Autism: Is there a folate connection?

Autism is increasing-but why? Birth defect prevention trials were based on the teleological assumption that folic acid could prevent neural tube defects without consideration of long-term effects, some of which could be beneficial, some of which might be harmful. We therefore ask-Is it impossible to look again at these cohorts?

The significance of neopterin and biopterin concentrations at presentation in haematological malignancies.

Urinary neopterin and biopterin concentrations were measured in 32 healthy controls and 53 patients with newly diagnosed haematological malignancies classified and staged by accepted criteria. The neopterin concentrations were only significantly raised in chronic lymphocytic leukaemia at stages III-IV. Total biopterin concentrations after oxidation with iodine at acid pH were decreased in chronic lymphocytic leukaemia stages O-II, multiple myeloma, and acute myeloid leukaemia but not in chronic lymphocytic leukaemia stages III-IV. Although of research interest, neopterin concentrations proved of little prognostic value at presentation, but taken with the biopterin concentration they may be useful for the assessment of tumour activity.

Neuroblastoma in a patient with dihydropteridine reductase deficiency.

Tetrahydrobiopterin (BH4) deficiency is a rare cause of hyperphenylalaninaemia (HPA) and usually leads to progressive neurological deterioration despite early dietary control of plasma phenylalanine concentrations. Dihydropteridine reductase (DHPR) deficiency is the most severe cause with respect to a fatal outcome. We report a 7-year-old girl with HPA diagnosed on neonatal Guthrie screening who at the age of 6 months had cytotoxic therapy for an adrenal neuroblastoma which secreted catecholamines. When 4 years old she was found to have DHPR deficiency. Although developmentally retarded and microcephalic she has failed to develop the florid neurological features often associated with the condition.

Dihydropteridine reductase activity in eluates from dried blood spots: automation of an assay for a national screening service.

We describe the automation, using a Cobas Bio centrifugal analyser, of a method for dihydropteridine reductase (DHPR) assay in eluates from dried blood spots. This is used as part of a routine screening service of neonates with hyperphenylalaninaemia in the United Kingdom. Automation reduced reagent volumes and analysis time by about 80% and improved the precision of the assay. Relating DHPR activity to haemoglobin concentration of the eluate further improved the precision of the assay and removed some differences in 'apparent' DHPR activity between samples from different countries and different age groups.

The effect of folic acid and 5-formyltetrahydrofolic acid on folate-deficient HEp 2 cells in culture.

Folic acid has less effect than 5-formyltetrahydofolic acid (folinic acid) in the alleviation of folate deficiency in cultured HEp 2 cells as measured by the deoxyuridine suppression test. Folic acid inhibits the metabolism of 5-formyltetrahydrofolic acid in vitro, is contraindicated in some cases of clinical folate deficiency and may be inappropriate in others.

Biopterin and neurotransmitter amine metabolism in children with acute lymphoblastic leukemia receiving methotrexate therapy.

To test the hypothesis that some of the neurologic sequelae of treatment for acute lymphoblastic leukemia (ALL) might be related to abnormalities in biopterin metabolism associated with methotrexate (MTX) therapy, total biopterin levels in cerebrospinal fluid (CSF) and plasma, and homovanillic acid (HVA) and 5-hydroxyindoleacetic acid (5HIAA) were measured in a cross-sectional study of 80 children with ALL. For comparison, biopterins were also measured in a group of children of similar age undergoing investigation for neurologic disease. In children with ALL studied before therapy, no significant difference was found between the means of plasma biopterin or CSF biopterin concentrations and the means in the control group. In children receiving MTX, plasma biopterin values were higher in the group given maintenance therapy than in children observed before treatment. CSF levels were significantly increased only in those patients who had completed 2 years of maintenance therapy. CSF concentrations of HVA and 5HIAA in patients with ALL who had received no treatment (median values 52 and 18 ng/ml, respectively) showed a wide scatter and were inversely related to age. In patients receiving MTX, concentrations of these metabolites were higher than in the untreated group, again reaching a peak in patients just completing 2 years of treatment (median HVA 110 ng/ml, 5HIAA 34 ng/ml). These results provide no support for the idea that neurotransmitter amine deficiency occurs in children with ALL receiving MTX, and indicate, rather, that amine and biopterin synthesis increases in such patients.

The effects of pathological and normal physiological processes on biopterin derivative levels in man.

Mean serum biopterin derivative levels in adult males and females were 1.75 microgram/l and 1.53 microgram/l respectively, increased with age and followed a cyclic pattern during menstruation. Foetal brain and liver levels at 16 weeks approximated adult concentrations. Wide distribution in adult tissues and variation in concentration independent of serum levels demonstrated local synthesis. Serum levels were significantly decreased in senile dementia, lead poisoning, coeliac disease and malignant carcinoid disease. Abnormal metabolism of phenylalanine in senile dementia suggest lowered levels of tetrahydrobiopterin in tissue. Methotrexate increased serum biopterin levels by inhibition of dihydropteridine reductase; a saturation effect was noted.

Biopterin defect in a normal-appearing child affected by a transient phenylketonuria.

A child diagnosed as having transient phenylketonuria was found to have reduced synthesis of tetrahydrobiopterin and an abnormal clearance of phenylalanine, but he remained clinically normal when on a normal diet. A small amount of 7,8-dihydrobiopterin was found in his serum; this distinguishes the case from that of malignant hyperphenylalaninaemia.

[Hyperphenylalaninaemia with normal phenylalanine-hydroxylase activity and a deficiency of tetrahydrobiopterin and dihydropteridine reductase]. / Les hyperphenylalaninemies avec activite normale de la phenylalanine-hydroxylase le deficit en tetrahydrobiopterine et le deficit en dihydropteridine reductase.

Two cases of hyperphenylalaninemia with a normal activity of phenylalanine hydroxylase are described. No activity of DHP reductase was found in the first case, having very high biopterin levels in basal conditions and after intravenous perfusion of phenylalanine. In the other case, the DHP reductase activity is normal but plasma and urinary levels of the reduced forms of biopterin are largely lowered and do not increase during the phenylalanine load. Early substitutive treatment with L-dopa and 5-HTP in one of the cases avoided the development of the "progressive neurological illness unresponsive to dietary treatment" characterizing two variants. This raises the question of a liver biopsy in order to assay the hydroxylation enzyme activities when screening hyperphenylalaninemia whatever the type.

Serum folates in man.

In an aseptic microbiological assay of folate compounds and their breakdown compounds, using Lactobacillus casei, Streptococcus faecalis, and Pediococcus cerevisiae, 4a-hydroxy-5methyl-4,5,6,7-tetrahydrofolate and 5-methyl-5,8-dihydrofolate were inactive under all conditions to all three organisms and 5-methyl-5,6-dihydrofolate was inactive unless ascorbate was present in the incubation medium, and then only to L. casei. 5-Methyltetrahydrofolate was active only for L. casei, and activity in purified samples to S. faecalis was due to trace amounts of folic acid. Analysis of S. faecalis values in the serum in normal subjects and in patients with various disorders showed that levels of 10-formyltetrahydrofolate are raised in coeliac disease, leukaemia, rheumatoid arthritis, and schizophrenia. 5-Methyltetrahydrofolate is readily absorbed by normal human subjects and by patients with pernicious anaemia but poorly absorbed by patients with coeliac disease or leukaemia. 5-Methyl-5,6-dihydrofolate was quickly absorbed by normal human subjects, being reflected by a considerably raised level of 5-methyltetrahydrofolate in serum when sodium bicarbonate was given by mouth before the 5-methyl-5,6-dihydrofolate. These higher levels were comparable to those in patients with pernicious anaemia after oral administration of 5-methyl-5,6-dihydrofolate. Oral 5-methyl-5,8-dihydrofolate and 4a-hydroxy-5-methyl-tetrahydrofolate did not appear as microbiologically active folates in the serum. The findings of this study suggest that the availability for biological utilisation of the major dietary folate compounds will depend on the amount of gastric acidity and of ascorbate in the intestinal chyme. Many may be unavailable for metabolic utilization in the body.

Biopterin derivatives in human body fluids and tissues.

Levels of biopterin derivatives in urine, serum, milk, cerebrospinal fluid, brain, and liver have been measured with the Crithidia fasciculata assay. Normal levels in serum and urine have been given and compared with those in a number of benign and malignant proliferative disorders, phenylketonuria, kidney disease, Parkinson's disease, schizophrenia, controlled epilepsy, rheumatoid arthritis, and pernicious anaemia. The active component of Crithidia factor in serum was 7,8-dihydrobiopterin. Tissue, urine, and some serum samples contained two active materials, the principal one being 7,8-dihydrobiopterin; a minor constituent was probably tetrahydrobiopterin. Serum biopterin levels following methotrexate administration were raised and subsequent administration of folic acid and 5-formyltetrahydrofolic acid further increased serum levels of biopterin derivatives; this was in contrast to the total absence of response to oral folates without prior methotrexate and to 5-methyltetrahydrofolic acid either with or without methotrexate being given.

Folates in human serum.

Constituent serum folates have been shown to be altered and in some cases raised in diseases in which total folate levels are known to be frequently decreased. Absorption experiments showed that orally administered folate analogues affect the folate pool in different ways. The stability of the 10-formyltetrahydrofolate level in normal subjects is demonstrated.