Glutaryl-CoA dehydrogenase activity determined with intact electron-transport chain: application to glutaric aciduria type II.
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Biomedical subjects
Publications and source records attributed to E Christensen.
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In a mentally retarded boy, who excreted elevated amounts of glycine, D-glyceric acid and acylglycines and whose cells exhibited diminished D-glycerate dehydrogenase and glycine cleavage activity, investigations have been undertaken aiming at characterizing the relationship between the different accumulations. This was done in vivo by trying in a specific manner to alter in turn the degree of accumulation of each of the three classes of compounds and then monitoring changes in the others. The results suggest, that the D-glyceric acid accumulation is directly caused by the genetic defect, since the D-glyceric acid excretion was not altered by changes in degree of accumulation of either glycine or acylglycines. Similarly alterations in acylglycine excretion caused alterations in glycine but not in D-glyceric acid excretion. Based on these findings a model for the pathogenesis behind the accumulations of acylglycines and glycine is proposed.
Incubation of intact fibroblasts from a patients with glutaric aciduria type II with [2-14C]riboflavin showed normal synthesis of flavin mononucleotide and flavin adenine dinucleotide. This is taken as evidence for normal transport of riboflavin into the cells and normal activity of riboflavin kinase (EC 2.7.1.26) and flavin mononucleotide adenylyltransferase (EC 2.7.7.2). The ability of intact fibroblasts to oxidize 1-14C-fatty acids and [6-14C]lysine is impaired in the patient which together with the urinary excretion pattern of organic acids indicates a defective dehydrogenation of fatty acid acyl-CoAs and glutaryl-CoA. However, dehydrogenation of (C6-C10) fatty acid acyl-CoA derivatives and glutaryl-CoA was normal when the dehydrogenases were measured in fibroblast homogenate with artificial electron acceptors. In vivo, these dehydrogenases transfer their electrons to CoQ10 in the main electron transport chain via electron transfer flavoprotein and electron transfer flavoprotein dehydrogenase. Glutaric aciduria type II fibroblasts showed very diminished activity when the glutaryl-CoA dehydrogenase activity was measured without artificial electron acceptor but with intact endogenous electron transport system. As the NADH and succinate oxidation seems normal in glutaric aciduria type II patients, this is strong evidence for a defect in either the electron transfer flavoprotein or the electron transfer flavoprotein dehydrogenase.
Thirty-three consecutive patients admitted to the intensive care liver unit of Rigshospitalet with acute hepatic encephalopathy induced by viral hepatitis, drugs, or pregnancy were studied. All were treated with a standard anticoma regime. The 20 patients (61%) who died had a higher bilirubin level and lower total cholic acid conjugation and glycine cholic acid conjugation (p less than 0.05) than the surviving patients. Antipyrin clearance and galactose elimination capacity tended to be lower in the non-survival group than in the survival group (p = 0.09 and 0.11, respectively). Of single variables a bilirubin level of greater than 384 mumol/l gave the best prediction of non-survival (sensitivity, 0.80; specificity, 0.69; PVpos, 0.80; PVneg, 0.69; kappa, 0.49). However, a discriminant score based on combination of variables distinguished completely between non-survivors and survivors when validated by an unbiased method in which each patient is classified on the basis of the other patients' data. It is suggested that the discriminant score is used to select patients with very low probability of survival for liver transplantation or liver assistance procedures of unknown value.
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Pyruvate carboxylase activity was investigated in cultured fibroblasts from a patient shown to have hepatic pyruvate carboxylase deficiency. Under standard conditions, the activity in fibroblasts was 50% of controls (p less than 0.001). Kinetic investigations of the enzyme showed abnormal protein linearity with low activity at low protein concentration. Mixture of homogenates from the patient and a control revealed no endogenous inhibitor. Temperature stability of the mutant enzyme was similar to controls. Apparent kinetic constants for the substrates bicarbonate, ATP and pyruvate were in the patient 2.6 mmol/l, 0.08 mmol/l and 0.10 mmol/l compared to 2.1 mmol/l, 0.13 mmol/l and 0.22 mmol/l in controls, respectively. The 50% inhibitory concentration of oxaloacetate was 0.5 mmol/l in controls. However, no inhibitory effect of oxaloacetate was found for pyruvate carboxylase in fibroblasts from the patient. With acetyl-CoA, the apparent activation constant was 0.21 mmol/l in controls and 0.10 mmol/l in the patient, while the Hill coefficients were similar. These results may be explained by a mutation primarily affecting the transcarboxylation site of pyruvate carboxylase from the patient.
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Blood vessels in the pars distalis of the embryonic pituitary gland of the dwarf (dw) mutant mouse were analyzed by means of electron microscopy. Dwarf (dw/dw) embryos ranging in age from 15 through 18 days of gestation were obtained from matings of dwarf homozygotes in which reproductivity was induced by means of hormone supplementation and grafts of normal pituitary to the kidney capsule. Endothelial cells in vessels of the dwarf pituitary were retarded in development as indicated by a retention of macrovesicles and marginal flaps beyond embryonic stages when they normally subside in normal embryos, as well as a lag in the development of endothelial cell attenuations. This retardation may be causally related to the pituitary pathology involving faulty cytodifferentiation of somatotrophs and mammotrophs.
The first Scandinavian hyperphenylalaninaemic patient with a cofactor deficiency is described. By neonatal screening the Guthrie test showed a serum phenylalanine of 302 mumol/1 (5 mg/dl), which at age 6 weeks had fallen to high normal values. At age 5 1/2 months the serum phenylalanine was around 2000 mumol/1 and the child presented with severe neurological symptoms. The diagnosis of defect dihydrobiopterin biosynthesis was made by high performance liquid chromatography of the urine. Loading tests followed by daily treatment of the missing cofactor was able to keep the serum phenylalanine in the normal level. Because of persisting, yet diminishing neurological symptoms neurotransmitter treatment was started. Breast feeding as the cause of the low neonatal levels of serum phenylalanine and the late start of clinical symptoms is proposed and the importance of screening all hyperphenylalaninaemic newborns for defect biopterin metabolism is stressed.
The clinical and biochemical findings in a four-year-old girl with prolidase deficiency, treated with L-proline, manganese and ascorbic acid, are presented.
Dicarboxylic aciduria was found during hypoglycemic episode in a 14 months old girl. Her brother had died at the age of 4 years during febrile illness. A ketogenic diet induced in this patient a severe hypoglycemia. Urinary organic acid profile exhibited abnormal excretion of the C6-C10 dicarboxylic acids (adipic-suberic-sebacic) and related metabolites (5 hydroxyhexanoic, hexanoylglycine, suberyl glycine). This pattern suggested a defect in fatty acids beta oxidation. Plasma carnitine values was within control limits. Similar clinical findings and urinary organic acids excretion have been described in 6 patients since the initial case of Gregersen. Enzymatic studies on cultivated fibroblasts from our patient showed a defect in medium chain CoA dehydrogenase. The treatment of this disease consists of glucose infusion during attacks and prevention of fasting. This rare disease must be considered in a child with non ketotic hypoglycemia or Reye's syndrome.
In 33 patients with acute hepatic encephalopathy due to toxic or viral hepatitis the following analyses were performed: (24-14C)cholic acid conjugation and sulfation, plasma phenazone clearance, galactose elimination capacity, and concentrations of glycocholic acid and glycolithocholic acid sulfate in plasma. The (24-14C)cholic acid conjugation in patients with viral hepatitis was significantly lower in fatal cases than in patients who survived (p less than 0.002). In these patients the galactose elimination capacity and the plasma phenazone clearance were insignificantly lower. Tauro-(24-14C)cholic acid was the predominant metabolite of (24-14C)cholic acid in six patients, but in four patients with toxic hepatitis this metabolite was only found in trace amounts. Sulfation after 3 h of (24-14C)cholic acid accounted for 0-8.2% of the administered dose. The sulfate of glycolithocholic acid was found in the plasma of all patients. No survival limit with regard to the capacity for the (24-14C)cholic acid conjugation could be defined.
The main causes of 436 deaths among 532 patients with cirrhosis followed up for up to 16 years constituted liver failure (24%), liver failure with gastrointestinal bleeding (13%), gastrointestinal bleeding (14%), primary liver cell carcinoma (4%), other liver-related causes (2%), infections (7%), cardiovascular diseases (22%), extrahepatic malignancies (9%), and other non-liver-related causes (5%). Totally, 57% died of liver-related causes. A high frequency of liver-related death was found among patients with a short observation time, high biochemical activity, pronounced change in liver architecture, ascites, and other signs of a poor prognosis at the time of diagnosis. The findings favoured the hypothesis that cirrhosis of the liver is a disease with an initial active and a subsequent inactive phase. Half of the patients were treated with prednisone, but this had no detectable influence on the distribution of causes of or on the frequency of single causes of death as infections or gastrointestinal bleeding. The group of patients responding favourably to prednisone treatment with regard to survival (non-alcoholic women without ascites) showed causes of death not different from those of the total material.
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A liver biopsy material comprising 477 biopsies from 477 patients included in a prospective, unblinded, randomized trial of treatment of cirrhosis with prednisone has been re-evaluated using new and more restrictive histological criteria for the diagnosis of cirrhosis and chronic aggressive hepatitis (CAH). The material was divided according to the likelihood of cirrhosis being present: (A) cirrhosis (287 patients), (B) probably cirrhosis (101 patients) and (C) compatible with but not diagnostic for cirrhosis (89 patients). Each group was further divided according to the presence (I) or absence (II) of CAH. A total of 98 patients fulfilled the histological criteria for CAH. The effect of prednisone concerning survival was evaluated in each group. In the total group of patients with CAH a significant beneficial effect of prednisone was found (p = 0.04). Among these patients the subgroup with cirrhosis in addition (group I A) also showed a significant effect of prednisone, while groups I B and I C only had a trend towards a beneficial effect (p = 0.44 and p = 0.36, respectively). In patients without CAH in the biopsy (Group II, A + B + C), no effect of prednisone was seen although a trend towards a harmful effect was found in patients with cirrhosis (Group II A). Control patients with CAH in all three subgroups had an insignificantly shorter survival than patients without CAH. All the CAH groups significantly more often included female patients with no history of alcoholism and a lower frequency of spider naevi. In addition, the CAH groups were more active as judged by biochemical and histological variables. It was further disclosed that the presence of large piecemeal necroses indicated a favourable effect of prednisone treatment, while alcoholism, ascites and male sex acted as indicators for an unfavourable treatment effect.
A prospective, unblinded, randomized trial of treatment of cirrhosis and chronic aggressive hepatitis (CAH) with prednisone included 484 patients who were divided using both the clinical criteria: non-alcoholic females without ascites, and the morphological criterion: presence of a liver biopsy showing CAH. A total of 164 patients (34%) satisfied the three clinical criteria and biopsies from 95 patients (20%) showed CAH. By a cross-tabulation method between the two sets of criteria, four groups were formed. Evaluation of the treatment effect by means of relative death rate showed that the clinical criteria identified both a group of patients with a beneficial effect of prednisone (p less than 0.05) and a group with a harmful effect of the treatment (p less than 0.05). Patients with CAH also had a significant beneficial treatment effect, but patients without CAH showed only an insignificantly harmful effect of treatment. Patients fulfilling both sets of criteria had a beneficial effect of prednisone (p less than 0.05) and patients lacking both sets had a significantly harmful treatment effect. A significantly better survival was found in patients satisfying the clinical criteria without CAH in the biopsy than in patients with CAH and not fulfilling the clinical criteria (p = 0.03). In both the groups of patients with disagreement between the two sets of criteria, a trend towards a beneficial effect of prednisone was found. It is concluded that the simple clinical criteria in comparison with the histological criteria identify a larger group of patients with a beneficial effect of treatment.