Biomarkers of Abnormal Energy Metabolism in Children with Autism Spectrum Disorder

Biomarkers of mitochondrial disease were studies in 133 consecutive autism spectrum disorder patients to determine the prevalence of abnormalities in biomarkers of mitochondrial disease. Biomarkers included traditional biomarkers of mitochondrial disease (lactate, alanine), fatty-acid oxidation defects (acyl-carnitine panel) and recently described novel biomarkers of detecting mitochondrial dysfunction in individuals with autism spectrum disorder (alanine-to-lysine ratio, creatine kinase, aspartate transaminase). Biomarkers were collected in the morning fasting state. Abnormal biomarker values were verified by repeat testing. For those with abnormal acyl-carnitine panels, secondary disorders of fatty acid metabolism were ruled out. Abnormalities in lactate, alanine-to-lysine ratio and acyl-carnitine panels occurred in over 30% of children on initial testing. Among the patients with abnormal biomarkers who had repeated testing, abnormalities were confirmed about half of the time except for alanine which was only confirmed 20% of the time. Elevation in alanine-to-lysine ratio was associated with epilepsy and elevation in multiple acyl-carnitines was associated with regression. In order to confirm the significance of certain biomarkers, a wide variety of mitochondrial biomarker values were compared between specific subgroups of children with abnormal biomarkers and matched children without any abnormalities in biomarkers. Lactate, alanine-to-lysine ratio and acyl-carnitine panel groups demonstrated abnormalities in multiple mitochondrial biomarkers, confirming the validity of these biomarkers of mitochondrial dysfunction. This study demonstrates that multiple biomarkers of mitochondrial dysfunction are elevated in a significant portion of children with autism spectrum disorder and lend support to the notion that disorders of energy production may affect a significant subset of children with autism.