What is mitochondrial disease? How often does it occur in individuals with ASD? Are their effective treatments?
“Got Questions?” is a new weekly feature on our blog to address the desire for scientific understanding in our community. We received over 3000 responses when we asked what science questions were on your mind. We answered a few here and the Autism Speaks Science staff will address the other themes we received in this weekly post.
Mitochondrial disease is caused by an error in the functioning of mitochondria, which are essential energy-producing compartments of nearly every cell in the body. Certain mutations can cause the mitochondria to function inefficiently. These mutations can be within the mitochondria itself, with its own small circle of DNA, or within the nucleus where the rest of the cell’s DNA resides. Over 1500 genes carry some part of the recipe for the optimal functioning of mitochondria. This means that there are many ways for mitochondria to function imperfectly but there are also complex means available to mask a deficit by altering some of the other protein interactions.
Mitochondria are responsible for the process of oxidative phosphorylation that turns nutrients into energy through a series of stages involving complexes of enzymes. A break at any particular stage results in an atypical balance of metabolites in affected body tissues and fluids.
Most people consider mitochondrial disease to be one of a growing number of disorders caused by a defined set of mutations and presenting with a set of characteristics that typically involve three or more organ systems. However, mitochondrial disorders are often diagnosed when no mutation is found despite observations of metabolic signatures of mitochondrial dysfunction. The symptoms may also be more mild.
We do not have a firm estimate of mitochondrial disease in ASD. However, if we use the broader definition of mitochondrial disorder then according to a population-based study in Portugal, there may be as many as 4% of the ASD population affected. Autism Speaks’ research is addressing this and related questions through a grant to Cecilia Giulivi, Ph.D. at UC Davis and also through a collaborative research project at UC Irvine and UC San Diego.
There is currently no cure for mitochondrial disease or disorder. There are, however, treatments and practices that can improve the quality of life and slow the progression of the disease. The most effective treatments are for specific symptoms that tend to accompany mitochondrial dysfunction such as seizures treated with anti-convulsants. Regular exercise, a healthy diet, stress and extreme temperature avoidance are among the common recommendations. Some dietary and supplement regimes have anecdotal support but there is a need for empirical studies to test the efficacy of these therapies.
For more information, please visit the United Mitochondrial Disease Foundation (UMDF) website. Also, read our report on a joint Autism Speaks’ supported symposium at the annual UMDF meeting.