Impact of obesity and aging on crestal alveolar bone height in mice

Obesity and aging are associated with periodontitis, which represents a chronic inflammatory disease of the tooth-supporting tissues, i.e. the periodontium. However, if both risk factors also have a negative impact on crestal alveolar bone in a clinically healthy periodontium, has yet to be elucidated and was analyzed in this in-vivo study. Eight C57BL/6 mice were fed a normal diet during the entire study. Half of these mice were sacrificed at week 19 (group 1: younger lean mice), whereas the other half of the animals were sacrificed at week 25 (group 2: older lean mice). In addition, four mice were fed a high-fat diet until their sacrifice at week 19 (group 3: younger obese mice). Mandibles and maxillae were scanned by micro-computed tomography and, subsequently, the distance between the cementoenamel junction and alveolar bone crest (CEJ-ABC) at all molars was determined. Levels of interleukin-6, cyclooxygenase-2, visfatin and adiponectin in gingival samples were quantified by real-time PCR. For statistical analyses, the Mann-Whitney-U test was applied (p<0.05). As compared to lean mice, obese animals presented a significantly increased CEJ-ABC distance, i.e. reduced alveolar bone crest height, at week 19. The alveolar bone loss was mainly found at the first molars of the mandibles. In animals fed a normal diet, the alveolar bone crest height in the mandibles and maxillae was significantly lower in the older mice as compared to the younger animals. Furthermore, gingival cyclooxygenase-2 and visfatin expressions were higher in the obese versus lean mice and in the older versus younger mice. This in-vivo investigation shows that obesity and older age can result in reduced alveolar bone crest height and suggests that they represent risk factors even in a clinically healthy periodontium.