title: Dietary protein in urea cycle defects: How much? Which? How?
abstract: Dietary recommendations for patients with urea cycle disorders (UCDs) are designed to prevent metabolic decompensation (primarily hyperammonaemia), and to enable normal growth. They are based on the 'recommended daily intake' guidelines, on theoretical considerations and on local experience. A retrospective dietary review of 28 patients with UCDs in good metabolic control, at different ages, indicates that most patients can tolerate a natural protein intake that is compatible with metabolic stability and good growth. However, protein aversion presents a problem in many patients, leading to poor compliance with the prescribed daily protein intake. These patients are at risk of chronic protein deficiency. Failing to recognise this risk, and further restricting protein intake because of persistent hyperammonaemia may aggravate the deficiency and potentially lead to episodes of metabolic decompensation for which no clear cause is found. These patients may need on-going supplementation with essential amino acids (EAA) to prevent protein malnutrition. Current recommendations for the management of acute metabolic decompensation include cessation of protein intake whilst increasing energy (calorie) intake in the first 24h. We have found that plasma concentrations of all EAA are low at the time of admission to hospital for metabolic decompensation, with correlation between low EAA concentrations, particularly branched-chain amino acids, and hyperammonaemia. Thus, supplementation with EAA should be considered at times of metabolic decompensation. Finally, it would be advantageous to treat patients in metabolic decompensation through enteral supplementation, whenever possible, because of the contribution of the splanchnic (portal-drained viscera) system to protein retention and metabolism.
authors.affiliation: Murdoch Childrens Research Institute, Victorian Clinical Genetics Services, Royal Children's Hospital, Flemington Road, Parkville, Melbourne, Australia; Department of Paediatrics, University of Melbourne, Melbourne, VIC, Australia.
authors.forename: Avihu
authors.initials: A
authors.lastname: Boneh
mesh_terms: D000597:Amino Acids, Branched-Chain / Q000097:blood; D000601:Amino Acids, Essential / Q000097:blood; D004032:Diet; D004044:Dietary Proteins / Q000627:therapeutic use*; D005247:Feeding Behavior; D006801:Humans; D017410:Practice Guidelines as Topic; D056806:Urea Cycle Disorders, Inborn / Q000178:diet therapy* / Q000378:metabolism*
chemical_list: D000597:Amino Acids, Branched-Chain; D000601:Amino Acids, Essential; D004044:Dietary Proteins
keywords: Catabolism; Energy; Low protein diet; Recommended daily intake; Urea cycle