Factors influencing the response of urease to sucrose in vivo

Objective: To identify factors that may influence the regulation of urease expression and activity in response to sucrose exposure in vivo.

Methods: Urease activity was measured in dental plaque and saliva of 20 children during fasting conditions and 30 min after rinsing with a 10% sucrose solution. Streptococcus salivarius ureC-specific mRNA in saliva was quantified using Real-Time RT-PCR in a sub-group of 11 subjects. Linear regression models were used to explain statistically the difference in urease activity and S.salivarius ureC mRNA levels pre- and post-rinse by the following potential predictors: age, gender, caries status, sugar consumption and salivary mutans levels.

Results: Gender (P=0.054) and baseline urease levels (P=0.035) were the factors that most influenced the difference in urease activity in plaque before and after rinsing. Overall, males had lower baseline levels of urease activity in plaque, but experienced the highest level of induction of urease activity following exposure to sugar. Similarly, in saliva, the difference in urease activity and in S. salivarius ureC mRNA was negatively correlated with baseline levels (urease activity: Spearman's rho =-0.56, P=0.012, ureC mRNA: Spearman's rho =-0.664, P=0.013). The response of urease activity to the sucrose rinse did not seem to be significantly associated with age, caries status, sugar consumption or salivary mutans levels in this sample.

Conclusions: The results of this study suggest that a sucrose exposure may have different effects on the induction of urease in the dental plaque and saliva of children depending on the levels of urease they express under resting conditions. These findings support the idea that host factors may strongly influence the expression levels of an enzyme that is absolutely critical for oral biofilm pH homeostasis. Further studies on a larger sample are required to confirm these observations.

Supported by: P20RR11126, DE015285, DE10362, G12RR-03051, R25 RR17589.