Glutamine, ornithine, citrulline and arginine levels in children with phenylketonuria: The diet effect

Phenylketonuria (PKU) therapeutic diet is characterized by the great replacement of natural protein with a phenylalanine-free formula.To investigate the effect of diet on the amino acid serum levels in PKU patients and their total antioxidant status (TAS).Thirty-seven poorly controlled patients (group A), 43 patients who strictly adhered to their diet (group B) and 50 controls were included in the study. In patients and controls blood chemistry, TAS and serum amino acid level determinations were performed.Phenylalanine levels significantly differed among the groups. Glutamine and ornithine levels were significantly higher in group A, while TAS (416±30 vs 228±23μmol/L, p<0.001), citrulline (39±15 vs 26±5μmol/L, p<0.001) and arginine levels (61±11 vs 80±12μmol/L, p<0.001) were higher in group B. The other determined amino acid serum levels did not differ among the groups of patients and controls.The high glutamine and ornithine levels in group A may reflect the high natural protein intake. High phenylalanine levels in these patients may locally affect the hepatocyte, enterocyte, and/or renal function resulting in low citrulline and arginine levels contributing to their low TAS.