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[Alpha-amino adipic aciduria: a rare psychomotor syndrome].

A 3.5-year-old boy with developmental motor retardation, hypotonicity, and severe speech disturbance had alpha-amino adipic acid in his blood and very high levels in his urine. In only 20 cases has this catabolite of lysine and hydroxylysine been found in high concentrations in urine, due to enzymatic block. The clinical features associated with alpha-amino adipic aciduria may include mental retardation, developmental and motor delay, learning difficulties, convulsions, speech problems and ataxia. 3 siblings had milder symptoms of psychomotor delay and intermediate degrees of alpha amino-adipic aciduria, suggesting that the described developmental deficits could be related to this metabolite or its derivatives.

2-Aminoadipic Acid↗

Perturbation of renal amino acid transport by brush border membrane vesicles in the vitamin D-deficient rat.

Vitamin D deficiency is characterized by secondary hyperparathyroidism, phosphaturia, bicarbonaturia, and generalized amino aciduria. While the site at which the phosphaturia ensues has been described to occur at the apical membrane of the renal proximal tubule, no studies are available for amino aciduria. Thus, weanling rats were fed five vitamin D-deficient diets for 4-6 weeks: (i) VLC, 0.02% Ca, 0.3% P; (ii) VLC + 1,25[OH]2D, same + 500 pmole ip for 2 days; (iii) LC, 0.45% Ca, 0.3% P; (iv) HC, 2.5% Ca, 0.3% P; and (v) VLP, 1.2% cA, 0.1% P. The normal diet contained 1.2% Ca, 0.7% P, and 2.5 micrograms% vitamin D. Amino acids, serum 25[OH]D, 1,25[OH]2D, and PTH, using a specific anti-rat PTH antibody, were measured. There were 4.65 +/- 1.1- and 10 +/- 1.39-fold increases in the urinary excretion of taurine and proline, respectively, irrespective of diet. Hypocalcemia, secondary hyperparathyroidism, and increased concentrations of urinary cAMP were demonstrated in all diets, except VLP. Taurinuria and prolinuria manifested at the renal brush border membrane. There was 21-25% and 26-39% attenuation in the peak of the overshoot of Na(+)-dependent uptake of taurine and proline, respectively, that was statistically significant as compared to that of normal diets (P less than 0.01). VLC resulted in a reduction in the Vmax of taurine (VLC, 78.26 +/- 6.88 vs normal, 115.4 +/- 6.26 pmole/mg protein/min, P less than 0.01) and proline (VLC, 402.06 +/- 31.26 vs normal, 589.49 +/- 37.42 pmole/mg protein/15 sec, P less than 0.01) uptake. Acute supplementation with pharmacological doses of 1,25[OH]2D normalized the Vmax of taurine and proline uptake, without affecting their renal excretion. The VLP diet induced and increase in the Km of taurine (VLP, 58.95 +/- 1.88 microM vs normal, 39.75 +/- 2.75 microM P less than 0.01) and proline (VLP, 116.75 +/- 8.87 microM vs normal, 76.82 +/- 7.27 microM P less than 0.01) uptake, without an associated perturbation in the Vmax of uptake. We conclude that the amino aciduria of vitamin D deficiency manifests at the apical membrane of the proximal tubule by an attenuation in the Na(+)-dependent uptake of amino acids. This is associated with a reduction in the initial rate of uptake or number of active transporters in the presence of secondary hyperparathyroidism and hypocalcemia, or a decrease in the affinity of the symport in the presence of P depletion. The data suggest the interplay of multiple factors in the causation of amino aciduria.

Amino Acids↗

Amino acid induced orotic aciduria.

Twenty amino acids were examined for their effects on urinary orotic acid excretion. Except for arginine and ornithine, all of the remaining amino acids tested induced a mild orotic aciduria in rats 2 hours post feeding. Two ammonium salts, and urease also acted, as inducers of orotic aciduria. The ammoneogenic properties of the amino acids tested could not solely explain the induced excretion of orotic acid. Only serine, glutamine, NH4Cl, (NH4)2CO3, and urease increased orotic acid excretion in the 24 hour fasted rat. Administration of 0.5 mmoles of arginine or ornithine ameliorated the mild orotic aciduria induced by either glycine or lysine. Arginine was shown to be more efficacious in preventing glycine induced orotic aciduria than was ornithine. Amino acid induced orotic aciduria is dependent upon the physiological state of the animal, varying with the state of digestion and the supply of arginine.

Amino Acids↗

Characterization of renal defects in dogs with a syndrome similar to the Fanconi syndrome in man.

Ten adult dogs with multiple spontaneous defects of renal tubular reabsorption were studied. Clinical signs included polydipsia, polyuria, and glycosuria for 2 to 12 months. Eight of the dogs were Basenjis. Urinalyses revealed hyposthenuria, glycosuria, and amino aciduria in most dogs. Renal function was normal in 5 dogs and slightly reduced in the remainder. Moderate metabolic acidosis had developed in 3 dogs. Renal clearance studies revealed reduced tubular reabsorption of glucose, phosphate, sodium, potassium, and uric acid. Abnormal glucose tubular maximal curves were found. Results of oral glucose tolerance tests were normal. Two patterns of abnormal amino aciduria were evident: generalized amino aciduria and a pattern similar to that of cystinuria in dogs. Radiography of long bones and bone densitometry did not reveal any skeletal abnormalities. Five of the dogs died within 90 days of diagnosis; death was due to acute renal failure associated with profound dehydration, acidosis, and papillary necrosis. The other dogs remained stable without treatment after 18 months. Histopathology of kidneys did not reveal uniform abnormalities; some dogs had variable and nonspecific changes and others were normal. Electron microscopy did not reveal ultrastructural abnormalities in renal tubular cells. It was concluded that the syndrome in these dogs represents a new entity of renal disease in dogs, similar to idiopathic Fanconi syndrome in man.

Animals↗

[Glutathion-synthetase deficiency with 5-oxoprolinuria. Two new cases and a review of the literature (author's transl)].

Hereditary deficiency in glutathion- synthetase is a rare disease presenting up to now either with a congenital non-spherocytic anaemia or with a metabolic acidosis, most often neonatal and accompanied by a pyroglutamic amino-aciduria (5-oxoprolinuria). These two syndrome may be present together or exist independently. Pyroglutamic amino-aciduria is the result of extension of the deficiency to non-haematopoietic cells, in particular renal. Two new cases of glutathion-synthetase deficiency are reported: both with haemolytic anaemia and moderate pyroglutamic amino-aciduria, in the absence of clinical signs of metabolic acidosis. The clinical, haematological and biochemical heterogeneity of the deficiency is illustrated by these two cases and datas from the literature.

Anemia, Hemolytic, Congenital↗

[Relation between metabolic amino acid defect and familial occurring epilepsy].

Within the framework of amino-aciduria research on familial epilepsy the authors describe the clinical picture, E. E. G., and biochemical urine findings for six members of one family. Three brothers and sisters suffered from oligophrenia and epileptic fits. The influence of therapy was also followed in the youngest patient. The authors stress the need for examining the urine for amino-aciduria in some cases of genuine epilepsy especially of a familial character. What is also emphasized is the necessity of employing a precise biochemical method of examination. The high-voltage electrophoresis in combination with paper chromatography was used. It was by using this particular method that the authors were able to observe variations in the elimination through urine of both free and peptide-bound amino acids in the parents as well as in three diseased children.

Adolescent↗

Neonatal 5-oxoprolinuria: difficult-to-diagnose?

A male newborn infant presented with metabolic acidosis and haemolytic anaemia. Renal tubular acidosis was suspected in the absence of amino aciduria and the patient was treated with sodium bicarbonate. Two years later, the chronic acidosis, clinical observation of developmental delay and ataxia prompted further investigational studies. 5-Oxoprolinuria was identified by gas-liquid chromatography and confirmed by mass spectrometry after an initial mass spectrum analysis reported a glutamic acid artifact. Glutathione and glutathione synthetase in erythrocytes were 25% and 5% of control values, respectively. On the basis of neonatal metabolic acidosis, without amino aciduria and an elevated reticulocyte count, a recommendation is made for blood glutathione and urine 5-oxoproline screening, followed by glutathione synthetase assay for confirmation of neonatal 5-oxoprolinuria.

Acidosis↗

[A drug-induced transient Fanconi syndrome associated with pure red cell aplasia: pathophysiology of the electrolyte disorders].

A 55-year-old female with a long history of pure red cell aplasia temporarily manifested Fanconi syndrome with hypophosphatemia, hypouricemia, glycosuria, acidic amino aciduria, but not metabolic acidosis nor hypokalemia. These abnormalities completely resolved in 3-4 weeks after withdrawal of several drugs, suggesting that the cause of her Fanconi syndrome could be attributed to a drug or a combination of multiple drugs, though lymphocyte stimulating tests revealed negative results for all possible drugs. Postmortem specimen of her kidneys showed mild mesangial proliferation without significant changes in tubular and interstitial regions. Massive ferrous precipitations were found in the zona glomerulosa of the adrenal glands. The pathophysiology of Fanconi syndrome shown in the patient was likely to have been a drug-induced transient and mild dysfunction of the Na+/K+ pump of the renal proximal tubules, which might also explain the selective amino aciduria. The absence of hypokalemia corroborates well with both a lack of bicarbonaturia and hemochromatosis-induced adrenal insufficiency. Patients with a renal dysfunction associated with electrolyte derangements and without proteinuria or azotemia should be under vigilant observation when using many drugs.

Fanconi Syndrome↗

1H NMR pattern recognition and 31P NMR studies with d-Serine in rat urine and kidney, time- and dose-related metabolic effects.

Proton NMR spectroscopy of urine has previously been used to gain insight into the site and mechanism of toxic injury to the kidney. d-Serine injures the rat kidney, causing selective necrosis of the proximal straight tubules. Damage is accompanied by proteinuria, glucosuria, and amino aciduria, the latter preceding the onset of necrosis. This study has employed (1)H NMR spectroscopy of urine and (1)H NMR and (31)P NMR spectroscopy of kidney extracts to examine the nephrotoxic action of d-serine. Urine was collected 0-8 h (all doses) and 8-24, 24-48, 48-72, 72-96, and 96-120 h (500 mg/kg only) postdosing from Alderley Park rats given d-serine (62.5, 125, 250, and 500 mg/kg ip). (1)H NMR spectra were monitored for markers of tubular damage. Additionally, ATP and ADP were quantitated in kidney perchloric acid extracts, prepared after 0.5, 1, 2, 4, and 8 h (500 mg/kg) to assess energy status; serine was also measured in these samples. At 500 mg/kg, glucosuria, amino aciduria, and reduced citrate, alpha-ketoglutarate, and succinate were observed in urine at 0-8 h. Furthermore, serine and pyruvate levels were elevated at this time. After 8-24 h, similar changes were observed; however, they were more severe reflecting the development of the lesion prior to recovery. These perturbations were dose-related, in particular, for serine and pyruvate, with no alterations seen at 62.5 mg/kg. Kidney serine concentration rapidly increased, where it was maximal after 30 min and cleared by 8 h. A decline in ATP, to approximately 60-70% of control, was observed within the kidney at 2-4 h postdosing, when necrosis first becomes evident suggesting that mitochondrial function might be impaired in the early stages of d-serine-induced nephrotoxicity. The use of NMR spectroscopy has given a comprehensive overview of the effects of d-serine in vivo. Information on the excretion of serine and its effect on renal energy metabolism provides insight into the possible mechanism of renal tubule injury.

Animals↗

Induction of lysinuria in the rat by two para-substituted guanidinophenylalanines.

1. p-Guanidino- and p-guanidinomethyl-phenylalanine increase the renal excretion of lysine especially and, to some extent, cystine in the phenylalanine-loaded rat. The methyl derivative is the more effective. 2. The lysinuria is dose-dependent, reversible, pronounced when the intravenous infusion of analogue exceeds 10 mumol min-1 kg-1 and does not appear to be secondary to changes in urine flow or sodium excretion. 3. A mechanism for induced basic amino-aciduria conditions is suggested.

Amino Acids↗

D-serine nephrotoxicity. The nature of proteinuria, glucosuria, and aminoaciduria in acute tubular necrosis.

Administration of D-serine to rats induced acute necrosis of the proximal straight tubules, proteinuria, glucosuria, and aminoaciduria. Proteinuria and glucosuria developed at the onset of tubular necrosis and disappeared when the tubules were completely relined by new epithelium. Our findings suggest (1) that abnormal loss of protein and glucose in urine is due to diffusion of these substances from interstitium to tubular fluid across the denuded permeable basement membranes of the necrotic tubules, and (2) that tubular cells normally are a barrier to diffusion of certain solutes betweeen interstitial and tubular fluids. Amino-aciduria preceded the onset of tubular necrosis and increased excretion of some amino acids persisted after tubular repair. Thus, D-serine-induced aminoaciduria may be due to impaired reabsorption of amino acids by the injured proximal straight tubules, as well as by backward diffusion of amino acids from the interstitium.

Acute Kidney Injury↗

Genetic heterogeneity in cystinuria: the SLC3A1 gene is linked to type I but not to type III cystinuria.

Cystinuria is an autosomal recessive amino-aciduria where three urinary phenotypes have been described (I, II, and III). An amino acid transporter gene, SLC3A1 (formerly rBAT), was found to be responsible for this disorder. To assess whether mutations in SLC3A1 are involved in different cystinuria phenotypes, linkage with this gene and its nearest marker (D2S119) was analyzed in 22 families with type I and/or type III cystinuria. Linkage with heterogeneity was proved (alpha = 0.45; P < 0.008). Type I/I families showed homogeneous linkage to SLC3A1 (Zmax > 3.0 at theta = 0.00; alpha = 1), whereas types I/III and III/III were not linked. Our data suggest that type I cystinuria is due to mutations in the SLC3A1 gene, whereas another locus is responsible for type III. This result establishes genetic heterogeneity for cystinuria, classically considered as a multiallelic monogenic disease.

Adolescent↗

The aminogram of the urine produced by the preserved kidney.

The function of autogenous canine kidneys may be considered even after successful preservation and reperfusion to be pathological for about 3 to 4 days, since a condition characterized by proteinuria and increased amino aciduria exists for a while.

Amino Acids↗

Uptake of neutral alpha- and beta-amino acids by human proximal tubular cells.

The transport characteristics of amino acids in primary cell cultures from the proximal tubule of human adults (AHKE cells) were examined, using alpha-aminoisobutyric acid (AIB) and beta-alanine as representatives of alpha- and beta-amino acids, respectively. The Na(+)-gradient dependent influx of AIB occurred by a single, saturable transport system, whereas the Na(+)-gradient dependent uptake data for beta-alanine could be described in terms of two-independent transport components as well as one-transport one-leak model with identical kinetic constants for the high-affinity system. Competition experiments revealed that all the neutral amino acids tested reduced the uptake of AIB, whereas there was no effect of taurine, L-aspartic acid, and L-arginine. By contrast, the influx of beta-alanine was only drastically reduced by beta-amino acids, whereas the inhibition by neutral alpha-amino acids was relatively low. Nor did L-arginine and L-aspartic acid affect the uptake of beta-alanine into AHKE cells. Comparison with the results obtained for normal (NHKE) and immortalized (IHKE) embryonic cells suggested an unaltered expression of the types of transport carriers for neutral alpha- and beta-amino acids in the embryonic and AHKE cells. However, the uptake capacity of the above-mentioned transport proteins was relatively smaller in the embryonic kidney compared with the adult human kidney, which may explain, at least partly, the phenomenon of physiologic amino aciduria in neonates.

Adult↗

The molecular basis of neutral aminoacidurias.

Recent success in the molecular cloning and identification of apical neutral amino acid transporters has shed a new light on inherited neutral amino acidurias, such as Hartnup disorder and Iminoglycinuria. Hartnup disorder is caused by mutations in the neutral amino acid transporter B(0) AT1 (SLC6A19). The transporter is found in kidney and intestine, where it is involved in the resorption of all neutral amino acids. The molecular defect underlying Iminoglycinuria has not yet been identified. However, two transporters, the proton amino acid transporter PAT1 (SLC36A1) and the IMINO transporter (SLC6A20) appear to play key roles in the resorption of glycine and proline. A model is presented, involving all three transporters that can explain the phenotypic variability of iminoglycinuria.

Amino Acid Transport Systems, Neutral↗