H. Dotremont et al., NUTRITIONAL-VALUE OF ESSENTIAL AMINO-ACIDS IN THE TREATMENT OF ADULTSWITH PHENYLKETONURIA, Journal of inherited metabolic disease, 18(2), 1995, pp. 127-130
Phenylketonuria (PKU; McKusick 261600) is an inherited metabolic disor
der caused by a deficiency of phenylalanine hydroxylase. Hyperphenylal
aninaemia results in progressive mental deterioration, unless treatmen
t with dietary phenylalanine (phe) restriction starts before 6 weeks o
f age (Scriver et al 1989). Since termination of the treatment leads t
o a deterioration of the intellectual and neurophysiological functions
, a 'diet for life' is recommended (Michals et al 1990). The recogniti
on that phe and other large neutral amino acids (LNAA) share common re
ceptor sites on a blood-brain barrier transport system (Oldendorf 1973
) led to the hypothesis that the administration of those LNAA to PKU p
atients may reduce the amount of phe reaching the brain and prevent so
me of its toxic effects on the central nervous system. Short- and long
-term trials conducted in animals and humans showed that motor and cog
nitive functions improved with the addition of branched-chain amino ac
ids to the low-phe diet (Berry et al 1990). However, little is known a
bout the bioavailability and the nutritional value of this essential a
mino acids mixture. To determine whether adult PKU patients who refuse
to continue taking their classical amino acids mixture may replace it
by LNAA, a nitrogen (N) balance was conducted in four PKU patients.