title: Resolving confounding enrichment kinetics due to overlapping resonance signals from 13C-enriched long chain fatty acid oxidation and uptake within intact hearts.
abstract: OBJECTIVE
  Long chain fatty acid (LCFA) oxidation measurements in the intact heart from 13C-NMR rely on detection of 13C-enriched glutamate. However, progressive increases in overlapping resonance signal from LCFA can confound detection of the glutamate 4-carbon (GLU-C4) signal. We evaluated alternative 13C labeling for exogenous LCFA and developed a simple scheme to distinguish kinetics of LCFA uptake and storage from oxidation.
  
  
  METHODS
  Sequential 13C-NMR spectra were acquired from isolated rat hearts perfused with 13C LCFA and glucose. Spectra were evaluated from hearts supplied: U 13C LCFA, [2,4,6,8,10,12,14,16-(13) C8 ] palmitate, [2,4,6,8,10,12,14,16,18-(13) C9 ] oleate, [4,6,8,10,12,14,16-(13) C7 ] palmitate, or [4,6,8,10,12,14,16,18-(13) C8 ] oleate.
  
  
  RESULTS
  13C signal reflected the progressive enrichment at 34.6 ppm from GLU-C4, confounded by additional signal with distinct kinetics attributed to 13C-enriched LCFA 2-carbon (34.0 ppm). Excluding 13C at the 2-carbon of both palmitate and oleate eliminated signal overlap and enabled detection of the exponential enrichment of GLU-C4 for assessing LCFA oxidation.
  
  
  CONCLUSIONS
  Eliminating enrichment at the 2-carbon of 13C LCFA resolved confounding kinetics between GLU-C4 and LCFA 2-carbon signals. With this enrichment scheme, oxidation of LCFA, the primary fuel for cardiac ATP synthesis, can now be more consistently examined in whole organs with dynamic mode, proton-decoupled (13C-NMR
authors.affiliation: Program in Integrative Cardiac Metabolism, Center for Cardiovascular Research, Department of Physiology and Biophysics, University of Illinois at Chicago, College of Medicine, Chicago, Illinois, USA.
authors.forename: J Michael
authors.initials: JM
authors.lastname: O'Donnell
authors.affiliation: Program in Integrative Cardiac Metabolism, Center for Cardiovascular Research, Department of Physiology and Biophysics, University of Illinois at Chicago, College of Medicine, Chicago, Illinois, USA.
authors.forename: Matthew J
authors.initials: MJ
authors.lastname: Fasano
authors.affiliation: Program in Integrative Cardiac Metabolism, Center for Cardiovascular Research, Department of Physiology and Biophysics, University of Illinois at Chicago, College of Medicine, Chicago, Illinois, USA.
authors.forename: E Douglas
authors.initials: ED
authors.lastname: Lewandowski
mesh_terms: D000465:Algorithms; D000818:Animals; D016477:Artifacts; D066241:Carbon-13 Magnetic Resonance Spectroscopy / Q000379:methods*; D005227:Fatty Acids / Q000493:pharmacokinetics*; D018698:Glutamic Acid / Q000493:pharmacokinetics*; D000067268:Isolated Heart Preparation; D008657:Metabolic Clearance Rate; D009206:Myocardium / Q000378:metabolism*; D010084:Oxidation-Reduction; D051381:Rats; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity
chemical_list: D005227:Fatty Acids; D018698:Glutamic Acid
keywords: carbon-13; dynamic mode spectroscopy; glutamate; oleate; palmitate