Advances in the study of the role of extraoral bitter taste receptors

Taste is one of the basic senses of living organisms and can recognize sour, bitter, salty, sweet and umami tastes. Bitter taste receptor is a class of G protein-coupled receptors capable of sensing bitterness. Initially, bitter taste receptor was thought to be only found in the taste buds of the tongue, palate and throat. Recent research has shown that in addition to the oral cavity, the bitter taste receptor is also present in the intestinal tract, respiratory tract, urinary tract, vascular smooth muscle, nervous system, thyroid gland and other tissues and organs to regulate body homeostasis and resist disorders . In this review, we focus on the effects of the bitter taste receptor outside the oral cavity to lay the groundwork for future research.