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Although inflammatory bowel disease tends to run in families, diet and intestinal flora also play an important role. A diet low in fiber leads to an increase in special bacteria that break down the intestinal mucosa and promote inflammatory bowel diseases.
A new study involving experts from the University of Michigan examined possible mechanisms by which diet and gut bacteria, combined with genetics, may promote inflammatory bowel disease. The results can be read in the specialist journal “Cell Host & Microbe”.
Influence of diet & intestinal flora
Although it is already known that inflammatory bowel disease (IBD) has a genetic component, not all people with a family history of the condition develop the disease. This shows that other factors also play a role, the researchers explain.
It is therefore assumed that diet and intestinal flora also have an important influence on the development of inflammatory bowel diseases. The new study was intended to identify possible underlying mechanisms.
Very complex interaction
In fact, the team has discovered a very complex interplay between diet, genes and intestinal flora that could explain why inflammatory bowel disease occurs.
The new research builds on previous studies that showed that a low-fiber diet contributes to the proliferation of bacteria that feed on intestinal mucus.
Genetic loss of a protein called interleukin-10 (IL-10), which influences the immune system, or its receptor can lead to an early onset of inflammatory bowel disease in infants and children, the researchers report.
A diet low in fiber increases risk
Using mice with the same immune changes, the team now examined the influence of intestinal flora and diet on the risk of disease. Some animals spontaneously developed inflammation in the intestinal tract, but the severity varied and appeared to be exacerbated by the presence of certain bacteria and a low-fiber diet, the researchers explain.
The team found that mice bred without bacteria showed no signs of inflammatory bowel disease. And by adjusting the presence or absence of a model human gut microbiome and the fiber content of the diet, the researchers were able to increase or decrease inflammation.
Connection with intestinal bacteria
The experts also found that the inflammation caused by a fiber-free diet appears to increase in response to the increased presence of the mucus-breaking bacteria Akkermansia mucinphila and Bacteroides caccae.
“These bacteria begin searching for nutrients in the mucus layer, reducing its thickness and barrier function and bringing the microbes just 10-100 micrometers closer to the host tissue. In the mice with IBD genetics, that was enough to make them sick,” reports study author Professor Dr. Eric Martens in a press release.
Fiber against inflammation?
On the other hand, if the mice received a diet rich in fiber, this prevented the inflammation. According to the team, when the animals were switched from a low-fiber to a high-fiber diet, there was a peak in inflammation, which was followed by a significant decrease.
According to experts, this suggests that fiber can reverse the harmful effect of mucus erosion on inflammation. However, inflammatory bowel disease is often treated with a so-called exclusive enteral diet, which contains no fiber.
Despite the lack of fiber, this treatment leads to a decrease in inflammation in humans for reasons that are still unclear, the team reports.
Isobutyrate suppresses inflammation
In further experiments with mice, the team finally identified the branched-chain fatty acid isobutyrate. This was present in increased amounts in animals that received enteral nutrition and suppressed inflammation. Isobutyrate is produced by fermentation of certain bacteria in the intestines.
“It appears that one of the ways in which this exclusive enteral nutrition could work in humans is by stimulating certain bacteria to produce useful metabolites,” said Professor Dr. Martens.
Further studies will now investigate how diet and bacteria interact in order to improve therapies for inflammatory bowel diseases and to find out how the onset of these diseases can be prevented by manipulating the triggering factors. (as)