Catrina Colomé

Children with stroke: polymorphism of the MTHFR gene, mild hyperhomocysteinemia, and vitamin status.

The aim of this study was to investigate a possible association among the thermolabile polymorphism, nucleotide 677 cytosine to thymidine point mutation (677 C→T) of the methylenetetrahydrofolate reductase (MTHFR) gene, hyperhomocysteinemia, serum folate, vitamins B12 and B6, and stroke in children. Allele and genotype frequencies for the 677 C→T polymorphism in 21 children with stroke and 28 healthy children of the same age were studied. No differences in allelic frequency were detected between the two populations. However, the prevalence of homozygous 677 C→T was doubled in the stroke population (28.6%) compared to the healthy group (14.3%). Total plasma homocysteine (tHcy) levels were significantly increased in children aged 2 months to 15 years with stroke compared to reference values. No association was observed between the homozygous genotype (T/T) and hyperhomocysteinemia, nor between the T/T genotype and low folate levels (below the 95th percentile) in this group of patients. Vitamin concentrations in patients were not significantly different from reference values. Significant negative correlations were found between tHcy and folate and between tHcy and cobalamin, but not between tHcy and B6 concentrations. In summary, a higher prevalence of hyperhomocysteinemia and the 677 C→T polymorphism were observed in children with stroke, but were not always associated. The systematic study of both abnormalities in children with stroke is recommended, so that hyperhomocysteinemia of any genetic origin can be corrected with vitamin supplementation. Moreover, the 677 C→T genotype is a strong factor for predisposition to hyperhomocysteinemia and recurrent risk of stroke that might also be prevented with folate supplementation. (J Child Neurol 2000;15:295-298).

Evaluation of hyperhomocysteinaemia in children with stroke.

Hyperhomocysteinaemia is associated with an increased risk of arterial vascular disease and thrombosis in adults. Our aim was to study the association of hyperhomocysteinaemia and stroke in children. Since some patients who had suffered a stroke developed seizures and received treatment with anti-epileptic (antifolate) drugs, we also examined the possible interaction between anti-epileptic drugs and hyperhomocysteinaemia. Plasma total homocysteine was measured in 68 children with stroke (23 of the 68 were taking anti-epileptic drugs) and 100 children undergoing anti-epileptic treatment but without history of stroke, and we compared the values with our reference values for similar ages (n = 195). Total homocysteine was determined by high profile liquid chromatography with fluorescence detection. Hyperhomocysteinaemia was defined as a homocysteine concentration above the 95th percentile for the reference values. Significant differences were found in total homocysteine values of children with stroke and those taking anti-epileptic drugs compared with our reference values for similar ages, except for the adolescent group. Total homocysteine values above the 95th percentile for the reference values were found in 36% of patients with stroke and 28% of children on anti-epileptic treatment. Total homocysteine concentrations in the 23 patients with both stroke and anti-epileptic drug treatment were similar to those of untreated patients with stroke in all age groups. In summary, systematic screening for hyperhomocysteinaemia should be included in the protocol to investigate the aetiology of stroke, even in paediatrics. Anti-epileptic treatment in children with stroke may be responsible for the mild hyperhomocysteinaemia observed in some of them. A dietary supplement of folate may be of benefit in children with stroke and in patients taking anti-epileptic drugs.

Hyperhomocysteinaemia and folate deficiency in human immunodeficiency virus-infected children.

Our aim was the detection of possible deficiencies of folate and cobalamin by the measurement of plasma total homocysteine (tHcy) in 69 human immunodeficiency virus (HIV) ‐infected children on antiretroviral treatment. We studied the relationship of these vitamins and methionine with tHcy values.

Is there a relationship between plasma phenylalanine and cholesterol in phenylketonuric patients under dietary treatment

OBJECTIVES To study the lipid profile in a group of treated phenylketonuric patients (PKU; n = 61) compared with a group of inborn error of intermediary metabolism patients (IEM; n = 22), a group of hyperphenylalaninemic children (HPA; n = 37), and a control group without dietary restriction (n = 41). DESIGN AND METHODS Phenylalanine was analyzed by ion exchange chromatography and triglycerides, cholesterol and HDL were determined by standard procedures with the Cobas Integra analyzer. RESULTS Serum total cholesterol concentrations were significantly lower in PKU patients compared with IEM patients (whose cholesterol daily intake was similar to those of PKU patients), HPA children and the control group. A negative correlation was observed between cholesterol and phenylalanine concentrations in the PKU patients. CONCLUSIONS Our findings support the hypothesis of a relationship between high plasma phenylalanine levels and an inhibition of cholesterogenesis, although the low cholesterol intake of the special diets may also decrease serum cholesterol values.

Personal experience with the application of carbohydrate-deficient transferrin (CDT) assays to the detection of congenital disorders of glycosylation.

Abstract Congenital disorders of glycosylation (CDG) are genetic multisystemic diseases due to various defects in the biosynthesis or processing of glycoproteins. Our aim is to present our experience in the selective screening of CDG syndrome in a paediatric population (421 patients) with clinical suspicion of the disease, analysing serum carbohydrate-deficient transferrin (CDT) by radioimmunoassay and/or immunoturbidimetry. We established the normal values for our paediatric population. The abnormal results were confirmed and classified by isoelectric focusing of serum sialotransferrins, and by enzymatic and molecular studies. We found 14 patients (3.3%) with abnormal serum CDT; 11 of them were classified as CDG type Ia (CDG-Ia) and the other three showed altered isoelectrofocusing patterns but remain untyped and are under investigation. In conclusion, both CDT assays proved to be useful tools for CDG screening. Isoelectric focusing is a simple procedure but it requires specific instruments that are not always available. Since the immunoturbidimetric procedure is commonly used to monitor for recent excessive alcohol consumption in clinical laboratories and does not require special equipment, it may also be reliably used to screen for CDG in children under clinical suspicion.

Monitoring of idebenone treatment in patients with Friedreich's ataxia by high-pressure liquid chromatography with electrochemical detection.

Idebenone is a quinone analog that is applied in the treatment of several neurological disorders including Friedreich ataxia and mitochondrial encephalomyopathies. Our aim was to develop an easy and sensitive analytical HPLC-procedure for the determination of idebenone in the serum of patients treated with this drug. Serum samples from nine paediatric patients diagnosed with Friedreich ataxia and receiving idebenone treatment were analyzed. Idebenone was separated from serum by reverse high-pressure liquid chromatography and analyzed using an electrochemical detection procedure. No interferences were observed during analysis of patient samples obtained prior to idebenone treatment. Calibration of idebenone concentration indicated a linear range between 500 pmol/l and 5 micromol/l and calculation of within-run and between-run coefficients of variation suggested adequate analytical quality for reliable determination. In agreement with previously reported data, during drug therapy, idebenone serum concentrations (basal conditions, range 0.1-0.49 micromol/l) were greatly elevated 90 min after an oral dose (range 0.66-3.63 micromol/l). Thus, we have developed a simple and rapid method that offers adequate analytical quality for accurate idebenone determination.

Oxygen consumption measurement in lymphocytes for the diagnosis of pediatric patients with oxidative phosphorylation diseases.

OBJECTIVES To evaluate the results of oxygen consumption measurement in lymphocytes for the diagnosis and treatment monitoring of pediatric patients with oxidative phosphorylation diseases. DESIGN AND METHODS Twenty-four children with an oxidative phosphorylation disease were studied. Results were compared with those of 87 healthy children. Oxygen consumption measurements in digitonine-permeabilized lymphocytes incubated with pyruvate plus malate and succinate were performed in a Clark-type oxygen electrode. RESULTS A total of 58% of patients showed a decreased oxygen consumption in lymphocytes incubated with pyruvate. In 4 patients, this analysis was the unique initial biochemical test, which revealed an impaired mitochondrial energy metabolism. Significant differences were observed in lymphocytes incubated with pyruvate between patients and reference values (p<0.00005), and in lymphocytes incubated with pyruvate before and after treatment (p<0.05). CONCLUSIONS This test is useful for diagnosing oxidative phosphorylation diseases in patients who did not have other biochemical alterations, although false-negative results can be found. It is not useful for treatment monitoring.