Production of hyperpolarized <sup>13</sup>CO<inf>2</inf> from [1-<sup>13</sup>C]pyruvate in perfused liver does reflect total anaplerosis but is not a reliable biomarker of glucose production

Karlos X. Moreno, Christopher L. Moore, Shawn C. Burgess, A. Dean Sherry, Craig R. Malloy, Matthew E. Merritt

Research output: Contribution to journalArticle

7 Citations (Scopus)

Abstract

In liver, <sup>13</sup>CO<inf>2</inf> can be generated from [1-<sup>13</sup>C]pyruvate via pyruvate dehydrogenase or anaplerotic entry of pyruvate into the TCA cycle followed by decarboxylation at phosphoenolpyruvate carboxykinase (PEPCK), the malic enzyme, isocitrate dehydrogenase, or α-ketoglutarate dehydrogenase. The purpose of this study was to determine the relative importance of these pathways in production of hyperpolarized (HP) <sup>13</sup>CO<inf>2</inf> after administration of hyperpolarized pyruvate in livers supplied with a fatty acid plus substrates for gluconeogenesis. Isolated mouse livers were perfused with a mixture of thermally-polarized <sup>13</sup>C-enriched pyruvate, lactate and octanoate in various combinations prior to exposure to HP pyruvate. Under all perfusion conditions, HP malate, aspartate and fumarate were detected within ~3 s showing that HP [1-<sup>13</sup>C]pyruvate is rapidly converted to [1-<sup>13</sup>C]oxaloacetate which can subsequently produce HP <sup>13</sup>CO<inf>2</inf> via decarboxylation at PEPCK. Measurements using HP [2-<sup>13</sup>C]pyruvate allowed the exclusion of reactions related to TCA cycle turnover as sources of HP <sup>13</sup>CO<inf>2</inf>. Direct measures of O<inf>2</inf> consumption, ketone production, and glucose production by the intact liver combined with <sup>13</sup>C isotopomer analyses of tissue extracts yielded a comprehensive profile of metabolic flux in perfused liver. Together, these data show that, even though the majority of HP <sup>13</sup>CO<inf>2</inf> derived from HP [1-<sup>13</sup>C]pyruvate in livers exposed to fatty acids reflects decarboxylation of [4-<sup>13</sup>C]oxaloacetate (PEPCK) or [4-<sup>13</sup>C]malate (malic enzyme), the intensity of the HP <sup>13</sup>CO<inf>2</inf> signal is not proportional to glucose production because the amount of pyruvate returned to the TCA cycle via PEPCK and pyruvate kinase is variable, depending upon available substrates.

Original languageEnglish (US)
Pages (from-to)1144-1156
Number of pages13
JournalMetabolomics
Volume11
Issue number5
DOIs
StatePublished - Oct 7 2015

Fingerprint

Biomarkers
Pyruvic Acid
Liver
Glucose
Phosphoenolpyruvate
Decarboxylation
Oxaloacetic Acid
Oxidoreductases
Fatty Acids
Isocitrate Dehydrogenase
Fumarates
Pyruvate Kinase
Tissue Extracts
Gluconeogenesis
Metabolome
Substrates
Enzymes
Ketones
Aspartic Acid
Lactic Acid

Keywords

  • Gluconeogenesis
  • Hyperpolarization
  • Hyperpolarized <sup>13</sup>CO<inf>2</inf> production
  • Liver metabolism
  • Pyruvate cycling

ASJC Scopus subject areas

  • Biochemistry
  • Clinical Biochemistry
  • Endocrinology, Diabetes and Metabolism

Cite this

@article{170b400050654d0298fef71997289530,
title = "Production of hyperpolarized 13CO2 from [1-13C]pyruvate in perfused liver does reflect total anaplerosis but is not a reliable biomarker of glucose production",
abstract = "In liver, 13CO2 can be generated from [1-13C]pyruvate via pyruvate dehydrogenase or anaplerotic entry of pyruvate into the TCA cycle followed by decarboxylation at phosphoenolpyruvate carboxykinase (PEPCK), the malic enzyme, isocitrate dehydrogenase, or α-ketoglutarate dehydrogenase. The purpose of this study was to determine the relative importance of these pathways in production of hyperpolarized (HP) 13CO2 after administration of hyperpolarized pyruvate in livers supplied with a fatty acid plus substrates for gluconeogenesis. Isolated mouse livers were perfused with a mixture of thermally-polarized 13C-enriched pyruvate, lactate and octanoate in various combinations prior to exposure to HP pyruvate. Under all perfusion conditions, HP malate, aspartate and fumarate were detected within ~3 s showing that HP [1-13C]pyruvate is rapidly converted to [1-13C]oxaloacetate which can subsequently produce HP 13CO2 via decarboxylation at PEPCK. Measurements using HP [2-13C]pyruvate allowed the exclusion of reactions related to TCA cycle turnover as sources of HP 13CO2. Direct measures of O2 consumption, ketone production, and glucose production by the intact liver combined with 13C isotopomer analyses of tissue extracts yielded a comprehensive profile of metabolic flux in perfused liver. Together, these data show that, even though the majority of HP 13CO2 derived from HP [1-13C]pyruvate in livers exposed to fatty acids reflects decarboxylation of [4-13C]oxaloacetate (PEPCK) or [4-13C]malate (malic enzyme), the intensity of the HP 13CO2 signal is not proportional to glucose production because the amount of pyruvate returned to the TCA cycle via PEPCK and pyruvate kinase is variable, depending upon available substrates.",
keywords = "Gluconeogenesis, Hyperpolarization, Hyperpolarized <sup>13</sup>CO<inf>2</inf> production, Liver metabolism, Pyruvate cycling",
author = "Moreno, {Karlos X.} and Moore, {Christopher L.} and Burgess, {Shawn C.} and Sherry, {A. Dean} and Malloy, {Craig R.} and Merritt, {Matthew E.}",
year = "2015",
month = "10",
day = "7",
doi = "10.1007/s11306-014-0768-1",
language = "English (US)",
volume = "11",
pages = "1144--1156",
journal = "Metabolomics",
issn = "1573-3882",
publisher = "Springer New York",
number = "5",

}

TY - JOUR

T1 - Production of hyperpolarized 13CO2 from [1-13C]pyruvate in perfused liver does reflect total anaplerosis but is not a reliable biomarker of glucose production

AU - Moreno, Karlos X.

AU - Moore, Christopher L.

AU - Burgess, Shawn C.

AU - Sherry, A. Dean

AU - Malloy, Craig R.

AU - Merritt, Matthew E.

PY - 2015/10/7

Y1 - 2015/10/7

N2 - In liver, 13CO2 can be generated from [1-13C]pyruvate via pyruvate dehydrogenase or anaplerotic entry of pyruvate into the TCA cycle followed by decarboxylation at phosphoenolpyruvate carboxykinase (PEPCK), the malic enzyme, isocitrate dehydrogenase, or α-ketoglutarate dehydrogenase. The purpose of this study was to determine the relative importance of these pathways in production of hyperpolarized (HP) 13CO2 after administration of hyperpolarized pyruvate in livers supplied with a fatty acid plus substrates for gluconeogenesis. Isolated mouse livers were perfused with a mixture of thermally-polarized 13C-enriched pyruvate, lactate and octanoate in various combinations prior to exposure to HP pyruvate. Under all perfusion conditions, HP malate, aspartate and fumarate were detected within ~3 s showing that HP [1-13C]pyruvate is rapidly converted to [1-13C]oxaloacetate which can subsequently produce HP 13CO2 via decarboxylation at PEPCK. Measurements using HP [2-13C]pyruvate allowed the exclusion of reactions related to TCA cycle turnover as sources of HP 13CO2. Direct measures of O2 consumption, ketone production, and glucose production by the intact liver combined with 13C isotopomer analyses of tissue extracts yielded a comprehensive profile of metabolic flux in perfused liver. Together, these data show that, even though the majority of HP 13CO2 derived from HP [1-13C]pyruvate in livers exposed to fatty acids reflects decarboxylation of [4-13C]oxaloacetate (PEPCK) or [4-13C]malate (malic enzyme), the intensity of the HP 13CO2 signal is not proportional to glucose production because the amount of pyruvate returned to the TCA cycle via PEPCK and pyruvate kinase is variable, depending upon available substrates.

AB - In liver, 13CO2 can be generated from [1-13C]pyruvate via pyruvate dehydrogenase or anaplerotic entry of pyruvate into the TCA cycle followed by decarboxylation at phosphoenolpyruvate carboxykinase (PEPCK), the malic enzyme, isocitrate dehydrogenase, or α-ketoglutarate dehydrogenase. The purpose of this study was to determine the relative importance of these pathways in production of hyperpolarized (HP) 13CO2 after administration of hyperpolarized pyruvate in livers supplied with a fatty acid plus substrates for gluconeogenesis. Isolated mouse livers were perfused with a mixture of thermally-polarized 13C-enriched pyruvate, lactate and octanoate in various combinations prior to exposure to HP pyruvate. Under all perfusion conditions, HP malate, aspartate and fumarate were detected within ~3 s showing that HP [1-13C]pyruvate is rapidly converted to [1-13C]oxaloacetate which can subsequently produce HP 13CO2 via decarboxylation at PEPCK. Measurements using HP [2-13C]pyruvate allowed the exclusion of reactions related to TCA cycle turnover as sources of HP 13CO2. Direct measures of O2 consumption, ketone production, and glucose production by the intact liver combined with 13C isotopomer analyses of tissue extracts yielded a comprehensive profile of metabolic flux in perfused liver. Together, these data show that, even though the majority of HP 13CO2 derived from HP [1-13C]pyruvate in livers exposed to fatty acids reflects decarboxylation of [4-13C]oxaloacetate (PEPCK) or [4-13C]malate (malic enzyme), the intensity of the HP 13CO2 signal is not proportional to glucose production because the amount of pyruvate returned to the TCA cycle via PEPCK and pyruvate kinase is variable, depending upon available substrates.

KW - Gluconeogenesis

KW - Hyperpolarization

KW - Hyperpolarized <sup>13</sup>CO<inf>2</inf> production

KW - Liver metabolism

KW - Pyruvate cycling

UR - http://www.scopus.com/inward/record.url?scp=84941022690&partnerID=8YFLogxK

UR - http://www.scopus.com/inward/citedby.url?scp=84941022690&partnerID=8YFLogxK

U2 - 10.1007/s11306-014-0768-1

DO - 10.1007/s11306-014-0768-1

M3 - Article

VL - 11

SP - 1144

EP - 1156

JO - Metabolomics

JF - Metabolomics

SN - 1573-3882

IS - 5

ER -