Mitochondria-associated lactate dehydrogenase is not a biologically significant contributor to bioenergetic function in murine striated muscle
Kyle L. Fulghum,
Benjamin R. Rood,
Velma O. Shang,
Lindsey A. McNally,
Daniel W. Riggs,
Yu-Ting Zheng,
Bradford G. Hill
Affiliations
Kyle L. Fulghum
Diabetes and Obesity Center, Envirome Institute, Department of Medicine, University of Louisville, Louisville, KY, USA; Department of Physiology and Biophysics, University of Louisville, Louisville, KY, USA
Benjamin R. Rood
Diabetes and Obesity Center, Envirome Institute, Department of Medicine, University of Louisville, Louisville, KY, USA
Velma O. Shang
Diabetes and Obesity Center, Envirome Institute, Department of Medicine, University of Louisville, Louisville, KY, USA; Department of Biochemistry and Molecular Genetics, University of Louisville, Louisville, KY, USA
Lindsey A. McNally
Diabetes and Obesity Center, Envirome Institute, Department of Medicine, University of Louisville, Louisville, KY, USA
Daniel W. Riggs
Diabetes and Obesity Center, Envirome Institute, Department of Medicine, University of Louisville, Louisville, KY, USA; Department of Bioinformatics and Biostatistics, University of Louisville, Louisville, KY, USA
Yu-Ting Zheng
Diabetes and Obesity Center, Envirome Institute, Department of Medicine, University of Louisville, Louisville, KY, USA
Bradford G. Hill
Diabetes and Obesity Center, Envirome Institute, Department of Medicine, University of Louisville, Louisville, KY, USA; Department of Physiology and Biophysics, University of Louisville, Louisville, KY, USA; Department of Biochemistry and Molecular Genetics, University of Louisville, Louisville, KY, USA; Corresponding author. Department of Medicine, Christina Lee Brown Envirome Institute, Diabetes and Obesity Center, University of Louisville, 580 S. Preston St., Rm 321E, Louisville, KY, 40202, USA.
Previous studies indicate that mitochondria-localized lactate dehydrogenase (mLDH) might be a significant contributor to metabolism. In the heart, the presence of mLDH could provide cardiac mitochondria with a higher capacity to generate reducing equivalents directly available for respiration, especially during exercise when circulating lactate levels are high. The purpose of this study was to test the hypothesis that mLDH contributes to striated muscle bioenergetic function. Mitochondria isolated from murine cardiac and skeletal muscle lacked an appreciable ability to respire on lactate in the absence or presence of exogenous NAD+. Although three weeks of treadmill running promoted physiologic cardiac growth, mitochondria isolated from the hearts of acutely exercised or exercise-adapted mice showed no further increase in lactate oxidation capacity. In all conditions tested, cardiac mitochondria respired at >20-fold higher levels with provision of pyruvate compared with lactate. Similarly, skeletal muscle mitochondria showed little capacity to respire on lactate. Protease protection assays of isolated cardiac mitochondria confirmed that LDH is not localized within the mitochondrion. We conclude that mLDH does not contribute to cardiac bioenergetics in mice. Keywords: Cardiac hypertrophy, Exercise, Mitochondria, Respiration, Bioenergetics, Glycolysis
