Role of PROP taster status as a marker for individual differences in astringency perception, salivary proteins, and oral health

Astringency is a sensation commonly described as drying, roughing, and puckering of the oral surfaces, which is experienced upon consumption of tannin-rich foods. Although there is more than one mechanism at play, it is widely accepted that astringency is mainly caused when salivary proteins are precipitated by polyphenols in the mouth. Individual differences in the perception of astringency are well known but not well-understood. Sensitivity to the bitter compound, 6-n-propylthiouracil (PROP), controlled by polymorphisms in the TAS2R38 gene, has been observed to associate with differences in perception and liking for astringency. Additionally, previous research from our lab (Melis 2017) has shown PROP sensitivity may also be related to variation in salivary proteins released after stimulation with polyphenols. As these salivary proteins are key players in maintaining a healthy oral environment, PROP sensitivity may then also be a marker for oral health. The aims of this dissertation were to investigate if PROP sensitivity characterized by PROP Taster Status is a marker for astringency perception and liking as well as variation in salivary proteins. An exploratory aim of this dissertation was to understand if taste perception, salivary proteins and the oral microbiome are related to one another and if PROP Taster Status can help us understand these relationships. We selected cranberry polyphenols, native to the cranberry fruit, Vaccinium marcoporan as an ecologically relevant model to study these research questions. In the first study, subjects evaluated cranberry juice cocktail supplemented with varying levels of cranberry polyphenols for key flavor attributes and liking. PROP-classified groups did not perceive astringency differently from these samples but instead perceived differences in other flavor attributes. The results showed that other individual factors, such as ethnicity or gender, may have a larger influence than PROP taster status in the perception of astringency from cranberry juice. In the second study, we studied the time course of salivary proteins released after stimulation with cranberry-derived stimuli to understand if differences in astringency perception by the PROP groups may be explained by variation in salivary proteins. We observed both an effect of PROP taster status and gender on this phenomenon. Specifically, PROP super-tasters (ST) were observed to have higher levels of alpha amylase after stimulation with cranberry juice (p=0.014-0.000) in comparison to PROP non-tasters (NT); an additional interaction with gender was observed, whereby male STs had higher levels of bPRPs after stimulation with cranberry-derived polyphenols. This study showed that there is variation in the salivary protein response with respect to PROP taster status after exposure to an astringent stimulus. The final study explored the influence of PROP taster status on the interrelationship between taste perception, salivary proteins, and the oral microbiome. PROP non-tasters and super-tasters used a cranberry-polyphenol oral rinse for 11 days. Results showed evidence for differences in the oral microbiome at baseline but not at the end of the intervention. Further analyses revealed that the oral rinse altered the microbiome in NTs but not in STs. Using correlation networks, we observed that the oral environment of STs may have more complex relationships with salivary proteins and oral microbiome than NTs. Taken together, these studies suggest that the presence of polyphenols in the mouth initiates astringency and other oral sensations that are mediated by salivary proteins which play a crucial role in protecting the oral cavity against insult and injury. Even brief exposure to cranberry polyphenols was sufficient to modify one indicator of oral well-being, the oral microbiome. PROP status appears to be an integral part of this dynamic system and deserves more attention as a marker for individual differences in oral responses to polyphenols.Ph.D.Includes bibliographical reference