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

Unveiling the power of proteomics in advancing tropical animal health and production

Proteomics, the large-scale study of proteins in biological systems has emerged as a pivotal tool in the field of animal and veterinary sciences, mainly for investigating local and rustic breeds. Proteomics provides valuable insights into biological processes underlying animal growth, reproduction, health, and disease. In this review, we highlight the key proteomics technologies, methodologies, and their applications in domestic animals, particularly in the tropical context. We also discuss advances in proteomics research, including integration of multi-omics data, single-cell proteomics, and proteogenomics, all of which are promising for improving animal health, adaptation, welfare, and productivity. However, proteomics research in domestic animals faces challenges, such as sample preparation variation, data quality control, privacy and ethical considerations relating to animal welfare. We also provide recommendations for overcoming these challenges, emphasizing the importance of following best practices in sample preparation, data quality control, and ethical compliance. We therefore aim for this review to harness the full potential of proteomics in advancing our understanding of animal biology and ultimately improve animal health and productivity in local breeds of diverse animal species in a tropical context.

Interplay of hormones and metabolite excretion with fern pattern prove saliva as a potent indicator of male reproductive status in Kangayam breed cattle

Kangayam cattle are one of the drought breeds in India with distinct attributes. Agricultural transformation has led to a decline in many pure-breed indigenous cattle, including the Kangayam breed. Hence, a study on the reproductive physiology of male Kangayam breed cattle is necessary to disentangle problems in the area of livestock improvement. In this study, we investigated the relationship between serum hormones and bio-constituents and ascertained the potential of saliva as an indicator of the reproductive status of Kangayam cattle (Bos indicus). The present study confirms that cholesterol was higher in intact males and lower in prepubertal and castrated males. Testosterone levels were also higher in intact males than in castrated or prepubertal males. Hence, it can be inferred that high cholesterol levels contribute to active derivatization of testosterone in intact males. In contrast, reduced cholesterol availability leads to decreased testosterone synthesis in castrated and prepubertal males. Furthermore, it is reasonable to speculate that testosterone could have influenced salivary fern patterns in intact males, and thus, fern-like crystallization in the saliva was apparent. The unique salivary compounds identified through GC-MS across various reproductive statuses of Kangayam males may advertise their physiological status to conspecifics. In addition, the presence of odorant-binding protein (OBP) in saliva further supports its role in olfactory communication. This study attested to a posssible interlink between gonadal status and serum biochemical profiles. The salivary fern pattern revealed in this study can be used as a predictive tool, and the presence of putative volatiles and OBP adds evidence to the role of saliva in chemical communication.

Metabolomics reveals early pregnancy biomarkers in sows: a non-invasive diagnostic approach

In an effort to enhance reproductive management and reduce non-productive periods in swine breeding, this study presents a novel, non-invasive metabolomics approach for the identification of early pregnancy biomarkers in sows. Utilizing an untargeted metabolomics approach with mass spectrometry analysis, we examined saliva samples from pregnant (n = 6) and non-pregnant control sows (n = 6, artificially inseminated with non-viable sperm). Our analysis revealed 286 differentially expressed metabolites, with 152 being up-regulated and 134 down-regulated in the pregnant group. Among these, three metabolites, namely Hyodeoxycholic acid, 2'-deoxyguanosine, and Thymidine, emerged as potential early pregnancy biomarkers. These biomarkers were further evaluated using targeted LC-MS/MS quantification and qualification, accompanied by ROC curve analysis. The study confirmed Hyodeoxycholic acid and 2'-deoxyguanosine as promising biomarkers for early pregnancy detection, offering potential for future implementation in swine production environments. This research establishes a robust theoretical foundation for the development of innovative molecular diagnostic techniques and explores new avenues for molecular genetic breeding and non-invasive diagnostics, ultimately enhancing fertility and productivity in sow herds.

Comparison of the Effect of Two Different Handling Conditions at Slaughter in Saliva Analytes in Pigs

In this report, different handling conditions at slaughterhouse were studied to assess changes in salivary biomarkers. For this purpose, finishing pigs were divided into two groups, one in which handling was improved to minimize stress (Group A, n = 24, transported and stabled at the slaughterhouse at low density without mixing with unfamiliar animals throughout the whole process) and another one in which animals had a more stressful handling process (Group B, n = 24, transported and stabled at high density with unfamiliar animals). Saliva samples were taken the day before transport to the slaughterhouse at 8:00 a.m. (B0) and 12:00 a.m. (B4), and the day of slaughter just after unloading animals at the slaughterhouse at approximately 8:00 a.m. (S0) and after 4 h of lairage at approximately 12:00 a.m. (S4). Group B showed significantly higher cortisol, total esterase activity, oxytocin, adenosine deaminase and haptoglobin levels than the Group A at both S0 and S4 sampling times, and higher levels of calprotectin and creatine kinase at S4 sampling time. This report indicates that differences in the way in which the pigs are handled at the slaughterhouse can lead to changes in salivary biomarkers and opens the possibility of the use of biomarker at slaughter to monitor handling conditions.

Proteomic Analysis of Salivary Extracellular Vesicles from COVID-19 Patients Reveals a Specific Anti-COVID-19 Response Protein Signature

Despite the understanding of the coronavirus disease-19 (COVID-19), the role of salivary extracellular vesicles (sEVs) in COVID-19 remains unclear. Exploring the proteomic cargo of sEVs could prove valuable for diagnostic and prognostic purposes in assessing COVID-19. The proteomic cargo of sEVs from COVID-19(+) subjects and their healthy close contacts (HCC) was explored. sEVs were isolated by ultracentrifugation from unstimulated saliva samples, and subsequently characterized through nanoparticle tracking, transmission electron microscopy, and Western blot analyses. The proteomic cargo of sEVs was processed by LC-MS/MS. sEVs were morphologically compatible with EVs, with the presence of Syntenin-1 and CD81 EV markers. The sEV pellet showed 1417 proteins: 1288 in COVID-19(+) cases and 1382 in HCC. In total, 124 proteins were differentially expressed in sEVs from COVID-19(+) subjects. "Coronavirus-disease response", "complement and coagulation cascades", and "PMN extracellular trap formation" were the most enriched KEGG pathways in COVID-19(+) cases. The most represented biological processes were "Hemoglobin and haptoglobin binding" and "oxygen carrier activity", and the best-denoted molecular functions were "regulated exocytosis and secretion" and "leucocyte and PMN mediated immunity". sEV proteomic cargo in COVID-19(+) suggests activity related to immune response processes, oxygen transport, and antioxidant mechanisms. In contrast, in HCC, sEV signature profiles are mainly associated with epithelial homeostasis.

Advances in Research on Pig Salivary Analytes: A Window to Reveal Pig Health and Physiological Status

Saliva is an important exocrine fluid that is easy to collect and is a complex mixture of proteins and other molecules from multiple sources from which considerable biological information can be mined. Pig saliva, as an easily available biological liquid rich in bioactive ingredients, is rich in nucleic acid analytes, such as eggs, enzymes, amino acids, sugars, etc. The expression levels of these components in different diseases have received extensive attention, and the analysis of specific proteins, metabolites, and biological compositions in pig saliva has become a new direction for disease diagnosis and treatment. The study of the changes in analytes in pig saliva can provide a new strategy for early diagnosis, prognosis assessment, and treatment of diseases. In this paper, the detection methods and research progress of porcine salivary analytes are reviewed, the application and research progress of porcine salivary analytes in diseases are discussed, and the future application prospect is presented.

Saliva Sampling Material Matters: Effects on the Results of Saliva Analysis in Pigs

The use of saliva as a biological sample from pigs is of high practical interest because blood collection from pigs is difficult and stressful. In this study, the influence of two different materials, a cotton roll and a polypropylene sponge, in porcine saliva collection was evaluated. For this purpose, the effect of the material used for sampling was evaluated in a panel of 13 analytes, including those related to stress (cortisol and oxytocin), inflammation and immunity (adenosine deaminase, haptoglobin and myeloperoxidase), redox homeostasis (the cupric reducing ability of saliva, the ferric reducing activity of saliva, and the Trolox equivalent antioxidant capacity), and sepsis (procalcitonin), as well as other routine analytes related to metabolism and different tissues and organs, such as lactate dehydrogenase, creatine kinase, urea, and total protein concentration. The polypropylene sponge provided a higher sample volume than the cotton roll. Although the results of some salivary analytes were equivalent for both materials, other analytes, such as creatine kinase, haptoglobin and total proteins, showed significant differences depending on the material used for saliva collection. Therefore, the type of material used for salivary collection in pigs should be considered when interpreting the results of analyses of the salivary analytes.

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

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.

Changes in the Saliva Proteome of Pigs with Diarrhoea Caused by Escherichia coli

Escherichia coli represents the main cause of diarrhoea in pigs. Saliva can provide information about the pathophysiology of diseases and be a source of biomarkers. We aimed to identify changes in the salivary proteome of pigs with diarrhoea caused by E. coli. Saliva samples were collected from 10 pigs with this disease and 10 matched healthy controls. SDS-PAGE (1DE) and two-dimensional gel electrophoresis (2DE) were performed, and significantly different protein bands and spots were identified by mass spectrometry. For validation, adenosine deaminase (ADA) was measured in 28 healthy and 28 diseased pigs. In 1DE, increases in lipocalin and IgA bands were observed for diseased pigs, whereas bands containing proteins such as odorant-binding protein and/or prolactin-inducible protein presented decreased concentrations. Two-dimensional gel electrophoresis (2DE) results showed that saliva from E. coli animals presented higher expression levels of lipocalin, ADA, IgA and albumin peptides, being ADA activity increased in the diseased pigs in the validation study. Spots containing alpha-amylase, carbonic anhydrase VI, and whole albumin were decreased in diseased animals. Overall, pigs with diarrhoea caused by E. coli have changes in proteins in their saliva related to various pathophysiological mechanisms such as inflammation and immune function and could potentially be biomarkers of this disease.

A workflow for automatic, high precision livestock diagnostic screening of locomotor kinematics

Locomotor kinematics have been challenging inputs for automated diagnostic screening of livestock. Locomotion is a highly variable behavior, and influenced by subject characteristics (e.g., body mass, size, age, disease). We assemble a set of methods from different scientific disciplines, composing an automatic, high through-put workflow which can disentangle behavioral complexity and generate precise individual indicators of non-normal behavior for application in diagnostics and research. For this study, piglets (Sus domesticus) were filmed from lateral perspective during their first 10 h of life, an age at which maturation is quick and body mass and size have major consequences for survival. We then apply deep learning methods for point digitization, calculate joint angle profiles, and apply information-preserving transformations to retrieve a multivariate kinematic data set. We train probabilistic models to infer subject characteristics from kinematics. Model accuracy was validated for strides from piglets of normal birth weight (i.e., the category it was trained on), but the models infer the body mass and size of low birth weight (LBW) piglets (which were left out of training, out-of-sample inference) to be "normal." The age of some (but not all) low birth weight individuals was underestimated, indicating developmental delay. Such individuals could be identified automatically, inspected, and treated accordingly. This workflow has potential for automatic, precise screening in livestock management.

Trace Elements and Ferritin in Pig Saliva: Variations during Fattening, Time of Sampling, Effect of Dirtiness and Stability under Different Storage Conditions

The objective of this study was to evaluate the possible changes of zinc (Zn), copper (Cu), iron (Fe) and ferritin during the entire productive cycle in fattening pigs and at different diurnal sampling times. Moreover, the possible effects of the presence of pen contaminants and storage stability at different temperature conditions were assessed. The analytes changed along the different phases of the fattening productive cycle, showing, in general, higher values at the initial phases. In addition, statistically significant variations were found in Zn and Cu measurements at different sampling times of the day. In the spectrophotometric assays, the values of all analytes significantly increased after adding high concentrations of feces or feed. However, when low concentrations of feces or feed were added, only Cu showed a significant increase. Overall, the salivary levels of Zn, Cu, Fe and ferritin in pigs can change during different fattening phases and the different hours of the day. These analytes were more stable at −80 °C and, if saliva is contaminated with feces or feed, it can lead to an increase in these analytes.

Diet and phytogenic supplementation substantially modulate the salivary proteome in dairy cows

Phytogenic compounds may influence salivation or salivary properties. However, their effects on the bovine salivary proteome have not been evaluated. We investigated changes in the bovine salivary proteome due to transition from forage to high-concentrate diet, with and without supplementation with a phytogenic feed additive. Eight non-lactating cows were fed forage, then transitioned to a 65% concentrate diet (DM basis) over a week. Cows were control (n = 4, CON) or supplemented with a phytogenic feed additive (n = 4, PHY). Proteomic analysis was conducted using liquid chromatography coupled with mass spectrometry. We identified 1233 proteins; 878 were bovine proteins, 189 corresponded to bacteria, and 166 were plant proteins. Between forage and high-concentrate, 139 proteins were differentially abundant (P < 0.05), with 48 proteins having a log2FC difference > |2|. The salivary proteome reflected shifts in processes involving nutrient utilization, body tissue accretion, and immune response. Between PHY and CON, 195 proteins were differently abundant (P < 0.05), with 37 having a log2FC difference > |2|; 86 proteins were increased by PHY, including proteins involved in smell recognition. Many differentially abundant proteins correlated (r > |0.70|) with salivary bicarbonate, total mucins or pH. Results provide novel insights into the bovine salivary proteome using a non-invasive approach, and the association of specific proteins with major salivary properties influencing rumen homeostasis. SIGNIFICANCE: Phytogenic compounds may stimulate salivation due to their olfactory properties, but their effects on the salivary proteome have not been investigated. We investigated the effect of high-concentrate diets and supplementation with a phytogenic additive on the salivary proteome of cows. We show that analysis of cows' saliva can be a non-invasive approach to detect effects occurring not only in the gut, but also systemically including indications for gut health and immune response. Thus, results provide unique insights into the bovine salivary proteome, and will have a crucial contribution to further understand animal response in terms of nutrient utilization and immune activity due to the change from forage to a high-energy diet. Additionally, our findings reveal changes due to supplementation with a phytogenic feed additive with regard to health and olfactory stimulation. Furthermore, findings suggest an association between salivary proteins and other components like bicarbonate content.

Comparative Analysis of Saliva and Plasma Proteins Patterns in Pregnant Cows—Preliminary Studies

Simple Summary

One of the most crucial topics about cattle breeding is pregnancy. During this state, there are many changes in protein expression and abundance. These changes find reflection not only in plasma protein patterns but also in saliva, which is easier to obtain than blood. The aim of this study was the analysis of plasma and salivary protein profiles in pregnant cows in order to search for valuable markers of pregnancy status. In this study, the presence of apolipoproteins possibly related to bovine pregnancy was confirmed both in plasma and saliva. This means that saliva can be considered a good source of information about the condition of the organism, including during pregnancy. It is possible that the comparison of salivary and plasma proteomes can be a helpful tool to assess the pregnancy status of cattle, and can be useful for developing rapid tests from saliva.

Abstract

Pregnancy is a physiological state that can be described, from a biochemical point of view, using protein patterns. The present study focused on the comparison of protein patterns between the saliva and plasma of pregnant cows to search for possible markers which are present both in plasma and saliva. Saliva and plasma were collected from healthy, pregnant (3–4 months) and non-pregnant (C; n = 4) cows aged between 4 and 8 years (P; n = 8) from the same farm. Biological material was analyzed using 2D electrophoresis and MS identification. Among identified spots, there were those which could be related to pregnancy (e.g., apolipoproteins I and II in all examined matrices or transforming growth factor-beta-induced protein ig-h3 in albumin-free plasma) as well as those which are responsible for regulating of cellular processes (e.g., pyruvate kinase and aspartate aminotransferase in all examined matrices, or lactate dehydrogenase, phosphoglycerate kinase, and NADH dehydrogenase in plasma). Further identification of common spots and those only specific to saliva as well as the comparison between other periods of pregnancy are necessary; it is already clear that saliva can be considered a valuable diagnostic matrix containing potential markers of physiological and pathological status.

Effects of pen faeces and feed contamination in biomarkers determination in oral fluid of pigs

The present study aims to evaluate the possible effects of the presence of pen faeces and feed on the measurement of a panel of biomarkers in porcine oral fluid. For this, clean porcine oral fluid was pooled and incubated with two different concentrations of pen faeces or feed representing a high or low level of contamination with each material. In addition, these pools were aliquoted and subjected to centrifugation, filtration or chemical clarification to evaluate if these techniques could revert the effects of those contaminants in biomarker evaluation. A panel of 21 biomarkers that assessed stress, inflammation, immune system and redox homeostasis among others, were measured for all aliquots. Changes of statistical relevance (p < 0.05) in oral fluid contaminated with pen faeces or feed versus untreated samples were observed for all methods employed with the exception of adenosine deaminase (ADA) and creatine kinase (CK) in oral fluid contaminated with pen faeces or feed. Pen faeces did not affect the measurement of haptoglobin, superoxide dismutase, CK, lactate dehydrogenase (LDH), ADA and cortisol (when the latter is measured by chemiluminescence); while uric acid, LDH, CK, ADA, and hydrogen peroxide methods were not affected by the presence of feed in oral fluid. The effects of centrifugation, filtration or chemical clarification with chitosan in these contaminated samples were modest and for most cases did not caused baseline levels on the measured biomarkers. In conclusion, the presence of pen faeces or feed in porcine oral fluid can interfere with the results obtained when analytes are measured.

Non-Invasive Nasal Discharge Fluid and Other Body Fluid Biomarkers in Alzheimer’s Disease

The key to current Alzheimer’s disease (AD) therapy is the early diagnosis for prompt intervention, since available treatments only slow the disease progression. Therefore, this lack of promising therapies has called for diagnostic screening tests to identify those likely to develop full-blown AD. Recent AD diagnosis guidelines incorporated core biomarker analyses into criteria, including amyloid-β (Aβ), total-tau (T-tau), and phosphorylated tau (P-tau). Though effective, the accessibility of screening tests involving conventional cerebrospinal fluid (CSF)- and blood-based analyses is often hindered by the invasiveness and high cost. In an attempt to overcome these shortcomings, biomarker profiling research using non-invasive body fluid has shown the potential to capture the pathological changes in the patients’ bodies. These novel non-invasive body fluid biomarkers for AD have emerged as diagnostic and pathological targets. Here, we review the potential peripheral biomarkers, including non-invasive peripheral body fluids of nasal discharge, tear, saliva, and urine for AD.

Changes in a Comprehensive Profile of Saliva Analytes in Fattening Pigs during a Complete Productive Cycle: A Longitudinal Study

Simple Summary

The aim of this study was to evaluate whether a panel of 29 salivary biomarkers of stress, immunity, inflammation, redox homeostasis and other physiological functions can change in healthy fattening pigs when monitoring the different phases of their productive cycle and can be influenced by various sources of variations such as gender and performance parameters. Several analytes showed changes due to the productive cycle, with a majority of the analytes showing higher values at lactation and at the beginning of nursery. Additionally, differences were seen due to sex. These differences can be related in some cases with performance parameters and should be taken into consideration for an appropriate interpretation of the analytes.

Abstract

A comprehensive panel of 29 salivary analytes was measured in fattening pigs to evaluate its possible changes along their productive cycle. The identification of those changes would allow a better interpretation of the results according to the productive phase of the animal. Saliva samples were obtained from 49 Large-White pigs (24 females, 25 males) in suckling phase, at the beginning and the end of the nursery phase, and at the beginning and the end of the growing phase. Several analytes changed according to the phase of the productive cycle, with most of the analytes showing higher values at lactation and at the beginning of nursery. Additionally, differences were seen due to sex. When possible relations between performance parameters and analytes were evaluated, significant positive but weak relationships were found between weight at birth and salivary γ-glutamyl transferase, and between back-fat thickness and salivary lactate dehydrogenase. In conclusion, differences in the values of salivary analytes can be found in fattening pigs depending on the productive phase and sex of the animals.

Changes in salivary analytes in cows due to the in vitro presence of feed

BACKGROUND

The effect in a sialochemistry profile of the presence of usually available feed in dairy cows was evaluated by an in vitro experiment. For this purpose, a pooled clean saliva from five healthy dairy cows was incubated five times with a standard feed based on a total mixed ration (F), wheat hay (H), and grass (G). The salivary panel was integrated by biomarkers of stress (cortisol -sCor-, salivary alpha-amylase -sAA-, butyrylcholinesterase -BChE-, total esterase -TEA-, and lipase -Lip-), immunity (adenosine deaminase -ADA-), oxidative status (Trolox equivalent antioxidant capacity -TEAC-, the ferric reducing ability of saliva -FRAS-, the cupric reducing antioxidant capacity -CUPRAC-, uric acid, and advanced oxidation protein products -AOPP-), and enzymes, proteins, and minerals of general metabolism and markers of liver, muscle, and renal damage (aspartate aminotransferase -AST-, alanine aminotransferase -ALP-, γ-glutamyl transferase -gGT-, lactate dehydrogenase -LDH-, creatine kinase -CK-, creatinine, urea, triglycerides, glucose, lactate, total protein, phosphorus, and total calcium).

RESULTS

Most of the evaluated analytes showed a coefficient of variations (CV) higher than 15% and/or significant changes compared with the clean saliva when feed was present. Some analytes, such as the oxidative status biomarkers (CV > 80%), AST (CV > 60%), or glucose (CV > 100%), showed significant changes with all the feed types tested. Others showed significant differences only with certain types of feed, such as LDH with F (CV > 60%) or triglycerides with F (CV > 100%) and H (CV > 95%). However, sCor or gGT remained unchanged (CV < 15%, P > 0.05) in all the treatments.

CONCLUSIONS

The presence of feed can produce changes in most of the analytes measured in cows' saliva, being of high importance to consider this factor when saliva is used as a sample to avoid errors in the interpretation of the results.

Saliva Diagnostics

Cancer remains one of the leading causes of death, and early detection of this disease is crucial for increasing survival rates. Although cancer can be diagnosed following tissue biopsy, the biopsy procedure is invasive; liquid biopsy provides an alternative that is more comfortable for the patient. While blood, urine, and cerebral spinal fluid can all be used as a source of liquid biopsy, saliva is an ideal source of body fluid that is readily available and easily collected in the most noninvasive manner. Characterization of salivary constituents in the disease setting provides critical data for understanding pathophysiology and the evaluation of diagnostic potential. The aim of saliva diagnostics is therefore to develop a rapid and noninvasive detection of oral and systemic diseases that could be used together with compact analysis systems in the clinic to facilitate point-of-care diagnostics.

Changes in Oxidative Status Biomarkers in Saliva and Serum in the Equine Gastric Ulcer Syndrome and Colic of Intestinal Aetiology: A Pilot Study

Simple Summary

Gastric ulcers and colic of intestinal aetiology (CIE) are highly prevalent diseases in domestic horses, with a negative impact on equine sport and breeding life. Therefore, the studies investigating possible biomarkers for their diagnosis or clarifying their pathophysiology are of high interest. Oxidative status changes have been reported in both diseases, but only in the blood. However, saliva may be a relevant source of oxidative status biomarkers not yet assessed in horses with interesting advantages, owing to its non-invasive collection. Hence, this study aimed to validate in both saliva and serum automated assays for the measurement of oxidative status biomarkers and assess them in horses suffering gastric ulcer diseases (squamous and/or glandular) and CIE, studying their possible relationship with their inflammatory and immunity status. It was found that horses with glandular mucosa ulcers showed higher levels of some antioxidant and oxidative biomarkers in saliva correlating with a marker of the immune system such as salivary adenosine deaminase. Horses suffering from CIE had increases in serum uric acid associated with their systemic inflammatory response and outcome of the disease. In conclusion, some oxidative status analytes can be automatically measured in horses’ saliva and serum and may potentially be assessed as biomarkers of gastric ulcers and CIE.

Abstract

Changes in the oxidative status of the blood of horses suffering from gastric ulcers and colic of intestinal aetiology (CIE) have been reported. However, saliva can also be a source of biomarkers of oxidative status. Therefore, this study aims to validate automated assays for the measurement of oxidative status biomarkers (ferric reducing ability of saliva/serum—FRAS/FRAP, cupric reducing antioxidant capacity—CUPRAC, the Trolox equivalent antioxidant capacity—TEAC, uric acid, and advanced oxidation protein products—AOPP) in the saliva and serum of horses, to assess their changes in the different ulcer gastric diseases (squamous—ESGD and glandular—EGGD) and CIE, and to evaluate their relationship with serum amyloid A (SAA), adenosine deaminase (ADA), and the systemic inflammatory response syndrome (SIRS) status. The assays showed a low imprecision and good linearity with enough sensitivity in both fluids. In EGGD, higher levels of FRAS, uric acid, and AOPP in saliva were observed compared to the healthy group, correlating with the salivary ADA levels. Horses with CIE showed increases in uric acid concentrations in serum associated with their SIRS status and outcome of the disease. In conclusion, analytes related to the oxidative status can be measured in the saliva and serum from horses by automated assays, and some of them can potentially be assessed as biomarkers in horses with gastric ulcers and CIE.

Basics for the potential use of saliva to evaluate stress, inflammation, immune system, and redox homeostasis in pigs

The use of saliva as a biological sample has many advantages, being especially relevant in pigs where the blood collection is highly stressful and painful, both for the animal and the staff in charge of the sampling. Currently one of the main uses of saliva is for diagnosis and detection of infectious diseases, but the saliva can also be used to measure biomarkers that can provide information of stress, inflammation, immune response and redox homeostasis. This review will be focused on the analytes that can be used for such evaluations. Emphasis will be given in providing data of practical use about their physiological basis, how they can be measured, and their interpretation. In addition, some general rules regarding sampling and saliva storage are provided and the concept of sialochemistry will be addressed. There is still a need for more data and knowledge for most of these biomarkers to optimize their use, application, and interpretation. However, this review provides updated data to illustrate that besides the detection of pathogens in saliva, additional interesting applicative information regarding pigs´ welfare and health can be obtained from this fluid. Information that can potentially be applied to other animal species as well as to humans.

Molecularly Imprinted Polymers in Diagnostics: Accessing Analytes in Biofluids

Bio-applied molecularly imprinted polymers (MIPs) are biomimetic materials with tailor-made synthetic recognition sites, mimicking biological counterparts known for their sensitive and selective analyte detection. MIPs, specifically designed for biomarker analysis...

Antioxidative and Oxidative Profiles in Plasma and Saliva in Dairy Cows during Pregnancy

Increased metabolism that occurs during pregnancy can result in oxidative stress which is harmful to cells and, consequently, for the proper functioning of the whole organism. Plasma and recently also saliva are important resources for evaluating physiological and pathological conditions in animals. The study aimed to investigate the influence of the metabolic state on the effectiveness of the antioxidant profile of plasma and saliva during the pregnancy of cows. Seventy-six healthy pregnant and twelve non-pregnant control cows were included in the study. Blood and saliva samples were collected each month of the pregnancy course. Examined body fluids were used to evaluate both the total antioxidant capacity (TAC) and the oxidative parameters related to protein and lipid peroxidative processes. TAC, the content of hydroperoxides, and SH groups were determined spectrophotometrically while formylokinurenine and bityrosine contents were measured spectrofluorimetrically. The results showed dynamic changes depending on the period of pregnancy course. The highest antioxidant activity in plasma was mostly noted in early pregnancy and advanced pregnant cows. All tested parameters except SH groups expressed higher values in saliva compared to plasma. Obtained results reveal that the increase in oxidative intensity induced appropriate answers of cells reflected in the increase in antioxidative activity of the organism. Moreover, some examined parameters can indicate the intensity of oxidative stress and therefore could be used in a panel of markers of the physiological course of pregnancy. However, with regards to antioxidant/oxidative parameters, saliva reflects the content of plasma only in part, due to the local metabolism of the salivary gland. Further studies are necessary to establish physiological ranges of antioxidative/oxidative profiles in cows and to define the usefulness of saliva as biological material in oxidative stress diagnostics.

Changes in saliva proteins in cows with mastitis: A proteomic approach

This study aimed to evaluate the possible saliva proteome changes in cows with mastitis using a Tandem Mass Tags (TMT) proteomics approach. For this purpose, the salivary proteomes from healthy cows and cows with mastitis were analysed, and their serum proteomes were also studied for comparative purposes. A total of eight saliva and serum paired samples for each group were used for the proteomic study, and eight additional samples for each group were analysed in the analytical and overlap performance studies. In saliva samples, 2192 proteins were identified, being sixty-three differentially modulated in mastitis. In serum, 1299 proteins were identified, being twenty-nine differentially modulated in mastitis. Gamma glutamyl transferase (γGT) in saliva and serum amyloid A (SAA) were validated by commercially available automated assays. In conclusion, there are changes in protein expression and metabolic pathways in saliva and serum proteomes of cows with mastitis, showing different response patterns but complementary information.

Salivary proteome of aphthous stomatitis reveals the participation of vitamin metabolism, nutrients, and bacteria

There are currently no preventative options for recurrent aphthous stomatitis, and the only available treatments are palliative. This is partly due to a poor understanding of its etiopathogenesis. In this case-control study, we characterized the salivary proteome of patients with recurrent aphthous stomatitis in the presence and absence of lesions. Through mass spectrometry-based proteomics and bioinformatics tools, we identified that the presence of oral ulcers is associated with several specific biological processes, including the metabolic pathways of vitamin B9, B12, nitrogen, selenium, and the bacterium Neisseria meningitidis. These changes occurred only in the presence of clinically visible lesions, and there were no relevant differences between patients in anatomical regions unaffected by ulcers. Additionally, using western blot and ELISA assays, we verified that carbonic anhydrase 1 (CA1) and hemoglobin subunit beta (HBB) proteins are highly expressed during the ulcerative and remission phases of recurrent aphthous stomatitis. Our results cumulatively support saliva as an indicator of the pathophysiological changes, which occur during the clinical course of lesions. From a clinical perspective, we suggest that recurrent aphthous stomatitis is a condition triggered by temporary biological changes in people with lesions.

Changes in Saliva Analytes in Dairy Cows during Peripartum: A Pilot Study

Simple Summary

The use of saliva as a biological fluid to assess welfare and health status is gaining interest nowadays since it can be collected by non-invasive methods without specialized staff. The possibility of measuring analytes in saliva by techniques adapted to automated analyzers is cost-effective, reliable, and replicable. These analytes can provide information useful for the evaluation of welfare and health in dairy cows. In this pilot study, a total of 26 salivary analytes were measured in healthy dairy cows along their peripartum period to assess possible changes and associations with their inflammatory, energy, and milk yield status. Salivary analytes related to stress (cortisol, salivary alpha-amylase, butyrylcholinesterase, and total esterase), immunity (adenosine deaminase), oxidative status (Trolox equivalent antioxidant capacity and the advanced oxidation protein products), and general metabolism (creatine kinase, γ-glutamyl transferase, urea, triglycerides, glucose, and lactate) had significant changes throughout this period. This study indicated that the saliva of dairy cows shows changes in its composition during the transition period and potentially can be a source of biomarkers for monitoring health and welfare.

Abstract

This pilot study aimed to study the possible changes in a profile of 26 salivary analytes in thirteen healthy dairy cows along their peripartum period. Analytes associated with the stress (salivary cortisol, salivary alpha-amylase, butyrylcholinesterase, and total esterase), inflammation (adenosine deaminase), oxidative status (total antioxidant capacity and the advanced oxidation protein products), and general metabolism (creatine kinase, γ-glutamyl transferase, urea, triglycerides, glucose, and lactate) varied along the sampling times. A positive correlation between the white blood cells counts, and the lipase, Trolox equivalent antioxidant capacity, advanced oxidation protein products, and lactate levels in saliva were observed at the delivery. A linear association between selected salivary analytes at different sampling times and the milk yield after calving was observed. In conclusion, in our experimental conditions, it was observed that the peripartum period in dairy cows can induce changes in salivary analytes. Some of them were associated with inflammatory status and the capacity of milk production after calving.

Paper microfluidic device using carbon dots to detect glucose and lactate in saliva samples

Bioanalyses are commonly performed with blood or serum samples. However, these analyses often require invasive and painful blood collection using a needle or finger pricking. Saliva is an alternative and very attractive biological medium for performing clinical analyses, since it contains many types of clinically relevant biomarkers and compounds. Its collection is straightforward and can be achieved in a non-invasive and stress-free way. However, the analytes are frequently present at low concentrations, while the viscosity of whole saliva hinders its analysis using paper devices, especially those with multiple layers (3D-μPADs). This work explores the use of a simple, fast, and low-cost saliva sample pretreatment using a cotton-paper-syringe filtration system, allowing the analysis of saliva samples using multilayer paper devices. The proposed methodology employs the oxidation of glucose and lactate, catalyzed by specific oxidase enzymes, producing hydrogen peroxide. The detection is based on the fluorescence quenching of carbon dots in the presence of hydrogen peroxidase. The concentrations of the analytes showed good linear correlations with the fluorescence quenching, with LODs of 2.60 × 10^-6 and 8.14 × 10^-7 mol L^-1 for glucose and lactate, respectively. The proposed method presented satisfactory intra-day and inter-day repeatabilities, with %RSD values in the range 3.82-6.61%. The enzymatic systems proved to be specific for the analytes and the matrix had no significant influence on the glucose and lactate determinations. The proposed methodology was successfully applied to saliva and serum samples and was validated using certified material.

Salivary Immunoglobulin Gamma-3 Chain C Is a Promising Noninvasive Biomarker for Systemic Lupus Erythematosus

We aimed to characterize the salivary protein components and identify biomarkers in patients with systemic lupus erythematosus (SLE). A proteomic analysis using two-dimensional gel electrophoresis and mass spectrometry was performed to determine the alterations of salivary proteins between patients with SLE and healthy controls, and the concentrations of the candidate proteins were measured through Western blot analysis and the enzyme-linked immunosorbent assay. The 10 differentially expressed protein spots were immunoglobulin gamma-3 chain C region (IGHG3), immunoglobulin alpha-1 chain C region, protein S100A8, lactoferrin, leukemia-associated protein 7, and 8-oxoguanine DNA glycosylase. The patients with SLE exhibited enhanced salivary IGHG3 (3.9 ± 2.15 pg/mL) and lactoferrin (4.7 ± 1.8 pg/mL) levels compared to patients with rheumatoid arthritis (1.8 ± 1.01 pg/mL and 3.2 ± 1.6 pg/mL, respectively; p < 0.001 for both) or healthy controls (2.2 ± 1.64 pg/mL and 2.2 ± 1.7 pg/mL, respectively; p < 0.001 for both). The salivary IGHG3 levels correlated with the erythrocyte sedimentation rate (r = 0.26, p = 0.01), anti-double-stranded DNA (dsDNA) antibody levels (r = 0.25, p = 0.01), and nephritis (r = 0.28, p = 0.01). The proteomic analysis revealed that the salivary IGHG3 levels were associated with SLE and lupus disease activity, suggesting that salivary IGHG3 may be a promising noninvasive biomarker for SLE.

Changes in Saliva Analytes Associated with Lameness in Cows: A Pilot Study

Simple Summary

Saliva may contain useful biomarkers which provide information about animal welfare using convenient and non-invasive sampling methods. In addition, the development of automated techniques of measuring analytes in saliva provides advantages from the technical point of view since they are cost-effective, reliable, and replicable. In this study, 21 salivary analytes measured by automated assays were tested as potential biomarkers of lameness, one of the most prevalent diseases in dairy cows producing significant economic losses. As a result, total esterase (TEA) showed increases in saliva in a group of 11 cows with lameness, decreasing when the lameness was solved after a specific treatment consisting of a hoof trimming and a medical treatment. In addition, TEA activity correlated with the severity of the lameness. Further studies using a larger population of cows with different causes of lameness and severity should be performed to determine the potential of TEA as a biomarker of lameness in cows.

Abstract

The possible changes in a panel of 21 salivary analytes on a population of cows with lameness before and after treating lameness by hoof trimming were analyzed. Then, the analytes that showed significant changes were studied in a larger population of cows with lameness and compared with healthy cows For this purpose, two groups of cows were made by a specialized veterinarian. One consisted of healthy cows with no external signs of diseases and no hematological or biochemical abnormalities, and showing no signs of lameness according to the numerical rating system of severity (NRS, 5-point scale); and the other composed of cows showing only lameness with a NRS of 3.1 ± 0.87 and a lesion scoring system (LSS, 4-point scale) of 3.3 ± 0.89. Both groups did not differ in parity (p = 0.140), days in milk (DIM) (p = 0.780), and body condition score (BCS) (p = 0.074). Initially, 21 biochemical analytes were determined in the saliva of six cows with lameness at the diagnosis time (T0) and twenty days after hoof trimming that successfully solved the lameness (TF). This exploratory study only showed significantly higher values in lipase (Lip) and total esterase (TEA) at T0 compared to TF (p < 0.001 and p = 0.034, respectively). When both analytes were measured in the additional five lame cows and the results of all the animals of the lame group (n = 11) were compared with the healthy group (n = 11), only TEA showed higher activities in the group of lame cows than healthy cows (p = 0.004). TEA was positively correlated with both NRS and LSS (r = 0.43, p = 0.004 and r = 0.35, p = 0.003). In conclusion, this study showed that cows with lameness in our experimental conditions had higher TEA values than healthy cows, and these values decreased after treatment. This is a pilot study, and further studies using a larger population of cows with lameness due to different causes and severity should be performed to determine the potential of TEA as a biomarker of lameness in cows.

Omics Application in Animal Science-A Special Emphasis on Stress Response and Damaging Behaviour in Pigs

Increasing stress resilience of livestock is important for ethical and profitable meat and dairy production. Susceptibility to stress can entail damaging behaviours, a common problem in pig production. Breeding animals with increased stress resilience is difficult for various reasons. First, studies on neuroendocrine and behavioural stress responses in farm animals are scarce, as it is difficult to record adequate phenotypes under field conditions. Second, damaging behaviours and stress susceptibility are complex traits, and their biology is not yet well understood. Dissecting complex traits into biologically better defined, heritable and easily measurable proxy traits and developing biomarkers will facilitate recording these traits in large numbers. High-throughput molecular technologies (“omics”) study the entirety of molecules and their interactions in a single analysis step. They can help to decipher the contributions of different physiological systems and identify candidate molecules that are representative of different physiological pathways. Here, we provide a general overview of different omics approaches and we give examples of how these techniques could be applied to discover biomarkers. We discuss the genetic dissection of the stress response by different omics techniques and we provide examples and outline potential applications of omics tools to understand and prevent outbreaks of damaging behaviours.

Salivary proteome of a Neotropical primate: potential roles in host defense and oral food perception

BACKGROUND

Saliva contains a very complex mixture of proteins for defense against microbiological pathogens and for oral food perception. Howler monkeys are Neotropical primates that can consume a mostly leaf diet. They are well known to thrive in highly disturbed habitats where they may cope with a diversity of dietary challenges and infection risks. We aimed to describe the salivary proteome of howlers to contribute to better understanding of their physiology.

METHODS

We analyzed the salivary proteins of wild black howler monkeys (Alouatta pigra), by SDS-PAGE-1-D and Nano LC-MS/MS and categorized them by their function involved in host defense and oral food perception.

RESULTS

Our proteomic analysis identified 156 proteins in howler saliva including a number of host defense peptides that are the first line of defense in mammals, such as defensin, cathelicidin, dermcidin, and lactotransferrin, and proteins with anti-bacterial, anti-fungal, and anti-viral capacity, such as IgA, IgG, IgM, BPI, salivary heat shock 70 kDa protein, beta-2-microbulin, and protein S-100. We also identified key proteins necessary for taste perception, including salivary carbonic anhydrase VI, cystatin D, IgA, and fatty acid-binding protein. Proteins to detect astringent foods were identifying, including four members of cystatins (A, B, C and D), lactoperoxidase, and histidine-rich proteins. No chitinase and amylase were identified as would be expected because howlers do not eat insects and little starch. These findings provide basic information to future studies in oral biology, ingestive physiology, and physiological ecology of mammals and non-human primates.

Unravelling the Potential of Salivary Volatile Metabolites in Oral Diseases. A Review

Fostered by the advances in the instrumental and analytical fields, in recent years the analysis of volatile organic compounds (VOCs) has emerged as a new frontier in medical diagnostics. VOCs analysis is a non-invasive, rapid and inexpensive strategy with promising potential in clinical diagnostic procedures. Since cellular metabolism is altered by diseases, the resulting metabolic effects on VOCs may serve as biomarkers for any given pathophysiologic condition. Human VOCs are released from biomatrices such as saliva, urine, skin emanations and exhaled breath and are derived from many metabolic pathways. In this review, the potential of VOCs present in saliva will be explored as a monitoring tool for several oral diseases, including gingivitis and periodontal disease, dental caries, and oral cancer. Moreover, the analytical state-of-the-art for salivary volatomics, e.g., the most common extraction techniques along with the current challenges and future perspectives will be addressed unequivocally.

Combinations of non-invasive indicators to detect dairy cows submitted to high-starch-diet challenge

High-starch diets (HSDs) fed to high-producing ruminants are often responsible for rumen dysfunction and could impair animal health and production. Feeding HSDs are often characterized by transient rumen pH depression, accurate monitoring of which requires costly or invasive methods. Numerous clinical signs can be followed to monitor such diet changes but no specific indicator is able to make a statement at animal level on-farm. The aim of this pilot study was to assess a combination of non-invasive indicators in dairy cows able to monitor a HSD in experimental conditions. A longitudinal study was conducted in 11 primiparous dairy cows fed with two different diets during three successive periods: a 4-week control period (P1) with a low-starch diet (LSD; 13% starch), a 4-week period with an HSD (P2, 35% starch) and a 3-week recovery period (P3) again with the LSD. Animal behaviour was monitored throughout the experiment, and faeces, urine, saliva, milk and blood were sampled simultaneously in each animal at least once a week for analysis. A total of 136 variables were screened by successive statistical approaches including: partial least squares-discriminant analysis, multivariate analysis and mixed-effect models. Finally, 16 indicators were selected as the most representative of a HSD challenge. A generalized linear mixed model analysis was applied to highlight parsimonious combinations of indicators able to identify animals under our experimental conditions. Eighteen models were established and the combination of milk urea nitrogen, blood bicarbonate and feed intake was the best to detect the different periods of the challenge with both 100% of specificity and sensitivity. Other indicators such as the number of drinking acts, fat:protein ratio in milk, urine, and faecal pH, were the most frequently used in the proposed models. Finally, the established models highlight the necessity for animals to have more than 1 week of recovery diet to return to their initial control state after a HSD challenge. This pilot study demonstrates the interest of using combinations of non-invasive indicators to monitor feed changes from a LSD to a HSD to dairy cows in order to improve prevention of rumen dysfunction on-farm. However, the adjustment and robustness of the proposed combinations of indicators need to be challenged using a greater number of animals as well as different acidogenic conditions before being applied on-farm.

Effect of food contamination and collection material in the measurement of biomarkers in saliva of horses

This study aims to evaluate the effect of the presence of food and the material used in a panel of biomarkers in saliva of horses. For the food effect study, clean saliva was incubated with a known amount of food consisting of oats, hay or grass. Significant changes were observed when saliva was incubated with oats for total protein (P = .050) and phosphorus (P = .008), with grass for total protein (P = .037), salivary alpha-amylase (sAA, P = .018), total esterase (TEA, P = .018), butyrilcholinesterase (BChE, P = .037), adenosine deaminase (ADA, P = .037), and total bilirubin (P = .018), and with hay for sAA (P = .018), phosphorus (P = .037), γ-glutamyl transferase (gGT, P = .004), and creatine kinase (CK, P = .016). For the material-based collection study, saliva using a sponge and a cotton role at the same time were collected and compared. Lower values were obtained in clean saliva collected with cotton role compared to sponge for sAA (P = .030), TEA (P = .034), BChE (P = .003), gGT (P = .002) and cortisol (P < .001) In conclusion, the presence of food and the material used for its collection, can influence the results obtained when analytes are measured in saliva of horses.

Changes in saliva proteins in two conditions of compromised welfare in pigs: An experimental induced stress by nose snaring and lameness

The aim of this study was to identify biological pathways and proteins differentially expressed in saliva of pigs in two conditions of compromised welfare: an acute stress consisting of restraint with a nose snare and in pigs with lameness which is a highly frequent problem in the swine industry. For this purpose, high-resolution quantitative proteomics based on Tandem Mass Tags labelling was used. Four proteins showed significant differences in the conditions of compromised welfare, namely cornulin, the heat shock protein 27 and lactate dehydrogenase (LDH), that showed significant increases, whereas immunoglobulin J chain showed a significant decrease. LDH, which was the protein that showed the highest differences, was selected for validation and clinical evaluation as a diagnostic biomarker. Significant changes in this protein were observed between pigs restrained with a nose snare and pigs with lameness compared with healthy pigs when measured with available commercial assays in a larger population of pigs. In conclusion, this study reports that in situations of compromised welfare on farm, such as acute stress and lameness in pigs, there are changes in proteins and metabolic pathways in saliva, and describes a series of proteins that could potentially be used as biomarkers for both short term acute stress and longer term chronic stress of lameness. These biomarkers would have the advantage of being measured in saliva by a noninvasive and not stressful collection sampling procedure.

Acute phase proteins, saliva and education in laboratory science: an update and some reflections

This manuscript provides updated knowledge and some ideas and reflections about three areas which are currently of interest in the field of the animal laboratory science. These areas are the study of acute phase proteins (APPs) as biomarkers of inflammation, the use of saliva as a non-invasive sample for analyte measurements, and the development of education in the field of laboratory medicine. In the APPs, a seven-point plan for their interpretation in all veterinary species containing updated knowledge and future perspectives is described. Regarding the saliva, general concepts, examples of practical applications and the limitations and points to improve for the use of this fluid are explained. Finally, the recent evolution, current situation and possible ideas for future development of education in this field are commented. In addition to review the knowledge in these three specific areas, this report can help to provide a wide vision of the potential and future perspectives in veterinary laboratory science.

Changes in saliva analytes in equine acute abdominal disease: a sialochemistry approach

BACKGROUND

The biochemical components of saliva can change in certain pathologies in horses, for example in acute abdominal disease. The aim of this study was (1) to evaluate if a panel of biochemical analytes usually used in serum can be measured in saliva of horses and (2) to study the possible changes of these biochemical analytes in saliva of horses affected by acute abdominal disease. A panel of 23 analytes was analytically validated in saliva of horses and possible changes in these analytes in a pilot study with six healthy horses and six horses with acute abdominal disease were evaluated. The analytes with significant changes were then evaluated in a larger population of 20 healthy and 37 diseased horses.

RESULTS

Seven analytes showed significant increases in the pilot study which were confirmed in the larger population. The analytes which showed significant changes, and their median fold increase and significance shown in the larger population were salivary γ-glutamyl transferase (gGT, 2.3 fold, P = 0.001), creatine kinase (CK, 6.2 fold, P < 0.001), urea (2.3 fold, P = 0.001), total bilirubin (2.6 fold, P < 0.001), total proteins (3.2 fold, P < 0.001), phosphorus (P, 4.5 fold, P < 0.001) and alpha-amylase (sAA, 8.5 fold, P < 0.001). Total proteins, P and sAA showed sensitivities higher than 70% at their optimal cut-off points and a specificity of 100% in differentiating between healthy horses and those with acute abdominal disease.

CONCLUSIONS

A panel of 23 biochemical analytes can be measured in saliva of horses, where gGT, CK, urea, total bilirubin, total protein, P and sAA levels are raised in horses with acute abdominal disease.

Biomarkers of oxidative stress in saliva in pigs: analytical validation and changes in lactation

Background

Biomarkers of oxidative stress in pigs have been measured in serum/plasma samples. However, blood collection in pigs can be highly stressful to the animals. Saliva is a biological fluid with several advantages in pigs over blood, since it can be easily collected without stress to the animals, being therefore an ideal sample in this species. The objective of this study was the validation of assays for the evaluation of oxidative stress status in saliva of pigs. For this purpose, three assays commonly used to evaluate the total antioxidant capacity (TAC): trolox equivalent antioxidant capacity (TEAC), cupric reducing antioxidant capacity (CUPRAC), and ferric reducing ability of plasma (FRAP)), one individual antioxidant (uric acid) and two assays to evaluate oxidant concentrations (advanced oxidation protein products (AOPP) and hydrogen peroxide (H₂O₂)) were measured and validated in porcine saliva. In addition, the possible changes of these assays in sows’ saliva during lactation were be studied.

Results

The methods had intra- and inter-assays coefficient of variation lower than 15%. They also showed an adequate linearity and recovery, and their detection limits were low enough to detect the analytes in saliva of pigs. Overall the analytical validation tests showed that the assays used in our study are valid and reliable for the evaluation of oxidative stress in porcine saliva. In addition, it was observed that these salivary biomarkers can change in a situation of oxidative stress such as lactation in sows.

Conclusions

All assays for salivary biomarkers of oxidative stress evaluated in this study have demonstrated a high analytical accuracy and low imprecision. In addition, it has been observed that these biomarkers showed significant changes in a situation of oxidative stress such as lactation in sows. Therefore, this study opens a new possibility of using saliva as a non-invasive sample to evaluate oxidative stress in pigs.

Biochemical changes in saliva of cows with inflammation: A pilot study

Saliva contains a variety of compounds that can change in local and systemic pathologies including inflammation. Although changes in acute phase proteins and markers of oxidative stress in saliva during inflammation in humans and different animal species have been described, no data exist about possible changes during inflammation in analytes in saliva of cows. The aim of the present study was to evaluate changes in selected salivary biomarkers of stress, inflammation and immune system, and oxidative stress in cows with inflammation. For this purpose, bovine mastitis was used as model. Saliva and serum from 18 clinically healthy cows and 18 cows with clinical mastitis were used in the study. A panel of analytes integrated by alpha-amylase, cortisol, haptoglobin, adenosine deaminase, cholinesterase, total antioxidant capacity, lactate, and uric acid was measured in all samples and differences between the two groups of animals were evaluated. Significant increases in cortisol, alpha-amylase, uric acid, lactate and significant decreases in cholinesterase were detected in saliva of cows with mastitis. These results indicate that that cows with mastitis show changes in salivary biomarkers that reflect presence of stress, inflammation and oxidative stress in the animals.

Salivary Exosomes as Nanocarriers for Cancer Biomarker Delivery

Human saliva is an ideal body fluid for developing non-invasive diagnostics. Saliva contains naturally-occurring nanoparticles with unique structural and biochemical characteristics. The salivary exosome, a nanoscale extracellular vesicle, has been identified as a highly informative nanovesicle with clinically-relevant information. Salivary exosomes have brought forth a pathway and mechanism by which cancer-derived biomarkers can be shuttled through the systemic circulation into the oral cavity. Despite such clinical potential, routine and reliable analyses of exosomes remain challenging due to their small sizes. Characterization of individual exosome nanostructures provides critical data for understanding their pathophysiological condition and diagnostic potential. In this review, we summarize a current array of discovered salivary biomarkers and nanostructural properties of salivary exosomes associated with specific cancers. In addition, we describe a novel electrochemical sensing technology, EFIRM (electric field-induced release and measurement), that advances saliva liquid biopsy, covering the current landscape of point-of-care saliva testing.

Salivary Biomarkers in Systemic Sclerosis Disease

Scleroderma or systemic sclerosis (SSc) is frequently detected at an advanced stage due to diagnosis difficulties. Salivary biomarkers, if existing, could be used for predictive diagnosis of this disease. Human saliva contains a large number of proteins that can be used for diagnosis and are of great potential in clinical research. The use of proteomic analysis to characterize whole saliva (WS) in SSc has gained an increasing attention in the last years and the identification of salivary proteins specific for SSc could lead to early diagnosis or new therapeutic targets. This review will present an overview about the use of WS in SSc studies. The proteomic technologies currently used for global identification of salivary proteins in SSc, as well as the advantages and limitations for the use of WS as a diagnostic tool, will be presented.

Influence of different sample preparation strategies on the proteomic identification of stress biomarkers in porcine saliva

Background

The influence of two different sample treatments comprising the enrichment of glycoproteins by boronic acid and dynamic range compression by hexapeptide libraries, on the detection of stress markers in saliva of pigs was evaluated in this study. For this purpose, saliva samples collected before and after the application of an acute stress model consisting of nasal restraining in pigs were processed without any treatment and with the two different treatments mentioned above. Protein separation by two-dimensional gel electrophoresis (2-DE) followed by identification of proteins using MALDI-TOF/TOF mass spectrometry (MS) was used as proteomic technique.

Results

The application of each of the two different sample treatment protocols allowed the identification of unique proteins that could be potential salivary acute stress markers in pigs: lipocalin 1, protein S100-A8 and immunoglobulin M by enrichment of glycoproteins; protein S100-A9, double headed protease inhibitor submandibular gland, and haemoglobin by dynamic range compression; and protein S100-A12 by both protocols. Salivary lipocalin, prolactin inducible protein, light chain of immunoglobulins, adenosine deaminase and carbonic anhydrase VI were identified as potential markers in untreated saliva as well as one of the other treatments.

Conclusion

The use of different procedures allowed the detection of different potential stress markers. Although from a practical point of view, the use of saliva without further treatment as well as the enrichment of glycoproteins are less expensive and easy to do procedures.

A Lab-on-a-Chip-Based Non-Invasive Optical Sensor for Measuring Glucose in Saliva

A lab-on-a-chip (LOC)-based non-invasive optical sensor for measuring glucose in saliva was fabricated. Existing glucose sensors utilizing blood require acquisition of a blood sample by pricking the finger, which is painful and inconvenient. To overcome these limitations, we propose a non-invasive glucose sensor with LOC, micro-electro-mechanical system and optical measurement technology. The proposed sensor for measuring glucose in saliva involves pretreatment, mixing, and measurement on a single tiny chip. Saliva containing glucose and glucose oxidase for glucose oxidation are injected through Inlets 1 and 2, respectively. Next, H₂O₂ is produced by the reaction between glucose and glucose oxidase in the pretreatment part. The saliva and generated H₂O₂ are mixed with a colorizing agent injected through Inlet 3 during the mixing part and the absorbance of the colorized mixture is measured in the measurement part. The absorbance of light increases as a function of glucose concentration at a wavelength of 630 nm. To measure the absorbance of the colorized saliva, a light-emitting diode with a wavelength of 630 nm and a photodiode were used during the measurement part. As a result, the measured output current of the photodiode decreased as glucose concentration in the saliva increased.

Saliva-Exosomics in Cancer: Molecular Characterization of Cancer-Derived Exosomes in Saliva

Exosomes are small membrane vesicles of endocytic origin that are secreted by most cells and detected in saliva. Pathophysiological roles for salivary exosomes are beginning to be recognized in diseases including cancer, highlighting potential biomarkers and biological functions. Since early detection of cancer is vital for successful treatment, salivary exosomes would be advantageous in achieving a better survival rate due to their ready availability and noninvasiveness. The use of salivary exosomes may therefore be promising in the accurate detection of premalignant lesions and early-stage cancers, also for better our understanding of the molecular basis of tumorigenesis. In this chapter, we review our current knowledge of salivaomics, focusing on nucleic acids and proteins in saliva as potential cancer biomarkers. Since salivaomics is a rapidly evolving field, we hope to expand frameworks toward salivary exosomes, integrate new and existing information, and bridge salivaomics with other biomedical researches. Furthermore, we would like to coin the term "saliva-exosomics" as the next-generation salivaomics. Our goal in this chapter is to provide the most updated information on cancer-derived exosomes in the saliva as natural carriers of biomarkers and signaling molecules. Major advances include definitive structure analysis and molecular characterization of salivary exosomes. We also highlight the exosome biogenesis and cargo trafficking mechanisms in which recent animal studies have expanded our understanding of exosome-mediated transfer of cancer-derived products from distal tumor to salivary gland. The potential roles of the salivary exosomes in cancer progression and immune surveillance are also addressed.

Quantitative proteomic analysis of the fall armyworm saliva

Lepidopteran larvae secrete saliva on plant tissues during feeding. Components in the saliva may aid in food digestion, whereas other components are recognized by plants as cues to elicit defense responses. Despite the ecological and economical importance of these plant-feeding insects, knowledge of their saliva composition is limited to a few species. In this study, we identified the salivary proteins of larvae of the fall armyworm (FAW), Spodoptera frugiperda; determined qualitative and quantitative differences in the salivary proteome of the two host races-corn and rice strains-of this insect; and identified changes in total protein concentration and relative protein abundance in the saliva of FAW larvae associated with different host plants. Quantitative proteomic analyses were performed using labeling with isobaric tags for relative and absolute quantification followed by liquid chromatography-tandem mass spectrometry. In total, 98 proteins were identified (>99% confidence) in the FAW saliva. These proteins were further categorized into five functional groups: proteins potentially involved in (1) plant defense regulation, (2) herbivore offense, (3) insect immunity, (4) detoxification, (5) digestion, and (6) other functions. Moreover, there were differences in the salivary proteome between the FAW strains that were identified by label-free proteomic analyses. Thirteen differentially identified proteins were present in each strain. There were also differences in the relative abundance of eleven salivary proteins between the two FAW host strains as well as differences within each strain associated with different diets. The total salivary protein concentration was also different for the two strains reared on different host plants. Based on these results, we conclude that the FAW saliva contains a complex mixture of proteins involved in different functions that are specific for each strain and its composition can change plastically in response to diet type.

Detection of 70 kDa heat shock protein in the saliva of dairy cows

This Research Communication describes, for the first time, the detection of HSP70 in saliva of dairy cows. Thermal stress is a major environmental stress that limits animal growth, metabolism, and productivity. The cellular response to heat stress involves the synthesis of heat shock proteins (HSPs), presumably to protect the functional stability of cells at increasing temperatures. HSP70 has been found to be present in cattle blood serum and may also be present in other secretory fluids, such as saliva, as already observed in humans. The aim of this study was to detect heat shock protein HSP70 in bovine saliva. Saliva samples were taken from higher- (n = 5) and lower milk producing (n = 5) Holstein-Friesian cows in summer and in winter for the detection of HSP70. HSP70 concentrations were assayed using the ELISA technique. Salivary HSP70 concentrations ranged from 0·524 to 12·174 ng/ml in cows. Higher salivary HSP70 concentrations were significantly associated with higher milk production and higher environmental temperature, but not with rectal temperature.