Myocardial Substrate Oxidation and Tricarboxylic Acid Cycle Intermediates During Hypothermic Machine Perfusion.
BACKGROUND
The optimal substrate for hypothermic machine perfusion preservation of donor hearts is unknown. Fatty acids, acetate, and ketones are preferred substrates of the heart during normothermic perfusion, but cannot replete the tricarboxylic acid (TCA) cycle directly. Propionate, an anaplerotic substrate, can replenish TCA cycle intermediates and may affect cardiac metabolism. The purpose of this study was to determine myocardial substrate preferences during hypothermic machine perfusion and to assess if an anaplerotic substrate was required to maintain the TCA cycle intermediate pool in perfused hearts.


METHODS
Groups of rat hearts were perfused with carbon-13 (13C)-labeled substrates (acetate, β-hydroxybutyrate, octanoate, with and without propionate) at low and high concentrations. TCA cycle intermediate concentrations, substrate selection, and TCA cycle flux were determined by gas chromatography/mass spectroscopy and 13C magnetic resonance spectroscopy.


RESULTS
Acetate and octanoate were preferentially oxidized, whereas β-hydroxybutyrate was a minor substrate. TCA cycle intermediate concentrations except fumarate were higher in substrate-containing perfusion groups compared with either the no-substrate perfusion group or the no-ischemia control group.


CONCLUSIONS
The presence of an exogenous, oxidizable substrate is required to support metabolism in the cold perfused heart. An anaplerotic substrate is not essential to maintain the TCA cycle intermediate pool and support oxidative metabolism under these conditions.
['Holmes|Cyonna|C|', 'Vela|Ryan J|RJ|', 'Powell|LaShondra|L|', 'Brant|Sarah|S|', 'Peltz|Matthias|M|', 'Jessen|Michael E|ME|']
D000105:Acetyl Coenzyme A D000818:Animals D002210:Caprylates D002952:Citric Acid Cycle D016027:Heart Transplantation D008297:Male D009206:Myocardium D009926:Organ Preservation D010101:Oxygen Consumption D010477:Perfusion D019289:Pyruvic Acid D051381:Rats D017207:Rats, Sprague-Dawley
Hypothermic machine perfusion preservation Cardiac metabolism Organ donation Organ preservation