Free amino acid composition of saliva in patients with healthy periodontium and periodontitis

Metabolomic Profiles of Oral Rinse Samples to Distinguish Severe Periodontitis Patients From Non-Periodontitis Controls

AIMS

To explore the potential of metabolomic profiles of oral rinse samples to distinguish between patients with severe periodontitis (stage III/IV) and non-periodontitis controls. This is coupled to an analysis of differences in metabolomic profiles between individuals without periodontitis, patients with localized periodontitis, and patients with generalized periodontitis.

METHODS

Periodontitis patients and controls were recruited, all aged ≥ 40 years. Study participants were asked to rinse vigorously for 30 s with 10 mL phosphate buffered saline. Metabolites were identified using a semi-targeted liquid chromatography tandem mass spectrometry (LC-MS/MS) platform.

RESULTS

In total, 38 periodontitis patients (18 localized, 20 generalized stage III/IV periodontitis patients) and 16 controls were included. Metabolomic profiles of oral rinse samples were able to distinguish patients with severe periodontitis (stage III/IV) from non-periodontitis controls. Among various variables for the severity of periodontitis, we found that the number of sites with deep pockets (PPD) ≥ 6 mm explained best the differences in metabolomic profiles between controls and patients with severe periodontitis. Subjects with a high number of sites with PPD ≥ 6 mm were characterized by a higher level of phosphorylated nucleotides, amino acids, peptides, and dicarboxylic acids. Metabolomic profiles were also significantly different between controls vs. generalized periodontitis and between localized periodontitis vs. generalized periodontitis (p < 0.05).

CONCLUSION

Our study demonstrates that simply collected oral rinse samples are suitable for LC-MS/MS based metabolomic analysis. We show that a metabolomic profile with a substantial number of metabolites can distinguish severe periodontitis patients from non-periodontitis controls. These observations can be a basis for further studies into screening to identify subjects with the risk of having severe periodontitis.

Involvement of propionate, citrulline, homoserine, and succinate in oral microbiome metabolite-driven periodontal disease progression

Dysbiosis of the oral microbiome has been implicated in the onset and progression of periodontal diseases. An altered oral microbiome can significantly affect the concentration and composition ratio of bacterial-derived metabolites, thereby contributing to disease development. However, there is limited research on the role of metabolites derived from the oral microbiota. This study aimed to identify specific bacteria-derived metabolites and their contributions to pathogenicity. Mouth-rinsed water was collected from 24 patients with periodontal disease and 22 healthy individuals. We conducted a correlation analysis between periodontal disease-associated bacteria and metabolites present in mouth-rinsed water. We evaluated the effects of these metabolites on human gingival epithelial cells analysis of oral bacteria culture supernatants confirmed the origin of these metabolites. We identified 20 metabolites associated with bacteria that are significantly more prevalent in periodontal disease. Notably, propionate, succinate, citrulline, and homoserine-metabolites derived from the oral microbiome-were identified as being associated with periodontal disease. These results suggested that metabolites derived from the oral microbiota are involved in periodontal disease.

Regulation of tryptophan-indole metabolic pathway in Porphyromonas gingivalis virulence and microbiota dysbiosis in periodontitis

Pathogenesis of periodontitis is marked by microbiota dysbiosis and disrupted host responses. Porphyromonas gingivalis is a keystone pathogen of periodontitis which expresses various crucial virulence factors. This study aimed to clarify the role and mechanisms of P. gingivalis tryptophan-indole metabolic pathway in the pathogenesis of periodontitis. This study showed that periodontitis patients exhibited elevated tryptophan metabolism and salivary pathogen abundance. Tryptophanase gene-deficiency altered proteome and metabolome of P. gingivalis, inhibited P. gingivalis virulent factors expression, biofilm growth, hemin utilization, cell adhesion/invasion and pro-inflammation ability. Tryptophan-indole pathway of P. gingivalis stimulated periodontitis biofilm formation and induced oral microbiota dysbiosis. In periodontitis mice, this pathway of P. gingivalis aggravated alveolar bone loss and gingival tissue destruction, causing oral and gut microbiota dysbiosis. This study indicates that the tryptophan-indole pathway serves as a significant regulator of P. gingivalis virulence and oral microbiota dysbiosis, which is also associated with gut dysbiosis.

The role of salivary metabolomics in chronic periodontitis: bridging oral and systemic diseases

BACKGROUND

Chronic periodontitis is a condition impacting approximately 50% of the world's population. As chronic periodontitis progresses, the bacteria in the oral cavity change resulting in new microbial interactions which in turn influence metabolite production. Chronic periodontitis manifests with inflammation of the periodontal tissues, which is progressively developed due to bacterial infection and prolonged bacterial interaction with the host immune response. The bi-directional relationship between periodontitis and systemic diseases has been reported in many previous studies. Traditional diagnostic methods for chronic periodontitis and systemic diseases such as chronic kidney diseases (CKD) have limitations due to their invasiveness, requiring practised individuals for sample collection, frequent blood collection, and long waiting times for the results. More rapid methods are required to detect such systemic diseases, however, the metabolic profiles of the oral cavity first need to be determined.

AIM OF REVIEW

In this review, we explored metabolomics studies that have investigated salivary metabolic profiles associated with chronic periodontitis and systemic illnesses including CKD, oral cancer, Alzheimer's disease, Parkinsons's disease, and diabetes to highlight the most recent methodologies that have been applied in this field.

KEY SCIENTIFIC CONCEPTS OF THE REVIEW

Of the rapid, high throughput techniques for metabolite profiling, Nuclear magnetic resonance (NMR) spectroscopy was the most applied technique, followed by liquid chromatography-mass spectrometry (LC-MS) and gas chromatography-mass spectrometry (GC-MS). Furthermore, Raman spectroscopy was the most used vibrational spectroscopic technique for comparison of the saliva from periodontitis patients to healthy individuals, whilst Fourier Transform Infra-Red Spectroscopy (FT-IR) was not utilised as much in this field. A recommendation for cultivating periodontal bacteria in a synthetic medium designed to replicate the conditions and composition of saliva in the oral environment is suggested to facilitate the identification of their metabolites. This approach is instrumental in assessing the potential of these metabolites as biomarkers for systemic illnesses.

Unveiling the consequences of early human saliva contamination on membranes for guided bone regeneration

AIMS

GBR membranes have various surface properties designed to elicit positive responses in regenerative clinical procedures; dental clinicians attempt to employ techniques to prevent the direct interaction of contaminated oral fluids with these biomaterials. However, saliva is uninterruptedly exhibited in oral surgical procedures applying GBR membranes, suggesting a persistent interaction with biomaterials and the surrounding oral tissues. This fundamental study aimed to investigate potential alterations in the physical, chemical, and key biological properties of membranes for guided bone regeneration (GBR) caused by isolated early interaction with human saliva.

METHODS

A reproducible step-by-step protocol for collecting and interacting human saliva with membranes was developed. Subsequently, membranes were evaluated for their physicochemical properties, protein quantification, DNA, and 16S rRNA levels viability of two different cell lines at 1 and 7 days, and ALP activity. Non-interacted membranes and pure saliva of donors were applied as controls.

RESULTS

Qualitative morphological alterations were noticed; DNA extraction and 16S quantification revealed significantly higher values. Furthermore, the viability of HGF-1 and MC3T3-E1 cells was significantly (p < .05) reduced following saliva interaction with biodegradable membranes. Saliva contamination did not prejudice PTFE membranes significantly in any biological assay.

CONCLUSIONS

These outcomes demonstrated a susceptible response of biodegradable membranes to isolated early human saliva interaction, suggesting impairment of structural morphology, reduced viability to HGF-1 and MC3T3-E1, and higher absorption/adherence of DNA/16S rRNA. As a result, clinical oral procedures may need corresponding refinements.

Saliva metabolomics: concepts and applications in oral disorders

OBJECTIVES

The purpose of this review was to present the basic concepts of metabolomics methodology and the use of saliva for diagnostic, prognostic, and predictive strategies.

MATERIAL AND METHODS

This review followed the focus in: "saliva metabolomics" and "oral diseases". The authors searched studies on PubMed database. The inclusion criteria were original studies and reviews that assessed metabolomics techniques. A descriptive analysis was performed considering the study design, approach system, clinical steps, and tools for the determination of profile or biomarkers metabolites, and the advantages and disadvantages.

RESULTS

Metabolomic analyses use a combination of analytical instrumentation and informatic tools to provide information on metabolite characteristics. In this review we described different technologies applied and the advantages and limitations of each technique. Furthermore, in the literature search, we retrieved 25 studies that investigated saliva metabolites in oral diseases: 8 studies used targeted analysis and 17 untargeted metabolomics approaches. Most studies included patients with periodontal diseases, oral squamous cell carcinoma, and Sjögren Syndrome. The most frequently reported metabolites were glycine, leucine, phenylalanine, dipeptides, linoleic acid, arachidonic acid, tyrosine, choline, taurine, lactate, valine, and proline.

CONCLUSIONS

Metabolomics analysis has emerged as a powerful tool for tumor diagnosis and to enhance tumor classification, including salivary gland tumors (SGTs). It also holds promise for developing personalized treatment plans and defining more precise prognostic categories.

CLINICAL RELEVANCE

Metabolomics is the most functional and comprehensive technique for monitoring and understanding gene functions and identifying the biochemical state of an organism in response to genetic and environmental changes.

Glutamate is a key nutrient for Porphyromonas gingivalis growth and survival during intracellular autophagic life under nutritionally limited conditions

Porphyromonas gingivalis survives in special autophagic vacuoles that serve as major replicative habitats in human primary gingival epithelial cells (GECs). As an asaccharolytic strict anaerobe, P. gingivalis is dependent on amino acids and peptides for nutrient sources. However, it is largely unknown as to P. gingivalis' metabolic processing under the nutritionally limited intracellular environments such the vacuoles, especially the preferred amino acids and associated-metabolic machineries. Here we elucidate that a Glutamate (Glu) catabolic enzyme, glutamate dehydrogenase (GdhA) is highly enriched in the isolated P. gingivalis -containing vacuoles. Interestingly, we found that P. gingivalis induces conversion of intracellular glutamine pool to Glu determined by analyses of the P. gingivalis- containing vacuoles and the whole infected-GECs. Critically, exogenous Glu-Glu dipeptide, a simple precursor of Glu, significantly increases the size of isolated intact P. gingivalis containing-vacuoles and live wild-type P. gingivalis numbers in GECs. In contrast, the isogenic GdhA-deficient-strain, Δ gdhA displayed a significant growth defect with collapsed-vacuoles in GECs. Next, we confirmed that P. gingivalis uptakes 14 C-Glu and it preferentially utilizes Glu-Glu-dipeptide using a nutritionally reduced Tryptic-Soy-Broth (TSB) media supplemented with Glu-Glu. Contrary, Δ gdhA -strain showed no detectable growth especially in nutritionally reduced TSB media with Glu-Glu. Using Atomic-Force-Microscopy, we observed that, wild-type P. gingivalis but not Δ gdhA strain notably increased the cell volume upon Glu-Glu supplementation, an indicator of higher metabolism and growth. Utilization of a human gingiva-mimicking organoid-system further validated the importance of Glu as an essential nutrient for the intramucosal colonization of P. gingivalis via the protected replicative vacuoles in GECs.

Importance

This study reveals that P. gingivalis heavily depends on preferential utilization of Glutamate (Glu) for autophagic vacuolar growth and survival in human GECs. Several novel observations are made to support this: (i) GdhA of P. gingivalis is highly enriched in these vacuoles, (ii) P. gingivalis induces a large conversion of intracellular glutamine to Glu, (iii) size of vacuoles are significantly increased in the presence of Glu-Glu in P. gingivalis wild-type strain infection which is opposite in a Δ gdhA strain, (iv) P. gingivalis uptakes 14 C-Glu and preferentially utilizes Glu-Glu dipeptide, (v) similarly, wild-type strain shows growth increase in a nutritionally reduced bacterial culture media, and (vi) finally, Glu-Glu supplementation increases bacterial cell-volume of P. gingivalis wild-type but not Δ gdhA strain, an indicator of higher metabolism and growth. Taken together, this study highlights the pathophysiological importance of Glu for P. gingivalis growth-rate, biomass induction and survival in nutritionally limited host subcellular environments.

High-Throughput Combined Analysis of Saliva Microbiota and Metabolomic Profile in Chinese Periodontitis Patients: A Pilot Study

The onset and progression of periodontitis involves complicated interactions between the dysbiotic oral microbiota and disrupted host immune-inflammatory response, which can be mirrored by the changes in salivary metabolites profile. This pilot study sought to examine the saliva microbiome and metabolome in the Chinese population by the combined approach of 16s rRNA sequencing and high-throughput targeted metabolomics to discover potential cues for host-microbe metabolic interactions. Unstimulated whole saliva samples were collected from eighteen Stage III and IV periodontitis patients and thirteen healthy subjects. Full-mouth periodontal parameters were recorded. The taxonomic composition of microbiota was obtained by 16s rRNA sequencing, and the metabolites were identified and measured by ultra-high performance liquid chromatography and mass spectrometry-based metabolomic analysis. The oral microbiota composition displayed marked changes where the abundance of 93 microbial taxa differed significantly between the periodontitis and healthy group. Targeted metabolomics identified 103 differential metabolites between the patients and healthy individuals. Functional enrichment analysis demonstrated the upregulation of protein digestion and absorption, histidine metabolism, and nicotinate and nicotinamide metabolism pathways in the dysbiotic microbiota, while the ferroptosis, tryptophan metabolism, glutathione metabolism, and carbon metabolism pathways were upregulated in the patients. Correlation analysis confirmed positive relationships between the clinical parameters, pathogen abundances, and disease-related metabolite levels. The integral analysis of the saliva microbiome and metabolome yielded an accurate presentation of the dysbiotic oral microbiome and functional alterations in host-microbe metabolism. The microbial and metabolic profiling of the saliva could be a potential tool in the diagnosis, prognosis evaluation, and pathogenesis study of periodontitis.

Engineering the Signal Resolution of a Paper-Based Cell-Free Glutamine Biosensor with Genetic Engineering, Metabolic Engineering, and Process Optimization

Specialized cancer treatments have the potential to exploit glutamine dependence to increase patient survival rates. Glutamine diagnostics capable of tracking a patient's response to treatment would enable a personalized treatment dosage to optimize the tradeoff between treatment success and dangerous side effects. Current clinical glutamine testing requires sophisticated and expensive lab-based tests, which are not broadly available on a frequent, individualized basis. To address the need for a low-cost, portable glutamine diagnostic, this work engineers a cell-free glutamine biosensor to overcome assay background and signal-to-noise limitations evident in previously reported studies. The findings from this work culminate in the development of a shelf-stable, paper-based, colorimetric glutamine test with a high signal strength and a high signal-to-background ratio for dramatically improved signal resolution. While the engineered glutamine test is important progress towards improving the management of cancer and other health conditions, this work also expands the assay development field of the promising cell-free biosensing platform, which can facilitate the low-cost detection of a broad variety of target molecules with high clinical value.

Sirtuin6 and Lipoxin A4 levels are decreased in severe periodontitis

OBJECTIVE

Sirtuin6 plays an important role in the regulation of inflammation, homeostasis, and apoptosis, and it has anti-inflammatory effects on several diseases. Lipoxin A4 is a pro-resolving lipid mediator of inflammation and inhibits hypoxia-induced apoptosis and oxidative stress. Considering that Lipoxin A4 and Sirtuin6 have protective effects on inflammatory diseases, the aim of this study is to determine the possible roles of these molecules on periodontitis inflammation in saliva and serum and to reveal the relationship of these data with clinical periodontal parameters.

MATERIAL AND METHODS

A total of 20 stage III/grade B periodontitis and 20 periodontally healthy subjects were included in this cross-sectional study (all never smokers and systemically healthy). Clinical periodontal parameters (plaque index, probing pocket depth, bleeding on probing, clinical attachment loss) were recorded. Saliva and serum levels of Sirtuin6 and Lipoxin A4 were analyzed by enzyme-linked immunosorbent assay.

RESULTS

Serum Sirtuin6 and saliva Lipoxin A4 levels were significantly lower in the periodontitis group than the control group (respectively, p = 0.0098, p = 0.0008). There were negative correlations between all periodontal clinical parameters and saliva Lipoxin A4 level (p < 0.05) and between probing pocket depth, clinical attachment loss, and serum and saliva Sirtuin6 levels (respectively, r =  - 0.465 and r =  - 0.473, p < 0.05).

CONCLUSIONS

Decreased levels of serum Sirtuin6 and saliva Lipoxin A4 in periodontitis patients and their correlation with clinical periodontal parameters suggest that serum Sirtuin6 and saliva Lipoxin A4 may be related with periodontal inflammation.

CLINICAL RELEVANCE

Scientific rationale for the study: Sirtuin6 is one of seven members of the family of NAD + dependent protein that played an important role in the regulation of inflammation, energy metabolism, homeostasis, and apoptosis. Sirtuin6 is associated with the pathogenesis of several diseases. Lipoxin A4 is a lipid mediator that inhibits hypoxia-induced apoptosis and oxidative stress, and it has an active role in the resolution of periodontal inflammation. No studies that investigated the potential role Sirtuin6 and its relationship with inflammation resolution and apoptosis mechanisms in severe periodontitis patients.

PRINCIPAL FINDINGS

the serum Sirtuin6 and saliva Lipoxin A4 levels were significantly lower and negatively correlated with clinical periodontal parameters in the patients with periodontitis than the healthy controls.

PRACTICAL IMPLICATIONS

this study shows that serum Sirtuin6 and saliva Lipoxin A4 may be candidate biomarkers related with periodontal inflammation and estimating to periodontal status.

CLINICAL TRIAL REGISTRATION

NCT05417061.

Does smoking influence tryptophan metabolism in periodontal inflammation? A cross-sectional study

OBJECTIVES

The aim of this study was to identify the effects of smoking and periodontal inflammation on tryptophan-kynurenine metabolism as well as the correlation between these findings and clinical periodontal parameters.

BACKGROUND

It has been shown that the tryptophan amino acid's primary catabolic pathway, the kynurenine pathway (KP), may serve as a key biomarker for periodontal disease. Although there are studies investigating the effect of smoking on KYN-TRP metabolism, the effect of smoking on periodontal disease through KP has not been revealed so far.

METHODS

The salivary and serum samples were gathered from 24 nonsmoker (NS-P) stage III, grade B generalized periodontitis and 22 smoker (S-P) stage III, grade C generalized periodontitis patients, in addition to 24 nonsmoker (NS-C) and 24 smoker (S-C) periodontally healthy control individuals. Saliva and serum IL-6, kynurenine (KYN), and tryptophan (TRP) values, and KYN/TRP ratio were analyzed by liquid chromatography-mass spectrometry. Clinical periodontal measurements were recorded.

RESULTS

Salivary TRP values were significantly higher in both periodontitis groups than control groups (p < .05). Salivary KYN values were highest in NS-P group (p < .05). Salivary KYN values did not differ significantly between periodontitis groups (p = .84). Salivary KYN/TRP ratio was significantly lower in NS-P group compared to other groups (p < .001). Serum TRP value is higher in S-P group than other groups; however, significant difference was found in S-C group (p < .05). Serum KYN values were significantly lower in smokers than nonsmokers. Serum KYN/TRP ratio is higher in NS-P group. NS-P group has the highest salivary IL-6 levels, NS-C group has the lowest values (p < .05).

CONCLUSIONS

Our results point out that smoking exacerbates inflammation in the periodontium and increases TRP destruction and decreases IDO activity by suppressing KP in serum. As a result, kynurenine and its metabolites may be significant biomarkers in the link between smoking and periodontal disease.

The increasing importance of the oral microbiome in periodontal health and disease

Herein, the aim is to discuss the current knowledge of microbiome and periodontal diseases. Current treatment strategies include mechanical therapy such as root planing, scaling, deep pocket debridement and antimicrobial chemotherapy as an adjuvant therapy. Among promising therapeutic strategies, dental probiotics and oral microbiome transplantation have gained attention, and may be used to treat bacterial imbalances by competing with pathogenic bacteria for nutrients and adhesion surfaces, as well as probiotics targeting the gut microbiome. Development of strategies to prevent and treat periodontal diseases are warranted as both are highly prevalent and can affect human health. Further studies are necessary to better comprehend the microbiome in order to develop innovative preventative measures as well as efficacious therapies against periodontal diseases.

Asymmetric and symmetric dimethylarginine gingival crevicular fluid levels in periodontitis

OBJECTIVE

This study aimed to evaluate the level of ADMA (asymmetric dimethylarginine), SDMA (symmetric dimethylarginine), and IL-1β (Interleukin-1β) in gingival crevicular fluid (GCF) from periodontitis patients and control subjects.

BACKGROUND

ADMA and SDMA are potentially hazardous non-proteinogenic amino acids that limit nitric oxide (NO) synthesis and have many functions in various human disorders. ADMA causes a structural change in nitric oxide synthase, while SDMA blocks arginine cell uptake. Increased plasma ADMA has been widely recognized as a "trigger" initiating impaired NO bioavailability and vascular dysfunction, which ultimately leads to oxidative stress.

METHODS

Twenty-five patients with periodontitis (P) (Stage III, Grade C, n = 25) and 20 control (C) subjects were included in the study. The IL-1β level of GCF was measured by enzyme immunoassay (ELISA) and ADMA and SDMA by liquid chromatography-mass spectrometry (LC-MS/MS).

RESULTS

Periodontitis patients had higher clinical parameters than controls (p < .001). Levels of IL-1β, ADMA and SDMA GCF were statistically significantly higher in group P than in group C (respectively; p = .003, p < .0001, p < .0001). There was no difference in the ADMA/SDMA ratio (p = .312) between the groups. There were significant positive correlations between clinical periodontal parameters and IL-1β, ADMA, and SDMA levels (p < .05). ADMA and SDMA levels were significantly correlated with IL-1β (p < .05).

CONCLUSIONS

These findings suggest that ADMA and SDMA may be involved in the pathogenesis of the periodontal disease.

Salivary irisin level is higher and related with interleukin-6 in generalized periodontitis

OBJECTIVES

Irisin plays an important role in energy homeostasis, inflammation, glucose, and lipid metabolism, and it is shown to have relations with many inflammatory diseases. The aim of the study was to determine saliva and serum irisin and IL-6 levels in patients with stage III/grade B periodontitis compared with individuals with healthy periodontium.

MATERIALS AND METHODS

Twenty patients with stage III grade B periodontitis (P) and 20 periodontally healthy subjects (control; C) were included in this study. Clinical periodontal measurements were recorded. Saliva and serum levels of irisin and interleukin-6 (IL-6) were analyzed by enzyme-linked immunosorbent assay.

RESULTS

Salivary irisin and IL-6 levels were significantly higher in the periodontitis group (p < 0.001, p = 0.002, respectively). Furthermore, serum IL-6 levels were found significantly higher in the periodontitis group compared with controls (p = 0.011). There was no significant difference between the periodontitis and control for serum irisin levels (p > 0.05). Significant positive correlations were found between all periodontal parameters and salivary irisin and IL-6 (p < 0.05) and also between BMI and saliva and serum IL-6 (respectively; r = 0.530, r = 0.329, p < 0.05). There was a positive correlation between salivary irisin and IL-6 (r = 0.369, p < 0.05).

CONCLUSIONS

Monitoring of salivary irisin and IL-6 might be potential biomarker for predicting the susceptibility to periodontitis.

CLINICAL RELEVANCE

Scientific rationale for the study: Irisin is a novel adipomyokine that has played an important role in energy homeostasis, glucose and lipid metabolism, angiogenesis, immunity, and inflammation. Irisin is involved in the pathogenesis of diseases affecting many body systems. IL-6, another adipomyokine, is a major inflammatory mediator and homeostatic regulator of glucose and lipid metabolism and is associated with periodontitis. No studies investigated the relationship between advanced periodontal disease, irisin, and IL-6 together.

PRINCIPAL FINDINGS

The salivary irisin and IL-6 levels were significantly higher and positively correlated in patients with periodontitis relative to healthy controls. Furthermore, serum IL-6 levels were significantly increased in patients with periodontitis.

PRACTICAL IMPLICATIONS

The study shows that irisin and IL-6 can be candidate salivary biomarkers for periodontitis and predict to periodontal status.

Identification of Nutritional Factors to Evaluate Periodontal Clinical Parameters in Patients with Systemic Diseases

Nutritional factors reflect the periodontal parameters accompanying periodontal status. In this study, the associations between nutritional factors, blood biochemical items, and clinical parameters were examined in patients with systemic diseases. The study participants were 94 patients with heart disease, dyslipidemia, kidney disease, or diabetes mellitus. Weak negative correlation coefficients were found between nine clinical parameters and ten nutritional factors. Stage, grade, mean probing depth (PD), rate of PD 4−5 mm, rate of PD ≥ 6 mm, mean clinical attachment level (CAL), and the bleeding on probing (BOP) rate were weakly correlated with various nutritional factors. The clinical parameters with coefficients of determinations (R2) > 0.1 were grade, number of teeth, PD, rate of PD 4−5 mm, CAL, and BOP rate. PD was explained by yogurt and cabbage with statistically significant standardized partial regression coefficients (yogurt: −0.2143; cabbage and napa cabbage: −0.2724). The mean CAL was explained by pork, beef, mutton, and dark green vegetables with statistically significant standardized partial regression coefficients (−0.2237 for pork, beef, and mutton; −0.2667 for dark green vegetables). These results raise the possibility that the frequency of intake of various vegetables can be used to evaluate periodontal stabilization in patients with systemic diseases.

Serum, saliva, and gingival tissue human β-defensin levels in relation to retinoic acid use

BACKGROUND

Retinoic acid is an active derivative of vitamin A and regulates the differentiation, proliferation, and antimicrobial peptide expression profiles of human cells. The aim of the present study was to analyze the effect of systemic retinoic acid use on serum, saliva, and gingival tissue levels of human β-defensin (hBD)-1, hBD-2, and hBD-3.

METHODS

A total of 69 participants (34 systemic retinoic acid users and 35 healthy controls) were enrolled in this study. Plaque index, probing pocket depth, bleeding on probing (BOP), and clinical attachment loss were measured. Saliva and serum hBD-1, hBD-2, and hBD-3 levels were quantified by enzyme-linked immunosorbent assay. Gingival tissue hBD-1, hBD-2, and hBD-3 levels were determined by immunohistochemistry. A univariate general linear model was used in adjusted comparisons of hBD1, hBD-2, and hBD-3. P values of < 0.05 were considered statistically significant.

RESULTS

Reduced salivary levels of hBD-2 (P = 0.042), but not hBD-1 or hBD-3, were detected in systemic retinoic acid users compared to non-user controls. There was a significant difference in the adjusted (for BOP%) salivary hBD-2 concentrations between retinoic acid and control groups (P = 0.031). No difference was observed in serum or tissue levels of hBD-1, hBD-2, or hBD-3 between the two study groups.

CONCLUSION

Systemic retinoic acid use was associated with suppressed salivary hBD-2 level, which was independent of gingival inflammation.

KEY FINDINGS

Systemic retinoic acid use associates with suppressed salivary hBD-2 levels.

Osteoporosis and Alveolar Bone Health in Periodontitis Niche: A Predisposing Factors-Centered Review

Periodontitis is a periodontal inflammatory condition that results from disrupted periodontal host-microbe homeostasis, manifested by the destruction of tooth-supporting structures, especially inflammatory alveolar bone loss. Osteoporosis is characterized by systemic deterioration of bone mass and microarchitecture. The roles of many systemic factors have been identified in the pathogenesis of osteoporosis, including endocrine change, metabolic disorders, health-impaired behaviors and mental stress. The prevalence rate of osteoporotic fracture is in sustained elevation in the past decades. Recent studies suggest that individuals with concomitant osteoporosis are more vulnerable to periodontal impairment. Current reviews of worse periodontal status in the context of osteoporosis are limited, mainly centering on the impacts of menopausal and diabetic osteoporosis on periodontitis. Herein, this review article makes an effort to provide a comprehensive view of the relationship between osteoporosis and periodontitis, with a focus on clarifying how those risk factors in osteoporotic populations modify the alveolar bone homeostasis in the periodontitis niche.

Protein Intake and Oral Health in Older Adults-A Narrative Review

Oral health is vital to general health and well-being for all ages, and as with other chronic conditions, oral health problems increase with age. There is a bi-directional link between nutrition and oral health, in that nutrition affects the health of oral tissues and saliva, and the health of the mouth may affect the foods consumed. Evidence suggests that a healthy diet generally has a positive impact on oral health in older adults. Although studies examining the direct link between oral health and protein intake in older adults are limited, some have explored the relationship via malnutrition, which is also prevalent among older adults. Protein-energy malnutrition (PEM) may be associated with poor oral health, dental caries, enamel hypoplasia, and salivary gland atrophy. This narrative review presents the theoretical evidence on the impact of dietary protein and amino acid composition on oral health, and their combined impact on overall health in older adults.

Influence of periodontal inflammation on tryptophan-kynurenine metabolism: a cross-sectional study

OBJECTIVES

Kynurenine pathway (KP) is the primary way of degrading tryptophan (TRP) and generates several bioactive metabolites (such as kynurenine (KYN), kynurenic acid (KYNA), 3-hydroxykynurenine (3OHKYN)) to regulate biological processes that include host-microbiome signaling and immune cell response. This study is aimed to determine the relationship between periodontal inflammation and tryptophan-kynurenine metabolism and identify their association with periodontal clinical parameters.

MATERIALS AND METHODS

Saliva and serum samples were collected from 20 stage III, grade B generalized periodontitis patients, and 20 periodontally healthy control individuals. Samples were analyzed for IL-6, KYN, TRP, KYN/TRP ratio, KYNA, 3OHKYN, picolinic acid (PA), and quinolinic acid (QA) by liquid chromatography-mass spectrometry. Clinical periodontal parameters (plaque index (PI), probing pocket depth (PPD), gingival recession (GR), clinical attachment loss (CAL), and bleeding on probing (BOP)) were recorded.

RESULTS

Clinical parameters were significantly higher in the periodontitis group (p < 0.001). Salivary IL-6, TRP, KYN, KYNA, PA, and QA levels were significantly higher and KYN/TRP ratio was significantly lower in periodontitis group than control group (p < 0.05). Serum KYN, KYN/TRP ratio and PA levels were significantly higher in periodontitis group than control group (p < 0.05). PPD, BOP, PI, and CAL had significantly positive correlations with salivary IL-6, TRP, PA, QA, and serum KYN and significantly negative correlations with salivary KYN/TRP ratio.

CONCLUSIONS

Our results suggest that periodontal inflammation plays a role in local and systemic tryptophan-kynurenine metabolism.

CLINICAL RELEVANCE

Due to their effects on the immune and inflammatory systems, kynurenines may be potential agents for diagnosis and treatment of periodontal diseases.

HPLC method with post-column derivatization for the analysis of endogenous histidine in human saliva validated using the total-error concept

Histidine (His) is an essential amino acid that plays an important biological role and associated with various pathological conditions. A simple and reliable method for the determination of endogenous histidine in human saliva was optimized and validated. The analyte was separated from the saliva matrix by cation exchange chromatography and detected fluorimetrically (λ_ex/λ_em = 360/440 nm) after online, specific post-column derivatization (PCD) reaction with o-phthalaldehyde. The chemical and instrumental variables of the post-column reaction were optimized using Box-Behnken experimental design to achieve maximum sensitivity. Method validation was carried out employing the total-error concept. Histidine could be analyzed reliably in the range of 0.5-5.0 μΜ, with an LOD (S/N = 3) of 50 nM. Monte Carlo simulations and capability analysis were used to investigate the ruggedness of the PCD reaction. The sampling strategy, sample preparation and stability were also investigated. Seventeen saliva samples were successfully analyzed with histidine levels being in the range of 2.7-19.5 μΜ.

Highly sensitive novel fluorescent chiral probe possessing (S)-2-methylproline structures for the determination of chiral amino compounds by ultra-performance liquid chromatography with fluorescence: An application in the saliva of healthy volunteer

We developed a novel fluorescent chiral probe, DBD-trans-2-methyl-L-proline (DBD-M-Pro), which can be used to target recognition of amino functional groups using chiral resolution. To investigate the chiral resolution efficiency, 20 chiral amino enantiomers (19 DL-amino acids and phenylethylamine) were labeled using ultra-performance liquid chromatography (UPLC) with a fluorescence (FL) system. Diastereomers were formed by the reactions of DBD-M-Pro with enantiomers of amino functional groups at 60 °C for 60 min and detected on a BEH C18 column (100 × 2.1 mm, 1.7 μm). Gradient elution of 10 mM ammonium acetate with 0.05% formic acid (FA) aqueous solution and 0.1% FA acetonitrile or 0.1% FA methanol solution was performed at an excitation wavelength (Ex) 460 nm and emission wavelength (Em) 550 nm. Each resulting derivative of D- and L- type was effectively separated. The results showed that the resolution (Rs) of 17 amino acids and phenylethylamine (PEA) in the range of 1.59-24.11, except for histidine (His) (Rs = 1.32) and serine (Ser) (Rs = 1.47), achieved completely separation. The DBD-M-Pro chiral probe has a robust chiral selectivity for D-amino acids. Furthermore, a new method for the simultaneous determination of six DL-amino acids (Pro, Val, Trp, Phe, Leu, Lys) in human saliva was developed. The proposed method showed resolution values of 1.78-16.38, and an excellent linear relationship was obtained in the range of 2.5-500 pmol (R² ≥ 0.9990). The limit of detection (S/N = 3) ranged from 0.5 to 3.75 pmol. The intra-day and inter-day coefficient of variation (CV) were within the range of 1.75-11.73%. The average addition recoveries in saliva ranged from 95.99 to 106.97%. The methodology was used to determine the content of DL-amino acids and the D/L-amino acid ratio in the saliva of 40 healthy volunteers (15 males and 25 females), as well as evaluating the differences between men and women. Our study suggests that the DBD-M-Pro chiral probe could be an effective tool for screening potential D-amino acid biomarkers in disease.

Wearable wristband-based electrochemical sensor for the detection of phenylalanine in biofluids

Wearable electrochemical sensors are driven by the user-friendly capability of on-site detection of key biomarkers for health management. Despite the advances in biomolecule monitoring such as glucose, still, several unmet clinical challenges need to be addressed. For example, patients suffering from phenylketonuria (PKU) should be able to monitor their phenylalanine (PHE) level in a rapid, decentralized, and affordable manner to avoid high levels of PHE in the body which can lead to a profound and irreversible mental disability. Herein, we report a wearable wristband electrochemical sensor for the monitoring of PHE tackling the necessity of controlling PHE levels in PHE hydroxylase deficiency patients. The proposed electrochemical sensor is based on a screen-printed electrode (SPE) modified with a membrane consisting of Nafion, to avoid interferences in biofluids. The membrane also consists of sodium 1,2-naphthoquinone-4-sulphonate for the in situ derivatization of PHE into an electroactive product, allowing its electrochemical oxidation at the surface of the SPE in alkaline conditions. Importantly, the electrochemical sensor is integrated into a wristband configuration to enhance user interaction and engage the patient with PHE self-monitoring. Besides, a paper-based sampling strategy is designed to alkalinize the real sample without the need for sample pretreatment, and thus simplify the analytical process. Finally, the wearable device is tested for the determination of PHE in saliva and blood serum. The proposed wristband-based sensor is expected to impact the PKU self-monitoring, facilitating the daily lives of PKU patients toward optimal therapy and disease management.