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Unique acyl-carnitine profiles are potential biomarkers for acquired mitochondrial disease in autism spectrum disorder.

ABSTRACT: Autism spectrum disorder (ASD) has been associated with mitochondrial disease (MD). Interestingly, most individuals with ASD and MD do not have a specific genetic mutation to explain the MD, raising the possibility of that MD may be acquired, at least in a subgroup of children with ASD. Acquired MD has been demonstrated in a rodent ASD model in which propionic acid (PPA), an enteric bacterial fermentation product of ASD-associated gut bacteria, is infused intracerebroventricularly. This animal model shows validity as it demonstrates many behavioral, metabolic, neuropathologic and neurophysiologic abnormalities associated with ASD. This animal model also demonstrates a unique pattern of elevations in short-chain and long-chain acyl-carnitines suggesting abnormalities in fatty-acid metabolism. To determine if the same pattern of biomarkers of abnormal fatty-acid metabolism are present in children with ASD, the laboratory results from a large cohort of children with ASD (n=213) who underwent screening for metabolic disorders, including mitochondrial and fatty-acid oxidation disorders, in a medically based autism clinic were reviewed. Acyl-carnitine panels were determined to be abnormal if three or more individual acyl-carnitine species were abnormal in the panel and these abnormalities were verified by repeated testing. Overall, 17% of individuals with ASD demonstrated consistently abnormal acyl-carnitine panels. Next, it was determined if specific acyl-carnitine species were consistently elevated across the individuals with consistently abnormal acyl-carnitine panels. Significant elevations in short-chain and long-chain, but not medium-chain, acyl-carnitines were found in the ASD individuals with consistently abnormal acyl-carnitine panels-a pattern consistent with the PPA rodent ASD model. Examination of electron transport chain function in muscle and fibroblast culture, histological and electron microscopy examination of muscle and other biomarkers of mitochondrial metabolism revealed a pattern consistent with the notion that PPA could be interfering with mitochondrial metabolism at the level of the tricarboxylic-acid cycle (TCAC). The function of the fatty-acid oxidation pathway in fibroblast cultures and biomarkers for abnormalities in non-mitochondrial fatty-acid metabolism were not consistently abnormal across the subgroup of ASD children, consistent with the notion that the abnormalities in fatty-acid metabolism found in this subgroup of children with ASD were secondary to TCAC abnormalities. Glutathione metabolism was abnormal in the subset of ASD individuals with consistent acyl-carnitine panel abnormalities in a pattern similar to glutathione abnormalities found in the PPA rodent model of ASD. These data suggest that there are similar pathological processes between a subset of ASD children and an animal model of ASD with acquired mitochondrial dysfunction. Future studies need to identify additional parallels between the PPA rodent model of ASD and this subset of ASD individuals with this unique pattern of acyl-carnitine abnormalities. A better understanding of this animal model and subset of children with ASD should lead to better insight in mechanisms behind environmentally induced ASD pathophysiology and should provide guidance for developing preventive and symptomatic treatments.

SUBMITTER: Frye RE

PROVIDER: S-EPMC3566723 | biostudies-literature | 2013 Jan

REPOSITORIES: biostudies-literature

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Unique acyl-carnitine profiles are potential biomarkers for acquired mitochondrial disease in autism spectrum disorder.

Frye R E RE Melnyk S S Macfabe D F DF

Translational psychiatry 20130122

Autism spectrum disorder (ASD) has been associated with mitochondrial disease (MD). Interestingly, most individuals with ASD and MD do not have a specific genetic mutation to explain the MD, raising the possibility of that MD may be acquired, at least in a subgroup of children with ASD. Acquired MD has been demonstrated in a rodent ASD model in which propionic acid (PPA), an enteric bacterial fermentation product of ASD-associated gut bacteria, is infused intracerebroventricularly. This animal m ...[more]

PMID: 23340503

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Project description:BackgroundEarly identification and treatment of individuals with autism spectrum disorder (ASD) improves outcomes, but specific evidence needed to individualize treatment recommendations is lacking. Biomarkers that could be routinely measured within the clinical setting could potentially transform clinical care for patients with ASD. This demonstration project employed collection of biomarker data during regular autism specialty clinical visits and explored the relationship of biomarkers with clinical ASD symptoms.MethodsEighty-three children with ASD, aged 5-10 years, completed a multi-site feasibility study integrating the collection of biochemical (blood serotonin, urine melatonin sulfate excretion) and clinical (head circumference, dysmorphology exam, digit ratio, cognitive and behavioral function) biomarkers during routine ASD clinic visits. Parents completed a demographic survey and the Aberrant Behavior Checklist-Community. Cognitive function was determined by record review. Data analysis utilized Wilcoxon two-sample tests and Spearman correlations.ResultsParticipants were 82% male, 63% White, 19% Hispanic, with a broad range of functioning. Group means indicated hyperserotonemia. In a single regression analysis adjusting for race and median household income, higher income was associated with higher levels of blood serotonin and urine melatonin sulfate excretion levels (p = 0.004 and p = 0.04, respectively). Melatonin correlated negatively with age (p = 0.048) and reported neurologic problems (p = 0.02). Dysmorphic status correlated with higher reported stereotyped behavior (p = 0.02) and inappropriate speech (p = 0.04).ConclusionThis demonstration project employed collection of multiple biomarkers, allowed for examination of associations between biochemical and clinical measures, and identified several findings that suggest direction for future studies. This clinical research model has promise for integrative biomarker research in individuals with complex, heterogeneous neurodevelopmental disorders such as ASD.

Project description:Autism Spectrum Disorder (ASD) lacks validated measures of core social functions across development stages suitable for clinical trials. We assessed the concurrent validity between ASD clinical measures and putative biomarkers of core deficits, and their feasibility of implementation in human studies. Datasets from two adult ASD studies were combined (observational study [n = 19] and interventional study baseline data [n = 19]). Potential biomarkers included eye-tracking, olfaction, and auditory and visual emotion recognition assessed via the Affective Speech Recognition test (ASR) and Reading-the-Mind-in-the-Eyes Test (RMET). Current functioning was assessed with intelligence quotient (IQ), adaptive skill testing, and behavioral ratings. Autism severity was determined by the Autism Diagnostic Observation Scale-2 and Social Communication Interaction Test (SCIT). Exploratory measures showed varying significant associations across ASD severity, adaptive skills, and behavior. Eye tracking endpoints showed little relationship to adaptive ability but correlated with severity and behavior. ASR scores significantly correlated with most adaptive behavior domains, as well as severity. Olfaction predicted visual and auditory emotion recognition. SCIT scores related moderately to multiple severity domains, and was the only measure not related with IQ. RMET accuracy was less related to ASD features. Eye tracking, SCIT, and ASR showed high test-retest reliability. We documented associations of proximal biomarkers of social functioning with multiple ASD dimensions. With the exception of SCIT, most correlations were modest, limiting utility as proxy measures of social communication. Feasibility and reliability were high for eye-tracking, ASR, and SCIT. Overall, several novel experimental paradigms showed potential as social biomarkers or surrogate markers in ASD. Autism Research 2018, 11: 1567-1579. © 2018 The Authors. Autism Research published by International Society for Autism Research and Wiley Periodicals, Inc. LAY SUMMARY: More accurate measurements of treatment effects are needed to help the development of new drug treatments for autism spectrum disorders (ASD). This study evaluates the relationship between assessments designed to measure behaviors associated with social communication and cognition in ASD with clinical and diagnostic assessments of symptom severity as well as their implementation. The assessments including eye-tracking, auditory and visual social stimuli recognition, and olfaction identification showed potential for use in the evaluation of treatments for social difficulties in ASD.

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Unique acyl-carnitine profiles are potential biomarkers for acquired mitochondrial disease in autism spectrum disorder.

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Unique acyl-carnitine profiles are potential biomarkers for acquired mitochondrial disease in autism spectrum disorder.

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