Emerging salivary biomarkers by mass spectrometry

Mass Spectrometry-Based Proteomics for Discovering Salivary Biomarkers in Periodontitis: A Systematic Review

Periodontitis is one of the primary causes of tooth loss, and is also related to various systemic diseases. Early detection of this condition is crucial when it comes to preventing further oral damage and the associated health complications. This study offers a systematic review of the literature published up to April 2023, and aims to clearly explain the role of proteomics in identifying salivary biomarkers for periodontitis. Comprehensive searches were conducted on PubMed and Web of Science to shortlist pertinent studies. The inclusion criterion was those that reported on mass spectrometry-driven proteomic analyses of saliva samples from periodontitis cohorts, while those on gingivitis or other oral diseases were excluded. An assessment for risk of bias was carried out using the Newcastle-Ottawa Scale and Quality Assessment of Diagnostic Accuracy Studies or the NIH quality assessment tool, and a meta-analysis was performed for replicable candidate biomarkers, i.e., consistently reported candidate biomarkers (in specific saliva samples, and periodontitis subgroups, reported in ≥2 independent cohorts/reports) were identified. A Gene Ontology enrichment analysis was conducted using the Database for Annotation, Visualization, and Integrated Discovery bioinformatics resources, which consistently expressed candidate biomarkers, to explore the predominant pathway wherein salivary biomarkers consistently manifested. Of the 15 studies included, 13 were case-control studies targeting diagnostic biomarkers for periodontitis participants (periodontally healthy/diseased, n = 342/432), while two focused on biomarkers responsive to periodontal treatment (n = 26 participants). The case-control studies were considered to have a low risk of bias, while the periodontitis treatment studies were deemed fair. Summary estimate and confidence/credible interval, etc. determination for the identified putative salivary biomarkers could not be ascertained due to the low number of studies in each case. The results from the included case-control studies identified nine consistently expressed candidate biomarkers (from nine studies with 230/297 periodontally healthy/diseased participants): (i) those that were upregulated: alpha-amylase, serum albumin, complement C3, neutrophil defensin, profilin-1, and S100-P; and (ii) those that were downregulated: carbonic anhydrase 6, immunoglobulin J chain, and lactoferrin. All putative biomarkers exhibited consistent regulation patterns. The implications of the current putative marker proteins identified were reviewed, with a focus on their potential roles in periodontitis diagnosis and pathogenesis, and as putative therapeutic targets. Although in its early stages, mass spectrometry-based salivary periodontal disease biomarker proteomics detection appeared promising. More mass spectrometry-based proteomics studies, with or without the aid of already available clinical biochemical approaches, are warranted to aid the discovery, identification, and validation of periodontal health/disease indicator molecule(s). Protocol registration number: CRD42023447722; supported by RD-02-202410 and GRF17119917.

Applications of Mass Spectrometry in Dentistry

Mass Spectrometry (MS) is one of the fastest-developing methods in analytical instrumentation. As a highly sensitive, universal detector, it can identify known and unknown compounds, which can indeed be found in a minimal concentration. This review aims to highlight the significant milestones in MS applications in dentistry during recent decades. MS can be applied in three different fields of dentistry: (1) in research of dental materials and chemical agents, (2) in laboratory analysis of biospecimens, and (3) as a real-time diagnostic tool in service of oral surgery and pathology. MS applications on materials and agents may focus on numerous aspects, such as their clinical behavior, possible toxicity, or antimicrobial properties. MS is also a valuable, non-invasive tool for biomarkers' detection in saliva and has found great application in -omics technologies as it achieves efficient structure-finding in metabolites. As metabolites are located beyond the central dogma, this technique can provide a complete understanding of cellular functions. Thus, it is possible to determine the biological profile in normal and pathological conditions, detect various oral or systematic diseases and conditions, and predict their course. Lastly, some promising advances concerning the surgical approach to potentially oral malignant or malignant disorders exist. This breakthrough method provides a comprehensive approach to dental materials research and biomarker discovery in dental and craniofacial tissues. The current availability of various 'OMIC' approaches paves the way for individualized dentistry and provides suggestions for clinical applications in the point-of-care hubs.

Analysis of Human and Microbial Salivary Proteomes in Children Offers Insights on the Molecular Pathogenesis of Molar-Incisor Hypomineralization

Molar incisor hypomineralization is a complex developmental enamel defect that affects the permanent dentition of children with significant functional and aesthetic implications. Saliva is an ideal diagnostic tool and ensures patients’ compliance by diminishing the discomfort especially in pediatric population. Lately, salivary proteome analysis has progressively evolved in various biomedical disciplines. As changes in saliva composition are associated with oral diseases, it is reasonable to assume that the saliva proteome of MIH-affected children might be altered compared to healthy children. This study analyzed the human and microbial salivary proteome in children with MIH in order to identify salivary markers indicative of the pathology. The conducted proteomic analysis generated a comprehensive dataset comprising a total of 1515 high confidence identifications and revealed a clear discrimination between the two groups. Statistical comparison identified 142 differentially expressed proteins, while the pathway analysis indicated deregulation of inflammation, immune response mechanisms, and defense response to bacteria in MIH patients. Bacterial proteome analysis showed a lower diversity for the microbial species, which highlights the dysbiotic environment established in the MIH pathology.

Stability of drugs of abuse in synthetic oral fluid investigated using a simple "dilute and inject" method of analysis

Human oral fluid is well established as a matrix for drug screening, particularly in the workplace. The need to synthesise synthetic oral fluid (SOF) has been recognised in order to overcome human oral fluid's composition variability. We have used SOF spiked with six common drugs of abuse or their primary metabolites: morphine, amfetamine, benzoylecgonine, cocaine, diazepam, and (−)‐Δ⁹‐tetrahydrocannabinol (THC) in order to assess the suitability of this matrix for quality assurance purposes. For confirmation of a drug screening test, controls and spiked standards are normally required. All our analytes were detected by LC–MS/MS using a quick and easy “dilute and inject” sample preparation approach as opposed to relatively slower solid‐phase extraction. The limit of detection (LOD) was 10 ng/ml for diazepam and THC and 5 ng/ml for morphine, amfetamine, benzoylecgonine and cocaine. Validation results showed good accuracy as well as inter‐ and intra‐assay precision (CV [%] < 5). Our work highlighted the importance of adding Tween® 20 to the SOF and calibrants to reduce losses when handling THC. Furthermore, drug stability was tested at various temperatures (5°C, 20°C and 40°C), for a number of days or after freeze–thaw cycles. Recommendations regarding storage are provided, the spiked SOF being stable at 5°C for up to 1 week without significant drug concentration loss.

Developing a Biosensor-Based Immunoassay to Detect HPV E6 Oncoprotein in the Saliva Rinse Fluid of Oral Cancer Patients

Transmission of Human papillomavirus (HPVs) is faithfully associated with carcinogenesis of oral cavity and oropharyngeal cancers. Therefore, clinical researchers may need to generate customized antibodies for the upcoming ELISA-based analysis to discover rare but valuable biomarkers. The aim of study was to develop and generate a biosensor-based immunoassay for early screening HPV-related oral cancer via saliva rinse fluid analysis. A peptide fragment of high-risk HPV subtype 16/18 protein, E6 protein (HP-1 protein sequence 48–66), was designed and synthesized, followed by the generation of polyclonal antibodies (anti-HP1 IgY) in our university-based laboratories. The titer and specificity of antibodies were determined by enzyme-linked immunosorbent assay (ELISA), and the Surface Plasmon Resonance (SPR) biosensor-based method was developed. Kinetic analyses by SPR confirmed that this designed peptide showed a high affinity with its generated polyclonal antibodies. Saliva fluid samples of thirty oral cancer patients and 13 healthy subjects were analyzed. SPR indicated that 26.8% of oral cancer patients had higher resonance unit (ΔRU) values than normal subjects. In conclusion, we developed a biosensor-based immunoassay to detect HPV E6 oncoprotein in the saliva rinse fluid for early screening and discrimination of HPV-related oral cancer patients.

Potential protein markers in children with Autistic Spectrum Disorder (ASD) revealed by salivary proteomics

The lack of specific pharmacological therapy for Autistic Spectrum Disorder (ASD) and its clinical heterogeneity demand efforts directed toward the identification of biomarkers to aid in diagnosis. Proteomics offers a new perspective for studying the altered proteins associated with autism spectrum disorders (ASD) and we have saliva as an easy-to-collect biological fluid with important biomolecules for investigating biomarkers in various diseases. In this sense, saliva could be used to identify potential biomarkers of ASD. In the current work, saliva samples were collected from children with different degrees of ASD and healthy children and proteomics approaches were applied to generate data on differentially expressed proteins between groups which will serve as a basis for future validation studies as protein markers. Data are available via ProteomeXchange with identifier PXD030065. As results, 132 proteins were present in 80% of the saliva pools of all analyzed groups. Twenty-five proteins were identified as overexpressed in the group of severe and mild/moderate ASD carriers, among which, eight were identified as potential biomarkers for ASD.

Salivary ZG16B expression loss follows exocrine gland dysfunction related to oral chronic graft-versus-host disease

Chronic graft-versus-host disease (cGVHD) targets include the oral mucosa and salivary glands after allogeneic hematopoietic stem cell transplant (HSCT). Without incisional biopsy, no diagnostic test exists to confirm oral cGVHD. Consequently, therapy is often withheld until severe manifestations develop. This proteomic study examined saliva and human salivary gland for a biomarker profile at first onset of oral cGVHD prior to initiation of topical steroid therapy. Whole saliva collected at onset of biopsy-proven oral GVHD was assessed using liquid chromatography-coupled tandem mass spectrometry with identification of 569 proteins, of which 77 significantly changed in abundance. ZG16B, a secretory lectin protein, was reduced 2-fold in oral cGVHD saliva (p <0.05), and significantly decreased in salivary gland secretory cells affected by cGVHD. Single-cell RNA-seq analysis of healthy MSG localized ZG16B expression to two discrete acinar cell populations. Reduced ZG16B expression may indicate specific cGVHD activity and possibly general salivary gland dysfunction.

Childhood Allergy Disease, Early Diagnosis, and the Potential of Salivary Protein Biomarkers

Allergic disease has risen to epidemic proportions since the last decade and is among the most common noncommunicable, chronic diseases in children and adolescents worldwide. Allergic disease usually occurs in early life; thus, early biomarkers of allergic susceptibility are required for preventive measures to high-risk infants which enable early interventions to decrease allergic severity. However, to date, there is no reliable general or specific allergy phenotype detection method that is easy and noninvasive for children. Most reported allergic phenotype detection methods are invasive, such as the skin prick test (SPT), oral food challenge (OFC), and blood test, and many involve not readily accessible biological samples, such as cord blood (CB), maternal blood, or newborn vernix. Saliva is a biological sample that has great potential as a biomarker measurement as it consists of an abundance of biomarkers, such as genetic material and proteins. It is easily accessible, noninvasive, collected via a painless procedure, and an easy bedside screening for real-time measurement of the ongoing human physiological system. All these advantages emphasise saliva as a very promising diagnostic candidate for the detection and monitoring of disease biomarkers, especially in children. Furthermore, protein biomarkers have the advantages as modifiable influencing factors rather than genetic and epigenetic factors that are mostly nonmodifiable factors for allergic disease susceptibility in childhood. Saliva has great potential to replace serum as a biological fluid biomarker in diagnosing clinical allergy. However, to date, saliva is not considered as an established medically acceptable biomarker. This review considers whether the saliva could be suitable biological samples for early detection of allergic risk. Such tools may be used as justification for targeted interventions in early childhood for disease prevention and assisting in reducing morbidity and mortality caused by childhood allergy.

The potential of salivary biomarkers of nutritional status and dietary intake: A Systematic Review

OBJECTIVES

To explore whether nutritional salivary biomarkers could be used to aid nutritional status assessment and/or support traditional dietary assessment methods for patients.

DATA AND SOURCES

Searches were performed using four electronic databases; MEDLINE, EMBASE, Scopus and Web of Science. Trial registers (i.e. Cochrane), grey literature and reference lists were searched.

STUDY SELECTION

Studies which measured nutritional salivary biomarkers related to nutritional status and/or dietary intake outcome were included. No restrictions on participants' age, study design, publication date, setting or health status. Animal studies, non-English language studies, commentaries, and conference abstracts were excluded.

RESULTS

Study titles and abstracts were screened (n = 7982), full-texts assessed (n = 176) and 85 studies were included in a narrative synthesis. The most promising salivary biomarkers for nutritional status included: glucose, where saliva and serum levels were positively correlated in those with type 2 diabetes (T2D), higher salivary calcium levels in post-menopausal women in general and specifically those with lower bone mineral density (BMD), and salivary vitamin D to assess vitamin D status in healthy volunteers. Higher salivary total antioxidant capacity (TAC), nitrate/nitrite and fluoride were observed with increased antioxidant, nitrate/nitrite and fluoride dietary intake, respectively. A meta-analysis found significantly higher mean salivary glucose (n = 12) in T2D compared with healthy controls, but there was substantial heterogeneity (I²=94%) and evidence of publication bias.

CONCLUSIONS

The most promising salivary biomarkers identified in this systematic review were, glucose, vitamin D, calcium, TAC, nitrate/nitrite and fluoride. However, this was based on a small number of studies of varying quality, with many lacking a salivary assay performance assessment.

CLINICAL SIGNIFICANCE

At present, nutritional salivary biomarkers cannot be used alone to assess nutritional status or dietary intake. Further research into the most promising nutritional salivary biomarkers is required.

Evaluation of multiple hydrophilic interaction chromatography columns and surrogate matrix for arginine quantification in saliva by high-resolution mass spectrometry

Arginine, a pivotal ingredient in many biochemical synthetic pathways, can be used as a biomarker for many oral care clinical applications. It is still a challenge to develop a sensitive and reliable chromatographic method to quantify arginine as a biomarker in saliva, with or without arginine product pretreatment. The current method solved two critical issues for arginine quantitation in human saliva. The first issue was how to optimize arginine peak shape. A hydrophilic interaction chromatography method based on the column selection, pH and pK_a relationship, mobile phase ionic strength, organic solvent consideration, and temperature effects was developed. An optimized chromatographic condition for arginine quantitation in the saliva matrix was obtained. The second issue was how to build confidence in the use of a simple surrogate matrix methodology to replace the more complex traditional standard addition methodology. The surrogate matrix methodology we developed is applicable to the measurement of arginine as a potential non-invasive biomarker in human saliva. The method detection and quantification limit reached 2 and 6 ng/mL. The tailing factor was within the 0.9-1.1 range even though arginine had three pK_a values at 2.18, 9.09, and 13.2.

Saliva, a bodily fluid with recognized and potential diagnostic applications

Human whole saliva is a bodily fluid that can be obtained easily by noninvasive techniques. Specimens can be collected by the patient also at home in order to monitor health status and variations of several analytes of clinical interest. The contributions to whole saliva include secretions from salivary glands and, among others, from the gingival crevicular fluid that derives from the epithelial mucosa. Therefore, saliva is currently a relevant diagnostic fluid for many substances, including steroids, nonpeptide hormones, therapeutic drugs, and drugs of abuse. This review at first briefly describes the different contributions to whole saliva. A section illustrates the procedures for the collection, handling, and storage of salivary specimens. Another section describes the present use of whole saliva for diagnostic purposes and its specific utilization for the diagnosis of several local and systemic diseases. The final sections illustrate the future opportunities offered by various not conventional techniques with a focus on the most recent –omic investigations. It describes the various issues that have to be taken into account to avoid false positives and negatives, such as the strength of the experimental plan, the adequacy of the number of samples under study, and the proper choice of controls.

Emerging intraoral biosensors

Biomedical devices that involved continuous and real-time health-care monitoring have drawn much attention in modern medicine, of which skin electronics and implantable devices are widely investigated. Skin electronics are characterized for their non-invasive access to the physiological signals, and implantable devices are superior at the diagnosis and therapy integration. Despite the significant progress achieved, many gaps remain to be explored to provide a more comprehensive overview of human health. As the connecting point of the outer environment and human systems, the oral cavity contains many unique biomarkers that are absent in skin or inner organs, and hence, this could become a promising alternative locus for designing health-care monitoring devices. In this review, we outline the status of the oral cavity during the communication of the environment and human systems and compare the intraoral devices with skin electronics and implantable devices from the biophysical and biochemical aspects. We further summarize the established diagnosis database and technologies that could be adopted to design intraoral biosensors. Finally, the challenges and potential opportunities for intraoral biosensors are discussed. Intraoral biosensors could become an important complement for existing biomedical devices to constitute a more reliable health-care monitoring system.

Top-Down Proteomics of Human Saliva Discloses Significant Variations of the Protein Profile in Patients with Mastocytosis

Mastocytosis is a myeloproliferative neoplasm causing abnormal clonal mast cell accumulation in different tissues, such as skin and bone marrow. A cutaneous subtype (CM) is distinguished from a systemic one (SM); SM patients can be grouped into SM with (SM+C) or without (SM-C) additional cutaneous lesions, and their classification is often challenging. This study was purposed to highlight variations in the salivary proteome of patients with different mastocytosis subtypes and compared to healthy controls. A top-down proteomics approach coupled to a label-free quantitation revealed salivary profiles in patients different from those of controls and a down-regulation of peptides/proteins involved in the mouth homeostasis and defense, such as statherin, histatins, and acidic proline-rich proteins (aPRPs), and in innate immunity and inflammation, such as the cathepsin inhibitors, suggesting a systemic condition associated with an exacerbated inflammatory state. The up-regulation of antileukoproteinase and S100A8 suggested a protective role against the disease status. The two SM forms were distinguished by the lower levels of truncated forms of aPRPs, statherin, P-B peptide, and cystatin D and the higher levels of thymosin β4 and α-defensins 1 and 4 in SM-C patients with respect to SM+C. Data are available via ProteomeXchange with identifier PXD017759.

Top-Down Proteomics of Human Saliva Discloses Significant Variations of the Protein Profile in Patients with Mastocytosis

Mastocytosis is a myeloproliferative neoplasm causing abnormal clonal mast cell accumulation in different tissues, such as skin and bone marrow. A cutaneous subtype (CM) is distinguished from a systemic one (SM); SM patients can be grouped into SM with (SM+C) or without (SM-C) additional cutaneous lesions, and their classification is often challenging. This study was purposed to highlight variations in the salivary proteome of patients with different mastocytosis subtypes and compared to healthy controls. A top-down proteomics approach coupled to a label-free quantitation revealed salivary profiles in patients different from those of controls and a down-regulation of peptides/proteins involved in the mouth homeostasis and defense, such as statherin, histatins, and acidic proline-rich proteins (aPRPs), and in innate immunity and inflammation, such as the cathepsin inhibitors, suggesting a systemic condition associated with an exacerbated inflammatory state. The up-regulation of antileukoproteinase and S100A8 suggested a protective role against the disease status. The two SM forms were distinguished by the lower levels of truncated forms of aPRPs, statherin, P-B peptide, and cystatin D and the higher levels of thymosin β4 and α-defensins 1 and 4 in SM-C patients with respect to SM+C. Data are available via ProteomeXchange with identifier PXD017759.

Saliva as a diagnostic tool for dental caries, periodontal disease and cancer: is there a need for more biomarkers?

Introduction: A biomarker is a biological indicator of normal or pathogenic processes. Identification of biomarkers is useful for the prevention, diagnosis and prognosis of diseases as well as for monitoring the progression of pathological disorders. Several types of molecules present in biological fluids can act as biomarkers such as DNA, coding and non-coding RNA, lipids, metabolites, proteins and even microbes. In this context, saliva emerges as a useful diagnostic tool for the detection of biomarkers involved with oral and systemic diseases, since it reflects the pathophysiological conditions of the organism and allows early, rapid, practical and noninvasive detection of biomarkers.Areas covered: This review discusses the properties of saliva as a diagnostic tool and addresses the main identified biomarkers related to dental caries, periodontal disease, head and neck cancer and other types of cancer of considerable incidence among the world population.Expert commentary: Despite extensive efforts which have been directed toward the identification of one or a combination of biomarkers with good predictive values for the early detection of dental caries, periodontal disease and cancer, these biomarkers still need validation before chairside point-of-care devices can be widely used in the clinic.

Metabolic Biomarkers of Squamous Cell Carcinoma of the Aerodigestive Tract: A Systematic Review and Quality Assessment

Introduction. Aerodigestive squamous cell carcinomas (ASCC) constitute a major source of global cancer deaths. Patients typically present with advanced, incurable disease, so new means of detecting early disease are a research priority. Metabolite quantitation is amenable to point-of-care analysis and can be performed in ASCC surrogates such as breath and saliva. The purpose of this systematic review is to summarise progress of ASCC metabolomic studies, with an emphasis on the critical appraisal of methodological quality and reporting.

METHOD

A systematic online literature search was performed to identify studies reporting metabolic biomarkers of ASCC. This review was conducted in accordance with the recommendations of the Cochrane Library and MOOSE guidelines.

RESULTS

Thirty studies comprising 2117 patients were included in the review. All publications represented phase-I biomarker discovery studies, and none validated their findings in an independent cohort. There was heterogeneity in study design and methodological and reporting quality. Sensitivities and specificities were higher in oesophageal and head and neck squamous cell carcinomas compared to those in lung squamous cell carcinoma. The metabolic phenotypes of these cancers were similar, as was the kinetics of metabolite groups when comparing blood, tissue, and breath/saliva concentrations. Deregulation of amino acid metabolism was the most frequently reported theme.

CONCLUSION

Metabolite analysis has shown promising diagnostic performance, especially for oesophageal and head and neck ASCC subtypes, which are phenotypically similar. However, shortcomings in study design have led to inconsistencies between studies. To support future studies and ultimately clinical adoption, these limitations are discussed.

Proteomics approach and techniques in identification of reliable biomarkers for diseases

Biomarkers, also called biological markers, are indicators to identify a biological case or situation as well as detecting any presence of biological activities and processes. Proteins are considered as a type of biomarkers based on their characteristics. Therefore, proteomics approach is one of the most promising approaches in this field. The purpose of this review is to summarize the use of proteomics approach and techniques to identify proteins as biomarkers for different diseases. This review was obtained by searching in a computerized database. So, different researches and studies that used proteomics approach to identify different biomarkers for different diseases were reviewed. Also, techniques of proteomics that are used to identify proteins as biomarkers were collected. Techniques and methods of proteomics approach are used for the identification of proteins' activities and presence as biomarkers for different types of diseases from different types of samples. There are three essential steps of this approach including: extraction and separation of proteins, identification of proteins, and verification of proteins. Finally, clinical trials for new discovered biomarker or undefined biomarker would be on.

Salivary glucose as a non-invasive biomarker of type 2 diabetes mellitus

Background

Every year, millions of people are diagnosed with Diabetes mellitus (DM) and the number of new and undiagnosed cases continue to rise. Diagnosis of diabetes is usually performed by blood glucose analysis after fasting for a certain period. However, this method uses an invasive technique that can cause discomfort and even trauma to some patients which could eventually lead to behavioral changes such as avoidance of healthcare and laboratory testing. Studies that explore the diagnostic value of salivary glucose are promising due to the non-invasiveness of the test procedures and its potential correlation with blood results.

Material and Methods

The study conducted aimed to determine if salivary glucose can be utilized as an alternative to blood glucose in the screening, diagnosis, and monitoring of type 2 diabetes mellitus (T2DM). A total of 75 participants were recruited and equally divided into 3 groups (normal fasting glucose, impaired fasting glucose, and provisional DM) based on their fasting blood glucose (FBG) level. Blood and unstimulated saliva were collected from each participant and were subjected to glucose analysis using the routine glucose oxidase-peroxidase method.

Results

Using Pearson's correlation and linear regression, a high degree and significant correlation was observed between blood and salivary glucose (r = 0.715, p<0.001). Further analysis showed that salivary glucose is 88.5% sensitive and 61.5% specific with a positive predictive value of 45.8%, and a negative predictive value of 97.1%.

Conclusions

Salivary glucose is comparable to blood glucose in diagnosing and monitoring T2DM and is considered more advantageous than blood due to its non-invasive nature. Key words:Saliva, glucose, non-invasive, diabetes.

Top-down proteomic profiling of human saliva in multiple sclerosis patients

Multiple sclerosis is a chronic disease of the central nervous system characterized by inflammation, demyelination and neurodegeneration which is of undetermined origin. To date a single diagnostic test of multiple sclerosis does not exists and novel biomarkers are demanded for a more accurate and early diagnosis. In this study, we performed the quantitative analysis of 119 salivary peptides/proteins from 49 multiple sclerosis patients and 54 healthy controls by a mass spectrometry-based top-down proteomic approach. Statistical analysis evidenced different levels on 23 proteins: 8 proteins showed lower levels in multiple sclerosis patients with respect to controls and they were mono- and di-oxidized cystatin SN, mono- and di-oxidized cystatin S1, mono-oxidized cystatin SA and mono-phosphorylated statherin. 15 proteins showed higher levels in multiple sclerosis patients with respect to controls and they were antileukoproteinase, two proteoforms of Prolactin-Inducible Protein, P-C peptide (Fr.1-14, Fr. 26-44, and Fr. 36-44), SV1 fragment of statherin, cystatin SN Des_1-4, cystatin SN P₁₁ → L variant, and cystatin A T₉₆ → M variant. The differences observed between the salivary proteomic profile of patients suffering from multiple sclerosis and healthy subjects is consistent with the inflammatory condition and altered immune response typical of the pathology. Data are available via ProteomeXchange with identifier PXD009440.

SIGNIFICANCE

To date a single diagnostic test of multiple sclerosis does not exist, and diagnosis is based on multiple tests which mainly include the analysis of cerebrospinal fluid. However, the need for lumbar puncture makes the analysis of cerebrospinal fluid impractical for monitoring disease activity and response to treatment. The possible use of saliva as a diagnostic fluid for oral and systemic diseases has been largely investigated, but only marginally in multiple sclerosis compared to other body fluids. Our study demonstrates that the salivary proteome of multiple sclerosis patients differs considerably compared to that of sex and age matched healthy individuals and suggests that some differences might be associated with the different disease-modifying therapy used to treat multiple sclerosis patients.

Salivary biomarkers and proteomics: future diagnostic and clinical utilities

Saliva testing is a non-invasive and inexpensive test that can serve as a source of information useful for diagnosis of disease. As we enter the era of genomic technologies and -omic research, collection of saliva has increased. Recent proteomic platforms have analysed the human salivary proteome and characterised about 3000 differentially expressed proteins and peptides: in saliva, more than 90% of proteins in weight are derived from the secretion of three couples of "major" glands; all the other components are derived from minor glands, gingival crevicular fluid, mucosal exudates and oral microflora. The most common aim of proteomic analysis is to discriminate between physiological and pathological conditions. A proteomic protocol to analyze the whole saliva proteome is not currently available. It is possible distinguish two type of proteomic platforms: top-down proteomics investigates intact naturally-occurring structure of a protein under examination; bottom-up proteomics analyses peptide fragments after pre-digestion (typically with trypsin). Because of this heterogeneity, many different biomarkers may be proposed for the same pathology. The salivary proteome has been characterised in several diseases: oral squamous cell carcinoma and oral leukoplakia, chronic graft-versus-host disease Sjögren's syndrome and other autoimmune disorders such as SAPHO, schizophrenia and bipolar disorder, and genetic diseases like Down's Syndrome and Wilson disease. The results of research reported herein suggest that in the near future human saliva will be a relevant diagnostic fluid for clinical diagnosis and prognosis.

Serum and salivary ferritin and Hepcidin levels in patients with chronic periodontitis and type 2 diabetes mellitus

BACKGROUND

Iron disorder and abnormal expression of hepcidin play important roles in many diseases, but it is still unclear in chronic periodontitis (CP) and type 2 diabetes mellitus (T2DM). We aimed to assess ferritin and hepcidin levels in serum and saliva of CP patients with or without T2DM.

METHODS

Serum and unstimulated whole saliva samples were collected from 88 participants, who were categorized into 4 groups based on the presence or absence of CP or T2DM. Demographics and general health parameters were recorded. Full-mouth clinical periodontal parameters including probing pocket depth, clinical attachment loss, bleeding index, and plaque index were recorded. Chemiluminescence microparticle immunoassay and enzyme-linked immunosorbent assay were used to detect ferritin and hepcidin concentrations, respectively, in serum and saliva.

RESULTS

Serum ferritin and hepcidin levels in the CP and CP with T2DM groups were higher than in the control group (P < 0.05). Serum hepcidin and serum ferritin are linear correlated (P < 0.001). Serum hepcidin/ferritin values in the CP with T2DM group were significantly lower than those in the T2DM and control groups. Moreover, salivary ferritin levels in the CP and T2DM groups were higher than those in the control group (P < 0.05). There was positively correlation between salivary ferritin and serum ferritin (P = 0.017). Hepcidin concentrations were relatively low in saliva.

CONCLUSIONS

These results suggest that iron overload and hepcidin inadequacy existed in CP with T2DM patients. Salivary ferritin might provide a reference for body iron load.

TRIAL REGISTRATION

ChiCTR-ROC-17012780.

Salivary proteomics of healthy dogs: An in depth catalog

Objective

To provide an in-depth catalog of the salivary proteome and endogenous peptidome of healthy dogs, evaluate proteins and peptides with antimicrobial properties, and compare the most common salivary proteins and peptides between different breed phylogeny groups.

Methods

36 healthy dogs without evidence of periodontal disease representing four breed phylogeny groups, based upon single nucleotide polymorphism haplotypes (ancient, herding/sighthound, and two miscellaneous groups). Saliva collected from dogs was pooled by phylogeny group and analyzed using nanoscale liquid chromatography-tandem mass spectrometry. Resulting tandem mass spectra were compared to databases for identification of endogenous peptides and inferred proteins.

Results

2,491 proteins and endogenous peptides were found in the saliva of healthy dogs with no periodontal disease. All dog phylogeny groups’ saliva was rich in proteins and peptides with antimicrobial functions. The ancient breeds group was distinct in that it contained unique proteins and was missing many proteins and peptides present in the other groups.

Conclusions and clinical relevance

Using a sophisticated nanoscale liquid chromatography-tandem mass spectrometry, we were able to identify 10-fold more salivary proteins than previously reported in dogs. Seven of the top 10 most abundant proteins or peptides serve immune functions and many more with various antimicrobial mechanisms were found. This is the most comprehensive analysis of healthy canine saliva to date, and will provide the groundwork for future studies analyzing salivary proteins and endogenous peptides in disease states.

Construction and characterization of the Korean whole saliva proteome to determine ethnic differences in human saliva proteome

As the first step to discover protein disease biomarkers from saliva, global analyses of the saliva proteome have been carried out since the early 2000s, and more than 3,000 proteins have been identified in human saliva. Recently, ethnic differences in the human plasma proteome have been reported, but such corresponding studies on human saliva in this aspect have not been previously reported. Thus, here, in order to determine ethnic differences in the human saliva proteome, a Korean whole saliva (WS) proteome catalogue indexing 480 proteins was built and characterized through nLC-Q-IMS-TOF analyses of WS samples collected from eleven healthy South Korean male adult volunteers for the first time. Identification of 226 distinct Korean WS proteins, not observed in the integrated human saliva protein dataset, and significant gene ontology distribution differences in the Korean WS proteome compared to the integrated human saliva proteome strongly support ethnic differences in the human saliva proteome. Additionally, the potential value of ethnicity-specific human saliva proteins as biomarkers for diseases highly prevalent in that ethnic group was confirmed by finding 35 distinct Korean WS proteins likely to be associated with the top 10 deadliest diseases in South Korea. Finally, the present Korean WS protein list can serve as the first level reference for future proteomic studies including disease biomarker studies on Korean saliva.

Multiplexed panel of precisely quantified salivary proteins for biomarker assessment

An increasingly popular "absolute" quantitative technique involves the SRM or MRM approach with stable isotope-labeled standards (SIS). Using this approach, many proteins in human plasma/serum have been quantified for biomarker assessment and disease stratification. Due to the complexity of plasma and the invasive nature of its collection, alternative biosamples are currently being explored. Here, we present the broadest panel of multiplexed MRM assays with SIS peptides for saliva proteins developed to date. The validated panel consists of 158 candidate human saliva protein biomarkers, inferred from 244 interference-free peptides. The resulting concentrations were reproducibly quantified over a 6 order-of-magnitude concentration range (from 218 μg/mL to 88 pg/mL; average CVs of 12% over analytical triplicates). All concentrations were determined from reverse standard curves, which were generated using a constant concentration of endogenous material with varying concentrations of spiked-in SIS peptides. The large-scale screening of the soluble and membrane-associated proteins contained within the 158-plex assay could present new opportunities for biomarker assessment and clinical diagnostics.

Human Saliva Collection Devices for Proteomics: An Update

There has been a rapid growth in the interest and adaptation of saliva as a diagnostic specimen over the last decade, and in the last few years in particular, there have been major developments involving the application of saliva as a clinically relevant specimen. Saliva provides a “window” into the oral and systemic health of an individual, and like other bodily fluids, saliva can be analyzed and studied to diagnose diseases. With the advent of new, more sensitive technologies to detect smaller concentrations of analytes in saliva relative to blood levels, there have been a number of critical developments in the field that we will describe. In particular, recent advances in standardized saliva collection devices that were not available three to four years ago, have made it easy for safe, simple, and non-invasive collection of samples to be carried out from patients. With the availability of these new technologies, we believe that in the next decade salivary proteomics will make it possible to predict and diagnose oral as well as systemic diseases, cancer, and infectious diseases, among others. The aim of this article is to review recent developments and advances in the area of saliva specimen collection devices and applications that will advance the field of proteomics.

A Study of the Variation in the Salivary Peptide Profiles of Young Healthy Adults Acquired Using MALDI-TOF MS

A cross-sectional observational study was conducted to evaluate the inter-individual variation in the MALDI-TOF MS peptide profiles of unstimulated whole saliva in a population of 268 systemically healthy adults aged 18–30 yr (150 males and 118 females) with no apparent caries lesions or periodontal disease. Using Spectral Clustering, four subgroups of individuals were identified within the study population. These subgroups were delimited by the pattern of variation in 9 peaks detected in the 2–15 kDa m/z range. An Unsupervised Feature Selection algorithm showed that P-C peptide, a 44 residue-long salivary acidic proline-rich protein, and three of its fragments (Fr. 1–25, Fr. 15–35 and Fr. 15–44) play a central role in delimiting the subgroups. Significant differences were found in the salivary biochemistry of the subgroups with regard to lysozyme and chitinase, two enzymes that are part of the salivary innate defense system (p < 0.001). These results suggest that MALDI-TOF MS salivary peptide profiles may relate information on the underlying state of the oral ecosystem and may provide a useful reference for salivary disease biomarker discovery studies.

Quantitative antibody-free LC-MS/MS analysis of sTRAIL in sputum and saliva at the sub-ng/mL level

Soluble tumor necrosis factor-related apoptosis-inducing ligand (sTRAIL) induces apoptosis via the extrinsic death receptor pathway and may be a biomarker in the pathogenesis of a broad range of diseases. To investigate the role of sTRAIL in asthma, we developed a quantitative LC-MS/MS method with a lower limit of quantitation (LLOQ) of ≈3pM in induced sputum (174pg/mL) and saliva (198pg/mL) without the use of antibodies. sTRAIL was enriched by immobilized metal affinity chromatography (IMAC) solid-phase extraction (SPE) followed by tryptic digestion and subsequent enrichment of a signature peptide by strong cation exchange (SCX) SPE. The method was validated with respect to stability, accuracy and precision using the standard addition approach and fully metabolically (15)N-labelled hrTRAIL as internal standard. Our results indicate that it is possible to quantify cytokines like sTRAIL at the pM level by LC-MS/MS without the use of antibodies, which has, to our knowledge, never been shown before.

Reference ranges for cortisol and α-amylase in mother and newborn saliva samples at different perinatal and postnatal periods

This paper describes a reliable analytical method based on Ultra High-Performance Liquid Chromatography coupled to tandem mass spectrometry to determine cortisol in saliva samples from healthy mothers (n=87) and newborns (n=65) at different time points: (i) 38 weeks of gestation, (ii) in the immediate postnatal period (48h) after a term delivery and, (iii) 3 months after delivery. The procedure is characterized by a simple sample treatment employing a sample volume of 25μL. In addition to this, salivary α-amylase was determined using a commercial kit. We have proposed potential reference ranges in saliva for cortisol (0.7-35nmolL(-1)) and α-amylase (2-500UmL(-1)) in mothers, and for cortisol (0.1-56nmolL(-1)) and α-amylase (0.1-500UmL(-1)) in newborn infants. In addition, statistical differences between the two sensitive population groups (mothers and newborns) at the perinatal and postnatal periods were studied. A lower concentration for maternal cortisol was found at 38 weeks of gestation than at 48h (p=0.048) or 3 months after delivery (p=0.021). Similar results were found for the α-amylase determinations. Hence, higher concentrations than could be expected from a chronic stress marker were found at 3 months after delivery than at 38 weeks of gestation (p<0.001) or 48h after delivery (p<0.001). We conclude that this analytical method could be applied to further clinical research on perinatal and postnatal stress, such as threatened preterm labor and/or parenting stress, respectively.

Proteomics in the Assessment of the Therapeutic Response of Antineoplastic Drugs: Strategies and Practical Applications

Uncovering unknown pathological mechanisms and body response to applied medication are the driving forces toward personalized medicine. In this post-genomic era, all eyes are turned to the proteomics field, searching for answers and explanations by investigating the gene end point functional units-proteins and their proteoforms. The development of cutting-edge mass spectrometric technologies and bioinformatics tools have allowed the life-science community to discover disease-specific proteins as biomarkers, which are often concealed by high sample complexity and dynamic range of abundance. Currently, there are several proteomics-based approaches to investigate the proteome. This chapter focuses on gold standard proteomics strategies and related issues toward candidate biomarker discovery, which may have diagnostic/prognostic as well as mechanistic utility in cancer drug resistance.

Enrichment and identification of glycoproteins in human saliva using lectin magnetic bead arrays

Aberrant glycosylation of proteins is a hallmark of tumorigenesis and could provide diagnostic value in cancer detection. Human saliva is an ideal source of glycoproteins due to the relatively high proportion of glycosylated proteins in the salivary proteome. Moreover, saliva collection is noninvasive and technically straightforward, and the sample collection and storage is relatively easy. Although differential glycosylation of proteins can be indicative of disease states, identification of differential glycosylation from clinical samples is not trivial. To facilitate salivary glycoprotein biomarker discovery, we optimized a method for differential glycoprotein enrichment from human saliva based on lectin magnetic bead arrays (saLeMBA). Selected lectins from distinct reactivity groups were used in the saLeMBA platform to enrich salivary glycoproteins from healthy volunteer saliva. The technical reproducibility of saLeMBA was analyzed with liquid chromatography-tandem mass spectrometry (LC-MS/MS) to identify the glycosylated proteins enriched by each lectin. Our saLeMBA platform enabled robust glycoprotein enrichment in a glycoprotein- and lectin-specific manner consistent with known protein-specific glycan profiles. We demonstrated that saLeMBA is a reliable method to enrich and detect glycoproteins present in human saliva.

Chrono-proteomics of human saliva: variations of the salivary proteome during human development

An important contribution to the variability of any proteome is given by the time dimension that should be carefully considered to define physiological modifications. To this purpose, whole saliva proteome was investigated in a wide age range. Whole saliva was collected from 17 preterm newborns with a postconceptional age at birth of 178-217 days. In these subjects sample collection was performed serially starting immediately after birth and within about 1 year follow-up, gathering a total of 111 specimens. Furthermore, whole saliva was collected from 182 subjects aged between 0 and 17 years and from 23 adults aged between 27 and 57 years. The naturally occurring intact salivary proteome of the 316 samples was analyzed by low- and high-resolution HPLC-ESI-MS platforms. Proteins peculiar of the adults appeared in saliva with different time courses during human development. Acidic proline-rich proteins encoded by PRH2 locus and glycosylated basic proline-rich proteins encoded by PRB3 locus appeared following 180 days of postconceptional age, followed at 7 months (±2 weeks) by histatin 1, statherin, and P-B peptide. The other histatins and acidic proline-rich proteins encoded by PRH1 locus appeared in whole saliva of babies from 1 to 3 weeks after the normal term of delivery, S-type cystatins appeared at 1 year (±3 months), and basic proline-rich proteins appeared at 4 years (±1 year) of age. All of the proteinases involved in the maturation of salivary proteins were more active in preterm than in at-term newborns, on the basis of the truncated forms detected. The activity of the Fam20C kinase, involved in the phosphorylation of various proteins, started around 180 days of postconceptional age, slowly increased reaching values comparable to adults at about 2 years (±6 months) of age. Instead, MAPK14 involved in the phosphorylation of S100A9 was fully active since birth also in preterm newborns.

Can Saliva Proteins Be Used to Predict the Onset of Acute Myocardial Infarction among High-Risk Patients?

Human saliva plays a pivotal role in digesting food and maintaining oral hygiene. The presence of electrolytes, mucus, glycoproteins, enzymes, antibacterial compounds, and gingival crevicular fluid in saliva ensures the optimum condition of oral cavity and general health condition. Saliva collection has been proven non-invasive, convenient, and inexpensive compared to conventional venipuncture procedure. These distinctive advantages provide a promising potential of saliva as a diagnostic fluid. Through comprehensive analysis, an array of salivary proteins and peptides may be beneficial as biomarkers in oral and systemic diseases. In this review, we discuss the utility of human salivary proteomes and tabulate the recent salivary biomarkers found in subjects with acute myocardial infarction as well as respective methods employed. In a clinical setting, since acute myocardial infarction contributes to large cases of mortality worldwide, an early intervention using these biomarkers will provide an effective solution to reduce global heart attack incidence particularly among its high-risk group of type-2 diabetes mellitus patients. The utility of salivary biomarkers will make the prediction of this cardiac event possible due to its reliability hence improve the quality of life of the patients. Current challenges in saliva collection are also addressed to improve the quality of saliva samples and produce robust biomarkers for future use in clinical applications.

Metabolomics for laboratory diagnostics

Metabolomics is an emerging approach in a systems biology field. Due to continuous development in advanced analytical techniques and in bioinformatics, metabolomics has been extensively applied as a novel, holistic diagnostic tool in clinical and biomedical studies. Metabolome's measurement, as a chemical reflection of a current phenotype of a particular biological system, is nowadays frequently implemented to understand pathophysiological processes involved in disease progression as well as to search for new diagnostic or prognostic biomarkers of various organism's disorders. In this review, we discussed the research strategies and analytical platforms commonly applied in the metabolomics studies. The applications of the metabolomics in laboratory diagnostics in the last 5 years were also reviewed according to the type of biological sample used in the metabolome's analysis. We also discussed some limitations and further improvements which should be considered taking in mind potential applications of metabolomic research and practice.