Tetrahydrobiopterin in phenylketonuria:Who can benefit?

Phenylketonuria, abbreviated PKU, is a rare inherited metabolic disease. In this disease, a building block of protein (an amino acid) called phenylalanine cannot be converted to tyrosine. This results in high phenylalanine concentrations in blood and brain. If left untreated, this especially results in severe developmental delay as well as epilepsy and behavioral problems. Lifelong treatment consists of a strict low protein diet, supplemented with an amino acid mixture not containing phenylalanine. Although the diet is very effective, it leads to a lot of social restrictions and is considered a great burden.Research looking at other treatment options has shown that several PKU patients benefit from treatment with BH4 (in full: tetrahydrobiopterin). In some patients, the medicine BH4 stimulates the conversion of phenylalanine to tyrosine. In this thesis I looked at methods to use to select those patients who benefit the most from treatment and also at the effects of BH4 on the brain.The results reported in this thesis show that using a BH4 loading test during at least 48 hours is preferential to only 24 hours (as was used a lot in the past), as otherwise some patients are falsely regarded as non-responders. Also, we concluded that patients with so called null-mutations (gene aberrations resulting in zero phenylalanine conversion) are no candidates for BH4 treatment. Finally, we conclude that BH4 possibly has an effect on the brain via influence on signal molecules (neurotransmitters). Although, a direct association is not yet shown

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The neonatal tetrahydrobiopterin loading test in phenylketonuria: what is the predictive value?

Contains fulltext : 171759.pdf (publisher's version ) (Open Access)BACKGROUND: It is unknown whether the neonatal tetrahydrobiopterin (BH4) loading test is adequate to diagnose long-term BH4 responsiveness in PKU. Therefore we compared the predictive value of the neonatal (test I) versus the 48-h BH4 loading test (test II) and long-term BH4 responsiveness. METHODS: Data on test I (>1991, 20 mg/kg) at T = 8 (n = 85) and T = 24 (n = 5) were collected and compared with test II and long-term BH4 responsiveness at later age, with >/=30 % Phe decrease used as the cut-off. RESULTS: The median (IQR) age at hospital diagnosis was 9 (7-11) days and the age at test II was 11.8 (6.6-13.7) years. The baseline Phe concentrations at test I were significantly higher compared to test II (1309 (834-1710) versus 514 (402-689) mumol/L, respectively, P = 0.000). 15/85 patients had a positive test I T = 8. All, except one patient who was not tested for long-term BH4 responsiveness, showed long-term BH4 responsiveness. In 20/70 patients with a negative test I T = 8, long-term BH4 responsiveness was confirmed. Of 5 patients with a test I T = 24, 1/5 was positive at both tests and showed long-term BH4 responsiveness, 2/5 had negative results at both tests and 2/5 showed a negative test I T = 24, but a positive test II with 1/2 showing long-term BH4 responsiveness. CONCLUSIONS: Both a positive neonatal 8- and 24-h BH4 loading test are predictive for long-term BH4 responsiveness. However, a negative test does not rule out long-term BH4 responsiveness. Other alternatives to test for BH4 responsiveness at neonatal age should be investigated

Microencephaly in fetal piglets following in utero inoculation of Zika virus article

Zika virus (ZIKV) is a mosquito-borne flavivirus that became associated with microcephaly in newborns and Guillain-Barré syndrome in adults after its emergence in the Pacific and the Americas in 2015. Newly developed rodent and nonhuman primate models have already revealed important insights into ZIKV-induced neuropathology. Nonhuman primates are phylogenetically closely related to humans and are therefore preferred human surrogates in ZIKV research. However, the use of nonhuman primates, particularly during gestation, raises ethical issues. Considering that pigs also share many anatomical and physiological features with humans, this species may be an attractive alternative human surrogate for ZIKV research. Here, we inoculated 20 porcine fetuses in utero and assessed the effect of ZIKV on brain development 4 weeks later. All inoculated fetuses presented mild to severe neuropathology, characterized by a depletion of neurons in the cerebral cortex. In most cases, neuronal depletion was confined to specific cerebral lobes without affecting brain size, whereas in severe cases a more generalized depletion resulted in microencephaly. Although the virus was widespread in the sows' placenta at the time of necropsy only low levels of viral RNA were detected in fetal brain samples, thereby preventing the identification of primary target cells. Our findings suggest that pigs can be used to study ZIKV-induced neurodevelopmental defects as currently observed in human neonates, varying from stunted brain growth to localized cortical neuronal depletion in the absence of major macroscopic abnormalities