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Department of Human Nutrition and Food Management, The Ohio State University, Columbus, OH 43210 and * Center for Cardiovascular Research, Departments of Medicine and Molecular Biology and Pharmacology, Washington University School of Medicine, St. Louis, MO 63110
2To whom correspondence should be addressed at Department of Human Nutrition, 213 Justin Hall, Kansas State University, Manhattan, KS 66506-1407.
The mechanism(s) by which impaired mitochondrial respiratory function and the accumulation of lipid droplets and mitochondria in hearts of copper-deficient rats occur remains unclear. It is not known whether specific components of the regulatory pathway involved in mitochondrial biogenesis, such as mitochondrial transcription factor A (mtTFA) and nuclear respiratory factors 1 and 2 (NRF-1 and NRF-2), are activated in copper deficiency. Little is known about gene expression of enzymes involved in fatty acid oxidation (FAO) in hearts of copper-deficient rats. Male weanling rats were fed copper-adequate (CuA), copper-deficient (CuD) or pair-fed (CuP) diets for 5 wk. Mitochondria and lipid droplet volume densities from electron micrographs were greater and there was an elevation in the mtTFA protein level in hearts of copper-deficient rats. DNA binding activities of NRF-1 and NRF-2 did not differ among the groups. Northern blot analysis of cardiac tissue revealed that transcripts of F1F0-ATP synthase subunit c were greater, but mRNA levels of ATP synthase ß subunit and the FAO enzyme, medium-chain acyl-CoA dehydrogenase (MCAD), were lower in hearts of copper-deficient rats. Long-chain acyl-CoA dehydrogenase (LCAD) mRNA levels did not differ among treatment groups. These results suggest that certain components of the mitochondrial biogenesis program are activated in hearts of copper-deficient rats. F1F0-ATP synthase ß subunit and MCAD transcript levels remain low, which may contribute to impaired mitochondrial respiratory function, decreased fatty acid utilization and lipid droplet accumulation in hearts of copper-deficient rats.
KEY WORDS: rats mitochondrial transcription factor A ATP synthase copper deficiency medium-chain acyl-CoA dehydrogenase
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