Deciphering the Gut Microbial Contribution to the Etiology of Autism Development

Abstract

Autistic spectrum disorder (ASD) is a spectrum of early-onset lifelong neurodevelopmental disorders that severely impact social and behavioral functioning. It is a debilitating disorder that affects 1 % of the global children population with increasing prevalence and presented huge economic burden to the family and the nation. Current diagnosis for ASD is very subjective mainly because of the multifactorial nature of the disorders. The etiology of ASD is highly complex and multifaceted involving the gene, environment, and diet and is associated with various abnormalities that include immunologic, metabolic, and, more recently, the host–gut microbiome stability (Fig. 14.1). The gut microbiota is a consortium of bacteria that coexisted and coevolved with the host from the time of birth. As such the gut microbiome–mammalian “superorganism” represents a level of biological evolutionary development where true symbiosis is characterized by extensive “transgenomic” modulation of metabolism and functions between the two entities. The gut microbiota is involved in various mammalian biological processes including defense against pathogens, immunity, intestinal microvilli development, and recovery of metabolic energy through fermentation of otherwise nondigestible dietary fiber. In addition, the gut microbiota has been shown to communicate with the brain via the gut–brain axis to modulate brain development, function, and behavior. Recent evidence indicated that the gut microbiota influenced central nervous system development and responses to stress. Current understanding on the potential and extend of gut microbe involvement in brain development and host metabolic signaling is still in its infancy. Coupled with ever-increasing awareness on the importance of the gut microbiome in health and disease particularly autism, understanding the fundamental mechanistic interaction between host brain development and gut microbiota is crucial for unraveling the mystery behind the etiopathology of autism.