High-fiber diet protects against dangerous intestinal infections

High-fiber diet protects against dangerous intestinal infections

A study published in the journalCell host & microbeBrazilian and American researchers suggest that a diet rich in soluble fiber can protect the intestines from pathogenic bacteria.

The conclusion is based on experiments with miceClostridioides difficilewhich causes colon inflammation and diarrhea and affects about 500,000 people per year in the United States.

"We were able to treat the mice with a diet supplemented with soluble fiber. This is digested by the intestinal microbiota, which produces compounds such as acetate. This leads to a cascade of interactions that leads to an appropriate immune response to the agreement with the infection by José Fachi studies in the infection. Louis, United States.

The work was a collaboration between the institution and the State University of Campinas (UNICAMP) in Brazil. The authors observed that the mice that consumed a diet rich in soluble fiber produced more acetate in the intestines. This increase has regulated the immune response in the layer that covers the inner wall of the organ, called the epithelium, making it effective in fighting theC. difficileBacteria.

Acetate is a short-chain fatty acid produced by the digestion of soluble fiber, a process carried out by the bacteria living in the intestines.

In the study, mice fed a low-fiber diet produced little acetate. As a result, the expression of components of the so-called major histocompatibility complex class 2 (MHC-II) was increased in the intestinal epithelium. Although MHC-II is an essential molecule in defense against infection, its excessive production can cause exaggerated inflammation, which damages tissue and worsens the patient's condition.

It is a similar effect to severe Covid-19, when the immune response itself leads to tissue destruction and even death. In our study, soluble fiber consumption regulated this response. “

Sarah de Oliveira, PhD student at Unicamp’s Institute of Biology (IB) and co-author of the article

Oliveira conducted the work during a research internship at Washington University with support from Fapesp.

The work is part of the project “Analysis of the molecular mechanisms involved in the interaction of microbiota metabolites and host cells during inflammation”, funded by FAPESP and coordinated by Marco Vinolo, professor at IB-Unicamp.

Vinolo supervised Oliveira's doctoral research and advised Fachi, who also received a fellowship.

Dangerous bacteria

Usually acquired from elderly hospital patients treated with antibiotics,C. difficileInfection leads to severe diarrhea, which can lead to sepsis (generalized infection) and even death.

Many strains are resistant to existing drugs, making treatment difficult. In Brazil, studies on this topic are scarce, partly due to the limited availability of testing, particularly in the public health system.

In the animals treated in the study with a diet low in fiber and therefore low in acetate production, the immune response was exacerbated. The epithelial cells overproduce MHC-II, which has the function of presenting pathogen molecules (antigens) to activate CD4+ T lymphocytes, which are responsible for fighting the infection.

Among these defense cells, intraepithelial lymphocytes (IELs) became too active and began to fill more inflammatory mediators such as gamma-type interferon. The excess of these molecules increases inflammation, leads to severe tissue damage and worsens the overall condition of the host, which can lead to death.

Using the results of the mouse tests, the researchers analyzed biopsies from infected patientsC. difficile. As with animals, the most severe cases had a higher presence of MHC-II and CD4+ T lymphocytes than the less severe cases.

“The study provides a broader understanding of the role of dietary fiber in the immune system. Although we’ve already shown the relationship between the production of short-chain fatty acids and immunity in other studies, this time we were able to demonstrate an unprecedented and coordinated event between the microbiota, the epithelium and the immune cells in the fight against infection,” comments Vinolo, who coordinated the work with Marco Colonna of Washington University in Saint Louis (Find more information).

The authors emphasize the importance of a high-fiber diet for intestinal health. The soluble fiber found in foods such as fruits, vegetables, legumes and whole grainsC. difficile.

“Simple food choices, such as including more fiber in the diet, can make a significant difference in protecting against intestinal infections,” concludes Fachi.

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