Objectives: The objectives of this study were to determine if Phenex-1, ami
no-acid modified medical food with iron maintained normal indices of protei
n status in infants with phenylketonuria (PKU) and to investigate factors t
hat influence plasma amino acid concentrations.
Methods: A study was conducted for six months in 35 infants with classical
PKU diagnosed in the neonatal period. Diet diaries and plasma amino acid co
ncentrations were obtained monthly. Blood for analysis of plasma albumin. b
lood urea nitrogen (BUN), retinol binding protein (RBP) and transthyretin w
as obtained at one, three and six months of study.
Results: Mean (+/-SEM) total daily intake of medical food and nutrients was
79 +/- 4 g: 17.3 +/- 0.6 g protein, 660 +/- 18 kcal. 255 +/- 10 mg phenyla
lanine (Phe), and 1423 +/- 56 mg tyrosine (Tyr). Mean concentrations of pla
sma amino acids, except cystine (during entire study), glycine (first month
) and Phe were in the normal range. Mean concentrations of plasma Phe were
in the treatment range (120 to 360 mu mol/L). Plasma concentrations of argi
nine, methionine, Phe, tryptophan, Tyr, and valine were positively correlat
ed with intakes at various months of study.Concentrations of aspartic and g
lutamic acids, Phe, and Tyr were positively correlated and 17 amino acids w
ere negatively correlated with the interval between feeding and blood draw.
At six months of study, concentration of plasma albumin was 4.1 +/- 0.1 g/
dL, REP was 3.74 +/- 0.2 mg/dL, transthyretin was 17.9 +/- 0.9 mg/dL, and u
rea nitrogen was 11.9 +/- 0.5 mg/dL.
Conclusion: During study, all mean plasma indices of protein status were in
normal reference ranges. Phenex-1 supports normal mean plasma amino acid,
albumin, REP, transthyretin, and BUN concentrations when fed in adequate am