Metabonomics Investigations of Human Saliva: Future Diagnostic and Prognostic Monitoring Perspectives

Dear Colleagues,

The multicomponent nuclear magnetic resonance (NMR) or liquid chromatographic-mass spectrometric (LC-MS) analysis of both biofluids and tissues offers a high level of potential regarding the investigation of metabolic processes, and when coupled with contemporary and/or newly-developed multivariate (MV) data analysis techniques, as in metabolomics, serves as an extremely powerful means of probing, the biochemical basis of human disease aetiology, and therapeutic or toxicological processes induced by administered drugs or further xenobiotics, for example. Although to date the great majority of clinically-based metabolomics investigations have focused on the analysis of commonly-collectable biofluids such as human blood plasma, urine and occasionally cerebrospinal fluid, only a small number of these have employed human saliva, albeit generally for oral health assessment purposes only. However, saliva-based metabolomics investigations principally offer many pertinent analytical advantages, since this medium also has the potential to represent the full physiological and disease status of the human body. Moreover, a further major benefit offered by salivary metabolomics technologies is that this biofluid may be collected from patients non-invasively, inexpensively, less stressfully, and without the requirement for clinical supervision. For oral health screening purposes, human saliva represents an ideal biofluid medium for such metabonomic investigations, particularly since when excreted from the salivary and mucous glands, it contains no invading bacteria and only very low concentrations of metabolic agents which may represent ‘biomarkers’ of selected oral diseases. Indeed, in the oral environment, micro-organisms located in tooth plaque, gingival crevices or soft tissues such as gums conduct a range of metabolic functions linked to their growth and prevalence, and hence human saliva contains many excreted catabolites which are unique and dependent on the infiltration, activity and preponderance of bacterial populations  therein. Furthermore, elevated salivary concentrations of markers of inflammatory processes occurring within soft tissue are also anticipated, e.g., ground substance glycosaminoglycans and low-molecular-mass saccharides arising therefrom. Hence, metabolomics strategies serve as extremely valuable tools for probing the multicomponent metabolic status of human saliva, abnormal patterns of which often provide much valuable information regarding the pathologies of human diseases. Areas covered by this Special Issue are, but not limited to, the principles and advantages offered by multi-analytical techniques employed in ‘state-of-the-art’ saliva-based metabolomics investigations; the reliability and reproducibility of such techniques, including their limits of detection and quantification, their selectivities and sensitivities, along with essential quality control and assurance processes for their operation and management, etc.; the value of high-resolution salivary ¹H NMR analysis and other multicomponent analytical techniques to provide potentially valuable salivary biomarker data in patients with clinically-proven oral and non-oral diseases (the former including dental caries, periodontal diseases, oral malodour, etc.); effective validation of such biomarkers; experimental design, and the merits and standardisation of saliva sample collection and preparation techniques; differential methods available for the univariate and MV analysis of salivary metabolomics datasets; statistical power calculations; the value of metabolomics strategies to recognise metabolic ‘signatures’ characteristic of clinically-determined sampling groups, sample donors and clinical severity score status, etc.; the prognostic stratification of patient participants. Overall, this Special Issue will delineate the bioanalytical and chemopathological benefits offered by MV metabolic/biomarker datasets acquired on carefully collected human saliva samples, as will advantages offered by the statistical and computational intelligence modelling of these. Manuscripts covering other relevant challenging research issues will also be welcomed.

Prof. Martin Grootveld
Guest Editor

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• Human Saliva
• Oral Heath
• Metabolomics
• Multivariate Statistics and Modelling
• Computational Intelligence Techniques
• Bioanalytical Chemistry
• Salivary Biomarkers
• Multicomponent Analytical Techniques
• Chemical Pathology