荔枝核皂苷对糖调节受损大鼠胰腺组织氧化应激的改善作用及其机制

目的：研究荔枝核皂苷（SL）对糖调节受损（IGR）大鼠氧化应激及核转录因子E2相关因子2（Nrf2）/血红素加氧酶1（HO-1）信号通路的作用，阐明其相关机制。方法：采用高脂饲料喂养制备IGR大鼠模型，随机分为模型组、二甲双胍组（0.20 g·kg^-1）、低剂量SL组（0.05 g·kg^-1）、中剂量SL组（0.10 g·kg^-1）和高剂量SL组（0.20 g·kg^-1），同时设正常对照组，每组12只，连续给药6周。观察SL对实验大鼠糖脂代谢的影响，采用实时荧光定量（Real-time PCR）法检测大鼠胰腺组织中超氧化物歧化酶（SOD）、丙二醛（MDA）和HO-1 mRNA表达水平，Western blotting法检测大鼠胰腺组织胞核、胞质Nrf2和全细胞HO-1蛋白表达水平，采用SOD和MDA试剂盒检测大鼠胰腺组织中SOD活性和MDA水平。结果：与正常对照组比较，模型组大鼠空腹血糖（FBG）和血脂水平明显升高（P<0.05或P<0.01），胰腺组织中SOD活性和mRNA表达水平降低（P<0.01），MDA水平和mRNA表达水平升高（P<0.01），胞核和胞质中Nrf2蛋白表达水平和核转位率升高（P<0.01），HO-1 mRNA和蛋白表达水平升高（P<0.05或P<0.01）。与模型组比较，二甲双胍组和中、高剂量SL组大鼠FBG和血清甘油三酯（TG）水平明显降低（P<0.05或P<0.01），胰腺组织中SOD活性和mRNA表达水平升高（P<0.05或P<0.01），MDA水平和mRNA表达水平降低（P<0.05或P<0.01），胞质中Nrf2表达水平降低（P<0.05或P<0.01），胞核中Nrf2表达水平和核转位率升高（P<0.05或P<0.01），HO-1 mRNA和蛋白表达水平升高（P<0.05或P<0.01）。结论：SL具有改善糖脂代谢和增强抗氧化应激作用，其作用机制可能与激活Nrf2/HO-1信号通路、促进Nrf2核转位及增强下游抗氧化基因HO-1表达有关。

Improvement effect of saponin of litchi seed on oxidative stress ofpancreas tissue in impaired glucose regulation rats and its mechanism

Objective:To observe the effects of saponin of litchi seed (SL) on the oxidative stress and nuclear factor erythroid 2-related factor 2 (Nrf2)/heme oxygenase-1 (HO-1) pathway in the impaired glucose regulation (IGR) rats,and to clarify their mechanisms. Methods:The IGR rat models were induced by high-fat feeding,then the rats were randomly divided into model group,metformin group (0.20 g·kg^-1),low dose of SL group (0.05 g·kg^<sup>-1),medium dose of SL group (0.1 g·kg^-1),and high dose of SL group (0.20 g·kg^-1); at the same time, normal control group was established; 12 rats in each group. After 6 weeks of administration,the effects of SL on the glucose and lipid metabolism were investigated. The expression levels of superoxide dismutase (SOD),malondialdehyde (MDA),HO-1 mRNA in pancreas tissue of the rats were observed by Real-time PCR,and the expression levels of whole cell HO-1 and Nrf2 in cytoplasm and nucleaus in pancreas tissue of the rats were decected by Western blotting method. The activity of SOD and the level of MDA in pancreas tissue of the rats were detected by the kits. Results: Compared with normal control group,the fasting blood glucose(FBG) and the blood lipid levels of the rats in model group were significantly increased (P<0.05 or P<0.01),the activity and mRNA expression level of SOD in pancreas tissue were decreased (P<0.01),the level and mRNA expression level of MDA were increased (P<0.01),the expression levels of Nrf2 protein in cytoplasm and nucleurs and the nucleur translaocation rate of Nrf2 were increased (P<0.01),and the mRNA and protein expression levels of HO-1 were upregualted (P<0.05 or P<0.01). Compared with model group,the FBG and serum TG levels in metformin group,medium and high doses of SL groups were decreased (P<0.05 or P<0.01),the activities and mRNA expression levels of SOD in pancreas tissue were increased (P<0.05 or P<0.01),the levels and mRNA expression levels of MDA were decreased (P<0.05 or P<0.01),the Nrf2 protein expression levels in cytoplasm were decreased (P<0.05 or P<0.01),the Nrf2 protein expression levels in nucleaus and the Nrf2 nucleaus translocation rates were increased (P<0.05 or P<0.01),and the mRNA and protein expression levels of HO-1 were upregualted (P<0.05 or P<0.01). Conclusion:SL can improve the glycolipid metabolism and has enhancement effect on anti-oxidative stress effect,and their mechanisms might be associated with activating the Nrf2/HO-1 signaling transduction pathway,promoting the nucleurs translocation of Nrf2 and increasing the expression of antioxidant gene in the down-stream such as HO-1.