High-intensity exercise improves cognitive function and hippocampal brain-derived neurotrophic factor expression in obese mice maintained on high-fat diet

We wanted to find the intensity of exercise that could increase brainderived neurotrophic factor (BDNF) expression and improve spatial learning and memory without dietary control. C57BL/6 mice were fed a 60% high-fat diet (HFD) for 6 weeks to induce obesity. Obesity-induced mice were exercised on a treadmill for 8 weeks at various exercise intensities: HFD-control (n= 7), HFD-low-intensity exercise (HFD-LIE, n= 7, 12 m/min for 75 min), HFD-middle intensity exercise (HFD-MIE, n= 7, 15 m/min for 60 min) and HFD-high-intensity exercise (HFD-HIE, n= 7, 18 m/min for 50 min). One week before sacrificing mice, the Morris water maze test was performed, and the hippocampus was immediately removed after sacrifice. The expression levels of BDNF (encoded by the gene Bdnf) and tropomyosin receptor kinase B (TrkB) in the hippocampus were analyzed by quantitative real-time reverse transcriptionpolymerase chain reaction and western blot. In the last probe test of the Morris water maze test, occupancy in the target quadrant was significantly higher in the HFD-HIE group (P< 0.05) than in the other groups. In addition, mRNA expression from the Bdnf promoter region was found to be significantly higher in the HFD-HIE group than in the other groups (P< 0.001). Although there were some differences in the levels of significance, the expression levels of both BDNF and TrkB were significantly higher in the HFD-HIE group than in the other groups. Therefore, relatively high-intensity aerobic exercise can resist the adverse effects of a high-fat diet on the brain without dietary control.