| Diabetes is a disease of metabolic disorders which does harm to human health, diabetes complications can seriously affect quality of life of patients. Hippocampal damage of cognitive impairment caused by diabetes characterized by acquired cognitive and behavioral defects. Therefore, research of hippocampal injury in diabetes and its complications of diabetes become an important topic.Sericin is a kind of water-soluble proteins that has many biological activities,and it occupies about30%of the cocoon, but this is abandoned during silk reeling. Scholars have been exploring ways that how to effectively utilize such large number high quality proteins. At present, only a small number of domestic scholars performed preliminary studying to investigate the actions of sericin in treating diabetes,and found that sericin could decreasing blood glucose efficiently. In this study, streptozotocin (STZ) induced type2diabetes model rats was used to investigate the protective effects of sericin on hippocampal damage of type2diabetes rats, and develop new avenues for preventing and treating diabetes hippocampal damage.Part I Effects of sericin on the expression of HO-1in hippocampus of type2diabetes ratsObjective:To investigate the effects and possible mechanisms of sericin on neurons in hippocampus of type2diabetic rats by observing changes of HO-1expression in hippocampus of type2diabetes rats.Methods:1.48male SD rats were randomly divided into4groups, normal control group, diabetes model group, sericin treatment group and positive control group. The rats in normal control group were bred as normal. The rats in diabetes model group,sericin treatment group and positive control group were made diabetes model by injecting2%STZ (25mg/kg,3d) into the abdominal cavity continuously. After the diabetes model was successfully established, the rats in model group had no more treatment, the rats in sericin treatment group were lavaged with sericin (2.4g/kg/d,35d), the rats in positive control group were lavaged with metformin (55.33mg/kg/d,35d).2. Glucose oxidase method was used to detect the BG of rats in each group.3. Western Blotting were used to observe the expression of HO-1protein in hippocampus.4. RT-PCR was used to detect the expression of HO-1mRNA in hippocampus.Results:1.BGThe BG of rats in model group was (29.45±4.82)mmol/L, which increased obviously compared with rats in normal control group (P<0.01). The BG of rats in sericin treatment group and positive control group was (13.20±4.09) mmol/L and (13.18±2.30) mmol/L respectively, which was obviously lower than that of model rats (P<0.01). Moreover, there had no obvious differences between sericin treatment group and positive control group (P<0.05).2. HO-1expression in rat hippocampusCompared with normal control rats, the HO-1protein and mRNA expression in hippocampus of rats in model group increased remarkably (P<0.01). The HO-1protein and mRNA expression in hippocampus of rats in sericin treatment group and positive control group were significantly higher than those of model rats (P<0.01, P<0.05). Moreover, there had no significant differences between sericin treatment group and positive control group (P>0.05). Conclusions:Sericin can reduce the synthesis of HO-1in the hippocampus,and significantly reduced neuronal injury and played against diabetic injury in the hippocampus, and the therapeutical effects of sericin are similar with metformin.Part Ⅱ Effects of sericin on GH/IGF-1axis of hippocampus in type2diabetes ratsObjective:To study the effects and mechanisms of sericin on growth hormone (GH)/insulin-like growth factor-1(IGF-1) axis of hippocampus in type2diabetes rats model.Methods:1.48male SD rats were randomly divided into4groups, normal control group, diabetes model group, sericin treatment group and positive control group. The rats in normal control group were bred as normal. The rats in diabetes model group,sericin treatment group and positive control group were made diabetes model by injecting2%STZ (25mg/kg,3d) into the abdominal cavity continuously. After the diabetes model was successfully established, the rats in model group had no more treatment, the rats in sericin treatment group were lavaged with sericin (2.4g/kg/d,35d), the rats in positive control group were lavaged with metformin (55.33mg/kg/d,35d).3. Western Blotting were used to observe the expression of GH and growth hormone receptor (GHR) protein in hippocampus.4. RT-PCR was used to detect the expression of GH、GHR and IGF-1mRNA in hippocampus.Results:1.GH and IGF-1The GH level of rats in model group was (2.56±1.13)ng/ml, which increased significantly compared with rats in normal control group (P<0.01). the IGF-1level was (520.20±121.81)ng/ml, which decreased significantly compared with rats in normal control group (P<0.01). The GH level of rats in sericin treatment group, positive control group and sericin prevention group was (1.36±0.57)ng/ml,(1.37±0.46)ng/ml and (1.53±0.42)ng/ml respectively, which was significantly lower than that of model rats (P<0.01). the IGF-1level was (981.10±180.88)ng/ml,(1021.10±198.32)ng/ml and (984.60±264.31) ng/ml respectively, which was significantly higher than that of model rats (P<0.01). Moreover, there had no significant differences between sericin treatment group, sericin prevention group and positive control group (.P>0.05).2. GH expression in rat hippocampusCompared with normal control rats, the GH protein and mRNA expression in hippocampus of rats in model group increased remarkably (P<0.01). The GH protein and mRNA expression in hippocampus of rats in sericin treatment group and positive control group group were remarkably lower than those of model rats (P<0.01, P<0.05). Moreover, there had no remarkable differences between sericin treatment group and positive control group (P>0.05).3. GHR expression in rat hippocampusCompared with normal control rats, the GHR protein and mRNA expression in hippocampus of rats in model group decreased significantly (P<0.01). The GHR protein and mRNA expression in hippocampus of rats in sericin treatment group and positive control group were significantly higher than those of model rats (P<0.01, P<0.05). Moreover, there had no significant differences between sericin treatment group and positive control group (P>0.05).4. IGF-1expression in rat hippocampusCompared with normal control rats, the IGF-1mRNA expression in hippocampus of rats in model group decreased obviously (P<0.01). The IGF-1mRNA expression in hippocampus of rats in sericin treatment group and positive control group were obviously higher than those of model rats (P<0.01). Moreover, there had no obvious differences between sericin treatment group and positive control group (P>0.05). Conclusions:1. The GH/IGF-1axis of diabetes rats is disorder, manifested as, elevated GH level and decreased IGF-1level in serum, increased GH expression and reduced GHR, IGF-1expression in hippocampus.2. Sericin can protect hippocampus of diabetes rats by regulating GH/IGF-1axis disturbance. Moreover, the protective effects of sericin are similar with metformin.Part Ⅲ Effects of sericin on Akt signaling pathway of hippocampus in type2diabetes ratsObjective:To study the effects and mechanisms of sericin on protein kinase B (Akt) signaling pathway of hippocampus in type2diabetes rats model.Methods:1.48male SD rats were randomly divided into4groups, normal control group, diabetes model group, sericin treatment group and positive control group. The rats in normal control group were bred as normal. The rats in diabetes model group,sericin treatment group and positive control group were made diabetes model by injecting2%STZ (25mg/kg,3d) into the abdominal cavity continuously. After the diabetes model was successfully established, the rats in model group had no more treatment, the rats in sericin treatment group were lavaged with sericin (2.4g/kg/d,35d), the rats in positive control group were lavaged with metformin (55.33mg/kg/d,35d).2. Western Blotting were used to observe the expression of phospho protein kinase B(p-Akt)、nuclear transcription factor kappa B (NF-κB) and Bcl-XL/Bcl-2associated death promoter (Bad) protein in hippocampus.3. RT-PCR was used to detect the expression of p-Ak、NF-κB and Bad mRNA in hippocampus.Results:1. p-Akt expression in rat hippocampusCompared with normal control rats, the p-Akt protein and mRNA expression in hippocampus of rats in model group decreased significantly (P<0.01). The p-Akt protein and mRNA expression in hippocampus of rats in sericin treatment group and positive control group group were remarkably higher than those of model rats (P<0.01, P<0.05). Moreover, there had no remarkable differences between sericin treatment group and positive control group (P>0.05).2. NF-κB expression in rat hippocampusCompared with normal control rats, the NF-κB protein and mRNA expression in hippocampus of rats in model group decreased significantly (P<0.01). The NF-κB protein and mRNA expression in hippocampus of rats in sericin treatment group and positive control group were significantly higher than those of model rats (P<0.01). Moreover, there had no significant differences between sericin treatment group and positive control group (P>0.05).3. Bad expression in rat hippocampusCompared with normal control rats, the Bad protein and mRNA expression in hippocampus of rats in model group increased remarkably (P<0.01). The Bad protein and mRNA expression in hippocampus of rats in sericin treatment group and positive control group were obviously lower than those of model rats (P<0.01). Moreover, there had no obvious differences between sericin treatment group and positive control group (P>0.05).Conclusions:Sericin can act on the Akt signaling pathway, up-regulate the expression of p-Akt in type2diabetic rat hippocampus, and then up-regulate the expression of NF-κB and down-regulate the expression of Bad. |
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