Diet-Induced Obesity and Its Differential Impact on Periodontal Bone Loss.

Obesity is associated with abnormal lipid metabolism and impaired bone homeostasis. The aim of our study was to investigate the impact of specific elevated fatty acid (FA) levels on alveolar bone loss in a Porphyromonas gingivalis-induced model of periodontal disease and to analyze underlying cellular mechanisms in bone-resorbing osteoclasts and bone-forming osteoblasts in mice. Four-week-old male C57BL/6 mice were randomly divided in groups and subjected to a palmitic acid (PA)- or oleic acid (OA)-enriched high-fat diet (HFD) (20% of calories from FA) or a normal caloric diet (C group) (10% of calories from FA) for 16 wk. Starting at week 10, mice were infected orally with P. gingivalis (W50) or placebo to induce alveolar bone loss. Animals were sacrificed, and percentage fat, serum inflammation (tumor necrosis factor [TNF]-α), and bone metabolism (osteocalcin [OC], carboxy-terminal collagen crosslinks [CTX], and N-terminal propeptides of type I procollagen [P1NP]) markers were measured. Osteoblasts and osteoclasts were cultured in the presence of elevated PA or OA levels and exposed to P. gingivalis. Animals on FA-enriched diets weighed significantly more compared with animals on a normal caloric diet (P < 0.05). Both obese groups had similar percentages of fat (P = nonsignificant); however, alveolar bone loss was significantly greater in animals that were on the PA-enriched HFD (P < 0.05). TNF-α levels were highest in the PA group (P < 0.001) and increased in all groups in response to P. gingivalis inoculation (P < 0.01), whereas bone remodeling markers OC, CTX, and P1NP were lowest in the PA group (P < 0.001) and highest in the C group. Bacterial challenge decreased bone metabolism markers in all groups (P < 0.01). Further, osteoclasts showed an augmented inflammatory response to P. gingivalis in the presence of hyperlipidemic PA levels as opposed to OA cultures, which responded similarly to controls. These findings indicate that the specific FA profile of diet rather than weight gain and obesity alone modulates bone metabolism and can therefore influence alveolar bone loss.

Plasma levels of tumour necrosis factor-alpha in patients with chronic periodontitis and type 2 diabetes.

OBJECTIVES: Studies suggest that elevated circulating tumour necrosis factor-alpha (TNF-alpha) may contribute to insulin resistance in patients with type 2 diabetes. The source of plasma TNF has been thought to be adipocytes associated with obesity, but inflammation and infection result in TNF-alpha production as well. METHODS: We studied 46 patients with type 2 diabetes and chronic periodontitis to determine the relationship between plasma TNF-alpha levels and clinical measures of periodontitis, gingival crevicular fluid (GCF) interleukin-1beta (IL-1beta), plasma endotoxin, serum glucose, and glycated haemoglobin (HbA1c). TNF-alpha levels were measured using a high sensitivity enzyme-linked immunosorbent assay. RESULTS: TNF-alpha showed a significant positive correlation with attachment loss (r=0.40, p=0.009), plasma endotoxin (r=0.33, p=0.03), and GCF IL-1beta (r=0.33, p=0.035), but not probing depth (r=0.28, p=0.07), bleeding on probing (r=0.30, p=0.053), plaque index (r=0.22, p=0.17), serum glucose, HbA1c (r=0.10, p=0.50), or body mass index (r=0.077, p=0.62). A dose-response relationship was observed between periodontitis severity and TNF-alpha (p=0.012). CONCLUSION: The finding that chronic periodontitis is associated with plasma TNF-alpha levels in subjects with type 2 diabetes supports the hypothesis that periodontal infection and inflammation may contribute to insulin resistance.

The influence of interleukin gene polymorphism on expression of interleukin-1beta and tumor necrosis factor-alpha in periodontal tissue and gingival crevicular fluid.

BACKGROUND: A specific composite genotype of the polymorphic interleukin-1 (IL-1) gene cluster has recently been associated with severe periodontitis. One polymorphism of the composite periodontitis-associated genotype (PAG) has been functionally linked with expression of high levels of IL-1. The purpose of this study was to test whether gingival crevicular fluid (GCF) levels of IL-1beta and tumor necrosis factor-alpha (TNFalpha), and gingival tissue levels of IL-1alpha, IL-1beta, and TNFalpha correlate with PAG, and to examine the effect of conservative periodontal therapy on these levels. METHODS: Twenty-two adults with moderate to advanced periodontal disease were enrolled. Polymerase chain reaction amplification and restriction enzymes were used to identify specific polymorphisms from peripheral blood samples. GCF samples were collected at baseline and 3 weeks following conservative treatment and analyzed by ELISA for IL-1beta and TNFalpha. An interproximal gingival biopsy was collected at baseline and follow-up and analyzed for IL-1alpha, IL-1beta, and TNFalpha by ELISA. RESULTS: The genotyping identified 7 as PAG(+) and 15 as PAG(-). The 2 groups were comparable in terms of existing periodontitis and age. In shallow sites (<4 mm), total IL-1beta in GCF was 2.5 times higher for PAG(+) patients prior to treatment (P=0.03), and 2.2 times higher after treatment (P=0.04), while differences were less apparent in deeper sites. Following treatment, a reduction in IL-1beta concentration in GCF was seen for PAG(-) but not for PAG(+) patients. While not statistically significant, a trend was observed in mean tissue levels of IL-1beta which were 3.6 times higher in PAG(+) versus PAG(-) patients (P=0.09). CONCLUSIONS: These data suggest that PAG(+) patients may demonstrate phenotypic differences as indicated by elevated levels of IL-1beta in GCF.