Lysinuric protein intolerance

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Lysinuric protein intolerance
Other namesHyperdibasic aminoaciduria type 2,Cationic aminoaciduria or Familial protein intolerance
L-lysine-2D-skeletal.png
Lysine
Specialty Endocrinology   OOjs UI icon edit-ltr-progressive.svg

Lysinuric protein intolerance (LPI) is an autosomal recessive [1] metabolic disorder affecting amino acid transport. It is characterised by the body's inability to properly digest and use certain proteins. [2] This condition leads to various metabolic complications and is typically diagnosed in infancy or early childhood. [3]

Contents

About 140 patients have been reported, almost half of them of Finnish origin. Individuals from Japan, Italy, Morocco and North Africa have also been reported plus one in Bixby, Oklahoma.

Signs and symptoms

Infants with LPI are usually symptom-free when breastfed because of the low protein concentration in human milk, but develop vomiting and diarrhea after weaning. The patients show failure to thrive, poor appetite, growth retardation, enlarged liver and spleen, prominent osteoporosis and osteopenia, [4] delayed bone age and spontaneous protein aversion. Forced feeding of protein may lead to convulsions and coma. Mental development is normal if prolonged episode of hyperammonemia can be avoided. Some patients develop severe pulmonary and kidney complications. High levels of plasma glutamine and glycine are observed.[ citation needed ]

Genetic Basis

LPI has been associated with SLC7A7. [5] LPI is caused by mutations in the SLC7A7 gene, which encodes for a protein involved in the transport of amino acids across cell membranes. Mutations in this gene impair the transport function, leading to the characteristic amino acid imbalances seen in LPI patients. [6]

Mechanism

Lysinuric protein intolerance has an autosomal recessive pattern of inheritance. Autorecessive.svg
Lysinuric protein intolerance has an autosomal recessive pattern of inheritance.

In LPI, urinary excretion of cationic amino acids (ornithine, arginine and lysine) is increased and these amino acids are poorly absorbed from the intestine. Therefore, their plasma concentrations are low and their body pools become depleted. Deficiency of arginine and ornithine restricts the function of the urea cycle and leads to hyperammonemia after protein-rich meals. Deficiency of lysine may play a major role in the skeletal and immunological abnormalities observed in LPI patients.[ citation needed ]

Clinical Features

The symptoms of LPI typically appear after weaning from breast milk to a protein-rich diet. Common symptoms include poor growth, muscle weakness, enlarged liver and spleen, and frequent infections. Neurological symptoms such as confusion and seizures can also occur. [7]

Diagnosis

The diagnosis is based on the biochemical findings (increased concentrations of lysine, arginine and ornithine in urine and low concentrations of these amino acids in plasma, elevation of urinary orotic acid excretion after protein-rich meals, and inappropriately high concentrations of serum ferritin and lactate dehydrogenase isoenzymes) and the screening of known mutations of the causative gene from a DNA sample. [8]

Treatment

Treatment of LPI consists of protein-restricted diet and supplementation with oral *GeneReview/NIH/UW entry on Lysinuric Protein Intolerance citrulline. Citrulline is a neutral amino acid that improves the function of the urea cycle and allows sufficient protein intake without hyperammonemia. [9]

Prognosis

Under proper dietary control and supplementation, the majority of the LPI patients are able to have a nearly normal life. However, severe complications including pulmonary alveolar proteinosis and chronic kidney disease may develop even with proper treatment. [10] Fertility appears to be normal in women, but mothers with LPI have an increased risk for complications during pregnancy and delivery. [11]

Related Research Articles

The urea cycle (also known as the ornithine cycle) is a cycle of biochemical reactions that produces urea (NH2)2CO from ammonia (NH3). Animals that use this cycle, mainly amphibians and mammals, are called ureotelic.

<span class="mw-page-title-main">Arginine</span> Amino acid

Arginine is the amino acid with the formula (H2N)(HN)CN(H)(CH2)3CH(NH2)CO2H. The molecule features a guanidino group appended to a standard amino acid framework. At physiological pH, the carboxylic acid is deprotonated (−CO2) and both the amino and guanidino groups are protonated, resulting in a cation. Only the l-arginine (symbol Arg or R) enantiomer is found naturally. Arg residues are common components of proteins. It is encoded by the codons CGU, CGC, CGA, CGG, AGA, and AGG. The guanidine group in arginine is the precursor for the biosynthesis of nitric oxide. Like all amino acids, it is a white, water-soluble solid.

<span class="mw-page-title-main">Ornithine</span> Chemical compound

Ornithine is a non-proteinogenic α-amino acid that plays a role in the urea cycle. Ornithine is abnormally accumulated in the body in ornithine transcarbamylase deficiency. The radical is ornithyl.

<span class="mw-page-title-main">Ornithine transcarbamylase</span> Mammalian protein found in Homo sapiens

Ornithine transcarbamylase (OTC) is an enzyme that catalyzes the reaction between carbamoyl phosphate (CP) and ornithine (Orn) to form citrulline (Cit) and phosphate (Pi). There are two classes of OTC: anabolic and catabolic. This article focuses on anabolic OTC. Anabolic OTC facilitates the sixth step in the biosynthesis of the amino acid arginine in prokaryotes. In contrast, mammalian OTC plays an essential role in the urea cycle, the purpose of which is to capture toxic ammonia and transform it into urea, a less toxic nitrogen source, for excretion.

Propionic acidemia, also known as propionic aciduria or propionyl-CoA carboxylase deficiency, is a rare autosomal recessive metabolic disorder, classified as a branched-chain organic acidemia.

<span class="mw-page-title-main">Hyperammonemia</span> Medical condition

Hyperammonemia is a metabolic disturbance characterised by an excess of ammonia in the blood. It is a dangerous condition that may lead to brain injury and death. It may be primary or secondary.

<span class="mw-page-title-main">Ornithine transcarbamylase deficiency</span> Medical condition

Ornithine transcarbamylase deficiency also known as OTC deficiency is the most common urea cycle disorder in humans. Ornithine transcarbamylase, the defective enzyme in this disorder, is the final enzyme in the proximal portion of the urea cycle, responsible for converting carbamoyl phosphate and ornithine into citrulline. OTC deficiency is inherited in an X-linked recessive manner, meaning males are more commonly affected than females.

<span class="mw-page-title-main">Hartnup disease</span> Metabolic disorder

Hartnup disease is an autosomal recessive metabolic disorder affecting the absorption of nonpolar amino acids. Niacin is a precursor to nicotinamide, a necessary component of NAD+.

<span class="mw-page-title-main">Argininosuccinic aciduria</span> Medical condition

Argininosuccinic aciduria is an inherited disorder that causes the accumulation of argininosuccinic acid in the blood and urine. Some patients may also have an elevation of ammonia, a toxic chemical, which can affect the nervous system. Argininosuccinic aciduria may become evident in the first few days of life because of high blood ammonia, or later in life presenting with "sparse" or "brittle" hair, developmental delay, and tremors.

<span class="mw-page-title-main">Argininosuccinate lyase</span> Mammalian protein found in Homo sapiens

The enzyme argininosuccinate lyase (EC 4.3.2.1, ASL, argininosuccinase; systematic name 2-(N ω-L-arginino)succinate arginine-lyase (fumarate-forming)) catalyzes the reversible breakdown of argininosuccinate:

<span class="mw-page-title-main">Ornithine translocase deficiency</span> Medical condition

Ornithine translocase deficiency, also called hyperornithinemia-hyperammonemia-homocitrullinuria (HHH) syndrome, is a rare autosomal recessive urea cycle disorder affecting the enzyme ornithine translocase, which causes ammonia to accumulate in the blood, a condition called hyperammonemia.

<span class="mw-page-title-main">Aldolase B</span> Mammalian protein found in Homo sapiens

Aldolase B also known as fructose-bisphosphate aldolase B or liver-type aldolase is one of three isoenzymes of the class I fructose 1,6-bisphosphate aldolase enzyme, and plays a key role in both glycolysis and gluconeogenesis. The generic fructose 1,6-bisphosphate aldolase enzyme catalyzes the reversible cleavage of fructose 1,6-bisphosphate (FBP) into glyceraldehyde 3-phosphate and dihydroxyacetone phosphate (DHAP) as well as the reversible cleavage of fructose 1-phosphate (F1P) into glyceraldehyde and dihydroxyacetone phosphate. In mammals, aldolase B is preferentially expressed in the liver, while aldolase A is expressed in muscle and erythrocytes and aldolase C is expressed in the brain. Slight differences in isozyme structure result in different activities for the two substrate molecules: FBP and fructose 1-phosphate. Aldolase B exhibits no preference and thus catalyzes both reactions, while aldolases A and C prefer FBP.

<span class="mw-page-title-main">Y+L amino acid transporter 1</span> Protein-coding gene in the species Homo sapiens

Y+L amino acid transporter 1 is a protein that in humans is encoded by the SLC7A7 gene.

<span class="mw-page-title-main">Large neutral amino acids transporter small subunit 2</span> Protein-coding gene in the species Homo sapiens

Large neutral amino acids transporter small subunit 2 is a protein that in humans is encoded by the SLC7A8 gene.

<span class="mw-page-title-main">Aldehyde dehydrogenase 18 family, member A1</span> Protein-coding gene in the species Homo sapiens

Delta-1-pyrroline-5-carboxylate synthetase (P5CS) is an enzyme that in humans is encoded by the ALDH18A1 gene. This gene is a member of the aldehyde dehydrogenase family and encodes a bifunctional ATP- and NADPH-dependent mitochondrial enzyme with both gamma-glutamyl kinase and gamma-glutamyl phosphate reductase activities. The encoded protein catalyzes the reduction of glutamate to delta1-pyrroline-5-carboxylate, a critical step in the de novo biosynthesis of proline, ornithine and arginine. Mutations in this gene lead to hyperammonemia, hypoornithinemia, hypocitrullinemia, hypoargininemia and hypoprolinemia and may be associated with neurodegeneration, cataracts and connective tissue diseases. Alternatively spliced transcript variants, encoding different isoforms, have been described for this gene. As reported by Bruno Reversade and colleagues, ALDH18A1 deficiency or dominant-negative mutations in P5CS in humans causes a progeroid disease known as De Barsy Syndrome.

Transient hyperammonemia of the newborn (THAN) is an idiopathic disorder occasionally present in preterm newborns but not always symptomatic. Continuous dialysis or hemofiltration have proven to be the most effective treatment. Nutritional support and sodium benzoate have also been used to treat THAN.

<span class="mw-page-title-main">Ornithine aminotransferase deficiency</span> Medical condition

Ornithine aminotransferase deficiency is an inborn error of ornithine metabolism, caused by decreased activity of the enzyme ornithine aminotransferase. Biochemically, it can be detected by elevated levels of ornithine in the blood. Clinically, it presents initially with poor night vision, which slowly progresses to total blindness. It is believed to be inherited in an autosomal recessive manner. Approximately 200 known cases have been reported in the literature. The incidence is highest in Finland, estimated at 1:50,000.

<span class="mw-page-title-main">Homocitrulline</span> Chemical compound

L-Homocitrulline is an amino acid and can be detected in larger amounts in the urine of individuals with urea cycle disorders. At present, it is thought that the depletion of the ornithine supply causes the accumulation of carbamyl-phosphate in the urea cycle which may be responsible for the enhanced synthesis of homocitrulline and homoarginine. Both amino acids can be detected in urine. Amino acid analysis allows for the quantitative analysis of these amino acid metabolites in biological fluids such as urine or blood.

<span class="mw-page-title-main">Citrullinemia type I</span> Medical condition

Citrullinemia type I (CTLN1), also known as arginosuccinate synthetase deficiency, is a rare disease caused by a deficiency in argininosuccinate synthetase, an enzyme involved in excreting excess nitrogen from the body. There are mild and severe forms of the disease, which is one of the urea cycle disorders.

<span class="mw-page-title-main">Amino acid score</span> Method used to determine if a protein is complete

Amino acid score, in combination with protein digestibility, is the method used to determine if a protein is complete.

References

  1. Simell O, Perheentupa J, Rapola J, Visakorpi JK, Eskelin LE (August 1975). "Lysinuric protein intolerance" (Free full text). The American Journal of Medicine. 59 (2): 229–240. doi:10.1016/0002-9343(75)90358-7. PMID   1155480.
  2. Simell, O. (1990), "Lysinuric Protein Intolerance", Inborn Metabolic Diseases, Berlin, Heidelberg: Springer Berlin Heidelberg, pp. 577–583, doi:10.1007/978-3-662-02613-7_44, ISBN   978-3-662-02615-1 , retrieved 2024-07-22
  3. Simell, O. (1990), "Lysinuric Protein Intolerance", Inborn Metabolic Diseases, Berlin, Heidelberg: Springer Berlin Heidelberg, pp. 577–583, doi:10.1007/978-3-662-02613-7_44, ISBN   978-3-662-02615-1 , retrieved 2024-07-22
  4. Online Mendelian Inheritance in Man (OMIM): 222700
  5. Borsani G, Bassi MT, Sperandeo MP, et al. (March 1999). "SLC7A7, encoding a putative permease-related protein, is mutated in patients with lysinuric protein intolerance". Nat. Genet. 21 (3): 297–301. doi:10.1038/6815. PMID   10080183. S2CID   38960307.
  6. Borsani, Giuseppe; Bassi, Maria Teresa; Sperandeo, Maria Pia; Grandi, Alessandro De; Buoninconti, Anna; Riboni, Mirko; Manzoni, Marta; Incerti, Barbara; Pepe, Antonio; Andria, Generoso; Ballabio, Andrea; Sebastio, Gianfranco (March 1999). "SLC7A7, encoding a putative permease-related protein, is mutated in patients with lysinuric protein intolerance". Nature Genetics. 21 (3): 297–301. doi:10.1038/6815. ISSN   1061-4036. PMID   10080183.
  7. Douda, David N; Farmakovski, Nicole; Dell, Sharon; Grasemann, Hartmut; Palaniyar, Nades (December 2009). "SP-D counteracts GM-CSF-mediated increase of granuloma formation by alveolar macrophages in lysinuric protein intolerance". Orphanet Journal of Rare Diseases. 4 (1): 29. doi: 10.1186/1750-1172-4-29 . ISSN   1750-1172. PMC   2807424 . PMID   20030831.
  8. Sebastio, Gianfranco; Schiff, Manuel; de Baulny, Hélène Ogier (September 2016). "Lysinuric Protein Intolerance and Hartnup Disease". Oxford Medicine Online. doi:10.1093/med/9780199972135.003.0025.
  9. Sebastio, Gianfranco; Schiff, Manuel; de Baulny, Hélène Ogier (September 2016). "Lysinuric Protein Intolerance and Hartnup Disease". Oxford Medicine Online. doi:10.1093/med/9780199972135.003.0025.
  10. Tanner LM, Näntö-Salonen K, Niinikoski H, et al. (June 2007). "Nephropathy advancing to end-stage renal disease: a novel complication of lysinuric protein intolerance". J. Pediatr. 150 (6): 161–164. doi:10.1016/j.jpeds.2007.01.043. PMID   17517249.
  11. Tanner LM, Näntö-Salonen K, Niinikoski H, et al. (February 2006). "Hazards associated with pregnancies and deliveries in lysinuric protein intolerance". Metabolism. 55 (2): 224–231. doi:10.1016/j.metabol.2005.08.016. PMID   16423630.