Several factors influence the composition of the intestinal microbiota, including nutrition and the body’s production of intestinal defense molecule defenses, researchers at the University of Ume in Sweden discovered. Instead, they found a possible function for these molecules in stopping blood sugar levels from rising after eating a high-calorie “Western-style diet.”
“Although defenses have little effect in shaping the composition of adult microbes compared to diet, defenses still play a very important role in protecting us from microbial infections; and our research highlights its protective role against the metabolic complications that may arise after the intake of a high-fat and high-sugar Western-style diet,” said Fabiola Puertolas Balint, son PhD student in the Department of molecular biology at Umea University.
She works in Bjorn Schroder’s research group, which is also affiliated with the Umea Center for Microbial Research, UCMR, and the Swedish Molecular Infectious Medicine Laboratory, MIMS, at Umea University.
The gut microbiota refers to the community of trillions of microorganisms that live within each person’s gut. Over the past decades, the abundance of specific bacteria in this community has been extensively studied for 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, among others, diet (especially fiber), genetics, medications, exercise, and defense molecules, the so-called antimicrobial peptides.
Antimicrobial peptides can be seen as the body’s own natural antibiotic molecules. In particular, the largest group of antimicrobial peptides – the defenders – are produced by all body surfaces, including the skin, lungs and gastrointestinal tract. They are considered to be the first line of defense of the immune system against infections but at the same time they are also thought to be necessary to shape the microbiota composition in the small intestine. However, it was not clear until now how large their effect was compared to diet, which is known to have a large effect.
To investigate this, researchers from Bjorn Schroder’s lab used normal healthy mice and compared their microbiota composition in the small intestine to mice that were unable to produce functional defenses in the gut, and then both groups of mice were fed a diet healthy or low-. western style dietary fiber.
“When we analyzed the composition of microbiota inside the gut and at the gut wall of two different regions in the small intestine, we were surprised – and a little disappointed – that defensins had only a very small effect on shaping the overall composition of the microbiota,” a said Bjorn Schroder.
However, the intestinal protectors still had some effect directly at the gut wall, where the protectors are produced and released. Here, a few specific bacteria, including Dubosiella and Bifidobacteria, appeared to be affected by the presence of the protectants, probably due to the selective antimicrobial activity of the protectants.
“To our surprise, we also found that the combination of eating a Western-style diet and a lack of functional defense increased fasting blood glucose values, indicating that defenders may help protect against metabolic disorders when eating an unhealthy diet,” said Bjorn Schroder.
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