Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UMLS:C0020500 (hyperoxaluria)
 912 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

In approximately one-third of primary hyperoxaluria type 1 patients, disease is associated with a unique protein sorting defect in which hepatic L-alanine:glyoxylate aminotransferase (AGT; EC 2.6.1.44), which is normally peroxisomal, is mistargeted to mitochondria. In all such patients analyzed to date, the gene encoding the aberrantly targeted AGT carries three point mutations, each of which specifies an amino acid substitution. In this paper we show that one of these substitutions, a proline-to-leucine at residue 11, is necessary and sufficient for the generation of a mitochondrial targeting sequence in the AGT protein. AGT with this substitution appears to interact specifically with the mitochondrial protein import machinery, via a discrete N-terminal domain of the AGT protein. The N-terminal 19 amino acids of AGT with this substitution are sufficient to direct mouse cytosolic dihydrofolate reductase to mitochondria, and a synthetic peptide corresponding to this same 19-amino acid region reversibly inhibits mitochondrial protein import, not only of AGT but also of ornithine transcarbamoylase, a genuine cytoplasmically synthesized mitochondrial protein. We have extended these studies to analyze a region of normal human AGT cDNA directly upstream of the coding region. This sequence appears to correspond to an ancestral mitochondrial targeting sequence deleted from the human coding region by point mutation at the initiation codon. We show that reestablishment of this initiation codon produces an active mitochondrial targeting sequence that is different to that found in the hyperoxaluria patients. These results are discussed with reference to the AGT targeting defect in primary hyperoxaluria and also in relation to the highly unusual species specificity of subcellular distribution of AGT among mammals.
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PMID:Mistargeting of peroxisomal L-alanine:glyoxylate aminotransferase to mitochondria in primary hyperoxaluria patients depends upon activation of a cryptic mitochondrial targeting sequence by a point mutation. 196 59

Considering the clinical heterogeneity of primary hyperoxaluria type I (PH1) and the fact that in many instances this diagnosis was made without enzymatic and immunohistochemical investigation, other disturbances of oxalate metabolism than those presently known can be expected in PH1. Using a gaschromatographic/mass spectrometric method that allows quantification of these acids, hyperoxaluria and hyperglycoluria was found repeatedly in two unrelated patients. The hyperoxaluria was unresponsive to pyridoxine. There was no nephrocalcinosis or urolithiasis. In the liver biopsy normal AGT activity and normal localization of this enzyme in the peroxisome was found. In one patient abnormal Km and maximal activity and mozaicism of AGT were excluded. Hyperoxaluria and hyperglycoluria were also found in other family members, suggesting autosomal dominant transmission. Although the underlying defect leading to hyperoxaluria and hyperglycoluria could not be identified in these patients, it is probable that they represent a separate type of primary hyperoxaluria.
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PMID:Hyperoxaluria with hyperglycoluria not due to alanine:glyoxylate aminotransferase defect: a novel type of primary hyperoxaluria. 891 45

The hyperoxaluria syndromes can be differentiated by the assessment of associated abnormalities in generation and urine excretion of metabolically related molecules. Based on the experience gained in our laboratory during the last decade, we have developed a comprehensive diagnostic work-up, which includes measurements of oxalate, glycolate and L-glycerate in plasma, urine and dialysis fluids, and an assay for AGT activity on liver biopsy. The availability of reliable assays for each of these parameters is indispensable for the recognition and differentiation of hyperoxalurias. Patients suspected to have abnormalities in oxalate metabolism are first screened by analysing spot urines and serum, and subsequently are subjected to more extensive studies using properly pre-treated blood samples and 24-hour urine collection. AGT activity, in the case of PH1, is assayed on few milligrams liver specimen by using a sensitive chromatographic procedure. Pertinent biochemistries will also assist in the long-term medical follow-up of these patients and in view of the choice of renal replacement or transplantation strategies.
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PMID:Biochemical approach to diagnosis and differentiation of primary hyperoxalurias: an update. 960 5

Primary hyperoxaluria (PH1) is a condition caused by a hepatic-based enzyme defect which can lead to renal failure due to oxalate stone disease, obstructive uropathy and nephrocalcinosis. It has been shown that the underlying metabolic defect can be corrected by liver transplantation and in most cases (renal failure having already occurred) is accompanied by a kidney graft. This paper describes the current results of 127 liver transplants performed in 117 patients over a 20-year period from 1984 to 2004 in 35 European centres. The mean age at onset of symptoms was 5.6 +/- 7.8 years and the mean age at which a diagnosis was made was 8.8 +/- 9.5 years. The diagnosis was confirmed by liver biopsy proven decreased AGT activity in 68% of cases, hyperoxaluria in 74%, hyperglycolicaciduria in 37% and hyperoxalaemia in 50%. Patients were transplanted at a mean age of 16.5 +/- 11.4 years following a period of dialysis of 3.2 +/- 3.2 years (range 0-14.4 years). 1-, 5- and 10-year patient survival values were 86, 80 and 69%, respectively, and liver graft survival rates of 80, 72 and 60% at the same time intervals. There have been 27 deaths and 10 liver retransplants have been carried out. Patient outcomes are improved when prolonged periods on dialysis and the complications of systemic oxalosis have not occurred.
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PMID:A 20-year experience of combined liver/kidney transplantation for primary hyperoxaluria (PH1): the European PH1 transplant registry experience 1984-2004. 1596 48

PH1 is an inborn error of the metabolism in which a functional deficiency of the liver-specific peroxisomal enzyme, AGT, causes hyperoxaluria and hyperglycolic aciduria. Infantile PH1 is the most aggressive form of this disease, leading to early nephrocalcinosis, systemic oxalosis, and end-stage renal failure. Infantile PH1 is rapidly fatal in children unless timely liver-kidney transplantation is performed to correct both the hepatic enzyme defect and the renal end-organ damage. The surgical procedure can be further complicated in infants and young children, who are at higher risk for vascular anomalies, such as IVC thrombosis. Although recently a limited number of children with IVC thrombosis have underwent successful kidney transplantation, successful multi-organ transplantation in a child with complete IVC thrombosis is quite rare. We report here the interesting and technically difficult case of a three-yr-old girl with a complete thrombosis of the IVC, who was the recipient of combined split liver and kidney transplantation for infantile PH1. Although initial delayed renal graft function with mild-to-moderate acute rejection was observed, the patient rapidly regained renal function after steroid boluses, and was soon hemodialysis-independent, with good diuresis. Serum and plasma oxalate levels progressively decreased; although, to date they are still above normal. Hepatic and renal function indices were at, or approaching, normal values when the patient was discharged 15-wk post-transplant, and the patient continues to do well, with close and frequent follow-up. This is the first report of a successful double-organ transplant in a pediatric patient presenting with infantile PH1 complicated by complete IVC thrombosis.
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PMID:Combined split liver and kidney transplantation in a three-year-old child with primary hyperoxaluria type 1 and complete thrombosis of the inferior vena cava. 1979 27

Primary hyperoxaluria type I (PH1) is an inborn error of metabolism caused by deficiency of the hepatic enzyme alanine-glyoxylate aminotransferase (AGXT or AGT) which leads to overproduction of oxalate by the liver and subsequent urolithiasis and renal failure. The current therapy largely depends on liver transplantation, which is associated with significant morbidity and mortality. To explore an alternative treatment, we used somatic gene transfer in a mouse genetic model for PH1 (Agxt1KO). Recombinant adeno-associated virus (AAV) vectors containing the human AGXT complementary DNA (cDNA) were pseudotyped with capsids from either serotype 8 or 5, and delivered to the livers of Agxt1KO mice via the tail vein. Both AAV8-AGXT and AAV5-AGXT vectors were able to reduce oxaluria to normal levels. In addition, treated mice showed blunted increase of oxaluria after challenge with ethylene glycol (EG), a glyoxylate precursor. In mice, AGT enzyme activity in whole liver extracts were restored to normal without hepatic toxicity nor immunogenicity for the 50 day follow-up. In summary, this study demonstrates the correction of primary hyperoxaluria in mice treated with either AAV5 or AAV8 vectors.
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PMID:Phenotypic correction of a mouse model for primary hyperoxaluria with adeno-associated virus gene transfer. 2111 25