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The intestinal mucus layer

A mucus layer protects the intestinal cell lining

The intestines are lined with a layer of mucus that acts as a physical barrier to separate the contents of the intestine, such as bacteria, from the rest of the human body. In the small intestine, there is just one thin mucus layer, which allows uptake of nutrients. In the stomach and colon, there are two layers of mucus, to give stronger protection to the underlying layer of cells called the epithelium. The inner of these two mucus layers cannot be crossed by bacteria.1,2

The mucus layer is continuously and rapidly replenished by secretion from mucus-producing cells, called ‘goblet cells’, creating a flow of mucus away from the epithelium.3 There are a range of anti-bacterial molecules and antibodies in the mucus layer that further reinforce the mucus barrier.4

Different factors influence the mucus layer

Some bacteria that can cause infections have developed mechanisms that reduce mucus secretion as part of the way they cause illness.5 By reducing the thickness of the mucus layer, these bacteria can get closer to the epithelial cells to cause problems. People with intestinal inflammatory diseases often have a reduced or modified mucus layer.5-8 In some cases, the thinner the mucus layer, the more severe the illness can be.9

Studies in animals have suggested that lifestyle factors may affect the intestinal mucus layer and its barrier function. These include: diet10-13 alcohol consumption14, psychological stress15-17, and aging18.

Additionally, the mix of the bacteria living in the gut, called the microbiome, influences mucus barrier function.19,20 There is not much information available on the relationship between diet and the mucus barrier from studies in humans, but a recent study showed that a thinner colonic mucus layer was linked with how much red meat and whole-grain the person has in their diet.21

Some probiotics may support the mucus layer

Some probiotics may stimulate mucus production and support the mucus barrier. For example, the probiotic Lactobacillus rhamnosus, LGG® has sticky, hair-like structures called ‘pili’ coming out from its surface. These help LGG® to stick to intestinal mucus and epithelial cells, making sure they have close contact with the epithelium.22,23 Studies have also shown that LGG® is able to increase the production of mucus in epithelial cells because this probiotic makes a specific protein called p40.24,25

Another probiotic, Bifidobacterium, BB-12®, has been shown in studies to increase the intestinal secretion of small anti-bacterial proteins and antibodies that enhance normal mucosal barrier function.26,27

LGG®, and BB-12® are registered trademarks of Chr. Hansen A/S.

The article is provided for informational purposes regarding probiotics and is not meant to suggest that any substance referenced in the article is intended to diagnose, cure, mitigate, treat, or prevent any disease.

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Reference list

  1. Johansson MEV, et al. The two mucus layers of colon are organized by the MUC2 mucin, whereas the outer layer is a legislator of host-microbial interactions. Proc Natl Acad Sci U S A. 2011;108(Suppl 1):4659–4665. (PubMed)
  2. Johansson MEV, et al. The gastrointestinal mucus system in health and disease. Nat Rev Gastroenterol Hepatol. 2013;10(6):352–361. (PubMed)
  3. Johansson MEV. Fast renewal of the distal colonic mucus layers by the surface goblet cells as measured by in vivo labeling of mucin glycoproteins. PLoS One. 2012;7(7):e41009. (PubMed)
  4. Johansson MEV, Hansson GC. Immunological aspects of intestinal mucus and mucins. Nat Rev Immunol. 2016;16(10):639–649. (PubMed)
  5. Cornick S, et al. Roles and regulation of the mucus barrier in the gut. Tissue Barriers. 2015;3(1-2):e982426. (PubMed)
  6. Capaldo CT, et al. Layered defense: how mucus and tight junctions seal the intestinal barrier. J Mol Med (Berl). 2017;95(9):927-934. (PubMed)
  7. Strugala V, et al. Thickness and continuity of the adherent colonic mucus barrier in active and quiescent ulcerative colitis and Crohn’s disease. Int J Clin Pract. 2008;62(5):762–769. (PubMed)
  8. Johansson MEV, et al. Bacteria penetrate the normally impenetrable inner colon mucus layer in both murine colitis models and patients with ulcerative colitis. Gut. 2014;63(2):281–291. (PubMed)
  9. Schroeder BO. Fight them or feed them: How the intestinal mucus layer manages the gut microbiota. Gastroenterol Rep (Oxf). 2019;7(1):3–12. (PubMed)
  10. Schroeder BO, et al. Bifidobacteria or Fiber Protects against Diet-Induced Microbiota-Mediated Colonic Mucus Deterioration. Cell Host Microbe. 2018;23(1):27-40.e7. (PubMed)
  11. Mackie A, et al. Increasing dietary oat fibre decreases the permeability of intestinal mucus. J Funct Foods. 2016;26:418–427. (PubMed)
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  13. Desai MS, et al. A Dietary Fiber-Deprived Gut Microbiota Degrades the Colonic Mucus Barrier and Enhances Pathogen Susceptibility. Cell. 2016;167(5):1339-1353.e21. (PubMed)
  14. Kirpich IA, et al. Ethanol and Dietary Unsaturated Fat (Corn Oil/Linoleic Acid Enriched) Cause Intestinal Inflammation and Impaired Intestinal Barrier Defense in Mice Chronically Fed Alcohol. Alcohol. 2013;47(3):257–264. (PubMed)
  15. Pigrau M, et al. The joint power of sex and stress to modulate brain-gut-microbiota axis and intestinal barrier homeostasis: Implications for irritable bowel syndrome. Neurogastroenterol Motil. 2016;28(4):463–486. (PubMed)
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  17. Da Silva S, et al. Stress disrupts intestinal mucus barrier in rats via mucin O-glycosylation shift: prevention by a probiotic treatment. Am J Physiol Gastrointest Liver Physiol. 2014;307(4):G420–429. (PubMed)
  18. Branca JJV, et al. Intestinal epithelial barrier functions in ageing. Ageing Res Rev. 2019;54:100938. (PubMed)
  19. He Y, et al. Intervention mechanism of repeated oral GABA administration on anxiety-like behaviors induced by emotional stress in rats. Psychiatry Res. 2019;271:649–657. (PubMed)
  20. Jakobsson HE, et al. The composition of the gut microbiota shapes the colon mucus barrier. EMBO Rep. 2015;16(2):164–177. (PubMed)
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  22. Kankainen M, et al. Comparative genomic analysis of Lactobacillus rhamnosus GG reveals pili containing a human-mucus binding protein. Proc Natl Acad Sci U S A. 2009;106(40):17193–17198. (PubMed)
  23. Von Ossowski I, et al. Mucosal adhesion properties of the probiotic Lactobacillus rhamnosus GG SpaCBA and SpaFED pilin subunits. Appl Environ Microbiol. 2010;76(7):2049–2057. (PubMed)
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