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Tetrahydrobiopterin Responsiveness of Patients with Phenylalanine

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Tetrahydrobiopterin Responsiveness of Patients with Phenylalanine 0021-7557/11/87-03/245 Jornal de Pediatria Copyright © 2011 by Sociedade Brasileira de Pediatria ARTIGO ORIGINAL Tetrahydrobiopterin responsiveness of patients with phenylalanine hydroxylase deficiency Responsividade à tetrahidrobiopterina em pacientes com deficiência de fenilalanina hidroxilase Luciana Giugliani1, Angela Sitta2, Carmen R. Vargas3, Luiz C. Santana-da-Silva4, Tatiéle Nalin5, Maria Luiza Saraiva-Pereira6, Roberto Giugliani7, Ida Vanessa D. Schwartz8 Resumo Abstract Objetivo: Identificar indivíduos responsivos à tetrahibrobiopterina Objective: To identify patients responsive to tetrahydrobiopterin (BH4) em uma amostra de pacientes brasileiros com hiperfenilalaninemia (BH4) in a sample of Brazilians with hyperphenylalaninemia due to por deficiência de fenilalanina-hidroxilase (HPA-PAH). phenylalanine hydroxylase deficiency (HPA-PAH). Métodos: Estudo intervencional, amostragem por conveniência. Para Methods: Interventional study, convenience sampling. The inclusion serem incluídos no estudo, os pacientes deveriam: possuir diagnóstico criteria were: diagnosis of HPA-PAH; age ≥ 7 years; phenylalanine- bioquímico de HPA-PAH; ter idade ≥ 7 anos; estar em tratamento die- restricted diet and phenylalanine (Phe) levels ≥ 6 mg/dL in all blood tético; e apresentar níveis de fenilalanina (Phe) ≥ 6 mg/dL em todas tests 1 year before inclusion. Blood samples were obtained the day as medidas realizadas no ano anterior à inclusão no estudo. Os níveis before (day 1) and at 0, 4, 8 (day 2) and 24 h (day 3) after BH4 intake. de Phe foram determinados por meio de espectrometria de massas in Phe levels were measured using tandem mass spectrometry. The criteria tandem no dia anterior (dia 1) e nos pontos de hora 0, 4 e 8 h (dia 2) used to define responsiveness to BH4 were: criterion 1- Phe reduction e 24 h (dia 3) após ingestão de BH4. Os critérios utilizados para definir ≥ 30% 8 h after BH4 administration; criterion 2 - Phe reduction ≥ 30% responsividade ao BH4 foram: critério 1-redução ≥ 30% de Phe após 8 24 h after BH4 administration. h da administração de BH4; e critério 2-redução ≥ 30% de Phe após 24 Results: Eighteen patients were enrolled (median age, 14 years; h da administração. 12 boys). Five patients were responsive to BH4, 3 according to both Resultados: Dezoito pacientes foram incluídos no estudo (mediana criteria (one classical PKU, two mild PKU); and two according to de idade = 14 anos, sexo masculino = 12). Cinco pacientes foram res- criterion 2 (one classical PKU; one indefinite PKU type). There were no ponsivos ao BH4, sendo três (forma clássica: um; forma leve: dois) de differences between Phe serum levels on day 1 and at the other time acordo com ambos os critérios, e dois (forma clássica: um; forma não points (p = 0.523). However, Phe levels on days 1 and 2 were significantly definida: um) de acordo com o critério 2. Os níveis de Phe plasmáticos different (p = 0.006). The analysis of the phenotype-genotype association do dia 1 não demonstraram variação nos pontos de hora (p = 0,523). confirmed its multifactorial character. Entretanto, quando comparamos os níveis de Phe nos pontos de hora Conclusion: A relevant number of Brazilian patients with HPA-PAH are dos dias 1 e 2, encontramos uma variação significativa (p = 0,006). A responsive to BH4, in agreement with other studies in the literature. análise da associação genótipo-fenótipo confirmou o caráter multifatorial da responsividade ao BH4. Conclusão: Os nossos achados estão de acordo com a literatura e indicam que um número relevante de pacientes brasileiros com HPA-PAH é responsivo à BH4. J Pediatr (Rio J). 2011;87(3):245-251: Fenilcetonúrias, fenilalanina J Pediatr (Rio J). 2011;87(3):245-251: Phenylketonuria, phenylalanine hidroxilase, biopterina. hydroxylase, biopterin. 1. Mestre, Programa de Pós-Graduação em Saúde da Criança e do Adolescente, Universidade Federal do Rio Grande do Sul (UFRGS), Porto Alegre, RS. 2. Mestre, Ciências Biológicas (Bioquímica). UFRGS, Porto Alegre, RS. 3. Doutora, Ciências Biológicas (Bioquímica). Professora adjunta III, UFRGS, Porto Alegre, RS. 4. Doutor, Ciências Biológicas (Bioquímica). UFRGS, Porto Alegre, RS. Professor, Instituto de Ciências Biológicas, Universidade Federal do Pará (UFPA), Belém, PA. 5. Mestranda, Programa de Pós-Graduação em Medicina: Ciências Médicas, UFRGS, Porto Alegre, RS. 6. Doutora, Genética Molecular, University of London (UL), Londres, Reino Unido. Professora associada, Departamento de Bioquímica, UFRGS, Porto Alegre, RS. 7. Doutor, Genética. Universidade de São Paulo (USP), São Paulo, SP. Professor titular, Departamento de Genética, UFRGS, Porto Alegre, RS. 8. Doutora, Ciências: Genética. Professora adjunta, Departamento de Genética, UFRGS, Porto Alegre, RS. Serviço de Genética Médica, Hospital de Clínicas de Porto Alegre (HCPA), UFRGS, Porto Alegre, RS. Não foram declarados conflitos de interesse associados à publicação deste artigo. Apoio financeiro: FIPE, CNPq e CAPES. Como citar este artigo: Giugliani L, Sitta A, Vargas CR, Santana-da-Silva LC, Nalin T, Saraiva-Pereira ML, et al. Tetrahydrobiopterin responsiveness of patients with phenylalanine hydroxylase deficiency. J Pediatr (Rio J). 2011;87(3):245-251. Artigo submetido em 25.10.10, aceito em 16.02.11. doi:10.2223/JPED.2090 245 246 Jornal de Pediatria - Vol. 87, Nº 3, 2011 Responsividade ao BH4 em pacientes com PKU - Giugliani L et al. Introdução das avaliações. No primeiro dia (dia pré-BH4 ou dia 1), os A hiperfenilalaninemia por deficiência de fenilalanina hi- pacientes foram submetidos a coletas de sangue às 8/12/16 droxilase (HPA-PAH), comumente chamada de fenilcetonúria h ou 9/13/17 h (ponto 0/ ponto 1/ ponto 2, respectivamen- (PKU), é um dos erros inatos do metabolismo mais frequentes te), para avaliar a variação dos níveis de Phe. No segundo e o primeiro a ser tratado por dietoterapia1. O tratamento dia (dia 2), foi aplicado um protocolo modificado do teste de 13 clássico para essa doença baseia-se em uma dieta com baixo sobrecarga com BH4 , com administração oral de uma única teor de fenilalanina (Phe). A restrição dietética de Phe prote- dose de 20 mg/kg de BH4 em todos os pacientes. ge o sistema nervoso central dos efeitos tóxicos da doença, As coletas de sangue no dia 2 foram realizadas nos pon- prevenindo as manifestações clínicas associadas. Contudo, a tos de hora 0, 4 e 8 h (ponto 0 ou basal, ponto 1 e ponto 2, dietoterapia é complexa e de longa duração. A baixa adesão respectivamente), após a ingestão do medicamento. A coleta ao tratamento é um problema enfrentado principalmente de sangue no dia 3 foi realizada 24 h após a ingestão do no atendimento a adolescentes e adultos, uma vez que as medicamento (ponto 3). Os níveis de Phe no sangue foram opções dietéticas são muito restritas2. determinados através da espectrometria de massa in tandem Desde a publicação de Kure et al.3, que relatou os pri- (MS/MS) no Laboratório de Erros Inatos do Metabolismo do meiros pacientes com HPA-PAH, cujos níveis plasmáticos de SGM/HCPA. Todas as dosagens foram realizadas em dupli- Phe diminuíram com a utilização oral de tetrahidrobiopterina cata, sendo a média entre as duas dosagens considerada como resultado final. (BH4), vários outros estudos, usando protocolos diferentes e doses variadas de BH4, demonstraram que pacientes com Os pacientes foram instruídos a permanecer em jejum HPA-PAH podem ter os seus níveis de Phe melhor controlados por aproximadamente uma hora antes de todas as coletas de 4-7 mediante a administração oral de BH4 . A partir desses estu- sangue. Caso algum dos pacientes não apresentasse níveis de dos, ficou evidente que a maioria dos indivíduos responsivos Phe ≥ 6 mg/dL no ponto 0 do dia 2 (dia da sobrecarga com ao BH4 pertence ao grupo com “Fenilcetonúria leve” (PKU BH4), o mesmo seria instruído a repetir esse protocolo em leve) e que cerca de 20 a 50% dos pacientes com HPA-PAH momento posterior, e o teste inicial não era considerado. alcançam redução ≥ 30% dos níveis de Phe associada ao uso de BH 8. Os dados disponíveis sugerem que a presença ou 4 Responsividade ao BH4 ausência de responsividade ao BH é multifatorial, sendo o 4 Foram utilizados dois critérios de responsividade ao BH , genótipo um dos seus fatores determinantes9-11. 4 uma vez que não existe consenso sobre o melhor critério a Nesse contexto, este trabalho propõe um estudo inédito ser utilizado: no Brasil, com o objetivo de identificar indivíduos responsivos critério 1: redução ≥ 30% de Phe após 8 h da adminis- à administração de BH por via oral. 4 tração do medicamento8; critério 2: redução ≥ 30% de Phe após 24 h da adminis- Metodologia tração do medicamento13. Esse é um estudo intervencional, aprovado pelo Comitê de Ética em Pesquisa do Hospital de Clínicas de Porto Alegre Consumo dietético de Phe (HCPA). A participação da indústria farmacêutica limitou-se à Todos os pacientes foram instruídos a continuar a mesma doação da BH (sapropterina dihidrocloride, Kuvan®) neces- 4 prescrição dietética de Phe em que estavam antes do início sária para a realização do estudo. Foram avaliados pacientes do estudo (ou seja, dieta usual restrita em Phe). O consumo com HPA-PAH atendidos no Ambulatório de Tratamento de de Phe ao longo do estudo foi verificado por meio de inqué- Distúrbios Metabólicos do Serviço de Genética Médica do rito alimentar de 3 dias, que foi aplicado do dia anterior à Hospital de Clínicas de Porto Alegre (ATDM-SGM/HCPA). Todos vinda dos pacientes ao SGM/HCPA até o dia da sobrecarga os pacientes e/ou seus responsáveis assinaram o termo de com o BH4 inclusive. O consumo de Phe foi obtido através consentimento livre e esclarecido. do cálculo do inquérito alimentar de cada dia, utilizando-se Foram incluídos no estudo pacientes com idade ≥ 7 anos e o programa de apoio à nutrição DietWin Profissional® 2008 que possuíam níveis séricos de Phe ≥ 6 mg/dL nos 12 meses (DietWin, Porto Alegre, RS).
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