Analysis of the Glutathione Cycle: A Comparison between Children with Autism, Healthy Controls, and Unaffected Siblings

Poster Presentation
Friday, May 11, 2018: 5:30 PM-7:00 PM
Hall Grote Zaal (de Doelen ICC Rotterdam)
S. C. Boland1, E. K. Lecarie1, M. B. Klein2 and R. J. Jou3, (1)Yale Child Study Center, New Haven, CT, (2)BioElectron Technology Corporation, Mountain View, CA, (3)Yale University, New Haven, CT

Previous studies have demonstrated biochemical evidence of oxidative stress in children with autism spectrum disorder (ASD), including a subset with co-morbid mitochondrial dysfunction. Increased oxidative stress results in depletion of the endogenous cellular sulfur-hydride antioxidant system, including reduced glutathione and cysteine. Depletion of these sulfur-hydride metabolites leads to free radical-mediated cell injury and death, as well as other impairments in cellular function. Comparing the levels of key sulfur-hydride metabolites in children with and without ASD may improve understanding of underlying biochemistry and identification of candidate biomarkers and therapeutic targets.

Objectives: To compare plasma levels of key antioxidant metabolites in children with ASD to their unaffected siblings (UAS) and unrelated typically developing (TD) children.

Methods: This study consisted of 31 children between the ages of 4 and 12 years: 14 ASD (mean age = 7.79 ±2.91 years; 10 boys and 4 girls), 12 TD non-siblings (mean age = 8.08 ±2.35 years; 7 boys and 5 girls) and 5 UAS of proband participants (mean age = 7.40 ±2.88 years; 2 boys and 3 girls). Blood samples collected by venipuncture were separated into plasma and subsequently analyzed using a mass spectrometer and microflow, reversed-phase chromatography. Biomarker quantitation was performed using Multiple Reaction Monitoring (NRM) mode acquisition and with the aid of stable isotopically-labeled standards. The analytes evaluated include reduced cysteine (CysB), reduced glutathione (GSH), thiosulfate (TSH), cysteine persulfide (CyssB), glutathione persulfide (GSSB), ornithine, 5-oxoproline (PGA), and methionine. A total of the main sulfur species included CysB, GSH, TSH, CyssB, and GSSB. The following clinical data were collected: Social Responsiveness Scale (SRS), Vineland Adaptive Behavior Scales (VABS), and Differential Ability Scales (DAS). ASD diagnoses were confirmed using Autism Diagnostic Interview (ADI), Autism Diagnostic Observation Schedule (ADOS), and Diagnostic and Statistical Manual of Mental Disorders, Fourth Edition, Text Revision. Correlation analyses between analyte levels and clinical measurements were also performed.

Results: A one-way ANOVA revealed significant differences between ASD and TD groups for CysB, CyssB, GSSB, ornithine and pooled sulfur analytes while differences in GSH approached significance. Significant differences between TD and UAS groups were found in PGA and ornithine. No differences were found between ASD and UAS groups. Across all subscales of the SRS, DAS (full-scale IQ), and all subdomains of the VABS, the ASD group significantly differed from both TD and UAS groups. No significant differences were found between the TD and UAS groups. There was a significant correlation between SRS and CysB, CyssB, GSSB, and pooled analytes.

Conclusions: This preliminary study demonstrates a differential biosignature across key components of the endogenous sulfur antioxidant system in children with ASD relative to TD children, suggesting that oxidative stress-associated sulfur depletion may play a role in the pathophysiology of autism. This is also supported by the significant negative correlations between SRS scores and analyte concentrations. However, the lack of significant differences between ASD and UAS groups in analyte levels suggests metabolite differences are also influenced by genetic factors and not solely driven by ASD symptomatology.