus subject areas

  • General

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