-
[show abstract]
[hide abstract]
ABSTRACT: A variety of genetic variations in the galactose-1-phosphate uridyltransferase (GALT) gene cause profound activity loss of the enzyme and acute toxic effects mediated by accumulating metabolic intermediates of galactose in newborns induced by dietary galactose. However, even on a severely galactose-restricted diet, patients develop serious long-term complications of the CNS and ovaries, which may result from damaging perturbations in cell biology caused by endogenously synthezised galactose. Under galactose stress, the cosubstrate of GALT, galactose-1-phosphate, accumulates and disturbs catabolic and anabolic pathways of the carbohydrate metabolism with potential effects on protein glycosylation and membrane localization of glycoprotein receptors, like the epidermal growth factor receptor. To address this issue in view of a cellular pathomechanism, we performed a differential semiquantitative N-glycomics study of membrane proteins. A suitable noninvasive cellular material derived from epithelial plasma membranes was found in urinary exovesicles and in the shed Tamm-Horsfall protein. By applying matrix-assisted laser ionization mass spectrometry on permethylated, PNGaseF released N-glycans, we demonstrate that GALT deficiency is associated with dramatic shifts from prevalent high-mannose-type glycans found in healthy subjects toward complex-type N-linked glycosylation in patients. These N-glycosylation shifts were observed on exosomal N-glycoproteins but not on the Tamm-Horsfall glycoprotein, which showed predominant high-mannose-type glycosylation with M6.
Journal of Proteome Research 11/2011; 11(2):906-16. · 5.11 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: To conduct a longitudinal assessment of long-term cognitive outcome in patients with classical galactosemia.
Inclusion criteria were (1) previous assessment of IQ dating back >10 years with tests being comparable with the recent German tests HAWIK-III and HAWIE-R, (2) absence of illnesses other than galactosemia, (3) absence of foreign language problems, (4) enzymatic-metabolic proof of classical galactosemia, (5) compliance with dietary therapy, and (6) written informed consent. Twenty-three patients who fulfilled these criteria were found. They underwent the first IQ test at a mean age of 11 +/- 5 years and the second 13.6 to 15.5 years later at a mean age of 26 +/- 5 years. Results were corrected for the obsolescence of test norms (Flynn effect).
Mean total IQ scores on the first and second tests were 78 +/- 14 and 73 +/- 15, respectively, and not significantly different. IQ scores in the average range were observed for 7 patients on the first test and for 5 patients on the second test. For 17 patients, the intraindividual IQ scores remained essentially unchanged. Five patients showed a decrease and 1 an increase of the IQ score over time. No consistent pattern of change was found with respect to performance or verbal IQ subscores or in achievements in the individual subtest.
The results confirm the presence of reduced cognitive ability in classical galactosemia and present evidence for an absence of substantial galactosemia-induced aggravation of this impairment with increasing age, at least in patients from 4 to 40 years of age. It remains to be clarified whether a reduction of cognitive function in galactosemia may be initiated by an in utero toxicity of endogenously formed galactose and which role such a process may play in the development of intellectual deficiencies that are later maintained throughout life.
PEDIATRICS 02/2010; 125(2):e374-81. · 4.47 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: Two new inborn errors in the pentose phosphate pathway have been described: ribose-5-isomerase deficiency and transaldolase deficiency. These defects are characterized by accumulation of specific polyols in body fluids. Little is known about human polyol metabolism, but there are indications for a physiological role primarily during early development.
The objective of this study was to evaluate the urinary excretion of polyols in neonates with special interest on a possible impact of the grade of maturity. For comparison, urinary polyol excretion in older children was also studied.
Urine samples of 40 neonates born between gestational week 25 and 41 were analyzed for the excretion of pentose phosphate pathway-associated polyols (erythritol, D-arabitol, ribitol, xylitol). These metabolites were also quantified in urine obtained from 77 children aged 4 weeks to 10 years.
The results show high urinary polyol excretions after birth independent of the week of gestation. During the first months of life, the concentrations decreased exponentially and reached a fairly stable steady state thereafter.
Urinary excretion of polyols shows an age dependency with highest concentrations postnatally independent of the grade of maturity. These findings suggest a possible connection between the formation of pentose phosphate pathway-associated polyols and fetal development.
Neonatology 12/2008; 95(3):256-61. · 2.66 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: Pregnancy, delivery, and postpartal metabolic control was monitored biochemically in five patients (22-38 years of age) with clinically, enzymatically, and genotypically established classical galactosaemia and good dietary compliance. Three of the patients performed breast feeding of their newborns. Monitoring parameters were galactose-1-phosphate and galactitol concentrations in erythrocytes and urinary excretion of galactose, galactitol, galactonate, and lactose. During pregnancy, a small but steady increase of renal metabolite excretion rates was observed. After delivery, a moderate transient increase of metabolite concentrations with peak values within the first week post partum occurred, irrespective of breast feeding. Altogether, there was no evidence for clinically or subclinically significant changes of metabolic control during pregnancy, delivery, or lactation. In conclusion, a specific metabolic monitoring is apparently not required in pregnant galactosemic women, and breast feeding of the nongalactosemic offspring can be recommended.
European Journal of Pediatrics 10/2008; 168(6):721-9. · 1.88 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: Newborn infants are exposed to various sources of oxidative and/or nitrative stress, which refers to either oxidation and/or nitration of endogenous proteins including loss of their original function. Nitrative stress is predominantly caused following synthesis of peroxynitrite. Particularly preterm infants with immature defense mechanisms against free radical injury appear at risk.
To test the feasibility of quantifying the degradation products of the peroxynitrite marker nitrotyrosine [3-nitro-4-hydroxyphenylacetic acid (NHPA) and para-hydroxyphenylacetic acid (PHPA)] in neonatal urine samples.
NHPA and PHPA were determined by gas chromatography/mass spectroscopy in urinary samples of preterm and term infants (mean gestational age = 28.4 and 39.6 weeks, respectively).
The urinary NHPA levels were lower in preterm infants in comparison with term infants. When the NHPA levels were adjusted to the urinary PHPA levels, no differences were found between the two groups.
Nitrotyrosine can be quantified in urinary samples of even the most immature infants. Nitration of endogenous PHPA in the gastrointestinal tract of term infants may have masked potentially higher levels of NHPA in preterm infants.
Neonatology 02/2008; 93(2):73-6. · 2.66 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: Maple syrup urine disease (MSUD) is an inherited deficiency of branched chain alpha-ketoacid dehydrogenase (BCKDH) activity impairing the degradation of the branched chain amino acids valine, leucine, and isoleucine. Classic MSUD may lead to severe neonatal encephalopathy including coma and impaired cognitive outcome in later life. Early start of dietary treatment and careful metabolic control may improve the outcome of patients with classic MSUD. The aim of this study was to investigate the impact of long-term metabolic control assessed by plasma leucine levels on cognitive outcome in patients with classic MSUD. Plasma leucine levels of 24 patients were obtained retrospectively for the first 6 y of life and yearly medians of mean plasma leucine levels were calculated. At the age of 6 y, IQ tests were performed. Yearly medians of mean plasma leucine levels yielded three homogeneous clusters (low, intermediate, high). Patients of the low cluster showed statistically significant higher IQ scores compared with those of those of intermediate and high clusters. Long-term plasma leucine levels are associated with impaired cognitive outcome in patients with classic MSUD. To achieve the best possible intellectual outcome for affected individuals, we recommend that in infants and preschool children the target range for plasma leucine should not exceed 200 micromol/L.
Pediatric Research 02/2006; 59(1):17-20. · 2.70 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: A stable isotope dilution assay was developed for the sensitive determination of D-galactonic acid. D-[U-13C(6)]galactono-1,4-lactone was prepared as internal standard. Unlabelled and U-13C-labelled D-galactonic acid species were converted to the N-(1-butyl)galactonamide pentaacetate derivatives and assessed by gas chromatography-mass spectrometry (GC-MS). Positive chemical ionisation and monitoring of the [MH-60](+)-ions in the galactonate chromatographic peak at m/z 402 and m/z 408 were used for quantification. The procedure was applied to study the variability of D-galactonate excretion in healthy subjects and galactosemic patients and to monitor the D-galactonate-D-galactitol ratio in human urine.
Journal of Chromatography B 04/2004; 801(2):249-55. · 2.89 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: The age dependence of endogenous galactose formation was investigated in Q188R homozygous galactosemic patients (n=18; 4-38 years) using the primed continuous infusion approach with D-[1-13C]galactose as a substrate. Studies were conducted under postabsorptive conditions (fasting >10h) and good metabolic control. In the patients, the release of galactose from endogenous sources into plasma (R(a)) decreased with age and ranged from 4.6 to 2.0 micromol/kg body weight per h. Galactitol and galactonate release rates paralleled the galactose R(a) but at a lower level. The mean relation of galactose, galactitol, and galactonate release was 10:5:1. Statistically, there was a highly significant (p<0.0001) inverse correlation between total galactose release (i.e., sum of R(a) plus galactitol and galactonate release) and age. The data (total galactose=y, age=t) were best fitted to the simple exponential model y=y(0)+axexp(-bt) by non-linear regression analysis. The parameter estimates were y(0)=3.0+/-0.2, a=6.5+/-0.4, and b=0.11+/-0.02. The value of y(0) provides an estimate of total galactose release in adult patients (i.e., approximately 13 mg/kg body weight per day), summation operator (y(0)+a) provides an estimate for galactosemic newborns (i.e., approximately 41 mg/kg body weight per day). The data show that significant amounts of endogenous galactose are formed in galactosemic patients with release rates being several fold higher in infants than in adults. The present findings can explain the persistently elevated galactose-1-phosphate levels in erythrocytes-and its age dependence-in galactosemic patients even when under strict dietary treatment.
Molecular Genetics and Metabolism 01/2004; 81(1):31-44. · 3.19 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: Maple syrup urine disease (MSUD) is an autosomal recessive metabolic disorder of panethnic distribution caused by a deficiency of the activity of branched-chain alpha-ketoacid dehydrogenase (BCKD) complex. Mutations in the human BCKD genes E1alpha (BCKDHA), E1beta (BCKDHB) and E2 (DBT) are known to result in MSUD, referred to as type Ia, Ib and II mutations respectively. In this study 16 patients with the classic severe form of MSUD and three patients with milder variant forms of the disease were investigated for mutations in the E1alpha-, E1beta- and E2-gene by single-strand conformation polymorphism (SSCP) analysis and DNA sequencing. The patients' clinical and biochemical phenotypes were well characterized. One novel type Ia missense mutation, eight novel type Ib (three missense, two nonsense, two small deletions, one small duplication) and three novel type II (two missense, one splice site) mutations were identified in patients. Moreover, eleven previously described mutations were detected: five type Ia (four missense, one nonsense), three type Ib mutations (two missense, one nonsense) and three type II mutations (two missense, one small deletion). Fourteen patients are homozygous for one single mutation, five patients are compound-heterozygous for two different mutations affecting one of the three genes. Thus, in all 19 patients the identified mutations can most probably be considered the molecular basis of the disease.
Human Mutation 12/2003; 22(5):417. · 5.69 Impact Factor
-
The Lancet 09/2003; 362(9382):446. · 38.28 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: An established gas chromatography/mass spectrometry (GC/MS) method, devised for stable-isotope dilution analysis of plasma galactose, was developed to allow determination of erythrocyte (red blood cell, RBC) concentrations of galactose-1-phosphate and other primary metabolites relevant in galactosaemia. Galactose-1-phosphate was enzymatically converted to galactose, and the aldononitrile pentaacetate derivative was separated by gas chromatography and determined by mass spectrometry using chemical ionisation and selected ion monitoring of the [MH-60](+) ion. U-(13)C-Labelled standard was used for quantification. Comparative measurements were conducted using established fluorimetric and radiometric enzymatic methods. The GC/MS analysis for galactose-1-phosphate was linear (range examined 0-600 micromol/L(RBC), packed cells), of acceptable repeatability at low and high concentrations (within and between run CVs <15%), with a limit of quantification of 0.01 micromol/L(RBC). With samples from patients with classical galactosaemia there was a linear correlation with conventional enzymatic assays (r(2) > 0.927). In erythrocytes from post-absorptive patients under treatment, Q188R-heterozygous parents, and healthy subjects, galactose-1-phosphate concentrations (mean +/- SD) were found to be 142 +/- 38 (n = 41), 1.4 +/- 0.2 (n = 8), and 1.9 +/- 0.5 (n = 33) micromol/L(RBC), respectively. In comparison, free galactose concentrations were 3.8 +/- 1.7, 0.49 +/- 0.19, and 0.43 +/- 0.20 mol/L(RBC), respectively. The procedure allowed simultaneous galactitol analysis and proved to be useful to trace incorporation of (13)C-label into erythrocyte galactose metabolites in a D-[1-(13)C]galactose in vivo turnover study.
Rapid Communications in Mass Spectrometry 02/2003; 17(24):2833-8. · 2.79 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: Maple syrup urine disease (MSUD) is a rare autosomal recessive disorder that causes acute and chronic brain dysfunction because of a neurotoxic effect of the accumulating branched chain amino acids (BCAA) and their corresponding keto acids. Aim of the treatment is a rapid reversal of the neonatal decompensation and a stable long-term metabolic control obtained by a carefully adjusted BCAA-low diet. In optimally treated patients, an unimpaired neurological and intellectual outcome is possible. Ten patients of Turkish origin suffering from MSUD are presently treated in the Metabolic Unit of the University Hospital in Düsseldorf, Germany. All patients show mild intellectual deficits; neurological impairment is rare. This paper aims to define the feasible standard of therapy and the resulting intellectual and psychosocial outcome achievable in MSUD patients of Turkish origin under high standard conditions of medical care for inborn errors of metabolism.
The Turkish journal of pediatrics 47(1):8-13. · 0.44 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: A simple closed system for the serial determination of 14CO2 in small volumes of fluid samples, is described. The device consists of commercially available scintillation vials and silicone tube seals. 14CO2 is selectively liberated by citric acid and absorbed in a scintillation vial by Hyamine. Experiments on the effect of dichloroacetate on pyruvate dehydrogenase activity in rat hindlimbs perfused with [1-14C]pyruvate demonstrate the applicability of the method.
Analytical Biochemistry 132(2):400-404. · 3.00 Impact Factor
