Mitochondrial Powerhouses May Be Compromised in Autistic Children, New Study Suggests

A recent study has uncovered evidence of mitochondrial abnormalities in young children diagnosed with autism. Researchers at the University of California-Davis observed impaired mitochondrial function across several tests when comparing a small group of autistic children to their neurotypical peers. While the findings are preliminary, they add to a growing body of research exploring the role of cellular energy production in autism spectrum disorder.

Key Takeaways

• Children with autism showed signs of impaired mitochondrial function compared to healthy controls.
• Specific abnormalities included reduced enzyme activity, altered DNA copy numbers, and increased hydrogen peroxide production in mitochondria.
• Researchers emphasize that it is currently unclear whether these mitochondrial issues are a cause or a consequence of autism.

Unveiling Mitochondrial Dysfunction

The study, published in the Journal of the American Medical Association (JAMA), involved 10 children aged 2 to 5 with autism and 10 age-matched healthy controls. The participants were drawn from a larger cohort previously involved in the Childhood Autism Risk from Genetics and the Environment (CHARGE) Study. Researchers collected plasma and cellular samples, specifically lymphocytes and granulocytes, to analyze mitochondrial DNA and function.

Specific Findings in Autistic Children

Several key differences were noted in the mitochondria of children with autism:

• Reduced Enzyme Activity: Nicotinamide adenine dinucleotide oxidase activity was significantly lower in autistic children.
• Mitochondrial DNA Overreplication: Half of the children with autism exhibited mtDNA overreplication, leading to a higher mean copy number compared to controls.
• Complex I Deficiency: Six out of ten autistic children showed lower complex I activity.
• Pyruvate Metabolism: Autistic children had higher plasma pyruvate levels and significantly lower pyruvate dehydrogenase complex (PDHC) activity, suggesting issues with energy metabolism.
• Oxidative Stress: Mitochondria from autistic samples demonstrated higher rates of hydrogen peroxide production, indicating increased oxidative stress.

Cause or Consequence?

Lead researcher Cecilia Giulivi, PhD, a professor at UC-Davis, stressed that the study cannot definitively determine if these mitochondrial abnormalities are a cause or an effect of autism. However, she noted that altered energy metabolism could potentially influence the social and cognitive deficits associated with the disorder. Given the brain's high energy demands, mitochondrial dysfunction could amplify existing brain dysfunction.

Expert Perspectives

Experts in the field acknowledge the study's findings but also highlight the small sample size. Salvatore DiMauro, MD, from Columbia University Medical Center, commented that mitochondrial dysfunction in autism has been discussed for years. Richard Kelley, MD, PhD, from Johns Hopkins Medical Institutions, noted similar findings in his own research, particularly regarding complex I deficiency. He suggested that children might be born with mild mitochondrial abnormalities that become problematic when the system is stressed by environmental factors like infection or inflammation.

Future Directions

Dr. Giulivi and her team plan to expand their research with larger, longitudinal studies to better understand the origins of mitochondrial dysfunction in autism. They are also investigating how early these abnormalities occur and how they might alter the development of brain circuits involved in autism spectrum disorders. The researchers are considering a combination of genetic and environmental factors as potential contributors.

Sources

• Mitochondrial Dysfunction Identified in Autistic Children, Neurology Today.