Animal models to study host-bacteria interactions involved in periodontitis

Animal models have distinct advantages because they can mimic cellular complexities that occur in humans in vivo and are often more accurate than in vitro studies that take place on plastic surfaces with limited numbers of cell types present. Furthermore, cause and effect relationships can be established by applying inhibitors or activators or through the use of genetically modified animals. Such gain or loss of function studies are often difficult to achieve in human clinical studies, particularly in obtaining target tissue due to important ethical considerations. Animal models in periodontal disease are particularly important at this point in the development of the scientific basis for understanding the predominant pathological processes. Periodontal disease can be broken down into discrete steps, each of which may be studied separately depending upon the animal model. These steps involve the development of a pathogenic biofilm, invasion of connective tissue by bacteria or their products, induction of a destructive host response in connective tissue and limitation of are pair process that follows tissue breakdown. Animal studies can test hypotheses related to each of these steps, and should be evaluated by their capacity to test a specific hypothesis rather than recapitulating all aspects of periodontal disease. Thus, each of the models described below can be adapted to test discrete components of the pathological process of periodontal disease, but not necessarily all of them.

Association between metabolic syndrome and periodontal disease

BACKGROUND

Metabolic syndrome has been suggested as a potential risk factor for periodontal disease. Data based on NHANES III, with 7431 subjects aged 20 years or older, were analysed to confirm the association between metabolic syndrome and periodontal disease, and identify which components of metabolic syndrome might play a role in this association.

METHODS

Clinical criteria for metabolic syndrome included: (1) abdominal obesity; (2) increased triglycerides; (3) decreased HDL cholesterol; (4) hypertension or current use of hypertension medication; and (5) high fasting plasma glucose. Periodontal disease was evaluated by probing pocket depth (PPD) and was defined as mean PPD≥2.5 mm.

RESULTS

Women with two or more metabolic components had significantly increased odds of having periodontal disease as compared to those with no component [(two components, OR=5.6 (95% CI: 2.2-14.4); three or more, OR=4.7 (2.0-11.2)]. Using the definition of metabolic syndrome as having three to five metabolic components (reference group with <3 components), the adjusted odds ratios were 1.0 (0.7-1.6) for men and 2.1 (1.2-3.7) for women. Abdominal obesity was the largest contributory factor in both genders.

CONCLUSIONS

While the association between metabolic syndrome and periodontal disease was particularly significant for women, abdominal obesity appeared to be the contributing metabolic factor for both genders.

Levels of serum interleukin (IL)-6 and gingival crevicular fluid of IL-1beta and prostaglandin E(2) among non-smoking subjects with gingivitis and type 2 diabetes

BACKGROUND

The goal of this study was to assess whether non-smoking patients with type 2 diabetes present with increased levels of local and systemic proinflammatory mediators and, if so, whether such an increase is associated with enhanced clinical gingival inflammation compared to non-smoking patients without diabetes.

METHODS

We used a cross-sectional database consisting of 725 self-reported lifelong non-smokers aged 53 to 74 years. Gingival crevicular fluid (GCF) levels of interleukin (IL)-1beta and prostaglandin E(2) (PGE(2)) and serum levels of IL-6 were measured using enzyme-linked immunosorbent assay. No participant had probing depth >3 mm. Participants with bleeding on probing (BOP) in <10% of sites were classified as healthy, whereas those with BOP in >or=10% of sites were defined as having biofilm-gingival interface (BGI) gingivitis.

RESULTS

Approximately 53% (n = 385) and 11% (n = 80) of the sample had BGI gingivitis and type 2 diabetes, respectively. The mean age-adjusted level of GCF IL-1beta was significantly elevated in the diabetic group compared to the non-diabetic group (P = 0.048), but serum IL-6 (P = 0.14) and GCF PGE(2) were not (P = 0.98). The mean GCF IL-1beta and PGE(2) levels were significantly elevated in subjects with BGI gingivitis (136.2 +/- 112.9 ng/ml and 277.2 +/- 187.2 ng/ml, respectively) compared to subjects with gingival health (95.9 +/- 82.9 ng/ml and 205.7 +/- 149.6 ng/ml, respectively), regardless of diabetic status (P <0.001 for both). However, serum IL-6 was elevated in subjects with BGI gingivitis compared to subjects with gingival health only among subjects with diabetes (2.9 +/- 3.2 pg/ml versus 1.5 +/- 1.4 pg/ml; P = 0.008). With the exception of serum IL-6 in subjects without diabetes, an increase in the levels of proinflammatory mediators was associated with increased odds of having BGI gingivitis. The associations were stronger in the diabetic group.

CONCLUSIONS

Type 2 diabetes may increase the host inflammatory response to oral biofilm, which, in turn, may exacerbate preconditions associated with gingivitis in susceptible individuals. Furthermore, systemic inflammation, as demonstrated by the increased level of serum IL-6, is associated with BGI gingivitis among non-smoking patients with diabetes.

Periodontal disease and risk of myocardial infarction: the role of gender and smoking

BACKGROUND

Studies examining the association between periodontal disease and coronary heart disease have shown a consistent but weak to moderate relationship. Limited data have been reported in women and the role of smoking has not been fully clarified.

METHODS/RESULTS

A population-based case-control study examining the association between periodontal disease (PD) and acute non-fatal myocardial infarction (MI) was conducted in Erie and Niagara counties in Western New York State. Cases (574) were discharged alive from local hospitals with MI diagnosis. Controls (887) were county residents randomly selected from the NY State Department of Motor Vehicles rolls and Health Care Financing Administration files. Periodontal disease was assessed using clinical attachment loss (CAL). Among men (415 cases), the odds ratio (OR) of the association between mean CAL (mm) and MI, adjusting for the effects of age, body mass index (BMI), physical activity, hypertension, cholesterol, diabetes, and total pack-years of cigarette smoking was 1.34 (1.15-1.57). In women (120 cases), the corresponding OR was 2.08 (1.47-2.94). The estimate of this association among non-smokers, also adjusting for age, gender, BMI, physical activity, hypertension, cholesterol, diabetes, and total pack-years of cigarette smoking, was 1.40 (1.06-1.86), while it was 1.49 (1.26-1.77) among smokers.

CONCLUSIONS

This study provides evidence of an association between PD and incident MI in both genders. This association appears to be independent from the possible confounding effect of smoking.

Bacterial infection increases periodontal bone loss in diabetic rats through enhanced apoptosis

Periodontal disease is the most common osteolytic disease in humans and is significantly increased by diabetes mellitus. We tested the hypothesis that bacterial infection induces bone loss in diabetic animals through a mechanism that involves enhanced apoptosis. Type II diabetic rats were inoculated with Aggregatibacter actinomycetemcomitans and treated with a caspase-3 inhibitor, ZDEVD-FMK, or vehicle alone. Apoptotic cells were measured with TUNEL; osteoblasts and bone area were measured in H&E sections. New bone formation was assessed by labeling with fluorescent dyes and by osteocalcin mRNA levels. Osteoclast number, eroded bone surface, and new bone formation were measured by tartrate-resistant acid phosphatase staining. Immunohistochemistry was performed with an antibody against tumor necrosis factor-α. Bacterial infection doubled the number of tumor necrosis factor-α-expressing cells and increased apoptotic cells adjacent to bone 10-fold (P < 0.05). Treatment with caspase inhibitor blocked apoptosis, increased the number of osteoclasts, and eroded bone surface (P < 0.05); yet, inhibition of apoptosis resulted in significantly greater net bone area because of an increase in new bone formation, osteoblast numbers, and an increase in bone coupling. Thus, bacterial infection in diabetic rats stimulates periodontitis, in part through enhanced apoptosis of osteoblastic cells that reduces osseous coupling through a caspase-3-dependent mechanism.

Gene expression dynamics during diabetic periodontitis

Diabetes impairs the resolution of periodontal inflammation. We explored pathways altered by inflammation in the diabetic periodontium by using ligatures to induce periodontitis in type-2 diabetic Goto-Kakizaki rats. Ligatures were removed after 7 days, and rats were then treated with TNF inhibitor (pegsunercept) or vehicle alone and euthanized 4 days later. RNA was extracted from periodontal tissue, examined by mRNA profiling, and further analyzed by functional criteria. We found that 1,754 genes were significantly up-regulated and 1,243 were down-regulated by pegsunercept (p < 0.05). Functional analysis revealed up-regulation of neuron-associated and retina-associated gene clusters as well as those related to cell activity and signaling. Others were down-regulated by TNF inhibition and included genes associated with host defense, apoptosis, cell signaling and activity, and coagulation/hemostasis/complement. For selected genes, findings with microarray and rt-PCR agreed. PPAR-α was investigated further by immunohistochemistry due to its anti-inflammatory function and was found to be up-regulated in the gingiva during the resolution of periodontal inflammation and suppressed by diabetes. The results indicate that diabetes-enhanced inflammation both up- and down-regulates genes involved in cellular activity and cell signaling, while it predominantly up-regulates genes involved in the host response, apoptosis, and coagulation/homeostasis/complement and down-regulates mRNA levels of neuron, retina, and energy/metabolism-associated genes.

Association between periodontal pathogens and risk of nonfatal myocardial infarction

BACKGROUND

The direct effect of periodontal pathogens on atherosclerotic plaque development has been suggested as a potential mechanism for the observed association between periodontal disease and coronary heart disease, but few studies have tested this theory.

OBJECTIVES

(i) To assess the association of periodontal pathogens in periodontal pockets with the risk of myocardial infarction (MI) and (ii) to assess whether an increase in the number of periodontal bacterial species increases the risk of MI.

METHODS

A total of 313 cases and 747 controls, consisting of Caucasian men and women from Western New York, aged 35 to 69 years, were recruited for this study. The presence of microorganisms was assessed by indirect immunofluorescence microscopy, using species-specific polyclonal and monoclonal serodiagnostic reagents. The presence of six periodontal pathogens, Porphyromonas gingivalis (Pg), Tannerella forsythensis (Tf), Prevotella intermedia (Pi), Campylobacter recta (Cr), Fusobacterium nucleatum (Fn), and Eubacterium saburreum (Es), and their co-occurrence (0-6) was compared with the odds of having myocardial infarction.

RESULTS

Univariate analyses revealed a higher percentage of the presence of each bacterium in cases compared to controls. In multivariate analyses, only Tf and Pi were statistically associated with an increase in the odds of having MI [Odds ratio OR=1.62; 95% CI (1.18-2.22); and 1.40; 95% (1.02-1.92), respectively] after adjusting for age, gender, education, cholesterol, high blood pressure, diabetes, and total pack-years of cigarette smoking. An increase in the number of different periodontal bacteria in pockets was also found to increase the odds of MI [adjusted OR=1.14; 95% CI (1.03-1.26)]. Participants who had three species or more of periodontal pathogens had about 2-fold increase in odds of having nonfatal MI than those who did not have any type of bacterial species [OR=2.01 (1.31-3.08)].

CONCLUSION

The presence of periodontal pathogens, specifically Tf or Pi, and an increase in total burden of periodontal pathogenic species were both associated with increased odds of having MI. However, further studies are needed to better assess any causal relationship, as well as the biological mechanisms underlying this association.

Potential association between prediabetic conditions and gingival and/or periodontal inflammation

AIMS/INTRODUCTION

Prediabetic conditions, which include impaired fasting glucose (IFG) and impaired glucose tolerance (IGT), might be associated with chronic gingival and/or periodontal inflammation. However, the occurrence of this oral inflammation in prediabetic conditions is poorly understood. The present study aimed to assess the association between prediabetes and gingival and/or periodontal inflammation.

MATERIALS AND METHODS

A total of 94 Puerto Rican men and women aged 40-65 years, who were residents of San Juan, Puerto Rico, and free of diabetes, were included in the study. All participants had at least one tooth site with clinical attachment loss ≥3 mm. Fasting and 2-h plasma glucose were collected. Gingival/periodontal inflammation was assessed by bleeding on gentle probing of the sulcus at six sites per tooth.

RESULTS

Participants with the percentage of teeth with bleeding on probing (BOP) equal to or greater than the median were compared with those with the percentage of teeth with BOP less than median. Participants with high BOP tended to present higher IFG (odds ratio [OR] 5.5, 95% confidence interval [CI] 1.2-25.3) and/or prediabetic condition (OR 3.6, 95% CI 1.0-13.2) than those with a low percentage of BOP, adjusting for age, sex, smoking, alcohol consumption, waist circumference and number of missing teeth. Using the continuous form of the outcome, the corresponding adjusted least squares means of percentage of BOP were 26.8 (standard error of the mean [SEM] 2.3) and 43.8 (SEM 6.0) in normal and IFG, respectively (P = 0.01), and 27.0 (SEM 2.4) and 39.0 (SEM 5.3) among healthy and prediabetic individuals, respectively (P = 0.05).

CONCLUSION

IFG and/or prediabetes are strongly associated with BOP, a marker of chronic gingival/periodontal inflammation.

A.actinomycetemcomitans-induced periodontal disease promotes systemic and local responses in rat periodontium

AIM

To characterize the histologic and cellular response to A. actinomycetemcomitans (Aa) infection.

MATERIAL & METHODS

Wistar rats infected with Aa were evaluated for antibody response, oral Aa colonization, loss of attachment, PMN recruitment, TNF-α in the junctional epithelium and connective tissue, osteoclasts and adaptive immune response in local lymph nodes at baseline and 4, 5 or 6 weeks after infection. Some groups were given antibacterial treatment at 4 weeks.

RESULTS

An antibody response against Aa occurred within 4 weeks of infection, and 78% of inoculated rats had detectable Aa in the oral cavity (p < 0.05). Aa infection significantly increased loss of attachment that was reversed by antibacterial treatment (p < 0.05). TNF-α expression in the junctional epithelium followed the same pattern. Aa stimulated high osteoclast formation and TNF-α expression in the connective tissue (p < 0.05). PMN recruitment significantly increased after Aa infection (p < 0.05). Aa also increased the number of CD8(+) T cells (p < 0.05), but not CD4(+) T cells or regulatory T cells (Tregs) (p > 0.05).

CONCLUSION

Aa infection stimulated a local response that increased numbers of PMNs and TNF-α expression in the junctional epithelium and loss of attachment. Both TNF-α expression in JE and loss of attachment was reversed by antibiotic treatment. Aa infection also increased TNF-α in the connective tissue, osteoclast numbers and CD8(+) T cells in lymph nodes. The results link Aa infection with important characteristics of periodontal destruction.

Utility of point-of-care vs reference laboratory testing for the evaluation of glucose levels

AIMS

To assess the level of agreement between point-of-care and laboratory reference glucose values in defining glycaemic status.

METHODS

We analysed 1292 overweight/obese, non-institutionalized participants, aged 40-65 years, in the San Juan Overweight Adults Longitudinal Study. Fasting venous blood glucose was determined using a point-of-care Bayer Contour Blood Glucose Meter and by Vitros System 250 instrument (laboratory). American Diabetes Association thresholds were used to classify participants into normoglycaemia (< 5.6 mmol/l), prediabetes (5.6 to 6.9 mmol/l), or diabetes groups (≥ 7 mmol/l).

RESULTS

Bland-Altman plot analysis showed a slope of 0.04 (P=0.002) for the regression between the mean difference and the average of the two methods. The slopes were significantly different from zero among people with normoglycaemia (β=-0.57, P<0.001), and prediabetes (β=-0.75, P<0.001) but not among people with diabetes (β=-0.02, P=0.68). When the prediabetes and diabetes groups were merged into one group, the slope was 0.01, and the glucose values remained similar using the two methods (P=0.76).

CONCLUSION

Point-of-care blood glucose measurement may be useful to screen people with diabetes, and to assess glucose among individuals with diabetes where blood can be drawn, but laboratory tests are unavailable or untimely.

Association of over-the-counter mouthwash use with markers of nitric oxide metabolism, inflammation, and endothelial function-a cross-sectional study

Introduction

Regular use of mouthwash can disrupt nitrate reduction by oral bacteria and may affect systemic nitric oxide (NO) levels, which are important for inflammation and endothelial function. We aim to assess the association between over-the-counter (OTC) mouthwash use and nitrate/nitrite, markers of inflammation (IL-6, TNF-α, CRP) and endothelial function (sICAM-1, sVCAM-1) in serum and saliva, and to assess the relationship between nitrate/nitrite levels and these biomarkers, as well as how OTC mouthwash modulated this relationship. We hypothesize that nitrates/nitrites are associated with these biomarkers, and that their associations would vary with the frequency of mouthwash use.

Method

Our cross-sectional study used data and specimen from the baseline of the San Juan Overweight Adult Longitudinal Study (SOALS). Robust Gamma regression with log-link function, Spearman correlations and partial correlations adjusted for covariates were used for the analysis.

Results

Using OTC mouthwash twice a day or more was significantly associated with lower serum nitrite levels compared to less frequent use (β = -0.357, 95% CI: -0.650, -0.064), but not with other markers of inflammation and endothelial function. Mouthwash use differentially impacted the relationship between nitrate/nitrite and TNF-α, sICAM-1 and sVCAM-1. Specifically, in the participants who used mouthwash less than twice a day or no use, TNF-α (β = -0.35, 95% CI: -0.52, -0.18), and sICAM-1 (β = -0.21, 95% CI: -0.32, -0.09) were negatively associated with serum nitrite. In the participants who used mouthwash twice a day or more use, TNF-α was positively associated with serum nitrate (β = 3.36, 95% CI: 2.07, 4.65), salivary nitrite (β = 1.04, 95% CI: 0.39, 1.69) and salivary nitrate (β = 0.48, 95% CI: 0.25, 0.71); sICAM-1 was positively associated with serum nitrate (β = 1.58, 95% CI: 0.86, 2.29). In both subgroups of mouthwash users, sVCAM-1 was positively correlated with serum nitrate and salivary nitrate. In addition, sVCAM-1 was positively correlated with serum nitrite in participants who used mouthwash frequently (ρ_S = 0.18, p = 0.045).

Discussion

Regular use of OTC mouthwash was associated with systemic nitric oxide. This raises concerns about its potential effects on the levels of inflammatory and endothelial biomarkers associated with cardiometabolic diseases.

Cross-sectional association among dietary habits, periodontitis, and uncontrolled diabetes in Hispanics: the LLIPDS study

Objectives

Type 2 Diabetes (T2D) is recognized as a risk factor for periodontal disease (PD), with evidence supporting a bidirectional relationship. Food choices are thought to influence both conditions, but research on their impact specifically on PD remains limited. This study aimed to explore whether food choices were linked to higher prevalence of adverse periodontal parameters and poorly controlled glucose levels among Hispanic adults with T2D.

Methods

A cross-sectional study was conducted with 260 Puerto Rican adults aged 40-65 years, all diagnosed with T2D. Dietary habits were assessed by weekly frequencies of food choices deemed healthy or unhealthy over the past year. Periodontal health was evaluated by the percentage of sites with probing pocket depth (PPD) ≥4 mm and bleeding on probing (BOP) at corresponding teeth. Glucose control was measured by glycated hemoglobin (HbA1c) levels, with uncontrolled glucose defined as HbA1c ≥ 7%. Linear regression models adjusted for demographic and clinical variables estimated associations with PD. Logistic regression assessed associations with glucose control.

Results

The median Healthy Eating Score was 0.5 (Q1, Q3: -3.9, 4.5). A higher Healthy Eating Score was significantly associated with fewer sites exhibiting PPD ≥ 4 mm and BOP (adjusted β: -0.02; SE: 0.01; p = 0.035), and reduced odds of uncontrolled glucose (adjusted odds ratio: 0.94; 95% CI: 0.89-0.98; p = 0.007).

Conclusions

Adherence to a healthier dietary pattern appears to correlate with lower periodontal inflammation and greater glucose control among Hispanics with T2D. Prospective studies are needed to confirm causality and long-term effects.