Phenylalanine and Tyrosine Metabolism Analysis in Heterozygotes for Phenylketonuria and in Healthy Individuals

Andrade, Roseani; Monteiro, Vaneisse Cristina Lima; Cruz, Cléber Monteiro; Silva, Carla; Bastos, A.B.; Silva, Luiz

doi:10.1177/2326409815573962

Cited by 3 publications

(2 citation statements)

References 24 publications

(35 reference statements)

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“…Plasma Phe concentrations were determined with a fluorometric assay (Shimadzu, RF-5301PC, USA). 31 Serum vitamin B12, folate and ferritin were evaluated by the chemiluminescence immunoassay method (ABBOTT, Architect i200, USA). Plasma samples for Hcy measurements were centrifuged at 4°C and 3000 r/min for 10 min (Hettich, Rotina 35 R, Germany).…”

Section: Methodsmentioning

confidence: 99%

Functional vitamin B12 deficiency in phenylketonuria patients and healthy controls: An evaluation with combined indicator of vitamin B12 status as a biochemical index

Akış

Kant

Işık³

et al. 2020

Ann Clin Biochem

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Background Vitamin B12 deficiency frequently appears in phenylketonuria patients having a diet poor in natural protein. The aims of this study were to evaluate vitamin B12 status in phenylketonuria patients by using combined indicator of vitamin B12 status (cB12) as well as methylmalonic acid and homocysteine, more specific and sensitive markers, in comparison with healthy controls. Methods Fifty-three children and adolescents with phenylketonuria under dietary treatment and 30 healthy controls were assessed cross-sectionally. Serum vitamin B12 and folate concentrations were analysed by chemiluminescence immunoassay. Plasma methylmalonic acid and total homocysteine concentrations were measured by liquid chromatography-tandem mass spectrometry and liquid chromatography, respectively. cB12 was calculated by using a formula involving blood parameters. Results Methylmalonic acid and folate concentrations in phenylketonuria group were higher compared with controls. Methylmalonic acid concentrations were high in 56.5% of the patients and 26.7% of the controls with normal vitamin B12 concentrations. Based on cB12, a significant difference within the normal values was detected between the groups. However, although 24.5% of phenylketonuria patients and 13.3% of controls had decreased vitamin B12 status according to cB12, there was no significant difference. Conclusion Children and adolescents with phenylketonuria having a strict diet can be at risk of functional vitamin B12 deficiency. This deficiency can be accurately determined by measuring methylmalonic acid concentrations. Calculation of cB12 as a biochemical index did not provide additional information compared with the measurement of methylmalonic acid alone, but may be helpful for classification of some patients with increased methylmalonic acid as having adequate vitamin B12 status.

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Section: Methodsmentioning

confidence: 99%

Functional vitamin B12 deficiency in phenylketonuria patients and healthy controls: An evaluation with combined indicator of vitamin B12 status as a biochemical index

Akış

Kant

Işık³

et al. 2020

Ann Clin Biochem

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“…Таким образом, способность метаболизировать ФА в тирозин у гетерозиготных носителей также ограничена. Было установлено, что у гетерозигот уровень метаболизма ФА снижен и сопровождается более длительными пиковыми его концентрациями в крови [4].…”

Section: Introductionunclassified

Prenatal diagnosis of phenylketonuria and bilateral renal agenesis in a fetus

Веропотвелян¹,

Макух²,

Chorna³

et al. 2018

Reproductive Endocrinology

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Phenylketonuria ( PKU )

Gonzalez-Lopez

McFalls

Vrana

2016

Encyclopedia of Life Sciences

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Phenylketonuria (PKU) is one of the first characterised metabolic diseases. PKU is an autosomal recessive metabolic disorder resulting in increased phenylalanine concentrations. Without intervention, such as pharmaceutical or dietary restriction of phenylalanine, most children with PKU develop a profound and irreversible intellectual disability. In fact, this treatable condition is one of the leading causes of mental retardation. PKU can occur via two main mechanisms: classical and nonclassical. Classical PKU results from impaired activity of the liver enzyme phenylalanine hydroxylase, which converts phenylalanine to tyrosine. In nonclassical PKU, there is an absence or deficiency of dihydropteridine reductase which impairs the regeneration of tetrahydrobiopterin, a necessary cofactor in the conversion of phenylalanine to tyrosine. The advent of neonatal screening for PKU has enabled the start of a low‐phenylalanine diet early in life and thus, the prevention of intellectual retardation associated with the disease. The mainstay of treatment is a phenylalanine‐restricted diet, but its application varies both internationally and nationally. Key Concepts Phenylketonuria (PKU) is a rare metabolic disorder, characterised by an impaired ability to metabolise the amino acid phenylalanine and resultant high circulating levels of phenylalanine. Classical PKU (the most common form) is caused by mutations in the gene for phenylalanine hydroxylase (PAH). Nonclassical PKU can be caused by defects in the synthesis or function of the cofactor for PAH (BH 4 ). If not treated shortly after birth, PKU can be destructive to the nervous system, causing intellectual disability. The identification of PKU during routine newborn screening and management with a diet low in phenylalanine became standard practice in the early 1960s. PKU is a disorder that has an unequal geographic and ethnic distribution. Individuals on well‐controlled phenylalanine‐free diet may still develop cognitive symptoms. Several new therapies have recently emerged that provide alternatives to the strict low‐phenylalanine diet. A description of these treatments (medical foods, BH 4 administration, large neutral amino acid supplementation and enzymatic therapy) is covered herein.

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Phenylalanine and Tyrosine Metabolism Analysis in Heterozygotes for Phenylketonuria and in Healthy Individuals

Cited by 3 publications

References 24 publications

Functional vitamin B12 deficiency in phenylketonuria patients and healthy controls: An evaluation with combined indicator of vitamin B12 status as a biochemical index

Functional vitamin B12 deficiency in phenylketonuria patients and healthy controls: An evaluation with combined indicator of vitamin B12 status as a biochemical index

Prenatal diagnosis of phenylketonuria and bilateral renal agenesis in a fetus

Phenylketonuria ( PKU )

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