Clinical Role of Extraoral Bitter Taste Receptors

Abstract

Humans can recognise five basic tastes: sweet, sour, salty, bitter and umami. Sour and salty substances are linked to ion channels, while sweet, bitter and umami flavours are transmitted through receptors linked to the G protein (G protein-coupled receptors; GPCRs). There are two main types of GPCRs that transmit information about sweet, umami and bitter tastes—the Tas1r and TAS2R families. There are about 25 functional TAS2R genes coding bitter taste receptor proteins. They are found not only in the mouth and throat, but also in the intestines, brain, bladder and lower and upper respiratory tract. The determination of their purpose in these locations has become an inspiration for much research. Their presence has also been confirmed in breast cancer cells, ovarian cancer cells and neuroblastoma, revealing a promising new oncological marker. Polymorphisms of TAS2R38 have been proven to have an influence on the course of chronic rhinosinusitis and upper airway defensive mechanisms. TAS2R receptors mediate the bronchodilatory effect in human airway smooth muscle, which may lead to the creation of another medicine group used in asthma or chronic obstructive pulmonary disease. The discovery that functionally compromised TAS2R receptors negatively impact glucose homeostasis has produced a new area of diabetes research. In this article, we would like to focus on what facts have been already established in the matter of extraoral TAS2R receptors in humans.

Therapeutic effects of quinine in a mouse model of atopic dermatitis

“…It has been proposed that bitter taste receptors (TAS2Rs) ( 9 ) only exist on the tongue, and that their activation enables the perception of bitterness ( 10 ). However, a previous study has found that TAS2Rs are also present in the respiratory system ( 11 ).…”

Positive selection drives the evolution of a primate bitter taste receptor gene

“…Bitter taste, one of the five basic taste qualities (umami, sweet, bitter, sour, and salty), acts as sentinels in defending animals from consuming the potentially toxic and harmful substances which often taste bitter (Chandrashekar et al., 2000; Lu et al., 2017). Bitter taste perception is mediated by the interaction between bitter tastants and bitter taste receptors which are discovered in mouth and throat, and also in extraoral positions such as brain, respiratory tract, lungs, heart, intestines, and bladder (Bloxham et al., 2020; Foster et al., 2013; Garcia‐Esparcia et al., 2013; Jeruzal‐Swiatecka et al., 2020; Shah et al., 2009).…”

Expression of Jejunal Taste Receptors in Women with Morbid Obesity

“…Nutrient taste receptors (TASs) have been well characterized in the oral cavity, but recently they have also been found in the gut mucosa [ 18 ]. Within the gastrointestinal (GI) tract, two families of TASs, the taste 1 receptor family (TAS1R), which detects umami and sweet stimuli, and the taste 2 receptor family (TAS2R), which detects bitter stimuli, occur as shown in Figure 1 [ 19 , 20 ]. The activation of these GI receptors results in the release of intestinal hormones such as cholecystokinin (CKK) or glucose-dependent insulinotropic polypeptide and glucagon-like peptide-1 (GLP-1), which modulate the physiological response to nutrients, particularly satiety and the maintenance of energy homeostasis [ 21 ].…”