What is Autism?
Autism is a developmental disorder that appears in the first years of life and affects the brain’s normal development of social and communication skills. Autism Spectrum Disorder (ASD) encompasses a range of symptoms, from mild to severe. ASD most likely has many different causes rather than resulting from any single disease process.
What is the role of mitochondrial dysfunction in ASD?
All ASD is not mitochondrial disease. However, mitochondrial dysfunction has been found repeatedly to be prevalent in this group of children and adults. The brain and muscles require a tremendous amount of energy to function normally. Deficiencies in the ability to fuel brain neurons – as may occur with mitochondrial dysfunction – could lead to some of the symptoms of Autism.
Because mitochondria make ATP, as well as perform vital cellular tasks, mitochondrial dysfunction can result in less energy available to fuel the high-energy needs of the brain and muscles, and also leave free radicals in the system where they can cause damage. Overall, there is a large and growing body of research showing that individuals with ASD often have significant mitochondrial dysfunction, which may be a cause of, or contributing factor to, their development disorder.
More attention has recently been focused on a potential link between Autism Spectrum Disorders (ASD) and dysfunctional mitochondria. A study published in 2009 in the Journal of Child Neurology further examined this link (Shoffner, JE et al, J Child Neurol. 2010 Apr;25(4):429-34; Epub 2009 Sep 22), finding that a subgroup of patients with mitochondria disorders may be at increased risk for autistic regression, especially around periods of fever.
Mitochondria are intimately tuned to the environment in which they reside and are built to respond quickly to fluctuations in the state of that environment. To characterize a relationship between mitochondria disorders and ASD, researchers from Atlanta identified a group of 28 children who had been diagnosed with both ASD and mitochondrial disease. (Shoffner, JE et al, J Child Neurol. 2010 Apr;25(4):429-34; Epub 2009 Sep 22). The most common clinical observation in children with both ASD and mitochondria disorder was hypotonia, or muscles with low tone, followed closely by “fatigue with activity.” They also found that approximately 60 percent (17 of 28) of these children experienced a regressive form of ASD, a rate of regression that is over two times greater than what is observed in the general population of individuals with ASD.
Notably, 12 of those 17 regressions occurred in conjunction with having suffered a fever within a two week period of the regression. However, this regression did not appear to be necessarily linked to vaccinations, as two-thirds of the children that regressed with fever had not received vaccination, and of those who did receive a vaccination, none regressed without also having a fever.
Although a small study, this mitochondrial research illuminates potentially useful new commonalities between children with both an ASD and mitochondria disorder, suggesting that children with mitochondrial disease may be at increased risk for autistic regression and that increased risk may be associated with some fever-response pathway. Although this mitochondrial research did not establish the temporal relationship between fever and autistic regression, fever-induced regression is a well-known feature of metabolic disorders overall, and the study brings another angle to the already intriguing relationship of fever and autism.
In 2008, researchers reported that some children with ASD actually improve around periods of fever, suggesting that subgroups of ASD exist in which the individuals react differently to fever. However, these children with ASD who improved during fever were not thought to have mitochondrial disease.
“In light of this new data, it is clear we need more research into the body’s complex cascade of metabolic and immune actions that accompany fever, how those relate to the biology of autism, and the appropriateness of fever management,” commented Dr. Colamarino. “By showing that a subgroup of individuals with mitochondrial disorders may be at risk for autistic regression, the publication highlights the continued need for enhanced awareness of the clinical signs of mitochondrial dysfunction as well.”
Former FMM Board Member John Shoffner was recognized by Autism Speaks as one of the Top 10 Researchers for 2009.
A December 2010 mitochondrial research study in The Journal of the American Medical Association reports mitochondrial dysfunction may influence processes highly dependent on energy, such as neurodevelopment, and contribute to Autism. In this exploratory study, children with Autism were more likely to have mitochondrial dysfunction, mtDNAoverreplication, and mtDNA deletions than typically developing children.
This particular study has also been recognized by Autism Speaks as one of the Top 10 Research Achievements for 2010 establishing continued acknowledgement of the significance between mitochondrial dysfunction and Autism.
Many patients with ASD can be helped by effective treatments for mitochondrial dysfunction. The treatments that are being evaluated specific for mitochondrial dysfunction that results in ASD include exercise and certain supplements. Coenzyme Q10, riboflavin, various antioxidants, vitamins, and many other compounds are being investigated as methods to improve ATP generation and reduce free radical damage to cells. However, those measures may not reverse the symptoms of autism (some say they may arrest the progression of the symptoms), but can only serve to help the individual stay as healthy as possible by supporting good mitochondrial function and minimizing reactive oxygen species. Due to the varying nature of ASD, it is becoming apparent that the role of mitochondrial dysfunction should be clarified in each patient in order to determine a treatment plan. Patients should consult with physicians experienced with mitochondrial disorders to discuss any supplementation or treatments.
Rossignol DA, Bradstreet JJ.Evidence of mitochondrial dysfunction in autism and implications for treatment. Am J of Biochemistry and Biotechnology, 2008;4:208-217. Available here.