Effect of globular adiponectin on interleukin-6 and interleukin-8 expression in periodontal ligament and gingival fibroblasts

The role of adiponectin in periodontitis: Current state and future prospects

Adiponectin (APN), which is an adipokine primarily secreted by adipose tissue into the peripheral blood, exerts anti-inflammatory and metabolic regulatory functions in many systemic inflammatory diseases. Periodontitis is a localized inflammatory disease and is also the sixth-leading complication of diabetes. Uncontrolled periodontal inflammation gradually destructs the periodontal supporting apparatus and leads to the consequent loss of teeth. Recently, emerging evidence has revealed an association between APN and periodontitis. Herein, we summarize the basic information of APN and its receptor agonists. We also overview current studies considering the role of APN in periodontitis and discuss the potential mechanisms in terms of inflammation and bone metabolism. At last, we outline the correlation between APN and systemic diseases related periodontitis. Above all, APN and its agonists are promising candidates for the treatment of periodontitis, while the underlying mechanisms and clinical translational application require further exploration.

Adiponectin: Serum-saliva associations and relations with oral and systemic markers of inflammation

This study addresses gaps in our understanding about the validity and utility of using salivary adiponectin to index serum adiponectin levels. Matched blood and saliva samples were collected on a single occasion from healthy adults (n=99; age 18-36 years, 53% male). Serum and saliva was assayed for adiponectin and inflammatory cytokines (IL-1β, IL-6, IL-8, TNFα), and saliva was also assayed for markers of blood contamination (transferrin), total protein (salivary flow rate) and matrix metalloproteinase-8 (MMP-8). We examined the extent to which salivary adiponectin was associated with serum adiponectin, and the influence of potential confounders on the serum-saliva correlation, including age, sex, body mass index, and markers of inflammation, oral health, salivary blood contamination, and flow rate. Findings revealed a modest serum-saliva association for adiponectin, and strong positive associations between salivary adiponectin and salivary levels of inflammatory cytokines, MMP-8, transferrin, and total protein. By contrast, salivary adiponectin was not related to serum levels of inflammatory activity. The magnitude of the serum-saliva association was strengthened when controlling for total protein in saliva, blood leakage into oral fluid, salivary inflammatory cytokines, and MMP-8. The pattern of findings extends our understanding of salivary adiponectin and its potential use as an index of circulating adiponectin levels.

Roles of Toll-Like Receptor 4, IκB Kinase, and the Proteasome in the Intestinal Alterations Caused by Sepsis

BACKGROUND

Lipopolysaccharide decreases intestinal contractility and induces the production of cytokines, which play an important role in the pathogenesis of sepsis.

AIM

The objective of the present study was to examine the role of Toll-like receptor 4, IκB kinase, and the proteasome in the intestinal alterations induced by lipopolysaccharide.

METHODS

Sepsis was induced in rabbits by intravenous injection of lipopolysaccharide. Contractility studies of rabbit duodenum were performed in an organ bath. Expressions of interleukin-1β, interleukin-6, interleukin-8, interleukin-10, IκB kinase-α, IκB kinase-β, IκB kinase-γ, and the proteasome mRNA were determined by RT-PCR on rabbit duodenum.

RESULTS

Neomycin and polymyxin B (Toll-like receptor 4 inhibitors), IKK NBD peptide (IκB kinase complex inhibitor), and MG-132 (proteasome inhibitor) blocked partially the effects of lipopolysaccharide on the acetylcholine-, prostaglandin E2-, substance P-, and KCl-induced contractions in the longitudinal and circular smooth muscle of rabbit duodenum. Lipopolysaccharide increased the mRNA expression of interleukin-6 and interleukin-8 in duodenal tissue, and this effect was partly reversed by neomycin, polymyxin B, IKK NBD peptide, and MG-132. IκB kinase-α, IκB kinase-β, IκB kinase-γ, and the proteasome mRNA expressions was not affected by lipopolysaccharide treatment.

CONCLUSIONS

Toll-like receptor 4, the IκB kinase complex, and the proteasome could be therapeutic targets in the treatment of sepsis symptoms in the intestine.

Beneficial effects of adiponectin on periodontal ligament cells under normal and regenerative conditions

Type 2 diabetes and obesity are increasing worldwide and linked to periodontitis, a chronic disease which is characterized by the irreversible destruction of the tooth-supporting tissues, that is, periodontium. The mechanisms underlying the association of diabetes mellitus and obesity with periodontal destruction and compromised periodontal healing are not well understood, but decreased plasma levels of adiponectin, as found in diabetic and obese individuals, might be a critical mechanistic link. The aim of this in vitro study was to examine the effects of adiponectin on periodontal ligament (PDL) cells under normal and regenerative conditions, and to study the regulation of adiponectin and its receptors in these cells. Adiponectin stimulated significantly the expression of growth factors and extracellular matrix, proliferation, and in vitro wound healing, reduced significantly the constitutive tumor necrosis factor-α expression, and caused a significant upregulation of its own expression. The beneficial actions of enamel matrix derivative on a number of PDL cell functions critical for periodontal regeneration were partially enhanced by adiponectin. The periodontopathogen Porphyromonas gingivalis inhibited the adiponectin expression and stimulated the expression of its receptors. In conclusion, reduced levels of adiponectin, as found in type 2 diabetes and obesity, may compromise periodontal health and healing.

Regulation of NAMPT in human gingival fibroblasts and biopsies

Adipokines, such as nicotinamide phosphoribosyltransferase (NAMPT), are molecules, which are produced in adipose tissue. Recent studies suggest that NAMPT might also be produced in the tooth-supporting tissues, that is, periodontium, which also includes the gingiva. The aim of this study was to examine if and under what conditions NAMPT is produced in gingival fibroblasts and biopsies from healthy and inflamed gingiva. Gingival fibroblasts produced constitutively NAMPT, and this synthesis was significantly increased by interleukin-1β and the oral bacteria P. gingivalis and F. nucleatum. Inhibition of the MEK1/2 and NFκB pathways abrogated the stimulatory effects of F. nucleatum on NAMPT. Furthermore, the expression and protein levels of NAMPT were significantly enhanced in gingival biopsies from patients with periodontitis, a chronic inflammatory infectious disease of the periodontium, as compared to gingiva from periodontally healthy individuals. In summary, the present study provides original evidence that gingival fibroblasts produce NAMPT and that this synthesis is increased under inflammatory and infectious conditions. Local synthesis of NAMPT in the inflamed gingiva may contribute to the enhanced gingival and serum levels of NAMPT, as observed in periodontitis patients. Moreover, local production of NAMPT by gingival fibroblasts may represent a possible mechanism whereby periodontitis may impact on systemic diseases.