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Yuzo Ninomiya - One of the best experts on this subject based on the ideXlab platform.
The Biochemical journal, 2016Co-Authors: Ryusuke Yoshida, Yuzo NinomiyaAbstract:
The Taste system of animals is used to detect valuable nutrients and harmful compounds in foods. In humans and mice, sweet, bitter, salty, sour and umami Tastes are considered the five basic Taste qualities. Sweet and umami Tastes are mediated by G-protein-coupled receptors, belonging to the T1R (Taste receptor type 1) family. This family consists of three members (T1R1, T1R2 and T1R3). They function as sweet or umami Taste receptors by forming heterodimeric complexes, T1R1+T1R3 (umami) or T1R2+T1R3 (sweet). Receptors for each of the basic Tastes are thought to be expressed exclusively in Taste bud cells. Sweet (T1R2+T1R3-expressing) Taste cells were thought to be segregated from umami (T1R1+T1R3-expressing) Taste cells in Taste buds. However, recent studies have revealed that a significant portion of Taste cells in mice expressed all T1R subunits and responded to both sweet and umami compounds. This suggests that sweet and umami Taste cells may not be segregated. Mice are able to discriminate between sweet and umami Tastes, and both Tastes contribute to behavioural preferences for sweet or umami compounds. There is growing evidence that T1R3 is also involved in behavioural avoidance of calcium Tastes in mice, which implies that there may be a further population of T1R-expressing Taste cells that mediate aversion to calcium Taste. Therefore the simple view of detection and segregation of sweet and umami Tastes by T1R-expressing Taste cells, in mice, is now open to re-examination.
Current pharmaceutical design, 2014Co-Authors: Shusuke Iwata, Ryusuke Yoshida, Yuzo NinomiyaAbstract:
In the oral cavity, Taste receptor cells dedicate to detecting chemical compounds in foodstuffs and transmitting their signals to gustatory nerve fibers. Heretofore, five Taste qualities (sweet, umami, bitter, salty and sour) are generally accepted as basic Tastes. Each of these may have a specific role in the detection of nutritious and poisonous substances; sweet for carbohydrate sources of calories, umami for protein and amino acid contents, bitter for harmful compounds, salty for minerals and sour for ripeness of fruits and spoiled foods. Recent studies have revealed molecular mechanisms for reception and transduction of these five basic Tastes. Sweet, umami and bitter Tastes are mediated by G-protein coupled receptors (GPCRs) and second-messenger signaling cascades. Salty and sour Tastes are mediated by channel-type receptors. In addition to five basic Tastes, Taste receptor cells may have the ability to detect fat Taste, which is elicited by fatty acids, and calcium Taste, which is elicited by calcium. Taste compounds eliciting either fat Taste or calcium Taste may be detected by specific GPCRs expressed in Taste receptor cells. This review will focus on transduction mechanisms and cellular characteristics responsible for each of basic Tastes, fat Taste and calcium Taste.
Chemical senses, 2002Co-Authors: Bernd Lindemann, Yoko Ogiwara, Yuzo NinomiyaAbstract:
Sweet, bitter, salty and sour are the four Taste qualities upon which the human sense of Taste is based. But is this really all? Is there room for more basic Tastes on the human tongue? Well, there is. Strangely, though, while people Tasted it daily, the fifth Taste long remained unknown and unnamed. Its final discovery, made nearly a century ago, was due entirely to a single man, a chemistry professor at the Imperial University of Tokyo, Kikunae Ikeda. It was Ikeda’s insight and endurance alone which powered this early work. The tedious chemical isolation and identification of the new Taste substance was done without the help from postdoctorates or students, as would be usual today, aided only by one technician. The investigation was based on an observation concerning the dominant Taste of dashi, a Japanese soup base. The Taste of dashi is mild but, according to Ikeda, clearly distinct from that of the four basic Tastes. Ikeda proceeded to isolate the principal Taste substance from a main ingredient of dashi, the seaweed Laminaria japonica. This was done with the procedures of classical chemistry, aqueous extraction, removal of large-scale contaminants (mannitol, NaCl, KCl) by crystallization, lead precipitation and numerous other steps of preparative chemistry. Finally, low-pressure evaporation resulted in the slow crystallization of a single substance with the mass formula C5H9NO4: glutamic acid. Its Taste was named umami, a word derived from the Japanese adjective umai (delicious). It has taken root as a scientific term internationally. The scientific community received this discovery with moderate applause only. Many, especially in Englishspeaking countries, remained unconvinced. One hindrance for the accceptance may have been that the detailed publication of Ikeda’s work appeared in Japanese (Ikeda, 1909). Other hindrances were that umami Taste is mild even at high concentrations of the tastants. Furthermore, high concentrations of glutamate, an anion, are necessarily accompanied by cations, the salty or sour Taste of which confused the issue. Umami research proceeded on a larger scale especially since about 1980. The umami substances L-glutamate, inosine 5′-monophosphate (IMP) and guanosine 5′-monophosphate (of which the latter two enhance the glutamate Taste) were defined, and Taste responses to them were investigated in humans and animals. Animal models, however, were of limited use as the responses of different species, even of different strains of mice, were at variance. Today a search in PubMed (MedLine) for papers concerned with Taste and containing the term ‘umami’ retrieved 86 references. (For comparison, ‘sweet Taste’ retrieved 10 times more references published since 1980.) A search with the Google engine found >4000 web pages containing the phrase ‘umami’. Some of these pages were from restaurants advertising umami food. Others dealt with the misconception that glutamate contained in food might be harmful. But foremost among them were pages reprinting newspaper articles about the discovery of umami receptors. The discovery of umami receptors, Taste receptors for L-glutamate, using methods of molecular biology is one of the recent highlights of Taste research. In 2000, a modified glutamate receptor of the brain was found, the TastemGluR4. It is a G protein-coupled (metabotropic) receptor. The Taste variety of mGluR4 has a truncated N-terminal to which L-glutamate still binds, albeit with reduced affinity. Presumably, therefore, the truncation adapted the receptor to the high glutamate concentration in food (Chaudhari et al., 2000). More recently, another umami receptor was discovered. Interestingly, this one is a heteromere built of the G protein-coupled receptors T1R1 and T1R3. In mice this heteromere responds to many amino acids contained in food, but in humans its response is preferentially to L-glutamate and is enhanced by IMP (Nelson et al., 2002).
Cathy A. Pelletier - One of the best experts on this subject based on the ideXlab platform.
Dysphagia, 2013Co-Authors: Angela M. Dietsch, Nancy Pearl Solomon, Catriona M Steele, Cathy A. PelletierAbstract:
Barium may affect the perception of Taste intensity and palatability. Such differences are important considerations in the selection of dysphagia assessment strategies and interpretation of results. Eighty healthy women grouped by age (younger, older) and genetic Taste status (superTaster, nonTaster) rated intensity and palatability for seven tastants prepared in deionized water with and without 40 % w/v barium: noncarbonated and carbonated water, diluted ethanol, and high concentrations of citric acid (sour), sodium chloride (salty), caffeine (bitter), and sucrose (sweet). Mixed-model analyses explored the effects of barium, Taster status, and age on perceived Taste intensity and acceptability of stimuli. Barium was associated with lower Taste intensity ratings for sweet, salty, and bitter tastants, higher Taste intensity in carbonated water, and lower palatability in water, sweet, sour, and carbonated water. Older subjects reported lower palatability (all barium samples, sour) and higher Taste intensity scores (ethanol, sweet, sour) compared to younger subjects. SuperTasters reported higher Taste intensity (ethanol, sweet, sour, salty, bitter) and lower palatability (ethanol, salty, bitter) than nonTasters. Refusal rates were highest for younger subjects and superTasters, and for barium (regardless of tastant), bitter, and ethanol. Barium suppressed the perceived intensity of some Tastes and reduced palatability. These effects are more pronounced in older subjects and superTasters, but younger superTasters are least likely to tolerate trials of barium and strong tastant solutions.
Charles S Zuker - One of the best experts on this subject based on the ideXlab platform.
Nature, 2015Co-Authors: Robert P J Barretto, Sarah Gillissmith, Jayaram Chandrashekar, David A Yarmolinsky, Mark J Schnitzer, Nicholas J P Ryba, Charles S ZukerAbstract:
Using two-photon microendoscopy and genetically encoded calcium indicators the tuning properties of the first neural station of the gustatory system are explored; results reveal that ganglion neurons are matched to specific Taste receptor cells, supporting a labelled line model of information transfer in the Taste system. Individual Tastes (sweet, sour, bitter, salty and umami) are detected by dedicated Taste receptor cells on the tongue and palate, but how these signals are encoded and transmitted to the relevant part of the central nervous system — the gustatory cortex — is unknown. Using transgenic mice expressing a calcium indicator in neurons, Charles Zuker and colleagues characterize the tuning properties of ganglion neurons, the first neural station of the gustatory system. Ganglion neurons respond specifically to certain Tastes, supporting a 'labelled line' model of information transfer in the Taste system. The mammalian Taste system is responsible for sensing and responding to the five basic Taste qualities: sweet, sour, bitter, salty and umami. Previously, we showed that each Taste is detected by dedicated Taste receptor cells (TRCs) on the tongue and palate epithelium1. To understand how TRCs transmit information to higher neural centres, we examined the tuning properties of large ensembles of neurons in the first neural station of the gustatory system. Here, we generated and characterized a collection of transgenic mice expressing a genetically encoded calcium indicator2 in central and peripheral neurons, and used a gradient refractive index microendoscope3 combined with high-resolution two-photon microscopy to image Taste responses from ganglion neurons buried deep at the base of the brain. Our results reveal fine selectivity in the Taste preference of ganglion neurons; demonstrate a strong match between TRCs in the tongue and the principal neural afferents relaying Taste information to the brain; and expose the highly specific transfer of Taste information between Taste cells and the central nervous system.
Eileen R Gibney - One of the best experts on this subject based on the ideXlab platform.
Proceedings of the Nutrition Society, 2011Co-Authors: Emma L Feeney, Stephen J Obrien, Amalia G M Scannell, Anne Markey, Eileen R GibneyAbstract:
Taste is often cited as the factor of greatest significance in food choice, and has been described as the body’s ‘nutritional gatekeeper’. Variation in Taste receptor genes can give rise to differential perception of sweet, umami and bitter Tastes, whereas less is known about the genetics of sour and salty Taste. Over twenty-five bitter Taste receptor genes exist, of which TAS2R38 is one of the most studied. This gene is broadly tuned to the perception of the bitter-tasting thiourea compounds, which are found in brassica vegetables and other foods with purported health benefits, such as green tea and soya. Variations in this gene contribute to three thiourea Taster groups of people: superTasters, medium Tasters and nonTasters. Differences in Taster status have been linked to body weight, alcoholism, preferences for sugar and fat levels in food and fruit and vegetable preferences. However, genetic predispositions to food preferences may be outweighed by environmental influences, and few studies have examined both. The Tastebuddies study aimed at taking a holistic approach, examining both genetic and environmental factors in children and adults. Taster status, age and gender were the most significant influences in food preferences, whereas genotype was less important. Taster perception was associated with BMI in women; nonTasters had a higher mean BMI than medium Tasters or superTasters. Nutrient intakes were influenced by both phenotype and genotype for the whole group, and in women, the AVI variation of the TAS2R38 gene was associated with a nutrient intake pattern indicative of healthy eating. Food choice: Bitter Taste: Phenylthiocarbamide: Propylthiouracil: TAS2R38: Fruit and vegetables
Davide Risso - One of the best experts on this subject based on the ideXlab platform.
PLOS ONE, 2016Co-Authors: Davide Risso, Julia Kozlitina, Eduardo Sainz, Joanne Gutierrez, Stephen Wooding, Betelihem Getachew, Donata Luiselli, Carla J Berg, Dennis DraynaAbstract:
Common TAS2R38 Taste receptor gene variants specify the ability to Taste phenylthiocarbamide (PTC), 6-n-propylthiouracil (PROP) and structurally related compounds. Tobacco smoke contains a complex mixture of chemical substances of varying structure and functionality, some of which activate different Taste receptors. Accordingly, it has been suggested that non-Taster individuals may be more likely to smoke because of their inability to Taste bitter compounds present in tobacco smoke, but results to date have been conflicting. We studied three cohorts: 237 European-Americans from the state of Georgia, 1,353 European-Americans and 2,363 African-Americans from the Dallas Heart Study (DHS), and 4,973 African-Americans from the Dallas Biobank. Tobacco use data was collected and TAS2R38 polymorphisms were genotyped for all participants, and PTC Taste sensitivity was assessed in the Georgia population. In the Georgia group, PTC Tasters were less common among those who smoke: 71.5% of smokers were PTC Tasters while 82.5% of non-smokers were PTC Tasters (P = 0.03). The frequency of the TAS2R38 PAV Taster haplotype showed a trend toward being lower in smokers (38.4%) than in non-smokers (43.1%), although this was not statistically significant (P = 0.31). In the DHS European-Americans, the Taster haplotype was less common in smokers (37.0% vs. 44.0% in non-smokers, P = 0.003), and conversely the frequency of the non-Taster haplotype was more common in smokers (58.7% vs. 51.5% in non-smokers, P = 0.002). No difference in the frequency of these haplotypes was observed in African Americans in either the Dallas Heart Study or the Dallas Biobank. We conclude that TAS2R38 haplotypes are associated with smoking status in European-Americans but not in African-American populations. PTC Taster status may play a role in protecting individuals from cigarette smoking in specific populations.