The alteration in the profile of gut microbiota was investigated in a population of patients with ASD and correspondent HCs by applying a robust statistical approach, adjusting for potential confounders. Although our results confirm that ASD was characterized by several changes in microbiota composition when compared with HCs, the results showed that the analysis might be affected by a variety of confounding factors, in which the severity of the disease itself has a certain impact on the results [11]. Our study was more concerned on the effects of gut microbiota imbalance on the nervous system and cognitive function of ASD and HC. ASD children abundance of Bacteroidales and Selenomonadales was significantly lower than that in normal children. The difference in the level of gut microbiota at the class level is remarkably significant for the host, which has also been reported in other studies related to the relationship between neurological lesions and gut microbiota [12]. The dysregulation of Bacteroidales and Selenomonadales affects intestinal secretion and in turn affects brain function through the vagal response [13]. The role of Bacteroidales is to maintain the immune regulation of intestinal mucosal cells such as CD4+T cells, CD8+ T cells and TLR responses, and they may also affect the development of host neurological function [14]. In addition, the within-group analysis according to ASD clinical features suggests the potential role of microbial composition (in particular Ruminococcaceae and Prevotellaceae) and the differential effects of the gut microbiota that further affect the children.
In the intestinal microbiota biodiversity analysis, the concentration trend in HCs was significantly different from the one in the ADS children. In the intestinal microbiota biodiversity analysis in the ASD children, the trend of HC concentration is significantly different, and in the alpha diversity analysis based on the biological microbiota, the trend of intestinal microbiota diversity reflecting ASD children is different from HCs [15–16]. Because children’s nervous system and immune system are not yet well developed, factors such as cesarean section and breastfeeding were consider because they have a significant impact on the microbial community of infants and young children, and these differences affect children’s development [17–18]. However, the baseline parameters of the children included in this study are referred to a small sample size and, thus, the results were not significant. However, in combination with the biological function prediction of KEGG, it was remarkable to notice that the imbalance of intestinal microbiota led to the inhibition of ASD nervous system and environmental information processes, in addition to the changes of Cellular Processes, which explained the influence of microbiota imbalance to some extent. Since the gut microbiota is controlled by the brain - gut axis, it affects the cognitive abilities of children with ASD and their responses to environmental information.
Due to our small sample size, the relationship between ASD and HC baseline parameters and cesarean section, breastfeeding and other factors, as well as the occurrence of ASD and gut microbiota imbalance, did not significantly differ. Autism is also a disease that is affected by multiple genes and environmental factors. However, the impact of genetic factors is not considered in our present research. Thus, further studies with a larger sample and prospective follow-up study is needed. However, our results demonstrated that it might be possible to improve the state of the nervous system development in patients with ASD by altering the food intake of children with ASD, thus interfering in a positive manner with the composition of the gut microbiota [19–22].