First identification of tannin-binding proteins in saliva of Papio hamadryas using MS/MS mass spectrometry

Salivary alpha-amylase stress reactivity in advanced-aged marmosets (Callithrix jacchus): Impacts of cognitive function and oral health status

Salivary alpha-amylase (sAA) is an enzyme found in saliva and is considered a noninvasive biomarker for sympathetic nervous system activity. While a wide range of sAA activity in response to stress has been reported in nonhuman primates, the effects of stress on sAA activity in common marmosets are still unknown. We tested the hypothesis that advanced age and cognitive function may have an impact on stress-related sAA reactivity in marmosets. Thirteen marmosets (nine males and five females) had saliva samples collected during a stressful condition (manual restraint stress) at two different time points, with a 60-min interval. On the next day, the animals underwent the object recognition test (ORT, a type of cognitive test), and then oral examinations. The animals were categorized into two age groups: old (10-13 years), and very old (15-22 years). Irrespective of age, sAA levels showed a significant difference between T1 (mean 2.07 ± 0.86 U/mL) and T2 samples (mean 1.03 ± 0.67 U/mL), with higher values observed at T1 (p < 0.001). The intra-assay coefficients of variation (CV) for low and high sAA concentrations were 10.79% and 8.17%, respectively, while the interassay CVs for low and high sAA concentrations were 6.39% and 4.38%, respectively. Oral health issues were common but did not significantly impact sAA levels. The ORT indicated that the animals could recognize an object placed in the cage 6 h after familiarization. In conclusion, all marmosets showed a higher sAA concentration in the first saliva sample as compared to the second saliva sample collected 1 h later, indicating adaptation to stress. No significant differences in sAA levels were observed between sexes, ORT performance, or oral health. Our results indicate that autonomic responsivity and cognitive (memory) functions were preserved even in very old marmosets.

Influence of tannic acid concentration on the physicochemical characteristics of saliva of spider monkeys (Ateles geoffroyi)

Tannins are a chemical defense mechanism of plants consumed by herbivores. Variations in salivary physicochemical characteristics such as pH, total protein concentration (TP), and presence of proline-rich proteins (PRPs) in animals have been reported as a mechanism to protect the oral cavity when consuming food with variations in pH and tannins. Variations in salivary physiochemistry as adaptations for consuming tannin-rich foods have been found in omnivorous and folivorous primates, but have not yet been reported in frugivorous species such as spider monkeys. We therefore assessed changes in pH using test strips, TP concentration by measuring absorbance at 595 nm in a spectrophotometer and salivary PRPs using the SDS-PAGE electrophoresis technique in the saliva of nine captive spider monkeys in response to the consumption of solutions with different concentrations of tannic acid. The results showed variations in pH, TP concentration and the presence and variation of possible salivary PRPs associated with tannic acid concentration. These findings suggest that spider monkeys may tailor their salivary physicochemical characteristics in response to the ingestion of potentially toxic compounds.

Plant secondary metabolites and primate food choices: A meta-analysis and future directions

The role of plant secondary metabolites (PSMs) in shaping the feeding decisions, habitat suitability, and reproductive success of herbivorous mammals has been a major theme in ecology for decades. Although primatologists were among the first to test these ideas, studies of PSMs in the feeding ecology of non-human primates have lagged in recent years, leading to a recent call for primatologists to reconnect with phytochemists to advance our understanding of the primate nutrition. To further this case, we present a formal meta-analysis of diet choice in response to PSMs based on field studies on wild primates. Our analysis of 155 measurements of primate feeding response to PSMs is drawn from 53 studies across 43 primate species which focussed primarily on the effect of three classes of PSMs tannins, phenolics, and alkaloids. We found a small but significant effect of PSMs on the diet choice of wild primates, which was largely driven by the finding that colobine primates showed a moderate aversion to condensed tannins. Conversely, there was no evidence that PSMs had a significant deterrent effect on food choices of non-colobine primates when all were combined into a single group. Furthermore, within the colobine primates, no other PSMs influenced feeding choices and we found no evidence that foregut anatomy significantly affected food choice with respect to PSMs. We suggest that methodological improvements related to experimental approaches and the adoption of new techniques including metabolomics are needed to advance our understanding of primate diet choice.

Human and Nonhuman Primate Lineage-Specific Footprints in the Salivary Proteome

Proteins in saliva are needed for preprocessing food in the mouth, maintenance of tooth mineralization, and protection from microbial pathogens. Novel insights into human lineage-specific functions of salivary proteins and clues to their involvement in human disease can be gained through evolutionary studies, as recently shown for salivary amylase AMY1 and salivary agglutinin DMBT1/gp340. However, the entirety of proteins in saliva, the salivary proteome, has not yet been investigated from an evolutionary perspective. Here, we compared the proteomes of human saliva and the saliva of our closest extant evolutionary relatives, chimpanzees and gorillas, using macaques as an outgroup, with the aim to uncover features in saliva protein composition that are unique to each species. We found that humans produce a waterier saliva, containing less than half total protein than great apes and Old World monkeys. For all major salivary proteins in humans, we could identify counterparts in chimpanzee and gorilla saliva. However, we discovered unique protein profiles in saliva of humans that were distinct from those of nonhuman primates. These findings open up the possibility that dietary differences and pathogenic pressures may have shaped a distinct salivary proteome in the human lineage.

Soil eaten by chacma baboons adsorbs polar plant secondary metabolites representative of those found in their diet

Geophagy, the deliberate consumption of earth materials, is common among humans and animals. However, its etiology and function(s) remain poorly understood. The major hypotheses about its adaptive functions are the supplementation of essential elements and the protection against temporary and chronic gastrointestinal (GI) distress. Because much less work has been done on the protection hypothesis, we investigated whether soil eaten by baboons protected their GI tract from plant secondary metabolites (PSMs) and described best laboratory practices for doing so. We tested a soil that baboons eat/preferred, a soil that baboons never eat/non-preferred, and two clay minerals, montmorillonite a 2:1 clay and kaolinite a 1:1 clay. These were processed using a technique that simulated physiological digestion. The phytochemical concentration of 10 compounds representative of three biosynthetic classes of compounds found in the baboon diet was then assessed with and without earth materials using high-performance liquid chromatography with diode-array detection (HPLC-DAD). The preferred soil was white, contained 1% halite, 45% illite/mica, 14% kaolinite, and 0.8% sand; the non-preferred soil was pink, contained 1% goethite and 1% hematite but no halite, 40% illite/mica, 19% kaolinite, and 3% sand. Polar phenolics and alkaloids were generally adsorbed at levels 10× higher than less polar terpenes. In terms of PSM adsorption, the montmorillonite was more effective than the kaolinite, which was more effective than the non-preferred soil, which was more effective than the preferred soil. Our findings suggest that HPLC-DAD is best practice for the assessment of PSM adsorption of earth materials due to its reproducibility and accuracy. Further, soil selection was not based on adsorption of PSMs, but on other criteria such as color, mouth feel, and taste. However, the consumption of earth containing clay minerals could be an effective strategy for protecting the GI tract from PSMs.

Salivary tannin-binding proteins are a pervasive strategy used by the folivorous/frugivorous black howler monkey

Dietary tannins can affect protein digestion and absorption, be toxic, and influence food selection by being astringent and bitter tasting. Animals that usually ingest tannins may regularly secrete tannin-binding salivary proteins (TBSPs) to counteract the negative effects of tannins or TBSPs production can be induced by a tannin-rich diet. In the wild, many primates regularly eat a diet that contains tannin-rich leaves and unripe fruit and it has been speculated that they have the physiological ability to cope with dietary tannins; however, details of their strategy remains unclear. Our research details the salivary protein composition of wild and zoo-living black howler monkeys (Alouatta pigra) feeding on natural versus manufactured low-tannin diets, and examines differences in TBSPs, mainly proline-rich proteins (PRPs), to determine whether production of these proteins is dependent on the tannin content of their food. We measured the pH, flow rate, and concentration of total protein and trichloroacetic acid soluble proteins (an index of PRPs) in saliva. Howler monkeys produced slightly alkaline saliva that may aid in the binding interaction between tannin and salivary proteins. We used gel electrophoresis to describe the salivary protein profile and this analysis along with a tannin-binding assay allowed us to detect several TBSPs in all individuals. We found no differences in the characteristics of saliva between wild and zoo-living monkeys. Our results suggest that black howler monkeys always secrete TBSPs even when fed on foods low in tannins. This strategy of constantly using this salivary anti-tannin defense enables them to obtain nutrients from plants that sometimes contain high levels of tannins and may help immediately to overcome the astringent sensation of their food allowing howler monkeys to eat tanniferous plants.

Phytoferritin association induced by EGCG inhibits protein degradation by proteases

Phytoferritin is a promising resource of non-heme iron supplementation, but it is not stable against degradation by proteases in the gastrointestinal tract. Therefore, how to improve the stability of ferritin in the presence of proteases is a challenge. Since (-)-epigallocatechin-3-gallate (EGCG) is rich in phenolic-hydroxyl groups, it could interact with ferritin through hydrogen bonds, thereby preventing protein from degradation. To confirm this idea, we focus on the interaction between EGCG and phytoferritin, and the consequence of such interaction. Results demonstrated that EGCG did interact with ferritin, and such interaction induced the change in the tertiary/quaternary structure of protein but not in its secondary structure. Furthermore, stopped-flow and dynamic light scattering (DLS) results showed that EGCG could trigger ferritin association. Consequently, such protein association markedly inhibited protein digestion by pepsin at pH 4.0 and by trypsin at pH 7.5. These findings raise the possibility to improve the stability of phytoferritin in the presence of proteases.

Rapid screening and identification of new soluble tannin-salivary protein aggregates in saliva by mass spectrometry (MALDI-TOF-TOF and FIA-ESI-MS)

Astringency is mainly attributed to the interaction between tannins and salivary proteins. Proline-rich proteins, histatins, and statherins are supposed to be the most reactive salivary proteins. This study aims to contribute to the knowledge of the tannin-protein binding process in saliva. It was identified for the first time in several soluble tannin-human salivary protein aggregates. A rapid mass spectrometry analytical method (MALDI-TOF and FIA-ESI-MS) was developed to identify new soluble tannin-human salivary protein aggregates. Three different tannins--procyanidin B3 (B3), procyanidin B2 gallate (B2G), and pentagalloylglucoside (PGG)--were tested to elucidate the tannin selectivity toward histatins, proline-rich proteins, and statherins in human saliva. A greater number of aggregates with a higher molecular weight was found when PGG was tested while no difference in the number and molecular mass range was observed in B3 or B2G salivary protein aggregates. This study confirms for the first time the bilateral selectivity of tannins and protein to yield soluble tannin-human salivary protein complexes. The results confirm that B3 and B2G are more selective than PGG. Furthermore, the families of proteins involved in the majority of B3-salivary protein soluble aggregates were primarly histatins, followed by basic proline-rich proteins and statherins. When B2G was tested, basic proline-rich proteins were involved in a greater number of aggregates, followed by histatines and statherins. Basic proline-rich proteins were also the family of proteins that formed a greater number of PGG-salivary protein aggregates followed by statherins and histatins. Acidic proline-rich proteins and glucosilated proline-rich proteins formed fewer soluble aggregates regardless of the tannin tested. The aggregation process was also found to be influenced by tannin and protein polarity. Indeed, the protein/tannin ratio of soluble aggregates increased with the tannin polarity. On the other hand, the only amphiphilic salivary proteins studied (histatins) formed a greater number of aggregates with the least polar tannin tested (B3).

Measurements of salivary alpha amylase and salivary cortisol in hominoid primates reveal within-species consistency and between-species differences

Salivary alpha amylase (sAA) is the most abundant enzyme in saliva. Studies in humans found variation in enzymatic activity of sAA across populations that could be linked to the copy number of loci for salivary amylase (AMY1), which was seen as an adaptive response to the intake of dietary starch. In addition to diet dependent variation, differences in sAA activity have been related to social stress. In a previous study, we found evidence for stress-induced variation in sAA activity in the bonobos, a hominoid primate that is closely related to humans. In this study, we explored patterns of variation in sAA activity in bonobos and three other hominoid primates, chimpanzee, gorilla, and orangutan to (a) examine if within-species differences in sAA activity found in bonobos are characteristic for hominoids and (b) assess the extent of variation in sAA activity between different species. The results revealed species-differences in sAA activity with gorillas and orangutans having higher basal sAA activity when compared to Pan. To assess the impact of stress, sAA values were related to cortisol levels measured in the same saliva samples. Gorillas and orangutans had low salivary cortisol concentrations and the highest cortisol concentration was found in samples from male bonobos, the group that also showed the highest sAA activity. Considering published information, the differences in sAA activity correspond with differences in AMY1 copy numbers and match with general features of natural diet. Studies on sAA activity have the potential to complement molecular studies and may contribute to research on feeding ecology and nutrition.

Effect of tannic acid on properties of soybean (Glycine max) seed ferritin: a model for interaction between naturally-occurring components in foodstuffs

There are many components with different properties co-existing in food, so interactions among these components are likely to occur, thereby affecting food quality. However, relatively little information is available on such interactions. In this study, we focus on the interaction between tannic acid (TA) and soybean seed ferritin (SSF), since they co-exist in many foodstuffs, and the consequence of this interaction. As expected, TA interacts with SSF, resulting in changes in the tertiary/quaternary structure of the protein, while having no effect on its primary and secondary structure. On one hand, such interaction leads to protein association, which markedly inhibited ferritin degradation by pepsin at pH 4.0 and trypsin at pH 7.5. On the other hand, iron release was faster with TA than with ascorbic acid, and such release has a negative effect on iron supplementation. These results help to understand the interactions of food components.

Saliva proteomics as an emerging, non-invasive tool to study livestock physiology, nutrition and diseases

Saliva is an extraordinary fluid in terms of research and diagnostic possibilities. Its composition in electrolytes, hormones and especially its proteome contains information about feeding status, nutritional requirements and adaptations to diet and environment, and also about health status of animals. It is easy to collect on a non-invasive and routine basis without any need for special training. Therefore, the analysis of salivary proteomes is going to emerge into a field of high interest with the future goal to maintain and improve livestock productivity and welfare. Moreover, the comprehensive analysis and identification of salivary proteins and peptides in whole and glandular saliva is a necessary pre-requisite to identify animal disease biomarkers and a powerful tool to better understand animal physiology. This review focuses on the different approaches used to study the salivary proteomes of farm animals, in respect to the physiology of nutrition and food perception in relation to food choices. The potential of animal saliva as a source of disease biomarkers will also be pointed out. Special emphasis is laid on the 'ruminating triad' - cattle, goat and sheep - as well as swine as major species of animal production in Western and Southern Europe.

Green tea ingestion by rats does not affect iron absorption but does alter the composition of the saliva proteome

We tested the hypothesis that rats adapt to the iron absorption inhibitory effects of tea by modifying the expression of salivary proteins. Thirty-six weanling rats were allocated into 6 groups. Two control groups were fed a semipurified diet containing 20 mg Fe(2+)/kg diet. Two groups were fed spray dried green tea infusion mixed into the diet (28.6 g tea/kg diet) and 2 groups were fed the control diet with a twice daily gavage of a tea solution (0.25 g tea/mL). Saliva samples were collected in 3 groups (control, gavage, and oral) on day 8 (acute) and in the remaining groups on day 31 (chronic). Iron absorption was assessed using a (58)Fe(3+) tracer administered on day 1 (acute) and day 24 (chronic). 2D gel electrophoresis and mass spectrometry were used to assess the composition of the saliva proteome. There was no significant difference in iron absorption between the 3 groups on either day 1 or day 24. Salivary proline-rich proteins and submandibular gland secretory protein increased to a greater extent in the oral group than in the gavage group, when compared to control, within the same exposure time period. Amylase, chitinase, deoxyribonuclease, cysteine-rich secretory protein 1, and parotid secretory protein all decreased to a greater extent in the oral tea group, compared to the control, within the same exposure time period. Our results show that green tea did not decrease iron absorption in rats but it did have a marked effect on the saliva proteome when given orally.