Nov. 30, 2010 -- New research linking impaired mitochondrial function to autism appears to support the notion that the cellular irregularity plays a role in the disorder in at least a subset of patients.
Known as the power plant of the cell, mitochondria are critical for converting nutrients into energy. Mitochondrial dysfunction can occur from birth or later in life and may involve no symptoms or a wide range of symptoms including developmental delays, problems with the heart, and muscle weakness.
In the new study, researchers found that children with autism were more likely than children without the disorder to have impaired mitochondrial function and mitochondrial DNA abnormalities.
The study was small, including just 10 children with autism and 10 typically developing children. And just one of the autistic children in the study actually had mitochondrial disease.
But researchers say the early findings suggest mitochondrial dysfunction and altered energy metabolism could contribute to the development or progression of autism in some children.
Little is known about the causes of autism, although most experts now believe that both genetic and environmental factors contribute to it.
The study appears in the Dec. 1 issue of TheJournal of the American Medical Association.
“Certainly, these findings need to be confirmed in larger studies,” study researcher Cecilia Giulivi, PhD, of the University of California, Davis tells WebMD. “More research is also needed to understand how mitochondrial dysfunction might contribute to autism.”
Markers for Impaired Mitochondrial Function
Giulivi and colleagues took blood samples taken from the 20 children to look for markers consistent with impaired mitochondrial function.
This represents a big advance over earlier studies, which relied on far more invasive muscle biopsies to look for evidence of the cellular dysfunction, says Geraldine Dawson, PhD, who is the chief science officer for the advocacy and research group Autism Speaks.
Based on their findings and those of earlier studies, the researchers concluded that the incidence of mitochondrial disease may be 550 to 770 times higher in autistic children than in the general population.
But it is not yet clear if mitochondrial dysfunction causes autism or if it is a consequence of the developmental disorder, Dawson says.
“These findings point to the need for more research to better understand the role of mitochondrial dysfunction in autism,” she says.
Implications for Autism Treatment
Giulivi says the research could potentially lead to blood tests to screen babies for autism long before behavioral symptoms of the disorder become evident.
But Dawson says it is more likely the blood screening will be useful in children who are already diagnosed with autism.
“If we know that a child with autism has mitochondrial dysfunction, this could have implications for treatment,” she says.
“We have learned that autism is associated with other medical conditions including GI [gastrointestinal] and sleep problems and seizures,” she says. “And we have learned that if we address some of these conditions we may be able to improve the autism. Mitochondrial dysfunction may be one of these conditions.”
Mitochondrial dysfunction became front and center in the debate about whether vaccines cause autism with the case of now 11-year-old Hannah Poling, whose parents said her autism symptoms began within days of receiving five routine inoculations for nine diseases in July of 2000.
They claimed that Hannah’s then undiagnosed mitochondrial disease put her at increased risk for injury from the vaccines, and in the spring of 2008 federal officials agreed, ruling that the family was entitled to payments from a fund set up to compensate people injured by immunizations.
Dawson says vaccination is usually indicated in children with known mitochondrial diseases.
“Anytime there is a challenge to the immune system there is vulnerability in these children,” she says. “Children who don’t get vaccinated are more susceptible to infections which challenge the immune system.”