Metabolism of deuterium-labeled nonanoic acids in the riboflavin-deficient rat model of multiple acyl-CoA dehydrogenase deficiency

Equine biochemical multiple acyl-CoA dehydrogenase deficiency (MADD) as a cause of rhabdomyolysis

Two horses (a 7-year-old Groninger warmblood gelding and a six-month-old Trakehner mare) with pathologically confirmed rhabdomyolysis were diagnosed as suffering from multiple acyl-CoA dehydrogenase deficiency (MADD). This disorder has not been recognised in animals before. Clinical signs of both horses were a stiff, insecure gait, myoglobinuria, and finally recumbency. Urine, plasma, and muscle tissues were investigated. Analysis of plasma showed hyperglycemia, lactic acidemia, increased activity of muscle enzymes (ASAT, LDH, CK), and impaired kidney function (increased urea and creatinine). The most remarkable findings of organic acids in urine of both horses were increased lactic acid, ethylmalonic acid (EMA), 2-methylsuccinic acid, butyrylglycine (iso)valerylglycine, and hexanoylglycine. EMA was also increased in plasma of both animals. Furthermore, the profile of acylcarnitines in plasma from both animals showed a substantial elevation of C4-, C5-, C6-, C8-, and C5-DC-carnitine. Concentrations of acylcarnitines in urine of both animals revealed increased excretions of C2-, C3-, C4-, C5-, C6-, C5-OH-, C8-, C10:1-, C10-, and C5-DC-carnitine. In addition, concentrations of free carnitine were also increased. Quantitative biochemical measurement of enzyme activities in muscle tissue showed deficiencies of short-chain acyl-CoA dehydrogenase (SCAD), medium-chain acyl-CoA dehydrogenase (MCAD), and isovaleryl-CoA dehydrogenase (IVD) also indicating MADD. Histology revealed extensive rhabdomyolysis with microvesicular lipidosis predominantly in type 1 muscle fibers and mitochondrial damage. However, the ETF and ETF-QO activities were within normal limits indicating the metabolic disorder to be acquired rather than inherited. To our knowledge, these are the first cases of biochemical MADD reported in equine medicine.

Synthesis of [9-14C]nonanoic acid via 2-thienyl(14CH3)(cyano)cuprate and its oxidation by newborn piglet muscle strips

To determine if newborn piglet muscle could oxidize propionyl-CoA formed by catabolism of odd-chain fatty acids, an odd-chain fatty acid labeled in the terminal three carbons was needed. The synthetic scheme described is based upon the displacement of a primary alkyl iodide, ethyl 8-iodooctanoate, by a [14C]methyl group via an activated 2-thienyl(14CHa)(cyano)cuprate intermediate, forming ethyl [9-14C]nonanoate. Ethyl [9-14C]nonanoate was hydrolyzed in 6 N KOH and [9-14C]nonanoic acid recovered by ion-exchange chromatography. The yield of [9-14C]nonanoic acid was 40%, based on the initial amount of [14C]methyl iodide. The cuprate and other precursors were commercially available or readily synthesized from available precursors. Mass spectroscopy of commercial and synthesized nonradioactive nonanoate determined an m/z of 159 for the product molecular ion, as expected. The 14C-labeled product phenacyl ester was found to cochromatograph in a C-18 reverse-phase HPLC system with similarly derivatized commercially obtained nonanoic acid. The synthesis should be generally applicable to labeling of compounds by displacement of primary alkyl iodides, where other reactive groups (e.g., carboxylic acid), if present, can be protected (e.g., converted to an ester). Muscle strips isolated from the triceps muscle of newborn piglets oxidized [9-14C]nonanoic acid to 14CO2. Newborn piglet muscle can oxidize propionyl-CoA produced during odd-chain fatty acid oxidation.