Gut–brain axis

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Not to be confused with Neuraxis.

The gut–brain axis refers to the biochemical signaling taking place between the gastrointestinal tract and the nervous system, often involving intestinal microbiota,[1] which have been shown to play an important role in healthy brain function.[2][3]

Brain function[edit]

Research suggests that the gut–brain axis, a bidirectional neurohumoral communication system in the human body, functions as a pathway for the gut microbiota to modulate brain function of its host. The postnatal microbial colonization of the gastrointestinal (GI) tract results in a long-lasting impact on the neural processing of sensory information regarding the hypothalamic-pituitary-adrenal stress response. Early postnatal bacterial colonization in germ free (GF) mice promoted the development of a central nervous system. The c-Fos activation in the paraventricular nucleus was rapidly induced by the inoculation of Bifidobacterium infantis. Tryptophan metabolism was modulated by Bifidobacterium infantis, suggesting that the normal gut microbiota can influence the precursor pool for serotonin, which is correlated to neurophysiological behavior. Anxiety-like behavior and central neurochemical changes were relieved in GF mice compared with specific pathogen free (SPF) mice. In addition, bacterial species Clostridial were found at an elevated level in the stools of children with autism than the stools of the children without.[4]

Behavioral phenotype[edit]

During birth, the immediate microbial colonization contributes to the development of epithelial barrier function, gut homeostasis, angiogenesis, innate adaptive immune function, and common neuro-developmental disorders (autism, schizophrenia). Compared to the specific pathogen free (SPF) mice, the germ free (GF) mice illustrated increased motor activity, reduced anxiety-like behavior, altered expression of synaptic plasticity-related genes, elevated noradrenaline, dopamine, and 5-hydroxytryptamine turnover in the striatum. When exposed to antibiotics, GI infections and stress, sharp changes in diet, the gut homeostasis and the central nervous system becomes imbalanced. Clinically, the introduction of probiotics, beneficial in the treatment of GI symptoms of disorder, help reduce anxiety, stress, and mood of patients with irritable bowel syndrome (IBS) and chronic fatigue. Lactobacillus reuteri, probiotic, is known to modulate the immune system, decrease anxiety, and reduce the stress-induced increase of corticosterone. Other probiotics can lower inflammatory cytokines, decrease oxidative stress, and improve nutritional status.[4]

Gut–brain–liver axis[edit]

The liver plays a dominant role in blood glucose homeostasis by maintaining a balance between the uptake and storage of glucose through the metabolic pathways of glycogenesis and gluconeogenesis. In recent studies, it is illustrated that intestinal lipids regulate glucose homeostasis involving a gut-brain-liver axis. The direct administration of lipids into the upper intestine increases the long chain fatty acyl-coenzyme A (LCFA-CoA) levels in the upper intestines and suppresses glucose production even under sub diaphragmatic vagotomy or gut vagal deafferentation. This interrupts the neural connection between the brain and the gut and blocks the upper intestinal lipids’ ability to inhibit glucose production. The gut-brain-liver axis can regulate the glucose homeostasis in the liver and provide potential therapeutic methods to treat obesity and diabetes.[4]

See also[edit]


  1. ^ Montiel-Castro, A. J.; González-Cervantes, R. M.; Bravo-Ruiseco, G.; Pacheco-López, G. (2013). "The microbiota-gut-brain axis: Neurobehavioral correlates, health and sociality". Frontiers in Integrative Neuroscience 7. doi:10.3389/fnint.2013.00070.  edit
  2. ^ Foster, J. A.; McVey Neufeld, K. A. (2013). "Gut–brain axis: How the microbiome influences anxiety and depression". Trends in Neurosciences 36 (5): 305–312. doi:10.1016/j.tins.2013.01.005. PMID 23384445.  edit
  3. ^ Cryan, J. F.; Dinan, T. G. (2012). "Mind-altering microorganisms: The impact of the gut microbiota on brain and behaviour". Nature Reviews Neuroscience 13 (10): 701–712. doi:10.1038/nrn3346. PMID 22968153.  edit
  4. ^ a b c Chen, X., Roshan S., and Seong-Tshool H.. "The role of gut microbiota in the gut-brain axis: current challenges and perspectives." Protein & Cell 4.6 (2013): 403-14. PMID 23686721
  • Hooper LV, Macpherson AJ. Immune adaptations that maintain homeostasis with the intestinal microbiota. Nat Rev Immunol 2010; 10: 159–69 PMID 20182457.
  • Hooper LV, Gordon JI. Commensal host-bacterial relationships in the gut. Science 2001; 292: 1115–8 PMID 11352068.
  • Zoetendal E, Akkermans AD, DeVos WM. Temperature gradient gel electrophoresis analysis of 16S rRNA from human fecal samples reveals stable and host-specific communities of active bacteria. Appl Environ Microbiol 1998; 64: 3854–9 PMID 9758810.
  • Bass NM. Review article: the current pharmacological therapies for hepatic encephalopathy. Aliment Pharmacol Ther 2007; 25(Suppl 1): 23–31 PMID 17295849.
  • Parracho HM, Bingham MO, Gibson GR, McCartney AL. Differences between the gut microflora of children with autistic spectrum disorders and that of healthy children. J Med Microbiol 2005; 54: 987–91 PMID 16157555.
  • Sandler RH, Finegold SM, Bolte ER et al. Short-term benefit from oral vancomycin treatment of regressive-onset autism. J Child Neurol 2000; 15: 429–35 PMID 10921511.
  • Mehdi S. Antibiotic-induced psychosis: a link to D-alanine? Med Hypotheses 2010; 75: 676–7 PMID 20691544.
  • Bercík P, De Giorgio R, Blennerhassett P, Verdú EF, Barbara G, Collins SM. Immune-mediated neural dysfunction in a murine model of chronic Helicobacter pylori infection. Gastroenterology 2002; 123: 1205–15 PMID 12360482.
  • Bercik P, Verdú EF, Foster JA, Lu J, Scharringa A, Kean I, Wang L, Blennerhassett P, Collins SM. Role of gut-brain axis in persistent abnormal feeding behavior in mice following eradication of Helicobacter pylori infection. Am J Physiol Regul Integr Comp Physiol 2009; 296: R587–94 PMID 19129375.
  • Chen X, D'Souza R, Hong ST. "The role of gut microbiota in the gut-brain axis: current challenges and perspectives." Protein & Cell 4.6 (2013): 403-14 PMID 23686721.