Advanced Search Abstract Mutational polymorphism in the TAS2R38 bitter taste receptor is a key determinant of threshold taste detection of isolated compounds, such as phenylthiocarbamide PTC and propylthiouracil PROPas well as complex orosensation-mediated traits such as diet choice and smoking habits. However, TAS2R38 harbors extensive additional polymorphism whose functional significance remains unknown.
Advanced Search Abstract The human population displays high variation in taste perception. Differences in individual taste sensitivity may also impact on nutrient intake and overall appetite.
A well-characterized example is the variable perception of bitter compounds such as 6-n-propylthiouracil PROP and phenylthiocarbamide PTCwhich can be accounted for at the molecular level by polymorphic variants in the specific type 2 taste receptor TAS2R Here, we proposed that the taste sensitivities of different bitter compounds would be correlated only when they activate the same bitter taste receptor.
Thirty-four volunteers were exposed to 8 bitter compounds that were selected based on their potential to activate overlapping and distinct repertoires of TAS2Rs. Taste intensity ratings were evaluated using the general Labeled Magnitude Scale.
Our data demonstrate a strong interaction between the intensity for bitter substances when they activate common TAS2Rs. In addition, our findings provide a novel framework to predict taste sensitivity based on their specific T2R activation profile.
Human appetite for highly palatable energy-rich foods may lead to overconsumption, one of the principal causes of obesity Yeomans et al. However, particularly since the discovery and characterization of the genes responsible for taste sensing Hoon et al. In recent years, genetic polymorphisms identified in taste receptors have been associated with differences in human sensitivity to sweet Fushan et al.
In addition, it has been suggested that individuals with higher taste acuity might be able to convey stronger and faster signals to the hypothalamus which in turn would result in an early onset of satiety and better control of food intake Stewart et al.
Moreover, as taste receptors are now recognized as expressed in cells and tissues throughout the body, the functional implications of these receptor variants may also extend beyond the oral cavity Behrens and Meyerhof ; Foster et al. Accordingly, it is important to gain an understanding of the molecular mechanisms of taste and taste sensitivity, as there is the potential to apply this knowledge to modulating hedonic value of foods in the context of trying to lower obesity incidence.
Bitter taste evolved as a sensing mechanism to detect and avoid consumption of a wide range of potential toxins present in food Sternini Consequently, high sensitivity in bitter perception may have direct survival implications Behrens and Meyerhof Thus, most of the variability in PTC sensitivity can be accounted for by 3 single nucleotide polymorphisms that form 2 common haplotypes, giving rise to receptor variants that contain the amino acids proline, alanine, and valine in positions, 49,andrespectively, or alanine, valine, and isoleucine, and which hence have been designated PAV and AVI.
Although the notion of hypertasting originally referred to the heightened PROP sensitivity, it has since been generalized to include the influence of this phenotype on other taste and somatosensory stimuli Bartoshuk et al.
Similarly, there is a substantial body of literature relating PROP sensitivity to other behaviors, including dietary preferences, risk of alcoholism, the control of food intake and risk of obesity and the prediction of taste thresholds for other compounds Anliker et al. Several early studies addressed the influence of PROP sensitivity on the taste sensitivity of other bitter agonists, albeit pre-dating the identification of the taste receptors as molecular mediators of taste Hall et al.
Nonetheless, the evidence that PROP status is the sole predicting factor determining sensitivity to other bitter and non-bitter tastes has been controversial Hayes et al. Notwithstanding the advances in the molecular pharmacology of taste receptors, the role of specific TAS2Rs as determinants of human taste sensitivity to different bitter compounds has been largely overlooked.
There are several notable cases where variations of TAS2R genes influence the taste sensitivity to different bitter compounds Kim et al. As the culmination of a series of studies conducted in the past decade, there is now a wealth of information about bitter agonists and their respective TAS2R activation profiles reviewed in Behrens and Meyerhof It is clear that TAS2Rs vary in their ability to respond to agonists, resulting in both specific and promiscuous receptors, while the same agonists can also activate multiple receptors Meyerhof et al.
Incorporating and synthesizing these findings, in this study we sought to investigate the relationship between taste sensitivity to PROP and other bitter compounds.
Accordingly, using suprathreshold bitterness perception testing for bitter compounds selected for their ability to activate different receptors, we examined the link between taste sensitivity and TAS2R activation profiles.
Materials and methods Participants Thirty-five volunteer staff and students of the University of Queensland 14 males and 21 females aged between 18 and 51 years old mean age Participants were of diverse ethnic origin: All participants gave informed, written consent prior to the commencement of the study, and were selected after successfully completing the eligibility questionnaires and the initial training session.
Volunteers with known illnesses, under medication, pregnant or lactating or reporting any kind of food allergies were not recruited for the current study.
A single female volunteer was also excluded from the analyses due to not completing the second trial.
Bitter taste compounds Eight compounds or natural extracts known to taste bitter to humans were selected based on their chemical diversity and differential activation of TAS2Rs Meyerhof et al. Where possible, the test concentrations for bitter taste compounds were selected based on previous literature from human psychophysical studies references are provided for each compound below.The objective of this study aimed to observe the phenylthiocarbamide (PTC) sensitivity and to determine gene frequency distribution among different human populations.
Allele frequencies for the bitter taste gene, TAS2R38 vary by racial/ethnic group and therefore when two racial groups are compared, they differ in phenotype as they differ in genotype .
Facsimile of the heading and first paragraph of Arthur Fox's first article on PTC sensitivity in the Proceedings of the National Academy of Sciences (Fox ).
Differences in individual taste sensitivity may also impact on nutrient intake and overall appetite. A well-characterized example is the variable perception of bitter compounds such as 6-n-propylthiouracil (PROP) and phenylthiocarbamide (PTC), which can be accounted for at the molecular level by polymorphic variants in the specific type 2 taste receptor (TAS2R38).
Phenylthiocarbamide: A Year Adventure in Genetics and Natural Selection Stephen Wooding1 THE DISCOVERY OF VARIABLE PTC SENSITIVITY Variation in PTC sensitivity was ﬁrst discovered in the sensitivity in human populations. In the 10 years fol-. Taste sensitivity to phenylthiocarbamide (PTC) and endemic goiter in the Indian natives of Peruvian highlands.
American Journal of Physical Anthropology. ; – the discovery of variable ptc sensitivity Variation in PTC sensitivity was first discovered in the early s. In a laboratory incident that would curl the toes of the most stoic OSHA officer, Arthur L.
Fox was pouring some PTC (a white powder) into a bottle when some “flew around in the air” (Figure 1) (F ox ).