| Objective:Alzheimer’s disease(AD)is a neurodegenerative disease characterized by cognitive and memory impairment.Insulin resistance caused by abnormal glucose metabolism could directly lead to neuron dysfunction and synaptic loss.On the other hand,abnormal glucose metabolism would aggravate the damage of ADDLs to nervous function.Excessive activation of NMDA receptors could also cause neuron death and synaptic damage.The abnormal structure and function of synapses and the damage of synaptic homeostasis are closely related to the impairment of clinical cognitive function.Therefore,in this study,a synaptic injury model caused by abnormal glucose metabolism was established,and insulin sensitizer metformin and NMDA antagonist memantine were selected to intervene,so as to explore the protective effect of the combination of the two drugs on synapses.And the regulation of Yueju pill on the fear memory of mice with glucose metabolismMethods:(1)Male ICR mice and db/db mice were used.ICR mice were injected with STZ via caudal vein and lateral ventricle to establish a mouse model of synaptic injury caused by abnormal glucose metabolism.Both the chemical model and db/db mice were given metformin and memantine.The blood glucose and body weight of mice were tested weekly to explore the effects of metformin and memantine combined on blood glucose and body weight,serum insulin content and insulin resistance index in the mouse model of synaptic injury caused by abnormal glucose metabolism.Morris water maze was conducted to detect the protective effect of metformin and memantine combined with glucose metabolism abnormalities on the spatial learning and memory function of the mouse model of synaptic injury.To explore the effect of combination of metformin and memantine on the Fear memory injury induced by abnormal glucose metabolism through Fear conditioning experiment.Western Blot was used to detect the expression levels of AMPK and p-ampk in the cerebral cortex of mice with synaptic injury caused by abnormal glucose metabolism,as well as the expression levels of synaptic proteins PSD95,NR2A,NR2B and Shank3.Serum T-CHO,TG,HDL-C,and LDL-C in db/db mice were tested to observe the effects of metformin and metformin on lipid metabolism.Finally,the serum AST/GOT,AKP,ALT/GPT,BUN and CRE of db/db mice were tested to determine whether metformin and metformin could damage the liver and kidney function of db/db mice.(2)Male ICR mice was used to establish a mouse model of synaptic injury caused by abnormal glucose metabolism by injecting STZ into caudal vein and lateral ventricle,and yueju pill was given to test its effects on blood glucose,body weight,spatial learning and memory function,and fear memory in mice.The effect of yueju pill on the expression levels of PSD95 and Shank3 was also detected by Western Blot.Results:(1)ICR male mice received tail vein injection of 200mg/KGSTZ for 1 week,and their blood glucose increased and body weight began to drop.In Morris water maze,the escape latency was significantly prolonged and the spatial learning and memory function of mice was impaired.The expression level of P-AMPKa protein in the cortex of mice decreased.The expression levels of synaptic proteins PSD95 and Shank3 decreased.A mouse model of synaptic injury induced by abnormal glucose metabolism was successfully established.(2)Mice were injected with 200mg/kgSTZ via tail vein and given metformin and memantine:The combined use of metformin and memantine showed hypoglycemic effect after 1 week of administration,which was earlier than the use of metformin alone.B:the combination of the two drugs could increase the decrease of serum insulin content caused by the tail vein injection of 200mg/kgSTZ and improve insulin resistance.C:The combination of metformin and memantine could inhibit the spatial memory impairment induced by tail vein injection of STZ in mice.D:The combination of metformin and memantine could prevent the enhancement of fear memory of STZ mice injected by tail vein.E:Combination of metformin and memantine can activate AMPK and increase the phosphorylation level of AMPKa protein in the cerebral cortex of mice.Combination of metformin and memantine can significantly increase the decreased expression levels of synaptic proteins PSD95,NR2B,Shank3 caused by tail vein injection of 200mg/kgSTZ,and protect the synaptic homeostasis.(3)A:The injection of 5mg/kgSTZ into the lateral ventricle had no effect on the body weight and blood glucose of mice,but the combined use of metformin and memantine could reduce the normal blood glucose level.B:the injection of STZ into the lateral ventricle had no effect on the serum insulin level of mice,but increased the insulin resistance index of mice,while the combination of metformin and vajra could reduce the insulin resistance index.C:the injection of 5mg/kgSTZ into the lateral ventricle can significantly prolong the escape latency and damage the spatial learning and memory function of mice.Compared with the model group,the combination of metformin and memantine could shorten the escape latency and inhibit the spatial learning and memory function damage caused by the injection of STZ into the lateral ventricle.D:the injection of 5mg/kgSTZ into the lateral ventricle reduced the percentage of rigidity time in mice,and also had a certain effect on fear memory,but metformin and memantine did not improve it.E:the injection of 5mg/kgSTZ into the lateral ventricle reduced the P-AMPKa protein level in the cerebral cortex of mice,while the combination of metformin and memantine significantly increased compared with the model group.F:5mg/kgSTZ injection into the lateral ventricle reduced the expression levels of synaptic proteins PSD95,NR2A,NR2B and Shank3 in the cerebral cortex of mice,while metformin and memantine combined significantly increased them compared with the model group.(4)A:The blood glucose of db/db mice was significantly increased,and significant obesity also appeared,while the combination of metformin and memantine could significantly reduce blood glucose,but had no effect on body weight.B:the combination of metformin and memantine could reduce serum TG andLDL-C levels in db/db mice and improve abnormal lipid metabolism in db/db mice.C:The spatial learning and memory function of db/db mice was impaired,while the combination of metformin and memantine had a protective effect.D:The combination of metformin and memantine did not improve the fear memory of db/db mice.E:the P-AMPKa protein level in the cerebral cortex of db/db mice was decreased,while the combination of metformin and memantine could increase it.F:there was no significant change in cerebral cortex NR2A of db/db mice,while the expression levels of PSD95,NR2B and Shank3 decreased significantly.Compared with the model group,the combined use of metformin and memantine could increase the expression levels of PSD95,NR2B and Shank3.G:The combination of metformin andmemantine could reduce the serum AST/GOT content in db/db mice,but has no effect on AKP,ALT/GPT,BUN and CRE.(5)A:Yueju pill given after tail vein injection of STZ did not significantly change the increase of blood glucose and the decrease of body weight in mice.B:Yueju pill has no protective effect on memory damage in mice.C:Yueju pill given after tail vein injection of STZ can reduce the increase of ICR mice’s stiff time percentage and improve the enhancement of fear memory.D:yueju pill can increase the decreased expression levels of synaptic protein PSD95 and Shank3 protein caused by tail vein injection of 200mg/kgSTZ.(6)A:The injection of STZ into the lateral ventricle and the administration of Yueju pill had no effect on the blood glucose and body weight of mice.B:Yueju pill has a protective effect on spatial learning and memory damage caused by STZ injection in the lateral ventricle.C:Yueju pill significantly increased the percentage of mouse ankylosing time caused by STZ injection into lateral ventricle,but it was not higher than the percentage of normal mice ankylosing time.D:the administration of Yueju pill could increase the decreased expression levels of synaptic protein PSD95 and Shank3 protein caused by 5mg/kgSTZ injection in the lateral ventricle.Conclusion:(1)Tail vein injection of 200mg/kg and lateral ventricle injection of 5mg/kgSTZ could lead to insulin resistance,memory damage,decreased levels of synaptic proteins PSD95,Shank3 and NR2B in ICR mice,and destruction of synaptic homeostasis.(2)Memantine could enhanced the hypoglycemic effect of metformin.The combination of metformin and memantine could reduce blood glucose at an earlier stage,which can not only reduce hyperglycemia,but also reduce the normal blood glucose level of mice,and improve the status of insulin resistance.(3)The combination of metformin and memantine has a protective effect on the spatial learning and memory impairment caused by abnormal glucose metabolism.(4)The combination of metformin and memantine can activate AMPK and increase the phosphorylation of AMPKa in the cerebral cortex of mice with synaptic injury caused by abnormal glucose metabolism.(5)Combination of metformin andmemantine could protect synaptic damage caused by abnormal glucose metabolism.(6)Yueju pill can not only protect the synaptic damage caused by abnormal glucose metabolism,but also regulate the fear memory of mice in both ways,while metformin and metformin cannot regulate the fear memory of mice in both ways. |
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