Abstract
Amino acid determinations in plasma have been used for diagnostic purposes and as markers of malnutrition since the 1960s. Biochemical research has given an insight into biochemical pathways and their organ specificity, allowing better understanding of the role of amino acids in the organism. In nutrition, amino acid concentrations are used as markers of excess, deficiency or imbalance for optimising the amount and composition of proteins in prepared nutrients. For useful results to be obtained in such investigations correct timing of sampling relative to the end of food intake is essential. Using data from a study in which a reduction of protein to 1.9 g/100 kcal in starter formulas was tested, it is shown that not only does this allow amino acid concentrations quite close to those of breast-fed babies to be achieved; in addition, the levels reached with the optimised composition lead to a balance with less competition from large neutral amino acids with tryptophan transport at the blood-brain barrier (LAT1 transporter), which probably enhances the supply to the brain even when less protein is fed than in conventional formula and when there is no increase of tryptophan in the blood.
Zusammenfassung
Aminosäurenbestimmungen im Plasma werden seit den 1960ern für diagnostische Zwecke eingesetzt. Untersuchungen der biochemischen Stoffwechselwege und deren Organspezifität führten zu einem immer besseren Verständnis der Rolle der Aminosäuren im Organismus. Aminosäurenkonzentrationsbestimmungen werden benutzt, um eine Über-, Unter- oder nicht balancierte Versorgung zu erkennen und den Gehalt und die Zusammensetzung von Proteinen in Nahrungsmitteln zu optimieren. Um verwertbare Ergebnisse zu erhalten, muss der Blutentnahmezeitpunkt in Abhängigkeit von der Nahrungsaufnahme korrekt gewählt werden. Die Daten einer Untersuchung, in welcher Neugeborenen eine Milch mit reduziertem Proteingehalt (1,9 g/100 kcal), aber optimierter Zusammensetzung gegeben wurde, werden dargestellt. Mit dieser Milch ernährte Kinder zeigten gestillten Kindern vergleichbare Blutaminosäurewerte. Zudem wurde erreicht, dass die Kompetition großer neutraler Aminosäuren mit Tryptophan am Transporter der Blut-Hirn-Schranke (LAT1-Transporter) geringer war, was möglicherweise die Tryptophanversorgung des Gehirns optimierte, obwohl weniger Protein verabreicht wurde als mit konventionellen Nahrungen und obwohl keine Zunahme des Bluttryptophangehalts vorlag.
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Bachmann, C. Plasma amino acids as substrates and nutrition-dependent markers. Monatsschr Kinderheilkd 151 (Suppl 1), S72–S77 (2003). https://doi.org/10.1007/s00112-003-0793-z
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DOI: https://doi.org/10.1007/s00112-003-0793-z