RNA-seq analyses of periodontal tissue and liver of periodontitis-affected mice

Background/purpose Periodontal diseases exacerbate hepatic inflammation and diseases like non-alcoholic fatty liver disease via circulating pathogenic factors from periodontal tissue. Long-term pre-symptomatic state eventually leads to the development of such hepatic diseases. However, it is uncertain if periodontitis contributes in the onset of hepatic pre-symptomatic state. Herein, we conducted a hepatic whole transcription analysis of periodontitis-affected mice and healthy mice to understand the early functional changes in the hepatic system in periodontitis-affected mice. Materials and methods Silk ligatures were tied around mice second maxillary molars for 14 days to develop periodontitis. RNA-seq samples were collected from periodontal tissues and liver tissues of mice with periodontitis and healthy mice. Lipidomic analysis of hepatic omega-3 fatty acids in periodontitis-affected and healthy mice was conducted. The anti-inflammatory effects of omega-3 fatty acids and their metabolites were elucidated using hepatocytes HepG2 cells. Results In the liver of mice with periodontitis, genes coding for cytochrome P450 such as Cyp4a12a and Cyp4a12b were identified as significantly down-regulated genes. Lipidomic analyses identified that epoxidation and subsequent hydrolysis of hepatic omega-3 fatty acids were inhibited in periodontitis-affected mice. Eicosapentaenoic acid metabolites, epoxy eicosatetraenoic acid and dihydroxyeicosatetraenoic acid, inhibited inflammatory responses of HepG2 cells. Conclusion These results suggest that, in the liver of periodontitis-affected mice, due to the reduced activity of omega-3 fatty acid epoxidation, pre-symptomatic state with pro-inflammatory status develop. Therefore, early intervention of periodontitis might contribute to the prevention of the onset of hepatic diseases.