目的 探讨茶多酚（tea polyphenols, TP）改善衰老2型糖尿病（type 2 diabetes mellitus, T2DM）模型大鼠胰岛 β 细胞去分化的机制。方法 40只雄性2月龄SD大鼠适应性喂养1 w,随机分为对照组（control, CON, n = 10）和造模组（n = 30）。造模组饲喂高糖高脂饲料并每日腹腔注射50 mg/kg D-半乳糖,饲喂4w后,造模组一次性腹腔注射30 mg/kg链脲佐菌素（streptozotocin, STZ）,注射STZ 2 w后,空腹血糖（fasting blood glucose, FBG）≥16.7 mmol/L即判定T2DM模型诱导成功。将诱导成功的大鼠按照FBG随机分为衰老T2DM组（model, MOD）、300 mg/kg TP组（TP）及3 mg/kg罗格列酮组（rosiglitazone, RSG）,每组各10只。各组继续50 mg/kg D-半乳糖诱导衰老并持续高糖高脂饲养8w,期间灌胃干预。实验结束后,Western blot法检测造模组胰腺组织P53蛋白的表达,明显高于CON组即判定衰老T2DM大鼠造模成功。罗氏血糖仪检测FBG,ELISA检测空腹血清胰岛素（fasting serum insulin, FINS）,并计算HOMA-IR和HOMA-β指数,HE染色观察胰腺组织病理变化,Western blot检测胰腺组织Pdx1、MafA、Ngn3、FoxO1和p-FoxO1蛋白的表达。结果 干预8周后,与CON组相比,MOD组大鼠FBG以及胰腺P53的表达水平明显升高（P<0.01）;胰腺Pdx1、MafA的表达水平及p-FoxO1/FoxO1比值明显降低（P<0.01）;Ngn3的表达水平明显升高（P<0.01）;HOMA-IR水平明显升高（P<0.01）,HOMA-β水平明显降低（P<0.01）;胰腺组织可见胰岛面积增大,不规则的胰岛形态且与周围组织界限模糊不清,部分胰岛细胞胞浆疏松或空泡化。与MOD组相比,TP组大鼠胰腺P53的表达水平明显降低（P<0.05）;FBG明显降低（P<0.01）;胰腺Pdx1、MafA的表达水平以及p-FoxO1/ FoxO1比值明显升高（P<0.01,P<0.05,P<0.05）;Ngn3的表达水平明显降低（P<0.01）。RSG组相较于MOD组,FBG明显降低（P<0.01）;胰腺Pdx1、MafA的表达水平以及p-FoxO1/ FoxO1比值明显升高（P<0.01,P<0.05,P<0.05）;Ngn3的表达水平明显降低（P<0.05）。TP组和RSG组大鼠HOMA-IR水平明显降低（P<0.05）;TP和RSG组胰岛形状改善,胰岛面积变小,胰岛细胞胞浆疏松或空泡化程度均减轻。结论 TP可能通过调节FoxO1信号通路从而改善衰老T2DM模型大鼠胰岛 β 细胞去分化,延缓T2DM的进展。

Objective To explore whether tea polyphenols (TP) improve islet β-cell dedifferentiation in aged rats with type 2 diabetes(T2DM). Methods Forty 2-month-old male SD rats were adaptively fed for 1 week, then randomly divided into the control group (control,CON, n=10) and the aging T2DM model group (n=30). The aging T2DM model group rats were fed a high-sugar and high-fat diet and intraperitoneally injected with 50 mg/kg D-galactose daily. After 4 weeks, the aging T2DM model group rats were given a single intraperitoneal injection of 30 mg/kg streptozotocin (STZ). After 2 weeks STZ injection, fasting blood glucose (FBG) greater than or equal to 16.7 mmol/L was defined as successful T2DM model. The successful model rats were randomly divided into aging T2DM group (model, MOD), 300 mg/kg TP group (TP) and 3 mg/kg rosiglitazone group (RSG) according to FBG, with 10 rats in each group. Rats were treated with 50 mg/kg D-galactose and fed with the high-sugar and high-fat diet in the following 8 weeks. Western blot was used to detect the expression of P53 protein in pancreatic tissue of the model group at the end of the experiment, which was higher than that of the CON group, indicating that the aging T2DM model was successfully established. FBG was measured by the blood glucose meter, fasting serum insulin by ELISA, HOMA-IR and HOMA-β calculated. The pathological changes of pancreas were observed after HE staining, and the protein expression of Pdx1, MafA, Ngn3, FoxO1 and p-FoxO1 in the pancreas was detected by Western blot. Results Compared with the CON group, the level of FBG and the expression of P53 in the MOD group were increased (P<0.01). The expression of Pdx1, MafA and the ratio of p-FoxO1/FoxO1 were reduced(P<0.01). The expression of Ngn3 was increased (P<0.01). The level of HOMA-IR was increased (P<0.01). The level of HOMA-β was reduced (P<0.01). The pancreatic tissue showed irregular islet shape, enlarged islet area and blurred boundary with surrounding tissue. Some islet cells had loose or vacuolated cytoplasm. Compared with the MOD group, the expression of P53 and the level of FBG in the rats treated with TP were down-regulated (P<0.05, P<0.01). The expression of Pdx1, MafA and the ratio of p-FoxO1/FoxO1 were increased (P<0.01, P<0.05, P<0.05). The expression of Ngn3 was reduced (P<0.01). Meanwhile, the level of FBG in the rats treated with RSG were down-regulated (P<0.05). The expression of Pdx1, MafA and the ratio of p-FoxO1/FoxO1 were increased (P<0.01, P<0.05, P<0.05). The expression of Ngn3 was reduced (P<0.05). The level of HOMA-IR in the rats treated wih TP or RSG was reduced (P<0.05). In addition, the islet shape was improved, the islet area was smaller, and the degree of loose cytoplasm or vacuolization of islet cells was reduced. Conclusion TP can improve the dedifferentiation of islet β cells in the aged T2DM model rats, and its mechanism is related to up-regulatd phosphorylation level of FoxO1.