Amj van Wegberg1, Raf Evers1, Jgm Burgerhof2, E van Dam1, M R Heiner-Fokkema3, McH Janssen4, M C de Vries5, F J van Spronsen6. 1. Division of Metabolic Diseases, Beatrix Children's Hospital, University Medical Center Groningen, University of Groningen, the Netherlands. 2. Department of Epidemiology, University Medical Center Groningen, University of Groningen, Groningen, the Netherlands. 3. Department of Laboratory Medicine, Laboratory of Metabolic Diseases, University of Groningen, University Medical Centre Groningen, the Netherlands. 4. Department of Internal Medicine, Radboudumc, Nijmegen, the Netherlands. 5. Department of Pediatrics, Radboudumc Nijmegen, the Netherlands. 6. Division of Metabolic Diseases, Beatrix Children's Hospital, University Medical Center Groningen, University of Groningen, the Netherlands. Electronic address: f.j.van.spronsen@umcg.nl.
Abstract
BACKGROUND: In patients with phenylketonuria, stability of blood phenylalanine and tyrosine concentrations might influence brain chemistry and therefore patient outcome. This study prospectively investigated the effects of tetrahydrobiopterin (BH4), as a chaperone of phenylalanine hydroxylase on diurnal and day-to-day variations of blood phenylalanine and tyrosine concentrations. METHODS:Blood phenylalanine and tyrosine were measured in dried blood spots (DBS) four times daily for 2 days (fasting, before lunch, before dinner, evening) and once daily (fasting) for 6 days in a randomized cross-over design with a period with BH4 and a period without BH4. The sequence was randomized. Eleven proven BH4 responsive PKU patients participated, 5 of them used protein substitutes during BH4 treatment. Natural protein intake and protein substitute dosing was adjusted during the period without BH4 in order to keep DBS phenylalanine levels within target range. Patients filled out a 3-day food diary during both study periods. Variations of DBS phenylalanine and Tyr were expressed in standard deviations (SD) and coefficient of variation (CV). RESULTS:BH4 treatment did not significantly influence day-to-day phenylalanine and tyrosine variations nor diurnal phenylalanine variations, but decreased diurnal tyrosine variations (median SD 17.6 μmol/l, median CV 21.3%, p = 0.01) compared to diet only (median SD 34.2 μmol/l, median CV 43.2%). Consequently, during BH4 treatment diurnal phenylalanine/tyrosine ratio variation was smaller, while fasting tyrosine levels tended to be higher. CONCLUSION:BH4 did not impact phenylalanine variation but decreased diurnal tyrosine and phenylalanine/tyrosine ratio variations, possibly explained by less use of protein substitute and increased tyrosine synthesis.
RCT Entities:
BACKGROUND: In patients with phenylketonuria, stability of blood phenylalanine and tyrosine concentrations might influence brain chemistry and therefore patient outcome. This study prospectively investigated the effects of tetrahydrobiopterin (BH4), as a chaperone of phenylalanine hydroxylase on diurnal and day-to-day variations of blood phenylalanine and tyrosine concentrations. METHODS: Blood phenylalanine and tyrosine were measured in dried blood spots (DBS) four times daily for 2 days (fasting, before lunch, before dinner, evening) and once daily (fasting) for 6 days in a randomized cross-over design with a period with BH4 and a period without BH4. The sequence was randomized. Eleven proven BH4 responsive PKUpatients participated, 5 of them used protein substitutes during BH4 treatment. Natural protein intake and protein substitute dosing was adjusted during the period without BH4 in order to keep DBSphenylalanine levels within target range. Patients filled out a 3-day food diary during both study periods. Variations of DBSphenylalanine and Tyr were expressed in standard deviations (SD) and coefficient of variation (CV). RESULTS:BH4 treatment did not significantly influence day-to-day phenylalanine and tyrosine variations nor diurnal phenylalanine variations, but decreased diurnal tyrosine variations (median SD 17.6 μmol/l, median CV 21.3%, p = 0.01) compared to diet only (median SD 34.2 μmol/l, median CV 43.2%). Consequently, during BH4 treatment diurnal phenylalanine/tyrosine ratio variation was smaller, while fasting tyrosine levels tended to be higher. CONCLUSION:BH4 did not impact phenylalanine variation but decreased diurnal tyrosine and phenylalanine/tyrosine ratio variations, possibly explained by less use of protein substitute and increased tyrosine synthesis.
Authors: Nasser A Elhawary; Imad A AlJahdali; Iman S Abumansour; Ezzeldin N Elhawary; Nagwa Gaboon; Mohammed Dandini; Abdulelah Madkhali; Wafaa Alosaimi; Abdulmajeed Alzahrani; Fawzia Aljohani; Ehab M Melibary; Osama A Kensara Journal: Hum Genomics Date: 2022-07-19 Impact factor: 6.481