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.
Association between body mass index and salivary uric acid among Mexican-origin infants, youth and adults: Gender and developmental differences.
Background:
Uric acid (UA) is the end product of the metabolic breakdown of purine nucleotides. Recent studies have measured UA in saliva in relation to obesity and chronic disease risk. Given the increasing prevalence of metabolic syndrome among Latino youth, we examined gender and age differences in salivary uric acid (sUA) and weight in a sample of Mexican-origin children (n = 65, 2 months to 18 years, 49% female) and adults (n = 46, 19-58 years, 72% female). We measured weight, height, waist, and hip circumference and collected saliva samples (later assayed for sUA). Structural equation models estimated the relationship between age, developmental stage, and weight outcomes in relation to sUA levels between genders, while controlling for race. Results demonstrate that increased sUA levels were related to higher BMI percentiles in females of all ages (β = 0.43, p < .001). There were significant differences in sUA levels between developmental stages for girls, with female toddlers having the highest sUA levels (β = .28, p = .02). In an interaction between BMI z-score and gender between youth and adults, BMI has a larger effect on increasing sUA levels among younger girls (β = 0.27, p < .03) and adult women (β = 0.33, p = .02). Levels of sUA may be gender-specific in relation to BMI and developmental stage. View Abstract