Voluntary Wheel Running Decreases Daytime Intake Of Very High-fat Diet In Mice By Improving Satiation

Exercise reduces the consumption of and preference for high-fat foods. The neurobiological mechanisms which underlie these benefits are not fully understood. PURPOSE: To further characterize the benefits of exercise on high-fat food intake behavior, we tested the effects of voluntary wheel running on feeding rhythm and meal structure in mice. We also investigated whether opioid and dopamine systems had mechanistic roles in the benefits of exercise on high-fat feeding. METHODS: Male C57BL/6 N mice fed very high-fat diet (VHFD) were divided into exercise and sedentary groups. Mice in the exercise group were treated with 30 minutes of voluntary wheel running daily. Mice in the sedentary group were instead treated with a locked running wheel which could not rotate, as control. Daytime and nighttime food intake were calculated from changes in food mass measured at 12-hour intervals. Time spent eating, meal structure (duration, size, number, intermeal interval), and eating rate were quantified from video recordings of feeding behavior. Opioid and dopamine function were assessed by measuring VHFD intake for 6 hours after intraperitoneal injection of U-50,488, a kappa opioid receptor agonist which blocks dopamine neurotransmission. RESULTS: Compared to control, exercise mice ate less VHFD during the day (0.98 ± 0.01 vs. 0.73 ± 0.03 grams, p < 0.001). Nighttime food intake was not different between groups (1.51 ± 0.04 vs. 1.44 ± 0.04 g, p > 0.05). Exercise mice spent less time eating during the day (11.21 ± 0.95 vs. 8.44 ± 0.57 minutes, p < 0.05). Exercise mice also had a shorter meal duration (73.49 ± 3.42 vs. 60.18 ± 1.84 seconds, p < 0.05) and smaller meal size (129.5 ± 5.3 vs. 101.8 ± 6.8 milligrams, p < 0.001) during the day. The number of meals (9.2 ± 0.74 vs. 8.4 ± 0.38, p > 0.05), intermeal interval (81.7 ± 9.0 vs. 87.7 ± 6.4 minutes, p > 0.05), and eating rate (106.2 ± 2.2 vs. 102.3 ± 7.1 milligrams per minute, p > 0.05) during the day were not different between groups. U-50,488 increased VHFD intake more for exercise than control mice (0.25 ± 0.05 vs 44.3 ± 0.04 grams, p < 0.01). CONCLUSIONS: Voluntary wheel running decreased daytime intake of VHFD in mice by enhancing satiation. Such benefit may be mediated by opioid and dopamine pathways. CSU-AAUP Faculty Research Grant (JC)