Bile acids are cholesterol-based compounds that help absorb fatty nutrients and controlling glucose metabolism. They can be transformed by the gut microbiome into secondary compounds that interact with mammalian receptors. Even minor structural changes can completely change the function of a bile acid. However, we don’t know which microbes transform bile acids or how these transformations affect human health. Daniel Amador-Noguez of UW-Madison is screening isolates from the gut microbiome and testing their ability to transform bile acids to answer these questions.
The first surprising result that Daniel found was that more bacteria were capable of transforming bile acids than expected – nearly 50% of isolates screened. Some bacteria were capable of complex transformations with unique chemistry, and some bacteria were more efficient at these transformations than others. There is also high specificity, with many bacteria only able to perform one type of transformation.
To study bile acid transformations in vivo, Daniel colonized gnotobiotic mice with bile acid transforming bacteria (and some others). He did see transformation of one type of bile acid when a specific bacterium was added, but a second bile acid required multiple types of bacteria to be tranformed. While this system is still not fully understood, it does suggest that it may be possible to one day manipulate microbiomes to specifically transform bile acids.