The Gillum Group characterizes identified metabolites generated via the gut microbiota, gut, and liver that affect host metabolism and appetite. We identify the receptors and cellular targets through which they exert their beneficial or detrimental effects. Identifying such metabolite receptor pairs may provide novel therapeutic possibilities by either targeting metabolite synthesis or developing receptor agonists/antagonists. We anticipate to find several unidentified microbial metabolites that could affect host metabolism, as well as hepatic factors that regulate appetite.