Abstract
There are hundreds of proteins in saliva. Although it has long been hypothesized that these proteins modulate taste by interacting with taste receptors or taste stimuli, the functional impact of these proteins on feeding remains relatively unexplored. We have developed a new technique for saliva collection that does not interfere with daily behavioral testing and allows us to explore the relationship between feeding behavior and salivary protein expression. First, we monitored the alterations in salivary protein expression while simultaneously monitoring the animals' feeding behavior and meal patterns on a custom control diet or on the same diet mixed with 3% tannic acid. We demonstrated that six protein bands increased in density with dietary tannic acid exposure. Several of these bands were significantly correlated with behaviors thought to represent both orosensory and postingestive signaling. In a follow-up experiment, unconditioned licking to 0.01–3% tannic acid solutions was measured during a brief-access taste test before and after exposure to the tannic acid diet. In this experiment, rats with salivary proteins upregulated found the tannin solution less aversive (i.e., licked more) than those in the control condition. These data suggest a role for salivary proteins in mediating changes in both orosensory and postingestive feedback.
Highlights
Variation in taste preferences in general, and bitter taste perception in particular, may play a key role in dietary choice, which has an uncontestable effect on human health
Larger tannin compounds are known to better interact with proline-rich proteins (PRPs) compared to smaller compounds [42], because PGG is a large tannin compound known to interact with PRPs, we have used PGG as a marker for size in this study
These data suggest that 67% of compounds in the tannic acid, are the same size or larger than PGG (Figure S1), we believe that the tannic acid supplied by Sigma contains large tannin compounds, which are capable of interacting with salivary proteins
Summary
Variation in taste preferences in general, and bitter taste perception in particular, may play a key role in dietary choice, which has an uncontestable effect on human health. Very little work has been done to investigate how salivary proteins interact with taste stimuli and alter taste sensitivity despite the fact that, under normal feeding and drinking conditions, taste compounds must inescapably mix with saliva before reaching their receptor targets. This sets the stage for potential modulation of the taste signal at its most fundamental level
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