Evaluation of carbon flux and substrate selection through alternate pathways involving the citric acid cycle of the heart by 13C NMR spectroscopy

C. R. Malloy, A. D. Sherry, F. M H Jeffrey

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Abstract

A previous 13C NMR technique (Malloy, C.R., Sherry, A.D., and Jeffrey, F.M.H. (1987) FEBS Lett. 212, 58-62) for measuring the relative flux of molecules through the oxidative versus anaplerotic pathways involving the citric acid cycle of the rat heart has been extended to include a complete analysis of the entire glutamate 13C spectrum. Although still simple in practice, this more sophisticated model allows an evaluation of 13C fractional enrichment of molecules entering both the oxidative and anaplerotic pathways under steady-state conditions. The method was used to analyze 13C NMR spectra of intact hearts or their acid extracts during utilization of 13C-enriched pyruvate, propionate, acetate, or various combinations thereof. [2-13C]Pyruvate was used to prove that steady-state flux of pyruvate through pyruvate carboxylase is significant during co-perfusion of pyruvate and acetate, and we demonstrate for the first time that a nine-line 13C multiplet may be detected in an intact, beating heart. Acetate or pyruvate alone provided about 86% of the acetyl-CoA; in combination, about 65% of the acetyl-CoA was derived from acetate, about 30% was derived from pyruvate, and the remainder from endogenous sources. Propionate reduced the contribution of exogenous acetate to acetyl-CoA to 77% and also reduced the oxidation of endogenous substrates. Equations are presented which allow this same analysis on multiply labeled substrates, making this technique extremely powerful for the evaluation of substrate selection and relative metabolic flux through anaplerotic and oxidative pathways in the intact heart.

Original languageEnglish (US)
Pages (from-to)6964-6971
Number of pages8
JournalJournal of Biological Chemistry
Volume263
Issue number15
StatePublished - 1988

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Carbon Cycle
Citric Acid Cycle
Pyruvic Acid
Nuclear magnetic resonance spectroscopy
Magnetic Resonance Spectroscopy
Carbon
Fluxes
Acetates
Acetyl Coenzyme A
Substrates
Propionates
Nuclear magnetic resonance
Pyruvate Carboxylase
Molecules
Carbon-13 Magnetic Resonance Spectroscopy
Rats
Glutamic Acid
Perfusion
Oxidation
Acids

ASJC Scopus subject areas

  • Biochemistry

Cite this

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title = "Evaluation of carbon flux and substrate selection through alternate pathways involving the citric acid cycle of the heart by 13C NMR spectroscopy",
abstract = "A previous 13C NMR technique (Malloy, C.R., Sherry, A.D., and Jeffrey, F.M.H. (1987) FEBS Lett. 212, 58-62) for measuring the relative flux of molecules through the oxidative versus anaplerotic pathways involving the citric acid cycle of the rat heart has been extended to include a complete analysis of the entire glutamate 13C spectrum. Although still simple in practice, this more sophisticated model allows an evaluation of 13C fractional enrichment of molecules entering both the oxidative and anaplerotic pathways under steady-state conditions. The method was used to analyze 13C NMR spectra of intact hearts or their acid extracts during utilization of 13C-enriched pyruvate, propionate, acetate, or various combinations thereof. [2-13C]Pyruvate was used to prove that steady-state flux of pyruvate through pyruvate carboxylase is significant during co-perfusion of pyruvate and acetate, and we demonstrate for the first time that a nine-line 13C multiplet may be detected in an intact, beating heart. Acetate or pyruvate alone provided about 86{\%} of the acetyl-CoA; in combination, about 65{\%} of the acetyl-CoA was derived from acetate, about 30{\%} was derived from pyruvate, and the remainder from endogenous sources. Propionate reduced the contribution of exogenous acetate to acetyl-CoA to 77{\%} and also reduced the oxidation of endogenous substrates. Equations are presented which allow this same analysis on multiply labeled substrates, making this technique extremely powerful for the evaluation of substrate selection and relative metabolic flux through anaplerotic and oxidative pathways in the intact heart.",
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T1 - Evaluation of carbon flux and substrate selection through alternate pathways involving the citric acid cycle of the heart by 13C NMR spectroscopy

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AU - Jeffrey, F. M H

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N2 - A previous 13C NMR technique (Malloy, C.R., Sherry, A.D., and Jeffrey, F.M.H. (1987) FEBS Lett. 212, 58-62) for measuring the relative flux of molecules through the oxidative versus anaplerotic pathways involving the citric acid cycle of the rat heart has been extended to include a complete analysis of the entire glutamate 13C spectrum. Although still simple in practice, this more sophisticated model allows an evaluation of 13C fractional enrichment of molecules entering both the oxidative and anaplerotic pathways under steady-state conditions. The method was used to analyze 13C NMR spectra of intact hearts or their acid extracts during utilization of 13C-enriched pyruvate, propionate, acetate, or various combinations thereof. [2-13C]Pyruvate was used to prove that steady-state flux of pyruvate through pyruvate carboxylase is significant during co-perfusion of pyruvate and acetate, and we demonstrate for the first time that a nine-line 13C multiplet may be detected in an intact, beating heart. Acetate or pyruvate alone provided about 86% of the acetyl-CoA; in combination, about 65% of the acetyl-CoA was derived from acetate, about 30% was derived from pyruvate, and the remainder from endogenous sources. Propionate reduced the contribution of exogenous acetate to acetyl-CoA to 77% and also reduced the oxidation of endogenous substrates. Equations are presented which allow this same analysis on multiply labeled substrates, making this technique extremely powerful for the evaluation of substrate selection and relative metabolic flux through anaplerotic and oxidative pathways in the intact heart.

AB - A previous 13C NMR technique (Malloy, C.R., Sherry, A.D., and Jeffrey, F.M.H. (1987) FEBS Lett. 212, 58-62) for measuring the relative flux of molecules through the oxidative versus anaplerotic pathways involving the citric acid cycle of the rat heart has been extended to include a complete analysis of the entire glutamate 13C spectrum. Although still simple in practice, this more sophisticated model allows an evaluation of 13C fractional enrichment of molecules entering both the oxidative and anaplerotic pathways under steady-state conditions. The method was used to analyze 13C NMR spectra of intact hearts or their acid extracts during utilization of 13C-enriched pyruvate, propionate, acetate, or various combinations thereof. [2-13C]Pyruvate was used to prove that steady-state flux of pyruvate through pyruvate carboxylase is significant during co-perfusion of pyruvate and acetate, and we demonstrate for the first time that a nine-line 13C multiplet may be detected in an intact, beating heart. Acetate or pyruvate alone provided about 86% of the acetyl-CoA; in combination, about 65% of the acetyl-CoA was derived from acetate, about 30% was derived from pyruvate, and the remainder from endogenous sources. Propionate reduced the contribution of exogenous acetate to acetyl-CoA to 77% and also reduced the oxidation of endogenous substrates. Equations are presented which allow this same analysis on multiply labeled substrates, making this technique extremely powerful for the evaluation of substrate selection and relative metabolic flux through anaplerotic and oxidative pathways in the intact heart.

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