Increased uncoupling proteins and decreased efficiency in palmitate-perfused hyperthyroid rat heart

• Published in: American journal of physiology. Heart and circulatory physiology Vol. 280; no. 3; pp. H977 - H983
• Main Authors: Boehm, Ernest A, Jones, Barney E, Radda, George K, Veech, Richard L, Clarke, Kieran
• Format: Journal Article
• Language: English
• Published: United States 01.03.2001
• Subjects: Animals; Body Weight - drug effects; Body Weight - physiology; Carrier Proteins - metabolism; Cell Respiration - drug effects; Cell Respiration - physiology; Energy Metabolism - drug effects; Energy Metabolism - physiology; Hyperthyroidism - metabolism; Ion Channels; Male; Membrane Proteins - metabolism; Membrane Transport Proteins; Mitochondria - drug effects; Mitochondria - metabolism; Mitochondrial Proteins; Myocardial Contraction - physiology; Myocardium - metabolism; Oxygen Consumption - drug effects; Oxygen Consumption - physiology; Palmitates - pharmacology; Proteins - metabolism; Rats; Rats, Wistar; Triiodothyronine - pharmacology; Uncoupling Protein 1; Uncoupling Protein 2; Uncoupling Protein 3
• ISSN: 0363-6135; 1522-1539
• DOI: 10.1152/ajpheart.2001.280.3.h977

1  Department of Biochemistry, University of Oxford, Oxford OX1 3QU, United Kingdom; and 2  Laboratory of Membrane Biochemistry and Biophysics, National Institute on Alcohol Abuse and Alcoholism, Rockville, Maryland 20852 The physiological role of mitochondrial uncoupling proteins (UCPs) in heart and skeletal muscle is unknown, as is whether mitochondrial uncoupling of oxidative phosphorylation by fatty acids occurs in vivo. In this study, we found that UCP2 and UCP3 protein content, determined using Western blotting, was increased by 32 and 48%, respectively, in hyperthyroid rat heart mitochondria. Oligomycin-insensitive respiration rate, a measure of mitochondrial uncoupling, was increased in all mitochondria in the presence of palmitate: 36% in controls and 71 and 100% with 0.8 and 0.9   mM palmitate, respectively, in hyperthyroid rat heart mitochondria. In the isolated working heart, 0.4 mM palmitate significantly lowered cardiac output by 36% and cardiac efficiency by 38% in the hyperthyroid rat heart. Thus increased mitochondrial UCPs in the hyperthyroid rat heart were associated with increased uncoupling and decreased myocardial efficiency in the presence of palmitate. In conclusion, a physiological effect of UCPs on fatty acid oxidation has been found in heart at the mitochondrial and whole organ level. isolated mitochondria; cardiac efficiency