IBS
Turning to functional bowel disorders, Dr. Kelly pointed out a new study examining FMT for IBS. “So far, the research has been pretty disappointing,” she noted. The study, presented by Prashant Singh, MBBS, a gastroenterology fellow at Beth Israel Deaconess Medical Center, Boston, examined FMT for patients with moderate to severe diarrhea-predominant IBS. The study had four arms, randomizing the 44 participants to FMT alone; pretreatment with metronidazole and ciprofloxacin or rifaximin, each followed by FMT; or placebo. “It really didn’t show any differences in their severity of IBS in any group; so no effect: a negative study,” said Dr. Kelly.
“It’s challenging. FMT is an appealing strategy because we don’t have to put a lot of thought process into it,” said Dr. Kashyap, but it’s no panacea. “We aren’t going to be able to treat everybody with FMT.
“The challenge with IBS is that if we look at all the compositional studies, the majority of them show that at least a big subset of patients with IBS already have a normal-appearing microbiome,” said Dr. Kashyap. In those patients, “It’s very hard to know what FMT is doing.” He noted that IBS subclassifications are made by pathophysiology, without regard to the intestinal microbiome, so these classifications may not be useful for determining who may benefit from FMT.
“Again, there’s always an opportunity to learn from these studies,” whether they’re positive or negative, as long as they’re well done, said Dr. Kashyap. “There’s always an opportunity to go back and see, was there a specific subgroup of patients who responded, where there might be one or more causes which might be more amenable” to FMT.
Small intestine
And most intestinal microbial research to date, noted Dr. Kelly, has focused on the colon. “Most of our knowledge is of fecal microbiota.” New techniques including double-balloon enteroscopy of the small bowel have promise to “provide completely new information about patterns of bacteria throughout the small bowel,” and of the role of small bowel bacteria in overall gut health, she said.
“The role of the small bowel has been ignored because of accessibility,” agreed Dr. Kashyap. There’s a current focus on research into enteroscopy and other techniques to sample small intestine microbiota, he said.
In a podium presentation, Eugene Chang, MD, Martin Boyer Professor in the University of Chicago’s department of medicine, gave a broad overview of how the small intestine microbiome modulates lipid regulation. This choice of topic for the Charles M. Mansbach Memorial Lecture shows that gastroenterologists are recognizing the importance of microbiome along the entire span of the gut, said Dr. Kashyap. Dr. Chang’s approach, he added, represents a departure in that “it’s not simply just looking at what’s present and what’s not, but seeing what’s functionally relevant to metabolism.”
“We always have known that the small intestine is the workhorse; that’s where everything happens” in terms of motility, absorption, and digestion, said Dr. Kashyap. “But because of our inability to reach it easily we’ve always chosen to ignore it; we always go after the low-hanging fruit.” Despite challenges, more microbiome research should be small-bowel focused. “Eventually, it’s no pain, no gain.”
Dr. Kashyap is on the advisory board of uBiome, and is an ad hoc advisory board member for Salix Pharmaceuticals. Dr. Kelly reported no conflicts of interest.
This story was updated on July 30, 2019.
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