Impaired cytosolic NADH shuttling and elevated UCP3 contribute to inefficient citric acid cycle flux support of postischemic cardiac work in diabetic hearts

• Published in: Journal of molecular and cellular cardiology Vol. 79; pp. 13 - 20
• Main Authors: Banke, Natasha H., Lewandowski, E. Douglas
• Format: Journal Article
• Language: English
• Published: England Elsevier Ltd 01.02.2015
• Subjects: Animals; Aspartic Acid - metabolism; Carbon-13 Magnetic Resonance Spectroscopy; Cardiovascular; Carrier Proteins - metabolism; Citric Acid Cycle; Cytosol - metabolism; db/db mouse malate–aspartate shuttle; Diabetes Mellitus, Experimental - complications; Diabetes Mellitus, Experimental - metabolism; Diabetes Mellitus, Experimental - physiopathology; Hemodynamics; Ion Channels - metabolism; Malates - metabolism; Male; Mice, Inbred C57BL; Mitochondria; Mitochondrial Proteins - metabolism; Myocardial Ischemia - complications; Myocardial Ischemia - metabolism; Myocardial Ischemia - physiopathology; Myocardial Reperfusion Injury - metabolism; Myocardial Reperfusion Injury - pathology; Myocardial Reperfusion Injury - physiopathology; Myocardium - metabolism; Myocardium - pathology; NAD - metabolism; Oxidation-Reduction; Oxoglutarate–malate carrier; Perfusion; PPAR alpha - metabolism; Reducing equivalents; Uncoupling protein; Uncoupling Protein 2; Uncoupling Protein 3; db/db; db/db mouse malate–aspartate shuttle; Uncoupling protein; CAC; OMC; NADHc; DM2; ISC/REP; MVO2; Oxoglutarate–malate carrier; Reducing equivalents; LCFA; NMR; Mitochondria; RPP; MA; FAO; UCP3; UCP2; NORM; MHC-PPARα; ischemia/reperfusion; cytosolic NADH; type 2 diabetes mellitus; db/db mouse; rate pressure product; normal c57bl/6 heart; myocardial oxygen consumption; nuclear magnetic resonance; long chain fatty acid; myosin heavy chain-peroxisome proliferator activated receptor alpha; malate–aspartate shuttle; uncoupling protein 2; citric acid cycle; uncoupling protein 3; oxoglutarate malate carrier; fatty acid oxidation; MVO 2
• ISSN: 0022-2828; 1095-8584; 1095-8584
• DOI: 10.1016/j.yjmcc.2014.10.015

Diabetic hearts are subject to more extensive ischemia/reperfusion (ISC/REP) damage. This study examined the efficiency of citric acid cycle (CAC) flux and the transfer of cytosolic reducing equivalents into the mitochondria for oxidative support of cardiac work following ISC/REP in hearts of c57bl/6 (NORM) and type 2 diabetic, db/db mouse hearts. Flux through the CAC and malate–aspartate shuttle (MA) were monitored via dynamic 13C NMR of isolated hearts perfused with 13C palmitate+glucose. MA flux was lower in db/db than NORM. Oxoglutarate malate carrier (OMC) was elevated in the db/db heart, suggesting a compensatory response to low NADHc. Baseline CAC flux per unit work (rate-pressure-product, RPP) was similar between NORM and db/db, but ISC/REP reduced the efficiency of CAC flux/RPP by 20% in db/db. ISC/REP also increased UCP3 transcription, indicating potential for greater uncoupling. Therefore, ISC/REP induces inefficient carbon utilization through the CAC in hearts of diabetic mice due to the combined inefficiencies in NADHc transfer per OMC content and increased uncoupling via UCP3. Ischemia and reperfusion exacerbated pre-existing mitochondrial defects and metabolic limitations in the cytosol of diabetic hearts. These limitations and defects render diabetic hearts more susceptible to inefficient carbon fuel utilization for oxidative energy metabolism. •Postischemic function in diabetic heart has a high cost in citric acid cycle flux.•Diabetic hearts have high levels of OMC protein for oxidation of cytosolic NADH.•Despite high OMC cytosolic NADH oxidation remains limited in diabetic hearts.•Limited NADHc increases citric acid cycle flux in postischemic diabetic hearts.•High UCP contributes to inefficient carbon flux in postischemic diabetic hearts.