Table 1. Expression of hormones and their receptors in taste buds are associated with taste perception and signaling and/or structural changes in taste buds.
| Hormone | Sources within the oral cavity | Hormone-receptor location in taste buds | Effects on taste perception | Effects on taste signaling and/or structural changes in taste buds | Reference |
|---|---|---|---|---|---|
| Insulin | Salivary gland and saliva; Type II TBCs | Type I, II, III TBCs; Progenitor cells | Increased response to salty tastants and avoidance to NaCl | Changes in mRNA level of NTPDase2; T1R3; Gustducin; CA4; GLUT8; SGLT1; Regulation of taste cell generation | [121,139,140,141] |
| Leptin | Saliva | Type II TBC | Dampens sweet taste (possibly increased temperature obscures leptin's effects); No effects on salty, sour, bitter, umami taste | Decreases sweet-stimulus evoked release of ATP from type II TBC; Increases 5-HT release from type III TBC (may not directly involve leptin binding) | [10,20,143,144,145] |
| Adiponectin | Saliva/salivary gland ductile cells | Adipor1 and Cdh13 in a subset of TBCs; AdipoR2 in TBC surrounding cells | Possibly implicated in the taste of lipids | Unknown | [121,131,146] |
| Neuropeptide Y | TBC (overlaps almost entirely with CCK expression); Saliva | NPY1-R on type 11 TBC that express T1Rs; NPY4-R expressed on taste nerve fibers | Involved in bitter and sweet taste; Acts antagonistically to CCK | Enhances an inwardly rectifying potassium current and modulates taste cell excitability; Acts antagonistically to inhibitory effect exerted by CCK on potassium current | [147,148,149,150] |
| Peptide YY | Type II TBC; Saliva | NPY1-R, on type II TBC; NPY4-R on type II TBC and afferent nerves | Modulates responsiveness to bitter-tasting stimuli, as well as to lipid emulsions | Might be involved in regulating CD36 expression and/or function | [20,149,151,152] |
| Cholecystokinin | TBC (overlaps almost entirely with NPY expression); Saliva | CCK-AR on type II TBC and afferent nerves | Involved in bitter, sweet, and umami taste perception | Implicated in regulation of inward and outward potassium current; Alter electrical activity of TBCs; Altered intracellular calcium levels; Prolonged bitter signaling | [75,121,150,153,154] |
| Glucagon | Type II TBC; Saliva/salivary gland | GluR co-expressed with glucagon on subpopulation of type II TBC | Modulates sweet taste responsiveness and maintains/ enhances sweet taste; No effect on sour, salty bitter taste | Enhanced sweet taste signaling; Appears to function as an autocrine signal for taste cells | [20,121,138,151] |
| GLP-1 and GLP-2 | Type II and III TBC | GLP-1R, on type III cells and on adjacent nerve fibers innervating the taste bud; GLP-1R in the major salivary glands of rats | GLP-1 deficiency contributes to decreased sweet and increased umami taste; GLP-1 decreases sour taste; No effect of GLP-1 on salty, bitter taste | GLP-1 acts as a paracrine modulator of taste; Role of GLP-2 in TBC remains unknown | [20,134,151,155,156,157] |
| Ghrelin | Type I, II, III, IV TBC; Saliva/salivary gland | GHRP in TBC I, II, III, IV | Modulates salty, sour, and sweet taste; Affects responsiveness to LCFAs | Physiological function in TBC remains unknown | [20,119,158,159] |
| VIP | Type II TBC; Saliva | VIPR-1 and VIPR-2 in subpopulation of T1R3 and T2R expressing TBC | Modulating taste perception of sweet, bit- ter, sour; VIP-deficiency associated with enhanced perception of sweet and bitter tastants; Opposing effects on sweet taste perception as GLP-1 signaling | Implicated in leptin receptor expression and GLP-1 expression in taste cells | [20,160] |
| Oxytocin | Saliva | Type I (low salt sensing) TBC | Decreases sweet taste; Possibly implicated in salty taste | Oxytocin acts via Ca2+ mobilization | [161,162,163] |
| Galanin | Type II and Type II TBC | GAL2-R in TBC (its co-expression with taste cell markers was not investigated) | Implicated in fat consumption but direct effects at the taste bud level are lacking. | Physiological function in taste buds remains unknown | [121,164] |
Table 1 summarizes current knowledge about hormone secretion and/or action as well as hormone receptor expression within taste cells and their contribution to taste sensation.
TBC, taste bud cell; NaCl, sodium chloride; mRNA, messenger ribonucleic acid; NTPDase2, nucleoside triphosphate diphosphohydrolase-2; T1R3, taste receptor type 1 member 3; CA4, carbonic anhydrase 4; GLUT8, glucose transporter 8; SGLT1, sodium/glucose transporter 1; ATP, adenosine triphosphate; 5-HT, serotonin; Adipor, adiponectin receptor; Cdh13, cadherin 13; CCK, cholecystokinin; NPY1-R, neuropeptide 1-receptor; NPY4-R, neuropeptide 4-receptor; CD36, cluster of differentiation 36 ; NPY, neuropeptide Y; CCK-AR, cholecystokinin-A receptor; GluR, glucagon receptor; GLP-1R, glucagon like peptide 1 receptor; GHRP, G protein-coupled growth hormone secretagogue receptor; LCFA, long chain fatty acid; VIPR, vasoactive intestinal peptide receptor; GAL2-R, galanin receptor 2.