Protective Effects Of Sericin On Sciatic Nerve And Correlated Neuronal Soma Of Diabetes Rats

ObjectiveThe diabetes animal model was established by intraperitoneal injection of streptozotocin (STZ). The protective effects of sericin on sciatic nerve and correlated neuronal soma of type 2 diabetes rats by observing changes of neurofilament protein (NFP) in sciatic nerve, nerve growth factor (NGF) and neuropeptide Y (NPY) protein expression in correlated neuronal soma, and provide theoretical and experimental bases for preventing diabetic peripheral neuropathy.Methods48 male SD rats were randomly divided into 4 groups and each group had 12 rats: normal control group, diabetes model group,sericin treatment group and metformin treatment group. The rats in diabetes model group, sericin treatment group and metformin treatment group were made diabetes model by injecting STZ (25mg/kg, 3d) into the abdominal cavity continuously and blood glucose (BG)≥16.7mmol/L was taken as standard. 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 metformin treatment group were lavaged with metformin (55.33mg/kg/d,35d).1.The rats were anesthetized by intraperitoneal injection of 4% chloral hydrate, the blood was obtained from vena orbitalis posterior through endocanthion and centrifugated, the BG and blood lipid in serum were respectively detected.2.The rats were sacrificed by cutting the head and the sciatic nerve, L4-6 spinal cord and spinal ganglia were taken. Immunohistochemical staining was used to observe NFP protein expression in sciatic nerve, NGF and NPY protein expression in spinal ganglia cells and anterior horn cells of spinal cord.Results1. BG: The 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 metformin treatment 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 metformin treatment group (P>0.05).2. Blood lipid: The content of triglyceride (TG), total cholesterol (TC) and low-density lipoprotein cholesterol (LDL-C) of rats in model group was (0.917±0.117) mmol/L, (1.836±0.271) mmol/L and (0.976±0.069) mmol/L, which increased significantly compared with rats in normal control group (P<0.01); the content of high-density lipoprotein cholesterol (HDL-C) of rats in model group was (0.875±0.062) mmol/L, which decreased significantly compared with normal control rats (P<0.01). The TG content of rats in sericin treatment group and metformin treatment group was (0.600±0.141) mmol/L and (0.571±0.111) mmol/L, TC was (1.528±0.009) mmol/L and (1.541±0.22) mmol/L, LDL-C was (0.854±0.11) mmol/L and (0.825±0.12) mmol/L, which was significantly lower than that of model rats (P<0.01); the content of HDL-C was (1.051±0.088) mmol/L and (1.068±0.173) mmol/L, which was significantly higher than that of model rats (P<0.01); Moreover, there had no significant differences between sericin treatment group and metformin treatment group (P>0.05).3. NFP expression in sciatic nerveNFP immunopositive products were buffy and located at neuraxis. Compared with normal control rats, the NFP expression in sciatic nerve of rats in model group decreased remarkably (P<0.01). The NFP expression in sciatic nerve of rats in sericin treatment group and metformin treatment group were remarkably higher than that of model rats (P<0.05); Moreover, there had no remarkable differences between sericin treatment group and metformin treatment group (P>0.05).4. NGF protein expression in spinal ganglia cells and anterior horn cells of spinal cordNGF protein immunopositive products were buffy exquisite granules, located at the cytoplasm and nucleus of spinal ganglia cells, and anterior horn cells of spinal cord, mainly at cytoplasm. Compared with normal control rats, the NGF expression in spinal ganglia cells and anterior horn cells of spinal cord of rats in model group decreased obviously (P<0.01). The NGF expression in spinal ganglia cells and anterior horn cells of spinal cord of rats in sericin treatment group and metformin treatment group were obviously higher than that of model rats (P<0.01,P<0.05); Moreover, there had no obvious differences between sericin treatment group and metformin treatment group (P>0.05).5. NPY protein expression in spinal ganglia cells and anterior horn cells of spinal cordNPY protein immunopositive products were tan granules and located at cytoplasm of spinal ganglia cells and anterior horn cells of spinal cord. Compared with normal control rats, the NPY expression in spinal ganglia cells and anterior horn cells of spinal cord of rats in model group increased significantly (P<0.01). The NPY expression in spinal ganglia cells and anterior horn cells of spinal cord of rats in sericin treatment group and metformin treatment group were significantly lower than that of model rats (P<0.01);Moreover, there had no significant differences between sericin treatment group and metformin treatment group (P>0.05).Conclusions1. Sericin can decrease BG and improve blood lipid disturbance of type 2 diabetes rats.2. Sericin can increase NFP expression in sciatic nerve of type 2 diabetes rats.3. Sericin can up regulate NGF protein expression and down regulate NPY protein expression in spinal ganglia cells and anterior horn cells of spinal cord of type 2 diabetes rats.4. Sericin can protect sciatic nerve and correlated neuronal soma of type 2 diabetes rats.