7-8-dihydrobiopterin and Phenylketonurias

Topics: Alleles; Amino Acid Metabolism, Inborn Errors; Animals; Biopterins; Dihydropteridine Reductase; Female; Fetal Diseases; Gene Frequency; Genetic Carrier Screening; Heterozygote; Humans; Hydroxylation; Phenylalanine; Phenylalanine Hydroxylase; Phenylketonurias; Pregnancy; Pregnancy Complications; Rats

A liquid chromatographic method for the simultaneous analysis of marker pteridins and biopterin reduced forms, in urine samples is proposed. A Zorbax Eclipse XDB-C18 column was used for the chromatographic separation, using a 98/2 (v/v), citrate buffer (pH 5.5)-acetonitrile mobile phase, in isocratic mode. A post-column photoderivatization was carried out with an on-line photoreactor, located between a diode array detector (DAD) and a fast scanning fluorescence detector (FSFD). Neopterin (NEO), biopterin (BIO), pterin (PT) and dihydrobiopterin (BH2) were determined by measuring native fluorescence, using the photoreactor in OFF-mode, and tetrahydrobiopterin (BH4) was determined by measuring of the induced fluorescence of the generated photoproducts, using the photoreactor in ON-mode. In addition, Creatinine (CREA), as a reference of metabolites excrection in urine, was simultaneously determined using the DAD detector. Detection limits were 0.2, 13.0, 0.3, 0.3 and 3.5 ng mL(-1), for NEO, BH2, BIO, PT and BH4, respectively, and 0.4 microg mL(-1) for CREA. Ratio values for NEO/CREA, PT/CREA, BH4/CREA, BH2/CREA, NEO/BIO and BIO(total)/CREA, in urine samples, of healthy children and adults, phenylketonuric children and infected mononucleosis children, are reported. A comparative study, about the mean values obtained for each of the compounds, by the present procedure and by the classical iodine oxidation method (Fukushimas method), has been performed, in urine samples belonging to healthy volunteers. The values obtained were BH4/CREA: 0.41, BH2/CREA: 0.31 and BIO(total)/CREA: 0.73, by the proposed method, and BH4/CREA: 0.35, BH2/CREA: 0.20 and BIO(total)/CREA: 0.48, by iodine oxidation method.

Topics: Adult; Biomarkers; Biopterins; Child; Chromatography, High Pressure Liquid; Female; Fluorescent Dyes; Humans; Infectious Mononucleosis; Male; Phenylketonurias; Pteridines

Several reports indicate that biopterin and folate pathways may interact. We examined folate metabolism in PKU patients where hyperphenylalaninaemia leads to a likely excess of THB. We found an increase in total HPLC determined red cell folate in PKU (p=0.0422): specifically, there was an increase in total formyl-H(4)folate (p=0.0002) and H(4)folate (p< or =0.0001), and decrease in total 5-methyl-H(4)folate in PKU patients. At the level of individual oligo-gamma-glutamyl coenzymes, we found that formyl-H(4)folate polyglutamates were virtually all increased in PKU (p=0.0223, 0.0004, 0.0004, 0.0012, and 0.0008 for di-, tri-, tetra-, penta-, and deca-gamma-glutamyl formyl-H(4)folate coenzymes, respectively). Hcy levels did not differ between clinical groups, indicating that folate dependent-Hcy remethylation is not compromised as a consequence of an altered PKU folate disposition. In nature, pentaglutamyl folates are considered the metabolically favoured coenzymes (optimum K(m) for dependent enzymes). The presented data support this-we found that red cell pentaglutamates gave the best measure of metabolism; pentaglutamyl formyl-H(4)folate increased in PKU (p=0.0012) and related methenyls behaved similarly, while, pentaglutamyl 5-methyl-H(4)folate and pentaglutamyl H(4)folate decreased (p< or =0.0001 and 0.0265, respectively). Furthermore, pentaglutamates showed the best correlations between one-carbon oxidation states of folate, as well as with Hcy (p=0.0003 r=-0.54, 95% CI; -0.724 to -0.272). That PKU might influence folate metabolism in some way is unsurprising: patients with DHPR deficiency accumulate DHB and develop secondary folate deficiency-responsive only to reduced folates, while CSF levels of THB are significantly correlated to monoamines and red cell folate in depression. Further studies to confirm the present findings and to ascertain precisely what mechanism operates in PKU that impacts upon folate homeostasis so profoundly are required.

Topics: Biopterins; Chromatography, High Pressure Liquid; Coenzymes; Folic Acid; Homocysteine; Humans; Immunoassay; Phenylalanine; Phenylketonurias

Topics: Biopterins; Child, Preschool; Dopamine Agents; Dystonia; Family Health; Female; GTP Cyclohydrolase; Humans; Infant; Levodopa; Male; Muscle, Skeletal; Mutation; Phenylketonurias; Phosphorus-Oxygen Lyases

Topics: Adult; Biopterins; Circadian Rhythm; Humans; Intellectual Disability; Male; Movement Disorders; Phenylalanine; Phenylketonurias

A defect in the synthesis of dihydrobiopterin was detected in an Arab girl, ascertained through high blood phenylalanine level on neonatal screening. An oral loading test with tetrahydrobiopterin (BH4) caused a significant fall in her blood phenylalanine and a rise in tyrosine concentrations. Her blood biopterin levels were low. In urine and cerebrospinal fluid (CSF) very high neopterin and low biopterin levels were observed. A deficiency of metabolites of neurotransmitters, serotonin and dopamine, was observed in CSF and urine. The patient was given replacement therapy of BH4, 5-hydroxytryptophan, and L-dopa with carbidopa starting from the age of 16 to 18 weeks. On this treatment the blood phenylalanine levels dropped to the desired range, while in urine and CSF a satisfactory rise of neurotransmitter metabolites was observed. In spite of this biochemical control, the patient developed neurological symptoms with myoclonic jerks and changes in muscle tone and presented severe cerebral damage with mental retardation. She died suddenly at the age of 38 weeks.

Topics: 5-Hydroxytryptophan; Biopterins; Carbidopa; Drug Combinations; Female; Humans; Infant, Newborn; Levodopa; Male; Nervous System Diseases; Phenylalanine; Phenylketonurias; Pteridines; Tyrosine

We describe a method of screening for dihydropteridine reductase deficiency and dihydrobiopterin synthesis deficiency--the two inherited defects that cause tetrahydrobiopterin deficiency--using blood spots on Guthrie cards. Dihydropteridine reductase deficiency may be identified positively, and a biopterin value of less than 6.0 micrograms/l in the presence of hyperphenylalaninaemia indicates further investigation for dihydrobiopterin synthesis deficiency.

Topics: Adolescent; Adult; Biopterins; Child; Child, Preschool; Dihydropteridine Reductase; Humans; Infant, Newborn; Methods; Phenylalanine; Phenylketonurias; Pteridines; Specimen Handling

Topics: Alcohol Oxidoreductases; Biopsy, Needle; Biopterins; Child; Child, Preschool; Humans; Infant; Infant, Newborn; Liver; Phenylalanine; Phenylketonurias; Pteridines; Pterins

The first Scandinavian hyperphenylalaninaemic patient with a cofactor deficiency is described. By neonatal screening the Guthrie test showed a serum phenylalanine of 302 mumol/1 (5 mg/dl), which at age 6 weeks had fallen to high normal values. At age 5 1/2 months the serum phenylalanine was around 2000 mumol/1 and the child presented with severe neurological symptoms. The diagnosis of defect dihydrobiopterin biosynthesis was made by high performance liquid chromatography of the urine. Loading tests followed by daily treatment of the missing cofactor was able to keep the serum phenylalanine in the normal level. Because of persisting, yet diminishing neurological symptoms neurotransmitter treatment was started. Breast feeding as the cause of the low neonatal levels of serum phenylalanine and the late start of clinical symptoms is proposed and the importance of screening all hyperphenylalaninaemic newborns for defect biopterin metabolism is stressed.

Topics: 5-Hydroxytryptophan; Biopterins; Carbidopa; Chromatography, High Pressure Liquid; Dihydroxyphenylalanine; Humans; Infant; Male; Nervous System Diseases; Phenylalanine; Phenylketonurias; Pteridines

A patient with atypical phenylketonuria and normal liver dihydropteridine reductase and phenylalanine-4-hydroxylase activities excreted neopterin but not biopterin or dihydrobiopterin in urine. The oral administration of L-sepiapterin (1 mg/kg body weight) lowered serum-henylalanine from 17.1 to 1.1 mg/dl within 6 h. Comparable responses were observed after oral administration of L-erythro-7, 8-dihydrobiopterin or L-erythro-5, 6, 7, 8-tetrahydrobiopterin (each given in a dose of 2.5 mg/kg body weight). The results indicate a 7, 8-dihydrobiopterin synthetase deficiency in the patient.

Topics: Alcohol Oxidoreductases; Biopterins; Child, Preschool; Female; Guanosine Triphosphate; Humans; Phenylalanine; Phenylketonurias; Pteridines; Pterins

A patient with atypical phenylketonuria (defective BH2 synthesis), detected at age 6 months because of severe muscle hypotonia and serum phenylalanine of 20 mg/100 ml, had normal activities of phenylalanine-4-hydroxylase and DHPR in liver biopsy, but only 2% activity in the phenylalanine-4-hyroxylase in vivo test using deuterated phenylalanine. After IV administration of 2.5 mg/kg chemically pure tetrahydrobiopterin bishydrochloride (BH4 . 2HCl), serum phenylalanine decreased from 20.4 to 2.1 mg/100 ml within 3 hours. Administration of 25 mg BH4 . HCl and 100 mg ascorbic acid through a gastric tube decrease; serum phenylalanine from 13.7 to less than 1.6 mg/100 ml within 3 hours and it remained less than 2 mg/100 ml for 2 days.

Topics: Biopterins; Female; Humans; Infant; Phenylalanine; Phenylketonurias; Pteridines