Upregulated Leptin in Periodontitis Promotes Inflammatory Cytokine Expression in Periodontal Ligament Cells

The relationship between leptin and periodontitis: a literature review

Leptin is a peptide hormone that regulates energy balance, immune inflammatory response, and bone metabolism. Several studies have demonstrated a relationship between leptin and periodontitis, a local inflammatory disease that progressively weakens the supporting structures of the teeth, eventually leading to tooth loss. This article reviews the existing literature and discusses leptin's basic characteristics, its relationship with periodontitis, and its effects on periodontal tissue metabolism.

Association between oral infections, triglyceride-glucose index, and in-stent restenosis

OBJECTIVES

To investigate oral infections in patients suffering in-stent restenosis (ISR) and non-ISR and analyze the possible correlation between the oral infection and triglyceride-glucose (TyG) index, a clinical surrogate indicator of insulin resistance (IR).

MATERIALS AND METHODS

A cross-sectional design was used, in which 586 patients with acute coronary syndrome who underwent coronary angiography 6-24 months after coronary stent implantation were recruited. The modified total dental index (TDI) was used to evaluate the status of oral inflammation.

RESULTS

In both univariate analyses, TDI scores [3 (1.5, 4.5) vs. 2.5 (1.5, 4.0), p < 0.01] and a multivariate regression model (OR = 1.202, 95% CI = 1.085-1.333, p < 0.01), the TDI significantly correlated with ISR. The TyG index was positively associated with ISR (OR = 1.766, 95% CI = 1.055-2.957, p < 0.05). Correlation analysis showed that TDI was positively correlated with TyG index (r = 0.190, p < 0.01). Using linear regression analysis, higher TDI scores were significantly associated with IR (95% CI = 0.029-0.063, p < 0.01).

CONCLUSIONS

Oral infections and TyG index were independently and positively correlated with ISR in patients with acute coronary syndrome. Oral inflammatory burden assessed by TDI score was associated with IR.

Leptin in Dental Pulp and Periapical Tissues: A Narrative Review

Leptin is a non-glycosylated 16 kDa protein synthesized mainly in adipose cells. The main function of leptin is to regulate energy homeostasis and weight control in a central manner. There is increasing evidence that leptin also has systemic effects, acting as a link between innate and acquired immune responses. The expression of leptin and its receptor in human dental pulp and periradicular tissues have already been described, as well as several stimulatory effects of leptin protein expression in dental and periodontal tissues. The aim of this paper was to review and to compile the reported scientific literature on the role and effects of leptin in the dental pulp and periapical tissues. Twelve articles accomplished the inclusion criteria, and a comprehensive narrative review was carried out. Review of the available scientific literature concluded that leptin has the following effects on pulpal and periapical physiology: 1) Stimulates odontogenic differentiation of dental pulp stem cells (DPSCs), 2) Increases the expression of dentin sialophosphoprotein (DSPP) and dentin matrix protein-1 (DMP-1), odontoblastic proteins involved in odontoblastic differentiation and dentin mineralization, 3) Stimulates vascular endothelial growth factor (VEGF) expression in human dental pulp tissue and primary cultured cells of human dental pulp (hDPCs), 4) Stimulates angiogenesis in rat dental pulp cells, and 5) Induces the expression of interleucinas 6 and 8 in human periodontal ligament cells (hPDLCs). There is evidence which suggests that leptin is implicated in the dentin mineralization process and in pulpal and periapical inflammatory and reparative responses.

Role of nonsurgical periodontal therapy on leptin levels and total antioxidant capacity in chronic generalised periodontitis patients - A clinical trial

Introduction

Periodontitis causes oxidative stress and reduce total antioxidant levels. The aim of this study was to determine the effect of non-surgical periodontal treatment on leptin levels and total antioxidant capacity in chronic periodontitis.

Materials and methods

A total of 35 chronic periodontitis (ChP) patients and 35 systemically and periodontal healthy subjects were enrolled in this study. Further, the ChP group received nonsurgical periodontal therapy (NSPT). Leptin and total antioxidant capacity (TAOC) was measured in serum and saliva samples at baseline, 3 months and 6 months after non-surgical periodontal therapy. Clinical parameters measured were measured at baseline, 1, 3 and 6 months interval.

Results

The mean serum leptin and TAOC levels in control group were significantly higher compared to chronic periodontitis group (p < 0.05). The control group had lower mean salivary leptin levels and higher mean salivary TAOC levels as compared to periodontitis group(p < 0.05). Clinical parameters were improved in ChP group post therapy (p < 0.05). However, the periodontal treatment showed insignificant changes in serum and salivary leptin and TAOC levels.

Conclusion

Chronic periodontitis is significantly associated with serum and salivary TAOC and leptin levels. Non surgical periodontal therapy didn't alter the local and systemic TAOC and leptin levels.

[Expression and distribution of calprotectin in healthy and inflamed periodontal tissues]

OBJECTIVE

Calprotectin, the heterdimer of S100A8 and S100A9, is the major cytoplasmic protein of neutrophils, which is also expressed or induced in gingival epithelial cells, activated mononuclear macrophages and vascular endothelial cells. Calprotectin is intimately associated with the initiation and progression of periodontitis, but the in vivo expression patterns of calprotectin in healthy and inflamed periodontal tissue are not fully understood. To observe the expression, distribution and cellular localization of calprotectin in the samples of healthy periodontal tissues and experimental periodontitis tissues of Beagles and to explore their relationship with periodontal inflammation and possible effect.

METHODS

Experimental periodontitis model was established by ligation around the mandibular second molar of the Beagle dogs, while the contralateral teeth were healthy controls. Induction duration was 12 weeks, before the dogs were executed. Tissue specimens were demineralized and serial sections were made conventionally. The in vivo expression of calprotectin in the healthy and inflamed periodontal tissues were examined by immunohistochemistry. The in vitro expression of calprotectin in human primary gingival fibroblasts (GFs) and periodontal ligament (PDL) cells were detected by immunocytochemistry.

RESULTS

Immunohistochemistry analysis indicated that calprotectin was expressed in gingival epithelial cells and infiltrated neutrophils in the healthy periodontium within the gingival epithelium, S100A8/A9 was most strongly expressed in the junctional epithelium, followed by surface epithelium, and least expressed in the sulcular epithelium. The S100A8/A9 expression levels were sharply defined at the junction between the junctional epithelium and the sulcular epithelium. In periodontal inflammatory lesions, the expression level of calprotectin in sulcular epithelium and junctional epithelium was up-regulated than that in the healthy gingival epithelium. Calprotectin was inducibly expressed in fibroblast-like cells in gingival connective tissue and periodontal ligament tissue, microvascular endothelial cells (ECs) and bone marrow fibroblasts under inflammatory conditions. Additionally, the expression of calprotectin in primary human GFs and PDL cells was confirmed by immunnocytochemistry staining.

CONCLUSION

Constitutively expressed in neutrophils and gingival epithelial cells, and calprotectin might maintain the homeostasis and integrity of periodontium. Inflammation-induced expression of calprotectin in GFs, PDL cells, microvascular ECs and bone marrow fibroblasts might process anti-microbial function and promote leukocytes transmigration to defend the host against the microorganisms.

Breast Cancer and Microcalcifications: An Osteoimmunological Disorder?

The presence of microcalcifications in the breast microenvironment, combined with the growing evidences of the possible presence of osteoblast-like or osteoclast-like cells in the breast, suggest the existence of active processes of calcification in the breast tissue during a woman’s life. Furthermore, much evidence that osteoimmunological disorders, such as osteoarthritis, rheumatoid arthritis, or periodontitis influence the risk of developing breast cancer in women exists and vice versa. Antiresorptive drugs benefits on breast cancer incidence and progression have been reported in the past decades. More recently, biological agents targeting pro-inflammatory cytokines used against rheumatoid arthritis also demonstrated benefits against breast cancer cell lines proliferation, viability, and migratory abilities, both in vitro and in vivo in xenografted mice. Hence, it is tempting to hypothesize that breast carcinogenesis should be considered as a potential osteoimmunological disorder. In this review, we compare microenvironments and molecular characteristics in the most frequent osteoimmunological disorders with major events occurring in a woman’s breast during her lifetime. We also highlight what the use of bone anabolic drugs, antiresorptive, and biological agents targeting pro-inflammatory cytokines against breast cancer can teach us.

Relationship between Apical Periodontitis and Metabolic Syndrome and Cardiovascular Events: A Cross-Sectional Study

Aim: Both apical periodontitis (AP) and metabolic syndrome (MetS) are associated with atherosclerotic cardiovascular disease (ACVD), the main cause of cardiovascular events. The aim of this study was to investigate the prevalence of AP and the oral inflammatory burden in control subjects and patients suffering cardiovascular events, analyzing the possible association between AP and the oral inflammatory burden with MetS. Materials and Methods: Using a cross-sectional design, 83 patients suffering a cardiovascular event were recruited in the study group (SG), and 48 patients without cardiovascular events were included in the control group (CG). Periapical index (PAI) was used to diagnose AP, and total dental index (TDI) was used to assess the total oral inflammatory burden. Diagnosis of MetS was made by meeting three or more American Heart Association Scientific Statement components. Results: In the multivariate logistic regression analysis, the number of teeth with AP (OR = 2.3; 95% C.I. = 1.3–4.3; p = 0.006) and TDI scores (OR = 1.5; 95% C.I. = 1.2–1.9; p = 0.001), significantly correlated with cardiovascular events. MetS was strongly associated (OR = 18.0; 95% C.I. = 6.5–49.7; p = 0000) with cardiovascular events. Higher TDI scores were significantly associated with MetS (OR = 1.3; 95% C.I. = 1.1–1.6; p = 0.003. Neither the number of root-filled teeth (RFT) (OR = 0.9; 95% C.I. = 0.6–1.3; p = 0.61) nor the number of teeth with apical periodontitis (OR = 1.1; 95% C.I. = 0.8–1.7; p = 0.49) were associated with MetS. Conclusions: Apical periodontitis is significantly associated with cardiovascular events. Total oral inflammatory burden assessed by TDI, but not AP alone, is associated with MetS.

Leptin reduces in vitro cementoblast mineralization and survival as well as induces PGE2 release by ERK1/2 commitment

Objectives

Juvenile obesity is a complex clinical condition that is present more and more frequently in the daily orthodontic practice. Over-weighted patients have an impaired bone metabolism, due in part to their increased levels of circulating adipokines. Particularly, leptin has been reported to play a key role in bone physiology. Leptin is ubiquitously present in the body, including blood, saliva, and crevicular fluid. If, and to what extent, it could influence the reaction of cementoblasts during orthodontic-induced forces is yet unknown.

Material and methods

OCCM-30 cementoblasts were cultivated under compressive forces using different concentrations of leptin. The expression of ObR, Runx-2, Osteocalcin, Rank-L, Sost, Caspase 3, 8, and 9 were analyzed by RT-PCR. Western blots were employed for protein analysis. The ERK1/2 antagonist FR180204 (Calbiochem) was used and cPLA2 activation, PGE2, and cytochrome C release were further evaluated.

Results

In vitro, when compressive forces are applied, leptin promotes ERK1/2 phosphorylation, as well as upregulates PGE2 and caspase 3 and caspase 9 on OCCM cells. Blockade of ERK1/2 impairs leptin-induced PGE2 secretion and reduced caspase 3 and caspase 9 expression.

Conclusions

Leptin influences the physiological effect of compressive forces on cementoblasts, exerting in vitro a pro-inflammatory and pro-apoptotic effect.

Clinical relevance

Our findings indicate that leptin exacerbates the physiological effect of compressive forces on cementoblasts promoting the release of PGE2 and increases the rate of cell apoptosis, and thus, increased levels of leptin may influence the inflammatory response during orthodontically induced tooth movement.

Analysis of leptin concentrations in oral fluids (saliva and crevicular gingival fluid) and blood in patients with chronic periodontal disease: systematic review of literature

Objective: The objective of this systematic analysis was to perform a qualitative and quantitative synthesis of the literature concerning salivary and serum leptin variations in patients with chronic periodontitis (CP) compared with healthy subjects. Saliva leptin concentration analysis could be a relevant and non-invasive biological test for the evaluation of periodontal disease in both medical and clinical trials, beyond the clinical and radiographic elements. Material and Method: Querying the PubMed and Web of Science databases identified articles that met our inclusion criteria. Quantitative analysis of the literature data was performed with the Review Manager 5.3 software. Results: The qualitative analysis included 14 articles and showed a decrease of salivary leptin (5 studies out of 5) and an increase of serum leptin (11 of 12 studies) in patients with CP compared to unaffected subjects of CP. Quantitative analysis was performed on 4 trials. For salivary leptin, we confirmed a decrease in its level in patients with CP with a standardized mean difference (SMD) of −2.27, 95% CI [−2.68, −1.86]. The difference was highly significant but we detected a very important heterogeneity in this dataset (I2 = 94%). For serum leptin, we also confirmed an increase in its rate in patients with CP with an SMD of 2.18, 95% CI [1.75, 2.61]. The difference was highly significant but the heterogeneity measured in this dataset was also too high (I2 = 95%). Conclusion: The current level of evidence was insufficient to assert an increase in serum leptin and a decrease in salivary leptin in CP patients compared to healthy controls due to a great heterogeneity of the values measured in the studies.

MicroRNA-153 promotes brain-derived neurotrophic factor and hippocampal neuron proliferation to alleviate autism symptoms through inhibition of JAK-STAT pathway by LEPR

Autism is known as a severe neurobehavioral syndrome, with males affected more often than females. Previous studies have revealed that microRNAs (miRNAs) play a critical role in the search for novel therapeutic strategies for autism. Therefore, we evaluate the ability of miR-153 to influence brain-derived neurotrophic factor (BDNF) of autism as well as proliferation and apoptosis of hippocampal neuron through the janus kinase-signal transducer and activator of transcription (JAK-STAT) signaling pathway by targeting leptin receptor (LEPR). Firstly, the autistic mice models were established and Morris water maze was employed for the analysis of the learning ability and memory of the mice. Besides, in vitro experiments were conducted with the transfection of different mimic, inhibitor, or siRNA into the hippocampal neuron cells, after which the effect of miR-153 on LEPR and the JAK-STAT signaling pathway-related factors was investigated. Next, 3-[4,5-dimethylthiazol-2-yl]-2,5 diphenyl tetrazolium bromide assay and flow cytometry assay were conducted to evaluate cell proliferation, cell cycle, and apoptosis respectively following transfection. The results revealed that there was a significant decrease in learning ability and memory in the autistic mice along with a reduction in the positive expression rate of BDNF and serious inflammatory reaction. LEPR was confirmed as a target gene of miR-153 by the dual luciferase reporter gene assay. After transfection of overexpressed miR-153, LEPR and the JAK-STAT signaling pathway were inhibited followed by an increase in BDNF and enhancement of cell proliferation. In conclusion, the high expression of miR-153 can inhibit activation of JAK-STAT signaling pathway by LEPR, thus improving BDNF expression and the proliferative ability of hippocampal neurons.

Evaluation of Systemic Inflammation Parameters in Dogs with Periodontitis

Periodontal diseases are the most common diseases in veterinary medicine. The first clinical finding is chewing difficulty, saliva flow and bad oral odor. It further develops into plaque and tartar formation, gingival inflammation and hemorrhagic appearance of the gingiva, periodontal pockets formation, alveolar bone resorption and tooth loss.

In this study an evaluation has been made to determine which degree reflects on the parameters of systemic inflammatory reaction with special attention to IL-6 (Interleukine-6), CRP (C-reactive protein), osteopontin, superoxide dismutase (SOD), malondialdehyde (MDA), glutathione peroxidase (GPx) and Ig (Immunglobulins = Total protein – Albumin) and hematological parameters in dogs with periodontitis.

Two groups have been defined in this study. The first group included 10 healthy and owned dogs as a control group. The second group consisted of 10 owned dogs with moderate-severe periodontitis.

The difference between monocyte (p <0.001) and neutrophil (p <0.05) counts was found to be significant. In addition, the difference between SOD, MDA, glutathione peroxidase, CRP, IL-6 measurements in group 1 and group 2 was significant. (p <0.001). The level of osteopontin in moderate-severe periodontitis cases was found significantly higher than the level measured in the healthy group.

Measured values in the moderate-severe periodontitis cases are higher than the healthy group in terms of CRP, IL-6, and osteopontin levels. Increasing severity of periodontitis was associated with changes in oxidative stress parameters: increased MDA, decreased SOD and glutathione peroxidase levels. These differences provide important information about the evaluation of the cellular responses. There is a need for continued research into the systemic impact of periodontal disease.

Interactions among moderate/severe periodontitis, ADIPOQ-rs1501299, and LEPR-rs1137100 polymorphisms on the risk of type 2 diabetes in a Chinese population

OBJECTIVE

Type 2 diabetes mellitus (T2DM) is a complex disease influenced by genes and the environment. Periodontitis a demonstrated risk factor of T2DM. Previous studies related to gene-environment interactions on the risk of T2DM mainly focused on gene-obesity interactions. However, the impact of gene-periodontitis interaction on the risk of T2DM has not yet been investigated. This study aimed to investigate gene-environment interactions among moderate/severe periodontitis, polymorphisms of adiponectin (ADIPOQ)-rs1501299, and leptin receptor (LEPR)-rs1137100 on T2DM risk in Chinese subjects.

DESIGN

A case-control study was conducted in 239 Chinese participants from Beijing Hypertension Association Institute (BHAL). After full-mouth periodontal examinations, the participants underwent bilateral buccal swabs for DNA testing. ADIPOQ-rs1501299 and LEPR-rs1137100 were used for genotyping. Generalised multifactor dimensionality reduction (GMDR) and logistic regression were used to examine the interactions among single nucleotide polymorphisms (SNPs) and moderate/severe periodontitis on the risk of T2DM.

RESULTS

The risk of T2DM was higher in moderate/severe periodontitis [adjusted odds ratio (AOR) = 3.67, 95% confidence interval (95%CI): 1.26-10.71] in ADIPOQ-rs1501299 GG genotype (AOR = 3.42, 95%CI: 1.81-6.46) and LEPR-rs1137100 GG genotype (AOR = 3.16, 95%CI: 1.56-6.39). The GMDR model indicated that there was a significant three-factor model (p = 0.001) involving rs1501299, rs1137100, and moderate/severe periodontitis, demonstrating a potential gene-environment interaction among periodontitis, polymorphisms of rs1501299, and rs1137100 influencing the risk of T2DM. Moderate/severe periodontitis patients with rs1501299-GG and rs1137100-GG have the highest T2DM risk after adjusting for age, gender, BMI, WHR, smoking status, alcohol consumption, economic status, and hypertension (AOR = 20.39, 95%CI: 2.64-157.26).

CONCLUSIONS

Interactions among moderate/severe periodontitis, rs1501299-GG, and rs1137100-GG were associated with an increased risk of T2DM. This study may provide a new insight into the effect of gene-environment interactions on T2DM.

Leptin induces IL-6 and IL-8 expression through leptin receptor Ob-Rb in human dental pulp fibroblasts

OBJECTIVE

Leptin, through binding to its special receptor (Ob-Rb), has potent effects on immunity and inflammation. This study aimed to investigate the expression of leptin receptor Ob-Rb in human dental pulp fibroblasts (HDPFs) and the effects of leptin on the production of proinflammatory cytokines of IL-6 and IL-8 by HDPFs.

METHODS

Ob-Rb expression was determined by quantitative real-time PCR (real-time PCR), Western blot and immunofluorescence analyses in cultured HDPFs. Small interfering RNA (siRNA) was transfected into HDPFs to down-regulate the expression of Ob-Rb. Real-time PCR and enzyme-linked immunosorbent assay (ELISA) were used to determine the proinflammatory cytokines of IL-6 and IL-8 levels in leptin-stimulated HDPFs. The involved signalling pathways that mediate the leptin-stimulated production of proinflammatory cytokines were investigated using Western blot and specific signalling inhibitor analyses.

RESULTS

The expression levels of Ob-Rb mRNA and protein were detected in HDPFs. Leptin could stimulate mRNA and protein expression of IL-6 and IL-8 in HDPFs in a concentration-dependent and time-dependent manner. Transfection with siRNA targeting Ob-Rb resulted in remarkable reduction of IL-6 and IL-8 expressions by HDPFs. In accordance with the enhanced expression of proinflammatory cytokines, leptin stimulation resulted in rapid phosphorylation of STAT3, p38 MAPK, ERK and Akt in HDPFs. Inhibiting JAK2/STAT3, p38 MAPK or PI3K/Akt substantially decreased leptin-induced IL-6 production, whereas blocking ERK and p38 MAPK substantially suppressed IL-8 production from leptin-stimulated HDPFs.

CONCLUSIONS

Leptin may up-regulate IL-6 and IL-8 production through binding with Ob-Rb in HDPFs via the activation of different intracellular signalling pathways.

ASK1-p38 cascaded signal mediates pulmonary microvascular endothelial barrier injury induced by the return of PHSML in rats

The return of post-hemorrhagic shock mesenteric lymph (PHSML) induces pulmonary vascular endothelial barrier dysfunction, which results in acute lung injury. Activation of the apoptosis signal-regulated kinase 1 (ASK1) and p38 mitogen-activated protein kinase (p38 MAPK) pathway has been shown to trigger inflammatory responses. However, whether the ASK1-p38 MAPK pathway is involved in the PHSML-induced pulmonary endothelial barrier dysfunction remains unclear. In the present study, permeability changes of pulmonary capillaries were found in vivo, and activation of the ASK1-p38 MAPK pathway was determined in vitro. PMVEC barrier dysfunction was determined by measuring TEER. Furthermore, junctional and cytoskeletal protein expressions were analyzed. The results showed that hemorrhagic shock led to a marked increase in the permeability of pulmonary capillaries in vivo, which was markedly alleviated by PHSML drainage. In cultured pulmonary microvascular endothelial cells (PMVECs), PHSML reduced the endothelial barrier function accompanied by upregulated p-ASK1 and p-p38 MAPK protein expression, impaired the cytoskeletal protein structure, and down-regulated junction protein expression. These adverse effects were eliminated by applying either Trx1 (ASK1 inhibitor) or SB203580 (p38 MAPK inhibitor). These results indicated that the ASK1-p38 MAPK pathway mediates PHSML-induced pulmonary vascular endothelial barrier dysfunction during hemorrhagic shock.

The return of post-hemorrhagic shock mesenteric lymph (PHSML) induces pulmonary vascular endothelial barrier dysfunction, which results in acute lung injury.

Association of circulating leptin and adiponectin with periodontitis: a systematic review and meta-analysis

BACKGROUND

This study aimed to assess the difference in serum levels of leptin and adiponectin in patients with periodontitis and in periodontally healthy individuals and evaluate the changes in circulating leptin and adiponectin after periodontal therapy. Leptin and adiponectin are the most generally studied adipokines that function as inflammatory cytokines. Although the association between periodontitis and serum levels of leptin and adiponectin has been studied extensively, the results were not consistent.

METHODS

A systematic search of the Pubmed, Embase, Web of Science, and Cochrane Library up to September 2016 was conducted. The studies were screened and selected by two writers according to the specific eligibility criteria. The quality of included cross-sectional studies was assessed using the quality assessment form recommended by the Agency for Healthcare Research and Quality and Methodological Index for Nonrandomized Studies. The meta-analyses were conducted using the STATA 12.0 software.

RESULTS

A total of 399 manuscripts were yielded and 25 studies were included in the present meta-analysis. Significantly elevated serum levels of leptin and decreased serum levels of adiponectin in patients with periodontitis were observed in the subgroup analysis of body mass index (BMI) <30. The overall and subgroup analyses showed no significant change in the serum levels of leptin in patients with periodontitis after periodontal treatment. The subgroup analysis of systemically healthy patients showed no significant change in serum levels of adiponectin in patients with periodontitis after periodontal treatment.

CONCLUSIONS

The present meta-analysis supported elevated serum levels of leptin and decreased serum levels of adiponectin in patients with periodontitis compared with controls in the BMI <30 population. In systemically healthy patients with periodontitis, serum levels of leptin and adiponectin do not significantly change after periodontal treatment.