Psychophysical Dissection of Genotype Effects on Human Bitter Perception

Abstract

The purpose of this study was to define the effects of individual polymorphisms within the haplotypes of the TAS2R38 taste receptor gene on human bitter taste perception. A racially and ethnically diverse sample of children and adults (N = 980) was phenotyped for thresholds of 6-n-propylthiouracil (PROP) and genotyped for 3 polymorphisms of the TAS2R38 gene (A49P, V262A, I296V). Subjects were grouped according to their diplotype (i.e., specific combinations of haplotypes) and compared for PROP thresholds. By contrasting subjects with particular diplotypes, we found that in addition to A49P, V262A and I296V were related to the ability of the subjects to detect PROP. The V262A variant site affected the ability of subjects to detect mid-range concentrations of PROP, whereas the I296V variant site affected the ability of subjects to perceive PROP at the lowest concentration. These data agree with results from previous studies using cell-based assays for 2 variant sites (A49P and V262A) but not those for the I296V variant site. The reason for the discordant results is not known but it highlights the need for psychophysical as well as cell-based methods to understand the genotype-phenotype relationship for taste receptors. Human PROP sensitivity is determined by the combination of each of these 3 polymorphisms within the TAS2R38 gene.

Age Variation In Bitter Taste Perception In Relation To The Tas2r38 Taste Receptor Phenotype.

“…The taster PAV diplotype was less affected by age: the proportions of tasters and supertasters were similar in adults and children with the PAV haplotype. This is in accordance with Mennella et al [27] who reported that AVI/PAV children, but not adults, perceived a bitter taste at low PROP concentrations, whereas no such effect occurred in AVI or PAV homozygous.…”

Intragastric infusion of denatonium benzoate attenuates interdigestive gastric motility and hunger scores in healthy female volunteers

“…Our finding that women perceive a bitter lingual 287 stimulus more intensely than men is in agreement with previous bitter sensitivity studies (6,288 8). This sex difference has been associated with the density of fungiform papillae on the 289 anterior tongue and with polymorphisms in the haplotypes of the TAS2R38 gene for PROP 290 sensitivity (6,7,33,34). 291 In addition we found that in women, but not in men, there was a switch in the origin of phase (22).…”

“…In the US, DB is added at a concentration of 6 ppm to denature alcohol 33 (3). Specialized G-protein coupled receptors (GPCRs) from the taste 2 receptor (TAS2R) family 34 are involved in the perception of bitter compounds (4). Until now, 25 TAS2Rs have been 35 identified in humans (5).…”

Flavor Perception and Preference Development in Human Infants

“…In addition to these individual differences, psychophysical studies have shown that PROP sensitivity appears to decrease with age. Children heterozygous for a TAS2R38 variant perceived lower concentrations of this bitter chemical than did heterozygous adolescents, who in turn detected lower concentrations than heterozygous adults [30,31] . Such sensitivity to this class of bitter tastes may contribute to reduced acceptance of cruciferous vegetables during childhood.…”