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The molecular basis of individual differences in phenylthiocarbamide and propylthiouracil bitterness perception.

ABSTRACT: Individual differences in perception are ubiquitous within the chemical senses: taste, smell, and chemical somesthesis . A hypothesis of this fact states that polymorphisms in human sensory receptor genes could alter perception by coding for functionally distinct receptor types . We have previously reported evidence that sequence variants in a presumptive bitter receptor gene (hTAS2R38) correlate with differences in bitterness recognition of phenylthiocarbamide (PTC) . Here, we map individual psychogenomic pathways for bitter taste by testing people with a variety of psychophysical tasks and linking their individual perceptions of the compounds PTC and propylthiouracil (PROP) to the in vitro responses of their TAS2R38 receptor variants. Functional expression studies demonstrate that five different haplotypes from the hTAS2R38 gene code for operatively distinct receptors. The responses of the three haplotypes we also tested in vivo correlate strongly with individuals' psychophysical bitter sensitivities to a family of compounds. These data provide a direct molecular link between heritable variability in bitter taste perception to functional variations of a single G protein coupled receptor that responds to compounds such as PTC and PROP that contain the N-C=S moiety. The molecular mechanisms of perceived bitterness variability have therapeutic implications, such as helping patients to consume beneficial bitter-tasting compounds-for example, pharmaceuticals and selected phytochemicals.

SUBMITTER: Bufe B

PROVIDER: S-EPMC1400547 | biostudies-literature | 2005 Feb

REPOSITORIES: biostudies-literature

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The molecular basis of individual differences in phenylthiocarbamide and propylthiouracil bitterness perception.

Bufe Bernd B Breslin Paul A S PA Kuhn Christina C Reed Danielle R DR Tharp Christopher D CD Slack Jay P JP Kim Un-Kyung UK Drayna Dennis D Meyerhof Wolfgang W

Current biology : CB 20050201 4

Individual differences in perception are ubiquitous within the chemical senses: taste, smell, and chemical somesthesis . A hypothesis of this fact states that polymorphisms in human sensory receptor genes could alter perception by coding for functionally distinct receptor types . We have previously reported evidence that sequence variants in a presumptive bitter receptor gene (hTAS2R38) correlate with differences in bitterness recognition of phenylthiocarbamide (PTC) . Here, we map individual ps ...[more]

PMID: 15723792

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Project description:Previous reports that the sensitivity to the bitter tasting substance 6-n-propylthiouracil (PROP) is related to the sensitivity to other tastes, to chemical irritants, and to fats and oils have led to adoption of PROP as a measure of general oral sensitivity and as a predictor of dietary habits that could impact health. The results, however, have not been consistent. It was recently discovered that the ability to perceive "thermal taste" (i.e., sweetness from thermal stimulation alone) was associated with higher responsiveness to 4 prototypical taste stimuli but not to PROP. This finding implied that individual differences in taste perception are determined in large part by factors other than those related to genetic expression of the PROP receptor. The present study followed up this observation by comparing individual differences in perception of 4 prototypical taste stimuli (sucrose, NaCl, citric acid, and quinine) and PROP under conditions that also enabled assessment of the reliability of individual intensity ratings of taste. Creaminess ratings of 3 milk products that had different fat contents were also collected to investigate further the relationship between taste and oral somatosensory perception. The results showed that intensity ratings across 2 trials were significantly correlated for all 5 taste stimuli and that averaging across replicates led to significant correlations among the 4 prototypical stimuli. In contrast, the bitterness of PROP was correlated only with the bitterness of quinine. None of the taste stimuli, including PROP, was significantly correlated with ratings of creaminess. These results imply 1) that with the exception of PROP, as few as 2 intensity ratings of common taste stimuli can reveal individual differences in overall taste perception and 2) that any relationship between taste and oral sensation is too weak to be detected under the same conditions. Accordingly, the results support other evidence that the genetic factors which determine the ability to perceive PROP do not play a major role in overall taste and oral somatosensory perception.

Project description:Extensive research documents the existence of egocentric biases in the perception and application of justice norms. The origin of these biases remains poorly understood. We investigated both inter- and intra-individual differences in egocentric justice biases. Participants played an ultimatum game presumably with different anonymous players (simulated by a computer) in which they contributed differentially to the joint production of the initial endowment. We examined how contributions (low vs. high) affect proposers' offers and responders' acceptance decisions, as well as their fairness judgments and their emotional reactions to different types of offers (equal, equitable, unfair, and hyperfair). An egocentric bias in proposers' offers (indicating more flexible preferences) was found only in individualists and not in prosocials, suggesting differences in the motivations (or cognitions) underlying their choice of justice norms. Responders also showed egocentric biases in their judgments of fairness and in their emotional reactions to equal and equitable offers, but not in their acceptance decisions. Such dissociation might suggest that some form of emotion regulation occurred. Responders may evaluate offers on valence dimensions (e.g., goal conduciveness/outcome favorability and norm compatibility/justice) that are multiply interacting and potentially conflicting. The individual's acceptance/rejection decision reflects the relative weight attributed to competing appraisals. For this overt behavioral decision, the (personal) appraisal of outcome favorability that drives (analytical) acceptance of goal-conducive outcome seems to be stronger than the (social) appraisal of outcome fairness, which may trigger covert (emotional) rejection of offers that are incompatible with justice norms. Our data show that the emotional reaction patterns provide a more fine-grained readout of the overall evaluation of the proposer's action, the underlying emotional dynamics of which may, in real life, strongly determine future interactions with specific partners. Further research on the relationship between emotion and behavior in economic games is needed to explore potential dissociations and long-term effects.

Dataset Information

The molecular basis of individual differences in phenylthiocarbamide and propylthiouracil bitterness perception.

Publications

The molecular basis of individual differences in phenylthiocarbamide and propylthiouracil bitterness perception.

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