The Effect of Diet, Exercise and 7,12-Dimethylbenz(a)anthracene on Food Intake, Body Composition and Carcass Energy Levels in Virgin Female BALB/c Mice

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Abstract
This study investigated the effect of diet, exercise and 7,12-dimethylbenz(a)anthracene (DMBA), a mammary-tumor carcinogen, on food intake, energy consumption, body weight and body composition in virgin female BALB/c mice. Interactions were examined among three diet conditions (standard AIN-76A, restricted AIN-76A and high fat AIN-76A diet), two exercise conditions (with and without treadmill exercise) and two treatment conditions (carcinogen or corn oil sham). Mice were randomized to one of 12 groups at 6 wk of age; beginning at 8 wk of age, all mice received either 7,12-dimethylbenz(a)anthracene (1 mg/0.2 mL corn oil) or 0.2 mL of corn oil via gastric tube once each week for six consecutive weeks. Exercise in a rotating-drum treadmill was initiated at 10 wk of age and was increased to a final rate of 6 m/min for 60 min, 5 d/wk. Mice were killed at 24 wk of age, confirmed to be tumor-free and analyzed for protein and fat content, from which body energy was calculated. Energy consumption was highest in the standard diet-fed groups followed by the high fat diet-fed groups and the restricted diet-fed groups. The groups fed the standard diet and restricted diet had similar body weight and carcass energy. Exercise or DMBA treatment generally reduced food consumption, energy intake, body weight and carcass energy. In summary, diet, exercise and DMBA all had pronounced effects on energy consumption, which in turn affected body composition. These treatments may influence expression of breast cancer via their effects on body composition.