Physiological roles of dietary free glutamate in gastrointestinal functions

The appropriate recognition of nutrients in gastrointestinal tract has an important role in the maintenance of healthy body functions. Perception of nutrients in gastrointestinal tract influences not only the regulation of gastrointestinal functions such as digestion and absorption, but also the subsequent formation of ingestive behaviors and food preferences. Glutamate is widely distributed amino acids, approximately 15-45% in the dietary protein as the total of free- and bound-forms. To note is that, glutamate is implicated in numerous physiological and metabolic functions in the body as a nutrient, in addition, free glutamate in the food is also known as the source of umami, one of the five basic taste. Taste is basically percepted on the tongue in the oral cavity via the specific taste sensors (receptors and/or transporters), however, the recent studies suggest the functional roles of taste sensors in the regulation of gastrointestinal tract. Interestingly, we recently found the presence of specific glutamate-sensing systems in the lumen of the stomach. In addition, we have been vigorously studying the physiological roles of dietary free glutamate in the body through experimental animals and human. In this topic, we review the beneficial roles of dietary free glutamate in the regulation of gastrointestinal functions and propose some application of the benefits for the clinical gastrointestinal disorders.