GAINESVILLE _Findings from two animal studies indicate autism and
schizophrenia may be linked to a person's inability to properly break down
a protein found in milk, University of Florida (UF) researchers report in
this month's issue of the journal Autism.
The digestive problem might actually lead to the disorders' symptoms,
whose basis has long been debated, said UF physiologist Dr. J. Robert
Cade, cautioning that further research must take place before scientists
have a definitive answer.
When not broken down, the milk protein produces exorphins,
morphine-like compounds that are then taken up by areas of the brain known
to be involved in autism and schizophrenia, where they cause cells to
dysfunction.
The animal findings suggest an intestinal flaw, such as a
malfunctioning enzyme, is to blame, says Cade, whose team also is putting
the theory to the test in humans.
Preliminary findings from that study which showed 95 percent of 81
autistic and schizophrenic children studied had 100 times the normal
levels of the milk protein in their blood and urine have been presented at
two international meetings in the past year but have not yet been
published.
When these children were put on a milk-free diet, at least eight out of
10 no longer had symptoms of autism or schizophrenia, says Cade, a
professor of medicine and physiology at UF's College of Medicine and
inventor of the Gatorade sports drink.
His research team includes research scientist Dr. Zhongjie Sun and
research associate R. Malcolm Privette.
"We now have proof positive that these proteins are getting into the
blood and proof positive they're getting into areas of the brain involved
with the symptoms of autism and schizophrenia." Cade said.
More than 500,000 Americans have some form of autism, according to the
Autism Society of America.
The developmental disability typically appears during the first three
years of life and is characterized by problems interacting and
communicating with others. Many individuals exhibit repeated body
movements such as hand flapping or rocking and may resist changes in
routine. In some cases, they may display aggressive or self-injurious
behavior.
Schizophrenia is noted for disturbances in thinking, emotional reaction
and behavior and is the most common form of psychotic illness.
More than 2 million Americans suffer from it, according to the National
Institute of Mental Health. People with schizophrenia often hear internal
voices not heard by others, or believe
others are reading their minds, controlling their thoughts or plotting to
harm them. In addition, their speech and behavior can be so disorganized
that they may be incomprehensible or frightening to others.
In the UF studies, researchers injected rats with the protein
beta-casomorphin-7, one of the key constituents of milk and the part that
coagulates to make cheese. They then observed their behavior and later
examined brain tissue to see whether the substances accumulated there.
Beta-casomorphin-7 was taken up by 32 different areas of the brain,
Cade said, including sections responsible for vision, hearing and
communication.
"This could explain several of the things one sees in autism and
schizophrenia, such as hallucinations," he said and added: "If part of
the brain puts out a false signal because of casomorphin, it could result
in the person seeing something that's not really there; either a visual or
auditory hallucination could occur."
"There are a whole number of behaviors that the rat has after
beta-casomorphin-8 that are basically the same as one sees in the human
with autism or schizophrenia," he went on. If we
ring a bell beside a rat's cage, it normally looks up to see where the
noise is coming from. But the rats after beta-casomorphin-7 didn't do that
--they were completely oblivious to the
bell-ringing above them. "This struck us as interesting because many
mothers of autistic children comment that they seem at times to be
totally deaf --they talk to their children and they just don't seem to
hear them." Researchers suspect the process begins in the intestine,
where the body absorbs the protein when a person eats foods containing it.
"We think this process is linked to the production of antibodies in the
gut when you eat something you're sensitive to," Cade said. "Both
schizophrenics and autistics have a high incidence of certain
antibodies, and a high incidence of diarrhea, which points to an
intestinal disorder."
So we think that with autism and schizophrenia, the basic
disorder is in the intestine, and these individuals are absorbing
beta-casomorphin-7 that they normally should break down in the body as
amino acids, rather than peptide chains up to 12 amino acids long."
Dr. Bennett L. Leventhal, professor of psychiatry and pediatrics and
director of child adolescent psychiatry at the University of Chicago
School of Medicine, said other studies exploring a dietary link to autism
or schizophrenia have been less than convincing, and the notion has not
generally been accepted in the field.
"Autism and schizophrenia certainly are distinctly different
disorders," Leventhal said. "I think the best hypothesis sitting out there
today is that some genetic abnormality is causing these disorders." It
is certainly possible that these genetic
abnormalities could lead to the metabolic effects Dr. Cade
mentions, though there is not substantial support for that at this time.
"With autism in particular, there are three or four genes that have
sparked interest," he added. "The assumption is that it is not a single
gene disorder but rather a polygenic disorder.
"Given that, it means not only does one have to figure out what the
genes are but also what they do and their relative contribution to the
symptoms of the disorder."
"This is not unusual -- the vast majority of medical conditions for
which there is genetic substantiation are complex disorders. Single gene
disorders are relatively rare."
March 16, 1999
Copyright 1999 by publishers involved.
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