A mutation in the gene for the neurotransmitter receptor-clustering protein gephyrin causes a novel form of molybdenum cofactor deficiency

Gephyrin was originally identified as a membrane-associated protein that is essential for the postsynaptic localization of receptors for the neurotransmitters glycine and GABA(A). A sequence comparison revealed homologies between gephyrin and proteins necessary for the biosynthesis of the universal molybdenum cofactor (MoCo). Because gephyrin expression can rescue a MoCo-deficient mutation in bacteria, plants, and a murine cell line, it became clear that gephyrin also plays a role in MoCo biosynthesis. Human MoCo deficiency is a fatal disease resulting in severe neurological damage and death in early childhood. Most patients harbor MOCS1 mutations, which prohibit formation of a precursor, or carry MOCS2 mutations, which abrogate precursor conversion to molybdopterin. The present report describes the identification of a gephyrin gene (GEPH) deletion in a patient with symptoms typical of MoCo deficiency. Biochemical studies of the patient's fibroblasts demonstrate that gephyrin catalyzes the insertion of molybdenum into molybdopterin and suggest that this novel form of MoCo deficiency might be curable by molybdate supplementation.

Isolated 2-methylbutyrylglycinuria caused by short/branched-chain acyl-CoA dehydrogenase deficiency: identification of a new enzyme defect, resolution of its molecular basis, and evidence for distinct acyl-CoA dehydrogenases in isoleucine and valine metabolism

Acyl-CoA dehydrogenase (ACAD) defects in isoleucine and valine catabolism have been proposed in clinically diverse patients with an abnormal pattern of metabolites in their urine, but they have not been proved enzymatically or genetically, and it is unknown whether one or two ACADs are involved. We investigated a patient with isolated 2-methylbutyrylglycinuria, suggestive of a defect in isoleucine catabolism. Enzyme assay of the patient's fibroblasts, using 2-methylbutyryl-CoA as substrate, confirmed the defect. Sequence analysis of candidate ACADs revealed heterozygosity for the common short-chain ACAD A625 variant allele and no mutations in ACAD-8 but a 100-bp deletion in short/branched-chain ACAD (SBCAD) cDNA from the patient. Our identification of the SBCAD gene structure (11 exons; >20 kb) enabled analysis of genomic DNA. This showed that the deletion was caused by skipping of exon 10, because of homozygosity for a 1228G-->A mutation in the patient. This mutation was not present in 118 control chromosomes. In vitro transcription/translation experiments and overexpression in COS cells confirmed the disease-causing nature of the mutant SBCAD protein and showed that ACAD-8 is an isobutyryl-CoA dehydrogenase and that both wild-type proteins are imported into mitochondria and form tetramers. In conclusion, we report the first mutation in the SBCAD gene, show that it results in an isolated defect in isoleucine catabolism, and indicate that ACAD-8 is a mitochondrial enzyme that functions in valine catabolism.

Which dyspepsia patients will benefit from omeprazole treatment? Analysis of a Danish multicenter trial

OBJECTIVE

The effect of omeprazole therapy in dyspepsia is unpredictable. The aim of this study was to identify patient characteristics and symptoms associated with the omeprazole response to improve selection of patients for empirical treatment with omeprazole.

METHODS

Data from a randomized controlled trial of 471 patients with ulcer-like or reflux-like dyspepsia treated with omeprazole 20 mg daily (243 patients) or placebo (228 patients) for 2 wk were studied using logistic regression analysis. The patients were randomly divided into a model sample (N = 236) for modeling the association between the omeprazole response and descriptive variables, and a test sample (N = 235) for testing the obtained model.

RESULTS

In the model sample a high body mass index, the use of antacids or H2-blockers within the last month, or pain at night time were independently associated with a good omeprazole response, whereas the presence of nausea was associated with a poor omeprazole response. Using these variables combined into a therapeutic index, the independent test sample patients could be classified into predicted good (N = 56), medium (N = 88), and poor omeprazole responders (N = 91). In these groups the observed therapeutic gain of omeprazole (omeprazole response minus placebo response) was 39.4%, 19.3%, and 4.6%, respectively (p = 0.013). For clinical use, an easy-to-use pocket chart to obtain the therapeutic index in a given patient has been devised.

CONCLUSIONS

In dyspepsia the identification of potential responders to omeprazole can be improved by considering certain patient characteristics and symptoms associated with the omeprazole response. Applying these data using a simple pocket chart may assist decision about empirical omeprazole therapy in patients with dyspepsia in general practice.

Glutaryl-CoA dehydrogenase deficiency in Spain: evidence of two groups of patients, genetically, and biochemically distinct

Glutaryl-CoA dehydrogenase (GCDH) deficiency causes glutaric aciduria type I (GA I), an inborn error of metabolism that is characterized clinically by dystonia and dyskinesia and pathologically by neural degeneration of the caudate and putamen. Studies of metabolite excretion allowed us to categorize 43 GA I Spanish patients into two groups: group 1 (26 patients), those presenting with high excretion of both glutarate and 3-hydroxyglutarate, and group 2 (17 patients), those who might not be detected by routine urine organic acid analysis because glutarate might be normal and 3-hydroxyglutarate only slightly higher than controls. Single-strand conformation polymorphism (SSCP) screening and sequence analysis of the 11 exons and the corresponding intron boundaries of the GCDH gene allowed us to identify 13 novel and 10 previously described mutations. The most frequent mutations in group 1 were A293T and R402W with an allele frequency of 30% and 28%, respectively. These two mutations were also found in group 2, but always in heterozygosity, in particular in combination with mutations V400M or R227P. Interestingly, mutations V400M and R227P were only found in group 2, and at least one of these mutations was found in 11 of 15 unrelated alleles, accounting together for 53% of the mutant alleles in group 2. Therefore, it seems clear that two genetically and biochemically distinct groups of patients exist. The severity of the clinical phenotype seems to be closely linked to the development of encephalopathic crises rather than to residual enzyme activity or genotype. Comparison of GCDH protein with other acyl-CoA dehydrogenases (whose x-ray crystal structure has been determined) reveals that most of the mutations identified in GCDH protein seem to affect folding and tetramerization, as has been described for a number of mutations affecting mitochondrial beta-oxidation acyl-CoA dehydrogenases.

[Zellweger syndrome--a peroxisomal disease]

Zellweger syndrome is a fatal recessively inherited disease with disturbed function of many organs. The disease is caused by a defect of peroxisomes, subcellular organelles, which are absent in these patients. Several genes are necessary for the formation and function of the peroxisomes. The clinical picture of Zellweger syndrome can be caused by defects in a number of genes. On the other hand, clinically different diseases such as neonatal adrenoleucodystrophy and infantile Refsum disease have been shown to be allelic to Zellweger syndrome. We describe a typical Zellweger patient belonging to complementation group 1, which is by far the largest group containing more than half of the Zellweger patients.

Infrared and Raman spectroscopic investigations of the Nb(V) fluoro and oxofluoro complexes in the LiF-NaF-KF eutectic melt with development of a diamond IR cell

A vacuum-tight cell for infrared spectroscopic investigations of extremely corrosive melts, e.g., molten fluorides, has been constructed and tested up to 750 degrees C. The cell has a gold-lined sample chamber and a diamond window transparent for the infrared light. It can be furnished with a gold piston that enables the recording of short-path-length FTIR spectra of liquid samples. Solutions of Nb(V) in LiF-NaF-KF eutectic (FLINAK) with and without oxide additions have been investigated by FTIR and Raman spectroscopy. The presence of NbF7(2-), NbOF5(2-), and NbO2F4(3-) complexes was established in the molten state at 600 degrees C. After solidification NbF7(2-) was still the only Nb(V) all-fluoro complex present. Three oxofluoro complexes, NbOF6(3-), NbOF5(2-), and NbO2F4(3-), have been identified in the solid state. Typical frequency regions for the different complexes are established. Finally, it was shown that K2NbF7 can be used as an indicator to determine the oxide content of the sample melts.

Glutaryl-CoA dehydrogenase mutations in glutaric acidemia (type I): review and report of thirty novel mutations

Glutaric acidemia type I (GA1) is caused by mutations in the gene encoding the enzyme glutaryl-CoA dehydrogenase (GCD). Sixty-three pathogenic mutations identified by several laboratories are presented, 30 of them for the first time, together with data on expression in Escherichia coli and relationship to the clinical and biochemical phenotype. In brief, many GCD mutations cause GA1, but none is common. There is little if any relationship between genotype and clinical phenotype, but some mutations, even when heterozygous, seem especially common in patients with normal or only minimally elevated urine glutaric acid.

Influence of hepatitis delta virus infection on morbidity and mortality in compensated cirrhosis type B. The European Concerted Action on Viral Hepatitis (Eurohep)

BACKGROUND

The effect of hepatitis delta virus (HDV) infection on the clinical course of cirrhosis type B is poorly defined.

AIMS

To investigate the impact of HDV status on morbidity and mortality in cirrhosis type B.

PATIENTS/METHODS

Retrospective cohort study of 200 Western European patients with compensated cirrhosis type B followed for a median period of 6.6 years.

RESULTS

At diagnosis, 20% of patients had antibodies to HDV (anti-HDV); median age was lower in anti-HDV positive cirrhotics (34 v 48 years respectively). Kaplan-Meier five year probability of hepatocellular carcinoma (HCC) was 6, 10, and 9% in anti-HDV positive/HBeAg negative, anti-HDV negative/HBeAg negative, and anti-HDV negative/HBeAg positive cirrhotics respectively; the corresponding figures for decompensation were 22, 16, and 19% and for survival they were 92, 89, and 83% respectively. Cox regression analysis identified age, albumin concentration, gamma-globulin concentration, and HDV status as significant independent prognostic variables. After adjustment for clinical and serological differences at baseline, the risk (95% confidence interval) for HCC, decompensation, and mortality was increased by a factor of 3.2 (1.0 to 10), 2.2 (0.8 to 5.7), and 2.0 (0.7 to 5.7) respectively in anti-HDV positive relative to HDV negative cirrhotic patients. The adjusted estimated five year risk for HCC was 13, 4, and 2% for anti-HDV positive/HBeAg negative, anti-HDV negative/HBeAg negative, and anti-HDV negative/HBeAg positive cirrhotics respectively; the corresponding figures for decompensation were 18, 8, and 14% and for survival 90, 95, and 93% respectively.

CONCLUSIONS

HDV infection increases the risk for HCC threefold and for mortality twofold in patients with cirrhosis type B.

Preoperative prediction model of outcome after cholecystectomy for symptomatic gallstones

BACKGROUND

After cholecystectomy for symptomatic gallstone disease 20%-30% of the patients continue to have abdominal pain. The aim of this study was to investigate whether preoperative variables could predict the symptomatic outcome after cholecystectomy.

METHODS

One hundred and two patients were referred to elective cholecystectomy in a prospective study. Median age was 45 years; range, 20-81 years. A preoperative questionnaire on pain, symptoms, and history was completed, and the questions on pain and symptoms were repeated 1 year postoperatively. Preoperative cholescintigraphy and sonography evaluated gallbladder motility, gallstones, and gallbladder volume. Preoperative variables in patients with or without postcholecystectomy pain were compared statistically, and significant variables were combined in a logistic regression model to predict the postoperative outcome.

RESULTS

Eighty patients completed all questionnaires. Twenty-one patients continued to have abdominal pain after the operation. Patients with pain 1 year after cholecystectomy were characterized by the preoperative presence of a high dyspepsia score, 'irritating' abdominal pain, and an introverted personality and by the absence of 'agonizing' pain and of symptoms coinciding with pain (P < 0.000001). In a constructed logistic regression model 15 of 18 predicted patients had postoperative pain (PVpos = 0.83). Of 62 patients predicted as having no pain postoperatively, 56 were pain-free (PVneg = 0.90). Overall accuracy was 89%.

CONCLUSION

From this prospective study a model based on preoperative symptoms was developed to predict postcholecystectomy pain. Since intrastudy reclassification may give too optimistic results, the model should be validated in future studies.

Prediction of hepatic encephalopathy in paracetamol overdose: a prospective and validated study

BACKGROUND

Paracetamol overdose may cause hepatic encephalopathy (HE). This condition demands specialized care and, in some instances, liver transplantation evaluation. No model is available for predicting HE. We aimed to set up and validate a model for predicting the occurrence of HE in paracetamol overdose.

METHODS

Prospectively, 161 patients with single-dose paracetamol overdose and no HE (defined as hepatic coma grade II or more) on admission were studied during a 26-month period. Patients admitted during the first 13-month period constituted a learning set to construct a model to predict the occurrence of HE. Patients admitted in the second 13-month period constituted the validation set. Serial biochemical variables (measured twice daily), the time line after the overdose, and demographic data were used for univariate testing, and significant factors were assessed in various multiple logistic regression analyses.

RESULTS

Thirty-two patients (20%), 15 in the first period and 17 in the second, developed HE grade II. The best model (the highest chi-square) for HE included: log10 (hours from overdose to antidote treatment), log10 (plasma coagulation factors on admission), and platelet count hours from overdose (chi-square = 41.2, P < 0.00001). In the validation set 88% (confidence interval (CI), 64%-99%) of the patients who developed HE were correctly predicted by the constructed model, whereas 90% (CI, 79%-96%) of the patients in the non-HE group were correctly predicted.

CONCLUSIONS

The constructed model for predicting HE in paracetamol overdose proved sensitive and accurate in the validation set and should be valuable for transferring high-risk patients to a liver intensive care unit/transplantation facility.

Glutaric aciduria type I: pathomechanisms of neurodegeneration

In organotypic corticostriatal and hippocampal slice cultures from rat brain, 3-hydroxyglutaric acid but not glutaric and glutaconic acids induced neurodegeneration by activation of NMDA receptors. Electrophysiological investigations (Xenopus laevis oocytes expressing glutamate receptors; rat mixed cortex culture) revealed no direct interaction of 3-hydroxyglutaric acid with glutamate receptors. We speculate that 3-hydroxyglutaric acid induces a mild energy deprivation that interferes with the voltage-dependent Mg(2+)-block of NMDA receptors.

Pretransplant prediction of prognosis after liver transplantation in primary sclerosing cholangitis using a Cox regression model

Liver transplantation remains the only treatment for patients with end-stage primary sclerosing cholangitis (PSC); however, selection criteria for the procedure and its timing remains uncertain. The aim of this study was to identify pretransplant variables associated with survival after transplantation and to devise a Cox regression model for prediction of post-transplant survival. We studied 118 patients transplanted for PSC at the Queen Elizabeth Hospital, Birmingham, UK, being followed for up to 91/4 years after the procedure. The association between pretransplant data and the post-transplant survival up to 1 year was studied using the logrank test (univariate analyses) and Cox multiple regression analysis. Univariate analyses showed the following variables to be associated with a decreased post-transplant survival: high serum creatinine, high serum bilirubin, biliary tree malignancy, previous upper abdominal surgery, hepatic encephalopathy, ascites, and Crohn's disease, whereas ulcerative colitis was associated with increased post-transplant survival (all P </=.05). The final multiple Cox regression model included the following significant variables: inflammatory bowel disease, ascites, previous upper abdominal surgery, serum creatinine, and biliary tree malignancy (all P <.03). Biliary tree malignancy could be omitted from the Cox model with only slight loss of information. The results were validated using the data of 30 independent PSC patients from another center. These results can improve selection of patients with PSC for liver transplantation. The developed prognostic model for transplantation can be used in parallel with previously published prognostic models for nontransplantation. The obtained prognostic estimates will provide additional information that is useful for optimal timing of liver transplantation in the individual patient.

Molybdenum cofactor deficiency: first prenatal genetic analysis

Molybdenum cofactor (MoCo) deficiency leads to a combined deficiency of the molybdo-enzymes sulphite oxidase, xanthine dehydrogenase and aldehyde oxidase. No therapy is known for this rare disease, which results in neonatal seizures and other neurological symptoms identical to sulphite oxidase deficiency. It is inherited autosomal-recessively and leads to early childhood death. Prenatal diagnosis has been performed since 1983 by the measurement of sulphite oxidase activity, but no enzymatic carrier diagnosis is possible. The human genes necessary for MoCo biosynthesis have recently been cloned and mutations in the bicistronic MOCS1 gene could be identified in most European patients. In a Danish family we have now performed enzymatic and molecular genetic analysis in parallel after chorionic villus sampling. The sulphite oxidase activity in uncultured CVS material was found to be normal. A MOCS1 splice site mutation, found homozygous in the affected patient, was found in a heterozygous state in cultured chorionic cells. This confirmed that the fetus was not affected, since heterozygous carriers of a MoCo deficiency allele do not display any symptoms.

Optimal timing of liver transplantation for patients with primary biliary cirrhosis: use of prognostic modelling

BACKGROUND/AIMS

Liver transplantation remains the only definitive treatment for patients with end-stage primary biliary cirrhosis, although the optimal timing of the procedure remains uncertain. The aim of the study was to use prognostic modelling to determine the optimal timing of transplantation for patients with primary biliary cirrhosis.

METHODS

A prognostic model for predicting the survival of patients after transplantation was generated using the Cox regression model with data from 312 patients transplanted for primary biliary cirrhosis at the Queen Elizabeth Hospital, Birmingham. The prognosis after transplantation was compared to that without transplantation (using a previously published prognostic index for non-transplantation) both in these patients and in 98 non-transplanted primary biliary cirrhosis patients dying from the liver disease, in order to establish at what stage the prognosis with transplantation was better than without transplantation.

RESULTS

The prognostic index for transplantation included the following significant prognostic variables: serum bilirubin, serum albumin, age, year of transplantation, and the presence of ascites or treatment with diuretics. Comparison of prognosis with and without transplantation showed that the predicted gain in survival after transplantation becomes increasingly positive when the 6-month survival probability in the absence of transplantation falls below 0.85. In the non-transplanted patients this occurs on average about 8 months before death.

CONCLUSIONS

Comparison of the prognosis with and without transplantation provides a rational method for determining the optimum timing of the procedure which occurs approximately when the predicted 6-month survival probability without transplantation falls below 0.85.

Genotype and phenotype in patients with dihydropyrimidine dehydrogenase deficiency

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 beta-alanine, uracil and thymine homeostasis might underlie the various clinical abnormalities encountered in patients with DPD deficiency.

Genomic structure and mutational spectrum of the bicistronic MOCS1 gene defective in molybdenum cofactor deficiency type A

Molybdenum cofactor (MoCo) deficiency is a rare and devastating disease resulting in neonatal seizures and other neurological symptoms identical to those of sulphite oxidase deficiency. It is an autosomal recessive disease and no therapy is known. Most patients harbour MOCS1 mutations, which are found in both open reading frames of this unusual gene encoding the first two enzymes required in the MoCo biosynthesis pathway, MOCS1 A and MOCS1 B, in a single transcript. We describe genomic details as a prerequisite for comprehensive mutation analysis. In an initial cohort of 24 MoCo deficiency patients, we identified 13 different mutations on 34 chromosomes, with a mutation detection rate of 70%. Five mutations were observed in more than one patient and together accounted for two thirds of detected mutations. These comprise the most frequent mutation, R319Q, which is restricted to England, two Danish/German mutations (one missense and one splice site mutation), a missense mutation found in England and Germany, and a "Mediterranean" frameshift mutation. All patients with identified mutations are either homozygous or compound heterozygous for mutations in either of the two open reading frames corresponding to MOCS1 A and MOCS1 B, respectively. This observation suggests the existence of more than the two previously described complementation groups in MoCo biosynthesis.

Classification of dyspepsia. Identification of independent symptom components in 7270 consecutive, unselected dyspepsia patients from general practice

BACKGROUND

Several attempts to classify dyspepsia into subgroups have been proposed as a basis for empirical treatment and research. However, subgrouping has proved difficult due to overlap of symptoms between subgroups, and the response to empirical therapy is difficult to predict. We aimed to study whether natural symptom combinations occur in patients seeing general practitioners because of dyspepsia and whether symptom presentation could predict the effect of proton pump inhibitor treatment.

METHODS

The symptom presentation of 7270 consecutive, unselected patients with dyspepsia in general practice was studied by using principal-components analysis. The relation to the effect of omeprazole was studied in a subsample (n=471) with predominantly reflux-like or ulcer-like dyspepsia being included in a controlled clinical trial of omeprazole versus placebo.

RESULTS

Four principal components (factors), explaining 36% of the total variance, were found. They describe four independent dimensions in the symptoms of dyspepsia that can be interpreted meaningfully as representing A) acid-related disease of the upper gastrointestinal tract, B) irritable bowel disorder, C) dysmotility of the stomach/duodenum, and D) dysmotility of the esophagus. In the subsample the response to proton pump inhibition therapy was associated with high component-A scores, low component-B scores, and low component-C scores. A pocket chart was devised to obtain the component scores easily in new patients.

CONCLUSION

The analysis identified four characteristic, biologically meaningful dyspepsia components that express independent dimensions in the symptoms of patients with dyspepsia. The symptom scores corresponding to the four components may improve symptom-based diagnosis and thereby empirical therapy. In particular, the association between component scores and the effect of omeprazole suggests that classifying dyspepsia on the basis of these components may focus empirical omeprazole therapy even more.

Glutaric aciduria type I with high residual glutaryl-CoA dehydrogenase activity

Two brothers with dystonia and slight MRI changes in the basal ganglia had normal urinary glutaric acid excretion, but slightly increased 3-hydroxyglutarate and conjugated glutarate excretions. Both siblings have high residual glutaryl-CoA dehydrogenase activity, and are compound heterozygotes for two mutations - R227P and V400M reported to be disease-causing in patients with glutaric aciduria type I.