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Amino acid Hartnup disease

Inherited defects in amino acid transport affect epithelial cells of the gastrointestinal tract and renal tubules. Some affect transport of neutral amino acids Hartnup disease), others that of basic amino acids and ornithine and cystine (cystinuria), or of glycine and proline (Chapter 12). Cystinosis is an intracellular transport defect characterized by high intralysosomal content of free cystine in the reticuloendothelial system, bone marrow, kidney, and eye. After degradation of endocytosed protein to amino acids within lysosomes, the amino acids normally are transported to the cytosol. The defect in cystinosis may reside in the ATP-dependent efflux system for cystine transport, and particularly in the carrier protein. [Pg.333]

Hartnup disease is a rare genetic condition in which there is a defect of the membrane transport mechanism for tryptophan and other large neutral amino acids. The result is that the intestinal absorption of free tryptophan is impaired, although dipeptide absorption is normal. There is a considerable urinary loss of tryptophan (and other amino acids) as a result of the failure of the normal reabsorption mechanism in the renal tubules - renal aminoaciduria. In addition to neurological signs that can be attributed to a deficit of tryptophan for the synthesis of serotonin in the central nervous system, the patients show clinical signs of pellagra, which respond to the administration of niacin. [Pg.224]

Hartnup s disease. There is a defect in the epithelial transport of neutral amino acids (e.g., tryptophan) leading to poor absorption and excess excretion of these amino acids. Clinical signs resemble those of niacin deficiency (tryptophan is a precursor of niacin), namely the 3 D s Diarrhea, Dementia, Dermatitis. The condition responds to nicotinamide administration. Fan-coni s syndrome is a more generalized defect in molecular transport, involving a multitude of amino acids, glucose, calcium, phosphate, proteins, and other molecules. There may be decreased growth and rickets. [Pg.54]

Metabolic studies by Milne et al. (M8) showed that in Hartnup disease the renal aminoaciduria is more constant than the excessive excretion of indican and indolic acids (indoleacetic acid, indolelactic acid, and indoleacetylglutamine). After ingestion of L-tryptophan in this disease there is usually delayed and incomplete absorption from the gut of the amino acid which is partly converted, by intestinal bacteria, to indole... [Pg.119]

The Hartnup disease described in 1956 (B2) under the title hereditary pellagra-like skin rash with temporary cerebellar ataxia, constant renal aminoaciduria, and other bizarre biochemical features evidently belongs to the diseases related to inborn errors of metabolism due to inherited differences. As was pointed out by Harris (H3), very often the detection of urinary amino acid metabolites has represented the starting point of the investigation of different genetic biochemical disorders. A recent study (A8) showed that the excess production of indole by colon bacteria in 15 cases of Hartnup disease was due entirely to an increased amount of tryptophan contained in the large bowel, and not to an abnormality of the bacteria themselves. [Pg.120]

Cysteine is oxidized to cystine, which may crystallize, forming kidney stones. In Hartnup s disease, the transport of neutral amino adds is defective in both intestinal cells and kidney tubules, resulting in deficiencies of essential amino acids. [Pg.263]

Hartnup disease is a disorder of renal tubular and intestinal absorption of tryptophan and other neutral amino acids. [Pg.363]

Pellagra-like symptoms can occur in Hartnup s disease and carcinoid syndrome. Hartnup s disease is an inherited disorder of amino acid transport (Chapter 17) in which niacin deficiency presumably develops because niacin intake is inadequate to supply metabolic needs when combined with the decreased absorption of dietary tryptophan. In carcinoid syndrome, up to 60% of available dietary tryptophan is diverted to formation of 5-hydroxytryptamine (serotonin) by what is normally a minor pathway. [Pg.924]

Which clinical laboratory observation below is suggestive of Hartnup disease (neutral amino acid transport deficiency) ... [Pg.202]

Hartnup disease is an inherited autosomal recessive disease that manifests itself in malabsorption of neutral amino acids, including tryptophan, in the gastrointestinal tract and also in deficient reabsorption of these amino acids in the renal tubules. The deficient uptake of tryptophan can result in a pellagra-like condition, which may include mental manifestations such as... [Pg.73]

Jonas, A. J. and Butler, I. J., Circumvention of defective neutral amino acid transport in Hartnup disease using tryptophan ethyl ester, /. Clin. Invest., 84, 200, 1989. [Pg.84]

Hartnup disease Is another genetically determined and relatively rare autosomal recessive disorder. It is caused by a defect in the transport of neutral amino acids across both intestinal and renal epithelial cells. The signs and symptoms are, in part, caused by a deficiency of essential amino acids (see Clinical Comments). Cystinuria and Hartnup disease involve defects in two different transport proteins. In each case, the defect is present both in intestinal cells, causing malabsorption of the amino acids from the digestive products in the intestinal lumen and in kidney tubular cells, causing a decreased resorption of these amino acids from the glomerular filtrate. [Pg.690]

However, some patients with the Hartnup biochemical phenotype eventually develop pellagra-like manifestations, which usually include a photosensitivity rash, ataxia, and neuropsychiatric symptoms. Pellagra results from a dietary deficiency of the vitamin niacin or the essential amino acid tryptophan, which are both precursors for the nicotinamide moiety of NAD and NADP. In asymptomatic patients, the transport abnormality may be incomplete and so subtle as to allow no phenotypic expression of Hartnup disease. These patients also may be capable of absorbing some small peptides that contain the neuttal amino acids. [Pg.694]

Hartnup disease, an autosomal recessive trait that interferes with the absorption of tryptophan, and carcinoid syndrome in which the amino acid is preferentially oxidized to 5-hydroxytryptophan and serotonin. Prolonged treatment with the drug isoniazid, which competes with pyridoxal 5 -phosphate (a vitamin Be-derived coenzyme required in the tryptophan-to-niacin pathway), also reduces the conversion of tryptophan to niacin. Oral contraceptives that contain high doses of estrogen increase tryptophan conversion efficiency (Braidman and Rose 1971). [Pg.143]

Aminoacidurias may be generalized, when there is excessive secretion of several non-related amino acids, or specific, when there is excess excretion of a single amino acid or a related group of them (as in cystinuria or Hartnup disease). [Pg.24]

An inborn error in which there is defective intestinal and renal transport of neutral amino acids, one of these being tryptophan. This amino acid is normally converted to the vitamin, nicotinamide. The clinical features of Hartnup disease are similar to the nicotinamide deficiency disease, pellagra, being due to the low amounts of tryptophan available for nicotinamide synthesis. The disease can be diagnosed by the presence of large amounts of indole compounds in the urine, which result from the action of gut bacteria on the unabsorbed dietary tryptophan. [Pg.174]

It can be converted by intestinal flora and probably by the tissues to the vitamin, nicotinamide. A dietary deficiency of tryptophan can therefore result in nicotinamide deficiency if dietary intake of nicotinamide is also low. Symptoms resembling those of nicotinamide deficiency can also occur in the inborn error, Hartnup disease, where body tryptophan levels are reduced due to diminished reabsorption of the amino acid from the renal tubules. [Pg.356]

In Hartnup disease [118] there is a defect in the reabsorption of the fourth group of amino acids and these 13 mono-amino mono-carboxylic acids are excreted in the urine in large amounts [119]. The concentrations in plasma are low. A similar defect occurs in the jejunal mucosa in most of the reported cases—greatly reduced absorption of tryptophan from the gut has been demonstrated [120] and there is evidence of reduced absorption of the other 12 amino acids involved [121]. A variant lacking the jejunal defect has been reported [117]. The failure to absorb tryptophan from the gut results in relatively large amounts of this amino acid entering the colon and being acted on by the colonic flora [120]. Considerable amounts of... [Pg.241]

Hartnup disease Indole-3-acetic add Indole-3-lactic adds Indole-3-acetylglutamine Neutral monoamino mono-carboxylic acids except glycine and the iminoacids. Indican Neutral amino add-transport system ... [Pg.218]


See other pages where Amino acid Hartnup disease is mentioned: [Pg.258]    [Pg.322]    [Pg.541]    [Pg.224]    [Pg.120]    [Pg.1116]    [Pg.234]    [Pg.188]    [Pg.193]    [Pg.216]    [Pg.219]    [Pg.74]    [Pg.19]    [Pg.585]    [Pg.84]    [Pg.571]    [Pg.217]    [Pg.243]   


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Hartnup disease

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