Newswise — Scientists at Umeå University in Sweden discovered that diet has a bigger effect on the type of bacteria found in the gut than the body's defense molecules, called defensins. However, they found that defensins may play a role in preventing high blood sugar levels after eating a high-calorie "Western-style" diet.
According to Fabiola Puértolas Balint, a PhD student at Umeå University, while diet has a greater impact on the type of bacteria in our gut compared to defensins, these defense molecules are still essential for protecting us from infections caused by harmful microbes. Additionally, the research conducted shows that defensins may also help prevent health problems that can arise from consuming a high-fat and high-sugar Western-style diet.
Fabiola Puértolas Balint works in a research group led by Björn Schröder at Umeå University. The research group is associated with Umeå Centre of Microbial Research (UCMR) and The Laboratory for Molecular Infection Medicine Sweden (MIMS).
The gut microbiota is a group of many tiny living things that reside inside the digestive system of every person. Researchers have extensively studied the abundance of specific bacteria in this community over the past few decades, as they are linked to several diseases like inflammatory bowel diseases, obesity, diabetes, and even psychological disorders. The gut microbiota is established when a person is born, and its composition is shaped by various internal and external factors like diet (especially fibre), genetics, medication, exercise, and defense molecules called antimicrobial peptides.
Antimicrobial peptides are naturally occurring molecules in the body that act like antibiotics. The largest group of these peptides is called defensins, and they are produced by all surfaces of the body, including the skin, lungs, and gastrointestinal tract. Defensins are the first line of defense against infections and are also believed to play a role in shaping the composition of the microbiota in the small intestine. However, it was previously unknown how significant their effect was compared to diet, which is known to have a major impact on the microbiota.
To study the impact of defensins and diet on the microbiota, researchers from Björn Schröder's lab conducted an experiment using two groups of mice. The first group of normal, healthy mice was compared to a second group of mice that couldn't produce functional defensins in their gut. Both groups of mice were then given either a healthy diet or a low-fiber Western-style diet, and their microbiota compositions in the small intestine were compared.
Björn Schröder stated that after analyzing the microbiota composition in the gut and the gut wall of two different regions in the small intestine, they were surprised and somewhat disappointed to find that defensins had only a minor impact on the overall microbiota composition.
Even though defensins had only a minor impact on the overall microbiota composition, they still had a direct effect at the gut wall where they are produced and secreted. At this location, the presence of defensins seemed to affect a few specific bacteria, including Dubosiella and Bifidobacteria, likely due to the selective antimicrobial activity of the defensins.
“To our surprise, we also found that the combination of eating a Western-style diet and lacking functional defensins led to increased fasting blood glucose values, which indicated that defensins may help to protect against metabolic disorders when eating an unhealthy diet,” says Björn Schröder.
The study suggests that strategies to improve the microbiota composition should primarily focus on diet rather than increasing the production of host defense molecules such as defensins, as the latter may have only a minor impact on the overall composition. However, during early stages of life when the microbiota community is not fully matured, defensins may have a stronger effect on the microbial composition. Nonetheless, increasing the production of defensins could be a useful option to prevent the development of metabolic disorders.
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