M. Parkar

Periodontitis and Systemic Inflammation: Control of the Local Infection is Associated with a Reduction in Serum Inflammatory Markers

Severe periodontitis is associated with elevated inflammatory markers in otherwise healthy populations. However, the nature of this association has not been determined. Our aim was to assess whether the degree of response to periodontal therapy was associated with changes in serological markers of systemic inflammation. Ninety-four systemically healthy subjects with severe generalized periodontitis participated in a prospective six-month blind intervention trial. Periodontal parameters and inflammatory markers [C-reactive Protein (CRP) and Interleukin-6 (IL-6)] were evaluated prior to and 2 and 6 mos after delivery of standard non-surgical periodontal therapy. Six months after treatment, significant reductions in serum IL-6 (p < 0.001, median decrease 0.2 ng/L, 95% CI 0.1–0.4 ng/L) and CRP (p < 0.0001, median decrease 0.5 mg/L, 95% CI 0.4–0.7) were observed. Decreases in inflammatory markers were significant in subjects with above average clinical response to periodontal therapy after correction for possible confounders. Periodontitis may add to the systemic inflammatory burden of affected individuals.

Short-term Effects of Intensive Periodontal Therapy on Serum Inflammatory Markers and Cholesterol

Severe periodontitis has been associated with increased systemic inflammation. In a three-arm preliminary randomized trial, we investigated the impact of standard (SPT) and intensive periodontal therapy (IPT) on serum inflammatory markers and cholesterol levels. Medical and periodontal parameters, C-reactive protein (CRP), interleukin-6 (IL-6), total cholesterol, and LDL cholesterol were evaluated in 65 systemically healthy subjects suffering from severe generalized periodontitis. Two months after treatment, both SPT and IPT resulted in significant reductions in serum CRP compared with the untreated control (0.5 ± 0.2 mg/L for SPT, P = 0.030 and 0.8 ± 0.2 mg/L for IPT, P = 0.001). Similar results were observed for IL-6. Changes in inflammation were independent of age, gender, body mass index, and ethnicity, but a significant interaction between cigarette smoking and treatment regimen was found. The IPT group also showed a decrease in total and LDL cholesterol after 2 months. Analysis of these data indicates that periodontitis causes moderate systemic inflammation in systemically healthy subjects.

Gene Polymorphisms and the Prevalence of Key Periodontal Pathogens

Growing evidence suggests that individual genetic susceptibility may influence the host’s response to infections. The aim of this project was to study whether gene polymorphisms of inflammatory markers are associated with the presence of viable periodontopathogenic bacteria. We extracted genomic DNA from 45 young adults diagnosed with generalized aggressive periodontitis to study Fc receptors, formyl peptide receptor, Interleukin-6, tumor necrosis factor-α, and vitamin D receptor polymorphisms. The presence and viable numbers of Actinobacillus actinomycetemcomitans, Porphyromonas gingivalis, and Tannerella forsythensis were determined by culture, and their identities confirmed by PCR. Multiple logistic regressions revealed that both Fcγ receptor and IL-6 -174 polymorphisms were associated with increased odds of detecting A. actinomycetemcomitans, P. gingivalis, and T. forsythensis after adjustment for age, ethnicity, smoking, and periodontitis extent. These findings support the hypothesis that complex interactions between the microbiota and host genome may be at the basis of susceptibility to aggressive periodontitis.

Association between periodontitis and common variants in the promoter of the interleukin-6 gene

We recently reported an association between interleukin-6 (IL6) polymorphisms (SNPs) and haplotypes and aggressive periodontitis (AgP). The aim of this study was to investigate this association in a larger cohort of subjects, affected by either aggressive or chronic periodontitis. Five IL6 SNPs were analyzed in 765 subjects (167 generalized aggressive periodontitis, 57 localized aggressive, 310 chronic periodontitis and 231 periodontally healthy). Among Caucasians (n=454) there were moderate associations for -1363T allele (p=0.011) and for -174GG and -1363GG genotypes with diagnosis of periodontitis (respectively, p=0.044, OR=1.6, 95% CI=1.0-2.4, and p=0.017, OR=1.8, 95% CI=1.1-2.8, adjusted for age, gender and smoking). Haplotypes containing the -174G>C, -1363G>T and -1480C>G polymorphisms were associated with diagnosis of periodontitis (p=0.02). Subgroup analysis by disease phenotype showed associations for the localized AgP (LAgP) group and -1480C>G and -6106A>T SNPs (p=0.007 and 0.010, respectively). Among Caucasians the genotypes IL6 -1480 CC and -6106 TT increased the adjusted OR for LAgP (OR=3.09 and 2.27, respectively). This study supports the hypothesis that IL6 polymorphisms and haplotypes are moderately associated with periodontitis, possibly acting through influencing tissue levels of IL6. This association is stronger for LAgP than for other periodontal disease phenotypes.

Expression Profiling of Periodontal Ligament Cells Stimulated with Enamel Matrix Proteins in vitro: A Model for Tissue Regeneration

Several studies have examined the role of enamel matrix proteins in root formation and periodontal regeneration, although most of these have focused on a few specific genes which had previously been implicated. However, recent advances in expressional profiling have made it possible to examine the range of genetic responses involved in these processes. In the present experiments, we have therefore utilized this technique to determine the effects of enamel matrix proteins on the gene activities of periodontal ligament cells in vitro. Such cells were found to have an elevated level of RNA synthesis compared with control cells. Moreover, hybridization of the cDNA prepared from this RNA to gene array filters showed that there was differential expression of 121 genes, most of which had not previously been associated with periodontal regeneration. Some of these selective changes in gene activity might thus reflect the fundamental events that underlie periodontal development.

A familial analysis of aggressive periodontitis – clinical and genetic findings

BACKGROUND AND OBJECTIVE Family history is a primary diagnostic criterion for current classification of aggressive periodontitis (AgP). However, results of previous studies have shed controversy over the degree of familiarity of AgP and its possible inheritance mechanisms. The aims of this study were to estimate the percentage of affected relatives of AgP individuals, to analyse the disease phenotypes in relatives and to explore the distributions of genetic polymorphisms of interleukin-6 (IL-6) in AgP patients and in diseased and healthy relatives. MATERIAL AND METHODS Patients with AgP were clinically examined and asked to provide relatives for examination. First-degree relatives were clinically and radiographically diagnosed. Blood samples were collected, DNA was extracted and analysis of single nucleotide polymorphisms of IL-6 (at positions -174, -1363 and -1480) by polymerase chain reaction was performed in patients and relatives. RESULTS Fifty-five AgP patients provided relatives for examination. A total of 100 first-degree relatives were assessed and 10 of them (10%) were found to have AgP. All relatives diagnosed with AgP had the same disease as the corresponding proband (localized AgP/localized AgP or generalized AgP/generalized AgP). The same IL-6 genotypes (-174 GG, -1480 CC) previously associated with AgP showed a tendency for association with AgP in relatives. CONCLUSION This pilot study confirmed a relatively high risk for relatives of AgP patients to have AgP (10%). Genetic polymorphisms in the IL-6 gene may have an impact in aetiopathogenesis. This study provides a sample size calculation for a novel study design using healthy relatives as control subjects.

Genetic Variants Associated With Neutrophil Function in Aggressive Periodontitis and Healthy Controls

BACKGROUND Genetic polymorphisms that influence neutrophil function were proposed as possible risk factors for aggressive periodontitis (AgP). The aim of this study is to test whether a clinical diagnosis and specific genetic variants are associated with neutrophil activity in subjects with AgP and healthy subjects. METHODS This study describes the results of neutrophil analyses performed in 40 subjects (20 subjects with AgP and 20 healthy control subjects). Neutrophils were extracted from peripheral blood and analyzed in a masked manner for phagocytosis and oxidative burst by flow cytometry in response to Escherichia coli, Aggregatibacter actinomycetemcomitans (previously Actinobacillus actinomycetemcomitans), and Porphyromonas gingivalis. Genomic DNA was extracted and genotyped for the nicotinamide adenine dinucleotide phosphate p22 phagocytic oxidase subunit (p22(phox)) cytochrome b alpha gene (CYBA) C242T, crystallizable gamma fragment (Fcgamma)IIa H/R, and FcgammaIIIb neutrophil antigen (NA)1/NA2 polymorphisms. RESULTS Analyses in pairs of white subjects (n = 24) revealed that patients with AgP exhibited a higher oxidative burst in response to E. coli (P = 0.002) and P. gingivalis (P = 0.002) compared to healthy control subjects. The p22(phox) CYBA 242 T allele was associated with an oxidative burst in response to the challenge by two strains of A. actinomycetemcomitans (P = 0.018 and P = 0.046). The FcgammaIIa polymorphism was associated with the phagocytic index of E. coli (P = 0.024). CONCLUSION This study confirms previous reports of a higher oxidative burst associated with AgP and presented preliminary evidence that genetic factors may influence neutrophil function in patients with AgP and healthy individuals.

Small molecule stimulation enhances bone regeneration but not titanium implant osseointegration.

The osteogenic and osseointegrative potential of a small molecule was examined to assess its usefulness in regenerative procedures. Purmorphamine was used to stimulate bone growth and repair in an in vitro cell-based assay and an in vivo chick embryo CAM-assay with and without the presence of an implant. Purmorphamine adhered to precipitated hydroxyapatite coating, could activate the sonic hedgehog pathway and thereby stimulated osteodifferentiation. Porous calcium phosphate beads were used to deliver this small molecule in vivo and showed that purmorphamine increased the trabecular bone to bone area significantly. The assay showed purmorphamine failed to induce any significant difference in osseointegration on titanium coated PTFE implants. This suggests that, while a small molecule can enhance osteogenesis and might be useful in regenerative procedures, it failed to enhance the osseointegration of a Ti coated implant, suggesting that this sort of stimulation might be useful for enhancing bone regeneration where bone loss due to disease exists, but not for enhancing early stability of an implant.

Association Between Short Leukocyte Telomere Length, Endotoxemia, and Severe Periodontitis in People With Diabetes: A Cross-Sectional Survey

OBJECTIVE Shortened leukocyte telomere length (LTL) and diagnosis of periodontitis are associated with an increased risk of complications and mortality in diabetes. This study investigated the association between LTL, endotoxemia, and severity of periodontitis in a large cohort of people with diabetes. RESEARCH DESIGN AND METHODS Six hundred thirty individuals (371 with type 2 and 259 with type 1 diabetes) were recruited from the University College Hospital in London, U.K. During a baseline visit, blood was collected for standard biochemical tests and DNA extraction, while a dental examination was performed to determine diagnosis and extent of periodontitis. LTL was measured by real-time PCR, and endotoxemia was assessed by the limulus amoebocyte lysate method. RESULTS Two hundred fifty-five individuals were diagnosed with gingivitis, 327 with periodontitis (114 with moderate and 213 with severe disease), and 48 with edentulous. Diagnosis of periodontitis was associated with shorter LTL (P = 0.04). A negative association between LTL and endotoxemia was found in the severe periodontitis and type 2 diabetes groups (P = 0.01 for both). Shorter LTL was associated with increased extent of periodontitis (P = 0.01) and increased insulin resistance (homeostatic model assessment). Multiple adjustments for biochemical, anthropometric, and medication-use variables did not affect the results. CONCLUSIONS LTL is associated with endotoxemia and diagnosis of periodontitis in people with diabetes. LTL shortening might represent a novel biological pathway accounting for previous epidemiological data that documented higher prevalence of diabetes and its complications in people with periodontitis and vice versa.