Peripheral chemosensing system for tastants and nutrients

Purpose of review The purpose of this review is to discuss the presence and possible roles of peripheral taste/nutrient sensors, particularly taste receptors. Recent findings Recent studies have demonstrated that taste signaling molecules are distributed not only in the gustatory epithelium, but also in other tissues, including the gastrointestinal tract, airways, testes and brain. Taste signaling mechanisms in the gastrointestinal tract were reported to participate in detecting sweet, umami and bitter compounds. Several research groups have suggested that tastant/nutrient detection by other systems contributes to the behavioral responses to food intake. Summary Taste-like cells expressing taste signaling components are distributed in multiple tissues. Investigation of their potential roles in chemosensing has just begun. Researchers have identified at least two chemosensory pathways in the gastrointestinal tract for detecting tastants/nutrients. One is the taste receptor signaling pathway and the other is the currently unknown nutrient-sensing pathway that elicits postingestive effects. The former system utilizes a mechanism similar to taste sensing in the oral cavity. By understanding how tastants/nutrients are sensed and regulated through both systems, we may be able to more effectively control food intake in the future.