Reduction of essential amino acid levels and sex-specific alterations in serum amino acid concentration profiles in children with autism spectrum disorder

•The serum levels of essential amino acids were reduced in children with ASD.•There are sex-specific differences in certain amino acids concentration in children with ASD.•Dysregulation of amino acid metabolism provide clues for future etiological research of ASD. Existing evidence has shown that metabolic disturbances may be involved in the pathological process of autism spectrum disorder(ASD). This study aimed to investigate the alterations of serum amino acid concentration profiles in Chinese Han children with ASD. Serum amino acid levels were measured using tandem mass spectrometry in 60 children with ASD and 30 typically developing (TD) controls. The Chinese Wechsler Young Children Scale of Intelligence (C-WYCSI) was used to evaluate the ASD subjects’ intelligence quotient (IQ). The serum levels of essential amino acids and some non-essential amino acids (glutamine, glycine, alanine, citrulline, cysteine, serine, tyrosine, and proline) in the ASD group were significantly lower than those in controls. The serum glutamate/glutamine (Glu/Gln) ratio was elevated in the ASD PIQ≥70 group, while serum levels of alanine, cysteine, phenylalanine, methionine and proline were significantly higher in male children with ASD than that in the female group. The study revealed that children with ASD exhibit alterations in the serum levels of certain amino acids, and the divergence can be sex-related or associated with different cognitive function, which might provide clues for further etiological research of ASD.