Effects of periodontitis on aortic insulin resistance in an obese rat model.

The combination of obesity and its associated risk factors, such as insulin resistance and inflammation, results in the development of atherosclerosis. However, the effects of periodontitis on atherosclerosis in an obese body remain unclear. The aim of the study was to investigate the effects of ligature-induced periodontitis in Zucker fatty rats on initiation of atherosclerosis by evaluating aortic insulin resistance. Zucker fatty rats (n=24) were divided into two groups. In the periodontitis group, periodontitis was ligature-induced for 4 weeks, whereas the control group was left unligated. After the 4-week experimental period, descending aorta was used for measuring the levels of lipid deposits, immunohistochemical analysis, and evaluation of gene expression. Levels of serum C-reactive protein (CRP), tumor necrosis factor-alpha (TNF-alpha), and insulin were also measured. Rats in the periodontitis group had significantly enhanced lipid deposits in the aorta, but not in the control group. Expression of suppressor of cytokine signaling 3, vascular cell adhesion molecule 1, reactive oxygen species, nitrotyrosine, and endothelin-1 in the periodontitis group was more intense than that in the control group. Significantly decreased levels of phosphatidylinositol 3-kinase (Pi3k) catalytic beta-polypeptide (Pi3kcb), Pi3kp85, and insulin receptor substrate 1 and 2 were observed in the periodontitis group. Levels of serum CRP and TNF-alpha were significantly increased in the periodontitis group. Under insulin-stimulated conditions, aorta in the periodontitis group altered the Akt phosphorylation. Periodontitis in obesity induced the initial stage of atherosclerosis and disturbed aortic insulin signaling.

Relationship between periodontitis and hepatic abnormalities in young adults.

OBJECTIVE: Obesity has been implicated as a risk factor for periodontitis and non-alcoholic fatty liver disease (NAFLD). In NAFLD, elevated alanine aminotransferase (ALT) is associated with obesity. Although a possible interrelationship between liver function and periodontitis has been reported among the middle-aged population, the correlation in young adults is little known. This study was designed to investigate the relationship between ALT and the presence of periodontitis in university students in Japan. MATERIAL AND METHODS: Medical and oral health data were collected in a cross-sectional examination conducted by the Health Service Center of Okayama University. Systemically healthy, non-smoking students aged 18 and 19 years old (n = 2225) were included. The protocol of the United States National Health and Nutrition Examination Survey was applied. Subjects with probing pocket depth >or= 4 mm were defined as having periodontitis. Logistic regression analysis was used to estimate the association between ALT, body mass index and periodontitis. RESULTS: The number of subjects with periodontitis was 104 (4.7%). In males, having periodontitis was significantly associated with an increased level of ALT (>or= 41 IU/l) in logistic regression analysis (adjusted odds ratio 2.3; 95% confidence interval 1.0-5.2; p < 0.05). However, there was no significant association between periodontitis and ALT in female students. CONCLUSIONS: Elevated ALT could be a potential risk indicator for periodontitis among young males. Monitoring hepatic abnormalities to prevent periodontitis must be better understood, even in the young adult population.

Preventive effects of a cocoa-enriched diet on gingival oxidative stress in experimental periodontitis.

BACKGROUND: Oxidative stress affects the progression of periodontitis. Cocoa is a rich source of flavonoids with antioxidant properties, which could suppress gingival oxidative stress in periodontal lesions. The purpose of the present study was to investigate the effects of a cocoa-enriched diet on gingival oxidative stress in a rat-periodontitis model. METHODS: In this 4-week study, rats were divided into three groups (n = 8/group): a control group (fed a regular diet) and two periodontitis groups (fed a regular diet or cocoa-enriched diet [10% of food intake]). Periodontitis was induced by ligature placement around the mandibular first molars. Serum levels for reactive oxygen metabolites were measured at baseline and 2 and 4 weeks. At 4 weeks, the levels of 8-hydroxydeoxyguanosine and reduced/oxidized glutathione ratio were determined to evaluate gingival oxidative damage and antioxidant status, respectively. RESULTS: Rats with experimental periodontitis that were fed a regular diet showed an increase in the level of serum reactive oxygen metabolites in a time-dependent manner. These rats also had an increased 8-hydroxydeoxyguanosine level and decreased reduced/oxidized glutathione ratio in the gingival tissue, inducing alveolar bone loss and polymorphonuclear leukocyte infiltration. Although experimental periodontitis was induced in the rats fed a cocoa-enriched diet, they did not show impairments in serum reactive oxygen metabolite level and gingival levels for 8-hydroxydeoxyguanosine and reduced/oxidized glutathione ratio. Alveolar bone loss and polymorphonuclear leukocyte infiltration after ligature placement were also inhibited by cocoa intake. CONCLUSION: Consuming a cocoa-enriched diet could diminish periodontitis-induced oxidative stress, which, in turn, might suppress the progression of periodontitis.

Lipopolysaccharide-induced epithelial monoamine oxidase mediates alveolar bone loss in a rat chronic wound model.

Reactive oxygen species (ROS) production is an antimicrobial response to pathogenic challenge that may, in the case of persistent infection, have deleterious effects on the tissue of origin. A rat periodontal disease model was used to study ROS-induced chronic epithelial inflammation and bone loss. Lipopolysaccharide (LPS) was applied for 8 weeks into the gingival sulcus, and histological analysis confirmed the onset of chronic disease. Junctional epithelium was collected from healthy and diseased animals using laser-capture microdissection, and expression microarray analysis was performed. Of 19,730 genes changed in disease, 42 were up-regulated >/=4-fold. Three of the top 10 LPS-induced genes, monoamine oxidase B (MAO/B) and flavin-containing monooxygenase 1 and 2, are implicated in ROS signaling. LPS-associated induction of the ROS mediator H(2)O(2), as well as MAO/B and tumor necrosis factor (TNF)-alpha levels were validated in the rat histological sections and a porcine junctional epithelial cell culture model. Topical MAO inhibitors significantly counteracted LPS-associated elevation of H(2)O(2) production and TNF-alpha expression in vivo and in vitro, inhibited disease-associated apical migration and proliferation of junctional epithelium and inhibited induced systemic H(2)O(2) levels and alveolar bone loss in vivo. These results suggest that LPS induces chronic wounds via elevated MAO/B-mediated increases in H(2)O(2) and TNF-alpha activity by epithelial cells and is further associated with more distant effects on systemic oxidative stress and alveolar bone loss.

Effects of obesity on gingival oxidative stress in a rat model.

BACKGROUND: Studies indicate a correlation between obesity and periodontitis. Oxidative stress is involved in the progression of periodontitis. The purpose of this study was to investigate the effects of obesity on gingival oxidative stress in a rat periodontitis model. METHODS: The obese Zucker rats (n = 14) and their lean littermates (n = 14) were each divided into two groups of seven rats. In one of each group, periodontitis was induced by ligature for 4 weeks, whereas the other group was left unligated. The level of 8-hydroxydeoxyguanosine and the ratio of reduced/oxidized glutathione were determined to examine gingival oxidative stress. The serum level of reactive oxygen metabolites and the gingival gene-expression pattern related to oxidative/metabolic stress, inflammation, and cell behavior were also evaluated. RESULTS: The obese rats weighed more than the lean rats at 4 weeks. Compared to lean rats, obese rats had enhanced gingival 8-hydroxydeoxyguanosine levels and a decreased ratio of reduced/oxidized glutathione in the gingival tissue, with increasing serum reactive oxygen metabolites. However, there were no significant differences in the degree of alveolar bone loss between lean and obese rats, except for teeth with and without ligatures in both rats. In addition, the periodontal lesion in obese rats showed higher 8-hydroxydeoxyguanosine levels and polymorphonuclear leukocyte infiltration than the inflamed ones in lean rats, with downregulation of multiple cytochrome P450 gene expression. CONCLUSIONS: Obesity induced gingival oxidative stress with increasing serum reactive oxygen metabolites in rats. In the periodontal lesion, gene expressions related to a capacity for xenobiotic detoxification were downregulated in the obese model.

Effects of improvement in periodontal inflammation by toothbrushing on serum lipopolysaccharide concentration and liver injury in rats.

OBJECTIVE: Periodontitis increases the serum lipopolysaccharide level, contributing to liver injury. Toothbrushing improves periodontitis and may also affect serum lipopolysaccharide concentration and periodontitis-induced liver injury. The purpose of the present study was to examine whether the improvement in periodontal inflammation by toothbrushing clinically affects the serum lipopolysaccharide level and hepatic pathological changes in rat periodontitis. MATERIAL AND METHODS: Thirty male Wistar rats were divided into 5 groups, 2 groups receiving topical application of pyrogen-free water to the gingival sulcus for 4 or 8 weeks. The next 2 groups received topical application of lipopolysaccharide and proteases for 4 or 8 weeks. The last group received topical application of lipopolysaccharide and proteases for 8 weeks, and the palatal gingiva was brushed with a powered toothbrush once a day for 4 weeks prior to the end of the experimental period. RESULTS: Topical application of lipopolysaccharide and proteases induced not only periodontal inflammation but also an elevation in the serum lipopolysaccharide concentration, with increasing hepatic inflammation, steatosis and 8-hydroxydeoxyguanosine levels in a time-dependent manner. The rats that received gingival stimulation showed decreased polymorphonuclear leukocyte infiltration and collagen loss levels in the periodontal lesions. Furthermore, this group also showed a decrease in serum lipopolysaccharide concentration and hepatic inflammation, steatosis and 8-hydroxydeoxyguanosine levels, compared with the group receiving no treatment. CONCLUSIONS: Toothbrushing promoted healing of periodontal lesions, decreased serum lipopolysaccharide concentration and suppressed liver injury in a rat periodontitis model.

Vitamin C intake attenuates the degree of experimental atherosclerosis induced by periodontitis in the rat by decreasing oxidative stress.

OBJECTIVE: Periodontitis has been causally linked to cardiovascular disease, which is mediated through the oxidative stress induced by periodontitis. Since vitamin C has been suggested to limit oxidative damage, we hypothesized that vitamin C intake may reduce endothelial oxidative stress induced by periodontitis in the aorta. The aim of this study was to investigate the effects of vitamin C intake on the initiation of atherosclerosis in a ligature-induced rat periodontitis model. DESIGN: Eighteen 8-week-old-male Wistar rats were divided into three groups of six rats and all rats received daily fresh water and powdered food through out the 6-week study. In the vitamin C and periodontitis groups, periodontitis was ligature-induced for the first 4 weeks. In the vitamin C group, rats were given distilled water containing 1 g/L vitamin C for the 2 weeks after removing the ligature. RESULTS: In the periodontitis group, there was lipid deposition in the descending aorta and significant increases of serum level of hexanoyl-lysine (HEL), and aortic levels of nitrotyrosine expression, HEL expression and 8-hydroxydeoxyguanosine (8-OHdG) compared to the control group. Vitamin C intake significantly increased plasma vitamin C level and GSH:GSSG ratio (178% and 123%, respectively), and decreased level of serum HEL and aortic levels of nitrotyrosine, HEL and 8-OHdG (23%, 87%, 84%, and 38%, respectively). CONCLUSIONS: These results suggest that vitamin C intake attenuates the degree of experimental atherosclerosis induced by periodontitis in the rat by decreasing oxidative stress.

Effects of vitamin C intake on gingival oxidative stress in rat periodontitis.

Increased levels of oxidative stress due to excessive production of reactive oxygen species are involved in the pathogenesis of periodontitis. Studies suggest a negative association between plasma vitamin C level and the severity of periodontitis. We hypothesized that increases in plasma vitamin C levels after vitamin C intake might clinically reduce gingival oxidative stress in a rat periodontitis model. A ligature was placed around rat mandibular molars for 4 weeks to induce periodontitis, and the rats were then given drinking water with or without 1 g/L vitamin C for 2 weeks after the ligature was removed. The periodontitis-induced rats showed a 149% increase in 8-hydroxydeoxyguanosine level and a 40% decrease in reduced:oxidized glutathione ratio in gingival tissue. Vitamin C intake induced a 175% increase in plasma vitamin C level, resulting in an improvement in the gingival 8-hydroxydeoxyguanosine level (decreased) and in the reduced:oxidized glutathione ratio (increased). Furthermore, in ligature-induced periodontitis lesions, gene expression encoding inflammation, including interleukin-1 alpha and interleukin-1 beta, was more than twofold down-regulated by vitamin C intake. The results suggest that systemic administration of vitamin C could be clinically beneficial in improving periodontitis-induced oxidative stress by down-regulating inflammatory gene expression.

Vitamin C intake inhibits serum lipid peroxidation and osteoclast differentiation on alveolar bone in rats fed on a high-cholesterol diet.

OBJECTIVE: A high-cholesterol diet stimulates osteoclast differentiation, which may be induced by increased serum lipid peroxidation. The inhibition of serum lipid peroxidation by vitamin C may offer beneficial effects on osteoclast differentiation including increased expression of receptor activator of nuclear factor (NF)-kappaB ligand (RANKL) and NF-kappaB. This study investigated the effects of vitamin C intake on RANKL and NF-kappaB expression in periodontal tissue of rats fed a high-cholesterol diet. DESIGN: Twenty-four rats (8 weeks old) were divided into four groups: a control group (fed a regular diet) and three experimental groups (fed a high-cholesterol diet supplemented with 0, 1 and 2 g/l vitamin C/day) in this 12-week study. Vitamin C was provided by its addition to drinking water. As an index of serum lipid peroxidation, hexanoyl-lysine (HEL) level was determined by a competitive enzyme-linked immunosorbent assay method. Immunohistological analysis was performed to evaluate RANKL and NF-kappaB expression on the alveolar bone surface. The number of tartrate-resistant acid phosphatase (TRAP)-positive osteoclasts was also counted. RESULTS: Feeding a high-cholesterol diet increased not only the serum HEL level but also the number of TRAP-positive osteoclasts on the alveolar bone surface, with an increase in RANKL and NF-kappaB expression on alveolar bone surface. Intake of vitamin C reduced the serum HEL level and osteoclast differentiation, with decreasing RANKL and NF-kappaB expression. CONCLUSIONS: Vitamin C intake could suppress osteoclast differentiation, including RANKL and NF-kappaB expression on the alveolar bone surface, by decreasing serum lipid peroxidation in rats fed a high-cholesterol diet.

Oxidative damage of rat liver induced by ligature-induced periodontitis and chronic ethanol consumption.

OBJECTIVE: Oxidative stress plays a central role in the initiation and progression of liver disease. Chronic ethanol consumption induces oxidative damage of the liver. Using a rat model, we previously showed that chronic administration of lipopolysaccharide and proteases to gingival sulcus induced both periodontal inflammation and liver injury. Periodontitis and ethanol consumption may have an additional effect on hepatic oxidative damage. The present study investigated the effects of periodontitis on ethanol-induced oxidative damage of the liver using a rat model. DESIGN: Male Wistar rats were divided into four groups (six rats/group). During the experimental period of eight weeks, two groups were fed an ethanol-containing liquid diet, and two groups were on a pair-fed control diet. Four weeks prior to the end of the experimental period, one group from each dietary treatment was ligated to induce periodontitis, while the other group was left unligated. In order to evaluate hepatic oxidative damage, the level of hexanoyl-lysine and the ratio of reduced form glutathione/oxidized form glutathione (GSH/GSSG) was determined. The concentration of blood hexanoyl-lysine was also measured as an index of circulating lipid peroxide. RESULTS: Ligature-induced periodontitis increased plasma levels of hexanoyl-lysine. In the liver, periodontitis decreased the GSH/GSSG ratio, and the combination of periodontitis and ethanol consumption induced a significant increase in hexanoyl-lysine level compared to ethanol consumption alone. CONCLUSION: In the rat model, ligature-induced periodontitis increased plasma lipid peroxide, decreased the hepatic GSH/GSSG ratio and augmented ethanol-induced lipid peroxidation in the liver.

Mechanical stimulation of gingiva reduces plasma 8-OHdG level in rat periodontitis.

OBJECTIVE: Gingival cells respond to periodontal pathogens by generating reactive oxygen species, and such a condition would increase circulating oxidative stress. Improvement of gingival inflammation by toothbrushing may offer clinical benefits on not only periodontal health but also the circulatory conditions. We examined the effects of mechanical stimulation on the plasma 8-hydroxydeoxyguanosine level in a rat periodontitis model. DESIGN: In this experiment, male Wistar rats (n=18) were divided into three groups. The control group received topical application of pyrogen-free water to the gingival sulcus for 8 weeks, while the other two groups received topical application of bacterial pathogens (lipopolysaccharide and proteases). After 4 weeks, half of the rats in the experimental groups received daily mechanical stimulation with an electric toothbrush for 4 weeks. RESULTS: Rats treated with bacterial pathogens presented periodontal tissue damage and increased plasma levels of 8-hydroxydeoxyguanosine. Mechanical stimulation by toothbrushing decreased gingival inflammation and oxidative DNA damage indicated by a decrease in plasma 8-hydroxydeoxyguanosine. CONCLUSIONS: Mechanical stimulation of periodontally involved gingiva reduced 8-hydroxydeoxyguanosine in plasma and may contribute to a reduction in circulating oxidative stress associated molecules.

Oral administration of vitamin C prevents alveolar bone resorption induced by high dietary cholesterol in rats.

BACKGROUND: A high-cholesterol diet stimulates alveolar bone resorption, which may be induced via tissue oxidative damage. Vitamin C reduces tissue oxidative damage by neutralizing free radicals and scavenging hydroxyl radicals, and its antioxidant effect may offer the clinical benefit of preventing alveolar bone resorption in cases of hyperlipidemia. We examined whether vitamin C could suppress alveolar bone resorption in rats fed a high-cholesterol diet. METHODS: In this 12-week study, rats were divided into four groups: a control group (fed a regular diet) and three experimental groups (fed a high-cholesterol diet supplemented with 0, 1, or 2 g/l vitamin C). Vitamin C was provided by adding it to the drinking water. The bone mineral density of the alveolar bone was analyzed by microcomputerized tomography. As an index of tissue oxidative damage, the 8-hydroxydeoxyguanosine level in the periodontal tissue was determined using a competitive enzyme-linked immunosorbent assay. RESULTS: Hyperlipidemia, induced by a high-cholesterol diet, decreased rat alveolar bone density and increased the number of tartrate-resistant acid phosphatase-positive osteoclasts. The expression of 8-hydroxydeoxyguanosine was upregulated in the periodontal tissues. Intake of vitamin C reduced the effect of a high-cholesterol diet on alveolar bone density and osteoclast differentiation and decreased periodontal 8-hydroxydeoxyguanosine expression. CONCLUSION: In the rat model, vitamin C suppressed alveolar bone resorption, induced by high dietary cholesterol, by decreasing the oxidative damage of periodontal tissue.

Chronic administration of lipopolysaccharide and proteases induces periodontal inflammation and hepatic steatosis in rats.

BACKGROUND: Epidemiologic studies suggest a relationship between periodontitis and liver diseases. A rat periodontitis model was used to investigate whether a causal relationship exists between periodontitis and liver diseases. METHODS: Fourteen male Wistar rats (8 weeks old) were divided into two groups: a periodontitis group in which Escherichia coli lipopolysaccharide (LPS) and Streptomyces griseus proteases were applied into the gingival sulcus for 8 weeks, and a control group using pyrogen-free water instead. After blood samples were collected, periodontal tissues and liver specimens were analyzed. RESULTS: Chronic administration of LPS and proteases to the gingival sulcus induced periodontitis and liver injury, including steatosis with inflammation and sinusoidal fibrosis. Apoptosis, enhanced concentration of 8-hydroxydeoxyguanosine, and activated production of tumor necrosis factor-alpha in liver were observed in the periodontitis group, with increased gingival inflammation, serum LPS, and reactive oxygen species. CONCLUSION: Periodontal inflammation in a rat model induced fatty liver disease through increased serum LPS.

Oxidative damage of periodontal tissue in the rat periodontitis model: effects of a high-cholesterol diet.

Studies suggest an association between consumption of a high-cholesterol diet and periodontitis. We addressed the mechanism by which high dietary cholesterol could be detrimental to periodontal health in a rat model. Feeding a high-cholesterol diet augmented the effects of bacterial pathogens and their products (e.g., lipopolysaccharide and proteases) on production of pro-inflammatory cytokines in fibroblasts. High dietary cholesterol also increased mitochondrial 8-hydroxydeoxyguanosine in the periodontal tissues. These results suggest that excessive tissue oxidative damage induced by high dietary cholesterol could potentiate pro-inflammatory cytokine production by fibroblasts stimulated with bacterial pathogens.