Animals Experiment On The Effects Of Hyperlipidemia In Mice With Periodontitis

Objective:Recent clinical studies have shown a clear and close relationship between periodontitis and cardiovascular diseases. The decompensation of lipid metabolism is a significant reason for cardiovascular diseases. This study was designed to induce periodontitis in Apo-E-mice and then to observe pathological changes in Apo-E-mice's periodontium, thus to investigate the effects hyperlipidemia has on the progression of periodontitis and the changes of the inflammatory factors as disease progress.Method:1.Experimental animal model and selective grouping:Experimental animals were divided into two groups:Group A designated as the group with uncomplicated periodontitis with eighteen Apo-E+/+ mice. Group B designated as the group with periodontitis and hyperlipidemia with eighteen Apo-E-/-mice. After feeding both groups with high lipid diet for four weeks, hyperlipidemia was successfully established in group B. There are no evident changes in serum lipid level in group A.2.Laboratory testing:Blood samples was draw from the inferior ophthalmic venous plexus of six randomly chosen experimental mice from each group, on the first, third and fifth week. Enzyme-Linked Immunosorbent Assay (ELISA) was used to measure inflammatory factor IL-6 and CRP serum level in collected samples. The test for mice's periodontium:Mazza's method was used to determine the sulcus bleeding index and furcation involvement. After the above tests, post mortem samples of left maxillary second molar and surrounding periodontal tissue were obtained for sectional micro-CT scan, reconstruction, measurement for alveolar bone loss and bone mineral density.3.Statistical analysis:Using SPSS12.0 statistical analysis package for the " t" test. p<0.05 was considered statistically significant.Result:1. Model of hyperlipidemia:Group B's HDL-C, LDL-C, TC, TG were all higher than group A with high lipid diet for four weeks, it was statistically significant (p<0.05).2. Periodontal examination results:Gingival sulcus bleeding index:there are no evident differences between group A and B at one week after installation of ligate. Group B's indicators were significantly higher than group A's at the third and fifth week, it was statistically significant (p<0.05). Furcation involvement:The furcation involvement index was zero at the first week. There were minor signs of furcation involvement in group A and B at the third week but was statistically insignificant. Group B's furcation involvement became severe at fifth weeks as compare with group A's and it was statistically significant (p<0.05).3. IL-6 and CRP inflammatory factors level comparison:IL-6:Group B's IL-6 level was at 37.89±2.13 pg/ml, significantly higher than group A's at 30.78±3.45 pg/ml in the third weeks and it was statistically significant (p<0.05). Group B's IL-6 level was at 43.62±3.13 pg/ml, significantly higher than group A's at 35.63±3.20 pg/ml in the fifth weeks and it was statistically significant (p<0.05). CRP:Group B's CRP level was at 0.69±0.04 ng/ml, significantly higher than group A's at 0.46±0.02 ng/ml in the fifth weeks and it was statistically significant (p<0.05).4. Micro-CT measurements:Level of horizontal alveolar bone loss of group B was greater than group A at 1 week after ligate installation. The difference was greater at third and fifth weeks; especially at the fifth weeks. The alveolar bone loss was three dimensional. In many samples alveolar bone loss reached down to the level of root apex. It was statistically significant (p<0.05). All three test results were statistically significant (p<0.05). Bone mineral density comparison:there were no evident differences between group B and A at one week after installation of ligates and it was not statistically significant. The differences were evident between group B and A at third and fifth weeks and it was statistically significant (p<0.05).Conclusion:1. Successfully established hyperlipidemia in Apo-E-/-mice group after four weeks feeding with high lipid diet. There were not evident changes of the blood lipid level of Apo-E+/+ mice group. This indicated that the correct animal was chosen for the study, and it provided referenced value for the post study analysis.2. The inflammatory factors and the periodontal tissue test results of mice with periodontitis and hyperlipidemia shown severe disease progression as compares to mice with uncomplicated periodontitis. This indicates that higher serum lipid level may have important effects on the progression of periodontitis.3. Micro-CT test results:Micro-CT test result indicates the high serum lipid level results in significant alveolar bone loss; reduce alveolar bone mineral density and trabeculation. This indicates that the higher serum lipid level may aggravate periodontitis induced bone lost.