Alveolar and tibial bone status in obese mice with exercise

Abstract

Objectives: To investigate the alveolar and tibial bone status of obese mice put under exercise. Methods: Eight-week-old C57BL/6J mice raised in specific-pathogen-free environment were put to consume an 8-week high-fat diet (HFD, 45% kcal% fat) ad libitum to induce obesity. The control group (C, n=3) went on standard chow. At 16 week, the mice consuming HFD were randomly divided into 3 groups: Sedentary control (S, n=6), moderate intensity exercise (MIE; running on treadmill 16 cm/s ×1 hour/day, n=5), high intensity exercise (HIE; running on treadmill 16 cm/s ×10 min, 17 cm/s ×5 min, 18 cm/s ×5 min, 19 cm/s ×5 min, 7×/day, n=3), while the diet remain unchanged. The exercise lasted for 4 weeks. At 20 week, all mice were sacrificed, mandibles and tibiae were collected. From micro-computed tomography (micro-CT) sections, apical-coronal distance of alveolar crest to cemento-enamel junction between teeth M1 and M2 (dAC) was recorded; bone mineral density (BMD) of tibial metaphysis was measured. Results: S mice showed significantly increased body weight and body fat, while different exercise intensities (MIE/HIE) appeared to attenuate the gain in the followed parameters. Micro-CT measurements indicated that MIE/HIE mice showed significantly smaller dAC (C/S/MIE/HIE: 244.8±25.7/304.9 ±84.5/159.7±36.2/129.9±32.8 μm, P<0.01) while HIE mice had significantly higher tibial metaphysis BMD, than S mice (538.4±19.6 vs 453.8±24.4 mg HA/ccm, P<0.01). Conclusions: This preliminary study showed bony element of tooth-supporting apparatus and tibial BMD of young laboratory mice might be influenced by overnutrition or obesity, while for obese mice these parameters appeared to be modifiable by intense exercise. Nature of the bony changes in the dental alveolus and tibia, however, appeared different. Further experiments are therefore warranted to explore mechanism(s) related to the systemic effects of intense exercise upon bone physiology of animals affected by overnutrition/obesity.