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Dietary fiber protects from bronchiolitis-causing viral infection

Research was conducted in animal models by a doctoral student at PUCRS

09/10/2019 - 11h02
2019_10_01-BronquioliteMyriam-ZillesPixabay908X617-

Photo: Myriam Zilles/Pixabay

A study recently published in  Nature Communications Journal showed that a high-fiber diet protects against severe respiratory syncytial virus (RSV) infection, a major cause of bronchiolitis in children under two years of age. There are currently no treatments or preventive measures to address this disease. The research, conducted in mice, is part of the doctoral work developed by Krist Antunes, a doctoral candidate at PUCRS’ Graduate Program in Pediatrics and Child Health, under the supervision of PUCRS professor Ana Paula Souza, with the collaboration of professors Renato Stein (PUCRS) and Marco Vinolo (Unicamp), as well as associate researchers from Argentina and the United States.

Once ingested, fibers cause the production of short-chain fatty acids in the intestine, mainly acetate, propionate and butyrate. In one preventive experiment, the researchers added acetate to the drinking water of the mice for three weeks and then infected the animals with RSV. In another test, considered therapeutic, they first infected the rodent with the virus and then gave it water with acetate as treatment. In both cases, both in prevention and treatment, there was a decrease in viral load and viral symptoms, such as weight loss and lung inflammation.

The researchers also performed the experiment directly with fibers, including them in animal feed. Similarly, the results were very positive in protecting animals from virus infection. A high-carbohydrate diet with zero fiber was also used in tests: “Interestingly, the animal submitted to the zero-fiber diet got much worse; its symptoms were far more severe than the ones of those who were fed the control diet,” says Antunes.  “This is the first time this mechanism is described:  acetate, a substance that our own microbiota produces, protects us by mediating an antiviral response against a respiratory infection. This is the great news of the study,” says Souza.

Baby Data Collection

A second phase of the study evaluated the level of short-chain fatty acids in the stool of infants under one year of age with RSV infection admitted at PUCRS São Lucas Hospital. Preliminary results showed that children with less short-chain fatty acids in their stool stay in hospital longer and need oxygen support for longer periods as well. “This data tells us that babies with the most severe bronchiolitis symptoms have lower levels of these fatty acids in their bodies,” confirms Souza.

Impact of Changing Dietary Patterns of Brazilians              

Antunes notes that the Brazilian dietary pattern is much changed, and that fiber consumption is a lot lower: “The guidelines say that we must consume 25 grams per day and the average Brazilian person consumes only 15 grams.” She warns that soluble dietary fibers, which lead to the production of acetate, are present in fruits such as apple (especially in the peel) and orange (mostly in the white part).

Next steps

For research to begin and to be carried out in humans, many steps are still needed, such as studies of safety data and protocols, demanding both time and financial support. Renato Stein, who is also a Pediatric Pneumologist, says that the intention going forward is to research means of protection for pregnant women, since RSV mainly affects infants: “We want to know if changing a pregnant woman’s diet or giving her a dietary supplement that increases short-chain fatty acid levels will benefit the baby,” he says. The first tests will be performed on animal models.