Metabolomics Research in Periodontal Disease by Mass Spectrometry

Metabolomics for dental caries diagnosis: Past, present, and future

Dental caries, a prevalent global infectious condition affecting over 95% of adults, remains elusive in its precise etiology. Addressing the complex dynamics of caries demands a thorough exploration of taxonomic, potential, active, and encoded functions within the oral ecosystem. Metabolomic profiling emerges as a crucial tool, offering immediate insights into microecosystem physiology and linking directly to the phenotype. Identified metabolites, indicative of caries status, play a pivotal role in unraveling the metabolic processes underlying the disease. Despite challenges in metabolite variability, the use of metabolomics, particularly via mass spectrometry and nuclear magnetic resonance spectroscopy, holds promise in caries research. This review comprehensively examines metabolomics in caries prevention, diagnosis, and treatment, highlighting distinct metabolite expression patterns and their associations with disease-related bacterial communities. Pioneering in approach, it integrates singular and combinatory metabolomics methodologies, diverse biofluids, and study designs, critically evaluating prior limitations while offering expert insights for future investigations. By synthesizing existing knowledge, this review significantly advances our comprehension of caries, providing a foundation for improved prevention and treatment strategies.

Creatine promotes osteogenic differentiation of dental pulp stem cells via the AMPK-ULK1-autophagy axis

OBJECTIVE

We aimed to demonstrate the effects of creatine (Cr) on osteogenic differentiation (OD) in HDPSCs.

MATERIALS AND METHODS

HDPSCs were treated with Cr and an inhibitor of Cr transporter. The OD capacity was evaluated by detecting ALP staining and activity, alizarin red staining (ARS), as well as osteogenesis-related protein levels. Transcriptomic sequencing, western blotting, transmission electron microscopy, immunofluorescence staining, and autophagy-related protein marker detection were applied to illustrate the underlying mechanism. Furthermore, the impact of Cr on bone regeneration was investigated in vivo.

RESULTS

We found that 1 mm of Cr effectively enhanced the OD of HDPSCs. The creatine group displayed significantly increased AMPK phosphorylation, overexpressed autophagy-related proteins, enhanced OD, and mineralization capabilities. We also found that ULK1 is the downstream molecule through which AMPK induces cellular autophagy. In vivo results demonstrated that Cr could increase the new bone formation of periodontitis.

CONCLUSION

Our research discovered a new AMPK-ULK1-autophagy pathway through which Cr enhances OD in HDPSCs. Cr enhanced HDPSCs-mediated periodontal tissue regeneration in a periodontitis mouse model, providing a theoretical foundation for the study of bone repair in periodontitis.

Recent findings on metabolomics and the microbiome of oral bacteria involved in dental caries and periodontal disease

Periodontal disease is characterized by bacterial toxins within the oral biofilm surrounding the teeth, leading to gingivitis and the gradual dissolution of the alveolar bone, which supports the teeth. Notably, symptoms in the early stages of the disease are often absent. Similarly, dental caries occurs when oral bacteria metabolize dietary sugars, producing acids that dissolve tooth enamel and dentin. These bacteria are commonly present in the oral cavity of most individuals. Metabolomics, a relatively recent addition to the "omics" research landscape, involves the comprehensive analysis of metabolites in vivo to elucidate pathological mechanisms and accelerate drug discovery. Meanwhile, the term "microbiome" refers to the collection of microorganisms within a specific environmental niche or their collective genomes. The human microbiome plays a critical role in health and disease, influencing a wide array of physiological and pathological processes. Recent advances in microbiome research have identified numerous bacteria implicated in dental caries and periodontal disease. Additionally, studies have uncovered various pathogenic factors associated with these microorganisms. This review focuses on recent findings in metabolomics and the microbiome, specifically targeting oral bacteria linked to dental caries and periodontal disease. We acknowledge the limitation of relying exclusively on the MEDLINE database via PubMed, while excluding other sources such as gray literature, conference proceedings, and clinical practice guidelines.

Metabolic Footprint of Treponema phagedenis and Treponema pedis Reveals Potential Interaction Towards Community Succession and Pathogenesis in Bovine Digital Dermatitis

Bovine digital dermatitis (BDD) is a cattle infection causing hoof lesions and lameness, with treponemes as key pathogens. We analyzed the metabolic activity of Treponema phagedenis and Treponema pedis using gas chromatography-mass spectrometry for organic acids (OAs), amino acids (AAs), and fatty acids (FAs), and high-performance liquid chromatography for short-chain fatty acids (SCFAs). Key findings include a 61.5% reduction in pyruvic acid in T. pedis and 81.0% in T. phagedenis. 2-hydroxybutyric acid increased by 493.8% in T. pedis, while succinic acid increased by 31.3%, potentially supporting T. phagedenis. Among AAs, glycine was reduced by 97.4% in T. pedis but increased by 64.1% in T. phagedenis. Proline increased by 76.6% in T. pedis but decreased by 13.6% in T. phagedenis. Methionine and glutamic acid were competitively utilized, with methionine reduced by 41.8% in T. pedis and 11.9% in T. phagedenis. Both species showed significant utilization of palmitic acid (reduced by 82.8% in T. pedis and 87.2% in T. phagedenis). Butyric acid production increased by 620.2% in T. phagedenis, and propionic acid increased by 932.8% in T. pedis and 395.6% in T. phagedenis. These reveal metabolic interactions between the pathogens, contributing to disease progression and offering insights to BDD pathogenesis.

Mass spectrometry-based metabolomics for the investigation of antibiotic-bacterial interactions

With the development of analytical technologies especially mass spectrometry, metabolomics is becoming increasingly hot in the field of studying antibiotic-bacterial interactions. On the one hand, metabolomics can reveal metabolic perturbations in bacteria in the presence of antibiotics and expose metabolic mechanisms. On the other hand, through in-depth analysis of bacterial metabolic profiles, biomarkers and bioactive secondary metabolites with great potential as drug precursors can be discovered. This review focuses on the experimental workflow of bacterial metabolomics and its application to study the interaction between bacteria and antibiotics. Metabolomics improves the understanding of antibiotic lethality, reveals metabolic perturbations in antibiotic-resistant bacteria, guides the diagnosis and antibiotic treatment of infectious diseases, and aids in the exploration of antibacterial metabolites in nature. Furthermore, current limitations and directions for future developments in this area are discussed.

Comparisons of different extraction methods and solvents for saliva samples

INTRODUCTION

Changes in the categories and concentrations of salivary metabolites may be closely related to oral, intestinal or systemic diseases. To study salivary metabolites, the first analytical step is to extract them from saliva samples as much as possible, while reducing interferences to a minimum. Frequently used extraction methods are protein precipitation (PPT), liquid-liquid extraction (LLE) and solid-phase extraction (SPE), with various organic solvents. The types and quantities of metabolites extracted with different methods may vary greatly, but few studies have systematically evaluated them.

OBJECTIVES

This study aimed to select the most suitable methods and solvents for the extraction of saliva according to different analytical targets.

METHODS

An untargeted metabolomics approach based on liquid chromatography-mass spectrometry was applied to obtain the raw data. The numbers of metabolites, repeatability of the data and intensities of mass spectrometry signals were used as evaluation criteria.

RESULTS

PPT resulted in the highest coverage. Among the PPT solvents, acetonitrile displayed the best repeatability and the highest coverage, while acetone resulted in the best signal intensities for the extracted compounds. LLE with the mixture of chloroform and methanol was the most suitable for the extraction of small hydrophobic compounds.

CONCLUSION

PPT with acetonitrile or acetone was recommended for untargeted analysis, while LLE with the mixture of chloroform and methanol was recommended for small hydrophobic compounds.

Circulating Metabolites and Dental Traits: A Mendelian Randomization Study

It is of great importance to uncover causal biomarkers to gain insight into the pathogenesis of oral diseases and identify novel treatment targets for prevention and treatment thereof. This study aimed to systematically evaluate the causal effects of hundreds of metabolites on 10 dental traits using a 2-sample Mendelian randomization (MR) approach. Genetic variants from genome-wide association studies of 309 known metabolites were used as instrumental variables. We selected 10 dental traits, including clinical measures of dental diseases, from the Gene-Lifestyle Interactions in Dental Endpoints Consortium and self-reported oral health data from the UK Biobank. The causal relationships between metabolites and dental traits were inferred using the inverse variance-weighted approach and further controlled for horizontal pleiotropy using 5 additional MR methods. After correcting for multiple tests, 5 metabolites were identified as causal biomarkers. Genetically predicted increased levels of mannose were associated with lower risk of bleeding gums (odds ratio [OR] = 0.72; 95% confidence interval [CI], 0.61-0.85; P = 9.9 × 10-5). MR also indicated 4 metabolites on the causal pathway to dentures, with fructose (OR = 0.50; 95% CI, 0.36-0.70; P = 5.2 × 10-5) and 1-palmitoleoyl-glycerophosphocholine (OR = 0.67; 95% CI, 0.56-0.81; P = 4.8 × 10-5) as potential protective factors and glycine (OR = 1.22; 95% CI, 1.11-1.35; P = 5.6×10-5) and 1,5-anhydroglucitol (OR = 1.32; 95% CI, 1.14-1.52; P = 1.5 × 10-4) as risk factors. The causal associations were robust in various sensitivity analyses. We further observed some shared metabolites among different dental traits, implying similar biological mechanisms underlying the pathogenic processes. Finally, the pathway analysis revealed several significant metabolic pathways that may be involved in the development of dental disorders. Our study provides novel insights into the combination of metabolomics and genomics to reveal the pathogenesis of and therapeutic strategies for dental disorders. It highlighted 5 metabolites and several pathways as causal candidates, warranting further investigation.

Metabolomics analysis in saliva from periodontally healthy, gingivitis and periodontitis patients

OBJECTIVE

The aim of this study was to investigate metabolomics markers in the saliva of patients with periodontal health, gingivitis and periodontitis.

BACKGROUND

The use of metabolomics for diagnosing and monitoring periodontitis is promising. Although several metabolites have been reported to be altered by inflammation, few studies have examined metabolomics in saliva collected from patients with different periodontal phenotypes.

METHODS

Saliva samples collected from a total of 63 patients were analysed by nuclear magnetic resonance (NMR) followed by ELISA for interleukin (IL)-1β. The patient sample, well-characterised clinically, included periodontal health (n = 8), gingivitis (n = 19) and periodontitis (n = 36) cases, all non-smokers and not diabetic.

RESULTS

Periodontal diagnosis (healthy/gingivitis/periodontitis) was not associated with any salivary metabolites in this exploratory study. Periodontal staging showed nominal associations with acetoin (p = .030) and citrulline (p = .047). Among other investigated variables, the use of systemic antibiotics in the previous 3 months was associated with higher values of the amino acids taurine, glycine and ornithine (p = .002, p = .05 and p = .005, respectively, at linear regression adjusted for age, gender, ethnicity, body mass index and staging).

CONCLUSION

While periodontal staging was marginally associated with some salivary metabolites, other factors such as systemic antibiotic use may have a much more profound effect on the microbial metabolites in saliva. Metabolomics in periodontal disease is still an underresearched area that requires further observational studies on large cohorts of patients, aiming to obtain data to be used for clinical translation.

Emerging avenues linking myeloid-derived suppressor cells to periodontal disease

Periodontal disease is one of the most common inflammatory disorders in humans. Gingivitis is the mildest form of periodontal disease and its progression can lead to periodontitis, an inflammatory disease characterized by soft tissue damage that can lead to progressive destruction of the periodontal ligament and alveolar bone. Diverse populations of immune cells are involved in periodontal disease. Myeloid-derived suppressor cells (MDSCs) represent a heterogeneous group of immature myeloid cells derived from hematopoietic precursor cells and exhibit T cell immunosuppressive functions that are thought to be involved in periodontal disease. Therefore, MDSCs have been recently analyzed in the context of this disease. In this review, we discuss the most recent advances in the characterization of the biological aspects, subpopulations, and traffic of MDSCs, as well as their immunosuppressive and osteoclastogenic activity in the context of periodontal disease and in the presence of key periodontal pathogens.