The impact of acute and chronic stress on gastrointestinal physiology and function: a microbiota-gut-brain axis perspective

The physiological consequences of stress often manifest in the gastrointestinal tract. Traumatic or chronic stress is associated with widespread maladaptive changes throughout the gut, although comparatively little is known about the effects of acute stress. Furthermore, these stress-induced changes in the gut may increase susceptibility to gastrointestinal disorders and infection, and impact critical features of the neural and behavioural consequences of the stress response by impairing gut-brain axis communication. Understanding the mechanisms behind changes in enteric nervous system circuitry, visceral sensitivity, gut barrier function, permeability, and the gut microbiota following stress is an important research objective with pathophysiological implications in both neurogastroenterology and psychiatry. Moreover, the gut microbiota has emerged as a key aspect of physiology sensitive to the effects of stress. In this review, we focus on different aspects of the gastrointestinal tract including gut barrier function as well as the immune, humoral and neuronal elements involved in gut-brain communication. Furthermore, we discuss the evidence for a role of stress in gastrointestinal disorders. Existing gaps in the current literature are highlighted, and possible avenues for future research with an integrated physiological perspective have been suggested. A more complete understanding of the spatial and temporal dynamics of the integrated host and microbial response to different kinds of stressors in the gastrointestinal tract will enable full exploitation of the diagnostic and therapeutic potential in the fast-evolving field of host-microbiome interactions.image Abstract figure legend Acute and chronic stress exert wide-ranging effects across the gut-brain axis. In the case of acute stress, the enteric nervous system may be activated and gut contractility modified. This is associated with altered serotonin metabolism in the gastrointestinal tract as well as activation of the innate immune system and suppression of the adaptive immune system. Less is known about how acute stress impacts gastrointestinal physiology and the gut microbiome. Chronic stress, depending on the type, timing and duration of exposure, impairs vagal signalling and enteric nerve function, impairs gut motility and induces visceral hypersensitivity. Both cellular and humoral immunity are suppressed, and the gut barrier exhibits reduced mucus layer thickness, increased paracellular permeability and infiltration of circulating immune cells, as well as increased mast cell degranulation. The gut microbiome exhibits reduced stability and altered composition and function. Specifically, the relative abundance of beneficial bacteria is reduced.image

Automated summary

The physiological consequences of stress often affect the gastrointestinal tract, and understanding the mechanisms behind these effects is important in the fields of neurogastroenterology and psychiatry. Stress-induced changes in the gut can increase susceptibility to gastrointestinal disorders and impair gut-brain communication. The gut microbiota is also sensitive to the effects of stress. This review focuses on different aspects of the gastrointestinal tract, including gut barrier function and gut-brain communication, and discusses the evidence for a role of stress in gastrointestinal disorders.