Utilisation of amino acid mixtures in adolescents with phenylketonuria

Abstract

The nutritional regimen of patients with phenylketonuria (PKU) comprises a diet of natural proteins and phenylalanine (Phe)-free amino acid (AA) mixture. The main daily protein requirement is covered by a Phe-free AA mixture. In an adult with PKU, the consumption of the daily AA requirement in one single dose at breakfast caused nausea and vomiting. Therefore, four studies were designed to investigate the adverse and metabolic effects resulting from large intakes of AA mixtures used in the treatment of PKU patients with respect to the following: (1) biochemical effects following consumption of one single dose of Phe-free AA mixture in healthy persons; (2) transient metabolic changes caused by different individual regimens of AA intake in healthy persons and in one PKU patient; (3) nitrogen excretion in PKU patients taking the AA mixture in two or three portions; and (4) catabolic metabolism of AA in a PKU patient. In healthy subjects following the ingestion of the AA mixture in one bolus there was an increase in the blood levels of the given AA and also an increase in blood insulin concentration and a decrease in blood glucose concentration. These changes were less marked when the AA mixture was divided into three portions per day. In contrast, in a PKU patient following the ingestion of AA there was an increase in blood glucose. The urinary nitrogen excretion was greater in PKU patients when one compared to three portions of AA mixture was taken. The consumption of the daily requirement of AA mixture in one single does produced increased catabolism in a PKU patient. In conclusion it is recommended that the total daily amount of AA mixture should be divided into a minimum of three portions.

Large neutral amino acids block phenylalanine transport into brain tissue in patients with phenylketonuria

“…Recently, the metabolic effects resulting from large intakes of AA mixtures have been reported (46). The recommended daily amount of ∼1.6/kg body weight AA mixture was given in a single dose to control subjects, leading to a substantial increase of AAs.…”

Endocrine Effects of Food Intake: Insulin, Ghrelin, and Leptin Responses to a Single Bolus of Essential Amino Acids in Humans

“…In the literature there are contradictory data concerning AA kinetics due to the different settings, forms of administration and dosages. It has been reported that the highest blood AA after ingesting a whole meal are found 3-5 h after the meal [20] or even 1 h following the consumption of an AA mixture [18].…”

“…Dur- ing our study, blood glucose concentrations remained within the normal range over a period of 5 h, so excluding acutely impaired glucose tolerance. Higher doses of AA (1.5 g/kg BW) may even lead to a decrease in blood glucose concentration in healthy individuals [18].…”

Importância do diagnóstico e tratamento da fenilcetonúria

“…55,59 Por falta de maiores estudos, os requerimentos protéicos para os fenilcetonúricos seguem as recomendações propostas pela FAO/WHO, 19,55,60 considerando-se a necessidade de ingestão de proteína igual à de indivíduos sadios.…”

“…12,70 O consumo diário dos aminoácidos requeridos, em dose única, pode resultar em náuseas, vômitos, tonturas e diarréia, mudanças na excreção de nitrogênio e metabolismo catabólico, diminuindo as taxas de glicose e lactato e aumentando os níveis de insulina no sangue. 55 As misturas de aminoácidos sintéticos também são indesejáveis do ponto de vista do equilíbrio osmótico, pois causam hiperosmolaridade no trato gastrointestinal, resultando em absorção ineficiente pelo organismo.…”