Porphyromonas gingivalis Lipopolysaccharide Upregulates Insulin Secretion From Pancreatic β Cell Line MIN6

Abstract

Background A close association between periodontitis and diabetes has been demonstrated in human cross-sectional studies, but an exact relationship between periodontitis and prediabetes has not been established. Previous studies using animal model systems consistently have shown that hyperinsulinemia occurs in animals with periodontitis compared to animals with healthy periodontium (while maintaining normoglycemia). Because bacterial lipopolysaccharide (LPS) plays an important role in the pathogenesis of periodontitis, we hypothesized that LPS may stimulate insulin secretion through a direct effect on β cell function. To test this hypothesis, pancreatic β cell line MIN6 cells were used to determine the effect of Porphyromonas gingivalis (Pg) LPS on insulin secretion. Furthermore, expression of genes altered by Pg LPS in innate immunity and insulin-signaling pathways was determined. Methods MIN6 cells were grown in medium with glucose concentration of normoglycemia (5.5 mM). Pg LPS was added to each well at final concentrations of 50, 200, and 500 ng/mL. Insulin secretion was measured using enzyme-linked immunosorbent assay. Gene expression levels altered by Pg LPS were determined by polymerase chain reaction (PCR) array for mouse innate and adaptive immunity response and mouse insulin-signaling pathways, and results were confirmed for specific genes of interest by quantitative PCR. Results Pg LPS stimulated insulin secretion in the normoglycemic condition by ≈1.5- to 3.0-fold depending on the concentration of LPS. Pg LPS treatment altered the expression of several genes involved in innate and adaptive immune response and insulin-signaling pathway. Pg LPS upregulated the expression of the immune response–related genes cluster of differentiation 8a (Cd8a), Cd14, and intercellular adhesion molecule-1 (Icam1) by about two-fold. LPS also increased the expression of two insulin signaling–related genes, glucose-6-phosphatase catalytic subunit (G6pc) and insulin-like 3 (Insl3), by three- to four-fold. Conclusions We have demonstrated for the first time that Pg LPS stimulates insulin secretion by pancreatic β cell line MIN cells. Pg LPS may have significant implications on the development of β cell compensation and insulin resistance in prediabetes in individuals with periodontitis.

Oral application of a periodontal pathogen impacts SerpinE1 expression and pancreatic islet architecture in prediabetes

“…We previously reported that SerpinE1 was expressed in the MIN6 pancreatic β cell line in vitro and expression levels were significantly higher upon incubation of cells with Pg‐LPS or live Pg . The results from the current in vivo study demonstrated that SerpinE1 was minimally expressed in the islets of the control group but was highly expressed in the experimental group, supporting the results from our in vitro study.…”

Serpine1 Mediates Porphyromonas gingivalis Induced Insulin Secretion in the Pancreatic Beta Cell Line MIN6

“…The results indicate that Pg LPS stimulates insulin secretion by MIN6 cells [11], further supporting the concept that periodontal pathogens influence IR. In addition, the results from a polymerase chain reaction array analysis identified a greater than 2-fold increase in Serpine1 gene expression by MIN6 cells upon stimulation with Pg LPS [11].…”

“…The results indicate that Pg LPS stimulates insulin secretion by MIN6 cells [11], further supporting the concept that periodontal pathogens influence IR. In addition, the results from a polymerase chain reaction array analysis identified a greater than 2-fold increase in Serpine1 gene expression by MIN6 cells upon stimulation with Pg LPS [11]. The Serpine1gene product SERPINE1, also known as Plasminogen activator inhibitor-1 (PAI1), is a serine protease inhibitor that inhibits tissue type and urokinase plasminogen activators (tPA and uPA respectively), thus functioning as an antifibrinolytic.…”

“…We previously investigated the effect of Pg LPS on insulin secretion using the pancreatic beta cell line MIN6 [11]. The results indicated that Pg LPS augments insulin secretion from MIN6 cells under a normoglycemic, but not hyperglycemic conditions and that Serpine 1 expression increases in response to Pg LPS.…”

Porphyromonas gingivalis Lipopolysaccharide Stimulation of Vascular Smooth Muscle Cells Activates Proliferation and Calcification

“…The doses of Pg ‐LPS investigated (0 to 1,000 ng/mL) were at the low end of the range used in in vitro and in vivo studies (0 to 50,000 ng/mL) 21 , 22 . Dolan et al 23 reported that healthy individuals had blood LPS levels ≥10 pg/mL.…”