The excretion of C6-C10-dicarboxylic acids in the urine of newborn infants during starvation. Evidence for omega-oxidation of fatty acids in the newborn

Role of mitochondrial acyl-CoA dehydrogenases in the metabolism of dicarboxylic fatty acids

Dicarboxylic fatty acids, taken as a nutritional supplement or produced endogenously via omega oxidation of monocarboxylic fatty acids, may have therapeutic potential for rare inborn errors of metabolism as well as common metabolic diseases such as type 2 diabetes. Breakdown of dicarboxylic acids yields acetyl-CoA and succinyl-CoA as products, the latter of which is anaplerotic for the TCA cycle. However, little is known about the metabolic pathways responsible for degradation of dicarboxylic acids. Here, we demonstrated with whole-cell fatty acid oxidation assays that both mitochondria and peroxisomes contribute to dicarboxylic acid degradation. Several mitochondrial acyl-CoA dehydrogenases were tested for activity against dicarboxylyl-CoAs. Medium-chain acyl-CoA dehydrogenase (MCAD) exhibited activity with both six and 12 carbon dicarboxylyl-CoAs, and the capacity for dehydrogenation of these substrates was significantly reduced in MCAD knockout mouse liver. However, when dicarboxylic acids were fed to normal mice, the expression of MCAD did not change, while expression of peroxisomal fatty acid oxidation enzymes was greatly upregulated. In conclusion, mitochondrial fatty acid oxidation, and in particular MCAD, contributes to dicarboxylic acid degradation, but feeding dicarboxylic acids induces only the peroxisomal pathway.

Plasma metabolomics indicates metabolic perturbations in low birth weight piglets supplemented with arginine

Large profit losses in the swine industry can be attributed to morbidity and mortality of piglets before weaning, especially in the low birth weight (LBW) piglet. Recent evidence suggests sow's milk contains insufficient concentrations of Arg to support optimal growth and health of piglets. Therefore, our objective was to assess global metabolomic profiles and the potential for Arg supplementation to promote growth of LBW (≤0.9 kg BW) and average birth weight (ABW; 1.3 to 1.5 kg BW) piglets. Piglets were selected in littermate pairs at processing to receive either Arg or an isonitrogenous control (Ala) and weighed daily to assess growth rate, and blood was collected at approximately 16 d of age for metabolomics analysis. In terms of growth, LBW and ABW piglets supplemented with Arg weighed 22.3 and 12.7% less, respectively, at d 16 compared with Ala-supplemented piglets of the same birth weight group. Overall, differences ( < 0.05) were observed among treatments for metabolic pathways involving energy (i.e., tricarboxylic acid cycle intermediates), AA, nucleotides, and fatty acids. Increased nucleotide turnover, indicative of an increase in DNA damage and cell death, was particularly noted in the LBW piglet. However, Arg supplementation reduced these effects to levels comparable to those observed in ABW piglets. Moreover, changes in glucose metabolism suggested a compromised ability to extract energy from dietary sources may have occurred in the LBW piglet, but these effects were partially recovered by Arg supplementation. We conclude that a reduction in the growth potential of LBW piglets may be associated with alterations in multiple metabolic pathways, and further reduction due to Arg supplementation may have resulted from perturbations in multiple metabolic pathways.

Dicarboxylic aciduria due to medium chain acyl CoA dehydrogenase defect. A cause of hypoglycemia in childhood

Dicarboxylic aciduria was found during hypoglycemic episode in a 14 months old girl. Her brother had died at the age of 4 years during febrile illness. A ketogenic diet induced in this patient a severe hypoglycemia. Urinary organic acid profile exhibited abnormal excretion of the C6-C10 dicarboxylic acids (adipic-suberic-sebacic) and related metabolites (5 hydroxyhexanoic, hexanoylglycine, suberyl glycine). This pattern suggested a defect in fatty acids beta oxidation. Plasma carnitine values was within control limits. Similar clinical findings and urinary organic acids excretion have been described in 6 patients since the initial case of Gregersen. Enzymatic studies on cultivated fibroblasts from our patient showed a defect in medium chain CoA dehydrogenase. The treatment of this disease consists of glucose infusion during attacks and prevention of fasting. This rare disease must be considered in a child with non ketotic hypoglycemia or Reye's syndrome.

Dicarboxylic aciduria during ketotic phases in various types of glycogen storage disease

Urine samples were collected before and after a starvation period of 14-16 h from patients with glycogen storage disease, one with type III (amylo-1,6-glucosidase deficiency), four with type VIII (phosphorylase-b-kinase deficiency), and one with an unclassified type. The excretion of adipic, suberic, and 3-hydroxybutyric acid was measured by combined gas chromatography-mass spectrometry. The tendency towards ketosis seemed to decline with age in the patients with type VIII. In the non-ketotic patients no excess amounts of dicarboxylic acids were excreted. Therefore, glycogen storage disease per se seems to have no direct relationship to the excretion of adipic or suberic acid. A positive correlation was, however, found between the urinary excretion of on one side 3-hydroxybutyric and on the other adipic (correlation coefficient (Kendall's tau) +0.64, P less than 0.002 (one-sided test)) or suberic (+0.61, P less than 0.003) acid. The two dicarboxylic acids are most probably formed from long-chain monocarboxylic acids by omega- and beta-oxidation. It is speculated that succinyl-CoA formed by this pathway may counteract the tendency to ketosis in patients with glycogen storage disease.