Effects of exercise and diet change on cognition function and synaptic plasticity in high fat diet induced obese rats

Abstract

Background: Nutritional imbalance-induced obesity causes a variety of diseases and in particular is an important cause of cognitive function decline. This study was performed on Sprague Dawley (SD) rats with 13-weeks of high fat diet-induced obesity in connection to the effects of regular exercise and dietary control for 8 weeks on the synaptic plasticity and cognitive abilities of brain.

Methods: Four weeks-old SD rats were adopted classified into normal-normal diet-sedentary (NNS, n = 8), obesity-high fat diet-sedentary (OHS, n = 8), obesity-high fat diet-training (OHT, n = 8), obesity-normal diet-sedentary (ONS, n = 8) and obesity- normal diet-training (ONT, n = 8). The exercise program consisted of a treadmill exercise administered at a speed of 8 m/min for 1-4 weeks, and 14 m/min for 5-8 weeks. The Western blot method was used to measure the expression of NGF, BDNF, p38MAPK and p-p38MAPK proteins in hippocampus of the brain, and expressions of NGF, BDNF, TrkA, TrkB, CREB and synapsin1 mRNA were analyzed through qRT-PCR.

Results: The results suggest cognitive function-related protein levels and mRNA expression to be significantly decreased in the hippocampus of obese rats, and synaptic plasticity as well as cognitive function signaling sub-pathway factors were also significantly decreased. In addition, 8-weeks exercises and treatment by dietary change had induced significant increase of cognitive function-related protein levels and mRNA expression as well as synaptic plasticity and cognitive function signaling sub-pathway factors in obese rats. In particular, the combined treatment had presented even more positive effect.

Conclusions: Therefore, it was determined that the high fat diet-induced obesity decreases plasticity and cognitive function of the brain, but was identified as being improved by exercises and dietary changes. In particular, it is considered that regular exercise has positive effects on memory span and learning capacity unlike dietary control.

Figure 1

Comparison of body weight of high fat diet induced-obesity after 8-weeks treatment. Mean ± SE, *p < 0.05 vs NNS, #p < 0.05 vs OHS, ^†p < 0.05 pre and post. NNS; normal-normal diet-sedenstary, OHS; obesity-high fat diet-sedentary, OHT; obesity-high fat diet-tarining, ONS; obesity-normal diet-sedentary, ONT; obesity-normal diet-training.

Figure 2

Comparison on protein expressions of NGF (A) and BDNF (B) in hippocampus of rats with high fat diet-induced obesity. Comparison on protein expressions of NGF (C) and BDNF (D) after 8-weeks treatment (Exercise, normal diet, exercise and normal diet). Values are means ± SE. *p < 0.05 vs NNS (A, B) or OHS (C, D), #p < 0.05 vs OHT.

Figure 3

Comparison on protein expressions of p38MAPK (A) and p-p38MAPK (B) in hippocampus of rats with high fat diet-induced obesity. Comparison on protein expression of p38MAPK (C) and p-p38MAPK (D) after 8-weeks treatment (Exercise, normal diet, exercise and normal diet). Values are means ± SE. *p < 0.05 vs NNS (A, B) or OHS (C, D), #p < 0.05 vs OHT.

Figure 4

Comparison on mRNA levels of NGF (A), BDNF (B), TrkA (E) and TrkB (F) in hippocampus of rats with high fat diet-induced obesity. Comparison on mRNA levels of NGF (C), BDNF (D), TrkA (G) and TrkB (H) after 8-weeks treatment (Exercise, normal diet, exercise and normal diet). Values are means ± SE. *p < 0.05 vs NNS (A, B, E, F) or OHS (C, D, G, H), #p < 0.05 vs OHT, †p < 0.05 vs ONS.

Figure 5

Comparison on mRNA levels of MAPK1 (A), CREB (C) and Synapsin1 (D) in hippocampus of rats with high fat diet-induced obesity. Comparison on mRNA levels of MAPK1 (B), CREB (E) and Synapsin1 (F) after 8-weeks treatment (Exercise, normal diet, exercise and normal diet). Values are means ± SE. *p < 0.05 vs NNS (A, C, D) or OHS (B, E, F).

Figure 6

Effects of diet and exercise on spatial learning performance using the water maze. (A) Effects of between group and time an interaction was showed. In addition, there were significant differences in the group and time respectively. (B) In the final period the 3 days NNS, OHS and ONT compared to the OHS and ONS significantly lower. Values are means ± SE. *p < 0.05 vs NNS, #p < 0.05 vs ONS.