Saliva as a non-invasive tool for assessment of metabolic andinflammatory biomarkers in children

Abstract

Background&aims:Epidemiological studies in school-age children are challenging, particularly thosethat aim to analyse metabolic markers on blood samples obtainedviainvasive and stressful procedures.The objective of this paper is to evaluate the use of saliva, as a non-invasive tool in epidemiologicalstudies performed in school-age children, to capture metabolic changes associated with body mass index(BMI), dietary characteristics and physical activity in both boys and girls.Methods:This is an observational study in which healthy children of ages between 8 and 12 years(n¼129, 60 girls and 69 boys) from three schools in a Mediterranean area of Spain were included. Apanel of biomarkers was measured in serum and saliva and correlated with BMI, dietary characteristicsand physical activity.Results:Significant positive correlation between serum and salivary levels were detected for CRP(r¼0.770) in all included children, and boys (r¼0.805) and girls (r¼0.775) separately (P<0.001, in allcases) and for insulin in girls (r¼0.442;P<0.05). Among all studied salivary biomarkers, insulin wassignificantly correlated with the three factors studied: positively with BMI and negatively with dietarycharacteristics (intake and composition) and physical activity (P<0.05). Obesity and diet compositionwere both positively associated to pro-inflammatory biomarkers, CRP and IL1b; while diet compositionshared with physical activity levels the correlation with IL6 (positive with energy, fat, carbohydrate andsaturated fatty acid intake, and negative with cholesterol intake and average physical activity in boys),NGF and glucose (in both cases correlations were negative with diet composition and physical activityvariables) (P<0.05, in all cases). Sex differences were detected in serum glucose and TNFa.Conclusions:Biomarkers in saliva are able to capture differences in BMI, dietary characteristics andphysical activity levels in school-age children. Saliva may potentially constitute a useful non-invasive andstress-free tool to evaluate metabolic markers of inflammation and/or metabolism related to BMI andlifestyle in a sex-dependent manner.