Diet has a much stronger impact on gut microbiota than defensins

Researchers from Umeå University in Sweden have found that of the many factors that shape the composition of the gut microbiota, diet has a much stronger impact than defensins, which are gut defense molecules produced by the organism. Instead, they identified a possible role for these molecules in preventing blood sugar levels from rising after consuming a high-calorie “Western diet.”

Although the effect of defensins on the formation of the composition of adult microbiota is rather minor compared to diet, defensins still play a very important role in the protection against microbial infections; and our research highlights their protective role against metabolic complications that can occur after taking a Western diet high in fat and sugar.”

Fabiola Puértolas Balint, PhD student in the Department of Molecular Biology at Umeå University

She works in Björn Schröder’s research group, which is also affiliated with the Umeå Center for Microbial Research, UCMR, and the Molecular Infection Medicine Laboratory Sweden, MIMS, at Umeå University.

Gut microbiota refers to the community of trillions of microorganisms that live inside everyone’s gut. Over the past few decades, the abundance of specific bacteria in this community has been widely studied due to its link to many diseases, including inflammatory bowel disease, obesity and diabetes, and even psychological disorders. . The microbial community is seeded at birth, after which several internal and external factors help shape the community to its final composition. These factors include, but are not limited to, diet (especially fiber), genetics, medications, exercise, and defense molecules, so-called antimicrobial peptides.

Antimicrobial peptides can be thought of as antibiotic molecules naturally produced by the body. In particular, the largest group of antimicrobial peptides – the defensins – are produced by all body surfaces, including the skin, lungs and gastrointestinal tract. Defensins are considered the first line of defense of the immune system against infections, but at the same time they are also considered essential in shaping the composition of the microbiota in the small intestine. However, it was not clear until now how big of an effect they were in relation to diet, which is known to have a major impact.

To investigate this, researchers from the Björn Schröder lab used normal healthy mice and compared the composition of their microbiota in the small intestine to mice that could not produce functional defensins in the intestine, and then both groups of mice were fed either a healthy diet or a low-grade western-style diet.
“When we analyzed the composition of the microbiota inside the intestine and at the level of the intestinal wall of two different regions of the small intestine, we were surprised – and slightly disappointed – that defensins had no only a very minor effect on the formation of the overall composition of the microbiota,” says Björn. Schroder.
However, intestinal defensins still had some effect directly on the intestinal wall, where defensins are produced and secreted. Here, a few distinct bacteria appeared to be affected by the presence of defensins, including Dubosiella And Bifidobacteriaprobably due to the selective antimicrobial activity of defensins.

“To our surprise, we also found that the combination of a Western-style diet and a lack of functional defensins resulted in increased fasting blood glucose values, indicating that defensins may help protect against metabolic disorders when eating an unhealthy diet,” says Björn. Schroder.
The results suggest that strategies to positively modulate microbiota composition should instead focus on diet, as modulating composition via increased production of host defense molecules, such as defensins, may not have only a small impact on the overall composition. However, it is possible that, especially in early life, when the microbiota community is not yet fully mature, defensins have a greater effect on microbial composition. However, increasing the production of defensins can be an interesting option to prevent the development of metabolic disorders.

The results were published in the scientific journal Microbiology Spectrum.