Impact of saliva incorporation on the rheological properties of in vitro gastric contents formulated from sour cream.

Rheological properties of gastric contents depend on the food ingested, and on the volume and composition of secretions from the host, which may vary. This study investigates the impact of saliva regular incorporation in the stomach after a meal on the rheological properties of gastric contents, considering two levels of salivary flow (low = 0.5 and high = 1.5 mL/min). In vitro chymes were obtained by mixing sour cream, simulated gastric fluid, two different volumes of oral fluid (at-rest human saliva, SSF for Simulated Salivary Fluid or water) and adjusting pH at 3. Chymes samples were characterized at 37°C for their particle size and rheological properties. Overall, particle size distribution was not different between samples: incorporating a larger volume of saliva resulted in more heterogeneity, but the surface area moment D[3,2] and volume moment D[4,3] did not differ significantly with the oral fluid type. Shear viscosity of chyme samples was higher when saliva was incorporated, in comparison with water or SSF. In addition, as shown from data extracted at γ ̇ $$ \dot{\gamma} $$ = 20 s-1 the higher the fluid volume the lower the shear viscosity, which is attributed to a dilution effect. However, this dilution effect was attenuated in the case of saliva, most likely due to its composition in organic compounds (e.g., mucins) contributing to the rheological properties of this biological fluid. In these in vitro conditions, both saliva and the salivation rate had a significant but slight impact on the rheological properties of gastric contents (of the order of 1-5 mPa s at γ ̇ $$ \dot{\gamma} $$ = 20 s-1).

Impact of age on the digestion of cream cheese formulated with opposite caseins to whey proteins ratios: An in vitro study.

Ageing leads to changes in the functionality of the digestive tract but the effect of age on digestion and absorption of nutrients remains unclear. The objective of this study was to investigate in vitro the digestion of two high-protein dairy products similar to cream cheese (24 % w/w proteins, 20 % w/w lipids) with opposite casein to whey protein ratios, 80:20 (WP-20), and 20:80 (WP-80). The new static digestion model adapted to the general older adult population (≥65 y.) proposed by INFOGEST was used, as well as the standard version of the protocol. Kinetics of proteolysis and lipolysis were compared between both models for each product, in the gastric and intestinal phases of digestion. In both cream cheeses, the degree of protein hydrolysis (DH-P) was significantly lower for older adults than for young adults at the end of the gastric phase (-19 % for WP-20, and -44 % for WP-80), and at the end of the intestinal phase (-16 % for WP-20, and -20 % for WP-80). The degree of lipid hydrolysis (DH-L) was also significantly lower for older adults than for young adults at the end of the digestion for WP-20 (-30 %), but interestingly it was not the case for WP-80 (similar DH-L were measured). Free fatty acids were also released faster from WP-80 than from WP-20 in both digestion conditions: after 5 min of intestinal digestion DH-L was already ≈32 % for WP-80 against 14 % for WP-20. This was attributed to the opposite casein to whey protein ratios, leading to the formation of different gel structures resulting in different patterns of deconstruction in the gastrointestinal tract. This study highlights the fact that it is essential to carefully consider the composition, structure, and digestibility of foods to develop products adapted to the specific needs of the older adult population.

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

Beneficial polyphenols in apples can reach the stomach as complexes formed with salivary proteins. The present study aimed at documenting the interactions between salivary proteins and cider apple polyphenols and the fate of complexes during gastric digestion. A polyphenolic extract was mixed with human saliva, and interactions were characterized by analyzing proteins and polyphenols in the insoluble and soluble fractions of the mixtures, before and after in vitro gastric digestion. Results confirmed that proline-rich proteins can efficiently precipitate polyphenols and suggested that two zinc-binding proteins can also form insoluble complexes with polyphenols. The classes of polyphenols involved in such complexes depended on the polyphenol-to-protein ratio. In vitro gastric digestion led to extensive proteolysis of salivary proteins, and we formulate the hypothesis that the resulting peptides can interact with and precipitate some procyanidins. Saliva may therefore partly modulate the bioaccessibility of at least procyanidins in the gastric compartment.

In vitro digestion of two protein-rich dairy products in the ageing gastrointestinal tract.

It is still unclear if changes in protein digestibility and absorption kinetics in old age may affect the anabolic effect of high-protein foods. The objective of this study was to investigate the digestion of two high-protein (10% w/w) dairy products in vitro: a fermented dairy product formulated with a ratio of whey proteins to caseins of 80 to 20% (WBD) and a Skyr containing mainly caseins. The new static in vitro digestion model adapted to the general older adult population (≥65 years) proposed by the INFOGEST international consortium was implemented to investigate the digestion of these products and compared with the standard version of the protocol. Kinetics of proteolysis was compared between both models for each product, in the gastric and intestinal phases of digestion. Protein hydrolysis was studied by the OPA method, SDS-PAGE, and LC-MS/MS, and amino acids were quantified by HPLC. Protein hydrolysis by pepsin was slower with the older adult model than with the young adult model, and consequently, in spite of a longer gastric phase duration, the degree of proteolysis (DH) at the end of the gastric phase was lower. Two different scenarios were observed depending on the type of dairy product studied: -10 and -40% DH for Skyr and WBD, respectively. In the intestinal phase, lower concentrations of free leucine were observed in older adult conditions (approx. -10%), but no significant differences in proteolysis were observed overall between the models. Therefore, the digestion conditions used influenced significantly the rate and extent of proteolysis in the gastric phase but not in the intestinal phase.

Feasibility of using a realistic food bolus for semi-dynamic in vitro gastric digestion of hard cheese with pH-stat monitoring of protein hydrolysis.

Oral processing of solid foods leads to boluses made of a human saliva and particles distributed in the size range âˆ¼ 0 to 5 mm. However, studies on the release of nutrients from realistic solid food boluses during digestion are scarce because such mechanisms are difficult to investigate in vivo, and in vitro experiments generally recommend to extensively mince solid foods during the oral stage. Similarly, it has previously been shown that the peptic hydrolysis of protein solutions during in vitro gastric digestion can be monitored by acid titration in both static and dynamic pH conditions, but such approach has never been evaluated in the presence of particles of several millimetres in size. The first objective of the study was therefore to test the feasibility of using a realistic food bolus for gastric digestion studies with a pH-stat monitoring of proteolysis, using Emmental cheese as a solid food and with consideration of gastric acidifying kinetics. Degree of hydrolysis (DH) of proteins was monitored from two series of experiments performed in the presence and absence of pepsin. Other DH measurements, estimated from an independent approach based on the amount of free NH2 groups (OPA method) contained by peptides released in the supernatant (UV absorbance) validated the pH-stat results. A second objective of this work was to test the possible influence of human saliva on gastric proteolysis (in comparison with a water-based bolus). Results showed that saliva slightly delayed initiation of proteolysis, which could be explained by the slightly higher initial pH of the saliva-based bolus, but had no statistical effects on pepsin activity. We conclude that acid titration with a pH-stat system can be a valuable approach to monitor the gastric in vitro proteolysis of realistic solid food boluses in dynamic pH conditions.

Quantitative magnetic resonance imaging of in vitro gastrointestinal digestion of a bread and cheese meal.

The monitoring of food degradation during gastrointestinal digestion is essential in understanding food structure impacts on the bioaccessibility and bioavailability of nutrients. Magnetic Resonance Imaging (MRI) has the unique ability to access information on changes in multi-scale structural features of foods in a spatially resolved and non-destructive way. Our objective was to exploit various opportunities offered by MRI for monitoring starch, lipid and protein hydrolysis, as well as food particle breakdown during the semi-dynamic in vitro gastrointestinal digestion of complex foods combined in a meal. The meal consisted of French bread, hard cheese and water (drink), with a realistic distribution of bolus particle sizes. The MRI approach was reinforced by parallel chemical analysis of all macronutrients in the supernatant. By combining different imaging protocols, quantitative MRI provided insights into a number of phenomena at the level of the cheese and bread particles and within the liquid phase that are hard to access through conventional approaches. MRI thus revealed the progressive ingress of fluids into the bread crust and the release of the gas trapped in the crumb, the erosion of cheese particles, the creaming of fat, the disappearance of small food particles and changes in liquid phase composition. Excellent agreement was obtained between the quantitative parameters extracted from the MRI images and the results of the chemical analysis, demonstrating the strong potential of MRI for the monitoring of in vitro gastrointestinal digestion. The present study proposes further improvements to fully exploit the capabilities of MRI and constitutes an important step towards the extension of quantitative MRI to in vivo studies.

Alterations in the Oral Microbiome Associated With Diabetes, Overweight, and Dietary Components.

The Mediterranean diet (MedDiet) represents the traditional food consumption patterns of people living in countries bordering the Mediterranean Sea and is associated with a reduced incidence of obesity and type-2 diabetes mellitus (T2DM). The objective of this study was to examine differences in the composition of the oral microbiome in older adults with T2DM and/or high body mass index (BMI) and whether the microbiome was influenced by elements of a MedDiet. Using a nested case-control design individuals affected by T2DM were selected from the Seniors-ENRICA-2 cohort concurrently with non-diabetic controls. BMI was measured, a validated dietary history taken, and adherence to a Mediterranean diet calculated using the MEDAS (Mediterranean Diet Adherence Screener) index. Oral health status was assessed by questionnaire and unstimulated whole mouth saliva was collected, and salivary flow rate calculated. Richness and diversity of the salivary microbiome were reduced in participants with T2DM compared to those without diabetes. The bacterial community structure in saliva showed distinct "signatures" or "salivatypes," characterized by predominance of particular bacterial genera. Salivatype 1 was more represented in subjects with T2DM, whilst those with obesity (BMI ≥ 30 kg/m2) had a predominance of salivatype 2, and control participants without T2DM or obesity had an increased presence of salivatype 3. There was an association of salivatype 1 with increased consumption of sugary snacks combined with reduced consumption of fish/shellfish and nuts. It can be concluded that the microbial community structure of saliva is altered in T2DM and obesity and is associated with altered consumption of particular food items. In order to further substantiate these observations a prospective study should be undertaken to assess the impact of diets aimed at modifying diabetic status and reducing weight.

Interactions between Salivary Proteins and Dietary Polyphenols: Potential Consequences on Gastrointestinal Digestive Events.

The present review documents the current knowledge and hypotheses on how polyphenols-saliva interactions may modulate the bioaccessibility or bioavailability of nutrients and highlights research prospects in the field. After an updated description of the different classes of dietary polyphenols and their modifications by food processing or digestion, an overview of interactions between salivary proteins and polyphenols (with an emphasis on tannins) is provided. In vitro studies show that the solubility of salivary protein-tannin complexes in gastric conditions depends on the degree of tannin polymerization, while complexes are partly solubilized by bile salts. Salivary proteins-polyphenols interactions may affect digestive processes. For example, polyphenols can bind to and inhibit salivary amylase, with downstream consequences on starch digestion. Some salivary proteins (PRPs) prevent tannin-induced reduced protein digestibility, probably through binding tannins before they interact with digestive proteases. Salivary proteins may also act as scavenger molecules to limit the intestinal uptake of tannins.

The salivary proteome reflects some traits of dietary habits in diabetic and non-diabetic older adults.

PURPOSE: Objective markers of usual diet are of interest as alternative or validating tools in nutritional epidemiology research. The main purpose of the work was to assess whether saliva protein composition can reflect dietary habits in older adults, and how type 2 diabetes impacted on the saliva-diet correlates. METHODS: 214 participants were selected from 2 European cohorts of community-dwelling older adults (3C-Bordeaux and Seniors-ENRICA-2), using a case-control design nested in each cohort. Cases were individuals with type 2 diabetes. Dietary information was obtained using the Mediterranean Diet Adherence Screener (MEDAS). Saliva was successfully obtained from 211 subjects, and its proteome analyzed by liquid chromatography-tandem mass spectrometry. RESULTS: The relative abundance of 246 saliva proteins was obtained across all participants. The salivary proteome differed depending on the intake level of some food groups (especially vegetables, fruits, sweet snacks and red meat), in a diabetic status- and cohort-specific manner. Gene Set Enrichment Analysis suggested that some biological processes were consistently affected by diet across cohorts, for example enhanced platelet degranulation in high consumers of sweet snacks. Minimal models were then fitted to predict dietary variables by sociodemographic, clinical and salivary proteome variables. For the food group «sweet snacks¼, selected salivary proteins contributed to the predictive model and improved its performance in the Seniors-ENRICA-2 cohort and when both cohorts were combined. CONCLUSION: Saliva proteome composition of elderly individuals can reflect some aspects of dietary patterns.

The role of overweight in the association between the Mediterranean diet and the risk of type 2 diabetes mellitus: a mediation analysis among 21 585 UK biobank participants.

BACKGROUND: There is growing evidence that the Mediterranean (Medi) diet may lower the risk of type 2 diabetes mellitus (T2DM). Whether this association is due to the Medi diet by itself or is mediated by a diet-associated lower rate of overweight is uncertain. Our aim was to disentangle these relationships among UK adults. METHODS: Based on 21 585 participants from the UK Biobank cohort, the adherence to the Medi diet (high fruits, vegetables, legumes, cereals, fish, olive oil; low meat, dairy products; and intermediate alcohol intakes) was assessed (range 0-18). Data on diabetes were self-reported, and overweight was defined as a body mass index (BMI) ≥ 25 kg/m². A mediation analysis was implemented to disentangle the role of overweight in the Medi diet-T2DM relationship. RESULTS: The average baseline Medi diet score was 8.8 [standard deviation (SD) 2.6]. During a mean follow-up of 6.1 years, 473 individuals developed T2DM. A higher adherence to a Medi diet (+1 point) was associated with 14% decreased risk of T2DM [hazard ratio (HR): 0.86, 95% confidence interval (CI): 0.82-0.90]. This association split into an indirect effect of 10%, mediated by lower odds of overweight (HR: 0.90, 95% CI: 0.87-0.92), and a direct effect of the Medi diet of 4% (HR: 0.96, 95% CI: 0.93-0.99), regardless of the effect mediated by overweight. CONCLUSIONS: Considered as a single mediator, reduced overweight mainly contributes to the association between greater Medi diet adherence and lower risk of T2DM on this British subsample. However, the direct effect of the diet on the risk of T2DM, even weaker, should not be overlooked.

Proteomic characterization of the mucosal pellicle formed in vitro on a cellular model of oral epithelium.

The oral mucosal pellicle is a thin lubricating layer generated by the binding of saliva proteins on epithelial oral cells. The protein composition of this biological structure has been to date studied by targeted analyses of specific salivary proteins. In order to perform a more exhaustive proteome characterization of pellicles, we used TR146 cells expressing or not the transmembrane mucin MUC1 and generated pellicles by incubation with human saliva and washing to remove unbound proteins. A suitable method was established for the in vitro isolation of the mucosal pellicle by "shaving" it from the cells using trypsin. The extracts, the washing solutions and the saliva used to constitute the pellicles were analyzed by LC MS/MS (data are available via ProteomeXchange with identifier PXD017268). Comparison of pellicle and saliva compositions evidenced the adsorption of proteins not previously reported as pellicle constituents such as proteins of the PLUNC family. Pellicles formed on TR146 and TR146/MUC1 were also analyzed and compared by protein label-free quantification. The two types of samples appeared as distinct clusters in multivariate analyses, but the discriminant proteins (Welch test p < .05, FDR < 0.1) were cellular rather than salivary proteins. SIGNIFICANCE: The oral mucosal pellicle is made of salivary proteins tightly bound to oral epithelial cells. It is essential to oral health, with biological functions depending largely on its protein constituents. Characterizing its proteome is difficult due to the intimate association of this protein layer to cell membranes. In this work, we report a trypsin "shaving" protocol which enabled to sample the pellicle formed on an in vitro cellular model of oral epithelium. Analyzing such samples by high-resolution mass spectrometry provided novel information on the mucosal pellicle composition. This work is therefore a good starting point for further characterization of this biological structure.

Understanding retention and metabolization of aroma compounds using an in vitro model of oral mucosa.

The mechanism leading to aroma persistence during eating is not fully described. This study aims at better understanding the role of the oral mucosa in this phenomenon. Release of 14 volatile compounds from different chemical classes was studied after exposure to in vitro models of oral mucosa, at equilibrium by Gas-Chromatography-Flame Ionization Detection (GC-FID) and in dynamic conditions by Proton Transfer Reaction- Mass Spectrometry (PTR-MS). Measurements at equilibrium showed that mucosal hydration reduced the release of only two compounds, pentan-2-one and linalool (p < 0.05), and suggested that cells could metabolize aroma compounds from different chemical families (penta-2,3-dione, trans-2-hexen-1-al, ethyl hexanoate, nonan- and decan-2-one). Dynamic analyses for pentan-2-one and octan-2-one evidenced that the constituents of the mucosal pellicle influenced release kinetics differently depending on molecule hydrophobicity. This work suggests that mucosal cells can metabolize aroma compounds and that non-covalent interactions occur between aroma compounds and oral mucosa depending on aroma chemical structure.

Nanoscale Mapping of the Physical Surface Properties of Human Buccal Cells and Changes Induced by Saliva.

The mucosal pellicle, also called salivary pellicle, is a thin biological layer made of salivary and epithelial constituents, lining oral mucosae. It contributes to their protection against microbiological, chemical, or mechanical insults. Pellicle formation depends on the cells' surface properties, and in turn the pellicle deeply modifies such properties. It has been reported that the expression of the transmembrane mucin MUC1 in oral epithelial cells improves the formation of the mucosal pellicle. Here, we describe an approach combining classical and functionalized tip atomic force microscopy and scanning microwave microscopy to characterize how MUC1 induces changes in buccal cells' morphology, hydrophobicity, and electric properties to elucidate the physicochemical mechanisms involved in the enhancement of the anchoring of salivary proteins. We show that MUC1 expression did not modify drastically the morphology of the epithelial cells' surface. MUC1 expression, however, resulted in the presence of more hydrophobic and more charged areas at the cell surface. The presence of salivary proteins decreased the highest attractive and repulsive forces recorded between the cell surface and a functionalized hydrophobic atomic force microscopy (AFM) tip, suggesting that the most hydrophobic and charged areas participate in the binding of salivary proteins. The cells' dielectric properties were altered by both MUC1 expression and the presence of a mucosal pellicle. We finally show that in the absence of MUC1, the pellicle appeared as a distinct layer poorly interacting with the cells' surface. This integrative AFM/scanning microwave microscopy approach may usefully describe the surface properties of various cell types, with relevance to the bioadhesion or biomimetics fields.

Biological films adhering to the oral soft tissues: Structure, composition, and potential impact on taste perception.

The role of free-flowing saliva in taste perception is increasingly recognized, but saliva is also present in the mouth as films intimately associated to soft or hard tissues. On mucosal surfaces, particularly on the tongue, the structure and composition of such films (including its microbial constitutive part) may play a particular role in the sense of taste due to their proximity with the taste anatomical structures. This review compiles the current knowledge on the structure of biological films adhering to oral mucosae and on their biochemical and microbiological composition, before presenting possible implications for taste perception. PRACTICAL APPLICATIONS: The understanding of the role of oral biological films on taste perception may provide new avenues of research and development for the industry or academia interested broadly in chemosensation.

Protein expression in submandibular glands of young rats is modified by a high-fat/high-sugar maternal diet.

OBJECTIVE: Maternal diet has consequences on many organs of the offspring, but salivary glands have received little attention despite the importance of the saliva secretory function in oral health and control of food intake. The objective of this work was therefore to document in rats the impact of maternal high-fat/high-sugar diet (Western Diet) on submandibular glands of the progeny. DESIGN: Sprague-Dawley rat dams were fed either a Western diet or control diet during gestation and lactation and their pups were sacrificed 25 days after birth. The pups' submandibular gland protein content was characterized by means of 2D-electrophoresis followed by LC-MS/MS. Data were further analyzed by Gene Ontology enrichment analysis and protein-protein interactions mapping. The expression of two specific proteins was also evaluated using immunohistochemistry. RESULTS: Combining both male and female pups (n = 18), proteome analysis revealed that proteins involved in protein quality control (e.g. heat shock proteins, proteasome sub-units) and microtubule proteins were over-expressed in Western diet conditions, which may translate intense metabolic activity. A cluster of proteins controlling oxidative stress (e.g. Glutathione peroxidases, peroxiredoxin) and enhancement of the antioxidant activity molecular function were also characteristic of maternal Western diet as well as under-expression of annexin A5. The down-regulating effect of maternal Western diet on Annexin A5 expression was significant only for males (p < 0.05). CONCLUSIONS: A maternal Western diet modifies the protein composition of the offspring's salivary glands, which may have consequences on the salivary function.

The Associations between Biochemical and Microbiological Variables and Taste Differ in Whole Saliva and in the Film Lining the Tongue.

The objective of this work was to investigate whether the biological film lining the tongue may play a role in taste perception. For that purpose, the tongue film and saliva of 21 healthy subjects were characterized, focusing on microorganisms and their main metabolic substrates and products. In parallel, taste sensitivity was evaluated using a test recently developed by our group, and the links between biological and sensory data were explored by a correlative approach. Saliva and tongue film differed significantly in biochemical composition (proportions of glucose, fructose, sucrose, and lactic, butyric, and acetic acids) and in microbiological profiles: compared to saliva, tongue film was characterized by significantly lower proportions of Bacteroidetes (p<0.001) and its main genus Prevotella (p<0.01) and significantly higher proportions of Firmicutes (p<0.01), Actinobacteria (p<0.001), and the genus Streptococcus (p<0.05). Generic taste sensitivity was linked to biological variables in the two compartments, but variables that appeared influent in saliva (flow, organic acids, proportion of Actinobacteria and Firmicutes) and in tongue film (sugars and proportions of Bacteroidetes) were not the same. This study points to two interesting areas in taste research: the oral microbiome and the specific characterization of the film lining the tongue.

Mechanisms of astringency: Structural alteration of the oral mucosal pellicle by dietary tannins and protective effect of bPRPs.

The interaction of tannins with salivary proteins is involved in astringency. This paper focussed on saliva lining oral mucosae, the mucosal pellicle. Using a cell-based model, the impact of two dietary tannins (EgC and EgCG) on the mucosal pellicle structure and properties was investigated by microscopic techniques. The role of basic Proline-Rich-Proteins (bPRPs) in protecting the mucosal pellicle was also evaluated. At low (0.05 mM) tannin concentration, below the sensory detection threshold, the distribution of salivary mucins MUC5B on cells remained unaffected. At 0.5 and 1 mM, MUC5B-tannin aggregates were observed and their size increased with tannin concentration and with galloylation. In addition, 3 mM EgCG resulted in higher friction forces measured by AFM. In presence of bPRPs, the size distribution of aggregates was greatly modified and tended to resemble that of the "no tannin" condition, highlighting that bPRPs have a protective effect against the structural alteration induced by dietary tannins.

The role of saliva in aroma release and perception.

Aroma perception is an important factor driving food acceptance. Volatile organic compounds (VOCs) are released from the food matrix and then reach the receptors located in the nasal cavity, leading to their perception. These steps are closely dependent on the physicochemical properties of the volatile compounds and the food matrix, but also on human physiology. Among the different physiological parameters involved, the literature reports that saliva has various effects on VOCs and therefore appears as a major actor impacting the perception of aroma. This article reviews how saliva takes part in aroma release, considering both in vitro and in vivo approaches, and how it may affect perception. It describes the direct mechanisms (molecular interactions, enzymatic conversion, salting-out effect, dilution) involving salivary components (salts, proteins including enzymes, microbiota) that can modify the release of aroma compounds. It also considers the indirect impact of saliva, such as changes of aroma diffusion through modification of the physicochemical properties of the food matrix.

Associations between food consumption patterns and saliva composition: Specificities of eating difficulties children.

Identifying objective markers of diet would be beneficial to research fields such as nutritional epidemiology. As a preliminary study on the validity of using saliva for this purpose, and in order to explore the relationship between saliva and diet, we focused on clearly contrasted groups of children: children with eating difficulties (ED) receiving at least 50% of their energy intake through artificial nutrition vs healthy controls (C). Saliva of ED and C children was analyzed by various methods (targeted biochemical analyses, 2-D electrophoresis coupled to MS, 1H NMR) and their diet was characterized using food frequency questionnaires, considering 148 food items grouped into 13 categories. Complete datasets were obtained for 16 ED and 16 C subjects (median age 4.7y and 5.0y, respectively) and the statistical link between salivary and dietary characteristics was studied by Multiple Factor Analysis (MFA). Overall, ED children showed as expected lower consumption frequency scores and higher food selectivity. The two groups of children differed in "diet/saliva" associations. Some distinctive salivary variables were common to both groups of children. For example, carbonic anhydrase 6 and the consumption frequency of biscuits & sweets and drinks were positively associated with the MFA axis 1 in C children, but oppositely associated in ED children. Specifically for ED children, abundant salivary proteins (cystatins, amylase, amylase fragments) and some metabolites (amino acids, galactose, lactate) correlated with axis 1, together with the consumption frequency of sauces & seasonings, bread & cereal products, ready-to-eat meals, fish, biscuits & sweets, drinks and potatoes. Specifically for C children, several proteins (serum albumin, haptoglobin, Igκ, apolipoprotein A-1, α-1 antitrypsin) correlated with axis 1, together with the consumption frequency of biscuits & sweets, milk & dairy products, drinks, fruit, meat and vegetables. This study demonstrates that the qualitative aspect of diet is linked to saliva composition, and that the associations between dietary consumption and salivary composition differ between groups of subjects with contrasted diets.

The membrane-associated MUC1 improves adhesion of salivary MUC5B on buccal cells. Application to development of an in vitro cellular model of oral epithelium.

OBJECTIVES: The mucosal pellicle is a thin layer of salivary proteins, mostly MUC5B mucins, anchored to epithelial oral cells. This pellicle is involved in protection of oral mucosae against abrasion, pathogenic microorganisms or chemical xenobiotics. The present study aimed at studying the involvement of MUC1 in mucosal pellicle formation and more specifically in salivary MUC5B binding using a cell-based model of oral epithelium. DESIGN: MUC1 mRNAs were not detected in TR146 cells, and therefore a stable cell line named TR146/MUC1 expressing this protein was developed by transfection. TR146 and TR146/MUC1 were incubated with human saliva in order to evaluate retention of MUC5B by epithelial cells. RESULTS: The cell surface of both TR146 and TR146/MUC1 was typical of a squamous non-keratinized epithelium, with the presence of numerous microplicae. After incubation for 2h with saliva diluted in culture medium (1:1) and two washes with PBS, saliva deposits on cells appeared as a loose filamentous thin network. MUC5B fluorescent immunostaining evidenced a heterogeneous lining of confluent cell cultures by this salivary mucin but with higher fluorescence on TR146/MUC1 cells. Semi-quantification of MUC5B bound to cells confirmed a better retention by TR146/MUC1, evaluated by Dot Blot (+34.1%, p<0.05) or by immunocytochemistry (+44%, p<0.001). CONCLUSION: The membrane-bound mucin MUC1 is a factor enhancing the formation of the mucosal pellicle by increasing the binding of salivary MUC5B to oral epithelial cells. An in vitro model suitable to study specifically the function and properties of the mucosal pellicle is proposed.