I have talked about impaired tight junctions in the intestinal epithelial lining (i.e. leaky gut) many times on this blog. (Look here and here, for just two examples.) We know this is a factor in diseases ranging from Parkinson’s to autism to Celiac disease to inflammatory bowel diseases, and many more. Leaky gut is both the cause and the result of intestinal inflammation. Protein complexes (i.e. tight junctions (TJ)) are supposed to bind adjacent cells together to prevent toxins, microorganisms, undigested food, and so forth from getting out of the intestine into the blood stream. When inflammation is present, these tight junctions open, compromising the health of the organism and leading to further inflammation.
Currently there is no accepted treatment for leaky gut, but research has begun to focus on finding probiotic species that can reduce intestinal wall inflammation, and tighten those junctions. A study has come out of Penn State College of medicine on this very topic: “The major aim of the present study was to identify probiotic bacteria able to produce a rapid and marked enhancement of intestinal TJ barrier function that can treat intestinal inflammation by targeting the TJ barrier.”[i] These researchers screened more than 20 different bacterial species to find one that could tighten up junctions between epithelial cells, testing this in vitro. Their results: only 1 strain (LA1) of Lactobacillus acidophilus clearly did so. Says the lead researcher, “Our data indicate that LA1 is able to prevent colonic inflammation formation and promote colitis healing…”[ii]
The bacteria appear to work by activating a protein in the cellular membrane called toll-like receptors, which are a part of the immune system. This activation caused the cells to tighten their junctions. Unlike the research out of Wake Forest University which I talked about in this post, this activation required live bacterial/epithelial cell interaction: i.e. heat-killed bacteria, for example, had no effect. The researchers then tested this strain in mice, and it rapidly improved epithelial barrier integrity and protected the mice against chemically-induced colitis. The strain also promoted healing in mice with colitis: “…our studies indicate that LA1 causes a strain-specific, rapid enhancement of intestinal epithelial TJ barrier function. The LA1 enhancement and maintenance of the intestinal epithelial barrier were required for the prevention of DSS-induced colitis and for accelerated healing of the colitis.” The researchers hope to conduct human trials in the near future.
I can’t figure out if this particular strain, LA1, is available commercially. In looking for it though, I stumbled across an article from 1997 which tested this particular Lactobacillus strain, in vitro, in fighting against a variety of pathogens, including Staph, Klebsiella, Listeria, etc.: “We present evidence that the spent culture supernatant of strain LA1 (LA1-SCS) contained antibacterial components.”[iii] I’d love to figure out if it’s in any currently available probiotics! If anyone does find it commercially available, let the rest of us know!
[i] Al-Sadi, R, Nighot, P, Nighot, M, Haque, M, Rawat, M, Ma, TY. Lactobacillus acidophilus induces a strain-specific and toll-like receptor 2-dependent enhancement of intestinal epithelial tight junction barrier and protection against intestinal inflammation. The American Journal of pathology. 2021. DOI:https://doi.org/10.1016/j.ajpath.2021.02.003
[iii] Bernet-Camard MF, Liévin V, Brassart D, Neeser JR, Servin AL, Hudault S. The human Lactobacillus acidophilus strain LA1 secretes a nonbacteriocin antibacterial substance(s) active in vitro and in vivo. Appl Environ Microbiol. 1997;63(7):2747-2753. doi:10.1128/AEM.63.7.2747-2753.1997.