The gel lets in nutrients and largely blocks out bacteria, preventing infections. It also regulates how some drugs are delivered elsewhere in our bodies.
Researchers had previously studied how the gel can be damaged, for instance when bacteria feed on the gut’s lining. The new study is the first to look at the structure of the gel and how it morphs in the presence of other substances naturally found in the gut.
Performing their experiments in mice, researchers tested the effects of polymers, which include dietary fiber as well as therapeutics such as medicines for constipation. The researchers fed some mice a diet rich in polymers and others (the controls) a polymer-free diet.
Apple a day?
Using a technique called confocal reflectance microscopy they measured the thickness of the gut gel and the degree to which the gel was compressed as a result of the consumed polymers. Mice given a high-polymer diet, they found, had a more compressed gel layer.
“The gel is like a sponge with holes that let material through,” says the paper’s lead author, Sujit Datta, a postdoctoral scholar at the California Institute of Technology. “We are seeing that polymers, including dietary fiber, can compress the gel, potentially making the holes smaller, and we think that this might offer protective benefits.”
In addition, the researchers applied different kinds of polymers—including dietary fibers like pectin, found in apples—directly to the gel lining to test its response. All of the polymers tested compressed the gel layer.
“It’s too early to draw any conclusions, but it may be that eating an apple a day will affect the shape of the lining in your gut,” says Asher Preska Steinberg, a Caltech graduate student and coauthor of the study published in the Proceedings of the National Academy of Sciences.
The researchers also found that dietary fiber and gut bacteria—which are part of a community of microorganisms collectively known as gut microbiota—can work together to influence how the gut gel changes shape.
They performed the same polymer/fiber experiments in germ-free mice, which are mice carefully raised to not have any bacteria in their gut. The results showed that the polymers compressed the gut gels of these germ-free mice to a greater degree. This implies that species of bacteria in our gut that are known to break down polymers can weaken the compressing effect.
“We previously thought of the gel as a static structure, so it was unexpected to find an interplay between diet and gut microbiota that rapidly and dynamically changes the biological structures that protect a host,” says Rustem Ismagilov, a professor of chemistry and chemical engineering.
“Our study gives biologists and scientists studying diseases of the gut something else to think about,” says Datta. “Now they can take the structure of the gut mucus, and how it responds to its environment, into account.”
The Defense Advanced Research Projects Agency (DARPA) and National Science Foundation (NSF) funded the work.
Source: Caltech, CC by 4.0,,