| Objective: The purpose of this study was to investigate the effects of different forms of exercise intervention on cognitive function of aging rats and to select the best exercise mode and explore the potential molecular mechanism by which different forms of exercise improve cognitive function in brain aging rats.Methods: In this study,SPF 6-month-old Wistar rats were fed to 21-month-old Wistar rats were randomly divided into group with 10 rats.Natural aging rats at 21 months of age were fed to 24 months of age without any intervention regarded as a model group(OC);Natural aging rats were trained with treadmill exercise as the aerobic intervention group(OT);Natural aging rats were trained with weight-bearing ladder training as resistance training group(OR).Natural aging rats were trained with treadmill exercise and/or climbed the ladder alternately as a mixed group(OM),and all exercise interventions were conducted for 12 weeks.6-month-old Wistar rats were regarded as the young control group(YC).The cognitive function of aging rats was evaluated by Morris water maze.After the water maze experiment,all rats were allowed to rest for 24 hours,after which all rats were sacrificed by breaking their necks after blood extraction from their eyeballs.Hippocampal tissue was taken out on the ice and put into the-80 ℃ refrigerator(or liquid nitrogen).Morphological changes of hippocampal neurons were evaluated by HE and Nissl staining;The structural changes of hippocampal synapses were evaluated by transmission electron microscope;BDNF in serum was detected by ELISA kit;The changes of synaptic plasticity were verified by Western blot;The senescence proteins were verified by Western blot;The changes of proteins in the Wnt pathway were detected to verify the activation of the pathway;and the apoptosis-related proteins were detected to verify the level of apoptosis;In addition,NeuN neuron staining was used to evaluate the loss of mature neurons.Results: 1)MWM showed that,compared with the YC group,aging rats obviously prolong the latency to platform(p<0.001),swimming speed decreased(p<0.01),and the number through the target platform decreased significantly(p<0.01),which suggest that the cognitive ability of aging rats impair.However,three different forms of exercise intervention(OR,OT,OM)increase the number of cross platform(p<0.05),attenuate the cognitive impairment.2)HE hippocampus and Nissl staining showed that,the cells in the hippocampal tissue of the aging rats were loosely arranged and irregularly-shaped,and the number of neosomes was significantly reduced,indicating that the neuronal function of the aged rats was seriously damaged.However,three different forms of exercise intervention protect some neuronal functions,among which the best effects were OT and OM.3)Compared with the control group,DKK-1(Wnt signaling inhibitor)and sensory-related proteins(Ac-p53 and p53)were significantly increased and Sirt1 was decreased in the hippocampal tissues of OC group.Three different forms of exercise intervention could increase the expression of Sirt1 protein(p<0.01)and reduce the expression level of senescence related proteins.The significant down-regulation of DKK-1 protein was only observed in OT group(p<0.01).4)Compared with the YC group,synaptic proteins(SYN,PSD-95,PSD-93)in hippocampal tissues in OC group were significantly decreased.The abnormal reduction of synaptic proteins was reversed by three different forms of exercise intervention(p<0.05).Moreover,transmission electron microscopy also showed that,the hippocampal synaptic structure of OC was severely damaged or even disappeared,the synaptic gap was not clear,and the postsynaptic membrane was thickened.The three forms of exercise intervention restored part of the synaptic structure,among which the best effects were OT and OM group.5)Compared with the control group,p-CREB protein in hippocampal tissue and BDNF protein in serum in OC group were significantly down-regulated,while three different forms of exercise intervention increased p-CREB level.However,only treadmill running and alternate exercise significantly increased BDNF level(p<0.05).6)The results showed that increased hippocampal neuron loss in OC group was accompanied by an increase in apoptotic proteins.We detected an increase in Bax expression and a decrease in Bcl-2 protein level in the hippocampal tissue in OC group,while OT and alternate exercise increased Bcl-2 protein level(p<0.05)and decreased Bax level(p<0.01).In addition,we observed that OT and OR group restored the down-regulation of the PI3K/Akt signaling pathway caused by aging(p<0.01).Consistent with this,NeuN neuron staining showed that,compared with YC group,the number of mature neurons in the hippocampus of OC group was markedly reduced,indicated increased hippocampal neuron loss,The three forms of exercise intervention restored part of the synaptic structure,among which the best effects were OT and OM group.7)Next,we examined the effects of three different forms of intervention on downstream factors of Wnt signaling.Western blotting showed that compared with the control group,the hippocampal levels of Axin1 protein and the phosphorylation of β-catenin(Ser33,Ser37,Thr41)in OC group were significantly increased,indicating Wnt signaling down-regulation in OC rats.Fortunately,three different forms of exercise intervention reduced the expression of these proteins.In addition,compared with YC group,the phosphorylation level of GSK-3 at ser9 site of hippocampal tissues in OC group was significantly reduced(p<0.001)and PHF10 was significantly increased,which suggest that the GSK-3 activity in OC group was increased,thus promoted the upregulation of PHF10.Compared with the natural aging model,three different forms of exercise intervention can reduce the phosphorylation of β-catenin and Axin1.Conclusion: Three different forms of exercise intervention can attenuate cognitive dysfunction in OC group.By comparing the combined effects of the three forms of exercise,the effect of the treadmill exercise intervention is the best one.Mechanically,it may restore the abnormally decreased Wnt signal pathway and corresponding targets in the naturally aging rats. |
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