Saliva as a non-invasive diagnostic tool for inflammation and insulin-resistance

Abstract

Saliva has been progressively studied as a non-invasive and relatively stress-free diagnostic alternative to blood. Currently, saliva testing is used for clinical assessment of hormonal perturbations, detection of HIV antibodies, DNA analysis, alcohol screening, and drug testing. Recently, there has been increasing interest in evaluating the diagnostic potential of saliva in obesity, inflammation, and insulin-resistance. Current literature has demonstrated elevated levels of inflammatory biomarkers including C-reactive protein, tumor necrosis factor-α, interleukin-6, and interferon-γ in saliva of obese/overweight children and adults. Salivary antioxidant status has also been studied as a measure of oxidative stress in individuals with type 2 diabetes. Further, several studies have demonstrated correlations of salivary markers of stress and insulin resistance including cortisol, insulin, adiponectin, and resistin with serum concentrations. These findings suggest the potential diagnostic value of saliva in health screening and risk stratification studies, particularly in the pediatric population, with implications for inflammatory, metabolic and cardiovascular conditions. However, additional studies are required to standardize saliva collection and storage procedures, validate analytical techniques for biomarker detection, and establish reference ranges for routine clinical use. The purpose of this review is to summarize and evaluate recent advancements in using saliva as a diagnostic tool for inflammation and insulin-resistance.

Keywords: Saliva; Inflammation; Cytokines; Insulin resistance; Adipokines

Core tip: Recent studies have shown that salivary concentrations of several inflammatory cytokines and insulin resistance indices (which may be lower than serum concentrations) may mirror alterations in systemic concentrations of such biomarkers. Saliva offers a promising diagnostic alternative, compared to blood sampling, for screening for inflammatory, metabolic, and cardiovascular risk factors particularly among pediatric and geriatric populations where blood sampling may be difficult. Additional research is needed to validate salivary biomarkers and establish reference ranges and characterize the influence of diet, physical activity, and drug treatment.