Udo Wendel

Homocysteine-betaine interactions in a murine model of 5,10-methylenetetrahydrofolate reductase deficiency

Hyperhomocysteinemia, a proposed risk factor for cardiovascular disease, is also observed in other common disorders. The most frequent genetic cause of hyperhomocysteinemia is a mutated methylenetetrahydrofolate reductase (MTHFR), predominantly when folate status is impaired. MTHFR synthesizes a major methyl donor for homocysteine remethylation to methionine. We administered the alternate choline‐derived methyl donor, betaine, to wild‐type mice and to littermates with mild or severe hyperhomocysteinemia due to hetero‐ or homozygosity for a disruption of the Mthfr gene. On control diets, plasma homocysteine and liver choline metabolite levels were strongly dependent on the Mthfr genotype. Betaine supplementation decreased homocysteine in all three genotypes, restored liver betaine and phosphocholine pools, and prevented severe steatosis in Mthfr‐deficient mice. Increasing betaine intake did not further decrease homocysteine. In humans with cardiovascular disease, we found a significant negative correlation between plasma betaine and homocysteine concentrations. Our results emphasize the strong interrelationship between homocysteine, folate, and choline metabolism. Hyperhomocysteinemic Mthfr‐compromised mice appear to be much more sensitive to changes of choline/betaine intake than do wild‐type animals. Hyperhomocysteinemia, in the range of that associated with folate deficiency or with homozygosity for the 677T MTHFR variant, may be associated with disturbed choline metabolism.

White matter abnormalities in patients with treated hyperphenylalaninaemia : magnetic resonance relaxometry and proton spectroscopy findings

In order to further clarify the pathogenesis and clinical significance of MRI white matter abnormalities in treated hyperphenylalaninaemia (HPA), ten patients (seven type I HPA, two type II and one type III) underwent T2 relaxometry (n=8) and/or1H spectroscopy (n=7) in addition to conventional MR spin-echo imaging at 1.5 T. Two patients with severe MRI abnormalities had repeat examinations during and after a 6-to 8-month period of strict diet control. The clinical evaluation included a detailed neurological examination. In nine out of ten patients visual evoked potentials (VEP) were obtained parallel to the MR examination. MR imaging demonstrated typical symmetrical areas of prolonged T2 relaxation time predominantly in the posterior periventricular white matter in all but one of type I and II patients. There was no consistent relationship between MRI findings and time of diagnosis/initiation of therapy, IQ or visual evoked potential changes. MRI abnormalities tended to be more severe in patients with poor dietary control and high current plasma phenylalanine levels, whereas a normal MRI was found only in patients with plasma phenylalanine levels continuously below 0.36 mmol/l. There was marked regression of MRI abnormalities already after 3 months of strict diet control. T2 relaxometry showed a bi-exponential behaviour of T2 in the affected white matter, with a slow component of about 200–450 ms, indicating an increase in free (extracellular) water.1H spectroscopy revealed no signs of severe neuronal damage. We conclude, that the observed white matter changes in treated HPA probably represent reversible structural myelin changes rather than permanent demyelination.

MS/MS-based newborn and family screening detects asymptomatic patients with very-long-chain acyl-CoA dehydrogenase deficiency☆

OBJECTIVES To determine whether asymptomatic persons with biochemical evidence of very long-chain acyl-CoA dehydrogenase (VLCAD) deficiency identified through expanded newborn screening with tandem mass spectometry have confirmed disease. STUDY DESIGN We characterized 8 asymptomatic VLCAD-deficient individuals by enzyme and/or mutational analysis and compared them with clinically diagnosed, symptomatic patients with regard to mutations, enzyme activity, phenotype, and age of disease onset. RESULTS VLCAD molecular analyses in 6 unrelated patients revealed the previously reported V243A mutation, associated with hepatic or myopathic phenotypes, on 7/12 alleles. All other mutations were also missense mutations. Residual VLCAD activities of 6% to 11% of normal were consistent with milder phenotypes. In these identified individuals treated prospectively with dietary modification as preventive measures, clinical symptoms did not develop during follow-up. CONCLUSIONS MS/MS-based newborn screening correctly identifies VLCAD-deficient individuals. Based on mutational and enzymatic findings, these infants probably are at risk of future disease. Because life-threatening metabolic derangement can occur even in otherwise mild phenotypes, we advocate universal newborn screening programs for VLCAD deficiency to detect affected patients and prevent development of metabolic crises. Longer-term follow-up is essential to define outcomes, the definite risk of future disease, and appropriate treatment recommendations.

Betaine in the treatment of homocystinuria due to 5,10-methylenetetrahydrofolate reductase deficiency

In a 3-year-old mentally retarded girl with homocystinuria due to 5,10-methylenetetrahydrofolate reductase deficiency among different therapeutic approaches only treatment with betaine (15–20 g/day) resulted in a satisfactory biochemical response. Betaine improved homocysteine remethylation and thus lowered plasma homocystine to trace amounts and normalized the previously very low plasma methionine concentration. This biochemical response was associated with a clinical improvement although she remained mentally retarded.

Normal Clinical Outcome in Untreated Subjects with Mild Hyperphenylalaninemia

There is international consensus that patients with phenylalanine (Phe) levels <360 μM on a free diet do not need Phe-lowering dietary treatment whereas patients with levels >600 μM do. Clinical outcome of patients showing Phe levels between 360 and 600 μM in serum on a free nutrition has so far only been assessed in a small number of cases. Therefore, different recommendations exist for patients with mild hyperphenylalaninemia. We investigated in a nationwide study 31 adolescent and adult patients who persistently displayed serum Phe levels between 360 and 600 μM on a normal nutrition with a corresponding genotype. Because of limited accuracy of measurements, Phe levels should be looked on as an approximation, but not as an absolute limit in every instance. In addition to serum Phe levels, the assessment program consisted of comprehensive psychological testing, magnetic resonance imaging of the head, 1H magnetic resonance spectroscopy, and genotyping. We found a normal intellectual (intelligence quotient, 103 ± 15; range, 79–138) and educational (school performance and job career) outcome in these subjects as compared with healthy control subjects (intelligence quotient, 104 ± 11; range, 80–135). Magnetic resonance imaging revealed no changes of cerebral white matter in any patient, and 1H magnetic resonance spectroscopy revealed brain Phe levels below the limit of detection (<200 μM). In the absence of any demonstrable effect, dietary treatment is unlikely to be of value in patients with mild hyperphenylalaninemia and serum Phe levels <600 μM on a free nutrition, and should no longer be recommended. Because of a possible late-onset phenylketonuria, Phe levels of untreated patients should be monitored carefully at least during the first year of life. Nevertheless, problems of maternal phenylketonuria should still be taken into account.

Evaluation of quality of life and description of the sociodemographic state in adolescent and young adult patients with phenylketonuria (PKU)

BackgroundNormal intellectual and personal development can be expected in early-diagnosed and treated PKU patients. Aim of the study was to analyse quality of life and social status, which are important parameters for an overall estimation of success of treatment apart from intellectual outcome in adult PKU patients.Methods67 patients completed a questionnaire on quality of life and social status. Data was compared to the German census on an age matched control collective.ResultsQuality of life measured with the Profile of Quality of Life in the Chronically Ill (PLC) revealed mean values for capacity of performance in the patient group in the same range as in the control collective.The analysis of the social state of PKU patients revealed a tendency towards lower or delayed autonomy, and a low rate of forming normal adult relationships in which to have children. Schooling and professional career corresponded approximately to the control collective.ConclusionThough every chronic disorder must be regarded as restraining, it shows that PKU does not preclude healthy emotional adjustment when the disease is diagnosed early and treated well.

Safety and efficacy of 22 weeks of treatment with sapropterin dihydrochloride in patients with phenylketonuria

Phenylketonuria (PKU) is an inherited metabolic disease characterized by phenylalanine (Phe) accumulation, which can lead to neurocognitive and neuromotor impairment. Sapropterin dihydrochloride, an FDA‐approved synthetic formulation of tetrahydrobiopterin (6R‐BH4, herein referred to as sapropterin) is effective in reducing plasma Phe concentrations in patients with hyperphenylalaninemia due to tetrahydrobiopterin (BH4)‐responsive PKU, offering potential for improved metabolic control. Eighty patients, ≥8 years old, who had participated in a 6‐week, randomized, placebo‐controlled study of sapropterin, were enrolled in this 22‐week, multicenter, open‐label extension study comprising a 6‐week forced dose‐titration phase (5, 20, and 10 mg/kg/day of study drug consecutively for 2 weeks each), a 4‐week dose‐analysis phase (10 mg/kg/day), and a 12‐week fixed‐dose phase (patients received doses of 5, 10, or 20 mg/kg/day based on their plasma Phe concentrations during the dose titration). Dose‐dependent reductions in plasma Phe concentrations were observed in the forced dose‐titration phase. Mean (SD) plasma Phe concentration decreased from 844.0 (398.0) µmol/L (week 0) to 645.2 (393.4) µmol/L (week 10); the mean was maintained at this level during the studys final 12 weeks (652.2 [382.5] µmol/L at week 22). Sixty‐eight (85%) patients had at least one adverse event (AE). All AEs, except one, were mild or moderate in severity. Neither the severe AE nor any of the three serious AEs was considered related to sapropterin. No AE led to treatment discontinuation. Sapropterin is effective in reducing plasma Phe concentrations in a dose‐dependent manner and is well tolerated at doses of 5–20 mg/kg/day over 22 weeks in BH4‐responsive patients with PKU.

Prevalence of coeliac disease in diabetic children and adolescents. A multicentre study

Screening for coeliac disease (CD) with serum antigliadin antibodies (AGA) was performed in 1032 diabetic children and adolescents. In 8 children CD had been diagnosed before study entry. Of the remaining 1024 children, 33 had an elevated AGA titre in the first serum sample. On follow-up an elevated AGA titre was confirmed in only 17 of 31 patients. Nine of the repeatedly positive patients underwent jejunal biopsy, and CD was diagnosed in two asymptomatic patients; both were positive for IgG- and IgA-AGA. Among 10 AGA-positive patients in whom biopsies could not be performed, only 1 showed IgA-AGA and thus carried a high risk for CD. From our results we estimate a prevalence of CD in Swiss and German diabetic children between 1.1% and 1.3%. Falsepositive AGA titres occurred significantly more often in patients with diabetes duration of less than 1 year. AGA testing teached a specificity of 99% if performed at least 1 year after the onset of diabetes. Children suffering from both diabetes and CD showed a diabetes manifestation at a significantly younger age than non-coeliac patients, whereas CD tended to be diagnosed at a remarkably late age.

Correlations between branched-chain amino acids and branched-chain α-keto acids in blood in maple syrup urine disease

In 62 blood samples from 3 patients with classical maple syrup urine disease and from one patient with a variant form, a close linear correlation was found between levels of branched chain amino acids and their corresponding alpha-keto acids. Keto acids were determined as O-trimethylsilyl quinoxalinols by gas chromatography with a nitrogen-selective detector.

Development of height and weight in children with diabetes mellitus: report on two prospective multicentre studies, one cross-sectional, one longitudinal.

Optimal regimen for insulin therapy should lead to normal longitudinal growth and weight gain in children with diabetes mellitus. However, reports published so far indicate that this goal of paediatric diabetology is currently not achieved in a considerable number of patients. In a cross-sectional sample of 89 children with insulin dependent diabetes mellitus (IDDM) for more than 3 years, we found the relation of height to weight to be significantly different compared to 102 healthy school children of similar age. Using bivariate analysis, body shape in these children with diabetes was shifted towards small and obese (P<0.05) compared to control children. We subsequently initiated a longitudinal study and followed children from the onset of diabetes for the following 3 years, recording height, weight and bone age as well as glycosylated haemoglobin and daily insulin requirement. At diagnosis, height SDS was identical in children with IDDM (+0.04±0.10) compared to control children (−0.07±0.10; M±SE), while weight SDS was −0.26±0.10 in children with diabetes (controls: +0.01±0.1). Bone age was identically retarded in newly diagnosed IDDM children (−0.73±0.12 SDS) and in our control group of children from the same regional background (−0.50±0.12; n.s.). In this group of children with diabetes mellitus followed prospectively, height to weight relationship differed from controls after 2 and after 3 years of the disease (P<0.05). At 2 years, body size in children with diabetes was shifted towards taller and heavier compared to controls, while at 3 years, the relation of height to weight was even more abnormal with increased obesity but a reduction of standardized height. This is the same relation encountered in the cross-sectional sample of children with a duration of diabetes beyond 3 years. These data demonstrate that even modern insulin therapy does not guarantee normal development of height and weight in children with IDDM.