Inhibition of hepatic carnitine palmitoyl-transferase I (CPT IA) by valproyl-CoA as a possible mechanism of valproate-induced steatosis

• Published in: Biochemical pharmacology 2010-03, Vol.79 (5), p.792-799
• Main Authors: Aires, Cátia C.P., IJlst, Lodewijk, Stet, Femke, Prip-Buus, Carina, de Almeida, Isabel Tavares, Duran, Marinus, Wanders, Ronald J.A., Silva, Margarida F.B.
• Format: Article
• Language: English
• Subjects: Acyl Coenzyme A - pharmacology; Animals; Anticonvulsants - toxicity; Biological and medical sciences; Carnitine O-Palmitoyltransferase - antagonists & inhibitors; Carnitine O-Palmitoyltransferase - genetics; Carnitine O-Palmitoyltransferase - metabolism; Carnitine palmitoyl-transferase I; Cells, Cultured; Drug-induced hepatic steatosis; Enzyme Inhibitors - pharmacology; Fatty acid oxidation; Fatty Acids - metabolism; Fatty Liver - chemically induced; Fatty Liver - enzymology; Fibroblasts - drug effects; Fibroblasts - enzymology; Gastroenterology. Liver. Pancreas. Abdomen; Humans; Liver. Biliary tract. Portal circulation. Exocrine pancreas; Malonyl-CoA; Medical sciences; Other diseases. Semiology; Oxidation-Reduction; Pharmacology. Drug treatments; Plasmids; Rats; Saccharomyces cerevisiae; Saccharomyces cerevisiae - enzymology; Saccharomyces cerevisiae - genetics; Transfection; Valproic acid; Valproic Acid - toxicity
• ISSN: 0006-2952; 1873-2968
• DOI: 10.1016/j.bcp.2009.10.011

Carnitine palmitoyl-transferase I (CPT I) catalyses the synthesis of long-chain (LC)-acylcarnitines from LC-acyl-CoA esters. It is the rate-limiting enzyme of mitochondrial fatty acid β-oxidation (FAO) pathway and its activity is regulated by malonyl-CoA. The antiepileptic drug valproic acid (VPA) is a branched chain fatty acid that is activated to the respective CoA ester in the intra- and extra-mitochondrial compartments. This drug has been associated with a clear inhibition of mitochondrial FAO, which motivated our study on its potential effect on hepatic CPT I. To investigate the effect of valproyl-CoA (VP-CoA) on CPT I, we performed in vitro studies using control human fibroblasts and rat CPT IA expressed in Saccharomyces cerevisiae. In addition to the wild-type enzyme, two mutant rCPT IAs were studied, one of which showing increased sensitivity towards malonyl-CoA (S24A/Q30A), whereas the other one is insensitive to malonyl-CoA (E3A). We demonstrate that VP-CoA inhibits the CPT I activity in control fibroblasts. Similar results were obtained using rCPT IA WT and S24A/Q30A. Importantly, VP-CoA also inhibited the activity of the rCPT IA E3A. We show that VP-CoA inhibits CPT IA competitively with respect to palmitoyl-CoA, and non-competitively to carnitine. Evidence is provided that VP-CoA interferes at the catalytic domain of CPT IA affecting the sensitivity for malonyl-CoA. The interference of VP-CoA with CPT IA, a pivotal enzyme in mitochondrial fatty acid β-oxidation, may be a crucial mechanism in the drug-induced hepatotoxicity and the weight gain frequently observed in patients under VPA therapy.