Periodontitis induced by Porphyromonas gingivalis drives periodontal microbiota dysbiosis and insulin resistance via an impaired adaptive immune response

Leaky Gum: The Revisited Origin of Systemic Diseases

The oral cavity is the gateway for microorganisms into your body where they disseminate not only to the directly connected respiratory and digestive tracts but also to the many remote organs. Oral microbiota, travelling to the end of the intestine and circulating in our bodies through blood vessels, not only affect a gut microbiome profile but also lead to many systemic diseases. By gathering information accumulated from the era of focal infection theory to the age of revolution in microbiome research, we propose a pivotal role of "leaky gum", as an analogy of "leaky gut", to underscore the importance of the oral cavity in systemic health. The oral cavity has unique structures, the gingival sulcus (GS) and the junctional epithelium (JE) below the GS, which are rarely found anywhere else in our body. The JE is attached to the tooth enamel and cementum by hemidesmosome (HD), which is structurally weaker than desmosome and is, thus, vulnerable to microbial infiltration. In the GS, microbial biofilms can build up for life, unlike the biofilms on the skin and intestinal mucosa that fall off by the natural process. Thus, we emphasize that the GS and the JE are the weakest leaky point for microbes to invade the human body, making the leaky gum just as important as, or even more important than, the leaky gut.

Periostin regulates LPS-induced apoptosis via Nrf2/HO-1 pathway in periodontal ligament fibroblasts

OBJECTIVE

Periostin is important for the maintenance of periodontal tissue, but its role in periodontitis is controversial. This research investigated the effect of periostin in periodontitis and the underlying mechanism.

DESIGN

Mouse periodontitis models in vivo and inflammation model in vitro which were induced by Porphyromonas gingivalis lipopolysaccharide were established to evaluate periostin expression. Human periodontal ligament fibroblasts (PDLFs) were treated with lipopolysaccharide and N-acetylcysteine, fluorescence staining, flow cytometry, western blot, and qRT-PCR were used to detect reactive oxygen species (ROS), periostin expression, and apoptosis-related makers. The periostin gene was successfully transfected into PDLFs to verify the effect of periostin on apoptosis. Then, the Nrf2 inhibitor was added to clarify the mechanism.

RESULTS

Periostin expression decreased in the periodontal ligaments of mouse periodontitis models and lipopolysaccharide-induced PDLFs. Lipopolysaccharide promoted the activation of ROS and apoptosis in PDLFs, whereas N-acetylcysteine reversed this condition. Overexpression of periostin suppressed apoptosis of PDLFs and reversed the inhibitory effect of lipopolysaccharide on nuclear Nrf2 expression. Moreover, the Nrf2 inhibitor attenuated the protective effect of periostin on lipopolysaccharide-induced apoptosis.

CONCLUSIONS

Lipopolysaccharide induced apoptosis in PDLFs by inhibiting periostin expression and thus Nrf2/HO-1 pathway, indicating that periostin could be a potential therapeutic target for periodontitis.

Oral microbiota in human systematic diseases

Oral bacteria directly affect the disease status of dental caries and periodontal diseases. The dynamic oral microbiota cooperates with the host to reflect the information and status of immunity and metabolism through two-way communication along the oral cavity and the systemic organs. The oral cavity is one of the most important interaction windows between the human body and the environment. The microenvironment at different sites in the oral cavity has different microbial compositions and is regulated by complex signaling, hosts, and external environmental factors. These processes may affect or reflect human health because certain health states seem to be related to the composition of oral bacteria, and the destruction of the microbial community is related to systemic diseases. In this review, we discussed emerging and exciting evidence of complex and important connections between the oral microbes and multiple human systemic diseases, and the possible contribution of the oral microorganisms to systemic diseases. This review aims to enhance the interest to oral microbes on the whole human body, and also improve clinician’s understanding of the role of oral microbes in systemic diseases. Microbial research in dentistry potentially enhances our knowledge of the pathogenic mechanisms of oral diseases, and at the same time, continuous advances in this frontier field may lead to a tangible impact on human health.

Links between Insulin Resistance and Periodontal Bacteria: Insights on Molecular Players and Therapeutic Potential of Polyphenols

Type 2 diabetes is a metabolic disease mainly associated with insulin resistance during obesity and constitutes a major public health problem worldwide. A strong link has been established between type 2 diabetes and periodontitis, an infectious dental disease characterized by chronic inflammation and destruction of the tooth-supporting tissue or periodontium. However, the molecular mechanisms linking periodontal bacteria and insulin resistance remain poorly elucidated. This study aims to summarize the mechanisms possibly involved based on in vivo and in vitro studies and targets them for innovative therapies. Indeed, during periodontitis, inflammatory lesions of the periodontal tissue may allow periodontal bacteria to disseminate into the bloodstream and reach tissues, including adipose tissue and skeletal muscles that store glucose in response to insulin. Locally, periodontal bacteria and their components, such as lipopolysaccharides and gingipains, may deregulate inflammatory pathways, altering the production of pro-inflammatory cytokines/chemokines. Moreover, periodontal bacteria may promote ROS overproduction via downregulation of the enzymatic antioxidant defense system, leading to oxidative stress. Crosstalk between players of inflammation and oxidative stress contributes to disruption of the insulin signaling pathway and promotes insulin resistance. In parallel, periodontal bacteria alter glucose and lipid metabolism in the liver and deregulate insulin production by pancreatic β-cells, contributing to hyperglycemia. Interestingly, therapeutic management of periodontitis reduces systemic inflammation markers and ameliorates insulin sensitivity in type 2 diabetic patients. Of note, plant polyphenols exert anti-inflammatory and antioxidant activities as well as insulin-sensitizing and anti-bacterial actions. Thus, polyphenol-based therapies are of high interest for helping to counteract the deleterious effects of periodontal bacteria and improve insulin resistance.

A Mouse Periodontitis Model With Humanized Oral Bacterial Community

Increasing evidence suggests that periodontitis, characterized by oral dysbiosis, is a critical player in the progression of multiple systemic diseases in humans. However, there is still a lack of a proper mouse model of periodontitis with the colonization of human periodontitis-associated bacteria. We here established a new mouse periodontitis model by combining ligation of the second molars with application of subgingival plaques from periodontitis patients. Using 16S rRNA gene sequencing and Taxonomic classification, we found that human periodontitis-associated bacteria efficiently colonized in the mouse model and were enriched in both ligature silk and mouse saliva. Furthermore, the well-recognized periodontal pathogens including Porphyromonas gingivalis, Fusobacterium nucleatum, Prevotella intermedia, and Tannerella forsythia were enriched in the new model, but not in ligature-induced periodontitis model or Sham mice. The human periodontitis-associated bacteria potently aggravated mouse periodontitis, as demonstrated by more severe bone resorption and higher expression of inflammatory and osteoclastogenesis genes. In summary, the new mouse periodontitis model paves the way for studying human periodontitis-associated bacteria in oral diseases and systemic diseases.

Association between groups of immunoglobulin G antibodies against periodontal microorganisms and diabetes related mortality

BACKGROUND

Immunoglobulin G (IgG) antibodies against periodontal microorganisms can be markers of periodontal infection because their levels rise following infection and remain elevated several years later.

METHODS

We evaluated the relation between groups of IgG antibodies against 19 periodontal microorganisms and diabetes related mortality over 27 years among participants of the National Health and Nutrition Examination Survey III (1988 to 1992) 40 years and older at the time of examination (N = 8153).

RESULTS

Individuals in the highest versus lowest antibody tertiles were at 86% higher risk of dying due to diabetes related causes in the Red-Green antibody cluster (T. forsythia, T. denticola, A. actinomycetemcomitans, E. corrodens, S. noxia, V. parvula, C. rectus) (HR = 1.86, 95% CI 1.09 to 3.20) and 55% lower in the Orange-Blue antibody cluster (E. nodatum, A. naeslundii) (HR = 0.45, 95% CI 0.32 to 0.63) in multivariable models. In these models, individuals with diabetes at the time of examination had a 16-fold higher risk of dying due to diabetes related causes (HR = 16.4, 95% CI 11.0 to 24.7).

CONCLUSION

As a subset of periodontal microorganisms are associated with adverse systemic outcomes, antibody profiles may help in prediction of diabetes related mortality and identify sub-groups of individuals among whom periodontal treatment may impact diabetes related outcomes. This article is protected by copyright. All rights reserved.

Oral-Intestinal Microbiota in Colorectal Cancer: Inflammation and Immunosuppression

It is widely recognized that microbial disorders are involved in the pathogenesis of many malignant tumors. The oral and intestinal tract are two of the overriding microbial habitats in the human body. Although they are anatomically and physiologically continuous, belonging to the openings at both ends of the digestive tract, the oral and intestinal microbiome do not cross talk with each other due to a variety of reasons, including intestinal microbial colonization resistance and chemical barriers in the upper digestive tract. However, this balance can be upset in certain circumstances, such as disruption of colonization resistance of gut microbes, intestinal inflammation, and disruption of the digestive tract chemical barrier. Evidence is now accruing to suggest that the oral microbiome can colonize the gut, leading to dysregulation of the gut microbes. Furthermore, the oral-gut microbes create an intestinal inflammatory and immunosuppressive microenvironment conducive to tumorigenesis and progression of colorectal cancer (CRC). Here, we review the oral to intestinal microbial transmission and the inflammatory and immunosuppressive microenvironment, induced by oral-gut axis microbes in the gut. A superior comprehension of the contribution of the oral-intestinal microbes to CRC provides new insights into the prevention and treatment of CRC in the future.

Pathogenic Molecular Mechanisms in Periodontitis and Peri-Implantitis: Role of Advanced Glycation End Products

Advanced Glycation End Products (AGEs), the products of the non-enzymatic oxidation of proteins, nucleic acids, and lipids, are accumulated in periodontal tissues under hyperglycemic conditions such as Diabetes Mellitus (DM) and are responsible for sustained periodontal destruction. AGEs mediate their intracellular effects either directly or indirectly through receptor binding (via RAGE) in all types of periodontal ligament cells (osteocytes, gingival fibroblasts, stem cells, epithelial cells), indicating an important target for intervention. In combination with lipopolysaccharides (LPS) from Porphyromonas gingivalis (Pg), the negative impact of AGEs on periodontal tissue is further enhanced and accentuated. In addition, AGE accumulation is evident in peri-implantitis, yet through different underlying molecular mechanisms. Novel therapeutic approaches targeting the effects of AGEs in periodontal ligament cells show beneficial effects in pre-clinical studies. Herein, we provide evidence on the detrimental role of AGE accumulation in oral cavity tissues and their associated signaling pathways in periodontitis and peri-implantitis to further highlight the significance of oral or topical use of AGE blockers or inhibitors along with dental biofilms’ removal and DM regulation in patients’ management.

Gut Microbiota: A Key Regulator in the Effects of Environmental Hazards on Modulates Insulin Resistance

Insulin resistance is a hallmark of Alzheimer’s disease (AD), type II diabetes (T2D), and Parkinson’s disease (PD). Emerging evidence indicates that these disorders are typically characterized by alterations in the gut microbiota composition, diversity, and their metabolites. Currently, it is understood that environmental hazards including ionizing radiation, toxic heavy metals, pesticides, particle matter, and polycyclic aromatic hydrocarbons are capable of interacting with gut microbiota and have a non-beneficial health effect. Based on the current study, we propose the hypothesis of “gut microenvironment baseline drift”. According to this “baseline drift” theory, gut microbiota is a temporarily combined cluster of species sharing the same environmental stresses for a short period, which would change quickly under the influence of different environmental factors. This indicates that the microbial species in the gut do not have a long-term relationship; any split, division, or recombination may occur in different environments. Nonetheless, the “baseline drift” theory considers the critical role of the response of the whole gut microbiome. Undoubtedly, this hypothesis implies that the gut microbiota response is not merely a “cross junction” switch; in contrast, the human health or disease is a result of a rich palette of gut-microbiota-driven multiple-pathway responses. In summary, environmental factors, including hazardous and normal factors, are critical to the biological impact of the gut microbiota responses and the dual effect of the gut microbiota on the regulation of biological functions. Novel appreciation of the role of gut microbiota and environmental hazards in the insulin resistance would shed new light on insulin resistance and also promote the development of new research direction and new overcoming strategies for patients.

Novel Insight into the Mechanisms of the Bidirectional Relationship between Diabetes and Periodontitis

Periodontitis and diabetes are two major global health problems despite their prevalence being significantly underreported and underestimated. Both epidemiological and intervention studies show a bidirectional relationship between periodontitis and diabetes. The hypothesis of a potential causal link between the two diseases is corroborated by recent studies in experimental animals that identified mechanisms whereby periodontitis and diabetes can adversely affect each other. Herein, we will review clinical data on the existence of a two-way relationship between periodontitis and diabetes and discuss possible mechanistic interactions in both directions, focusing in particular on new data highlighting the importance of the host response. Moreover, we will address the hypothesis that trained immunity may represent the unifying mechanism explaining the intertwined association between diabetes and periodontitis. Achieving a better mechanistic insight on clustering of infectious, inflammatory, and metabolic diseases may provide new therapeutic options to reduce the risk of diabetes and diabetes-associated comorbidities.

Porphyromonas gingivalis Administration Induces Gestational Obesity, Alters Gene Expression in the Liver and Brown Adipose Tissue in Pregnant Mice, and Causes Underweight in Fetuses

Preventing adverse pregnancy outcomes is crucial for maternal and child health. Periodontal disease is a risk factor for many systemic diseases including adverse pregnancy outcomes, such as preterm birth and low birth weight. In addition, the administration of the periodontopathic bacterium Porphyromonas gingivalis exacerbates obesity, glucose tolerance, and hepatic steatosis and alters endocrine function in the brown adipose tissue (BAT). However, the effects of having periodontal disease during pregnancy remain unclear. Thus, this study investigates the effect of P. gingivalis administration on obesity, liver, and BAT during pregnancy. Sonicated P. gingivalis (Pg) or saline (Co) was injected intravenously and administered orally to pregnant C57BL/6J mice three times per week. Maternal body weight and fetal body weight on embryonic day (ED) 18 were evaluated. Microarray analysis and qPCR in the liver and BAT and hepatic and plasma triglyceride quantification were performed on dams at ED 18. The body weight of Pg dams was heavier than that of Co dams; however, the fetal body weight was decreased in the offspring of Pg dams. Microarray analysis revealed 254 and 53 differentially expressed genes in the liver and BAT, respectively. Gene set enrichment analysis exhibited the downregulation of fatty acid metabolism gene set in the liver and estrogen response early/late gene sets in the BAT, whereas inflammatory response and IL6/JAK/STAT3 signaling gene sets were upregulated both in the liver and BAT. The downregulation of expression levels of Lpin1, Lpin2, and Lxra in the liver, which are associated with triglyceride synthesis, and a decreasing trend in hepatic triglyceride of Pg dams were observed. P. gingivalis administration may alter lipid metabolism in the liver. Overall, the intravenous and oral administration of sonicated P. gingivalis-induced obesity and modified gene expression in the liver and BAT in pregnant mice and caused fetuses to be underweight.

Calcitriol-enhanced autophagy in gingival epithelium attenuates periodontal inflammation in rats with type 2 diabetes mellitus

Type 2 diabetes mellitus (T2DM)-associated periodontitis is a common disease with high prevalence, associated with persistent infection and complicated manifestations. Calcitriol (1 alpha, 25-dihydroxyvitamin D3, 1,25D) is the active form of vitamin D that plays a protective role in immune regulation, bone metabolism, and inflammatory response. In this study, we constructed a T2DM model in rats by combining a high-fat diet with low-dose streptozotocin. The periodontitis model in rats was developed by ligation and Porphyromonas gingivalis (ATCC 33277) inoculation. Rats were randomly divided into five groups: non-diabetic blank, diabetic blank, diabetes with calcitriol treatment, diabetes with 3-methyladenine (3-MA) treatment, or diabetes with calcitriol and 3-MA treatment. The diabetic rats exhibited an intense inflammatory response and decreased autophagy compared with the non-diabetic rats. Intraperitoneal injection of calcitriol and autophagy inhibitor (3-MA) allowed us to explore the effect of calcitriol on inflammation in the gingival epithelium and the role of autophagy in this process. Treatment with calcitriol resulted in the decreased expression of NFκB-p65, p62/SQSTM1 and inflammatory response and increased expression of LC3-II/LC3-I. Application of 3-MA significantly suppressed autophagy, which was apparently retrieved by calcitriol. Antibacterial peptide (LL-37) is the only antimicrobial peptide in the cathelicidin family that is found in the human body, and it exhibits a broad spectrum of antibacterial activity and regulates the immune system. In the present study, our findings indicated that calcitriol-enhanced autophagy may attenuated periodontitis and the decrease of LL-37 was rescued by calcitriol treatment in the gingival epithelial cells of T2DM rats. Our study provides evidence for the application of calcitriol as an adjunctive treatment for T2DM-associated periodontitis.

Suppressed inflammation in obese children induced by a high-fiber diet is associated with the attenuation of gut microbial virulence factor genes

In our previous study, a gut microbiota-targeted dietary intervention with a high-fiber diet improved the immune status of both genetically obese (Prader-Willi Syndrome, PWS) and simple obese (SO) children. However, PWS children had higher inflammation levels than SO children throughout the trial, the gut microbiota of the two cohorts was similar. As some virulence factors (VFs) produced by the gut microbiota play a role in triggering host inflammation, this study compared the characteristics and changes of gut microbial VF genes of the two cohorts before and after the intervention using a fecal metagenomic dataset. We found that in both cohorts, the high-fiber diet reduced the abundance of VF, and particularly pathogen-specific, genes. The composition of VF genes was also modulated, especially for offensive and defensive VF genes. Furthermore, genes belonging to invasion, T3SS (type III secretion system), and adherence classes were suppressed. Co-occurrence network analysis detected VF gene clusters closely related to host inflammation in each cohort. Though these cohort-specific clusters varied in VF gene combinations and cascade reactions affecting inflammation, they mainly contained VFs belonging to iron uptake, T3SS, and invasion classes. The PWS group had a lower abundance of VF genes before the trial, which suggested that other factors could also be responsible for the increased inflammation in this cohort. This study provides insight into the modulation of VF gene structure in the gut microbiota by a high-fiber diet, with respect to reduced inflammation in obese children, and differences in VF genes between these two cohorts.

Berberine as a promising natural compound for the treatment of periodontal disease: A focus on anti-inflammatory properties

Accumulating evidence during the last two decades has addressed the potential anti‐inflammatory properties of berberine (BBR), a bioactive alkaloid compound isolated from Coptidis rhizoma, in controlling or treating several inflammatory diseases. Periodontitis is one of the most common chronic and serious inflammatory diseases, in which uncontrolled and unabated host immune responses against periodontopathic pathogens play critical and crucial roles in the disease pathogenesis. Hence, regulating inflammatory responses in periodontitis has a valuable approach and holds promise in treating periodontitis. For the first time, this paper reviews the evidence from in vitro and in vivo experimental models to explore the anti‐inflammatory effects of BBR in periodontitis and exhibits that BBR has the high potency to exert anti‐inflammatory effects by reducing expression and secretion of pro‐inflammatory mediators including TNF‐α, IL‐1β, IL‐17, RANKL, MMP‐2, MMP‐9 and MCP‐1. The BBR‐mediated anti‐inflammatory actions could translate into the inhibition of the periodontal tissues and alveolar bone destruction and the control of the disease in vivo. As the second aim of this paper, we also paid attention to the therapeutic potential of BBR in treating human diseases regarding its anti‐inflammatory properties.

Inorganic nitrate: A potential prebiotic for oral microbiota dysbiosis associated with type 2 diabetes

Oral microbiota dysbiosis, concomitant with decreased abundance of nitrate (NO₃^-)-reducing bacteria, oral net nitrite (NO₂^-) production, and reduced nitric oxide (·NO) bioactivity, is associated with the development of cardiometabolic disorders. Therefore, restoring the oral microbiome to a health-associated state is suggested as a therapeutic approach to potentiate the NO₃^--NO₂^--·NO pathway and provide a backup resource for insufficient NO production in conditions including cardiovascular disease and type 2 diabetes mellitus (T2DM). The current review discusses how inorganic NO₃^- can improve the oral microbial community in patients with T2DM and act as a prebiotic. Both animal and human experiments indicated that inorganic NO₃^- modulates the oral microbiome by increasing the abundance of health-associated NO₃^--reducing bacteria (e.g., Neisseria and Rothia) and decreasing the plenty of species Prevotella and Veillonella, leading to oral NO₂^- accumulation and improved systemic ·NO availability. Supplementation with NO₃^- reduces caries- and periodontitis-associated bacteria and the pathogenic genus related to insulin resistance and glucose intolerance. In addition, inorganic NO₃^- may provide a more optimal environment for NO₃^- reductase activity in the oral cavity, as it increases salivary flow rate and prevents decreased pH by inhibiting acid-producing bacteria.

Sulfonylureas for Treatment of Periodontitis-Diabetes Comorbidity-Related Complications: Killing Two Birds With One Stone

Periodontitis is one of the most prevalent oral inflammatory diseases leading to teeth loss and oral health problems in adults. Periodontitis mainly affects periodontal tissue by affecting the host immune system and bone homeostasis. Moreover, periodontitis is associated with various systemic diseases. Diabetes is a metabolic disease with systemic effects. Both periodontitis and diabetes are common inflammatory diseases, and comorbidity of two diseases is linked to exacerbation of the pathophysiology of both diseases. Since bacterial dysbiosis is mainly responsible for periodontitis, antibiotics are widely used drugs to treat periodontitis in clinics. However, the outcomes of antibiotic treatments in periodontitis are not satisfactory. Therefore, the application of anti-inflammatory drugs in combination with antibiotics could be a treatment option for periodontitis-diabetes comorbidity. Anti-diabetic drugs usually have anti-inflammatory properties and have shown beneficial effects on periodontitis. Sulfonylureas, insulin secretagogues, are the earliest and most widely used oral hypoglycemic drugs used for type-2 diabetes. Studies have found that sulfonylurea drugs can play a certain role in the mitigation of periodontitis and inflammation. This article reviews the effects of sulfonylurea drugs on the mitigation of periodontitis-diabetes comorbidity-related inflammation, bone loss, and vascular growth as well as the involved molecular mechanisms. We discuss the possibility of a new application of sulfonylureas (old drug) to treat periodontitis-diabetes comorbidity.

Periodontal disease-related nonalcoholic fatty liver disease and nonalcoholic steatohepatitis: An emerging concept of oral-liver axis

Periodontal disease, a chronic inflammatory disease of the periodontal tissues, is not only a major cause of tooth loss, but it is also known to exacerbate/be associated with various metabolic disorders, such as obesity, diabetes, dyslipidemia, and cardiovascular disease. Recently, growing evidence has suggested that periodontal disease has adverse effects on the pathophysiology of liver disease. In particular, nonalcoholic fatty liver disease, a hepatic manifestation of metabolic syndrome, has been associated with periodontal disease. Nonalcoholic fatty liver disease is characterized by hepatic fat deposition in the absence of a habitual drinking history, viral infections, or autoimmune diseases. A subset of nonalcoholic fatty liver diseases can develop into more severe and progressive forms, namely nonalcoholic steatohepatitis. The latter can lead to cirrhosis and hepatocellular carcinoma, which are end‐stage liver diseases. Extensive research has provided plausible mechanisms to explain how periodontal disease can negatively affect nonalcoholic fatty liver disease and nonalcoholic steatohepatitis, namely via hematogenous or enteral routes. During periodontitis, the liver is under constant exposure to various pathogenic factors that diffuse systemically from the oral cavity, such as bacteria and their by‐products, inflammatory cytokines, and reactive oxygen species, and these can be involved in disease promotion of nonalcoholic fatty liver disease and nonalcoholic steatohepatitis. Also, gut microbiome dysbiosis induced by enteral translocation of periodontopathic bacteria may impair gut wall barrier function and promote the transfer of hepatotoxins and enterobacteria to the liver through the enterohepatic circulation. Moreover, in a population with metabolic syndrome, the interaction between periodontitis and systemic conditions related to insulin resistance further strengthens the association with nonalcoholic fatty liver disease. However, most of the pathologic links between periodontitis and nonalcoholic fatty liver disease in humans are provided by epidemiologic observational studies, with the causal relationship not yet being established. Several systematic and meta‐analysis studies also show conflicting results. In addition, the effect of periodontal treatment on nonalcoholic fatty liver disease has hardly been studied. Despite these limitations, the global burden of periodontal disease combined with the recent nonalcoholic fatty liver disease epidemic has important clinical and public health implications. Emerging evidence suggests an association between periodontal disease and liver diseases, and thus we propose the term periodontal disease–related nonalcoholic fatty liver disease or periodontal disease–related nonalcoholic steatohepatitis. Continued efforts in this area will pave the way for new diagnostic and therapeutic approaches based on a periodontologic viewpoint to address this life‐threatening liver disease.

Controlled release of iodine from cross-linked cyclodextrin metal-organic frameworks for prolonged periodontal pocket therapy

Effective therapeutic system to periodontitis was designed using cross-linked cyclodextrin metal-organic framework (COF) as carrier for iodine and further suspended in hydroxyethyl cellulose gel as I2@COF-HEC hydrogel. Inclusion of iodine within the COF was demonstrated by SR-FTIR spectral and characteristic DSC and TGA changes. Molecular modelling identified the interaction of iodine with both COF central cavity and individual cyclodextrin moieties of COF. In vitro results of study demonstrated that iodine release in artificial saliva from I2@COF-HEC hydrogel could be extended up to 5 days, which was slower than I2@COF particles. Using an in vivo rat model of periodontitis, micro-computed tomography of alveolar bone morphology demonstrated that I2@COF-HEC hydrogel showed similar effects in decreasing periodontal pocket depth and alveolar bone resorption to minocycline ointment, a periodontitis antibiotic. The I2@COF-HEC hydrogel is a novel local delivery device of iodine as a broad spectrum antimicrobial use for treatment of periodontitis.

The Potential Role of RP105 in Regulation of Inflammation and Osteoclastogenesis During Inflammatory Diseases

Inflammatory diseases have a negative impact on bone homeostasis via exacerbated local and systemic inflammation. Bone resorbing osteoclasts are mainly derived from hematopoietic precursors and bone marrow monocytes. Induced osteoclastogenesis during inflammation, autoimmunity, metabolic diseases, and cancers is associated with bone loss and osteoporosis. Proinflammatory cytokines, pathogen-associated molecular patterns, or endogenous pathogenic factors induce osteoclastogenic differentiation by binding to the Toll-like receptor (TLR) family expressed on surface of osteoclast precursors. As a non-canonical member of the TLRs, radioprotective 105 kDa (RP105 or CD180) and its ligand, myeloid differentiation protein 1 (MD1), are involved in several bone metabolic disorders. Reports from literature had demonstrated RP105 as an important activator of B cells, bone marrow monocytes, and macrophages, which regulates inflammatory cytokines release from immune cells. Reports from literature had shown the association between RP105 and other TLRs, and the downstream signaling mechanisms of RP105 with different “signaling-competent” partners in immune cells during different disease conditions. This review is focused to summarize: (1) the role of RP105 on immune cells’ function and inflammation regulation (2) the potential regulatory roles of RP105 in different disease-mediated osteoclast activation and the underlying mechanisms, and (3) the different “signaling-competent” partners of RP105 that regulates osteoclastogenesis.

What Are the Clinical and Systemic Results of Periodontitis Treatment in Obese Individuals?

Purpose of Review

Periodontitis and obesity are characterized by a dysregulated inflammatory state. Obese individuals have a higher chance of presenting periodontitis. Clinical studies in different populations demonstrate that individuals with obesity have worse periodontal conditions. This current review aims to explore recent literature to understand what the impacts of obesity on periodontal treatment outcomes are and to learn whether periodontal treatment can improve systemic biomarkers in obese individuals.

Recent Findings

Short- and long-term evaluations demonstrated that non-surgical periodontal treatment could improve clinical parameters in obese individuals, represented as the reduction in mean probing depth, sites with probing depth ≥ 4 mm, and extension of bleeding on probing. However, obese individuals may have less clinical improvement when compared to normal-weight individuals with a similar periodontal profile. Additionally, periodontal treatment may contribute to a reduction in systemic levels of retinol-binding protein 4 and leptin, while promoting an increase in systemic levels of adiponectin.

Summary

Overall, obese individuals with periodontitis can significantly benefit from non-surgical periodontal treatment. However, clinical improvements seem to be less prominent in obese individuals with periodontitis compared to non-obese individuals with similar periodontal status. Nevertheless, periodontal treatment may impact significantly on the reduction of several biochemical biomarkers of obesity with or without weight reduction. Further investigations are needed to improve our comprehension of the mechanisms underlying those findings.

Oral Microbiota: A Major Player in the Diagnosis of Systemic Diseases

The oral cavity is host to a complex and diverse microbiota community which plays an important role in health and disease. Major oral infections, i.e., caries and periodontal diseases, are both responsible for and induced by oral microbiota dysbiosis. This dysbiosis is known to have an impact on other chronic systemic diseases, whether triggering or aggravating them, making the oral microbiota a novel target in diagnosing, following, and treating systemic diseases. In this review, we summarize the major roles that oral microbiota can play in systemic disease development and aggravation and also how novel tools can help investigate this complex ecosystem. Finally, we describe new therapeutic approaches based on oral bacterial recolonization or host modulation therapies. Collaboration in diagnosis and treatment between oral specialists and general health specialists is of key importance in bridging oral and systemic health and disease and improving patients' wellbeing.

Porphyromonas gingivalis exacerbates the progression of fatty liver disease via CD36-PPARγ pathway

Periodontal diseases have been reported to have a multidirectional association with metabolic disorders. We sought to investigate the correlation between periodontitis and diabetes or fatty liver disease using HFD-fed obese mice inoculated with P. gingivalis. Body weight, alveolar bone loss, serological biochemistry, and glucose level were determined to evaluate the pathophysiology of periodontitis and diabetes. For the evaluation of fatty liver disease, hepatic nonalcoholic steatohepatitis (NASH) was assessed by scoring steatosis, inflammation, hepatocyte ballooning and the crucial signaling pathways involved in liver metabolism were analyzed. The C-reactive protein (CRP) level and NASH score in P. gingivalis-infected obese mice were significantly elevated. Particularly, the extensive lobular inflammation was observed in the liver of obese mice infected with P. gingivalis. Moreover, the expression of metabolic regulatory factors, including peroxisome proliferator-activated receptor γ (Pparγ) and the fatty acid transporter Cd36, was up-regulated in the liver of P. gingivalis-infected obese mice. However, inoculation of P. gingivalis had no significant influence on glucose homeostasis, insulin resistance, and hepatic mTOR/AMPK signaling. In conclusion, our results indicate that P. gingivalis can induce the progression of fatty liver disease in HFD-fed mice through the upregulation of CD36-PPARγ axis.

Role of experimental periodontitis in inducing pulmonary inflammation in mice

OBJECTIVE

The aim of the study was to explore the potential role of experimental periodontitis in pulmonary inflammation in mice.

MATERIALS AND METHODS

Mice were divided into control, ligature-induced periodontitis (L) and ligature plus Porphyromonas gingivalis (P. gingivalis)-induced periodontitis (LPG) groups. Alveolar bone resorption, pulmonary function, lung tissue histology and cytokine expression were examined at 2, 4 and 8 weeks. Then cytokines and neutrophils in the peripheral blood and lung tissue were further assessed at 8 weeks to determine the role of cytokines induced by LPG periodontitis, and the effect of P. gingivalis was evaluated using P. gingivalis-IgG and P. gingivalis gingipain.

RESULTS

Alveolar bone resorption was more severe in the L and LPG groups. However, pulmonary inflammation was observed only in the LPG group at 8 weeks when cytokines and neutrophils in the peripheral blood and lung tissue were the most significant elevation, along with higher levels of P. gingivalis-IgG and P. gingivalis gingipain. Cytokine levels were also increased in the gingival tissue, peripheral blood and lung tissue in the L group, accompanied by elevated peripheral blood neutrophils, but not as significantly as that in the LPG group.

CONCLUSIONS

LPG periodontitis can trigger pulmonary inflammation over the long term, in which cytokines and P. gingivalis play an important role.

Connection between Periodontitis-Induced Low-Grade Endotoxemia and Systemic Diseases: Neutrophils as Protagonists and Targets

Periodontitis is considered a promoter of many systemic diseases, but the signaling pathways of this interconnection remain elusive. Recently, it became evident that certain microbial challenges promote a heightened response of myeloid cell populations to subsequent infections either with the same or other pathogens. This phenomenon involves changes in the cell epigenetic and transcription, and is referred to as ''trained immunity''. It acts via modulation of hematopoietic stem and progenitor cells (HSPCs). A main modulation driver is the sustained, persistent low-level transmission of lipopolysaccharide from the periodontal pocket into the peripheral blood. Subsequently, the neutrophil phenotype changes and neutrophils become hyper-responsive and prone to boosted formation of neutrophil extracellular traps (NET). Cytotoxic neutrophil proteases and histones are responsible for ulcer formations on the pocket epithelium, which foster bacteremia and endoxemia. The latter promote systemic low-grade inflammation (SLGI), a precondition for many systemic diseases and some of them, e.g., atherosclerosis, diabetes etc., can be triggered by SLGI alone. Either reverting the polarized neutrophils back to the homeostatic state or attenuation of neutrophil hyper-responsiveness in periodontitis might be an approach to diminish or even to prevent systemic diseases.

Gut Microbiota May Mediate the Influence of Periodontitis on Prediabetes

Mounting evidence has shown that periodontitis is associated with diabetes. However, a causal relationship remains to be determined. Recent studies reported that periodontitis may be associated with gut microbiota, which plays an important role in the development of diabetes. Therefore, we hypothesized that gut microbiota might mediate the link between periodontitis and diabetes. Periodontitis was induced by ligatures. Glycemic homeostasis was evaluated through fasting blood glucose (FBG), serum glycosylated hemoglobin (HbA1c), and intraperitoneal glucose tolerance test. Micro-computed tomography and hematoxylin and eosin staining were used to evaluate periodontal destruction. The gut microbiota was analyzed using 16S ribosomal RNA gene sequencing and bioinformatics. Serum endotoxin, interleukin (IL) 6, tumor necrosis factor α (TNF-α), and IL-1β were measured to evaluate the systemic inflammation burden. We found that the levels of FBG, HbA1c, and glucose intolerance were higher in the periodontitis (PD) group than in the control (Con) group (P < 0.05). When periodontitis was eliminated, the FBG significantly decreased (P < 0.05). Several butyrate-producing bacteria were decreased in the gut microbiota of the PD group, including Lachnospiraceae_NK4A136_group, Eubacterium_fissicatena_group, Eubacterium_coprostanoligenes_group, and Ruminococcaceae_UCG-014 (P < 0.05), which were negatively correlated with serum HbA1c (P < 0.05). Subsequently, the gut microbiota was depleted using antibiotics or transplanted through cohousing. Compared with the PD group, the levels of HbA1c and glucose intolerance were decreased in the gut microbiota-depleted mice with periodontitis (PD + Abx) (P < 0.05), as well as the serum levels of endotoxin and IL-6 (P < 0.05). The serum levels of IL-6, TNF-α, and IL-1β in the PD + Abx group were higher than those of the Con group (P < 0.05). Antibiotics exerted a limited impact on the periodontal microbiota. When the PD mice were cohoused with healthy ones, the elevated FBG and HbA1c significantly recovered (P < 0.05), as well as the aforementioned butyrate producers (P < 0.05). Thus, within the limitations of this study, our data indicated that the gut microbiota may mediate the influence of periodontitis on prediabetes.

Obesity Drives an Oral Microbiota Signature of Female Patients with Periodontitis: A Pilot Study

The aim of this study was to analyze the link between oral microbiota and obesity in humans. We conducted a pilot study including 19 subjects with periodontitis divided into two groups: normo-weighted subjects (NWS) with a body mass index (BMI) between 20 and 25 (n = 9) and obese subjects (OS) with a BMI > 30 (n = 10). Obesity was associated with a poor oral health status characterized by an increased number of missing teeth and a higher score of periodontal-support loss associated with dysbiotic oral microbiota (39.45 ± 3.74 vs. 26.41 ± 11.21, p = 0.03 for the Chao 1 index). Oral microbiota taxonomic analysis showed that the abundance of the Capnocytophaga genus was higher (2.47% ± 3.02 vs. 0.27% ± 0.29, p = 0.04) in OS compared to NWS. Obese females (OF) were characterized by an increase in the Streptococcus genus (34.12% ± 14.29 vs. 10.55% ± 10.42, p = 0.05) compared to obese males (OM), where the Neisseria genus was increased (5.75% ± 5.03 vs. 58.05% ± 30.64, p = 0.008). These first data suggest that sex/gender is determinant in the link between oral dysbiotic microbiota and obesity in patients with periodontitis. Our results could lead to recommendations concerning therapeutic strategies for obese patients with periodontitis following the sex/gender.

Role of the gut microbiota in type 2 diabetes and related diseases

Type 2 diabetes is the fastest-growing metabolic disease in the world. Many clinical studies have found that type 2 diabetes patients have metabolic disorders and chronic inflammatory states accompanied by disturbances in the gut microbiota. The gut microbiota plays an important role in body metabolism and immune regulation, and disturbances in the gut microbiota in conjunction with destruction of the intestinal barrier in type 2 diabetes patients causes damage to multiple organs. Therefore, the gut microbiota may be a new therapeutic target for treating type 2 diabetes and related diseases. In this review, we introduce the characteristics of the gut microbiota in type 2 diabetes and related diseases, as well as highlight the potential molecular mechanisms of their effects on intestinal barrier disruption, metabolic disorders, and chronic inflammation. Finally, we summarize an intestinal microecological therapeutic strategy, with a focus on shaping the intestinal bacteria, to improve the malignant progress of type 2 diabetes and related diseases. AUTHOR SUMMARY: Type 2 diabetes (T2D) is the fastest-growing metabolic disease in the world. Many clinical studies have found that T2D patients have metabolic disorders and chronic inflammatory states, accompanied by disturbances of the gut microbiota and increased intestinal permeability. The number of human gut microbiota is more than 10 times of human cells, and they play an important role in the body's metabolism and immune regulation. The abnormal intestinal metabolites and intestinal barrier disruption caused by the gut microbiota dysbiosis in the T2D facilitate intestinal bacteria and their harmful metabolites entering the circulatory system. The abnormal entering will cause the damage to multiple organs through disturbing insulin sensitivity, glucose metabolism, and immune homeostasis. Therefore, the gut microbiota may be a new therapeutic target for improving T2D and its related diseases. In this review, we introduce the compositional characteristics of the gut microbiota in T2D, and highlight some new molecular mechanisms of their effects on intestinal barrier disruption, metabolic disorders and chronic inflammation in T2D and its related diseases. Finally, we summarize an intestinal microecological therapeutic strategy, with a focus on shaping the intestinal bacteria, to improve the malignant progress of T2D and related diseases.

The Association between Periodontitis and Inflammatory Bowel Disease: A Systematic Review and Meta-analysis

BACKGROUND

It has been reported that patients with inflammatory bowel disease (IBD) are more susceptible to periodontitis. However, data regarding the risk of periodontitis in IBD patients are scarce, and results from individual studies remain controversial. The aim of this study is to investigate the risk of periodontitis in IBD patients.

METHODS

Web of Science, PubMed, and Embase were searched for studies investigating the risk of periodontitis in the IBD patient population from Jan. 2000 to Nov. 2020. Articles were included if they contained the number of people with IBD diagnosed with periodontitis (or periodontal disease parameters) compared with a control group. Case reports, reviews, animal studies, and articles without available abstracts were excluded. A pooled odds ratio (OR) and 95% confidence interval (CI) were calculated to assess the association between periodontitis and IBD.

RESULTS

Six studies were included in the meta-analysis. The overall risk of periodontitis was significantly higher in IBD patients than controls (OR: 2.10, 95% CI: 1.60-2.74; I 2 = 27%). In particular, Crohn's disease (CD) and ulcerative colitis (UC) were both linked to an increased risk of periodontitis (OR: 1.72, 95% CI: 1.36-2.19; I 2 = 0% for CD vs. OR:2.39, 95% CI: 1.19-4.80; I 2 = 85% for UC).

CONCLUSIONS

IBD patients are at higher risk of periodontitis than controls. After subgroup analysis, the elevated risk remained significant when analyzing CD or UC alone. UC patients were at higher risk of developing periodontitis than CD patients.

The Role of Bacterial and Fungal Human Respiratory Microbiota in COVID-19 Patients

Recently, severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), the etiologic agent of coronavirus disease 2019 (COVID-19), has led to a worldwide pandemic with millions of infected patients. Alteration in humans' microbiota was also reported in COVID-19 patients. The alteration in human microbiota may contribute to bacterial or viral infections and affect the immune system. Moreover, human's microbiota can be altered due to SARS-CoV-2 infection, and these microbiota changes can indicate the progression of COVID-19. While current studies focus on the gut microbiota, it seems necessary to pay attention to the lung microbiota in COVID-19. This study is aimed at reviewing respiratory microbiota dysbiosis among COVID-19 patients to encourage further studies on the field for assessment of SARS-CoV-2 and respiratory microbiota interaction.

Local and systemic mechanisms linking periodontal disease and inflammatory comorbidities

Periodontitis, a major inflammatory disease of the oral mucosa, is epidemiologically associated with other chronic inflammation-driven disorders, including cardio-metabolic, neurodegenerative and autoimmune diseases and cancer. Emerging evidence from interventional studies indicates that local treatment of periodontitis ameliorates surrogate markers of comorbid conditions. The potential causal link between periodontitis and its comorbidities is further strengthened by recent experimental animal studies establishing biologically plausible and clinically consistent mechanisms whereby periodontitis could initiate or aggravate a comorbid condition. This multi-faceted ‘mechanistic causality’ aspect of the link between periodontitis and comorbidities is the focus of this Review. Understanding how certain extra-oral pathologies are affected by disseminated periodontal pathogens and periodontitis-associated systemic inflammation, including adaptation of bone marrow haematopoietic progenitors, may provide new therapeutic options to reduce the risk of periodontitis-associated comorbidities.

Periodontitis has been causally linked to the development of other chronic inflammatory diseases outside the oral mucosa. In this Review, George Hajishengallis and Triantafyllos Chavakis consider the molecular basis of these links.

Effects of melatonin on insulin signaling and inflammatory pathways of rats with apical periodontitis

AIM

To verify the effects of melatonin supplementation on insulin sensitivity, plasma concentrations of inflammatory cytokines, insulin signalling and inflammatory pathways in the soleus (SM) and extensor digitorum longus (EDL) muscles of rats with apical periodontitis (AP).

METHODOLOGY

Seventy-two Wistar rats were distributed into 4 groups: (a) control (C), (b) control supplemented with melatonin (M), (c) AP (AP), and (d) AP supplemented with melatonin (AP + M). AP was induced by pulp exposure of the maxillary and mandibular right first and second molars to the oral environment. After AP induction, oral supplementation with 5 mg kg^-1 melatonin (diluted in drinking water) for 60 days was initiated. At the end of the treatment, the following were analysed: (1) plasma concentrations of insulin and inflammatory cytokines (TNF-α, IL-6, IL-1β and IL-10) using ELISA kits; (2) glycaemia using enzymatic assay; (3) insulin resistance using homoeostasis model assessment of insulin resistance (HOMA-IR) index; and (4) phosphorylation status of pp185 tyrosine, Akt serine, IKKα/β, and JNK in SM and EDL using Western blot. Analysis of variance of two or three factors was performed, followed by the Bonferroni test. P values < 0.05 were considered statistically significant.

RESULTS

AP promoted insulin resistance, significantly increased (P < 0.05) plasma concentrations of pro-inflammatory cytokines (TNF-α, IL-6, and IL-1β), significantly decreased (P < 0.05) the concentration of anti-inflammatory cytokine IL-10, impaired insulin signalling in SM, and increased IKKα/β phosphorylation status in SM and EDL. Melatonin supplementation in rats with AP improved insulin sensitivity, significantly decreased (P < 0.05) TNF-α and IL-1β, significantly increased (P < 0.05) IL-10 plasma concentrations, and changed the insulin signalling in soleus muscle and IKKα/β phosphorylation status in SM and EDL muscles.

CONCLUSIONS

Melatonin is a potent adjuvant treatment for improving apical periodontitis-associated changes in insulin sensitivity, insulin signalling and inflammatory pathways. In addition, the negative impact of AP on general health was also demonstrated.

Special Issue: 2019 Consortium for Trans-Pyrenean Investigations on Obesity and Diabetes

This Special Issue of the Journal of Physiology and Biochemistry contains 6 contributions that exemplify the advances obtained by the mini-network entitled "Consortium of Trans-Pyrenean Investigations on Obesity and Diabetes" (CTPIOD), which is on its 16th year of existence. This scientific community, essentially based in France and Spain, but also open to participants coming from all over the world, is focusing its attention on the prevention and the novel treatments of obesity, diabetes, and other non-communicable diseases. Accordingly, this special issue will cover some nutritional, pharmacologic, and genetic aspects of the current knowledge of metabolic diseases. Some of these papers emerge from the lectures of the 16th Conference on Trans-Pyrenean Investigations in Obesity and Diabetes, held in Soria (Spain) in June 2019.

Accuracy of a 7-Item Patient-Reported Stand-Alone Tool for Periodontitis Screening

Periodontitis is interrelated with various other chronic diseases. Recent evidence suggests that treatment of periodontitis improves glycemic control in diabetes patients and reduces the costs of diabetes treatment. So far, however, screening for periodontitis in non-dental settings has been complicated by a lack of easily applicable and reliable screening tools which can be applied by non-dental professionals. The purpose of this study was to assess the diagnostic accuracy of a short seven-item tool developed by the German Society for Periodontology (DG PARO) to screen for periodontitis by means of patient-reported information. A total of 88 adult patients filled in the patient-reported Periodontitis Risk Score (pPRS; range: 0 points = lowest periodontitis risk; 20 points = very high periodontitis risk) questionnaire before dental check-up at Heidelberg University Hospital. Subsequent clinical assessments according to Periodontal Screening and Recording (PSR®) were compared with pPRS scores. The diagnostic accuracy of pPRS at different cutoff values was assessed according to sensitivity, specificity, positive, and negative predictive values, as well as Receiver-Operator-Characteristic curves, Area Under the Curve (AUC), and logistic regression analysis. According to combined specificity and sensitivity (AUC = 0.86; 95%-CI: 0.76-0.95), the diagnostic accuracy of the pPRS for detecting periodontal inflammation (PSR® ≥ 3) was highest for a pPRS cutoff distinguishing between pPRS scores < 7 vs. ≥ 7. Patients with pPRS scores ≥ 7 had a 36.09 (95%-CI: 9.82-132.61) times higher chance of having a PSR® ≥ 3 than patients with scores < 7. In conclusion, the pPRS may be considered an appropriately accurate stand-alone tool for the screening for periodontitis.

Clinical significance and prognostic value of Porphyromonas gingivalis infection in lung cancer

A variety of pathogenic microorganisms can promote the occurrence and development of malignant tumors by colonizing in the body. It has been shown that Porphyromonas gingivalis (P. gingivalis) can be colonized for a long time in upper gastrointestinal tumors and is closely related to the occurrence and development of esophageal cancer in previous studies of our team. Because the esophagus and trachea are closely adjacent and P. gingivalis can instantly enter and colonize in cells, we speculate that P. gingivalis may be colonized in lung cancer cells through oral or blood, promoting the malignant progression of lung cancer. In this study, we investigated P. gingivalis infection in lung carcinoma tissues and adjacent lung tissues, and found that the colonization rate of P. gingivalis in carcinoma tissues was significantly higher than that in adjacent lung tissues. Therefore, we propose that the microenvironment of cancer cells is more conducive to the survival of P. gingivalis. Then, we analyzed the correlation between P. gingivalis infection and clinicopathological features and survival prognosis of patients with lung cancer. It was found that P. gingivalis infection was closely related to smoking, drinking, lymph node metastasis and clinical stage. Moreover, the survival rate and median survival time of patients with P. gingivalis infection were significantly shortened. Therefore, we put forward the view that long term smoking and drinking will cause a bad oral environment, increasing the risk of P. gingivalis infection, then P. gingivalis infection will promote the malignant progression of lung cancer.

Identification of an oral microbiota signature associated with an impaired orosensory perception of lipids in insulin-resistant patients

AIMS

Type 2 diabetes leads to multiple sensory dysfunctions affecting notably the gustatory sensitivity. Although this sensory defect, by impacting food choices, might lead to unhealthy eating behavior, underlying mechanisms remains poorly studied. We have recently reported that the composition of microbiota in contact with circumvallate gustatory papillae might affect the orosensory perception of lipids in lean and normoglycemic obese subjects. This finding has prompted us to explore whether such a phenomenon also occurs in diabetic obese patients.

METHODS

The composition of microbiota surrounding the circumvallate papillae was analyzed in combination with the linoleic acid perception thresholds in male insulin-resistant patients and weight-matched healthy controls. Two complementary comparisons were performed: (1) controls vs diabetic and (2) diabetic low-lipid tasters versus diabetic high-lipid tasters.

RESULTS

Despite subtle modifications in the oral microbiota composition, comparison of orosensory lipid perception in controls and diabetic subjects did not lead to discriminating data due to the large inter-individual variability of linoleic acid perception thresholds. In contrast, specific bacterial signatures were found by comparing diabetic low- and high-lipid tasters leading to differential molecular pathways. Surprisingly, a lower fatty taste perception was mainly found in patients treated with metformin and/or statins, suggesting a possible side effect of these antidiabetic and/or hypolipidemic drugs on taste acuity.

CONCLUSIONS

Collectively, these data show that the diabetic patients with defective fatty taste detection are characterized by a specific microbiota metabolism at the circumvallate papillae levels, this occurrence seeming amplified by drugs commonly used to counteract the damaging metabolic effects of T2D. Trial registration for original previous studies: ClinicalTrials.gov #NCT02028975.

Periodontitis in elderly patients with type 2 diabetes mellitus: impact on gut microbiota and systemic inflammation

Elderly patients with type 2 diabetes mellitus (T2DM) exhibit considerable periodontitis frequency, which causes tooth loss and poor quality of life. To investigate the impact of periodontitis on gut microbiota, we used 16S rRNA amplicon sequencing to characterize the composition and structure of gut microbiota among elderly patients with T2DM and periodontitis (T2DM_P), elderly patients with T2DM alone (T2DM_NP), and healthy volunteers. We identified 34 key gut microbiota markers that distinguished participants with different periodontal conditions and investigated their connections to other gut bacteria, as well as their clinical correlates. The most striking differences in co-occurrence networks between the T2DM_P and T2DM_NP groups comprised interactions involving dominant genera in the oral cavity (i.e., Streptococcus and Veillonella). Of the 34 identified key gut microbiota markers that distinguished participants with different periodontal conditions, 25 taxa were correlated with duration of diabetes, dry mouth or the peripheral levels of pro-inflammatory cytokines (e.g., tumor necrosis factor-α, interferon-γ, prostaglandin E2, interleukin-17, and interleukin-6) and metabolic parameters (e.g., hemoglobin A1c), respectively. Our findings suggest that gut microbial shifts driven by periodontitis may contribute to systemic inflammation and metabolic dysfunction during the progression of T2DM.

A gut dysbiotic microbiota-based hypothesis of human-to-human transmission of non-communicable diseases

Non-communicable diseases (NCDs) have replaced communicable diseases as the leading cause of premature death worldwide over the past century. Increasing numbers of studies have reported a link between NCDs and dysbiotic gut microbiota. Some gut microbiota, such as Helicobacter pylori, have been implicated in person-to-person transmission. Based on these reports, we develop a hypothesis regarding dysbiotic microbiota-associated NCDs, and explore how the presence of communicable NCDs could be confirmedexperimentally. We have also reviewed reports on environmental factors, including a high-fat diet, alcohol, smoking, exercise, radiation and air pollution, which have been associated with dysbiotic microbiota, and determined whether any of these parameters were also associated with NCDs. This review discusses the potential mechanism by which dysbiotic microbiota induced by environmental factors are directly or indirectly involved in person-to-person transmission. The hypothetical interplay between the environment, gut microbiota and host can be tested through high-throughput sequencing, animal models, and cell studies, although each of these modalities presents specific challenges. Confirmation of a causative association of dysbiotic microbiota with NCDs would represent a paradigm shift in efforts to prevent and control these diseases, and should stimulate additional studies on the associations among environmental factors, gut microbiota, and NCDs.

Oral P. gingivalis impairs gut permeability and mediates immune responses associated with neurodegeneration in LRRK2 R1441G mice

Background

The R1441G mutation in the leucine-rich repeat kinase 2 (LRRK2) gene results in late-onset Parkinson’s disease (PD). Peripheral inflammation and gut microbiota are closely associated with the pathogenesis of PD. Chronic periodontitis is a common type of peripheral inflammation, which is associated with PD. Porphyromonas gingivalis (Pg), the most common bacterium causing chronic periodontitis, can cause alteration of gut microbiota. It is not known whether Pg-induced dysbiosis plays a role in the pathophysiology of PD.

Methods

In this study, live Pg were orally administrated to animals, three times a week for 1 month. Pg-derived lipopolysaccharide (LPS) was used to stimulate mononuclear cells in vitro. The effects of oral Pg administration on the gut and brain were evaluated through behaviors, morphology, and cytokine expression.

Results

Dopaminergic neurons in the substantia nigra were reduced, and activated microglial cells were increased in R1441G mice given oral Pg. In addition, an increase in mRNA expression of tumor necrosis factor (TNF-α) and interleukin-1β (IL-1β) as well as protein level of α-synuclein together with a decrease in zonula occludens-1 (Zo-1) was detected in the colon in Pg-treated R1441G mice. Furthermore, serum interleukin-17A (IL-17A) and brain IL-17 receptor A (IL-17RA) were increased in Pg-treated R1441G mice.

Conclusions

These findings suggest that oral Pg-induced inflammation may play an important role in the pathophysiology of LRRK2-associated PD.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12974-020-02027-5.

Porphyromonas gingivalis and Its Systemic Impact: Current Status

The relationship between periodontitis and systemic diseases, notably including atherosclerosis and diabetes, has been studied for several years. Porphyromonas gingivalis, a prominent component of oral microorganism communities, is the main pathogen that causes periodontitis. As a result of the extensive analysis of this organism, the evidence of its connection to systemic diseases has become more apparent over the last decade. A significant amount of research has explored the role of Porphyromonas gingivalis in atherosclerosis, Alzheimer's disease, rheumatoid arthritis, diabetes, and adverse pregnancy outcomes, while relatively few studies have examined its contribution to respiratory diseases, nonalcoholic fatty liver disease, and depression. Here, we provide an overview of the current state of knowledge about Porphyromonas gingivalis and its systemic impact in an aim to inform readers of the existing epidemiological evidence and the most recent preclinical studies. Additionally, the possible mechanisms by which Porphyromonas gingivalis is involved in the onset or exacerbation of diseases, together with its effects on systemic health, are covered. Although a few results remain controversial, it is now evident that Porphyromonas gingivalis should be regarded as a modifiable factor for several diseases.

Peripheral T helper cell profiles during management of periodontitis

AIM

Periodontitis has been associated with other systemic diseases with underlying inflammation responsible for the shared link. This study evaluated longitudinal variation in peripheral T helper cells in periodontitis patients undergoing management over 1 year.

MATERIALS AND METHODS

Periodontal parameters and peripheral blood mononuclear cells (PBMCs) were collected from 54 periodontitis patients at baseline, and 3-, 6- and 12-months post-treatment and 40 healthy controls. IFN-γ⁺ , IL-4⁺ , IL-17⁺ and Foxp3⁺ and their double-positive expression were identified in CD4⁺ and TCRαβ⁺ cells using flow cytometry. PBMCs were incubated with P. gingivalis, and IFN-γ, IL-4, IL-17 and IL-10 in cell supernatant were measured by ELISA. Cells and cytokines were also assessed based on clinical response to treatment where good (<10% of sites), moderate (10-20%) and poor (>20%) treatment outcome (TxO) groups had probing depths of ≥5 mm at study conclusion.

RESULTS

IFN-γ⁺ cells were lower at baseline, and 3- and 6-months compared to health, whereas Foxp3⁺ cells were increased at 12-months compared to all preceding timepoints and health. The good TxO group showed treatment-related variation in IFN-γ⁺ and Foxp3⁺ cells, whereas the poor TxO group did not. IFN-γ and IL-17 cytokine expression in cell supernatants was significantly lower at baseline compared to health, and IFN-γ and IL-10 showed treatment-related decrease.

CONCLUSION

This study suggests that IFN-γ⁺ and Foxp3⁺ cells may have a role in the systemic compartment in periodontitis. Periodontal management has local and systemic effects, and thus, assessment and management of periodontitis should form an integral part of overall systemic health.

Alteration of salivary microbiome in periodontitis with or without type-2 diabetes mellitus and metformin treatment

We aimed to explore the effects of type-2 diabetes mellitus (T2DM) and hypoglycemic therapy on the salivary microbiome in periodontitis patients and identify the potential salivary micro-biomarker for the early warning of T2DM. Saliva samples were collected from healthy individuals (Health), periodontitis patients (P), T2DM patients, periodontitis patients with T2DM (DAP), and DAP patients treated with Metformin (Met). Samples were determined by16S rRNA gene sequencing. 29 phyla, 322 genera, and 333 species of salivary microbiome were annotated. Compared to the Health group, the P and DAP group showed a significantly higher diversity of saliva microbiota, while the T2DM and Met group had no significant difference in microbial abundance but showed a trend of increasing diversity. Other than well-known periodontitis-inducing pathogens, the proportion of Prevotella copri, Alloprevotella rava, and Ralstonia pickettii, etc. were also significantly increased in periodontitis patients with or without T2DM. After effective glycemic control, the abundance of Prevotella copri, Alloprevotella rava, Ralstonia pickettii, etc. decreased in periodontitis patients with companion T2DM. The accuracies of the classification models in differentiating Health-vs.-P, DAP-vs.-P, and T2DM-vs.-P were 100%, 96.3%, and 98.1%, respectively. Hypoglycemic therapy could reconstruct the saliva microbiota and hence improve the localized conditions of diabetes patients with periodontitis.

Intracellular Porphyromonas gingivalis Promotes the Tumorigenic Behavior of Pancreatic Carcinoma Cells

Porphyromonas gingivalis is a member of the dysbiotic oral microbiome associated with oral inflammation and periodontal disease. Intriguingly, epidemiological studies link P. gingivalis to an increased risk of pancreatic cancer. Given that oral bacteria are detected in human pancreatic cancer, and both mouse and human pancreata harbor microbiota, we explored the involvement of P. gingivalis in pancreatic tumorigenesis using cell lines and a xenograft model. Live P. gingivalis induced proliferation of pancreatic cancer cells; however, surprisingly, this effect was independent of Toll-like receptor 2, the innate immune receptor that is engaged in response to P. gingivalis on other cancer and immune cells, and is required for P. gingivalis to induce alveolar bone resorption. Instead, we found that P. gingivalis survives inside pancreatic cancer cells, a trait that can be enhanced in vitro and is increased by hypoxia, a central characteristic of pancreatic cancer. Increased tumor cell proliferation was related to the degree of intracellular persistence, and infection of tumor cells with P. gingivalis led to enhanced growth in vivo. To the best of our knowledge, this study is the first to demonstrate the direct effect of exposure to P. gingivalis on the tumorigenic behavior of pancreatic cancer cell lines. Our findings shed light on potential mechanisms underlying the pancreatic cancer–periodontitis link.

Association between the gut and oral microbiome with obesity

In recent decades, obesity has become one of the most common lifestyle-associated disorders. Obesity is a major contributing factor for several other lifestyles associated disorders such as type 2 diabetes mellitus, hypertension, and cardiovascular disease. Although genetics and lifestyle have been directly implicated in the onset and progression of obesity, recent studies have established that gut microbiome plays a crucial role in obesity progression. A higher proportion of Firmicutes and a skewed Firmicutes/Bacteroidetes ratio may contribute to gut dysbiosis and subsequent disturbances in the overall body metabolisms. Like gut microbiome, the oral cavity of humans also harbors a characteristic microbial population called "oral microbiome". The oral microbiome has also been implicated in the development of obesity due to its modulating effects on the gut microbiome. Due to its critical role in obesity, alteration in the gut microbiome has been suggested as one of the therapeutic strategies to manage obesity itself. For example, fecal microbiome transfer, or the use of probiotics and prebiotics have been suggested. These therapies not only restore the gut microbiome to the "pre-obese stage" but also ameliorate many functional aspects of the metabolic syndrome such as systemic inflammation, insulin resistance, and fat accumulation. However, the efficacy and safety of some of the methods have not been tested for their long-term implications, and further research in this area is warranted to understand the molecular mechanisms involved in this process completely.

Periodontal Disease, Tooth Loss, and Risk of Serrated Polyps and Conventional Adenomas

Growing data indicate an association between periodontal disease and the development of cancer. However, the evidence for colorectal cancer has been inconsistent and longitudinal study examining its precursor lesions is lacking. We prospectively collected information on periodontal disease and number of tooth loss in the Nurses' Health Study (1992-2002) and the Health Professionals Follow-up Study (1992-2010). Polyp diagnosis was acquired via self-reported questionnaires and confirmed through review of medical records. We used logistic regression to calculate the multivariate-adjusted ORs and 95% confidence intervals (CI) with adjustment for smoking and other known risk factors for periodontal disease and colorectal cancer. In this study, we included 17,904 women and 24,582 men. We documented 2,336 cases of serrated polyps and 4,102 cases of conventional adenomas among 84,714 person-endoscopies throughout follow-up. The ORs of serrated polyps and conventional adenomas comparing individuals with and without periodontal disease were 1.17 (95% CI, 1.06-1.29) and 1.11 (95% CI, 1.02-1.19), respectively. Compared with participants without tooth loss, those who lost ≥4 teeth had 20% (OR, 1.20; 95% CI, 1.03-1.39) greater risk of serrated polyps (P trend 0.01). Among never smokers, similar associations with periodontal disease were observed for both serrated polyps (OR, 1.20; 95% CI, 1.02-1.41) and conventional adenomas (OR, 1.12; 95% CI, 1.00-1.26). History of periodontal disease and possibly higher number of tooth loss may modestly increase the risk of developing colorectal precursor lesions. Our findings advance our understanding of the interplay between oral health, microbiome, and early colorectal carcinogenesis.

The association of periodontal diseases with metabolic syndrome and obesity

Periodontitis is a multifactorial chronic inflammatory disease associated with dysbiotic plaque biofilms and characterized by progressive destruction of the tooth-supporting apparatus. Globally, it is estimated that 740 million people are affected by its severe form. Periodontitis has been suggested to be linked to obesity and metabolic syndrome. Obesity, defined as excessive fat accumulation, is a complex multifactorial chronic inflammatory disease, with a high and increasing prevalence. Metabolic syndrome is defined as a cluster of obesity, dyslipidemia, hypertension, and dysglycemia. Obesity, metabolic syndrome and periodontitis are among the most common non-communicable diseases and a large body of evidence from epidemiologic studies supports the association between these conditions. Extensive research has established plausible mechanisms to explain how these conditions can negatively impact each other, pointing to a bidirectional adverse relationship. At present there is only limited evidence available from a few intervention studies. Nevertheless, the global burden of periodontitis combined with the obesity epidemic has important clinical and public health implications for the dental team. In accordance with the common risk factor approach for tackling non-communicable diseases, it has been proposed that oral healthcare professionals have an important role in the promotion of periodontal health and general well-being through facilitation of healthy lifestyle behaviours.

Gender-associated differences in oral microbiota and salivary biochemical parameters in response to feeding

Saliva plays a key role in food absorption and digestion mainly due to both its enzymes and microbiota. The main objective of this study was to compare the oral microbiota and salivary parameters between men and women in response to feeding. To answer this question, we set up a pilot study on 10 male and 10 female subjects to examine the role of saliva in glycaemia physiology. Biological parameters and the microbiotal composition of saliva were analyzed in fasted and fed states. The results show that the level of blood glucose was not different between men and women in the fasted state (88.00 mg/dL ± 6.38 vs 87.00 mg/dL ±8.07, p = 0.9149) or in the fed state (102.44 mg/dL ± 14.03 vs 116.9 mg/dL ± 25, p = 0.1362). Free fatty acids (FFA 0.15 mmol/L ± 0.15 vs 0.07 mmol/L ± 0.07, p = 0,0078), cholesterol (0.53 mmol/L ± 0.30 vs 0.15 mmol/L ± 0.14, p < 0.0001), and total saliva proteins (13.2 g/L ± 4.31 vs 9.02 g/L ± 6.98, p = 0.0168) were decreased after feeding, as well as the saliva lipase (27.89 U/L ± 25.7 vs 12.28 U/L ± 4.85, p = 0.0126). A very significant increase in the relative abundance of Streptococcaceae (24.56 ± 9.32 vs 13.53 ± 7.47, p = 0.00055) and a decrease in Prevotellaceae (34.45 ± 9.30 vs 17.43 ± 9.03, p = 0.00055) were observed in the fed condition. When investigating gender-related differences in the fasted state, men showed higher levels of cholesterol (0.71 mmol/L ± 0.26 vs 0.40 mmol/L ± 0.27, p = 0.0329), FFA (0.25 mmol/L ± 0.18 vs 0.08 mmol/L ± 0.06, p = 0.0049), and triglycerides (0.24 mmol/L ± 0.15 vs 0.09 mmol/L ± 0.04, p = 0.006) than women. Finally, differences could be observed in saliva microbiota between men and women in the fasted condition but even more in the fed condition, where Porphyromonas and Capnocytophaga were overrepresented in the male salivary samples compared with female saliva. Thus, biological parameters and microbiota in saliva could be the signatures of the feeding conditions and sex gender status.

Virulence mechanisms used in the pathogenesis of periodontal diseases caused by Porphyromonas gingivalis

Periodontal diseases are characterized by progressive inflammation that destroys the tooth-supporting tissues, leading to gum bleeding and tooth loss. Porphyromonas gingivalis is considered one of the main etiological agents responsible for the initiation and progression of chronic periodontitis. This gram-negative, anaerobic bacterium is a part of a multi-species oral biofilm. P. gingivalis does not have the full pathway of protoporphyrin IX synthesis, nor does it produce siderophores. Therefore, for survival and proliferation, it requires heme as a source of iron and protoporphyrin IX. In order to obtain heme, P. gingivalis uses a number of mechanisms that affect the ability of this bacterium to initiate a pathological condition. This review presents the current knowledge regarding the best-known and characterized systems involved in heme acquisition by P. gingivalis. We focused on processes occurring in the initial states of infection, where gingipain, hemagglutinins, and hemolysins play a crucial role. The mechanisms encoded by hmu, iht and hus operons, including proteins with hemophore-like properties, as well as TonB-dependent outer membrane receptors are described. We present their function and participation in the progression of the infection. In addition, we describe mechanisms produced by P. gingivalis and other periodontopathogens in synergistic processes promoting the growth and virulence of P. gingivalis. We also describe processes regulating iron and heme homeostasis, including the homolog of the Fur protein, the two-component system HaeSR, as well as the OxyR, SigH, and PgDps proteins.

Effect of VEGFC on lymph flow and inflammation-induced alveolar bone loss

The lymphatic system plays a crucial role in the maintenance of tissue fluid homeostasis and the immunological response to inflammation. The effects of lymphatic drainage dysfunction on periodontitis have not been well studied. Here we show that lymphatic vessel endothelial receptor 1 (LYVE1)+ /podoplanin (PDPN)+ lymphatic vessels (LVs) are increased in the periodontal tissues, with accumulation close to the alveolar bone surface, in two murine periodontitis models: rheumatoid arthritis (RA)-associated periodontitis and ligature-induced periodontitis. Further, PDPN+ /alpha-smooth muscle actin (αSMA)- lymphatic capillaries are increased, whereas PDPN+ /αSMA+ collecting LVs are decreased significantly in the inflamed periodontal tissues. Both mouse models of periodontitis have delayed lymph flow in periodontal tissues, increased TRAP-positive osteoclasts, and significant alveolar bone loss. Importantly, the local administration of adeno-associated virus for vascular endothelial growth factor C, the major growth factor that promotes lymphangiogenesis, increases the area and number of PDPN+ /αSMA+ collecting LVs, promotes local lymphatic drainage, and reduces alveolar bone loss in both models of periodontitis. Lastly, LYVE1+ /αSMA- lymphatic capillaries are increased, whereas LYVE1+ /αSMA+ collecting LVs are decreased significantly in gingival tissues of patients with chronic periodontitis compared with those of clinically healthy controls. Thus, our findings reveal an important role of local lymphatic drainage in periodontal inflammation-mediated alveolar bone loss. © 2020 Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.