Figure 1.

A critical window in early life for gut microbiota assembly and neurodevelopment. Preterm infants are at high risk of both gastrointestinal and neurodevelopmental impairment due to a peculiar developmental environment, with impaired gut microbiota assembly. (A) Brain developmental events during prenatal and early postnatal life that correspond to windows of vulnerability. Developmental processes occur in phases, setting the stage for potential periods of susceptibility to stimuli and insults that may affect brain growth and function. (B) Bidirectional gut-brain communication pathways. Evidence from animal studies suggests that gut hormones, growth factors, microbial metabolites, and receptors are involved in the microbiota-gut-brain axis. 5-HT: 5-hydroxytryptamine or serotonin; IGF-1: insulin-like growth factor-1; BDNF: brain-derived neurotrophic factor; PDGF-BB: platelet-derived growth factor-BB; SCFAs: short-chain fatty acids; FFAR2: free fatty acids receptor 2. (C) Dysbiotic gut microbiota profiles negatively affect gut-brain communication. Some specific bacterial taxa have been shown to be associated with neurodevelopmental outcomes in preterm infants. Up arrows indicate an increase in relative abundance of taxa, down arrows indicate a decrease in relative abundance of taxa.