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Resolving confounding enrichment kinetics due to overlapping resonance signals from 13 C‐enriched long chain fatty acid oxidation and uptake within intact hearts
Author(s) -
O'Donnell J. Michael,
Fasano Matthew J.,
Lewandowski E. Douglas
Publication year - 2015
Publication title -
magnetic resonance in medicine
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.696
H-Index - 225
eISSN - 1522-2594
pISSN - 0740-3194
DOI - 10.1002/mrm.25446
Subject(s) - kinetics , chemistry , fatty acid , beta oxidation , biochemistry , carbon 13 nmr , nuclear magnetic resonance , stereochemistry , physics , quantum mechanics
Purpose Long chain fatty acid (LCFA) oxidation measurements in the intact heart from 13 C‐NMR rely on detection of 13 C‐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 13 C labeling for exogenous LCFA and developed a simple scheme to distinguish kinetics of LCFA uptake and storage from oxidation. Methods Sequential 13 C‐NMR spectra were acquired from isolated rat hearts perfused with 13 C LCFA and glucose. Spectra were evaluated from hearts supplied: U 13 C LCFA, [2,4,6,8,10,12,14,16‐ 13 C 8 ] palmitate, [2,4,6,8,10,12,14,16,18‐ 13 C 9 ] oleate, [4,6,8,10,12,14,16‐ 13 C 7 ] palmitate, or [4,6,8,10,12,14,16,18‐ 13 C 8 ] oleate. Results 13 C signal reflected the progressive enrichment at 34.6 ppm from GLU‐C4, confounded by additional signal with distinct kinetics attributed to 13 C‐enriched LCFA 2‐carbon (34.0 ppm). Excluding 13 C 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. Conclusion Eliminating enrichment at the 2‐carbon of 13 C 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 13 C‐NMR. Magn Reson Med 74:330–335, 2015. © 2014 Wiley Periodicals, Inc.