The Influence of (Poly)phenol Intake in Saliva Proteome: Short- and Medium-Term Effects of Apple

Abstract

The relationship between salivary proteome and dietary habits was studied in previous works, where a relationship between salivary proteins like cystatins and polyphenol/tannin levels in diet was observed. However, it remains to be elucidated if this association results from an effect of polyphenol-rich food ingestion on saliva composition. The aim of this work was to test the effects of apple intake on the saliva proteome, both in the short and medium term (after 4 days of continuous intake). By incubating saliva samples with apple phenolic-rich extract, protein bands containing α-amylase, S-type cystatins, and proline-rich proteins (PRPs) appeared in the fraction that precipitated, showing the potential of these (poly)phenols to precipitate salivary proteins. Among these, it was salivary cystatins that presented changes in their levels both in the saliva samples collected immediately after apple intake and in the ones collected after 4 days of intake of an extra amount of apple. These results support the thought that intake is reflected in the salivary proteome. The effect of a polyphenol-rich food, like the apple, on salivary cystatin levels is in line with results observed in animal models and, due to the involvement of these proteins in oral food perception, it would be interesting to explore in future studies the effect of these changes on sensory perception and acceptance of polyphenol-rich food.

Interactions between Salivary Proteins and Apple Polyphenols and the Fate of Complexes during Gastric Digestion

“…Here, although we cannot conclude whether amylase is bound to or not to apple polyphenols in supernatants, we show at least that it is only moderately precipitated. These results are in agreement with those of Louro et al, who used a protocol very similar to the one used in the present study. The authors reported that an apple polyphenol extract could precipitate amylase, but in fact, the results presented clearly show that amylase was present in much lower quantities in pellets than in supernatants.…”

“…The first result that was expected is the dose-dependent precipitation of PRP in the band at 27 kDa. This finding is in perfect agreement with another study which also described the concomitant increase in pellets and decrease in supernatants of a 27.5 kDa band after the interaction of whole saliva with an apple polyphenolic extract. The authors proposed that this band contained igκ chain C and PRP.…”

“…Results suggested that, for those two types of proteins, complexes were very stable in the in vitro gastric environment, while tannins were partly resolubilized during the simulated intestinal digestion, especially in the presence of bile salts. Another study used whole saliva acidified with 10% trifluoroacetic acid, which depletes saliva of proteins with molecular weight above 30 precipitates obtained after incubation with tannins were separated and submitted to in vitro gastric digestion. 11 The authors showed that the impact of gastric digestion depended on the degree of polymerization (DP) of the tannins, with complexes involving higher DP tannins (tetramers and above) significantly more stable than those involving lower DP tannins.…”