Saliva as a diagnostic fluid

Establishing age-group specific reference intervals of human salivary proteome and its preliminary application for epilepsy diagnosis

Salivary proteins serve multifaceted roles in maintaining oral health and hold significant potential for diagnosing and monitoring diseases due to the non-invasive nature of saliva sampling. However, the clinical utility of current saliva biomarker studies is limited by the lack of reference intervals (RIs) to correctly interpret the testing result. Here, we developed a rapid and robust saliva proteome profiling workflow, obtaining coverage of >1,200 proteins from a 50-µL unstimulated salivary flow with 30 min gradients. With the workflow, we investigated protein variation in a cohort of 1,743 healthy individuals. The significant differences in non-linear saliva proteomes among age groups resulted in the establishment of age-related RIs covering 1,123 salivary protein variations. We then utilized a cohort of 30 epilepsy patients as a case study to illustrate the practical application of RIs in identifying disease-enriched outlier proteins, elucidating their cellular origins, determining disease diagnosis, and visualizing outlier proteins in each epilepsy patient. Our study showed the classification model based on the RI achieved PR-AUC of 0.815 (95%CI: 0.813-0.826). Additionally, we validated these results in an independent test set. Furthermore, the epilepsy cohort could be further stratified into 2 major subtypes, with one subtype characterized by disrupted metabolic proteins and containing mostly Focal Cortical Dysplasia (FCD) type III epilepsy patients. Overall, our study provided a proof-of-principle workflow for the use of salivary proteome for health monitoring, epilepsy diagnosis and subtyping.

Analytical Insights into Methods for Measuring Ischemia-Modified Albumin

Ischemia-modified albumin (IMA) has emerged as a pivotal biomarker for the early detection of ischemic conditions, particularly myocardial ischemia, where timely diagnosis is crucial for effective intervention. This review provides an overview of the analytical methods for assessment of IMA, including Albumin Cobalt Binding (ACB), Albumin Copper Binding (ACuB), Enzyme-Linked Immunosorbent Assay (ELISA), new techniques such as liquid crystal biosensors (LCB), quantum dot coupled X-ray fluorescence spectroscopy (Q-XRF), mass spectrometry (MS), and electron paramagnetic resonance (EPR) spectroscopy. Each method was thoroughly examined for its analytical performance in terms of sensitivity, specificity, and feasibility. The ACB assay is the most readily implementable method in clinical laboratories for its cost-effectiveness and operational simplicity. On the other hand, the ACuB assay exhibits enhanced sensitivity and specificity, driven by the superior binding affinity of copper to IMA. Furthermore, nanoparticle-enhanced immunoassays and liquid crystal biosensors, while more resource-intensive, significantly improve the analytical sensitivity and specificity of IMA detection, enabling earlier and more accurate identification of ischemic events. Additionally, different biological matrices, such as serum, saliva, and urine, were reviewed to identify the most suitable for accurate measurements in clinical application. Although serum was considered the gold standard, non-invasive matrices such as saliva and urine are becoming increasingly feasible due to advances in technology. This review underscores the role of IMA in clinical diagnostics and suggests how advanced analytical techniques have the potential to significantly enhance patient outcomes in ischemic disease management.

A simple and effective method for smartphone-based detection of polyamines in oral cancer

Oral cancer accounts for 50%-70% of all cancer-related deaths in India and ranks sixth among the most frequent cancers globally. Roughly 90% of oral malignancies are histologically arise from squamous cells and are therefore called oral squamous cell carcinoma. Organic polycations known as biogenic polyamines, for example, putrescine (Put), spermidine (Spd), and spermine (Spm), are vital for cell proliferation, including gene expression control, regulation of endonuclease-mediated fragmentation of DNA, and DNA damage inhibition. Higher Spm and Spd levels have been identified as cancer biomarkers for detecting tumour development in various cancers. The current study utilises tannic acid, a polyphenolic compound, as a reducing and capping agent to fabricate AuNPs via a one-step microwave-assisted synthesis. The fabricated TA@AuNPs were utilised as a nanoprobe for colourimetric sensing of polyamines in PBS. When TA@AuNPs are added to the polyamine, the amine groups in polyamines interact with the phenolic groups of TA@AuNPs via hydrogen bonding or electrostatic interactions. These interactions cause the aggregation of TA@AuNPs, resulting in a red shift of the Surface Plasmon Resonance band of TA@AuNPs from 530 nm to 560 nm. The nanoprobe was found to be highly specific for Spm at low concentrations. TA@AuNPs were able to detect Spm successfully in artificial saliva samples. On recording the RGB values of the sensing process using a smartphone app, it was found that as the nanoparticles aggregated due to the presence of Spm, the intensity of theR-value decreased, indicating the aggregation of TA@AuNPs due to interaction with the polyamine.

A systematic review and meta-analysis of the validation of serological methods for detecting anti-Toxoplasma gondii antibodies in humans and animals

Toxoplasma gondii is a paradigmatic zoonotic parasite from the One Health perspective, since it is broadly distributed and virtually infects all warm-blooded species. A wide variety of serological techniques have been developed to detect T. gondii infection in humans and animals. Our aim was to describe and compare the main characteristics of these serological tests and validation processes and to critically analyze whether these tests meet the standards required to ensure an accurate serological diagnosis. The current systematic review and meta-analysis included 134 studies that were published from 2013 to 2023. QUADAS 2 tool was used to evaluate the quality of the included studies. A total of 52 variables related to the characteristics of the techniques and analytical and diagnostic validation parameters were studied. A wider panel of tests was developed for humans, including techniques exclusively developed for humans that involve costly equipment and the measurement of different Ig isotypes that are considered biomarkers of congenital toxoplasmosis. Studies conducted in humans frequently employed commercial techniques as reference tests, measured different immunoglobulin isotypes with a predominance for IgG (>50%) and discriminated between acute and chronic infections. In animals, the most commonly used reference techniques were in-house tests, which almost exclusively detected IgG. Common limitations identified in a large number of studies were some misunderstandings of the terms "gold standard" and "reference test" and the absence of information about the negative and positive control sera used or the exact cutoff employed, which were independent of the quality of the study. There is a lack of analytical validation, with few evaluations of cross-reactivity with other pathogens. Diagnostic odds ratio values showed that indirect ELISA based on native or chimeric antigens performed better than other tests. The reproducibility of serological test results in both humans and animals is not guaranteed due to a lack of relevant information and analytical validation. Thus, several key issues should be considered in the future, including interlaboratory ring trials.

Saliva - a new opportunity for fluid biopsy

Saliva is a complex biological fluid with a variety of biomolecules, such as DNA, RNA, proteins, metabolites and microbiota, which can be used for the screening and diagnosis of many diseases. In addition, saliva has the characteristics of simple collection, non-invasive and convenient storage, which gives it the potential to replace blood as a new main body of fluid biopsy, and it is an excellent biological diagnostic fluid. This review integrates recent studies and summarizes the research contents of salivaomics and the research progress of saliva in early diagnosis of oral and systemic diseases. This review aims to explore the value and prospect of saliva diagnosis in clinical application.

Optimisation of saliva volumes for lipidomic analysis by nanoflow ultrahigh performance liquid chromatography-tandem mass spectrometry

Saliva is a readily accessible and clinically useful biofluid that can be used to develop disease biomarkers because of a variety of biologically active molecules in it that are also found in blood. However, even though saliva sampling is simple and non-invasive, few studies have investigated the use of salivary lipids as biomarkers, and the extraction of lipids from saliva needs to be examined thoroughly. In the present study, methods (i.e., saliva sample volume, 0.1-1.0 mL) for the extraction and analysis of salivary lipids by nanoflow ultrahigh performance liquid chromatography-tandem mass spectrometry (nUHPLC-ESI-MS/MS) were evaluated according to the matrix effect, extraction recovery, and number of quantifiable lipids. A total of 780 lipids were identified in a pooled saliva sample from 20 healthy volunteers, and 372 lipids without differentiating acyl chain structures were quantified, along with comprehensive information on salivary lipid composition and individual lipid levels. Even though extraction recovery was maintained at saliva sample volumes as low as 0.2 mL, the matrix effect and limit of detection (LOD) were relatively large with 1.0 mL. Considering the matrix effect, LOD, and number of quantifiable lipids (>limit of quantitation), the minimum volume of saliva sufficient for lipidomic analysis using nUHPLC-ESI-MS/MS was determined to be 0.5 mL.

Salivary Uric Acid: A Noninvasive Wonder for Clinicians?

This review is a summary of the modern-day approach and recent trend in the determination of uric acid in the saliva of humans and its use in diagnosis by clinicians. Uric acid, which is the end product obtained from the breakdown of purine nucleotides, is an important biomarker associated with various conditions. Uric acid is found in various body fluids, such as serum, plasma, and urine. It can be used as an important tool for various diseases, such as gout and hyperuricemia, or conditions that are associated with increased oxidative stress. Recently, there has been an emergence of studies that have utilized uric acid concentrations measured in the saliva and studied its association with various diseases. Salivary uric acid can prove to be a noninvasive method to provide a diagnosis of serious illness. A raised uric acid level in the saliva can be associated with cancer, human immunodeficiency virus (HIV) infection, gout, and hypertension. A reduced level of salivary uric acid on the other hand can be a marker for Alzheimer's disease, progression of multiple sclerosis, and impairment of cognition. Online search databases, including Google Scholar, Scopus, PubMed, and Web of Science, were searched, and articles that were published before September 2021 based on salivary uric acid analysis were analyzed for this review. Uric acid is an essential biomarker that has antioxidant properties. Assessment of salivary uric acid levels was found to be essential in conditions such as cancer, metabolic syndrome, neurological conditions, psychiatric conditions, human immunodeficiency virus, and gout and in monitoring treatment of hyperuricemia. Although having importance in diagnosis and therapeutic monitoring, salivary uric acid analysis has not gained enough popularity due to limitations such as saliva collection and sample processing issues. With proper education and standardization, salivary uric acid analysis can be used as a cost-effective and noninvasive tool for getting a clue about antioxidant biomarker concentration in saliva and hence various diseases associated with oxidative stress.

Identification of Possible Salivary Metabolic Biomarkers and Altered Metabolic Pathways in South American Patients Diagnosed with Oral Squamous Cell Carcinoma

Oral squamous cell carcinoma (OSCC) represents 90% of oral malignant neoplasms. The search for specific biomarkers for OSCC is a very active field of research contributing to establishing early diagnostic methods and unraveling underlying pathogenic mechanisms. In this work we investigated the salivary metabolites and the metabolic pathways of OSCC aiming find possible biomarkers. Salivary metabolites samples from 27 OSCC patients and 41 control individuals were compared through a gas chromatography coupled to a mass spectrometer (GC-MS) technique. Our results allowed identification of pathways of the malate-aspartate shuttle, the beta-alanine metabolism, and the Warburg effect. The possible salivary biomarkers were identified using the area under receiver-operating curve (AUC) criterion. Twenty-four metabolites were identified with AUC > 0.8. Using the threshold of AUC = 0.9 we find malic acid, maltose, protocatechuic acid, lactose, 2-ketoadipic, and catechol metabolites expressed. We notice that this is the first report of salivary metabolome in South American oral cancer patients, to the best of our knowledge. Our findings regarding these metabolic changes are important in discovering salivary biomarkers of OSCC patients. However, additional work needs to be performed considering larger populations to validate our results.

Detection of SARS-CoV-2 in saliva and characterization of oral symptoms in COVID-19 patients

OBJECTIVES

In order to provide a more comprehensive understanding of the effects of SARS-CoV-2 on oral health and possible saliva transmission, we performed RNA-seq profiles analysis from public databases and also a questionnaire survey on oral-related symptoms of COVID-19 patients.

MATERIALS AND METHODS

To analyse ACE2 expression in salivary glands, bulk RNA-seq profiles from four public datasets including 31 COVID-19 patients were recruited. Saliva and oropharyngeal swabs were collected. SARS-CoV-2 nucleic acids in saliva were detected by real-time polymerase chain reaction (RT-PCR). Additionally, a questionnaire survey on various oral symptoms such as dry mouth and amblygeustia was also carried out on COVID-19 patients.

RESULTS

ACE2 expression was present at detectable levels in the salivary glands. In addition, of four cases with positive detection of salivary SARS-CoV-2 nucleic acids, three (75%) were critically ill on ventilator support. Furthermore, we observed the two major oral-related symptoms, dry mouth (46.3%) and amblygeustia (47.2%), were manifested by a relatively high proportion of 108 COVID-19 patients who accepted the questionnaire survey.

CONCLUSIONS

This study confirms the expression of ACE2 in the salivary glands and demonstrates the possibility of SARS-CoV-2 infection of salivary glands. Saliva may be a new source of diagnostic specimens for critically ill patients, since it can be easily collected without any invasive procedures. In addition, dry mouth and amblygeustia can be considered as initial symptoms of COVID-19 infection.

Comparative evaluation of peptidome and microbiota in different types of saliva samples

Background

Clinical and research interest in salivary peptidome and microbiota is ever-growing owing to its great value for diagnosis, risk assessment and prediction of prognosis in oral and systemic diseases. Saliva can be stimulated for the purpose of rapid collection, but currently there are no studies systematically addressing the similarities and differences of salivary peptidome and microbiota in different types of samples. The purpose of this study was to investigate the variations of salivary peptidome and microbial profiles in response to different stimulating conditions.

Methods

Unstimulated saliva and three types of stimulated saliva samples (olfaction, gustation, and mastication stimulated saliva) were collected from 10 systematically and orally healthy donors. The peptidome profiles were detected by weak cation exchange magnetic beads and analyzed through matrix-assisted laser desorption/ionization-time of flight-mass spectrometry (MALDI-TOF MS), while their microbial profiles were analyzed by 16S rDNA V3-V4 hypervariable region amplicon sequencing utilizing the Illumina MiSeq PE300 platform. The distance matrixes of salivary peptidome and microbial profiles were generated and the intra-individual distances were extracted, then the variations brought by different sampling conditions and repeated collections were compared.

Results

By comparisons of the overall salivary peptidome and microbial profiles, olfactory stimulation led to minimal variations comparing with that of unstimulated saliva, but appreciable variations were observed between saliva samples collected with gustatory/masticatory stimulation and unstimulated saliva. The three types of stimulated saliva exhibited significantly different peptidome and microbial profiles.

Conclusions

Stimulated saliva collected in response to olfactory stimulation is an appropriate alternative to unstimulated saliva, whereas gustatory/masticatory stimulation introduced appreciable variations. It is suggested that only one type of stimulating method should be used throughout one peptidome/microbiome research, which provides comprehensive insight into the optimization of sampling methods for salivaomic studies in the future.

Salivary β2-microglobulin levels in patients with erosive oral lichen planus and squamous cell carcinoma

OBJECTIVES

β2 microglobulin, as a biomarker, is used for the diagnosis of oral malignant and pre-malignant lesions. The components of the microglobulin system can directly or indirectly help grow and develop tumors. The present study aims to compare beta-2 microglobulin levels in patients with lichen planus of the esophagus, oral squamous cell carcinoma, and healthy individuals. Further, it evaluated the salivary β2-microglobulin level in malignant and pre-malignant lesions. Oral lichen planus (OLP) is a chronic skin-mucus disorder. Of the total 75 patients referred to Oral Medicine at Dentistry School of Zahedan University of Medical Sciences, 25 were healthy and 25 had oral lichen planus (OLP) and the rest had squamous cell carcinoma (SCC). To collect the saliva samples, unstimulated spitting was used. They were collected between 9 and 12 a.m. Salivary beta2 microglobulin was recorded based on the factory instructions by ELISA optical density method with 450 nm wavelength for each sample. The data were analyzed using descriptive, Kruskal-Wallis and Mann-Whitney and Pearson's correlation coefficient (SPSS 21).

RESULTS

The salivary β2 microglobulin level in patients with squamous cell carcinoma (SCC) and oral lichen plan (OLP) is significantly higher than that in healthy group. Thus, this index is used for assessing early malignant transformation and oral pre-malignant lesion.

A Review of Salivary Diagnostics and Its Potential Implication in Detection of Covid-19

Saliva is an exocrine secretion produced from the salivary glands and has numerous functions, such as cleansing and protection of the oral cavity, antimicrobial effects and aids in digestion. Due to the speedy development in the field of salivaomics, saliva is now well accepted as a pool of biological markers that vary from changes in biochemicals, nucleic acids and proteins to the microflora. Saliva has an immense potential as a diagnostic fluid and offers an edge over other biological fluids as its collection method does not require invasive procedure, economical and is useful for monitoring systemic health. Development of sensitive and precise salivary diagnostic tools and the formulation of defined guidelines following meticulous testing will allow salivary diagnostics to be utilised as chair side tests for various oral and systemic diseases in the near future. The coronavirus disease (Covid-19) pandemic is the biggest challenge and global health crisis for the world since World War Two. Rapid and accurate diagnosis of Covid-19 is crucial in controlling the outbreak in the community and in hospitals. Nasopharyngeal and oropharyngeal swabs are the recommended specimen types for Covid-19 diagnostic testing. The collection of these specimen types requires close contact between healthcare workers and patients and poses a risk of transmission of the virus, causes discomfort and may cause bleeding, especially in patients with condition such as thrombocytopenia. Hence, nasopharyngeal or oropharyngeal swabs are not desirable for sequential monitoring of viral load. Saliva specimens can be obtained easily as the patient is asked to spit into a sterile bottle. The collection of saliva is non-invasive and greatly minimizes the exposure of healthcare workers to Covid-19. Saliva has a high consistency rate of greater than 90% with nasopharyngeal specimens in the detection of respiratory viruses, including coronaviruses. Saliva has also been used in screening respiratory viruses among hospitalized patients without pyrexia or respiratory symptoms. SARS-CoV can be detected in saliva at high titers. Salivary diagnostics is a dynamic field that is being incorporated as part of disease diagnosis, clinical monitoring of systemic health and to make significant clinical decisions for patient care. More research is required to analyze the potential diagnostic of Covid-19 in saliva to develop rapid chair side tests for the detection of Covid-19 and it is also pivotal to improve and develop successful strategies for prevention, especially for dentists and healthcare professionals who are involved in performing aerosol-generating procedures.

Saliva Proteomics Analysis Offers Insights on Type 1 Diabetes Pathology in a Pediatric Population

The composition of the salivary proteome is affected by pathological conditions. We analyzed by high resolution mass spectrometry approaches saliva samples collected from children and adolescents with type 1 diabetes and healthy controls. The list of more than 2000 high confidence protein identifications constitutes a comprehensive characterization of the salivary proteome. Patients with good glycemic regulation and healthy individuals have comparable proteomic profiles. In contrast, a significant number of differentially expressed proteins were identified in the saliva of patients with poor glycemic regulation compared to patients with good glycemic control and healthy children. These proteins are involved in biological processes relevant to diabetic pathology such as endothelial damage and inflammation. Moreover, a putative preventive therapeutic approach was identified based on bioinformatic analysis of the deregulated salivary proteins. Thus, thorough characterization of saliva proteins in diabetic pediatric patients established a connection between molecular changes and disease pathology. This proteomic and bioinformatic approach highlights the potential of salivary diagnostics in diabetes pathology and opens the way for preventive treatment of the disease.

Reduced salivary amylase activity in metabolic syndrome patients with obesity could be improved by treatment with a dipeptidyl peptidase IV inhibitor

OBJECTIVES

The present study is to investigate the salivary gland function of metabolic syndrome (MetS) patients, as indicated by salivary flow rate, amylase activity, and salivary oxidative stress, by measuring MDA level.

MATERIALS AND METHODS

One hundred and eighty-one MetS patients from Maharaj Nakorn Chiang Mai Hospital were enrolled onto this study. The metabolic parameters of each patient were collected and evaluated. Unstimulated saliva was also collected for 5 min. Salivary gland functions, including salivary flow rate, amylase activity, and salivary MDA levels, were investigated.

RESULTS

High levels of triglycerides, high-density lipoprotein, blood pressure, and waist circumference in MetS patients did not show a correlation with altered salivary gland function. However, a decrease in salivary flow rate was observed in MetS patients with hyperglycemia. In addition, decreased amylase activity was found in MetS patients with obesity (BMI ≥ 23 kg/m²). Salivary amylase activity of MetS patients treated with dipeptidyl peptidase IV (DPP-IV) inhibitor was significantly greater than that observed in MetS patients without a DPP-IV inhibitor. Moreover, the salivary amylase activity in MetS patients was found to be independently positively correlated with DPP-IV inhibitor therapy (r = 0.708, p < 0.01).

CONCLUSION

These findings suggest that obesity and hyperglycemia in MetS patients were associated with the impairment of salivary glands. Treatment with a DPP-IV inhibitor was found to exert beneficial effects on the salivary gland.

CLINICAL RELEVANCE

This study demonstrated the impairment of salivary glands of MetS patients and the beneficial effect of DPP-IV inhibitor treatment in the salivary glands.

[Application of saliva in disease diagnosis]

Saliva is secreted by salivary glands and performs a variety of functions, including mouth cleaning and protection, antibacterial activity, and digestion. With the rapid progress in salivaomics, saliva became recognized as a potential pool of biological markers. Being a non-invasive and safe source, saliva is a potential substitute for blood in diagnosis and prognosis of diseases. This review summarizes the latest advancement in saliva-related studies and presents the potential value of saliva in early diagnosis of oral diseases, such as dental caries, periodontal disease, cancer, diabetes, and other systemic disorders. Saliva biomarkers can reveal changes ranging from changes in biochemical index, DNA, RNA, and proteins to the diversification of microbiota structure. By integrating recent data, this paper discusses the clinical significance and application prospect of saliva in early diagnosis of diseases and in translational and precision medicine.

Salivary flow rate, buffer capacity, and urea concentration in adolescents with type 1 diabetes mellitus

BACKGROUND

The objective of the study was to analyze salivary flow rate, urea concentration, and buffer capacity in adolescents with type 1 diabetes mellitus (type 1 DM) in two different stages.

METHODS

This study was performed on adolescents (14-19 years), allocated between two groups: type 1 DM group comprised 32 adolescents with type 1 DM, and non-type 1 DM group comprised 32 nondiabetics. The adolescents in type 1 DM group were evaluated at a baseline (T0) and after 15 months (T1), and those in non-type 1 DM group were only evaluated at T0. Diabetic status was determined by glycosylated hemoglobin (GHb) and capillary glucose tests. Measurement of salivary flow was performed by means of stimulated saliva (SSFR) collection. The buffer capacity (BC) was determined, and analysis of urea salivary concentration was performed using the colorimetric method.

RESULTS

At T0, there were significant differences between diabetics and nondiabetics for SSFR and BC (p<0.05). In diabetics, SSFR was 0.790 mL/min in T0 and 0.881 mL/min in T1 (p>0.05). BC at T0 was 4.8, and at T1, it was 3.9 (p=0.000). Urea concentration mean value had a significant decrease at T1 (28.13) compared with T0 (34.88) (p=0.013). There was a negative correlation between SSFR and urea salivary concentration at both T0 (r=-0.426, p≤0.05) and T1 (r=-0.601, p≤0.01).

CONCLUSIONS

In adolescents with type 1 DM, hyposalivation at T0 was associated with an increase in urea salivary concentration. At T1, hyposalivation was associated with a reduction in BC, and an increase in salivary urea.

Saliva in the diagnosis of diseases

Saliva is secreted from the salivary glands and has multiple functions, including mouth cleaning and protection, antibacterial effects and digestion. With the rapid advancement in salivaomics, saliva is well recognized as a pool of biological markers. Saliva, as a non-invasive and safe source, could be a substitute for blood in the diagnosis and prognosis of diseases. This review summarizes the latest advancements in saliva-related studies and addresses the potential value of saliva in the early diagnosis of oral diseases, such as dental caries and periodontal disease, as well as cancer, diabetes and other systemic disorders. Saliva biomarkers range from changes in the biochemical indices of DNA, RNA and proteins to the diversification of microbiota structures. This study integrates data reported in the recent literature and discusses the clinical significance and prospects for the application of saliva in the early diagnosis of diseases, translational medicine and precision medicine.

Metabolomics for biomarker discovery in gastroenterological cancer

The study of the omics cascade, which involves comprehensive investigations based on genomics, transcriptomics, proteomics, metabolomics, etc., has developed rapidly and now plays an important role in life science research. Among such analyses, metabolome analysis, in which the concentrations of low molecular weight metabolites are comprehensively analyzed, has rapidly developed along with improvements in analytical technology, and hence, has been applied to a variety of research fields including the clinical, cell biology, and plant/food science fields. The metabolome represents the endpoint of the omics cascade and is also the closest point in the cascade to the phenotype. Moreover, it is affected by variations in not only the expression but also the enzymatic activity of several proteins. Therefore, metabolome analysis can be a useful approach for finding effective diagnostic markers and examining unknown pathological conditions. The number of studies involving metabolome analysis has recently been increasing year-on-year. Here, we describe the findings of studies that used metabolome analysis to attempt to discover biomarker candidates for gastroenterological cancer and discuss metabolome analysis-based disease diagnosis.

Saliva: A Cutting Edge in Diagnostic Procedures

The ability to monitor the health and disease status of the patient through saliva is a highly desirable goal for the health professionals. Considering the microconcentration of salivary constituents, saliva is explored to be diagnostic tool as it also meets the demands for an inexpensive, noninvasive and easy to use screening method. The incorporation of salivary diagnostics into clinical practice is gaining reality and will be of diagnostic value in the prospective future. The investigative use of saliva is not being applied only in dental health but also in various other systemic disorders. The advent of molecular techniques is gaining attention and this has triggered its application as a specific and sensitive biomarker in proteomics, genomics, and transcriptomics. This review discusses the basics of salivary diagnostics, expectoration techniques, and its application in various local and systemic disorders.

The human salivary proteome is radiation responsive

In the event of a nuclear incident in a heavily populated area, the surge in demand for medical evaluation will likely overwhelm our emergency care system, compromising our ability to care for victims with life-threatening injuries or exposures. Therefore, there exists a need for a rapidly deployable biological assay for radiation exposure that can be performed in the field by individuals with little to no medical training. Saliva is an attractive biofluid for this purpose, due to the relative ease of its collection and the wide array of biomolecules it contains. To determine whether the human salivary proteome is responsive to ionizing radiation exposure, we characterized the abundances of salivary proteins in humans before and after total body irradiation. Using an assay panel targeting 90 analytes (growth factors, chemokines and cytokines), we identified proteins that were significantly radiation responsive in human saliva. The responses of three proteins (monocyte chemo-attractant protein 1, interleukin 8 and intercellular adhesion molecule 1) were confirmed using independent immunoassay platforms and then verified and further characterized in 130 saliva samples from a completely independent set of 38 patients undergoing total body irradiation. The results demonstrate the potential for detecting radiation exposure based on analysis of human saliva.

Oral fluids that detect cardiovascular disease biomarkers

OBJECTIVE

The aim of this study was to determine the utility of oral fluids for assessment of coronary and cardiovascular (CV) health.

STUDY DESIGN

Twenty-nine patients with preexisting CV disease underwent an invasive cardiac procedure (alcohol septal ablation or percutaneous coronary intervention) and provided unstimulated whole saliva (UWS), sublingual swabs (LS), gingival swabs (GS) and serum at 0, 8, 16, 24, and 48 hours. Concentrations of 13 relevant biomarkers were determined and correlated with levels in serum and the oral fluids.

RESULTS

Concentrations of the majority of biomarkers were higher in UWS than in LS and GS. Coronary and CV disease biomarkers in UWS correlated better with serum than with LS and GS based on group status and measures of time effect. Seven biomarkers demonstrated time effect changes consistent with serum biomarkers, including C-reactive protein and troponin I.

CONCLUSIONS

Changes in serum biomarker profiles are reflected in oral fluids suggesting that oral fluid biomarkers could aid in the assessment of cardiac ischemia/necrosis.

Salivary peptidome in type 1 diabetes mellitus

Diabetic patients show a high susceptibility to oral diseases of inflammatory, catabolic and chronic nature with potential impact on saliva composition. In this study, our purpose was to characterize type 1 diabetes-induced alterations in the salivary peptidome aiming to find prospective biomarkers for type 1 diabetes oral health evaluation. Peptidomic analysis of saliva from controls (n = 5) and type 1 diabetic patients (n = 5) were performed by liquid chromatography followed by mass spectrometry. The proteolytic activity and metalloproteinases expression was accessed by zymography and slot blot analysis, respectively. Data evidenced a significant increase in the percentage of peptides in diabetic patients paralleled by a higher proteolytic activity, compared with healthy individuals. The nonsalivary gland protein fragments identified in saliva were mainly derived from collagen and extracellular matrix proteins, namely collagen type I. The cleavage site frequency analysis showed significant differences between healthy and type 1 diabetic individuals, highlighting the activity of proteases such as matrix metalloproteinase-9 and cathepsin D. Our results highlight salivary collagen fragments as potential biomarkers to follow up diabetes-related oral damage.

Salivary markers for oral cancer detection

Oral cancer refers to all malignancies that arise in the oral cavity, lips and pharynx, with 90% of all oral cancers being oral squamous cell carcinoma. Despite the recent treatment advances, oral cancer is reported as having one of the highest mortality ratios amongst other malignancies and this can much be attributed to the late diagnosis of the disease. Saliva has long been tested as a valuable tool for drug monitoring and the diagnosis systemic diseases among which oral cancer. The new emerging technologies in molecular biology have enabled the discovery of new molecular markers (DNA, RNA and protein markers) for oral cancer diagnosis and surveillance which are discussed in the current review.

Differential salivary proteome profile-based predictive model for discrimination between gastric cancer and chronic gastritis

AIM: To investigate the differential salivary protein expression profile between chronic gastritis and gastric cancer using mass spectrometry-based proteomic technique, and to seek specific biomarkers for discrimination between gastric cancer and chronic gastritis.

METHODS: Saliva specimens collected from gastric cancer patients and chronic gastritis patients were detected using weak cation exchange magnetic beads and matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS). Corresponding peptide mass fingerprint was obtained to develop a differential diagnostic model for discrimination between chronic gastritis and gastric cancer.

RESULTS: A total of 77 differential protein peaks were observed between chronic gastritis patients and gastric cancer patients. One protein peak with a mass-to-charge ratio of 6 021.72 Da was statistically significant (P < 0.05). Based on the analysis of the expression profile of this differential protein, a predictive model for discrimination between gastric cancer and chronic gastritis was developed. The model has a specificity of 95.65% and a sensitivity of 71.43%.

CONCLUSION: The protein expression profiles of saliva specimens collected from gastric cancer patients and chronic gastritis patients are obtained. The diagnostic model for discrimination between gastric cancer and chronic gastritis is developed based on the expression profile of a differential protein with a molecular weight of 6 021.72 Da.

Within-subject variability in repeated measures of salivary analytes in healthy adults

BACKGROUND

Saliva contains a large number of biomolecules, some of which have putative diagnostic usefulness. A potential problem with the use of biomolecules in diagnosis is day-to-day fluctuation due to within-subject variability. This study evaluated the intraindividual variability of six salivary analytes in healthy adults and determined their normal range.

METHODS

Unstimulated whole saliva (5 ml) was collected every 2 to 3 days on six occasions from 30 subjects in good oral and systemic health. Four of the samples were collected in the clinic, and two were collected by the subject at home. The concentration ranges of interleukin (IL)-1beta, IL-6, matrix metalloproteinase-8, prostaglandin E(2), tumor necrosis factor-alpha, interferon-alpha, and albumin were examined. Descriptive statistics were computed, and a one-way random-effects model was used to quantify within- and between-subject components of variability. Intraclass correlation coefficients (ICCs) were calculated for each subject/analyte combination.

RESULTS

Within-subject coefficients of variation for these analytes ranged from 67.6% to 172.1% for the in-clinic samples and from 111.9% to 201.0% for the at-home samples. The ICC for the various analytes ranged from 41% to 61% for the in-clinic samples. The at-home samples exhibited significantly more variability than did those obtained in the clinic under supervision.

CONCLUSIONS

There was marked within-subject variation in the salivary concentrations of these analytes. With increased interest in salivary diagnostics, the within-subject variability, normal range, and threshold levels for abnormal levels of individual salivary analytes need to be determined if these diagnostics tests are to have clinical usefulness.

Determination of total, free and saliva mycophenolic acid with a LC-MS/MS method: application to pharmacokinetic study in healthy volunteers and renal transplant patients

Mycophenolic acid (MPA) is the active moiety of mycophenoate mofetil (MMF), an ester prodrug widely used as an immunosuppressant. Therapeutic drug monitoring (TDM) of MPA is becoming mandatory for transplant patients received MMF therapy in the routine clinical practice because of large individual variability, dose-related toxicity and the risk of acute rejection. In this study, a rapid, sensitive and selective LC-MS/MS method was developed and validated for the quantitative analysis of total and free MPA in plasma and in saliva that uses one identical liquid chromatographic and mass spectrometric condition. Following protein precipitation for total and saliva MPA, and ultrafiltration for free MPA, chromatographic separation was performed on an Allure PFP Propyl analytical column (100 x 2.1 mm, 5 microm, RESTEK Co., Bellefonte, PA, USA) with 0.1% formic acid in acetonitrile and 0.1% formic acid in water (45:55, v/v) as the mobile phases. The compounds were quantified by positive electrospray ionization tandem mass spectrometry. Selectivity, linearity, accuracy, precision, recovery, matrix effect, and saliva stability were evaluated during method validation. The validated method was applied to a pharmacokinetic study of MPA after an oral administration of a single 1000 mg of MMF to eight healthy male volunteers and 750 mg bid of MMF to nine renal transplant patients.

Age and gender related differences in human parotid gland gene expression

OBJECTIVE

The present study evaluated differences in gene expression associated with age and gender in the human parotid gland.

DESIGN

Parotid gland tissue was analysed using the Affymetrix GeneChip HGU133plus2.0 array.

RESULTS

Differential gene expression, defined as a statistically significant difference with a 1.5-fold or greater change, was detected in 787 gene probe sets; 467 (approximately 59%) showed higher expression in females. Several genes associated with saliva secretion were differentially expressed in male and female parotid glands including vesicle-associated membrane protein 3 VAMP3, synaptosomal-associated protein SNAP23, RAS oncogene family member RAB1A and the syntaxin binding protein STXBP1. Evaluation of gene expression in the youngest and the oldest female subjects revealed that the expression of 228 probe sets were altered during aging; 155 genes were up-regulated in the aged female parotid gland. However, of the genes that were altered during aging, 22 of the 30 probes (73%) classified as being associated with immune responses were down-regulated in the aged parotid gland. A panel of differentially expressed, age- and gender-related genes was selected for validation by quantitative, real-time RT-PCR. Comparable differences in gene expression were detected by both Affymetrix array and quantitative, real-time RT-PCR methods.

CONCLUSIONS

Our data suggest that salivary gland function may be adversely affected in the aged population due, at least in part, to the altered regulation of several categories of genes. Moreover, the gender specific differences in gene expression identified in the present study correlate with the previously observed sexual dimorphism in salivary gland function.