Cornelis Jakobs

Underlying disorders associated with severe early-onset preeclampsia

OBJECTIVE Our purpose was to determine whether patients with severe early-onset preeclampsia have hemostatic or metabolic abnormalities that are associated with a tendency to vascular thrombosis. STUDY DESIGN A total of 101 patients with a history of severe early-onset preeclampsia were tested at least 10 weeks post partum for the presence of hyperhomocysteinemia (methionine loading test), protein C, protein S, and antithrombin III deficiency, activated protein C resistance, lupus anticoagulant, and immunoglobulin G and/or M anticardiolipin antibodies. RESULTS Of the 101 patients, 39 (38.6%) had chronic hypertension. Of the 85 patients tested for coagulation disturbances, 21 (24.7%) had protein S deficiency. Of the 50 patients tested for activated protein C resistance, 8 (16.0%) were positive. Of the 79 patients tested for hyperhomocysteinemia, 14 (17.7%) had a positive methionine loading test. Finally, 95 patients were tested for anticardiolipin antibodies; 27 (29.4%) had detectable immunoglobulin G and/or M anticardiolipin antibodies. CONCLUSION Patients with a history of severe early-onset preeclampsia should be screened for protein S deficiency, activated protein C resistance, hyperhomocysteinemia, and anticardiolipin antibodies, since these results may have an impact on counseling for and pharmacologic management in future pregnancies.

Mutations in antiquitin in individuals with pyridoxine-dependent seizures

We show here that children with pyridoxine-dependent seizures (PDS) have mutations in the ALDH7A1 gene, which encodes antiquitin; these mutations abolish the activity of antiquitin as a Δ1-piperideine-6-carboxylate (P6C)–α-aminoadipic semialdehyde (α-AASA) dehydrogenase. The accumulating P6C inactivates pyridoxal 5′-phosphate (PLP) by forming a Knoevenagel condensation product. Measurement of urinary α-AASA provides a simple way of confirming the diagnosis of PDS and ALDH7A1 gene analysis provides a means for prenatal diagnosis.

Dynamic rerouting of the carbohydrate flux is key to counteracting oxidative stress

Background Eukaryotic cells have evolved various response mechanisms to counteract the deleterious consequences of oxidative stress. Among these processes, metabolic alterations seem to play an important role. Results We recently discovered that yeast cells with reduced activity of the key glycolytic enzyme triosephosphate isomerase exhibit an increased resistance to the thiol-oxidizing reagent diamide. Here we show that this phenotype is conserved in Caenorhabditis elegans and that the underlying mechanism is based on a redirection of the metabolic flux from glycolysis to the pentose phosphate pathway, altering the redox equilibrium of the cytoplasmic NADP(H) pool. Remarkably, another key glycolytic enzyme, glyceraldehyde-3-phosphate dehydrogenase (GAPDH), is known to be inactivated in response to various oxidant treatments, and we show that this provokes a similar redirection of the metabolic flux. Conclusion The naturally occurring inactivation of GAPDH functions as a metabolic switch for rerouting the carbohydrate flux to counteract oxidative stress. As a consequence, altering the homoeostasis of cytoplasmic metabolites is a fundamental mechanism for balancing the redox state of eukaryotic cells under stress conditions.

Increased, homocysteine and S-adenosylhomocysteine concentrations and DNA hypomethylation in vascular disease

BACKGROUND The pathogenic mechanism of homocysteines effect on cardiovascular risk is poorly understood. Recent studies show that DNA hypomethylation induced by increases in S-adenosylhomocysteine (AdoHcy), an intermediate of Hcy metabolism and a potent inhibitor of methyltransferases, may be involved in homocysteine-related pathology. METHODS We measured fasting plasma total Hcy (tHcy), AdoHcy, and S-adenosylmethionine (AdoMet) and methylation in leukocytes in 17 patients with vascular disease and in 15 healthy, age- and sex-matched controls. RESULTS Patient with vascular disease had significantly higher plasma tHcy and AdoHcy concentrations and significantly lower plasma AdoMet/AdoHcy ratios and genomic DNA methylation. AdoMet concentrations were not significantly different between the two groups. More than 50% of the patients fell into the highest quartiles of plasma tHcy, AdoHcy, and [(3)H]dCTP incorporation/ micro g of DNA (meaning the lowest quartile of DNA methylation status) and into the lowest quartile of the AdoMet/AdoHcy ratios of the control group. Plasma tHcy was significantly correlated with plasma AdoHcy and AdoMet/AdoHcy ratios (n = 32; P < 0.001). DNA methylation status was significantly correlated with plasma tHcy and AdoHcy (n = 32; P < 0.01) but not with plasma AdoMet/AdoHcy ratios. CONCLUSION Global DNA methylation may be altered in vascular disease, with a concomitant increase in plasma tHcy and AdoHcy.

Hyperhomocysteinemia Is Associated With an Increased Risk of Cardiovascular Disease, Especially in Non–Insulin-Dependent Diabetes Mellitus A Population-Based Study

A high serum total homocysteine (tHcy) level is an independent risk factor for cardiovascular disease. Because it is not known whether the strength of the association between hyperhomocysteinemia and cardiovascular disease is similar for peripheral arterial, coronary artery, and cerebrovascular disease, we compared the three separate risk estimates in an age-, sex-, and glucose tolerance-stratified random sample (n=631) from a 50- to 75-year-old general white population. Furthermore, we investigated the combined effect of hyperhomocysteinemia and diabetes mellitus with regard to cardiovascular disease. The prevalence of fasting hyperhomocysteinemia (>14.0 micromol/L) was 25.8%. After adjustment for age, sex, hypertension, hypercholesterolemia, diabetes, and smoking, the odds ratios (ORs; 95% confidence intervals) per 5-micromol/L increment in tHcy were 1.44 (1.10 to 1.87) for peripheral arterial, 1.25 (1.03 to 1.51) for coronary artery, 1.24 (0.97 to 1.58) for cerebrovascular, and 1.39 (1.15 to 1.68) for any cardiovascular disease. After stratification by glucose tolerance category and adjustment for the classic risk factors and serum creatinine, the ORs per 5-micromol/L increment in tHcy for any cardiovascular disease were 1.38 (1.03 to 1.85) in normal glucose tolerance, 1.55 (1.01 to 2.38) in impaired glucose tolerance, and 2.33 (1.11 to 4.90) in non-insulin-dependent diabetes mellitus (P=.07 for interaction). We conclude that the magnitude of the association between hyperhomocysteinemia and cardiovascular disease is similar for peripheral arterial, coronary artery, and cerebrovascular disease in a 50- to 75-year-old general population. High serum tHcy may be a stronger (1.6-fold) risk factor for cardiovascular disease in subjects with non-insulin-dependent diabetes mellitus than in nondiabetic subjects.

Hyperhomocysteinemia Increases Risk of Death, Especially in Type 2 Diabetes 5-Year Follow-Up of the Hoorn Study

BACKGROUND A high serum total homocysteine (tHcy) concentration is a risk factor for death, but the strength of the relation in patients with type 2 (non-insulin-dependent) diabetes mellitus compared with nondiabetic subjects is not known. A cross-sectional study suggested that the association between tHcy and cardiovascular disease is stronger in diabetic than in nondiabetic subjects. We therefore prospectively investigated the combined effect of hyperhomocysteinemia and type 2 diabetes on mortality. METHODS AND RESULTS Between October 1, 1989, and December 31, 1991, serum was saved from 2484 men and women, 50 to 75 years of age, who were randomly selected from the town of Hoorn, The Netherlands. Fasting serum tHcy concentration was measured in 171 subjects who died (cases; 76 of cardiovascular disease) and in a stratified random sample of 640 survivors (control subjects). Mortality risks were calculated over 5 years of follow-up by means of logistic regression. The prevalence of hyperhomocysteinemia (tHcy >14 micromol/L) was 25. 8%. After adjustment for major cardiovascular risk factors, serum albumin, and HbA(1c), the odds ratio (95% CI) for 5-year mortality was 1.56 (1.07 to 2.30) for hyperhomocysteinemia and 1.26 (1.02 to 1. 55) per 5-micromol/L increment of tHcy. The odds ratio for 5-year mortality for hyperhomocysteinemia was 1.34 (0.87 to 2.06) in nondiabetic subjects and 2.51 (1.07 to 5.91) in diabetic subjects (P=0.08 for interaction). CONCLUSIONS Hyperhomocysteinemia is related to 5-year mortality independent of other major risk factors and appears to be a stronger (1.9-fold) risk factor for mortality in type 2 diabetic patients than in nondiabetic subjects.

Coexistence of Hereditary Homocystinuria and Factor V Leiden — Effect on Thrombosis

BACKGROUND Venous and arterial thromboembolism occurs in only about one third of patients homozygous for homocystinuria, which suggests that other, contributory factors are necessary for the development of thrombosis in these patients. Factor V Leiden, an R506Q mutation in the gene coding for factor V, is the most common cause of familial thrombosis and could be a potentiating factor. METHODS We determined activated partial-thromboplastin times in the presence and absence of activated protein C and tested for the factor V Leiden mutation in 45 members of seven unrelated consanguineous kindreds in which at least 1 member was homozygous for homocystinuria. RESULT Thrombosis (venous, arterial, or both) occurred in 6 of 11 patients with homocystinuria (age, 0.2 to 8 years). All six also had the factor V Leiden mutation. One patient with prenatally diagnosed homocystinuria who was also heterozygous for factor V Leiden has received warfarin therapy since birth and has not had thrombosis (age, 18 months). Of four patients with homocystinuria who did not have factor V Leiden, none had thrombosis (ages at this writing, 1 to 17 years). Three women who were heterozygous for both homocystinuria and factor V Leiden had recurrent fetal loss and placental infarctions. CONCLUSIONS Patients with concurrent homocystinuria and factor V Leiden can have an increased risk of thrombosis. Screening for factor V Leiden may be indicated in patient with homocystinuria and their family members.

Hyperhomocysteinaemia and endothelial dysfunction in young patients with peripheral arterial occlusive disease.

Abstract. Hyperhomocysteinaemia, defined as an abnormally high plasma homocysteine concentration after an oral methionine load, is common in young (≤ 50 years) patients with peripheral arterial occlusive disease. It is thought to predispose to atherosclerosis by injuring the vascular endothelium. Treatment with pyridoxine and/or folic acid may lower plasma homocysteine levels. In mildly hyperhomocysteinaemic patients with peripheral arterial occlusive disease, we studied the effect of daily treatment with pyridoxine (250 mg) plus folic acid (5 mg) on homocysteine metabolism (i.e. plasma concentrations in the fasting state and after methionine loading, in 48 patients) and on endothelial function (in 18 patients). Endothelial function was estimated as the plasma concentrations of the endothelium‐derived proteins, von Willebrand factor (vWF), thrombomodulin (TM), and tissue‐type plasminogen activator (tPA). At baseline, fasting homocysteine levels were above normal in 24 of the 48 patients (50%); post‐load levels, by definition, were above normal in 100% of patients. After 12 weeks of treatment, fasting and post‐load levels were normal in 98 and 100% of patients, respectively. Endothelial function was assessed in 18 patients who completed 1 year of treatment. At baseline, median vWF (235%) and TM (57.1 ng mL‐1) levels were above normal. At follow‐up, vWF levels had decreased to 170% (P= 0.01) and TM levels had decreased to 49 ng mL‐1 (P= 0.04). tPA levels were normal at baseline and did not change. Endothelial dysfunction is present in young patients with peripheral arterial occlusive disease and hyperhomocysteinaemia. Pyridoxine plus folic acid treatment normalizes homocysteine metabolism in virtually all patients, and appears to ameliorate endothelial dysfunction.

Genotype and phenotype in patients with dihydropyrimidine dehydrogenase deficiency

Abstract Dihydropyrimidine dehydrogenase (DPD) deficiency is an autosomal recessive disease characterised by thymine-uraciluria in homozygous deficient patients and has been associated with a variable clinical phenotype. In order to understand the genetic and phenotypic basis for DPD deficiency, we have reviewed 17 families presenting 22 patients with complete deficiency of DPD. In this group of patients, 7 different mutations have been identified, including 2 deletions [295–298delTCAT, 1897delC], 1 splice-site mutation [IVS14+1G>A)] and 4 missense mutations (85T>C, 703C>T, 2658G>A, 2983G>T). Analysis of the prevalence of the various mutations among DPD patients has shown that the G→A point mutation in the invariant splice donor site is by far the most common (52%), whereas the other six mutations are less frequently observed. A large phenotypic variability has been observed, with convulsive disorders, motor retardation and mental retardation being the most abundant manifestations. A clear correlation between the genotype and phenotype has not been established. An altered β-alanine, uracil and thymine homeostasis might underlie the various clinical abnormalities encountered in patients with DPD deficiency.

5,10-methylenetetrahydrofolate reductase (MTHFR) 677C→T and 1298A→C mutations are associated with DNA hypomethylation

A growing body of evidence has highlighted the role of abnormal DNA methylation patterns on inappropriate gene expression and promotion of disease.1–3 DNA methylation patterns are maintained by DNA methyltransferases,4–7 using S-adenosylmethionine (AdoMet) as the methyl group donor; AdoMet is then converted to S-adenosylhomocysteine (AdoHcy). Intracellular homocysteine (Hcy) is derived from AdoHcy hydrolysis through the action of AdoHcy hydrolase, a reversible reaction with a dynamic equilibrium that strongly favours AdoHcy synthesis rather than hydrolysis.8 Thus, an efficient metabolic removal of Hcy is required to prevent AdoHcy accumulation. The toxicity of intracellular AdoHcy accumulation lies in its high affinity binding to the catalytic region of most AdoMet dependent methyltransferases (including DNA methyltransferases), acting as its inhibitor.9 Thereby, any disturbance in Hcy metabolism is likely to disturb cellular methylation processes, including DNA methylation patterns. 5,10-methylenetetrahydrofolate reductase (MTHFR) is one of the main regulatory enzymes of Hcy metabolism that catalyses the reduction of 5,10-methylenetetrahydrofolate to 5-methyltetrahydrofolate, the methyl donor for the remethylation of Hcy to methionine. A common 677C→T transition in the MTHFR gene is a well established genetic determinant of hyperhomocysteinaemia, and results in a thermolabile protein, with a decreased enzymatic activity. The molecular basis of this thermolability is a missense mutation in the exon 4 of the MTHFR gene, a cytosine to thymine substitution at nucleotide 677, which converts an alanine to a valine codon in the N-terminal catalytic domain of the protein. The association between this MTHFR genotype and the total Hcy (tHcy) circulating levels is well known to be contingent on folate status.10,11 Recently, a second polymorphism associated with decreased enzymatic activity but not with thermolability was discovered in the MTHFR gene.12 This genetic variant corresponds to an adenosine to cytosine transversion at nucleotide 1298, in exon 7, leading to …