| In this experiment, we prepared branch bark powder of the cultivated mulberry from Morus multicaulis L as experimental materials. Mulberry branch bark powder has got by medium-size crushing, fine crushing and super fine crushing. The aim of this study was to investigate the potential preventive effect and antidiabetic effect of mulberry branch bark powder(MBBP).In order to study the preventive effect of MBBP in diabetic mice with normal feed, we have done the following experiment. The normal male ICR mice were maintained under environment for 7 days, then the mice were randomly assigned into five groups: normal group(fed with normal diet), control group(fed with HSFD), model group(fed with HSFD), 10% MBBP group(fed with HSFD containing 10% MBBP), 15% MBBP group(fed with HSFD containing 15% MBBP).After the normal male ICR mice were fed a diet containing 2.5 %, 5.0 % and 10.0 %, respectively, mulberry branch bark powder(MBBP) for 2 weeks, STZ(100 mg/kg) was injected into the caudal vein of these mice. These mice continued to be fed the same diet, and the levels of fasting blood glucose(FBG) were monitored on 3 days and 7 days. The results showed that oral administration of MBBP could effectively inhibit weight loss and maintain the blood glucose level. The diet with 10% MBBP inhibited almost the incidence of type 2 diabetic mice induced by STZ. MBBP also maintained the original antioxidant capacity and regulated the lipid metabolism in mice. An immunohistochemical assay showed that MBBP could also prevent the injury induced by STZ of the insulin-secreting islet β-cells. RT-PCR also confirmed that the mRNA expression of the genes PI3 K, PDK1, Akt and FoxO1 in the PI3K/AKT signalling pathway in the 10% MBBP-dose group hardly suffered from STZ. These results clearly illustrate that oral administration of MBBP has preventive effect to diabetic mice with normal feed. Especially, almost all the mice with 10.0 % MBBP-treatment were not diabetic.In order to study the preventive effect of MBBP in diabetic mice with high fat-high sucrose diet(HFSD) feed, based on the above results, we have done the following experiment. The normal male ICR mice were maintained under environment for 7 days, then the mice were randomly assigned into five groups: normal group(fed with normal diet), control group(fed with HSFD), model group(fed with HSFD), 10% MBBP group(fed with HSFD containing 10% MBBP), 15% MBBP group(fed with HSFD containing 15% MBBP). All the mice were prepared for 3 weeks, and then STZ(100 mg/kg) was injected into the caudal vein of mice in model group, 10% MBBP group and 15% MBBP group. The mice continued to be fed the same diet for 2 weeks. The results showed that there were insignificant differences in the FBG between the control group and control group. But the FBG in model group was evidently higher than that of the control group. The model group had a higher incidence rate of diabetes, approximately 100 %, which lower than that of the model group in the above experiment(75%). When 15 % MBBP was administered, the incidence rate of diabetes was 45.45%. These results suggested that the HSFD with MBBP could prevent the incidence of type 2 diabetic mice induced by STZ. Additionally, oral administration of MBBP with HSFD could control weight of mice, suppress the hyperglycemia, maintain the original antioxidant capacity and regulated the lipid metabolism in mice. Histopathological observation showed that MBBP could also prevent the injury induced by STZ of the insulin-secreting islet β-cells. RT-PCR and western blotting analysis also confirmed that MBBP could protect gene expression in the PI3K/AKT signalling pathway. These results clearly illustrated that oral administration of MBBP had preventive effect to diabetic mice with HSFD feed.The two experiments above had amply confirmed MBBP could prevent diabetes in mice, whether it is normal diet or HSFD. To investigate the therapeutic effects of MBBP on mice with diabetes by STZ-induced, we have done the following experiment. The normal male ICR mice were adaptive feeding for 3 days, and then 15 mice were randomly selected as control group with normal feed. The other mice were fed with HSFD for 4 weeks, then STZ(100 mg/kg) was injected into the caudal vein of mice. After 72 h, the mice with FBG ≥ 11.1 mmol·L-1 were selected as diabetic mice. Subsequently, the mice were randomly divided into four groups(n = 15) as follows: model group, 5% MBBP group(fed with normal diet containing 5% MBBP), 10% MBBP group(fed with normal diet containing 10% MBBP), 20% MBBP group(fed with normal diet containing 20% MBBP). In the next 4 weeks, weight loss, hyperglycemia(~≥ 20 mmol/L) and hyperinsulinemia occurred in the diabetic mice of model group. After the mice were fed a diet containing 5%, 10% and 20% MBBP, respectively, the weight loss, FBG and insulin resistance in mice had been inhibited. The 20% MBBP group had the significant effect of hpyerglycemic, which FBG and insulin had been reduced to 14.77 mmol/L and 16 mU/L, respectively. Additionally, oral administration of MBBP could decrease the content of 8-OHdG, AST, and ALT, increase antioxidation ability, regulated the lipid metabolism, and repair pancreatic cells, and the dose-effect relation is obvious. Western blotting analysis also confirmed that MBBP could enhance the gene expression of metabolic key enzymes in the liver and pancreases, accelerate the insulin discharge, and improve metabolism of glucose and lipids.In conclusion, oral administration of MBBP could prevent diabetes in mice, whether it is normal diet or HSFD. Almost all of the mice had diabetes by HSFD plus STZ-injection treatment, but MBBP could offset the effect of the HSFD. In a final experiment, after a month with MBBP-treated, the FBG, insulin and serum lipid in mice had been reduced, and the gene expression of key enzymes also had been regulated. These results suggested that MBBP could serve as ancillary drug and healthy food to prevent and treat diabetes, so MBBP have significant research value for the exploitation and utilization. |
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