Children with autism spectrum disorder often have intestinal problems, such as constipation and diarrhea. The following could be the cause of the increased synthesis in tryptophan in intestinal tract, which could lead to increased absorption in blood stream and its metabolism into uremic toxins. Uremic toxins in higher concentration amplify oxidative stress, which could potentially have effect on microcirculation of the brain and function of the brain cells, which has lately shown to have effect on cognitive disorders development.
Because of that, we decided to measure concentrations of three uremic toxins in urine sample: symmetrical dimethylarginine, asymmetrical dimethylarginine and indoxyl sulfate. Concentration measurement was done on 143 urine samples of children with autism spectrum disorder and on 47 urine samples of healthy children by using enzyme-linked immunosorbent assay. Results were then statistically analyzed and then compared between groups of children with autism spectrum disorder and healthy children. We also compared results between subgroups of children with spectrum disorder, which are autism and Asperger syndrome and control group. Concentrations of the parameters were also compared based on the gender, age and severity level of disorder in children with autism spectrum disorder.
The results showed, that children with autism spectrum disorder compared to healthy children have statistically significant lower concentration of symmetrical and asymmetrical dimethylarginine, while significant difference in concentration of indoxyl sulfate was not proven. Children with autism and Asperger syndrome were also proven to have significant lower concentration of symmetrical and asymmetrical dimethylarginine than healthy children. When comparing between subgroups, we could only prove significant higher ratios of symmetrical and asymmetrical dimethylarginine with creatinine in children with autism compared to those with Asperger syndrome. Gender comparison of the parameters in the children with the autism spectrum disorder failed to yield any significant difference, which goes the same for the comparison based on the age of the children with autism spectrum disorder. We also failed to demonstrate any significant differences between groups that based on the severity level of the autism spectrum disorder (mild, moderate and severe).
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