Harsh M. Trivedi

Acceleration of Purine Degradation by Periodontal Diseases

Periodontal diseases, such as gingivitis and periodontitis, are characterized by bacterial plaque accumulation around the gingival crevice and the subsequent inflammation and destruction of host tissues. To test the hypothesis that cellular metabolism is altered as a result of host-bacteria interaction, we performed an unbiased metabolomic profiling of gingival crevicular fluid (GCF) collected from healthy, gingivitis, and periodontitis sites in humans, by liquid and gas chromatography mass spectrometry. The purine degradation pathway, a major biochemical source for reactive oxygen species (ROS) production, was significantly accelerated at the disease sites. This suggests that periodontal-disease-induced oxidative stress and inflammation are mediated through this pathway. The complex host-bacterial interaction was further highlighted by depletion of anti-oxidants, degradation of host cellular components, and accumulation of bacterial products in GCF. These findings provide new mechanistic insights and a panel of comprehensive biomarkers for periodontal disease progression.

Metabolomics Reveals Elevated Macromolecular Degradation in Periodontal Disease

Periodontitis is a chronic inflammatory disease characterized by tissue destruction. In the diseased oral environment, saliva has primarily been considered to act as a protectant by lubricating the tissue, mineralizing the bones, neutralizing the pH, and combating microbes. To understand the metabolic role that saliva plays in the diseased state, we performed untargeted metabolomic profiling of saliva from healthy and periodontitic individuals. Several classes of biochemicals, including dipeptide, amino acid, carbohydrate, lipids, and nucleotide metabolites, were altered, consistent with increased macromolecular degradation of proteins, triacylglycerol, glycerolphospholipids, polysaccharides, and polynucleotides in the individuals with periodontal disease. These changes partially reflected the enhanced host-bacterial interactions in the diseased state as supported by increased levels of bacterially modified amino acids and creatine metabolite. More importantly, the increased lipase, protease, and glycosidase activities associated with periodontitis generated a more favorable energy environment for oral bacteria, potentially exacerbating the disease state.

Global Metabolomic Analysis of Human Saliva and Plasma from Healthy and Diabetic Subjects, with and without Periodontal Disease

Recent studies suggest that periodontal disease and type 2 diabetes mellitus are bi-directionally associated. Identification of a molecular signature for periodontitis using unbiased metabolic profiling could allow identification of biomarkers to assist in the diagnosis and monitoring of both diabetes and periodontal disease. This cross-sectional study identified plasma and salivary metabolic products associated with periodontitis and/or diabetes in order to discover biomarkers that may differentiate or demonstrate an interaction of these diseases. Saliva and plasma samples were analyzed from 161 diabetic and non-diabetic human subjects with a healthy periodontium, gingivitis and periodontitis. Metabolite profiling was performed using Metabolons platform technology. A total of 772 metabolites were found in plasma and 475 in saliva. Diabetics had significantly higher levels of glucose and α-hydroxybutyrate, the established markers of diabetes, for all periodontal groups of subjects. Comparison of healthy, gingivitis and periodontitis saliva samples within the non-diabetic group confirmed findings from previous studies that included increased levels of markers of cellular energetic stress, increased purine degradation and glutathione metabolism through increased levels of oxidized glutathione and cysteine-glutathione disulfide, markers of oxidative stress, including increased purine degradation metabolites (e.g. guanosine and inosine), increased amino acid levels suggesting protein degradation, and increased ω-3 (docosapentaenoate) and ω-6 fatty acid (linoleate and arachidonate) signatures. Differences in saliva between diabetic and non-diabetic cohorts showed altered signatures of carbohydrate, lipid and oxidative stress exist in the diabetic samples. Global untargeted metabolic profiling of human saliva in diabetics replicated the metabolite signature of periodontal disease progression in non-diabetic patients and revealed unique metabolic signatures associated with periodontal disease in diabetics. The metabolites identified in this study that discriminated the periodontal groups may be useful for developing diagnostics and therapeutics tailored to the diabetic population.

Assessment of the effects of dentifrice on periodontal disease biomarkers in gingival crevicular fluid.

BACKGROUND Periodontal disease has been studied primarily from clinical outcomes in lengthy human studies. Comprehensive biochemical profiling (metabolomics) has become a powerful tool for disease characterization and biomarker discovery. In a previous study, we performed a metabolomic analysis of gingival crevicular fluid collected from healthy, gingivitis, and periodontitis sites. Many metabolites associated with inflammation, oxidative stress, tissue degradation, and bacterial metabolism were found to be significantly induced by the diseases. METHODS A panel of 10 markers was selected from the previous metabolomic study based on their statistical significance. Thirty-nine chronic periodontitis subjects were randomly assigned to a toothpaste regimen: control dentifrice (n = 21) or triclosan-containing dentifrice ([CT] n = 18). Subjects were instructed to use their assigned dentifrice twice daily for 6 weeks. Gingival crevicular fluid samples from six healthy, six gingivitis, and three periodontitis sites were collected from each subject at baseline, 1 week, and 6 weeks. The relative levels of the markers in the samples were determined by mass spectrometry. One-sided matched-paired t tests were performed to compare data from healthy, gingivitis, and periodontitis sites. RESULTS Statistical analysis indicates that CT significantly decreased the levels of inosine, lysine, putrescine, and xanthine at the gingivitis sites as early as week 1. In contrast, control dentifrice had little effect. CONCLUSIONS This result provides biochemical confirmation for the therapeutic effects of CT on gingivitis. Biomarkers were significantly altered by CT before clinical changes were observed, suggesting that the markers have predicative value for disease state assessment.