Valine, isoleucine, and leucine. A new treatment for phenylketonuria
H. K. Berry, R. L. Brunner, M. M. Hunt and P. P. White
Metabolic Disease Center, Children's Hospital Medical Center, Cincinnati, OH 45229.
Early treatment of phenylketonuria by dietary phenylalanine restriction
prevents brain damage. Behavioral and cognitive deficits occur when serum
phenylalanine levels increase. Administration of valine, isoleucine, and
leucine to patients with phenylketonuria may inhibit entry of phenylalanine
into the brain and reduce its toxic effects on the central nervous system.
Sixteen adolescents and young adults with phenylketonuria participated in
double-blind trials in which a valine, isoleucine, and leucine mixture or a
control mixture was given for four 3-month periods. Biochemical and
neuropsychologic tests were carried out before and at the end of each
period. Time to completion of a test that required substantial attention
with mental processing (Attention Diagnostic Method) was faster during the
valine, isoleucine, and leucine periods than during the control mixture
periods. Improvement with valine, isoleucine, and leucine on a less
demanding task (Continuous Performance Test) approached significance. These
data lent support to the hypothesis that a regimen of valine, isoleucine,
and leucine may help individuals unable to maintain low serum phenylalanine
levels.
