Figure 1.

Ways gut microbiota metabolites act on targets. Within gut lumen, gut microbiota metabolites serve as the nutrients for some bacteria and change the composition of gut microbiota. Locally, gut microbiota metabolites can act on intestinal epithelium and immune cells in the lamina propria, and the local effects can further induce downstream systemic functions. Systemically, gut microbiota metabolites can be absorbed and transported to remote organs and tissues to exert diverse functions. Some gut microbiota metabolites can indirectly regulate the composition and function of gut microbiota via inducing hosts to synthesize and release anti-bacterial materials into gut lumen. Some gut microbiota metabolites may undergo enterohepatic circulation.