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Autism Discovery Paves Way for Early Blood Test

Researchers focus on L-tryptophan metabolism (June 5)

Researchers at the Greenwood Genetic Center in Greenwood, South Carolina, have reported an important discovery in the understanding of autism, which was published in Molecular Autism.

The study found that individuals with autism spectrum disorders (ASDs) showed significantly decreased metabolism of the amino acid L-tryptophan when compared with both typical controls and individuals with other neurodevelopmental disorders. Cells from individuals with autism metabolized L-tryptophan at a decreased rate, whereas cells from individuals without autism did not show this change.

The researchers also measured the expression of genes that are known to be involved in L-tryptophan metabolism in a small subset of patients with autism and found that these patients also expressed some of the genes at lower levels than did those without autism.

According to staff scientist Luigi Boccuto, MD, 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. An assay method, called the Phenotype MicroArray, allows researchers to measure the ability of cells to generate energy from various biochemical nutrients, including L-tryptophan.

Currently, no laboratory tests can accurately diagnose ASDs, which are estimated to affect 1 in 50 school-aged children in the U.S. Current diagnosis of the disorder depends on a developmental evaluation and on parent interviews, and often cannot be made before the age of 2 to 3 years.

Boccuto added: “We also see tremendous potential that these findings will aid in our understanding of the molecular and metabolic 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 biochemical level.”

L-tryptophan is one of twenty amino acids used by cells to make protein. It is one of eight amino acids that cannot be made by the body, so it must be obtained from the diet. More important, L-tryptophan plays an important role in brain development and function as it is the precursor of key neurochemicals, such as serotonin and melatonin, which have already been linked to behavioral and neurodevelopmental problems.

Source: Greenwood Genetic Center; June 5, 2013.

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