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Biomedical subjects

C Jakobs

Publications and source records attributed to C Jakobs.

At least 145 records · Page 8Linked to original sources
PubMed1998

Methylmalonic semialdehyde dehydrogenase deficiency: psychomotor delay and methylmalonic aciduria without metabolic decompensation.

A patient presenting with developmental delay but no episodes of metabolic acidosis was found to excrete significant amounts of methylmalonate (MMA) without any associated increased excretion of malonate, ethylmalonate, 3-hydroxypropionate, or beta-alanine. In contrast to patients with methylmalonic aciduria due to deficient mutase or impaired cobalamin metabolism, there was no increase of propionylcarnitine in blood or urine. The activity of methylmalonyl-CoA mutase and the pathway for cobalamin metabolism were also intact. The quantitative levels of the various labeled enantiomers of 3-hydroxyisobutyric (3-HIBA), 3-aminoisobutyric (3-AIBA), MMA, and propionylcarnitine were compared following separate intravenous infusions of equimolar doses of [2H8]-valine or [2H4]thymine in this patient and another with methylmalonyl-CoA mutase deficiency. Levels of labeled S- and R-3-HIBA and S- and R-3-AIBA indicated an isolated defect in methylmalonic semialdehyde dehydrogenase in this patient. This condition can be recognized by plasma MMA levels of approximately 8.5 microM (cf. 400 microM in mutase deficiency), urine MMA of 20-55 micromol/kg/24 h (cf. 1150 micromol/kg/24 h), no increase in propionylcarnitine following an oral carnitine load, and increased excretion of S-3-AIBA-nearly 10 times that observed in mutase deficiency. The ratio of R-AIBA to S-AIBA of <1 also reflects this disorder.

Aldehyde Oxidoreductases↗
PubMed1998

Abnormalities of vascular function in hyperhomocysteinaemia: relationship to atherothrombotic disease.

Hyperhomocysteinaemia is a risk factor for atherothrombotic disease, but data are limited on the arterial histology in humans with hyperhomocysteinaemia, either with or without other risk factors. Studies in vitro and in animals have shown that hyperhomocysteinaemia, possibly by increasing oxidant stress as well as by other mechanisms, may induce dysfunction of the vascular endothelium and proliferation of vascular smooth muscle cells, both key processes in atherogenesis. In clinically healthy subjects with hyperhomocysteinaemia, endothelium-dependent vasodilation may be impaired, but endothelial antithrombotic and profibrinolytic function appear normal at this stage. In patients with atherosclerosis and hyperhomocysteinaemia, endothelial antithrombotic properties appear more severely impaired than in similar patients with normohomocysteinaemia. Controlled data on the effects of homocysteine-lowering treatment on vascular function in humans are not available. The increased risk of atherothrombotic disease conferred by hyperhomocysteinaemia may be related to homocysteine-associated impairments in endothelial and vascular smooth muscle cell function. The precise mechanisms by which homocysteine affects vascular cell function, however, are unknown.

Animals↗
PubMed1998

Post- and prenatal diagnostic methods for the homocystinurias.

Diagnosis of the homozygous homocystinurias can be performed by investigations at the metabolite, enzyme and DNA level. The existence of variant forms due to the wide range of genetic variation may result in only small differences in various parameters between controls and affected subjects. 1. Sulphur amino acid concentrations in plasma, especially total homocysteine, are useful in first line diagnostic investigations. 2. Cystathionine-beta-synthase (CBS), methylenetetrahydrofolate reductase (MTHFR) and methylfolate homocysteine methyltransferase (MFMT) can be directly assayed in many tissues including fibroblasts (each) and blood cells (except CBS). Indirect whole cell assays which measure pathway activity dependent on a particular enzyme can provide useful diagnostic information. 3. Direct analysis of mutations is available for CBS, MTHFR and recently also for MFMT deficiencies. However the existence of a larger number of very rare, often private, mutations limits the usefulness of this approach in routine diagnosis. The above diagnostic approaches can generally be applied to prenatal diagnosis. Measurement of methylmalonic acid and other metabolites in amniotic fluid by stable isotope dilution / gas chromatography-mass spectrometry is well established for the methylmalonic acidurias. This method has also been applied to combined homocystinuria/methylmalonic aciduria supported by enzyme assays in cultured cells. Total homocysteine measurement in cell free amniotic fluid is also possible, performed so far in 14 cases with two affected fetuses. The indirect assay of methionine formation from [14C] labelled formate in intact cultured amniotic fluid cells has been for prenatal diagnosis of the remethylation defects.

5-Methyltetrahydrofolate-Homocysteine S-Methyltran↗
PubMed1998

Late-onset holocarboxylase synthetase-deficiency: pre- and post-natal diagnosis and evaluation of effectiveness of antenatal biotin therapy.

UNLABELLED: The clinical and biochemical findings in a family with late-onset holocarboxylase synthetase (HCS) deficiency are described. The index patient had two life-threatening episodes of metabolic decompensation at the age of 13 and 18 months with ketotic hypoglycaemia, vomiting and progressive loss of consciousness. The child recovered without biotin therapy. Organic aciduria characteristic of multiple carboxylase deficiency (MCD) was found, however, the key metabolites were only slightly elevated in some samples. Biotinidase deficiency was considered but excluded by the finding of normal plasma biotinidase activity. The correct diagnosis was made only at the age of 19 months when severe MCD was found in lymphocytes in the presence of normal plasma biotin concentration. HCS deficiency was confirmed by fibroblast studies. Biotin therapy (20 or 40 mg/day) prevented further episodes and normalized biochemical parameters with so far normal development. During two subsequent pregnancies, 10 mg biotin/day was administered to the mother from the 20th week of gestation. At delivery plasma biotin in cord blood samples was 3 4 times higher than in maternal plasma. The 2nd child was unaffected. In the 3rd pregnancy prenatal diagnosis was performed at 16 weeks of gestation. The concentration of methylcitrate in amniotic fluid was within the normal range and that of 3-hydroxyisovalerate only slightly elevated. However, enzyme assays in cultured amniotic fluid cells were consistent with an affected fetus. At birth, carboxylase activities in lymphocytes of this newborn were only moderately decreased to 37% of mean normal. HCS deficiency was confirmed postnatally in fibroblasts. Development remains normal on biotin therapy (20 mg/day). CONCLUSION: Prenatal diagnosis in families with milder forms of HCS deficiency has to be performed by enzyme assays in cultured amniotic cells since organic acid analysis of amniotic fluid may be inconclusive in affected fetuses. Biotin administered prenatally is effectively taken up by the fetus and prevents functional deficiency of the carboxylases in an affected newborn.

Biotin↗
PubMed1998

Effects of folic acid and vitamin B6 supplementation on women with hyperhomocysteinemia and a history of preeclampsia or fetal growth restriction.

OBJECTIVE: Our purpose was to assess the incidence of hyperhomocysteinemia in patients with a history of preeclampsia or fetal growth restriction, to evaluate the effects of vitamin supplementation on the methionine loading test, and to study the course of subsequent pregnancies in women with hyperhomocysteinemia and a history of preeclampsia or fetal growth restriction. STUDY DESIGN: A total of 207 consecutive patients with a history of preeclampsia or fetal growth restriction was tested for hyperhomocysteinemia. Thirty-seven were found to be positive and were treated with folic acid and vitamin B6, and 27 had a second methionine loading test after vitamin supplementation. Fourteen patients became pregnant again while receiving vitamins and aspirin. RESULTS: All patients who underwent a methionine loading test after vitamin supplementation had a completely normalized methionine loading test. Of the 14 pregnancies in women receiving vitamins and aspirin, 7 were complicated by preeclampsia. Birth weights were 2867 +/- 648 g compared with 1088 +/- 570 g in the previous pregnancies. CONCLUSIONS: Vitamin B6 and folic acid correct the methionine loading test in patients with hyperhomocysteinemia. Perinatal outcome in patients with a history of preeclampsia or fetal growth restriction and hyperhomocysteinemia appears to be favorable.

Dietary Supplements↗
PubMed1998

Postmenopausal oral 17beta-estradiol continuously combined with dydrogesterone reduces fasting serum homocysteine levels.

OBJECTIVE: To investigate the effects of oral 17beta-estradiol administration continuously combined with dydrogesterone on fasting serum total homocysteine levels in postmenopausal women. DESIGN: Randomized, double-blind study. SETTING: Gynecologic outpatient department of a university hospital. PATIENT(S): One hundred thirty-five healthy, nonhysterectomized postmenopausal women. INTERVENTION(S): Oral micronized 17beta-estradiol (2 mg/d) continuously combined with one of four dosages of dydrogesterone (2.5 mg [n = 41], 5 mg [n = 38], 10 mg [n = 37], or 15 mg [n = 19]) was given for 6 months. MAIN OUTCOME MEASURE(S): Fasting serum total homocysteine concentrations. RESULT(S): The mean fasting serum total homocysteine concentrations in the overall study population decreased significantly (by 13.5%) after the first 3 months of treatment and remained unchanged thereafter. No influence of dydrogesterone dosage was found. The greatest reduction in total homocysteine concentration was obtained in women with the highest baseline levels. CONCLUSION(S): Continuously combined hormone replacement therapy lowers fasting serum total homocysteine levels significantly in postmenopausal women. This decrease may be one of the mechanisms that underlie the cardioprotective effects of postmenopausal hormone replacement therapy.

Administration, Oral↗
PubMed1998

Randomized, double-blind, placebo-controlled study of the effects of raloxifene and conjugated equine estrogen on plasma homocysteine levels in healthy postmenopausal women.

OBJECTIVE: To investigate the long-term effects of raloxifene on fasting plasma homocysteine levels in postmenopausal women compared with conjugated equine estrogen (CEE). DESIGN: Randomized, double-blind, placebo-controlled study. SETTING: Outpatient department of a university hospital. PATIENT(S): Fifty-two hysterectomized, healthy postmenopausal women. INTERVENTION(S): Oral raloxifene in two dosages (60 mg/d [n=13] and 150 mg/d [n=13]), oral CEE (0.625 mg/d [n=13], and placebo (n=13) were given for 24 months. MAIN OUTCOME MEASURE(S): Fasting plasma homocysteine concentrations. RESULT(S): Plasma homocysteine levels were not altered in the placebo group. After 12 months, a significant reduction versus baseline in the mean plasma homocysteine level (-16%) was found only in the raloxifene 150-mg group. The mean change in plasma homocysteine levels within this group also was significantly different from the changes versus baseline found in the placebo group (+2%) and the raloxifene 60-mg group (-2%), but not different from those found in the CEE group (-8%). After 24 months, plasma homocysteine levels were decreased significantly in the raloxifene 150-mg and CEE groups compared with both baseline (-13% and -10%, respectively) and placebo values (-15% and -11%, respectively). No significant change in plasma homocysteine levels was observed in the raloxifene 60-mg group. CONCLUSION(S): Raloxifene has a favorable, dose-related effect on plasma homocysteine levels in postmenopausal women.

Administration, Oral↗
PubMed1998

A randomized controlled study of the effects of 17beta-estradiol-dydrogesterone on plasma homocysteine in postmenopausal women.

OBJECTIVE: To investigate the effects of oral 17beta-estradiol (E2) -dydrogesterone on fasting plasma homocysteine concentrations in healthy postmenopausal women. METHODS: We studied 27 postmenopausal women who were assigned randomly to either a treatment group (n = 14) or a control group (n = 13). During the first 12 months of the study, treatment consisted of oral E2, 1 mg daily, combined sequentially with dydrogesterone 5 or 10 mg (14 days per 28-day treatment cycle). Thereafter, women were treated with oral E2, 2 mg daily, combined sequentially with dydrogesterone, 10 mg daily (14 days per 28-day treatment cycle) for a period of 3 months. The control group received no treatment. Fasting plasma total homocysteine concentrations were determined at baseline and 3, 12, and 15 months after study entry. RESULTS: At baseline, plasma homocysteine levels did not differ between the groups. After 15 months of hormone treatment mean plasma homocysteine concentration was lowered by 12.6% compared with baseline (P < .001; analysis of variance for repeated measures). Plasma homocysteine levels were not altered in the control group. The interaction between treatment and time for homocysteine levels was significantly different between the groups (P < .001; analysis of variance for repeated measures). The decrease in plasma homocysteine levels correlated inversely with the increase in serum E2 levels after 3 and 12 months of hormone treatment (r = -.54, P < .05 and r = -.56, P < .05, respectively). CONCLUSION: Plasma fasting homocysteine concentrations are lowered by E2-dydrogesterone therapy in postmenopausal women.

Dydrogesterone↗
PubMed1998

The effect of renal transplantation on hyperhomocysteinaemia in dialysis patients, and the estimation of renal homocysteine extraction in patients with normal renal function.

BACKGROUND: The pathophysiology of hyperhomocysteinaemia in chronic renal failure (CRF) is unknown. Possible mechanisms are decreased renal homocysteine (Hcy) catabolism or inhibition of extrarenal Hcy metabolism by uraemic toxins. METHODS: We studied the short-term effect on plasma Hcy concentration of improvement of renal function after successful kidney transplantation (n = 8), and determined renal Hcy extraction by measurement of total Hcy in arterial and renal venous blood in 7 cardiac patients with normal renal function. RESULTS: Post-transplantation, plasma Hcy decreased with improving renal function. In the cardiac patients, no significant renal Hcy extraction could be demonstrated, but tubular disposal of the filtered load could not be excluded. CONCLUSIONS: Because loss of such renal metabolism could lead to hyperhomocysteinaemia in CRF, it is necessary to determine the renal extraction of free Hcy in subjects with normal renal function to further investigate renal homocysteine metabolism.

Adult↗
PubMed1998

An accurate stable isotope dilution gas chromatographic-mass spectrometric approach to the diagnosis of guanidinoacetate methyltransferase deficiency.

A gas chromatography-mass spectrometry (GC-MS) method is described for the quantification of guanidinoacetate in different body fluids, using a two step derivatisation procedure which involves a reaction with hexafluoroacetylacetone to form a bis(trifluoromethyl)pyrimidine ring structure followed by a reaction with pentafluorobenzyl bromide. 13C2-labelled guanidinoacetate is used as an internal standard. Bis(trifluoromethyl)pyrimidine pentafluorobenzyl derivatives were separated on a polar capillary GC-column and were quantified using negative chemical ionisation mass fragmentography. The detection limit of the method is 1 pmol guanidinoacetate in a 100 microl sample. Control values were obtained for urine (53.9 +/- 25.9 mmol mol(-1) creatinine), plasma (1.08 +/- 0.31 micromol l(-1)), cerebrospinal fluid (CSF) (0.114 +/- 0.068 micromol l(-1)) and amniotic fluid (3.44 +/- 0.64 micromol l(-1)). The applicability of the method is illustrated by the determination of guanidinoacetate in urine, plasma and CSF of a patient affected with guanidinoacetate methyltransferase deficiency. In all body fluids of this patient, guanidinoacetate was highly elevated.

Amino Acid Metabolism, Inborn Errors↗
PubMed1998

The effect of fasting, long-chain triglyceride load and carnitine load on plasma long-chain acylcarnitine levels in mitochondrial very long-chain acyl-CoA dehydrogenase deficiency.

We studied a 10-year-old patient with very long-chain acyl-CoA dehydrogenase (VLCAD) deficiency who was originally (mis)diagnosed as having systemic carnitine deficiency. He was subjected to a fasting test, a long-chain triglyceride (LCT) loading test (1.5 g/kg) and an intravenous carnitine clearance test (0.25 mumol/kg per min). Plasma acylcarnitines were analysed using a quantitative GC-CI-MS method. During fasting, all long-chain acylcarnitines with a chain length of C14 and higher (especially C14:1) increased dramatically. Total plasma long-chain acylcarnitine reached a concentration of 28.6 mumol/L. LCT loading resulted in a moderate increase, mainly of the C18 esters. The carnitine infusion, which led to a supranormal plasma free carnitine concentration, gave only a slight but generalized rise of long-chain acylcarnitines. Although only one patient could be tested, the results suggest that the accumulation of potentially toxic long-chain acylcarnitines in VLCAD deficiency is provoked by fasting, LCT loading and carnitine supplementation. Therapy should be adjusted accordingly.

Acyl-CoA Dehydrogenase↗
PubMed1998

Studies on the oxidation of phytanic acid and pristanic acid in human fibroblasts by acylcarnitine analysis.

The alpha-oxidation of phytanic acid and the beta-oxidation of pristanitc acid were investigated in cultured fibroblasts from controls and patients affected with different peroxisomal disorders using deuterated substrates. Formation of [omega-2H6]4,8-dimethylnonanoylcarnitine ([omega-2H6]C11-carnitine) from [omega-2H6]phytanic acid and [omega-2H6]pristanic acid was used as marker for these processes. Analysis was performed by tandem mass spectrometry. In normal cells, formation of [omega-2H6]C11-carnitine from both [omega-2H6]phytanic acid and [omega-2H6]pristanic acid was observed. When peroxisome-deficient fibroblasts were incubated with these substrates, [omega-2H6]C11-carnitine was not detectable or, in two cases, very low, which results from deficiencies in both peroxisomal alpha- and beta-oxidation. In cells with an isolated beta-oxidation defect at the level of the peroxisomal bifunctional protein, formation of [omega-2H6]C11-carnitine could also not be detected. Cells with an isolated defect in the alpha-oxidation of phytanic acid, obtained from patients affected with Refsum disease (McKusick 266500) or rhizomelic chondrodysplasia punctata (McKusick 215100), did not form [omega-2H6]C11-carnitine from [omega-2H6]phytanic acid. The observed formation of [omega-2H6]C11-carnitine from [omega-2H6]pristanic acid in these cells is in accordance with a normal peroxisomal beta-oxidation in these disorders. This study shows that separate incubation of fibroblasts with [omega-2H6]phytanic acid and [omega-2H6]pristanic acid, followed by acylcarnitine analysis in the medium by tandem mass spectrometry, can be used for screening cell lines for deficiencies in the peroxisomal alpha- and beta-oxidation pathways. Phytanic acid (3,7,11,15-tetramethylhexadecanoic acid) and pristanic acid (2,6,10,14-tetramethylpentadecanoic acid) are branched-chain fatty acids that are constituents of the human diet. As phytanic acid possesses a beta-methyl group, it cannot be degraded by beta-oxidation. Instead, phytanic acid is first degraded by alpha-oxidation, yielding pristanic acid, which is subsequently degraded by beta-oxidation (Figure 1). Phytanic acid alpha-oxidation is thought to occur partly, and pristanic acid beta-oxidation exclusively, in peroxisomes (see Wanders et al 1995 for review). Accumulation of phytanic acid and pristanic acid is found in blood and tissues of patients affected with generalized peroxisomal disorders. In this type of disorder, no morphologically distinguishable peroxisomes are present in tissues, resulting in accumulation of metabolites that are normally metabolized in these organelles (see Wanders et al 1995 for review). The group of generalized peroxisomal disorders consists of three diseases, differing in clinical presentation. Patients suffering from the most severe disease, Zellweger syndrome (McKusick 214100), have symptoms from birth on and usually do not live beyond their first year of life. Neonatal adrenoleukodystrophy (N-ALD, McKusick 202370) has a milder presentation, whereas infantile Refsum disease (IRD, McKusick 266510) is the mildest form among the generalized peroxisomal disorders. Not only in these generalized peroxisomal disorders, but also in some isolated peroxisomal beta-oxidation defects, elevated levels of phytanic acid and pristanic acid are found (ten Brink et al 1992a). The elevated phytanic acid levels are considered to be caused by product inhibition of alpha-oxidation by accumulating pristanic acid. This is reflected in a highly elevated pristanic acid to phytanic acid ratio in plasma from patients suffering from bifunctional protein deficiency or peroxisomal thiolase deficiency (ten Brink et al 1992a). Elevated phytanic acid concentrations are also found in plasma from patients affected with classical Refsum disease and rhizomelic chondrodysplasia punctata (RCDP). As pristanic acid beta-oxidation is not disturbed in these disorders, pristanic acid levels are normal (ten Brink et al 1992

Carnitine↗