Management of newborn siblings of patients with phenylketonuria or galactosemia

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Correlação entre a idade e a contagem dos folículos antrais em mulheres inférteis

OBJETIVO: Construir um nomograma correlacionando a idade com diferentes valores dos percentis da contagem dos folículos antrais (CFA) em mulheres inférteis. MÉTODOS: Foi feito um estudo transversal de todas as pacientes atendidas, no centro de reprodução assistida Fêmina, no período de 1º de março de 2010 a 1º de outubro de 2011. As pacientes foram submetidas à ultrassonografia transvaginal do 2º ao 4º dias de seu ciclo menstrual. Foram incluídas as pacientes de 21 a 45 anos, com ciclos regulares, dois ovários íntegros, sem evidência de endocrinopatias e que assinaram o consentimento. Foram excluídas as tabagistas, portadoras de galactosemia, cistos ovarianos, com antecedente de hepatopatia, cirurgia ginecológico-ovariana e tratamento com quimioterapia ou radioterapia. Com o intuito de se verificar a correlação da CFA com a idade das pacientes, foram utilizados os percentis 5, 25, 50, 75 e 95. Com o uso dos percentis foi feita uma regressão linear que possibilitasse perceber o efeito da idade sobre a CFA. Foi utilizado como nível de significância o valor de 5% (p<0,05). RESULTADOS: Cento e setenta e duas pacientes foram incluídas no estudo e a média de idade foi de 32,7 anos. Dentre as causas de infertilidade, os fatores masculino e tubário foram as principais etiologias, contribuindo com 65% dos casos. O nomograma correlacionando a idade com os percentis 5, 25, 50, 75 e 95 da CFA foi melhor ajustado por uma função linear. Os percentis que apresentaram as correlações mais altas foram o P25 (r=-0,9; p<0,001), o P50 (r=-0,9; p<0,001) e o P75 (r=-0,9; p<0,001). CONCLUSÃO: Construiu-se um nomograma correlacionando a idade com os diferentes valores dos percentis da CFA em mulheres inférteis sem endocrinopatias. Esse apresentou um padrão linear de redução da CFA com a idade, em todos os percentis. Esse nomograma pode ser uma referência para o clínico; no entanto, uma validação futura, com dados longitudinais, ainda é necessária.

Galactose oxidation using 13C in healthy and galactosemic children

Galactosemia is an inborn error of galactose metabolism that occurs mainly as the outcome of galactose-1-phosphate uridyltransferase (GALT) deficiency. The ability to assess galactose oxidation following administration of a galactose-labeled isotope (1-13C-galactose) allows the determination of galactose metabolism in a practical manner. We aimed to assess the level of galactose oxidation in both healthy and galactosemic Brazilian children. Twenty-one healthy children and seven children with galactosemia ranging from 1 to 7 years of age were studied. A breath test was used to quantitate 13CO2 enrichment in exhaled air before and at 30, 60, and 120 min after the oral administration of 7 mg/kg of an aqueous solution of 1-13C-galactose to all children. The molar ratios of 13CO2 and 12CO2 were quantified by the mass/charge ratio (m/z) of stable isotopes in each air sample by gas-isotope-ratio mass spectrometry. In sick children, the cumulative percentage of 13C from labeled galactose (CUMPCD) in the exhaled air ranged from 0.03% at 30 min to 1.67% at 120 min. In contrast, healthy subjects showed a much broader range in CUMPCD, with values from 0.4% at 30 min to 5.58% at 120 min. The study found a significant difference in galactose oxidation between children with and without galactosemia, demonstrating that the breath test is useful in discriminating children with GALT deficiencies.

Heterodimer formation and activity in the human enzyme galactose-1-phosphate uridylyltransferase.

One of the fundamental questions concerning expression and function of dimeric enzymes involves the impact of naturally occurring mutations on subunit assembly and heterodimer activity. This question is of particular interest for the human enzyme galactose-l-phosphate uridylyl-transferase (GALT), impairment of which results in the inherited metabolic disorder galactosemia, because many if not most patients studied to date are compound heterozygotes rather than true molecular homozygotes. Furthermore, the broad range of phenotypic severity observed in these patients raises the possibility that allelic combination, not just allelic constitution, may play some role in determining outcome. In the work described herein, we have selected two distinct naturally occurring null mutations of GALT, Q188R and R333W, and asked the questions (i) what are the impacts of these mutations on subunit assembly, and (ii) if heterodimers do form, are they active? To answer these questions, we have established a yeast system for the coexpression of epitope-tagged alleles of human GALT and investigated both the extent of specific GALT subunit interactions and the activity of defined heterodimer pools. We have found that both homodimers and heterodimers do form involving each of the mutant subunits tested and that both heterodimer pools retain substantial enzymatic activity. These results are significant not only in terms of their implications for furthering our understanding of galactosemia and GALT holoenzyme structure-function relationships but also because the system described may serve as a model for similar studies of other complexes composed of multiple subunits.

Insight into the mechanism of galactokinase: role of a critical glutamate residue and helix/coil transitions

Galactokinase, the enzyme which catalyses the first committed step in the Leloir pathway, has attracted interest due to its potential as a biocatalyst and as a possible drug target in the treatment of type I galactosemia. The mechanism of the enzyme is not fully elucidated. Molecular dynamics (MD) simulations of galactokinase with the active site residues Arg-37 and Asp-186 altered predicted that two regions (residues 174-179 and 231-240) had different dynamics as a consequence. Interestingly, the same two regions were also affected by alterations in Arg-105, Glu-174 and Arg- 228. These three residues were identified as important in catalysis in previous computational studies on human galactokinase. Alteration of Arg-105 to methionine resulted in a modest reduction in activity with little change in stability. When Arg-228 was changed to methionine, the enzyme’s interaction with both ATP and galactose was affected. This variant was significantly less stable than the wild-type protein. Changing Glu-174 to glutamine (but not to aspartate) resulted in no detectable activity and a less stable enzyme. Overall, these combined in silico and in vitro studies demonstrate the importance of a negative charge at position 174 and highlight the critical role of the dynamics in to key regions of the protein. We postulate that these regions may be critical for mediating the enzyme’s structure and function. 

Rastreio neonatal da galactosémia custo/beneficio da introdução no programa nacional de diagnóstico precoce

Trabalho Final do Curso de Mestrado Integrado em Medicina, Faculdade de Medicina, Universidade de Lisboa, 2014