L-Tryptophan: A Clue in Solving the Autism Puzzle

Autism is the third most common developmental disability. An estimated 1 in 68 kids has been diagnosed with autism, and their numbers are growing. Yet
its origins remain elusive. Consequently, so do effective treatments.

The science behind autism has been obscured by misinformation, misunderstanding of the disability itself, and the sheer complexity of autism research,
therapy, and treatment. Recently, scientists working in autism research have focused their studies on genetic links and biochemical disruptions that
impact brain development and brain function.

As part of that focus, researchers at the Greenwood Genetic Center (GGC), along with collaborators from Biolog, Inc. in California, found that people with
with autism spectrum disorders (ASDs) showed significantly decreased metabolism of the amino acid L-tryptophan when compared with control groups.

L-tryptophan is one of nine essential amino acids. These amino acids are called essential because they cannot be made by the human body but must be obtained
through diet.

Tryptophan is the precursor of key neurochemicals such as serotonin and melatonin, which help the body manage sleep, control moods, and even hold depression
at bay.

GGC’s scientists learned that cells from individuals with autism metabolized L-tryptophan at a decreased rate, while cells from individuals without autism
did not show this change.

Researchers also measured the expression of genes — the process by which genes produce the structure of a cell. Specifically, our researchers examined
those genes that are known to be involved in L-tryptophan metabolism in a small subset of patients with autism. They found these patients also expressed
some of the genes at lower levels than those without autism.

“The important and immediate implication of this work is the development of a simple, early blood-screening test for autism by measuring the metabolism of L-tryptophan using Biolog’s technology,” shared Dr. Luigi Boccuto, staff scientist at GGC.

Currently there are no laboratory tests that can accurately diagnose autism; therefore, diagnosis depends upon a developmental evaluation and parent interviews. This prolongs the diagnostic process, and it means that many children are not diagnosed until they are 2 or even 3 years old. The window to intervene early is nearly closed before a diagnosis is even made.

When Parker, Laura’s son, was 18 months old, she became seriously concerned about his development. “He had frequent tantrums because we couldn’t communicate, even through pointing, and we couldn’t understand what he needed. It was like playing a constant never-ending game of charades, she said. “Parker’s diagnosis was a long, drawn-out journey.” Within six months, Laura knew the likely diagnosis, but it took another two years to get in to see a developmental pediatrician and start the initial testing. The testing itself was a six-month process.

“A screening, and eventually, a diagnostic blood test for autism would be of immense value to families,” explained Dr. Charles Schwartz, director of research at Greenwood Genetic Center and lead investigator. “An early, accurate diagnosis is key to providing effective and timely therapies for these patients and their families.”

Dr. Boccuto added, “We also see tremendous potential that these findings will aid in our understanding of the … bases of autism. Once we have a clear vision of what has gone awry within the tryptophan metabolism pathways, we can develop therapies to target and correct those problems at the research at Greenwood Genetic Center and lead investigator. “An early, accurate diagnosis is key to providing effective and timely therapies for these patients and their families.”