Etomoxir-induced partial carnitine palmitoyltransferase-I (CPT-I) inhibition in vivo does not alter cardiac long-chain fatty acid uptake and oxidation rates

J.J.F.P. Luiken, H.E.C. Niessen, S.L.M. Coort, N. Hoebers, W.A. Coumans, R.W. Schwenk, A. Bonen, J.F. Glatz

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Abstract

Abstract: Although CPT-I (carnitine palmitoyltransferase-I) is generally regarded to present a major rate-controlling site in mitochondrial beta-oxidation, it is incompletely understood whether CPT-I is rate-limiting in the overall LCFA (long-chain fatty acid) flux in the heart. Another important site of regulation of the LCFA flux in the heart is trans-sarcolemmal LCFA transport facilitated by CD36 and FABPpm (plasma membrane fatty acid-binding protein). Therefore, we explored to what extent a chronic pharmacological blockade of the LCFA flux at the level of mitochondrial entry of LCFA-CoA would affect sarcolemmal LCFA uptake. Rats were injected daily with saline or etomoxir, a specific CPT-I inhibitor, for 8 days at 20 mg/kg of body mass. Etomoxir-treated rats displayed a 44 % reduced cardiac CPT-I activity. Sarcolemmal contents of CD36 and FABPpm, as well as the LCFA transport capacity, were not altered in the hearts of etomoxir-treated versus control rats. Furthermore, rates of LCFA uptake and oxidation, and glucose uptake by cardiac myocytes from etomoxir-treated rats were not different from control rats, neither under basal nor under acutely induced maximal metabolic demands. Finally, hearts from etomoxir-treated rats did not display triacylglycerol accumulation. Therefore CPT-I appears not to present a major rate-controlling site in total cardiac LCFA flux. It is likely that sarcolemmal LCFA entry rather than mitochondrial LCFA-CoA entry is a promising target for normalizing LCFA flux in cardiac metabolic diseases.
Original languageEnglish
Pages (from-to)447-55
JournalBiochemical Journal
Volume419
Issue number2
DOIs
Publication statusPublished - 1 Jan 2009

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