ABSTRACT
BACKGROUND: Valproic acid (2-propyl-N-pentanoic acid, VPA) causes severe hepatic dysfunction, similar to Reye's syndrome, in a small number of patients. An enhanced excretion of dicarboxylic acids by patients indicates an interference with mitochondrial beta-oxidation. We investigated the expression of various acyl-coenzyme A (acyl-CoA) dehydrogenases (ACD), which catalyze the first step of beta-oxidation in VPA-treated rats. METHODS: The control group received normal saline and the experimental group received VPA (500 mg/kg per day) by intraperitoneal injections for 7 days. Various clinical chemistry parameters in rat blood and free and total carnitine levels in plasma and tissue were determined. Mitochondria were isolated from rat liver and heart and the relative amount of each ACD protein was determined by immunoblot analysis. Total RNA was prepared from various tissues and the mRNA levels for various ACD were measured by slot-blot hybridization analysis using respective cDNA probes. RESULTS: Administration of VPA to rats caused various metabolic effects including hypoglycemia, hyperammonemia and decreased beta-hydroxybutyrate concentration. Free carnitine levels in plasma and heart were also decreased. Enzyme activities of various acyl-CoA dehydrogenases, which are involved in fatty acid oxidation, decreased moderately in heart (57-79%), and slightly in liver (78-95%). The most prominent effects were observed in mRNA levels involved in fatty acid oxidation (short-, medium- and long-chain acyl-CoA dehydrogenase). Each mRNA increased in the liver, kidney, skeletal muscle and heart to varying degrees when rats were fed ad libitum. The increase of short- and medium- chain acyl-CoA dehydrogenase mRNA in the heart were particularly large. However, 3 day starvation strongly inhibited expression of ACD in VPA-treated rats. There was an apparent decrease in the amount of ACD mRNA and proteins in VPA-treated liver. CONCLUSIONS: Valproic acid causes enhanced expression of fatty ACD mRNA, especially in the heart, by a feedback mechanism related to inhibition of beta-oxidation in rats fed ad libitum. However, it impairs the expression of ACD in the liver when there is a drastic change in nutritional state.
Subject(s)
Acyl-CoA Dehydrogenase, Long-Chain/drug effects , Anticonvulsants/adverse effects , Valproic Acid/adverse effects , Acyl-CoA Dehydrogenase , Acyl-CoA Dehydrogenase, Long-Chain/analysis , Animals , Anticonvulsants/metabolism , Carnitine/blood , Chemical and Drug Induced Liver Injury/etiology , Chemical and Drug Induced Liver Injury/metabolism , Drug Evaluation, Preclinical , Fatty Acids/metabolism , Male , Mitochondria, Heart/chemistry , Mitochondria, Heart/metabolism , Mitochondria, Liver/chemistry , Mitochondria, Liver/metabolism , Oxidation-Reduction , Rats , Rats, Wistar , Starvation/metabolism , Valproic Acid/metabolismABSTRACT
Studies of effects of 4-thia-substituted fatty acid analogues on rat liver lipid metabolism are described. With isolated hepatocytes tetradecylthiopropionate was shown to divert [1-14C]oleate from beta-oxidation into esterification, the total amount of [1-14C]oleate metabolized remaining unchanged. Tetradecylthiopropionyl-CoA was a good substrate for mitochondrial carnitine palmitoyltransferases I and II (EC 2.3.1.21), acyl-CoA oxidase (EC 1.3.3.6), for the microsomal (but not mitochondrial) glycerophosphate acyltransferase (EC 2.3.1.15), and for long-chain acyl-CoA dehydrogenase (EC 1.3.99.3). In isolated hepatocytes, its 4-thia-trans-2-enoic derivative, tetradecylthioacrylate, inhibits both beta-oxidation of, and incorporation of, [1-14C]oleate into lipids. In rat liver mitochondria tetradecylthiocrylate inhibited beta-oxidation. The degree of inhibition was not markedly increased by preincubation with tetradecylthioacrylate. Tetradecylthioacrylyl-CoA was a poor substrate for carnitine palmitoyltransferase I, and inhibited carnitine palmitoyltransferase II, microsomal glycerophosphate acyltransferase and acyl-CoA oxidase. It is concluded that the inhibitory effects of tetradecylthiopropionyl-CoA are expressed intramitochondrially, whereas primary sites of inhibition by tetradecylthioacrylyl-CoA are extramitochondrial.
Subject(s)
Acrylates/pharmacology , Acyl Coenzyme A/pharmacology , Lipid Metabolism , Liver/metabolism , Propionates/pharmacology , Repressor Proteins , Saccharomyces cerevisiae Proteins , Sulfides/pharmacology , Acyl-CoA Dehydrogenase , Acyl-CoA Dehydrogenase, Long-Chain/drug effects , Acyl-CoA Oxidase , Animals , Carbon Radioisotopes , Carnitine O-Palmitoyltransferase/drug effects , Coenzyme A Ligases/drug effects , Dose-Response Relationship, Drug , Glycerol-3-Phosphate O-Acyltransferase/drug effects , Isotope Labeling , Liver/cytology , Liver/drug effects , Male , Mitochondria, Liver/metabolism , Oleic Acid , Oleic Acids/metabolism , Oxidation-Reduction , Oxidoreductases/drug effects , Rats , Rats, WistarABSTRACT
Late onset Multiple Acyl CoA dehydrogenase (MAD) deficiency myopathy is a rare disorder. Only five cases have been reported. We report one case with MAD deficiency in which the clinical features appeared during valproic acid therapy. A 47-yr-old man taking valproic acid for 4 months presented nocturnal calf cramps, exercise intolerance, difficulty in climbing stairs and shortness of breath. Muscle biopsy revealed ragged red fibres and neutral lipid storage. Electron microscopy showed enlarged abnormal mitochondria with abnormal internal structure. The total and free muscle carnitine was decreased. The activities of all short, medium and long chain acyl CoA dehydrogenases were 40% of the normal. In this case a partial defect of MAD is noted, possibly triggered by valproic acid, causing the clinical manifestations of the pre-existing myopathy. After discontinuation of the drug a clinical improvement was observed while therapy with riboflavin resulted in a total relief of the symptoms.
