New Delhi: According to researchers, a type of dietary fiber called inulin, which is used in health supplements and has some anti-inflammatory properties, may promote allergy-related types of inflammation in the lungs and gut, As well as in other parts of the body. ,
Researchers from the Friedman Center for Nutrition and Inflammation and the Jill Roberts Institute for Inflammatory Bowel Disease in Weill Cornell Medicine and the Boyce Thompson Institute on Cornell’s Ithaca Campus published their findings in the journal Nature.
The study found that dietary inulin fiber alters the metabolism of certain gut bacteria, which in turn triggers what scientists call type 2 inflammation in the gut and lungs. This type of inflammation is believed to have evolved in mammals primarily to protect against parasitic worm (“helminth”) infection, and is also part of normal wound-healing, although its inappropriate activation is associated with allergies, asthma and other inflammations. Reduces related diseases.
The study’s co-senior authors are Dr. David Artis, director of the Friedman Center for Nutrition and Inflammation, and the Michael Kors Weill Professor of Immunology at Cornell Medicine.
The study’s scientific participants reflect the Friedman Center’s highly cross-collaborative research mission, drawing on expertise in bacterial genetics, biochemistry and immunology at Weill Cornell Medicine in New York City and Cornell’s Ithaca campus. Dr. Chun-jun Guo, assistant professor of immunology in medicine at Weill Cornell Medicine, and Dr. Frank Schroeder, a professor at the Boyce Thompson Institute and the Ithaca campus in the Department of Chemistry and Chemical Biology in Cornell’s College of Arts and Sciences, collaborated with the Artis laboratory to gain a detailed understanding of how an important dietary component affects the microbiome and immune response. does. The first author of the study is Dr. Mohammad Arifuzzaman, a postdoctoral researcher in the Artis laboratory. Artis Weill is also director of the Jill Roberts Institute for Inflammatory Bowel Disease at Cornell Medicine.
Small amounts of insulin are present in a variety of fruits and vegetables, including bananas, asparagus and garlic. It is also often concentrated in commonly available high-fiber dietary supplements. Previous studies have found that inulin increases the population of beneficial gut bacteria species which in turn boosts the levels of anti-inflammatory immune cells called regulatory T (Treg) cells. In this new study, the researchers examined the effects of inulin more broadly. They fed mice an insulin-based, high-fiber diet for two weeks, and then analyzed the many differences between these mice and mice that were fed an insulin-deficient diet. One major difference was that the inulin diet, while increasing Treg cells, also induced higher levels of white blood cells called eosinophils in the gut and lungs. A high level of eosinophils is a classic sign of type 2 inflammation and is commonly seen in seasonal allergies and asthma.
Researchers eventually found that the eosinophil response was mediated by immune cells called group 2 innate lymphoid cells (ILC2s), which were activated by elevated levels of small molecules called bile acids in the blood. Elevated levels of bile acids were caused by the inulin-induced growth of certain bacterial species—a group called bacteria found in both mice and humans—that contain a bile acid-metabolizing enzyme.
“We were amazed to find such a strong association between inulin supplementation and increased bile acid levels,” said Dr. Schroeder. “We then found that deletion of the bile acid receptor abolishes inulin-induced inflammation, suggesting that microbiota-driven changes in bile acid metabolism underlie the effects of inulin.”
“When we colonized germ-free mice (mice without the microbiota) with one of these bacterial species, and then knocked down the gene for a bacterial enzyme that promotes bile acid production, insulin-induced eosinophilia and allergic reactions occurred. The entire path leading up to the inflammation was blocked,” Dr. Guo said.
While insulin promotes type 2 inflammation, the researchers said, that doesn’t mean this type of fiber is always “bad.” They found that inulin worsened allergen-induced type 2 airway inflammation in mice. But the experiments also confirmed the previously reported effect of inulin in promoting anti-inflammatory Treg cells, which, in many cases, may outweigh some of the pro-inflammatory effects. Furthermore, a type 2 immune response, which involves an increased production of tissue-protecting mucus in the gut and lungs, is not necessarily harmful to healthy people—in fact, the researchers found in their mouse experiments that insulin- Induced type 2 inflammation enhances defense against helminth infection.
“It may be that this inulin endemic to the type-2-inflammation pathway represents an adaptive, beneficial response to helminth parasite infection, although in more industrialized, helminth-free environments its effects are more complex and difficult to predict.” are,” Dr. Arifuzzaman.
The researchers now plan to use their multi-disciplinary, multi-platform approach to study the immunotherapeutic effects of different types of dietary fiber, as well as a range of other dietary supplements in different states of health and disease.