Tas2r125 functions as the main receptor for detecting bitterness of tea catechins in the oral cavity of mice

Effect of salivary gland removal on taste preference in mice

To evaluate the effect of decreased salivary secretion on taste preference, we investigated taste preference for five basic tastes by a 48 h two-bottle preference test using a mouse model (desalivated mice) that underwent surgical removal of three major salivary glands: the parotid, submandibular, and sublingual glands. In the desalivated mice, the avoidance behaviors for bitter and salty tastes and the attractive behaviors for sweet and umami tastes were significantly decreased. We confirmed that saliva is necessary to maintain normal taste preference. To estimate the cause of the preference changes, we investigated the effects of salivary gland removal on the expression of taste-related molecules in the taste buds. No apparent changes were observed in the expression levels or patterns of taste-related molecules after salivary gland removal. When the protein concentration and composition in the saliva were compared between the control and desalivated mice, the protein concentration decreased and its composition changed after major salivary gland removal. These results suggest that changes in protein concentration and composition in the saliva may be one of the factors responsible for the changes in taste preferences observed in the desalivated mice.

Effect of Brewing Conditions on Antioxidant Properties of Ginkgo biloba Leaves Infusion

Due to the growing awareness of the importance of healthy eating in society, there is an increasing interest in the use of herbs and low-processed, natural products. Ginkgo biloba is a raw material with a high pro-health potential, which is related to the high content of antioxidant compounds. The aim of the study was to determine the relationship between the antioxidant activity of Ginkgo biloba leaf infusions and the weighted amount of leaves and brewing time. In addition, a sensory analysis of the infusions obtained was carried out. The innovation is to determine the migration of micro- and macroelements to the infusion prepared from Ginkgo biloba depending on the leaves' weight used and the brewing time. The research showed the dependence of the antioxidant activity of the infusions and the migration of microelements on the size of the dried material and the brewing time. In the publication, the main factors influencing the quality of infusions were analysed, their mutual correlations were determined, and combinations showing the highest antioxidant activity and, at the same time, the highest sensory acceptability were selected.

Identification of mouse bitter taste receptors that respond to resveratrol, a bitter-tasting polyphenolic compound

The mouse bitter taste receptors (Tas2rs) that respond to resveratrol, a bitter-tasting polyphenolic compound, were identified. Among 35 members of the Tas2r family, Tas2r108, 109, 131, and 137 responded to resveratrol treatment. mRNA expression levels of Tas2r108 and Tas2r137 were higher than those of Tas2r109 and Tas2r131 in mouse circumvallate papillae, indicating that Tas2r108 and Tas2r137 may play important roles in detecting the bitterness of resveratrol in the oral cavity. The mRNA expression of Tas2r137 and Tas2r108 were also observed in several tissues, suggesting that Tas2r108 and Tas2r137 may also be involved in the physiological action of resveratrol.

Change in Taste Preference to Capsaicin and Catechin Due to Aging in Mice

Taste is a chemical sensation that primarily detects nutrients present in food, and maintenance of taste sensations is important for ensuring that older people have a balanced nutritional diet. While several reports have suggested that taste sensitivity changes with age, the molecular mechanisms underlying this phenomenon are still unclear. Previous studies on the matter have focused mainly on the relationship between aging and taste detection of specific basic taste-inducing substances, and other than for these basic substances, understanding of how aging affects the detection of taste is limited. Therefore, to understand the effect that aging has on the taste detection of some familiar substances found in our daily meals, namely capsaicin and catechin, we investigated age-related changes in taste preferences to capsaicin and catechin in young and old C57BL/6J mice using a 48-h two-bottle preference test. For the capsaicin stimuli, the mice showed avoidance behavior in a concentration-dependent manner. However, we observed that there was no significant difference in the preference ratio for capsaicin between young and old mice. For the catechin stimuli, although both age groups showed avoidance behavior in a concentration-dependent manner, the preference ratio in old mice showed significantly higher values than those in young mice. This suggests that catechin sensitivity is declined due to aging. Thus, we observed that catechin sensitivity decreases with age, but capsaicin sensitivity does not.

TAS2R20 variants confer dietary adaptation to high-quercitrin bamboo leaves in Qinling giant pandas

Sensitivity to bitter tastes provides animals with an important means of interacting with their environment and thus, influences their dietary preferences. Genetic variants encoding functionally distinct receptor types contribute to variation in bitter taste sensitivity. Our previous study showed that two nonsynonymous sites, A52V and Q296H, in the TAS2R20 gene are directionally selected in giant pandas from the Qinling Mountains, which are speculated to be the causative base-pair changes of Qinling pandas for the higher preference for bamboo leaves in comparison with other pandas. Here, we used functional expression in engineered cells to identify agonists of pTAS2R20 (i.e., giant panda's TAS2R20) and interrogated the differences in perception in the in vitro responses of pTAS2R20 variants to the agonists. Our results show that pTAS2R20 is specifically activated by quercitrin and that pTAS2R20 variants exhibit differences in the sensitivity of their response to the agonist. Compared with pTAS2R20 in pandas from other areas, the receptor variant with A52V and Q296H, which is most commonly found in Qinling pandas, confers a significantly decreased sensitivity to quercitrin. We subsequently quantified the quercitrin content of the leaves of bamboo distributed in the Qinling Mountains, which was found to be significantly higher than that of the leaves of bamboo from panda habitats in other areas. Our results suggest that the decreased sensitivity to quercitrin in Qinling pandas results in higher-quercitrin-containing bamboo leaves to be tasting less bitter to them and thus, influences their dietary preference. This study illustrates the genetic adaptation of Qinling pandas to their environments and provides a fine example of the functional effects of directional selection in the giant panda.