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Determination of malate‐aspartate shuttle activity in intact hearts using 13 C NMR spectroscopy and modeling
Author(s) -
Lu Ming,
Saidel Gerald,
Yu Xin
Publication year - 2009
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.23.1_supplement.513.3
Subject(s) - citric acid cycle , cytosol , chemistry , flux (metallurgy) , metabolism , nuclear magnetic resonance spectroscopy , biochemistry , mitochondrion , biophysics , stereochemistry , biology , enzyme , organic chemistry
The malate‐aspartate (M‐A) shuttle, which transports cytosolic NADH into mitochondria, provides an important mechanism to regulate metabolic activity in these two compartments. However, direct measurement of M‐A shuttle flux has not been possible. In this study, we developed a novel approach that combines dynamic 13 C NMR spectroscopy with biology detailed model of cardiac metabolism to directly quantify M‐A shuttle flux from experimental data. Dynamic 13 C NMR spectra were acquired from isolated rat hearts perfused with either short chain (2.5mM [2‐ 13 C]acetate) or long chain (0.32mM [U‐ 13 C]palmitate) fatty acids (FA). A 3 rd group of hearts were perfused with 2.5mM [2‐ 13 C]acetate plus unlabeled glucose (5.0mM) and lactate (1.0mM) to induce high cytosolic redox state (HRX). TCA cycle flux (V TCA ) and M‐A shuttle activity (V M‐A ) were determined by least‐square fitting of a novel multi‐domain kinetic model of cardiac metabolism to dynamic 13 C NMR spectra. Our results showed that, regardless of chain length, both V TCA and V M‐A were unchanged in FA only groups. At HRX, V TCA was unaltered compared to the other two groups, however, V M‐A was increased by 40% (P<0.05). Therefore, our proposed method provides the opportunity to directly quantify metabolic communication between subcellular compartments via M‐A shuttle under various pathophysiological conditions. This work was supported by R01HL073315 & R01HL086935.