RESUMO
Acute metabolic decompensation in maple syrup urine disease (MSUD) during otherwise minor illnesses has generally been presumed to result from massive release of leucine from protein catabolism. A stable isotope method based on the continuous infusion of (2H5)phenylalanine was used to measure protein metabolism in vivo in two children with MSUD during acute illness and when well. Net protein catabolism was greater in the unwell state (0.51 and 0.40 gm/kg per 24 hours in each child, respectively) than in the basal state (0.34 and 0.32). This rate of release of leucine from protein is compatible only with a slow (several days) rather than a dramatic rise in plasma leucine levels during acute illness in MSUD. Poor oral intake leading to a relative increase in time spent in the fasting state appears to be a more important determinant of increasing leucine levels than the catabolic effect of infection in itself. These factors suggested that branched-chain amino acid restriction should be commenced at the start of minor illness in children with MSUD, and that intake of other nutrients should be maintained or increased throughout the illness. A regimen based on these concepts was used during nine episodes of minor illness in two children with MSUD. Plasma branched-chain amino acid levels remained acceptable (less than 700 mumol/L) throughout each of these episodes. Dietary supplementation of this type may reduce the risk of metabolic decompensation during acute illnesses in children with MSUD.
Assuntos
Leucina/metabolismo , Doença da Urina de Xarope de Bordo/metabolismo , Proteínas/metabolismo , Doença Aguda , Aminoácidos de Cadeia Ramificada/sangue , Pré-Escolar , Feminino , Humanos , Lactente , Doença da Urina de Xarope de Bordo/complicações , Doença da Urina de Xarope de Bordo/dietoterapia , Infecções Respiratórias/complicaçõesRESUMO
Continuous venovenous hemofiltration was used to treat two neonates, one with maple syrup urine disease and the other with an inborn error of long-chain fatty acid oxidation. The latter infant had hypoglycemia, hyperammonemia and lactic acidosis. In both cases, acceptable biochemical control was achieved within 8 hours. This therapy offers the potential to overcome acute crises rapidly in a wide range of inborn errors of intermediary metabolism.
Assuntos
Ácidos Graxos/metabolismo , Hemofiltração/métodos , Erros Inatos do Metabolismo Lipídico/terapia , Doença da Urina de Xarope de Bordo/terapia , Aminoácidos/sangue , Aminoácidos de Cadeia Ramificada/sangue , Feminino , Humanos , Recém-Nascido , Erros Inatos do Metabolismo Lipídico/sangue , Masculino , Doença da Urina de Xarope de Bordo/sangueRESUMO
The relative importance of endogenous metabolism and urinary metabolite excretion was assessed in vivo in six children with methylmalonic acidemia by examining the kinetics of the immediate precursor to methylmalonate, propionate. Total production and oxidation of propionate were measured by means of a continuous infusion of (1-13C)propionate and were compared with the urinary excretion of propionate metabolites. Propionate oxidation was substantial (mean 48.9 mumol/kg/hr +/- SD 18.0) and, in four children, exceeded urinary metabolite excretion (mean urinary excretion in all subjects 40 mumol/kg/hr +/- 25). The sum of urinary excretion and oxidation rates (88 mumol/kg/hr +/- 29) approximated the total propionate production (93.4 +/- 37.0), suggesting that these routes together constitute the major mechanisms of propionate disposal. These results suggest that propionate oxidation is an important route of disposal in methylmalonic acidemia. Variations in the relative proportions of propionate disposal through oxidation and urinary excretion may be one reason for the often poor correlation between clinical status and urinary metabolite excretion. Measurement of urinary metabolite concentration alone may not always reflect clinical status and responses to treatment accurately.
Assuntos
Malonatos/metabolismo , Erros Inatos do Metabolismo/metabolismo , Ácido Metilmalônico/metabolismo , Propionatos/farmacocinética , Humanos , Lactente , Recém-Nascido , Erros Inatos do Metabolismo/sangue , Erros Inatos do Metabolismo/urina , Ácido Metilmalônico/sangue , Ácido Metilmalônico/urina , OxirreduçãoRESUMO
The effect of taurine supplementation (30 to 40 mg/kg/24 hr) on fat absorption and related measurements was examined in 21 preadolescent children with cystic fibrosis (CF) using a 12-month double-blind crossover technique. The mean coefficient of fat absorption was unchanged by taurine both in the unselected study group (without taurine, mean +/- SD 84.0% +/- 11.9%; with taurine, 84.4% +/- 11.8%, n = 20) and in a subgroup of seven children with moderately severe fat malabsorption (without taurine, 75.6% +/- 15.6%; with taurine, 74.8% +/- 14.6%). The mean fecal split fat/total fat ratio, which generally reflects bile acid-related fat malabsorption, was also unchanged. Linoleic and arachidonic acid deficiencies noted in plasma before supplementation showed no significant improvement with taurine supplementation. Likewise, plasma/serum vitamin A, E, and D levels were unchanged. Standard scores for height and weight were not affected significantly. This study does not support the use of taurine supplementation in the nutritional management of CF.