The microbiome as a novel paradigm in studying stress and mental health.

Abstract

At the intersection between neuroscience, microbiology, and psychiatry, the enteric microbiome has potential to become a novel paradigm for studying the psychobiological underpinnings of mental illness. Several studies provide support for the view that the enteric microbiome influences behavior through the microbiota-gut-brain axis. Moreover, recent findings are suggestive of the possibility that dysregulation of the enteric microbiota (i.e., dysbiosis) and associated bacterial translocation across the intestinal epithelium may be involved in the pathophysiology of stress-related psychiatric disorders, particularly depression. The current article reviews preliminary evidence linking the enteric microbiota and its metabolites to psychiatric illness, along with separate lines of empirical inquiry on the potential involvement of psychosocial stressors, pro-inflammatory cytokines and neuroinflammation, the HPA axis, and vagal nerve activation, respectively, in this relationship. Finally, and drawing on these independent lines of research, an integrative conceptual model is proposed in which stress-induced enteric dysbiosis and intestinal permeability confer risk for negative mental health outcomes through immunoregulatory, endocrinal, and neural pathways.

Vulnerability of the industrialized microbiota

“…Acute perturbations from diet, antibiotics, and medical practices could have been propagated over generations and synergized with heightened hygiene and sanitation to result in the population-wide ecosystem re-configurations observed today. The effects of other factors associated with an industrialized lifestyle on the microbiota, including increased sedentary behavior, stress, exposure to new chemicals (e.g., plastics, herbicides, and pesticides), and social isolation, have only begun to be explored (55)(56)(57).…”

Primate microbial endocrinology: An uncharted frontier

“…Hormones involved in the stress response, such as catecholamines (e.g., epinephrine, norepinephrine, dopamine) and glucocorticoids, have long been known to interact with mammalian gut microbes (Eriksson, ; Liu, ). Using Gram negative bacteria cultures, Lyte and Ernst () observed a significantly increased growth rate of Yersinia enterocolitica , in response to norepinephrine.…”

Immunosuppressive effect and global dysregulation of blood transcriptome in response to psychosocial stress in vervet monkeys (Chlorocebus sabaeus)

“…Psychosocial stress can also increase the permeability of the intestinal barrier, causing the translocation of bacteria and antigens from the gut to the bloodstream and, in turn, activating pro-inflammatory responses [41][42][43] . To assess the potential effects of PS on the permeability of the gut epithelium and systemic inflammatory state, we investigated plasma levels of the microbial translocation biomarker sCD14, an indicator of monocyte activation, as well as levels of the bacterial endotoxin lipopolysaccharide (LPS).…”