High-fiber Diet May Help Control COVID-19 Related Inflammation

Study shows that gut microbiota produced compounds during fermentation of insoluble fiber from dietary plant matter doesn’t affect the ability of the coronavirus to enter and replicate in cells lining the intestines. But, in vitro treatment ofcells with these molecules reduces the expression of a gene that plays a key role in viral cell entry and a cytokine receptor that favors inflammation. Up to 50% of COVID-19 patients (17.6% of severe cases) experience gastrointestinal symptoms like diarrhea, vomiting, and abdominal pain. Studies have found major changes in patients' gut microbiota, including a decrease in levels of bacteria that secrete short-chain fatty acids (SCFAs) by fermenting dietary fiber, which is important for colon health and maintenance of intestinal barrier integrity.

Patricia Brito, first author, said, “In earlier research, we found in animals that compounds produced by gut microbiota help protect the organism against respiratory infection. The model used respiratory syncytial virus [RSV], which causes bronchiolitis [inflammation of the small airways in the lung] and frequently infects children. Similar results have been obtained by other research groups in studies of different respiratory diseases.”

The researchers infected healthy colon tissue and epithelial cells from 11 patients with coronavirus in the laboratory and subjected them to a battery of tests. The tissues and cells were treated with a mixture of acetate, propionate, and butyrate, compounds produced by gut microbiota metabolization of SCFAs present in dietary fiber. This did not alter viral load in colon biopsies or cells, nor were there any cell wall permeability and integrity changes.

Raquel Franco Leal, co-principal investigator, explained, “Viral load wasn’t reduced and was the same in cells and tissue treated with SCFAs and in untreated samples. However, treated intestinal biopsy samples displayed a significant decrease in the gene DDX58 and the interferon-lambda receptor, which mediates antiviral activity. There was also a decrease in expression of the protein TMPRSS2, which is important to viral cell entry.”

“That doesn’t exclude the possibility of significant action by SCFAs on infection by SARS-CoV-2. The antiviral effects could depend on interaction with other cells in the organism,” Rodrigues said.

Other tests involving non-treated infected biopsy samples showed an increase in expression of DDX58 and interferon-beta (IFN-beta).

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DDX58 is an innate immune system receptor that detects viral nucleic acids and activates a signal that results in the production of proinflammatory cytokines. IFN-beta is a proinflammatory molecule that participates in the cytokine storm associated with severe cases of COVID-19.

“Alterations in genes associated with virus recognition and response during intestinal infection may be relevant to the onset of the inflammatory chain,” Leal said. “In this context, it will be important to deepen the analysis of the effects of SCFAs with these parameters, as this could be significant in severe stages of the disease.”

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Source-Medindia