O'Donnell JM, Fasano MJ, Lewandowski ED. Resolving confounding enrichment kinetics due to overlapping resonance signals from 13C-enriched long chain fatty acid oxidation and uptake within intact hearts.
Magn Reson Med 2014;
74:330-5. [PMID:
25199499 DOI:
10.1002/mrm.25446]
[Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/10/2014] [Revised: 08/04/2014] [Accepted: 08/18/2014] [Indexed: 11/09/2022]
Abstract
PURPOSE
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.
CONCLUSION
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
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