Metabolomic Studies of Oral Biofilm, Oral Cancer, and Beyond.

Jumpei Washio,Nobuhiro Takahashi

doi:10.3390/ijms17060870

Abstract

Oral diseases are known to be closely associated with oral biofilm metabolism, while cancer tissue is reported to possess specific metabolism such as the ‘Warburg effect’. Metabolomics might be a useful method for clarifying the whole metabolic systems that operate in oral biofilm and oral cancer, however, technical limitations have hampered such research. Fortunately, metabolomics techniques have developed rapidly in the past decade, which has helped to solve these difficulties. In vivo metabolomic analyses of the oral biofilm have produced various findings. Some of these findings agreed with the in vitro results obtained in conventional metabolic studies using representative oral bacteria, while others differed markedly from them. Metabolomic analyses of oral cancer tissue not only revealed differences between metabolomic profiles of cancer and normal tissue, but have also suggested a specific metabolic system operates in oral cancer tissue. Saliva contains a variety of metabolites, some of which might be associated with oral or systemic disease; therefore, metabolomics analysis of saliva could be useful for identifying disease-specific biomarkers. Metabolomic analyses of the oral biofilm, oral cancer, and saliva could contribute to the development of accurate diagnostic, techniques, safe and effective treatments, and preventive strategies for oral and systemic diseases.

Highlights

Glucose rinsing resulted in marked changes in the samples’ metabolite profiles. These results indicated for the first time that the main carbon metabolic pathways, such as the EMP pathway, the PP pathway, and the tri-carbonic acid (TCA) cycle (Figure 1), are in operation in the oral biofilm in vivo
xylitol 5-phosphate (X5P) was detected at a significant level only after a rinse with a xylitol-glucose mixture (Table 3), indicating that X5P is produced via a bacterial phosphoenolpyruvate-dependent phosphotransferase system [50,53]
Metabolomic research into the oral biofilm, oral cancer, and saliva is in its early stages, but it has already revealed several novel findings about the properties metabolisms, that is, their physiological functions

Summary

What Is Metabolomics?

Metabolomics is a relatively new form of omics research. Living cells contain many metabolites, which are derived from various metabolic activities. Clinical specimen, such as oral biofilm samples, are too small to be analyzed using this method Due to such technical limitations, previous studies of biofilm metabolism have been based on in vitro techniques involving the culturing of a single bacterium, whereas the oral biofilm is known to be composed of over 500 kinds of bacteria. CE-TOFMS can detect various metabolites and only requires a small sample It can be used for metabolomic research involving clinical specimens, such as oral biofilm samples. Glucose rinsing resulted in marked changes in the samples’ metabolite profiles These results indicated for the first time that the main carbon metabolic pathways, such as the EMP pathway, the PP pathway, and the TCA cycle (Figure 1), are in operation in the oral biofilm in vivo. The metabolite profile in the oral biofilm exhibited similar characteristics to those of Streptococcus and Actinomyces [41,42]

Effects of Fluoride and Xylitol on Metabolism in the Oral Biofilm

Application to Oral Cancer Research

Application to Saliva Samples

Findings

Conclusions and the Future