TAS2R38 Single Nucleotide Polymorphisms Are Associated with PROP—but Not Thermal—Tasting: a Pilot Study

Abstract

T2R38 is a bitter taste receptor known to be associated with 6-n-propylthiouracil (PROP) responsiveness, as operationalized by PROP taster status (PTS). Suprathreshold PROP responsiveness is a proxy for general taste responsiveness and has been linked to diet-related behavior and health outcomes, including alcohol consumption, body mass index, and cardiovascular disease risk. The ability to taste PROP allows classification of individuals into three groups: super-tasters (pST), medium-tasters (pMT), or non-tasters (pNT). Recently, another taste phenotype, thermal tasting, has been identified, in which the heating or cooling of a region of one’s tongue evokes a phantom taste response in 20–50 % of individuals. The mechanism behind thermal tasting is not yet known. In this study, we sought to investigate the relationship between TAS2R38 sequence variation with both PROP responsiveness and thermal taster status (TTS). PTS was determined from participants’ intensity rating of a 3.2 mM PROP solution, while TTS was determined based on the presence/absence and intensity (generalized labeled magnitude scale) of oral sensation(s) elicited by temperature changes to a participant’s extended tongue applied by a computer-controlled thermode. Using buccal cell DNA, we performed genotyping of the TAS2R38 variations for 53 individuals, primarily of Caucasian decent. A significant correlation between PTS and three TAS2R38 single nucleotide polymorphisms (SNPs) (rs713598, rs1726866, and rs10246939) was found, as previously reported, with the strongest association seen when all three SNPs were included in the multiple regression model. However, not all PTS differences can be explained by variation at these three SNP sites or other sites in the coding region, suggesting the involvement of additional genes. Although in prior studies both PTS and TTS have been shown to predict general taste responsiveness, our data indicate no association between TTS and the TAS2R38 genotype, suggesting the involvement of different genes in this phenotype. While underpowered due to small sample size, our study was not able to confirm the previously reported association between Gustin SNP rs2274333 genotype and PROP responsiveness. This pilot study provides the first genetic evidence to support previous phenotype-based observation suggesting a lack of association between PROP responsiveness and thermal taster status. Specifically, our data show that TAS2R38 is unlikely to be involved in thermal tasting.