Retrospective analysis of the correlation between serum vitamin D levels and blood amino acids levels in children with autism: Exploration of possible mechanisms of the effect of vitamin D on autism

Hypovitaminosis D has been recognized as a risk factor for autism spectrum disorder (ASD); however, its mechanism remains unclear. Amino acid metabolism is involved in the related factors of ASD, such as neurotransmitters, oxidative stress, and immune dysfunction. Vitamin D not only regulates the activity of the amino acid transport system, but is also closely related to amino acids in the regulation of immunity and oxidative stress. To investigate the possible mechanisms by which vitamin D may influence ASD, the correlation between blood amino acids and serum 25(OH)D levels of 506 children (411 males and 95 females) with ASD were retrospectively analyzed, and possible related pathways were determined via a literature review. According to the results, alanine, arginine, glycine, ornithine, glutamine and histidine were found to be significantly negatively correlated with serum 25(OH)D levels (P < 0.05). Glycine and ornithine were also found to be influenced by age, and glutamine levels were different in male and female children with ASD. In addition, there were differences in alanine levels in different BMI levels. However, after adjusting for the influences of these factors in the regression equation, it was found that 25(OH)D was associated with the identified 6 amino acids (P < 0.05). Therefore, vitamin D may influence ASD through the cross-pathways of these amino acids (i.e. glutamine-gamma aminobutyric acid balance, oxidative stress, and immune dysfunction). This conclusion may provide some ideas for further investigation of the effect of vitamin D on ASD.