Alterations in the Bacterial Microbiome Associated with Ankylosing Spondylitis: A Larger and Confirming Study

My long time readers know that at this time of year, I typically review my favorite stories from the prior year but I was so darn busy this holiday season, I simply did not have the time this past week.  I will try to do so as a throw-back Thursday present this week.

In the meantime, I know that one of the most read posts of 2019 was the one I wrote on April 11th about a small study that showed that those with Ankylosing spondylitis (AS) have distinct bacterial and fungal microbiome differences from healthy controls:  “The study included 22 patients with  AS and 16 healthy controls (HC).  They found major differences in the bacterial microbiomes between the two groups, including a ‘significant increase’ in diversity in the AS group that included a nearly 3-fold increase in Proteobacteria and a decrease in Bacteroidetes species, including Prevotella.” The researchers also noted that the fungal microbiome was depleted in those with AS, in relation to the bacterial:  that is, the ratio of bacteria to fungi is off.  And the severity of disease completely coincided with the degree of alteration to the bacterial microbiome.

That study though was on only 22 patients.  Obviously, the results needed to be replicated with a larger cohort, and I am happy to announce that a new study has done just that.  Researchers at a Swedish University evaluated the fecal microbiota in 150 patients with AS, and compared them to patients with ulcerative colitis and healthy controls over a 5 year period of time.  Like the earlier, smaller study, they also assessed inflammation levels.[i]

Sure enough, “…the fecal microbiota in AS was characterized by a higher abundance of Proteobacteria, Enterobacteriaceae, Bacilli and Streptococcus species, as well as Actinobacteria, but lower abundance of Bacteroides and Lachnospiraceae.”[ii]  Notice that these results somewhat parallel the earlier smaller study:  a higher level of Proteobacteria, a decrease in Bacteroidetes.

One other interesting finding in this study:  the scientists also measured calprotectin, a marker for intestinal inflammation.  Those individuals with dysbiosis, including lower levels of anti-inflammatory bacteria and higher levels of Streptococcus, had higher levels of calprotectin in their feces.  As 87% of those with AS in the study suffered from dysbiosis, the researchers conclude that intestinal inflammation is common in the disease.

Which leads me to a few points that I never knew about AS.  Yes, I knew that gut issues are commonly found alongside AS, but here are a few facts I did NOT know:

  1. “AS is characterized by microscopic intestinal inflammation, which has been demonstrated in 40–60% of the patients.”
  2. “AS patients also have an increased risk of developing IBD, especially CD.”
  3. “Interleukin (IL) 23 and IL17, which are key cytokines in AS, are produced in the inflamed gut, both in AS and in IBD.”

What to do about it, no one yet knows, just as is the case with all these inflammatory illnesses that seem to originate in the gut.  I did point out, in my first ever post about AS, that in one 2007 study, patients with AS were given Moxifloxacin, an antibiotic and that this “…resulted in a significant and sustained improvement…”  on top of reducing inflammation.  I haven’t found any kind of follow up on that though.

Spondyloartropathies are incredibly common, as I’ve pointed out before – way more common than Parkison’s, MS, and other much better known diseases.  As so many of you seem interested in this topic, I most certainly I will continue to watch out for any new information.

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[i] Klingberg, E, et. al. A distinct gut microbiota composition in patients with ankylosing spondylitis is associated with increased fecal calprotectin.  Arthritis Research & Therapy. 2019.  doi:10.1186/s13075-019-2018-4.

[ii] https://www.healio.com/rheumatology/spondyloarthropathies/news/online/%7B47729d65-828c-4471-83d5-ec097ab7508a%7D/patients-with-ankylosing-spondylitis-display-distinct-fecal-microbiota-signature

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