Hyperpolarized δ-[1-13C]gluconolactone as a probe of the pentose phosphate pathway

Karlos X. Moreno, Crystal E. Harrison, Matthew E. Merritt, Zoltan Kovacs, Craig R. Malloy, A. Dean Sherry

Research output: Contribution to journalArticle

7 Scopus citations

Abstract

The pentose phosphate pathway (PPP) is thought to be upregulated in trauma (to produce excess NADPH) and in cancer (to provide ribose for nucleotide biosynthesis), but simple methods for detecting changes in flux through this pathway are not available. MRI of hyperpolarized 13C-enriched metabolites offers considerable potential as a rapid, non-invasive tool for detecting changes in metabolic fluxes. In this study, hyperpolarized δ-[1-13C]gluconolactone was used as a probe to detect flux through the oxidative portion of the pentose phosphate pathway (PPPox) in isolated perfused mouse livers. The appearance of hyperpolarized (HP) H13CO3 - within seconds after exposure of livers to HP-δ-[1-13C]gluconolactone demonstrates that this probe rapidly enters hepatocytes, becomes phosphorylated, and enters the PPPox pathway to produce HP-H13CO3 - after three enzyme catalyzed steps (6P-gluconolactonase, 6-phosphogluconate dehydrogenase, and carbonic anhydrase). Livers perfused with octanoate as their sole energy source show no change in production of H13CO3 - after exposure to low levels of H2O2, while livers perfused with glucose and insulin showed a twofold increase in H13CO3 - after exposure to peroxide. This indicates that flux through the PPPox is stimulated by H2O2 in glucose perfused livers but not in livers perfused with octanoate alone. Subsequent perfusion of livers with non-polarized [1,2-13C]glucose followed by 1H NMR analysis of lactate in the perfusate verified that flux through the PPPox is indeed low in healthy livers and modestly higher in peroxide damaged livers. We conclude that hyperpolarized δ-[1-13C]gluconolactone has the potential to serve as a metabolic imaging probe of this important biological pathway.

Original languageEnglish (US)
JournalNMR in Biomedicine
DOIs
StateAccepted/In press - 2017

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Keywords

  • C NMR
  • Dynamic nuclear polarization
  • Isolated mouse liver
  • Lactone metabolism
  • Pentose phosphate pathway

ASJC Scopus subject areas

  • Molecular Medicine
  • Radiology Nuclear Medicine and imaging
  • Spectroscopy

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