Gastrointestinal condition, nutritional aspects and gut microbiota in Autism Spectrum Disorders: a new perspective for research and intervention

In the last two decades several studies have been trying to explore a possible role for gut microbiota in Autism Spectrum Disorders (ASD), supported by the high incidence of gastrointestinal disorders among ASD children and by the now well recognized existence of the brain-gut-microbiota axis (the complex system of bidirectional interactions between central nervous system, gastrointestinal tract and microorganisms inhabiting the gut). Nevertheless, results about alterations in gut microbiota composition and/or activity in ASD are to date strongly contrasting. A possible explanation could be that these studies tend to treat ASD as a unique pathology, whereas it includes different cognitive-behavioural phenotypes. Moreover, they do not consider factors which are important for children’s gut flora development, such as type of delivery, nutritional history (e.g. formula milk during lactation) and medical history (e.g. antibiotics intake) as well as factors that may affect the present composition of microbiota, such as the current diet (e.g. the strong food selectivity that often occurs in ASD children) and the presence of gastrointestinal disorders. In this study, I developed an interview to parents to assess whether there are differences related to the above mentioned aspects between ASD children and typically developing children and among ASD themselves, considering differences in cognitive level and severity of autistic traits. I also explored the use of special diets such as gluten-, lactose and casein free diets, the reasons for their adoption and the possible benefits for the child. Moreover, I decided to include in this interview also a section dedicated to parental difficulties in managing mealtime in order to collect information useful to plan future interventions. I found differences between ASD- and typical children in the incidence of gastrointestinal disorders and food selectivity. Especially, some children initially eat everything and then switch to a more and more restricted diet. This could be considered an early symptom of the pathology. I also found an association between gastrointestinal disorders and severity of autistic traits. Furthermore, I collected faecal samples from ASD families (two parents, an ASD child and a typically developing sibling) and analysed them with metaproteomics and bioinformatics techniques in order to assess microbiota activity and evaluate it in light of ASD phenotype, nutritional habits, gastrointestinal disorders and genetic proximity. Demonstrating the existence of a different microbiota composition in ASD or at least in a subgroup could allow to identify a biomarker of a possible development of ASD and to design preventive interventions, even through probiotics intake. Moreover, it could help to better understand the molecular mechanism underlying this pathology.