Chapter title |
Development of Metabolic Phenotype in Phenylketonuria: Evaluation of the Blaskovics Protein Loading Test at 5 Years of Age
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Chapter number | 508 |
Book title |
JIMD Reports, Volume 29
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Published in |
JIMD Reports, January 2015
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DOI | 10.1007/8904_2015_508 |
Pubmed ID | |
Book ISBNs |
978-3-66-253277-5, 978-3-66-253278-2
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Authors |
P. Burgard, E. Mönch, J. Zschocke, U. Wendel, U. Langenbeck, On behalf of the German Collaborative Study of Phenylketonuria (PKU)/Hyperphenylalaninaemia (HPA), Burgard, P., Mönch, E., Zschocke, J., Wendel, U., Langenbeck, U. |
Abstract |
As part of the German Collaborative Study on Phenylketonuria (PKU)/Hyperphenylalaninaemia (HPA) Study Protocol, a Blaskovics protein loading test (180 mg phenylalanine (phe) protein equivalent per kg body weight and day for 72 h) had been applied to 145 children at the age of 6 months. For investigating possible age-related changes of metabolic phenotype, 51 of them received a 2nd loading test at 5 years of age. Besides the analysis of blood phe levels, acidic phe transamination metabolites were quantified in urine. Compared to the 6-month data, the mean blood phe level 72 h after start of loading (Phe72) was found to be decreased by 7% (P = 0.06), whereas the mean urinary excretion (per 1.73 m(2) body surface and day) of 2-hydroxyphenylacetic acid was increased 1.9-fold (P < 0.01). Corresponding with these analytical data, the kinetic model constant k out of metabolic plus renal phe disposal was found increased 1.3-fold in mean (P < 0.01).In 3 of the 51 patients, Phe72 was very high at 6 months while in the medium range at 5 years, suggesting that catabolic states may mimic a more severe metabolic defect.The blood phe level response of mild PKU (type II) was assigned identically at both ages in 7/9 patients. Diverging results were (i) response type III (mild hyperphenylalaninaemia) at 6 months and type II at 5 years and (ii) type II at 6 months and type III at age 5. Renal elimination of OHPAA and phe tolerance increase significantly between the age of 6 months and 5 years, suggesting that, at least in childhood, formation and/or renal disposal of phe transamination metabolites may be major distal determinants of phe tolerance. |
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Unknown | 5 | 100% |
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Professor > Associate Professor | 1 | 20% |
Other | 1 | 20% |
Unknown | 1 | 20% |
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Unknown | 1 | 20% |