Last year's Top 10 featured a report on regression in children with both autism and mitochondrial disorder. This year has had its share of mitochondria in the news as well, especially recently with Cecilia Giulivi, Ph.D. and colleagues reporting in the Journal of the American Medical Association (JAMA) a greater incidence of mitochondrial dysfunction in young children with autism.
Mitochondria are the cells' main provider of fuel. With the tens of billions of neurons in the brain, each actively receiving electrical signals and converting them to chemical messages to pass along to neighboring neurons, the brain is a very energetically expensive organ. Although there are hints in previous research that autism is associated with abnormal energy metabolism in autism, studies of mitochondrial dysfunction in autism are still relatively few. One challenge is that the gold standard method of assessing mitochondrial function involves an invasive muscle biopsy. Dr. Giulivi wanted to test whether mitochondrial dysfunction could be tested using a much less invasive method.
Giulivi and colleagues used blood samples from children aged 2-5 years old with autism who were enrolled in the CHARGE study. Mitochondria aren't typically obtained from blood samples because it was believed that there weren't enough to analyze – there are no mitochondria in red blood cells. However the white blood cells, specifically lymphocytes, do have reasonable quantities of mitochondria. Giulivi developed methods for isolating these mitochondria and measuring the function of the enzyme chain that convert nutrients into energy.
The researchers found evidence of mitochondrial dysfunction in the enzyme chain in 8 of the 10 children with autism but none of the typically-developing children. Mitochondrial DNA mutations were also observed in the children with autism. Curious at first blush, the children with autism appeared to have more copies of mitochondrial DNA. This makes sense if each individual mitochondrion is functioning imperfectly and so more are needed to fill the energy demands of the cells.
The advantage of identifying mitochondrial dysfunction is that there are ways to support better function. Through diet, exercise and in some cases, supplements, individuals with mitochondrial dysfunction can improve significantly (see the United Mitochondrial Disease Foundation for more information). We look forward to next year to see how this research develops.