3-methylbutyrylcarnitine and isovaleric-acid

Topics: Acute Disease; Amino Acid Metabolism, Inborn Errors; Asymptomatic Diseases; Carnitine; Child; Child, Preschool; Chronic Disease; Creatinine; Female; Fibroblasts; Gene Expression; Genetic Association Studies; Genotype; Glycine; Hemiterpenes; Humans; Infant; Infant, Newborn; Isovaleryl-CoA Dehydrogenase; Male; Mutation; Neonatal Screening; Pentanoic Acids; Phenotype; Prevalence; Spain

Tandem mass spectrometric analysis of acylcarnitines and amino acids has been applied in newborn screening programmes for the detection of several inborn errors of metabolism. We report a false positive result for isovaleric acidaemia in a newborn screening programme using this method. The newborn screening sample showed a very prominent signal corresponding to the mass of isovalerylcarnitine. Repeat samples (age 6 days) of blood and urine showed similar results. However, urine organic acids were normal. Acylcarnitine analysis in blood, breast milk and urine of the mother also showed a prominent signal of the same mass. Gas chromatography-mass spectrometry of the methyl esters demonstrated that the signal in the patient's urine was due to the presence of pivaloylcarnitine, which is isomeric with isovalerylcarnitine. The patient's mother was receiving an antibiotic containing a derivative of pivalic acid to treat a urinary tract infection. Follow-up samples in the patient and the mother confirmed a decrease in the levels of pivaloylcarnitine, concomitant with the discontinuation of the treatment. We conclude that pivaloylcarnitine can give a false positive result for isovaleric acidaemia in newborns whose mothers are on treatment with pivoxilsulbactam-containing antibiotics.

Topics: Carnitine; False Positive Reactions; Female; Gas Chromatography-Mass Spectrometry; Hemiterpenes; Humans; Infant, Newborn; Mass Spectrometry; Metabolism, Inborn Errors; Neonatal Screening; Pentanoic Acids; Sulbactam; Urinary Tract Infections

To assess the effectiveness of glycine and carnitine therapy on isovaleryl conjugate excretion in isovaleric acidemia (IVA).. Urinary isovalerylglycine (IVG) and isovalerylcarnitine (IVC) were measured from 12-hour urine specimens collected overnight from an 8-year-old patient with IVA (who had no residual activity of isovaleryl-CoA dehydrogenase in fibroblasts) before and during 3-week courses of supplementation with glycine alone (250 mg/kg per day), L-carnitine alone (100 mg/kg per day) therapy, and both of these agents combined, with a 2 gm leucine challenge performed at the end of each treatment period.. Isovalerylglycine was the predominant metabolite excreted throughout the study, and its mean value doubled with glycine treatment. Isovalerylcarnitine excretion was minimal without carnitine supplementation. L-Carnitine therapy was associated with a 50% decline in excretion of IVG without a fully compensatory increase in IVC. The readdition of glycine to the carnitine regimen resulted in an increase in IVG excretion. Leucine challenge resulted in a 2.7- and 2.4-fold increase of IVG and IVC excretion, respectively, during L-carnitine therapy but not during glycine supplementation, and a 3.5- and 4-fold increase in excretion of both metabolites during glycine plus L-carnitine therapy. Total conjugate excretion was highest after a leucine load during combined glycine and L-carnitine therapy.. Combined glycine and L-carnitine therapy maximally increases isovaleryl conjugate excretion during metabolic stress but not under stable conditions.

Topics: Amino Acid Metabolism, Inborn Errors; Carnitine; Child; Female; Glycine; Hemiterpenes; Humans; Isovaleryl-CoA Dehydrogenase; Leucine; Oxidoreductases; Oxidoreductases Acting on CH-CH Group Donors; Pentanoic Acids

When a 12-y-old girl suffering from isovaleric acidemia was treated with L-carnitine, there was a considerable increase in her blood and urine concentration of isovalerylcarnitine. When later the patient received an infusion of glycine in place of carnitine, isovalerylcarnitine reverted toward the low levels found in a normal subject. At the end of either treatment, erythrocyte calpain was measured and found to be decreased after carnitine therapy (140 versus 96 U/mg Hb with glycine or carnitine, respectively). Because we have previously shown that the activity of calpain isolated from erythrocytes was markedly modified by isovalerylcarnitine, the present results might be seen as the consequence of the chronic exposure of the patient's red blood cells to high levels of isovalerylcarnitine. The lowered calpain activity was also proved by an increase in erythrocyte band 3 phosphorylation together with an increased erythrocyte fragility after calcium loading in the presence of the ionophore A-23187. Calpastatin, the natural inhibitor of calpain, was only slightly modified.

Topics: Calpain; Carnitine; Child; Erythrocytes; Female; Glycine; Hemiterpenes; Humans; Isovaleryl-CoA Dehydrogenase; Oxidoreductases; Oxidoreductases Acting on CH-CH Group Donors; Pentanoic Acids

Topics: Amniotic Fluid; Carnitine; Female; Fetal Diseases; Glycine; Hemiterpenes; Humans; Isovaleryl-CoA Dehydrogenase; Oxidoreductases; Oxidoreductases Acting on CH-CH Group Donors; Pentanoic Acids; Pregnancy; Prenatal Diagnosis; Spectrometry, Mass, Fast Atom Bombardment

Concentrations of l-carnitine and acylcarnitines have been determined in urine from patients with disorders of organic acid metabolism associated with an intramitochondrial accumulation of acyl-CoA intermediates. These included propionic acidemia, methylmalonic aciduria, isovaleric acidemia, multicarboxylase deficiency, 3-hydroxy-3-methylglutaric aciduria, methylacetoacetyl-CoA thiolase deficiency, and various dicarboxylic acidurias including glutaric aciduria, medium-chain acyl-CoA dehydrogenase deficiency, and multiple acyl-CoA dehydrogenase deficiency. In all cases, concentrations of acylcarnitines were greatly increased above normal with free carnitine concentrations ranging from undetectable to supranormal values. The ratios of acylcarnitine/carnitine were elevated above the normal value of 2.0 +/- 1.1. l-Carnitine was given to three of these patients; in each case, concentrations of plasma and urine carnitines increased accompanied by a marked increase in concentrations of short-chain acylcarnitines. These acylcarnitines have been examined using fast atom bombardment mass spectrometry in some of these diseases and have been shown to be propionylcarnitine in methylmalonic aciduria and propionic acidemia, isovalerylcarnitine in isovaleric acidemia, and hexanoylcarnitine and octanoylcarnitine in medium-chain acyl-CoA dehydrogenase deficiency. The excretion of these acylcarnitines is compatible with the known accumulation of the corresponding acyl-CoA esters in these diseases. In this group of disorders, the increased acylcarnitine/carnitine ratio in urine and plasma indicates an imbalance of mitochondrial mass action homeostasis and, hence, of acyl-CoA/CoA ratios. Despite naturally occurring attempts to increase endogeneous l-carnitine biosynthesis, there is insufficient carnitine available to restore the mass action ratio as demonstrated by the further increase in acylcarnitine excretion when patients were given oral l-carnitine.(ABSTRACT TRUNCATED AT 250 WORDS)

Topics: Acyl-CoA Dehydrogenases; Adolescent; Adult; Amino Acid Metabolism, Inborn Errors; Amino Acids, Branched-Chain; Carnitine; Child; Child, Preschool; Female; Hemiterpenes; Humans; Infant; Infant, Newborn; Lysine; Male; Methylmalonic Acid; Middle Aged; Pentanoic Acids; Propionates

Isovaleric acidemia, resulting from isovaleryl-coenzyme A dehydrogenase deficiency, is associated with marked reduction of free carnitine in both plasma and urine. Fast atom bombardment-mass spectrometry, hydrolysis, and gas chromatography/mass spectrometry have unequivocally identified the existence of isovalerylcarnitine, a new metabolite specific for this disorder. Administration of equimolar amounts of glycine or L-carnitine separately with leucine demonstrated that isovaleryl-coenzyme A is removed by supplemental L-carnitine in the form of isovalerylcarnitine as effectively as it is by glycine, in the form of isovalerylglycine. When L-carnitine is given alone, excretion of isovalerylglycine decreases in preference to enhanced excretion of isovalerylcarnitine and hippurate. Treatment with L-carnitine alone has proven effective in preventing further hospitalizations in a patient with this genetic disorder.

Topics: Amino Acid Metabolism, Inborn Errors; Carnitine; Child, Preschool; Chromatography, Ion Exchange; Glycine; Hemiterpenes; Humans; Isovaleryl-CoA Dehydrogenase; Male; Mass Spectrometry; Oxidoreductases; Oxidoreductases Acting on CH-CH Group Donors; Pentanoic Acids; Valerates