Comparison of blood tryptophan and glutamate levels in children and adolescents with autism and healthy controls

Studies show that there are significant increments of glutamate levels in individuals with autism spectrum disorders, which suggests that this amino acid could be a potential biomarker. We aimed to evaluate the concentration tryptophan and glutamate in the blood plasma of children with autism and their correlation with symptoms severity in children and adolescents diagnosed with autism. We assessed the plasma tryptophan and glutamate levels in the 35 children with autism and 31 unrelated healthy controls. The plasma amino acid analysis was performed by a high-pressure liquid chromatograph (HPLC). The Gilliam Autism Rating Scale (GARS-2) was used to evaluate autism severity. Compared with the control group, the autism group had higher levels of plasma glutamate (p = .005), and there was a negative correlation between stereotyped patterns score, total score of GARS-2, and plasma tryptophan levels in the autism group (p = .012, r = -0.42 and p = .034, r = -0.36 respectively). There was also a positive correlation between stereotyped patterns score and plasma glutamate levels in ASD boys (p = .050, r = 0.39). Our findings provide evidence of elevated plasma glutamate levels and for correlations between tryptophan, glutamate and severity of symptoms in children with autism.