title: Hyperpolarized δ-[1-13C]gluconolactone as a probe of the pentose phosphate pathway.
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 hyperpolarized13C-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 PPPoxpathway 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 PPPoxis stimulated by H2O2in glucose perfused livers but not in livers perfused with octanoate alone. Subsequent perfusion of livers with non-polarized [1,2-13C]glucose followed by1H NMR analysis of lactate in the perfusate verified that flux through the PPPoxis 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.
authors.affiliation: Advanced Imaging Research Center, UT Southwestern Medical Center, Dallas, Texas, 75390, USA.
authors.forename: Karlos X
authors.initials: KX
authors.lastname: Moreno
authors.affiliation: Advanced Imaging Research Center, UT Southwestern Medical Center, Dallas, Texas, 75390, USA.
authors.forename: Crystal E
authors.initials: CE
authors.lastname: Harrison
authors.affiliation: Advanced Imaging Research Center, UT Southwestern Medical Center, Dallas, Texas, 75390, USA.|Department of Radiology, UT Southwestern Medical Center, Dallas, Texas, 75390, USA.
authors.forename: Matthew E
authors.initials: ME
authors.lastname: Merritt
authors.affiliation: Advanced Imaging Research Center, UT Southwestern Medical Center, Dallas, Texas, 75390, USA.
authors.forename: Zoltan
authors.initials: Z
authors.lastname: Kovacs
authors.affiliation: Advanced Imaging Research Center, UT Southwestern Medical Center, Dallas, Texas, 75390, USA.|Department of Radiology, UT Southwestern Medical Center, Dallas, Texas, 75390, USA.|Department of Internal Medicine, UT Southwestern Medical Center, Dallas, Texas, 75390, USA.|VA North Texas Health Care System, Dallas, Texas, 75216, USA.
authors.forename: Craig R
authors.initials: CR
authors.lastname: Malloy
authors.affiliation: Advanced Imaging Research Center, UT Southwestern Medical Center, Dallas, Texas, 75390, USA.|Department of Radiology, UT Southwestern Medical Center, Dallas, Texas, 75390, USA.|Department of Chemistry, University of Texas at Dallas, Richardson, Texas, 75083, USA.
authors.forename: A Dean
authors.identifier: 0000-0001-7150-8301
authors.initials: AD
authors.lastname: Sherry
mesh_terms: D000818:Animals; D066241:Carbon-13 Magnetic Resonance Spectroscopy; D005942:Gluconates / Q000737:chemistry / Q000378:metabolism*; D005947:Glucose / Q000494:pharmacology; D007328:Insulin / Q000494:pharmacology; D007783:Lactones / Q000737:chemistry / Q000378:metabolism*; D008099:Liver / Q000187:drug effects / Q000378:metabolism; D051379:Mice; D010427:Pentose Phosphate Pathway; D013997:Time Factors
chemical_list: D005942:Gluconates; D007328:Insulin; D007783:Lactones; D005947:Glucose; C010730:beta-glucono-1,5-lactone
keywords: 13C NMR; dynamic nuclear polarization; isolated mouse liver; lactone metabolism; pentose phosphate pathway