Bitter taste receptor TAS2R4 is involved in regulation of mechanisms of gastric acid secretion induced by gallic acid
Poster presentation
Red wine is an admired beverage, considered to be the healthiest among wines as it provides antioxidants from the dark skin of the grapes. Among these are the characteristic phenolic compounds in red wine, which contribute predominantly to the distinctive taste of red wine. Gallic acid (GA) is one of the major phenolic compounds with evidence for its contribution to the astringent sensation whereas this is not clear for the bitter taste. In our previous studies, we showed that bitter compounds act as regulators on the cellular proton secretion (PS) via extra-oral bitter-taste receptors (TAS2Rs). Furthermore, we showed that red wine is stimulating the PS more effective than white wine. This study was performed with the hypothesis that GA plays a contributive role to the red wine-stimulated effect on PS in human gastric tumor (HGT-1) cells.
Sensory tastings pointed out that GA [10 µM] tastes significantly more bitter than tap water, whereby the bitterness is increasing with the concentration of GA. In cell culture studies with HGT-1 cells, the lowest GA concentration perceived bitter was 10 µM, which also evoked a bitter receptor-associated response on the PS by HGT-1 cells. For the investigation of the GA-evoked proton secretion in a red wine matrix, HGT-1 cells were exposed to red wine samples spiked with up to 10 µM GA. These results demonstrated distinct effects of two red wines (Zweigelt and Blaufränkisch) on PS by HGT-1 cells to be modulated after spiking with GA up to a concentration of 10 µM GA. Subsequent gene expression analysis of TAS2Rs revealed TAS2R4 as one of the most prominently regulated genes (1.59±0.22, p≤0.05). The proposed functional involvement of TAS2R4 in the PS was verified via a homozygote CRISPR Cas9 TAS2R4 knock out approach in HGT-1 cells.
These results suggest a functional role of TAS2R4 in the GA-evoked PS, a key mechanism of gastric acid secretion. Moreover, these data provide evidence for making red wine variants more stomach friendly.
Sensory tastings pointed out that GA [10 µM] tastes significantly more bitter than tap water, whereby the bitterness is increasing with the concentration of GA. In cell culture studies with HGT-1 cells, the lowest GA concentration perceived bitter was 10 µM, which also evoked a bitter receptor-associated response on the PS by HGT-1 cells. For the investigation of the GA-evoked proton secretion in a red wine matrix, HGT-1 cells were exposed to red wine samples spiked with up to 10 µM GA. These results demonstrated distinct effects of two red wines (Zweigelt and Blaufränkisch) on PS by HGT-1 cells to be modulated after spiking with GA up to a concentration of 10 µM GA. Subsequent gene expression analysis of TAS2Rs revealed TAS2R4 as one of the most prominently regulated genes (1.59±0.22, p≤0.05). The proposed functional involvement of TAS2R4 in the PS was verified via a homozygote CRISPR Cas9 TAS2R4 knock out approach in HGT-1 cells.
These results suggest a functional role of TAS2R4 in the GA-evoked PS, a key mechanism of gastric acid secretion. Moreover, these data provide evidence for making red wine variants more stomach friendly.