title: G protein-coupled receptors in human fat taste perception.
abstract: In contrast to carbohydrates and proteins, which are detected by specialized taste receptors in the forms of their respective building blocks, sugars, and L-amino acids, the third macronutrient, lipids, has until now not been associated with gustatory receptors. Instead, the recognition of fat stimuli was believed to rely mostly on textural, olfactory, and postingestive cues. During the recent years, however, research done mainly in rodent models revealed an additional gustatory component for the detection of long-chain fatty acids (LCFAs), the main taste-activating component of lipids. Concomitantly, a number of candidate fat taste receptors were proposed to be involved in rodent's gustatory fatty acid perception. Compared with rodent models, much less is known about human fat taste. In order to investigate the ability of the human gustatory system to respond to fat components, we performed sensory experiments with fatty acids of different chain lengths and derivatives thereof. We found that our panelists discriminated a "fatty" and an irritant "scratchy" taste component, with the "fatty" percept restricted to LCFAs. Using functional calcium-imaging experiments with the human orthologs of mouse candidate fat receptors belonging to the G protein-coupled receptor family, we correlated human sensory data with receptor properties characterized in vitro. We demonstrated that the pharmacological activation profile of human GPR40 and GPR120, 2 LCFA-specific receptors associated with gustatory fat perception in rodents, is inconsistent with the "scratchy" sensation of human subjects and more consistent with the percept described as "fatty." Expression analysis of GPR40 and GPR120 in human gustatory tissues revealed that, while the GPR40 gene is not expressed, GPR120 is detected in gustatory and nongustatory epithelia. On a cellular level, we found GPR120 mRNA and protein in taste buds as well as in the surrounding epithelial cells. We conclude that GPR120 may indeed participate in human gustatory fatty acid perception.
authors.affiliation: Department of Molecular Genetics, German Institute of Human Nutrition Potsdam-Rehbruecke, Nuthetal, Germany.
authors.forename: Maria Mercedes
authors.initials: MM
authors.lastname: Galindo
authors.forename: Nadine
authors.initials: N
authors.lastname: Voigt
authors.forename: Julia
authors.initials: J
authors.lastname: Stein
authors.forename: Jessica
authors.initials: J
authors.lastname: van Lengerich
authors.forename: Jan-Dirk
authors.initials: JD
authors.lastname: Raguse
authors.forename: Thomas
authors.initials: T
authors.lastname: Hofmann
authors.forename: Wolfgang
authors.initials: W
authors.lastname: Meyerhof
authors.forename: Maik
authors.initials: M
authors.lastname: Behrens
mesh_terms: D017398:Alternative Splicing; D000818:Animals; D002118:Calcium / Q000378:metabolism; D004305:Dose-Response Relationship, Drug; D005227:Fatty Acids / Q000494:pharmacology*; D015870:Gene Expression; D057809:HEK293 Cells; D006801:Humans; D007700:Kinetics; D051379:Mice; D020033:Protein Isoforms; D012333:RNA, Messenger / Q000235:genetics* / Q000378:metabolism*; D043562:Receptors, G-Protein-Coupled / Q000235:genetics / Q000378:metabolism*; D013649:Taste / Q000502:physiology*; D013650:Taste Buds / Q000187:drug effects / Q000502:physiology; D055697:Taste Perception / Q000187:drug effects / Q000502:physiology*; D014162:Transfection
chemical_list: C473034:FFAR1 protein, human; C519853:FFAR4 protein, human; D005227:Fatty Acids; D020033:Protein Isoforms; D012333:RNA, Messenger; D043562:Receptors, G-Protein-Coupled; D002118:Calcium