Effects of aerobic exercise intensity on hippocampus BDNF, TrkB protein expression and cognitive function in high-fat diet-fed mice

Effects of aerobic exercise intensity on Brain-derived neurotrophic factor (BDNF) expression of hippocampus and cognitive function in mice with high-fat diet are not well known. In this study, we investigated the differences in hippocampus BDNF and its receptor, tyrosine kinase B (TrkB) expression and cognitive functions in high-fat diet-fed mice after aerobic exercise with different intensities. The mice were fed a 60% high-fat diet for 6 weeks and divided into 4 experimental groups; no exercise (HFD, n=6), low intensity exercise (HFD-LE, n=6), moderate intensity exercise (HFD-ME, n=6), or high intensity exercise (HFD-HE, n=6). Exercise intervention was conducted for 8 weeks. For the control group (CON, n=6), normal diet was fed for 14 weeks. Protein expression of BDNF and TrkB were measured by western blot and cognitive functions were determined by T-maze task and Morris water maze task. Our result show that HFD-HE and HFD-LE groups had significantly higher BDNF protein expression level than CON, and HFD-HE group had significantly higher than HFD-LE group. The HFD-HE group also showed significantly higher TrkB protein expression level than all other groups. In the T-maze task, novel route awareness was significantly higher in HFD-HE and HFD-LE groups than CON. For Morris water maze task, time to reach platform was significantly shorter in HFD-HE than all other groups. These results indicate that high intensity exercise is generally more effective for increases in BDNF and TrkB protein expression and improvements on cognitive functions than moderate and low intensity exercise even with high fat diet. Therefore, we hypothesize that high intensity exercise can be recommended to overweight or obese individuals with reduced cognitive function.