Neurotransmitter and amino acid levels in Nigerian children with autism spectrum disorders

Abstract

Autism Spectrum Disorder (ASD), often referred to as Autism, is a clinically heterogeneous neurodevelopmental disorder with core-defining features of impaired socialization, impaired verbal and nonverbal communication, and restricted and repetitive patterns of behaviour. The disorder is presently diagnosed behaviourally, however the search for possible biomarkers that could aid earlier diagnosis have been on the increase. The present study aims to investigate plasma amino acid levels as a potential biomarker in ASD screening. Plasma levels of 20 amino acids (AA) (including neurotransmitters-GABA and glutamate) of autistic individuals and typical age and sex matched control, were determined using reversed-phase high performance liquid chromatography (RPHPLC). All statistical analyses (independent t-test, spearman correlation, cohen’s d effect size) were done using IBM SPSS version 20. A total of 31 plasma samples (18 Autism cases and 13 agesex matched controls) were analyzed with mean ages 8.44±4.87 for cases and 8.15±4.88 for controls. No significant intergroup difference was observed in the individual amino acid levels with the exception of glutamate (t = 5.472, df = 2.324, p = 0.000063), glutamine (t = 8.342, df = 14.780, p = 0.000001) , GABA (t = 6.601, df = 24.593, p = 0.000001), tryptophan (t = 3.568, df = 16.472, p = 0.002) and cysteine (t = 4.000, df = 13.762, p = 0.001).The amino acid profile and the glutamate - GABA levels can serve as biochemical markers for ASD, and can thus be utilized as screening for earlier diagnosis of the disorder.

Keywords: Autism Spectrum Disorder (ASD), Biomarkers, Neurotransmitters, GABA, Glutamate, Diagnosis