Influence of periodontitis and scaling and root planing on insulin resistance and hepatic CD36 in obese rats

Chronic periodontitis induces the proliferation of pancreatic β-cells to cause hyperinsulinemia in a rat model

BACKGROUND AND OBJECTIVE

The purpose of this study was to determine if chronic periodontitis (CP) may induce hyperinsulinemia and may have the effect of on pancreatic β-cell proliferation in a rat model.

MATERIALS AND METHODS

Twelve male Sprague-Dawley rats were divided into two groups: the CP group and the control group (Con group). The following contents were evaluated: pathological changes in periodontal soft and hard tissues; serum lipopolysaccharide (LPS) level, serum fasting insulin (FINS) level, fasting blood glucose (FBG) level, and homeostasis model assessment (HOMA) β (HOMA-β) index; histopathological examination of islets; immunohistochemistry of insulin and p-Smad2 expression in islets; immunofluorescence of changes in the relative number of β-cells and the number of Ki67-positive β-cells. Western blotting was used to analyze p-Smad2/Smad2 levels. Results were analyzed by two independent samples t tests.

RESULTS

Increased serum LPS level, FINS level, and HOMA-β index were observed in the rats of the CP group; FBG level did not change significantly; histological assessments showed an enlarged islet area, increased insulin content, relatively increased β-cells, increased Ki67-positive β-cells, and decreased p-Smad2 expression in islets in the rats of the CP group.

CONCLUSION

Our study results link CP-induced hyperinsulinemia with changes in islets, such as islet hyperplasia and compensatory β-cell proliferation, by using a CP rat model.

Host insulin resistance caused by Porphyromonas gingivalis-review of recent progresses

Porphyromonas gingivalis (P. gingivalis) is a Gram-negative oral anaerobic bacterium that plays a key role in the pathogenesis of periodontitis. P. gingivalis expresses a variety of virulence factors that disrupt innate and adaptive immunity, allowing P. gingivalis to survive and multiply in the host and destroy periodontal tissue. In addition to periodontal disease, P.gingivalis is also associated with systemic diseases, of which insulin resistance is an important pathological basis. P. gingivalis causes a systemic inflammatory response, disrupts insulin signaling pathways, induces pancreatic β-cell hypofunction and reduced numbers, and causes decreased insulin sensitivity leading to insulin resistance (IR). In this paper, we systematically review the studies on the mechanism of insulin resistance induced by P. gingivalis, discuss the association between P. gingivalis and systemic diseases based on insulin resistance, and finally propose relevant therapeutic approaches. Overall, through a systematic review of the mechanisms related to systemic diseases caused by P. gingivalis through insulin resistance, we hope to provide new insights for future basic research and clinical interventions for related systemic diseases.

Periodontitis as a promoting factor of T2D: current evidence and mechanisms

Periodontitis is an infectious disease caused by an imbalance between the local microbiota and host immune response. Epidemiologically, periodontitis is closely related to the occurrence, development, and poor prognosis of T2D and is recognized as a potential risk factor for T2D. In recent years, increasing attention has been given to the role of the virulence factors produced by disorders of the subgingival microbiota in the pathological mechanism of T2D, including islet β-cell dysfunction and insulin resistance (IR). However, the related mechanisms have not been well summarized. This review highlights periodontitis-derived virulence factors, reviews how these stimuli directly or indirectly regulate islet β-cell dysfunction. The mechanisms by which IR is induced in insulin-targeting tissues (the liver, visceral adipose tissue, and skeletal muscle) are explained, clarifying the influence of periodontitis on the occurrence and development of T2D. In addition, the positive effects of periodontal therapy on T2D are overviewed. Finally, the limitations and prospects of the current research are discussed. In summary, periodontitis is worthy of attention as a promoting factor of T2D. Understanding on the effect of disseminated periodontitis-derived virulence factors on the T2D-related tissues and cells may provide new treatment options for reducing the risk of T2D associated with periodontitis.

The interplay between oral microbiota, gut microbiota and systematic diseases

Over the past two decades, the importance of microbiota in health and disease has become evident. The human gut microbiota and oral microbiota are the largest and second-largest microbiome in the human body, respectively, and they are physically connected as the oral cavity is the beginning of the digestive system. Emerging and exciting evidence has shown complex and important connections between gut microbiota and oral microbiota. The interplay of the two microbiomes may contribute to the pathological processes of many diseases, including diabetes, rheumatoid arthritis, nonalcoholic fatty liver disease, inflammatory bowel disease, pancreatic cancer, colorectal cancer, and so on. In this review, we discuss possible routes and factors of oral microbiota to affect gut microbiota, and the contribution of this interplay between oral and gut microbiota to systemic diseases. Although most studies are association studies, recently, there have been increasing mechanistic investigations. This review aims to enhance the interest in the connection between oral and gut microbiota, and shows the tangible impact of this connection on human health.

C-reactive protein perturbs alveolar bone homeostasis: an experimental study of periodontitis and diabetes in the rat

AIMS

To explore the role of C-reactive protein (CRP) in periodontitis and diabetes and its mechanism in alveolar bone homeostasis.

MATERIALS AND METHODS

In vivo, normal and Crp knockout rats were randomly divided into: control, diabetes, periodontitis, and diabetes and periodontitis (DP) groups respectively. The diabetes model was established using a high-fat diet combined with streptozotocin (STZ) injection. The periodontitis model was established by ligature combined with lipopolysaccharide injection. Alveolar bones were analyzed using microCT, histology, and immunohistochemistry. In vitro, human periodontal ligament cells (hPDLCs) were treated with lipopolysaccharide and high glucose. CRP knockdown lentivirus or CRP overexpression adenovirus combined with a PI3K/AKT signaling inhibitor or agonist were used to explore the regulatory mechanism of CRP in osteogenesis and osteoclastogenesis of hPDLCs, as evidenced by ALP staining, WB and qPCR.

RESULTS

In periodontitis and diabetes, CRP knockout decreased the alveolar bone loss and the expression levels of osteoclastogenic markers, while increasing the expression levels of osteogenic markers. CRP constrained osteogenesis while promoting the osteoclastogenesis of hPDLCs via PI3K/AKT signaling under high glucose and pro-inflammatory conditions.

CONCLUSIONS

CRP inhibits osteogenesis and promotes osteoclastogenesis via PI3K/AKT signaling under diabetic and pro-inflammatory conditions, thus perturbing alveolar bone homeostasis. This article is protected by copyright. All rights reserved.

Effects of periodontitis and periodontal treatment on systemic inflammatory markers and metabolic profile in obese and non-obese rats

BACKGROUND

Little is known about a synergistic effect of periodontitis and obesity on systemic biomarkers and a possible effect periodontal treatment may exert. This study aimed to evaluate the impact of periodontitis and periodontal treatment on systemic inflammation and metabolic profile in obese and non-obese rats.

METHODS

60 male Wistar rats were randomly divided in six groups differentiated by diet and periodontal status: no periodontitis (G1 and G4), untreated ligature-induced periodontitis (G2 and G5) and treated ligature-induced periodontitis (G3 and G6). Groups G4, G5 and G6 were exposed to cafeteria diet to induce obesity. Periodontitis was induced by silk ligatures over 4 weeks (G2, G3, G5, G6). Rats in G3 and G6 received scaling and root planning and were followed for additional 4 weeks. After sacrifice, serum levels of C-reactive protein (CRP), interleukin (IL)-1β, IL-6, IL-10, IL-17a, tumor necrosis factor alfa (TNF-α), glucose, triglycerides, and total cholesterol (TC) were compared between groups.

RESULTS

CRP was significantly higher in obese rats with than without periodontitis (G5 = 10.15μg/L vs. G4 = 4.47μg/L, p = 0.01). No beneficial effects of periodontal treatment were observed for CRP levels, IL-6, IL-1β, IL-17a, TNF-α, glucose and triglycerides. Treated periodontitis (G6) exhibited significantly lower TC than the periodontitis group (G5) in obese rats.

CONCLUSION

Periodontitis increased serum CRP in obese rats, indicating a synergistic role of periodontitis in the systemic inflammatory burden triggered by obesity. The treatment of induced periodontitis reduced TC levels in obese rats. This article is protected by copyright. All rights reserved.

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.

Ligature induced periodontitis in rats causes gut dysbiosis leading to hepatic injury through SCD1/AMPK signalling pathway

AIMS

Previous studies have demonstrated that chronic periodontitis (CP) is closely associated with the occurrence and development of a variety of systemic diseases. In this study, we successfully constructed a rat CP model through dental silk ligation, and the corresponding inflammatory reactions and fatty lesions were observed in the liver.

MAIN METHODS

Sprague-Dawley rats (n = 6) underwent tooth ligation at the bilateral first molars with silk thread to induce CP and were sacrificed 8 weeks later and compared to non-ligated rats (n = 6). RNA sequencing and 16S rRNA analysis were performed to determine the molecular mechanisms of CP involved in inducing liver disease. Alveolar bone loss, liver enzymes, mandible and liver histopathology, and inflammatory responses were compared between groups.

KEY FINDINGS

RNA sequencing of liver tissue showed that the expression of SCD1 increased significantly in CP rats compared to controls. KEGG enrichment analysis showed that the AMPK signalling pathway may be involved in liver steatosis. The intestinal flora of faecal samples of rats were analysed by 16S rRNA sequencing, and the results indicated that the intestinal flora of the CP group was evidently imbalanced. The expression levels of tight junction proteins (ZO-1, occludin, and claudin-1) were significantly reduced in CP rats. Meanwhile, increases in serum IL-1β and lipopolysaccharide in CP rats reflected a systemic inflammatory response.

SIGNIFICANCE

CP may be involved in the occurrence and development of hepatic injury and liver steatosis, and its mechanism may be related to the oral-gut-liver axis and SCD1/AMPK signal activation in the liver.

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.

Plaque control alleviated renal damage that was aggravated by experimental periodontitis in obese rats

OBJECTIVE

This study aimed to evaluate the influence of experimental periodontitis on renal damage in obese rats.

MATERIALS AND METHODS

Thirty-two male Sprague Dawley rats were randomly allocated into 4 groups with 8 animals each: obese rats (obese group), obese rats with periodontitis (periodontitis obese group), obese rats with periodontitis that underwent plaque control (plaque-control obese group), and healthy rats (healthy group). Rats were fed a high-fat diet to establish an obesity model. Experimental periodontitis was induced by local ligation with silk around the bilateral maxillary second molars. The plaque control was accomplished by removing ligations and local wiping with an antiseptic rinse. Histology was used to observe the gingival inflammation and clinical attachment level (CAL) to further assess bone loss and to also observe renal structure. Serum creatinine, urea nitrogen, and kidney injury molecule-1 (KIM-1) levels were measured to evaluate renal function. Renal Toll-like receptor 4 (TLR4), nuclear factor-kappa B (NF-κB), serum C-reactive protein (CRP), lipopolysaccharides (LPS), and interleukin-1β (IL-1β) were measured to evaluate renal and systemic inflammation.

RESULTS

Periodontal histology showed that in the periodontitis obese group, the epithelial barrier was considerably eroded by inflammatory cells, which infiltrated into the subepithelial connective tissue and lamina propria. A periodontal pocket was forming accompanied by the loss of attachment. The extent of infiltration of inflammatory cells and the CAL were significantly higher than those of the obese group (p < .001). In the plaque-control obese group, although the inflammatory condition was significantly improved than in the periodontitis obese group, the clinical attachment level with the presence of fiber hyperplasia could not be restored. Renal histology showed that renal tubular structural damage was aggravated in the periodontitis obese group, including vacuolar degeneration, exfoliation of the proximal tubular epithelial cell lining, multifocal loss of the brush border, and movement of several nuclei from the basement membrane to the lumen. These alterations were improved in the plaque-control obese group. Kidney TLR4 and NF-κB mRNA levels increased significantly in the periodontitis obese group compared to the obese group (p = .015 and p = .015, respectively) and decreased significantly in the plaque-control obese group (p = .028 and p = .021, respectively). Kidney TLR4 and NF-κB protein expression in the plaque-control obese group were significantly lower than those in the periodontitis obese group (p < .001 and p = .043, respectively). Serum creatinine and KIM-1 levels significantly decreased in the plaque-control obese group compared to the periodontitis obese group (p = .001 and p = .002, respectively). At 21 weeks (1 week after periodontal ligation), serum CRP levels in the periodontitis obese group were significantly higher than that in the healthy group (p = .017). Other serum inflammatory markers (LPS and IL-1β) did not change significantly.

CONCLUSION

Experimental periodontitis induced dysfunction and structural destruction of the kidney in obese rats. Plaque control relieved renal damage.

Effect of scaling and root planing on level of immunoglobulin E and immunoglobulin G4 in children with gingivitis and house-dust mite allergy: A pilot randomised controlled trial

Background and Objective: There is a pressing need for developing innovative strategies to prevent allergic diseases among children. As house-dust mite (HDM) allergy is often seen in children with gingivitis, strategies should be derived from a conceptual framework of allergen elimination and pathogen eradication; one such strategy is dental scaling and root planing (SRP) to remove dental plaque and periodontal pathogens. The study aimed to evaluate the beneficial effects of comprehensive 6-months dental SRP to reduce the level of immunoglobulin E (IgE) and immunoglobulin G₄ (IgG₄) in children with gingivitis and HDM allergy. IgE and IgG₄, whose production is controlled mainly by Th-2 cells and B cells, are proven biomarkers for atopic inflammatory responses. Methods: The present study conducted a non-blinded randomised controlled trial with superiority design. A total of 10 subjects (age range 6-16 years) with gingivitis and positive skin-prick test to HDM from Pediatric Allergy Outpatient Clinic, Dr. Soetomo General Hospital were enrolled in the present study. Of the 10 subjects, only five received dental SRP. We further evaluated total serum IgE and IgG₄ level before and 6 months after treatment. Results and Discussion: Subjects in the standard treatment group showed a slight decrease in the IgE level ([Formula: see text]) but no change in the IgG₄ level ([Formula: see text]), while subjects in the intervention group showed a significant decrease in IgE ([Formula: see text]) and IgG₄ levels ([Formula: see text]). Conclusion: The study results suggest that 6-month comprehensive dental scaling combined with root planing may help to reduce IgE and IgG₄ levels in children with gingivitis and HDM allergy. Furthermore, untreated or undertreated gingivitis is often associated with worsening allergic manifestation and thus should be avoided. Trial Registration: ISRCTN31416107, retrospectively registered on 17 April 2018.

[Expression of high mobility group protein B1 in periodontal tissues and its association with hepatic lipid metabolism in diabetic rats with periodontitis]

OBJECTIVE

To investigate the expression of high mobility group box-1 protein (HMGB1) and its downstream products, receptor for advanced glycation end-products (RAGE) and tumor necrosis factor-α (TNF-α), in periodontal tissues of diabetic rats with periodontitis, and explore the association of HMGB1 with hepatic lipid metabolism.

METHODS

Immunohistochemical staining was used to detect the expression of HMGB1, RAGE and TNF-α in the periodontal tissues in rat models of diabetes mellitus (DM), periodontitis (CP), and diabetic periodontitis (DM + CP). The serum levels of the indicators of lipid metabolism and biochemical indexes of liver damage were detected by spectroscopy.

RESULTS

The expressions of HMGB1 and RAGE in the periodontal tissues were significantly higher in DM group than in the control group, but the expression of TNF-α showed no significant difference among the groups. In CP group, the expressions of HMGB1 and TNF-α were significantly higher than those in the control group, and the expression of RAGE was comparable with that in the control group but significantly lower than that in DM and DM+CP group. The expressions of HMGB1, RAGE and TNF-α were all significantly higher in DM+CP group than in the control group. Compared with the control rats, the rats in DM, CP, DM+CP group all showed abnormal hepatic lipid metabolism with significantly elevated serum ALT levels.

CONCLUSIONS

HMGB1 and RAGE participate in the inflammation of the periodontal tissues in diabetic rats. Diabetes leads to elevated expression of HMGB1 in the periodontal tissues. Both periodontitis and hyperglycemia contribute to liver metabolic dysfunction. HMGB1- RAGE provides clues in the study of signaling pathways underlying the mutual susceptibility of diabetes and periodontitis.