Hyperphenylalaninaemia and outcome in intravenously fed preterm neonates.

Phenylalanine and Tyrosine Kinetics in Critically Ill Children with Sepsis

“…Also, the hydroxylation of phenylalanine, expressed either as an absolute rate or as a percentage of the phenylalanine flux, was higher in our patients than was phenylalanine hydroxylation in newborn infants as reported by Denne with sepsis, suggesting a n increased rate of muscle breakdown, reduced rate of incorporation of phenylalanine into muscle proteins, and/or a n alteration in the rate of hepatic conversion of phenylalanine to tyrosine (26,27,35,36). Also, during protein deficiency, phenylalanine use decreases, leading to a relative increase in the plasma phenylalanine level, which again is possibly due to a decreased enzymatic conversion of phcnylalanine to tyrosine (37,38). Of course, the low content of tyrosine in the parenteral amino acid mixture would also be expected to raise the plasma-free phenylalanine/tyrosine ratio, although the ratio was also high in the two patients (patients 4 and 9) who were receiving glucose alone.…”

Effect of Hyperalimentation and Insulin‐Treated Hyperglycemia on Tyrosine Levels in Very Preterm Infants Receiving Parenteral Nutrition

“…Vamin 9 (Kabi Pharmacia, Uppsala, Sweden) had phenylalanine concentrations (7.8 g/100 g AA) higher than human milk (4.1 g/100 g AA), causing both hyperphenylalaninemia and hypertyrosinemia in the first week of life 8 . It is of some reassurance that 18‐month follow‐up of infants exposed to phenylalininemia did not identify any neurodevelopmental impairment 38 . Hypertyrosinemia occurred despite low PN tyrosine concentrations (0.7 g/100 g AA) compared with human milk (3.9 g/100 g AA) 39 and indicates adequate phe‐nylalanine hydroxylase activity.…”

Low plasma taurine and later neurodevelopment

“…Neonatal plasma taurine concentrations, 5 Bayley Scales of Infant Development (corrected for gestational age) at 18 months of age, and the Wechsler Intelligence Scale for Children-revised (WISC-R) at 7 years were available in 157 children (mean (SD) birth weight, 1398 (277) g; gestation, 31 (2.4) weeks). The lowest (minimum) plasma taurine concentration during their hospital stay was obtained for each subject.…”