TAS1R2/ TAS1R3 Single-Nucleotide Polymorphisms Affect Sweet Taste Receptor Activation by Sweeteners: The SWEET Project

Abstract

Background/objectives: Studies have hypothesised that single-nucleotide polymorphisms (SNPs) in the TAS1R2 and TAS1R3 genes may alter sweet compound detection and eating habits, thereby increasing the risk of obesity. This in vitro study aims to measure the impact of human TAS1R2/TAS1R3 polymorphisms, some of which are thought to be involved in obesity, on the response of the sweet taste receptor to various sweeteners. It also aims to identify new SNPs in an obese population associated with a decrease in or loss of TAS1R2/TAS1R3 function.

Methods: First, the effects of 12 human TAS1R2-SNPs and 16 human TAS1R3-SNPs, previously identified in the literature, on the response of the sweet taste receptor stimulated by 12 sweeteners were investigated using functional cellular assays. Second, a total of 162 blood samples were collected from an obese population (BMI between 25 and 35 kg/m²) involved in the SWEET project. The TaqMan method for SNP genotyping was carried out using DNA extracted from blood samples to identify new SNPs and predict possible/probable TAS1R2/TAS1R3 loss of function.

Results: Although certain human TAS1R2/TAS1R3 SNPs showed reduced receptor response, they were not associated with particular phenotypes. Seven SNPs were predicted to severely impair the human TAS1R2/TAS1R3 response to sweeteners.

Conclusions: Although some TAS1R2- and TAS1R3-SNPs have previously been associated with obesity, our cellular results do not confirm this association and reinforce the hypothesis, put forward by other researchers, that sweet taste perception and sugar consumption are governed by factors other than the TAS1R2 and TAS1R3 genes.

Keywords: SNP; TAS1R2/TAS1R3; obesity; sugar intake; sweet taste receptor; sweetener.

Figure 1

Schematic summary of the different TAS1R2/TAS1R3 binding sites of the 12 studied sweeteners [9,11,12,13,14,15,16,19,56,57]. AceK: acesulfame-K; RebA: rebaudioside A; RebM: rebaudioside M; NHDC: neohesperidin dihydrochalcone; VFT: Venus flytrap domain; CRD: cysteine-rich domain; 7TM: 7-helix transmembrane domain.

Figure 2

mTAS1R2-WT/mTAS1R3-WT (black line) and mTAS1R2-WT/m-TAS1R3-I60T (turquoise line) dose–response curves with 12 sweeteners. The data are presented as the mean ± SEM of 8 wells from 4 independent experiments. * p < 0.05, ** p < 0.01, *** p < 0.001, calculated using ANOVA followed by Dunnett’s test (with reference to mTAS1R2-WT/mTAS1R3-WT). The p-values are presented in Table S1. WT: wild type; AceK: acesulfame-K; NHDC: neohesperidin dihydrochalcone.

Figure 3

Human TAS1R2-WT/TAS1R3-WT (blue line) and TAS1R2-SNP/TAS1R3-WT (red line) dose–response curves with sucralose. HEK293T-Gα16gust44 cells were transiently transfected with pcDNA6-MAX-TAS1R2-WT-FLAG or pcDNA6-MAX-TAS1R2-SNP-FLAG and pcDNA4-MAX-TAS1R3-WT-FLAG. The data are presented as the mean ± SEM of 8 wells from 4 independent experiments. * p < 0.05, ** p < 0.01, *** p < 0.001, calculated using ANOVA followed by Dunnett’s test for multiple comparison analysis (with reference to TAS1R2-WT/TAS1R3-WT). The p-values are presented in Table S2. WT: wild type.

Figure 4

Human TAS1R2-WT/TAS1R3-WT (blue line) and TAS1R2-WT/TAS1R3-SNP (green line) dose–response curves with sucralose. HEK293T-Gα16gust44 cells were transiently transfected with pcDNA6-MAX-TAS1R2-WT-FLAG and pcDNA4-MAX-TAS1R3-WT-FLAG or pcDNA4-MAX-TAS1R3-SNP-FLAG. The data are presented as the mean ± SEM of 8 wells from 4 independent experiments. * p < 0.05, ** p < 0.01, *** p < 0.001, calculated using ANOVA followed by Dunnett’s test for multiple comparison analysis (with reference to TAS1R2-WT/TAS1R3-WT). The p-values are presented in Table S3. WT: wild type.