| With increasing prevalence of diabetes, diabetes complications ariseincreasing year by year. For the complications of diabetes, the most attentionis the vascular and nervous system lesions, and less on the study of diabetichepatic lesions, studies have found that diabetic patients with hepatic lesions isas high as50%above. Liver is a target organ of the role of insulin action andan important target organ of insulin resistance, therefore, the study ofmechanism of hepatic insulin resistance diabetes, liver disease related researchcan strengthen and improve the illness and progression of diabetes and is ofgreat significance to improve the quality of life of patients with diabetes.Sericin is a molecular weight of10-300kd, consisting of18kinds ofamino acids from the water-soluble protein polymer. Sericin content of about30%of the total silk, but the great part was removed when silk reeling andrefined, resulting in a great waste, the effective use of high-quality protein isalways hoped in silk industry.In recent years, studies found that sericin hasgood hypoglycemic effect, but the protective effect against diabetes relatedhepatic insulin resistance has not been reported at home and abroad. In thisstudy, streptozotocin (STZ) induced type2diabetes model rats was used toinvestigate the protective effects of sericin on liver injury in type2diabetesrats, and develop new avenues for preventing and treating diabetescomplications.Part Ⅰ Effects of sericin on insulin signaling pathway related factors inliver of type2diabetes ratsObjectiveTo investigate the effects and possible mechanisms of sericin on insulinsignaling pathway in liver of type2diabetic rats by observing changes of insulin receptor and insulin receptor substrate-2levels.Methods1.60male SD rats were randomly divided into5groups, normal controlgroup, diabetes model group, sericin treatment group, positive control groupand sericin prevention group,each group of12. The rats in normal controlgroup were bred as normal. The rats in diabetes model group, sericinprevention group, sericin treatment group and positive control group weremade diabetes model by injecting2%STZ (25mg/kg,3d) into the abdominalcavity continuously and blood glucose (BG)≥16.7mmol/L was taken asstandard. After the diabetes model was successfully established, the rats inmodel group had no more treatment. the rats in sericin treatment group werelavaged with sericin (2.4g/kg/d,35d), the rats in positive control group werelavaged with metformin (55.33mg/kg/d), the time same with sericin treatmentgroup,the rats in sericin prevention group were lavaged with sericin (2.4g/kg/d)for35-day before injecting STZ.2. Glucose oxidase method was used to detect the BG of rats in eachgroup.3. SP immunohistochemical staining and Western Blotting were used toobserve the expression of insulin receptor and insulin receptor substrate-2protein in liver.4. RT-PCR was used to detect the expression of insulin receptor andinsulin receptor substrate-2mRNA in liver.5. Periodic acid-schiff stain was used to detect the liver glucogen level ineach group.Results1. BGThe BG of rats in model group was (29.45±4.82)mmol/L， whichincreased obviously compared with rats in normal control group (P＜0.01).The BG of rats in sericin treatment group, positive control group and sericinprevention group was (13.20±4.09) mmol/L,(13.18±2.30) mmol/L and(10.04±2.29)mmol/L respectively, which was obviously lower than that of model rats (P＜0.01). Moreover, there had no obvious differences betweensericin treatment group, sericin prevention group and positive control group(P＞0.05).2. IR expression in rat liverIR immunopositive products were buffy granules and located inmembrane and cytoplasm. Compared with normal control rats, the IR proteinand mRNA expression in liver of rats in model group decreased remarkably(P＜0.01). The IR protein and mRNA expression in liver of rats in sericintreatment group, positive control group and sericin prevention group wereremarkably higher than those of model rats (P＜0.01). Moreover, there had noremarkable differences between sericin treatment group and positive controlgroup (P＞0.05).3. IRS-2expression in rat liverIRS-2immunopositive products were buffy granules and located inmembrane and cytoplasm. Compared with normal control rats, the IRS-2protein and mRNA expression in liver of rats in model group decreasedremarkably (P＜0.01); in sericin treatment group, positive control group andsericin prevention group were remarkably higher than those of model rats(P＜0.01). Moreover, there had no remarkable differences between sericintreatment group and positive control group (P＞0.05).4. Liver glycogen synthesis expression in rat liverLiver glucogen synthesis Periodic Acid-Schiff Stain were purplegranules and located in cytoplasm. Compared with normal control rats, theliver glycogen synthesis expression in liver of rats in model group decreasedremarkably (P＜0.01); in sericin treatment group, positive control group andsericin prevention group were remarkably higher than those of model rats(P＜0.01). Moreover, there had no remarkable differences between sericintreatment group and positive control group (P＞0.05).ConclusionsSericin can significantly decrease the type2diabetes mellitus rats of theblood glucose,through by increase the level of IR and IRS-2in liver, to improve the insulin resistance increase the liver glycogen synthesis.Part Ⅱ Effects of sericin on inflammatory factor of liver in type2diabetesratsObjectiveTo study the effects and mechanisms of sericin on tumor necrosis factor-αand hepatocyte nuclear factor4α of liver in type2diabetes rats.Methods1.60male SD rats were randomly divided into5groups, normal controlgroup, diabetes model group, sericin treatment group, positive control groupand sericin prevention group,each group of12. The rats in normal controlgroup were bred as normal. The rats in diabetes model group, sericinprevention group, sericin treatment group and positive control group weremade diabetes model by injecting2%STZ (25mg/kg,3d) into the abdominalcavity continuously and blood glucose (BG)≥16.7mmol/L was taken asstandard. After the diabetes model was successfully established, the rats inmodel group had no more treatment. the rats in sericin treatment group werelavaged with sericin (2.4g/kg/d,35d), the rats in positive control group werelavaged with metformin (55.33mg/kg/d), the time same with sericin treatmentgroup,the rats in sericin prevention group were lavaged with sericin (2.4g/kg/d)for35-day before injecting STZ.2. SP immunohistochemical staining and Western Blotting were used toobserve the expression of tumor necrosis factor-α and hepatocyte nuclearfactor4α protein in liver.3. RT-PCR was used to detect the expression of tumor necrosis factor-αand hepatocyte nuclear factor4α mRNA in liver.Results1. TNF-α expression in rat liverTNF-α immunopositive products were buffy granules and located incytoplasm. Compared with normal control rats, the TNF-α protein and mRNAexpression in liver of rats in model group higher remarkably (P＜0.01). The TNF-α protein and mRNA expression in liver of rats in sericin treatment group,positive control group and sericin prevention group were remarkablydecreased than those of model rats (P＜0.01). Moreover, there had noremarkable differences between sericin treatment group and positive controlgroup (P＞0.05).2. HNF-4α expression in rat liverHNF-4α immunopositive products were buffy granules and located innucleus. Compared with normal control rats, the HNF-4α protein and mRNAexpression in liver of rats in model group higher remarkably (P＜0.01); insericin treatment group, positive control group and sericin prevention groupwere remarkably decreased than those of model rats (P＜0.01). Moreover,there had no remarkable differences between sericin treatment group andpositive control group (P＞0.05).ConclusionsSericin can improve the insulin resistance and significantly decrease thetype2diabetes mellitus rats of the blood glucose,through by decrease the levelof TNF-a and HNF-4a in liver. |
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