Microbiota-produced molecules like short-chain fatty acids, indole derivatives, and phenols can enter the bloodstream, be metabolized by the host, and bind to receptors to trigger signaling cascades.

“And so the array of molecules is still being defined, we're trying to figure out what all these chemicals are. We've mentioned the short-chain fatty acids, but those are just the tip of the iceberg. They are really interesting compounds like indole derivatives and phenols, derived from amino acids, metabolized by gut microbes, taken up into the bloodstream. And then we further metabolize these, they become kind of co-microbe host metabolites, and then they can go on and bind to different receptors throughout our body, anywhere our bloodstream has access to, and start to trigger signaling cascades.”