Comparing Urinary Effect Size Related to Behavioral Symptoms between Total Antioxidant Capacity and Hexanoyl-lysine in Individuals with Autism Spectrum Disorders

Abstract

The imbalance between oxidative stress such as increased free radicals and decreased antioxidant capacity has been implicated in the etiology of autism spectrum disorders (ASD). However. which of these has a greater effects on ASD behavioral symptoms is still unclear. We measured urinary levels of the oxidative stress biomarker hexanoyl-lysine (HEL) and the total antioxidant capacity (TAC) and the plasma levels of the oxidative stress biomarker superoxide dismutase (SOD) and of the anti-inflammatory fatty acid eicosapentaenoic acid (EPA). We examined the relationships between these biomarkers and behavioral symptoms in 19 individuals with ASD (mean age 10.9 ± 5.3 years) and 11 healthy controls (mean age 14.3 ± 6.3 years). Ages were not no significant difference between the two groups. Behavioral symptoms were assessed using the Aberrant Behavior Checklist (ABC). In the ASD group, urinary TAC levels were significantly lower and urinary HEL levels were significantly higher than in the control group without plasma SOD and EPA levels. ABC scores were significantly higher in the ASD group than in the control group. Stepwise regression analysis and the standardized regression coefficient revealed that urinary TAC levels provided greater impact for distinguishing the two groups, and that that TAOC levels had a larger effect size than HEL levels in urine. Plasma SOD levels were significantly correlated with the ABC irritability and stereotypy score. Thus, urinary TAP levels may be important factor in the pathophysiology of ASD, and altered plasma SOD levels may contribute to the autistic behaviors.