Metabolic disease risk in children by salivary biomarker analysis

Abstract

Objective: The study of obesity-related metabolic syndrome or Type 2 diabetes (T2D) in children is particularly difficult because of fear of needles. We tested a non-invasive approach to study inflammatory parameters in an at-risk population of children to provide proof-of-principle for future investigations of vulnerable subjects.

Design and methods: We evaluated metabolic differences in 744, 11-year old children selected from underweight, normal healthy weight, overweight and obese categories by analyzing fasting saliva samples for 20 biomarkers. Saliva supernatants were obtained following centrifugation and used for analyses.

Results: Salivary C-reactive protein (CRP) was 6 times higher, salivary insulin and leptin were 3 times higher, and adiponectin was 30% lower in obese children compared to healthy normal weight children (all P<0.0001). Categorical analysis suggested that there might be three types of obesity in children. Distinctly inflammatory characteristics appeared in 76% of obese children while in 13%, salivary insulin was high but not associated with inflammatory mediators. The remaining 11% of obese children had high insulin and reduced adiponectin. Forty percent of the non-obese children were found in groups which, based on biomarker characteristics, may be at risk for becoming obese.

Conclusions: Significantly altered levels of salivary biomarkers in obese children from a high-risk population, suggest the potential for developing non-invasive screening procedures to identify T2D-vulnerable individuals and a means to test preventative strategies.

Figure 1. The concentration of biomarkers in saliva supernatant that were significantly different in obese children compared to normal weight children.

Insulin, CRP and leptin significantly increased with obesity whereas adiponectin decreased. Central values represent the median concentration and whiskers represent the interquartile range (+75^th percentile, −25^th percentile).

Figure 2. Total salivary protein concentration and salivary flow rate.

In the subset of 213 samples from children measured for total salivary protein, protein content significantly declined with increased salivary flow rate.

Figure 3. Salivary protein concentration and salivary flow rate of children by body weight category.

Neither protein content nor salivary flow rate differed significantly in this subset of 213 samples between children in each body weight category.

Figure 4. A: Categorical decision tree describing identification of children that are obese or not obese. 76% of the obese children were identified by the predictor variable salivary CRP >219 pg/ml.

Of the lower salivary CRP saliva samples, 13% of the obese children were identified by the predictor variable insulin >128 pg/ml and 11% had insulin ≤128 pg/ml. B: Insulin concentration in fasting saliva supernatant and plasma of 53 adolescent donors. These data were fitted after log transformation to obtain the equation Ln(Plasma) = 0.85*Ln(Saliva) +1.84 with r² = 0.67. Based on this approximation, the predictor variable of 128 pg/ml saliva insulin would be approximately 67 pmoles/L of plasma insulin (or 11 µU/ml using the conversion factor 1µU/ml = 6.00 pmol/L).