Immune system vs. gut bacteria: How vitamin A 'keeps the peace'

A team of scientists, led by Shipra Vaishnava, an assistant professor of molecular microbiology and immunology at Brown University in Providence, RI, found that moderate levels of vitamin A in the intestine prevent the immune system from becoming overactive.The findings, published in the journal Immunity, may have significant implications for autoimmune disorders, such as Crohn's disease.The gut microbiota consists of over 100 trillion bacteria, explain the researchers, which are mainly divided into the phyla Firmicutes and Bacteroidetes.Using a mouse model of the microbiome, Vaishnava and team found that these gut bacteria regulate their hosts' immune responses by adjusting a protein that activates vitamin A in the gastrointestinal tract.The protein is called retinol dehydrogenase 7 (Rdh7) because it transforms vitamin A to retinoic acid, which is vitamin A's active form.Furthermore, the scientists found that Firmicutes bacteria — more specifically, bacteria that are part of the Clostridia family — lower the expression of Rdh7. They say that understanding the interactions between the gut bacteria and the immune response can shed light on new therapies for autoimmune disorders, such as inflammatory bowel disease."A lot of these diseases are attributed to increased immune response or immune activation, but we've found a new way that bacteria in our gut can dampen the immune response," Vaishnava says. We hope that adding our finding — that bacteria can regulate how vitamin A is being metabolized in the intestine or stored — could help clarify why the field is seeing what it is seeing."The researcher goes on to highlight the role of diet and gut bacteria for keeping our immune system healthy. "Both our diet and the bacteria in our gut are critically linked in regulating how our immune cells behave," Vaishnava says."Finding what those links are at a molecular level is important to figuring out how we could use either diet or bacteria, or both of them together, to have a therapeutic effect in inflammatory or infectious diseases."Your privacy is important to us.Healthline Media UK Ltd, Brighton, UK.© 2004-2019 All rights reserved.