Background: Uric acid (UA) is associated with cardiovascular and metabolic disorders, as well as a wide range of other health conditions and behaviors. A non-invasive measure of UA would be particularly useful in biobehavioral health and clinical research. We examined the validity and stability of salivary UA as a noninvasive measure of serum UA.
Methods: To interrogate the validity of salivary UA as a marker of systemic UA, we measured UA levels in blood and saliva samples collected on a single occasion from healthy adults (n=99; age 18-36 years, 54% male). We examined the serum-saliva correlation for UA and associations between salivary UA and inflammatory markers in serum and saliva, and with self-reported oral health indices. We also tested whether associations of UA with adiponectin and C-reactive protein, circulating markers of cardiovascular health, are evident in saliva. Using longitudinal data from young adults (n=182; age 18-31 years; 46% male) we examined salivary UA stability. Correlations and latent state-trait modeling examined the stability of salivary UA levels; the percent of variance in salivary UA estimates attributable to trait and state-components; and associations of the salivary UA trait component with body mass index (BMI) and sex.
Results: We found a strong positive association between salivary and serum UA. Neither the direction nor the magnitude of this association was related to total protein in saliva, blood leakage into oral fluid, proinflammatory cytokines, or biobehavioral indices of poor oral health. Results also revealed robust inverse associations between UA and adiponectin in both serum and saliva. Salivary UA levels were also highly correlated within and between assessment points 3 hours as well as 2 months apart. Advanced statistical modeling showed the majority (62-66%) of the variance in salivary UA could be attributed to a latent trait component suggesting relative stability in salivary UA levels. Furthermore, BMI and sex were associated with the stable trait-like component of salivary UA.
Conclusions: The findings demonstrate strong measurement validity and stability when UA is measured in saliva, and provide evidence supporting salivary UA as a robust indicator of systemic UA activity. These finding suggest that salivary UA could serve as a biomarker for a wide range of potential conditions and disease states.
Adiponectin: Serum-Saliva Associations and Relations with Oral and Systemic Markers of Inflammation.
Background:
This study addresses gaps in our understanding about the validity and utility of using salivary adiponectin to index serum adiponectin levels. Matched blood and saliva samples were collected on a single occasion from healthy adults (n=99; age 18-36 years, 53% male). Serum and saliva was assayed for adiponectin and inflammatory cytokines (IL-1β, IL-6, IL-8, TNFα), and saliva was also assayed for markers of blood contamination (transferrin), total protein (salivary flow rate) and matrix metalloproteinase-8 (MMP-8). We examined the extent to which salivary adiponectin was associated with serum adiponectin, and the influence of potential confounders on the serum-saliva correlation, including age, sex, body mass index, and markers of inflammation, oral health, salivary blood contamination, and flow rate. Findings revealed a modest serum-saliva association for adiponectin, and strong positive associations between salivary adiponectin and salivary levels of inflammatory cytokines, MMP-8, transferrin, and total protein. By contrast, salivary adiponectin was not related to serum levels of inflammatory activity. The magnitude of the serum-saliva association was strengthened when controlling for total protein in saliva, blood leakage into oral fluid, salivary inflammatory cytokines, and MMP-8. The pattern of findings extends our understanding of salivary adiponectin and its potential use as an index of circulating adiponectin levels.