Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound   Target Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound

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Query: EC:2.6.1.44 (AGT)
770 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

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 (PH) is an autosomal-recessive disorder of endogenous oxalate synthesis characterized by accumulation of calcium oxalate primarily in the kidney. Deficiencies of alanine-glyoxylate aminotransferase (AGT) or glyoxylate reductase (GRHPR) are the two known causes of the disease (PH I and II, respectively). To determine the etiology of an as yet uncharacterized type of PH, we selected a cohort of 15 non-PH I/PH II patients from eight unrelated families with calcium oxalate nephrolithiasis for high-density SNP microarray analysis. We determined that mutations in an uncharacterized gene, DHDPSL, on chromosome 10 cause a third type of PH (PH III). To overcome the difficulties in data analysis attributed to a state of compound heterozygosity, we developed a strategy of "heterozygosity mapping"-a search for long heterozygous patterns unique to all patients in a given family and overlapping between families, followed by reconstruction of haplotypes. This approach enabled us to determine an allelic fragment shared by all patients of Ashkenazi Jewish descent and bearing a 3 bp deletion in DHDPSL. Overall, six mutations were detected: four missense mutations, one in-frame deletion, and one splice-site mutation. Our assumption is that DHDPSL is the gene encoding 4-hydroxy-2-oxoglutarate aldolase, catalyzing the final step in the metabolic pathway of hydroxyproline.
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PMID:Mutations in DHDPSL are responsible for primary hyperoxaluria type III. 2211 83

Primary hyperoxaluria (PH) is a rare autosomal recessive disease caused by the functional defect of alanine-glyoxylate aminotransferase (AGT) enzyme in the liver and it is characterized by the deposition of diffuse calcium oxalate crystals. A 38-year-old male patient presented with history of recurrent nephrolithiasis and has received chronic hemodialysis treatment for 2 years. Cadaveric renal transplantation was applied to the case. The patient was reoperated on postoperative day 13 because of the collection surrounding the urethra. During this operation, kidney biopsy was made due to late decrease in creatinine levels. Deposition of diffuse oxalate crystal was detected in allograft kidney biopsy, whereas in the 0-hour biopsy there were no oxalate crystals. Oxalate level was found to be high in a 24-hour urine specimen (118 mg/L, normal level: 7-44 mg/L). The patient was identified with primary hyperoxaluria and followed up in terms of systemic oxalate deposition as well as allograft kidney. In the kidney biopsy taken after 18 months, we detected that oxalate crystals almost entirely disappeared. In our case, bilateral preretinal, intraretinal, and intravascular diffuse oxalate crystals were detected, and argon laser photocoagulation treatments were needed for choroidal and retinal neovascularization. Repeated ophthalmic examinations showed the regressive nature of oxalate depositions. In the 18th month, fundus examination and fluorescein angiography revealed that oxalate crystals were significantly regressed. To increase the quality of life and slow down the systemic effects of oxalosis, kidney-only transplantation is beneficial.
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PMID:Regressive course of oxalate deposition in primary hyperoxaluria after kidney transplantation. 2086 24

Mutations in the alanine-glyoxylate aminotransferase gene (AGXT) are responsible for primary hyperoxaluria type I, a rare disease characterized by excessive hepatic oxalate production that leads to renal failure. A deeper understanding of the changes in the metabolic pathways secondary to the lack of AGXT expression is needed in order to explore substrate depletion as a therapeutic strategy to limit oxalate production in primary hyperoxaluria type I. We have developed an Agxt knockout (AgxtKO) mouse that reproduces some key features of primary hyperoxaluria type I. To improve our understanding of the metabolic adjustments subsequent to AGXT deficiency, we performed a proteomic analysis of the changes in expression levels of various subcellular fractions of liver and kidney metabolism linked to the lack of AGXT. In this article, we report specific changes in the liver and kidney proteome of AgxtKO mice that point to significant variations in gluconeogenesis, glycolysis and fatty acid pathways.
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PMID:Differential expression of liver and kidney proteins in a mouse model for primary hyperoxaluria type I. 2097 70

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

Oxalobacter colonization of rat intestine was previously shown to promote enteric oxalate secretion and elimination, leading to significant reductions in urinary oxalate excretion (Hatch et al. Kidney Int 69: 691-698, 2006). The main goal of the present study, using a mouse model of primary hyperoxaluria type 1 (PH1), was to test the hypothesis that colonization of the mouse gut by Oxalobacter formigenes could enhance enteric oxalate secretion and effectively reduce the hyperoxaluria associated with this genetic disease. Wild-type (WT) mice and mice deficient in liver alanine-glyoxylate aminotransferase (Agxt) exhibiting hyperoxalemia and hyperoxaluria were used in these studies. We compared the unidirectional and net fluxes of oxalate across isolated, short-circuited large intestine of artificially colonized and noncolonized mice. In addition, plasma and urinary oxalate was determined. Our results demonstrate that the cecum and distal colon contribute significantly to enteric oxalate excretion in Oxalobacter-colonized Agxt and WT mice. In colonized Agxt mice, urinary oxalate excretion was reduced 50% (to within the normal range observed for WT mice). Moreover, plasma oxalate concentrations in Agxt mice were also normalized (reduced 50%). Colonization of WT mice was also associated with marked (up to 95%) reductions in urinary oxalate excretion. We conclude that segment-specific effects of Oxalobacter on intestinal oxalate transport in the PH1 mouse model are associated with a normalization of plasma oxalate and urinary oxalate excretion in otherwise hyperoxalemic and hyperoxaluric animals.
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PMID:Enteric oxalate elimination is induced and oxalate is normalized in a mouse model of primary hyperoxaluria following intestinal colonization with Oxalobacter. 2116

Urinary excretion of oxalate is one of risk factors in urinary stone formation. Prevention of undesirable overflow into the production of oxalate definitely leads to a decrease of urolithiasis. The activity of serine : pyruvate/alanine : glyoxylate aminotransferase (SPT/AGT) or glyoxylate reductase/hydroxypyruvate reductase (GRHPR), the key enzyme of primary hyperoxlauria type 1 and 2, respectively, and their subcellular distribution highly affects the oxalate production. On the other hand, urolithiasis is tightly related to lifestyle disease, such as diabetes mellitus and insulin resistance. The hypothesis that insulin resistance induces mitochondria dysfunction, resulting in the decrease of mitochondria-related enzyme activity is a very attractive new treatment strategy of urolithiasis. Namely, the improvement of insulin resistance might prevent stone formation.
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PMID:[Future perspective in the treatment of urolithiasis based on oxalate metabolism]. 2130 60

Serine:pyruvate (or alanine:glyoxylate) aminotransferase (SPT or AGT) in the liver is unique in that its subcellular distribution is entirely peroxisomal in man and herbivores, and largely mitochondrial in carnivores. In rats, this enzyme is located in both mitochondria and peroxisomes and only the mitochondrial activity is markedly induced by glucagon. The mechanism of the species-specific dual organelle localization is either transcription of the gene from two different start sites or loss of upstream translation initiation ATG codon by mutations. In herbivores, peroxisomal localization of SPT appears to be indispensable to prevent excessive oxalate production by removing glyoxylate, an immediate precursor of oxalate, formed from glycolate in this organelle. In carnivores, its mitochondrial localization appears to be needed to metabolize glyoxylate formed from L-hydroxyproline in mitochondria. In addition, SPT contributes substantially to gluconeogenesis from serine in rabbit, human and dog livers, irrespective of its mitochondrial or peroxisomal localization. (Communicated by Shigetada Nakanishi, M.J.A.).
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PMID:Studies on a unique organelle localization of a liver enzyme, serine:pyruvate (or alanine:glyoxylate) aminotransferase. 2155 62

Primary hyperoxaluria is a genetic disorder in glyoxylate metabolism that leads to systemic overproduction of oxalate. Functional deficiency of alanine-glyoxylate aminotransferase in this disease leads to recurrent nephrolithiasis, nephrocalcinosis, systemic oxalosis, and kidney failure. We present a young woman with end-stage renal disease who received a kidney allograft and experienced early graft failure presumed to be an acute rejection. There was no improvement in kidney function, and she was required hemodialysis. Ultimately, biopsy revealed birefringent calcium oxalate crystals, which raised suspicion of primary hyperoxaluria. Further evaluations including genetic study and metabolic assay confirmed the diagnosis of primary hyperoxaluria type 1. This suggests a screening method for ruling out primary hyperoxaluria in suspected cases, especially before planning for kidney transplantation in patients with end-stage renal disease who have nephrocalcinosis, calcium oxalate calculi, or a family history of primary hyperoxaluria.
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PMID:Recurrence of primary hyperoxaluria after kidney transplantation. 2205 78

Primary hyperoxaluria type 1 (PH1) and type 2 (PH2) are rare genetic diseases that result from deficiencies in glyoxylate metabolism. The increased oxalate synthesis that occurs can lead to kidney stone formation, deposition of calcium oxalate in the kidney and other tissues, and renal failure. Hydroxyproline (Hyp) catabolism, which occurs mainly in the liver and kidney, is a prominent source of glyoxylate and could account for a significant portion of the oxalate produced in PH. To determine the sensitivity of mouse models of PH1 and PH2 to Hyp-derived oxalate, animals were fed diets containing 1% Hyp. Urinary excretions of glycolate and oxalate were used to monitor Hyp catabolism and the kidneys were examined to assess pathological changes. Both strains of knockout (KO) mice excreted more oxalate than wild-type (WT) animals with Hyp feeding. After 4 wk of Hyp feeding, all mice deficient in glyoxylate reductase/hydroxypyruvate reductase (GRHPR KO) developed severe nephrocalcinosis in contrast to animals deficient in alanine-glyoxylate aminotransferase (AGXT KO) where nephrocalcinosis was milder and with a lower frequency. Plasma cystatin C measurements over 4-wk Hyp feeding indicated no significant loss of renal function in WT and AGXT KO animals, and significant and severe loss of renal function in GRHPR KO animals after 2 and 4 wk, respectively. These data suggest that GRHPR activity may be vital in the kidney for limiting the conversion of Hyp-derived glyoxylate to oxalate. As Hyp catabolism may make a major contribution to the oxalate produced in PH patients, Hyp feeding in these mouse models should be useful in understanding the mechanisms associated with calcium oxalate deposition in the kidney.
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PMID:Hydroxyproline metabolism in mouse models of primary hyperoxaluria. 2249 66


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