In vivo assessment of intracellular redox state in rat liver using hyperpolarized [1- 13 C]Alanine

Magn Reson Med. 2017 May;77(5):1741-1748. doi: 10.1002/mrm.26662. Epub 2017 Mar 5.

Abstract

Purpose: The intracellular lactate to pyruvate concentration ratio is a commonly used tissue assay biomarker of redox, being proportional to free cytosolic [NADH]/[NAD+ ]. In this study, we assessed the use of hyperpolarized [1-13 C]alanine and the subsequent detection of the intracellular products of [1-13 C]pyruvate and [1-13 C]lactate as a useful substrate for assessing redox levels in the liver in vivo.

Methods: Animal experiments were conducted to measure in vivo metabolism at baseline and after ethanol infusion. A solution of 80-mM hyperpolarized [1-13 C]alanine was injected intravenously at baseline (n = 8) and 45 min after ethanol infusion (n = 4), immediately followed by the dynamic acquisition of 13 C MRS spectra.

Results: In vivo rat liver spectra showed peaks from [1-13 C] alanine and the products of [1-13 C]lactate, [1-13 C]pyruvate, and 13 C-bicarbonate. A significantly increased 13 C-lactate/13 C-pyruvate ratio was observed after ethanol infusion (8.46 ± 0.58 at baseline versus 13.58 ± 0.69 after ethanol infusion; P < 0.001) consistent with the increased NADH produced by liver metabolism of ethanol to acetaldehyde and then acetate. A decrease in 13 C-bicarbonate production was also noted, potentially reflecting ethanol-induced mitochondrial redox changes.

Conclusion: A method to measure in vivo tissue redox using hyperpolarized [1-13 C]alanine is presented, with the validity of the proposed 13 C-pyruvate/13 C-lactate metric tested using an ethanol challenge to alter liver redox state. Magn Reson Med 77:1741-1748, 2017. © 2017 International Society for Magnetic Resonance in Medicine.

Keywords: alanine; dynamic nuclear polarization; hyperpolarized; liver; redox.

Publication types

  • Research Support, Non-U.S. Gov't
  • Research Support, N.I.H., Extramural

MeSH terms

  • Alanine / chemistry*
  • Animals
  • Carbon Isotopes / chemistry*
  • Cytosol / metabolism
  • Ethanol / chemistry
  • Liver / diagnostic imaging*
  • Liver / physiology*
  • Magnetic Resonance Imaging
  • Magnetic Resonance Spectroscopy
  • Male
  • Mitochondria / metabolism
  • Oxidation-Reduction*
  • Oxygen / chemistry
  • Positron-Emission Tomography
  • Pyruvic Acid / chemistry
  • Rats
  • Rats, Wistar
  • Reproducibility of Results

Substances

  • Carbon Isotopes
  • Ethanol
  • Pyruvic Acid
  • Alanine
  • Oxygen