| Objective:To explore the possible mechanisms for their effects of islet B cell function by studying the interaction between Nrf2/ARE pathway and IRS-2. Methods:80 male Wistar rats were randomly divided into two groups include normal control group (NC group, n=20) and experimental group (n=60). Rats in NC group were fed normal fat diet (NFD) mixed with 1% flour (w/w)without drug intervention. Rats in experimental group were fed high-sucrose and high-fat diet for 4 weeks and then induced by a single intraperitoneal injection of streptozotocin (30mg/kg BW). Finally, type 2 diabetes models were established successfully in 40 rats.40 rats were randomly divided into diabetic model group (DM group, n=20) and tertiary-Butylhydroquinone (tBHQ group, n=20). Rats in DM group and tBHQ group were respectively fed high-sucrose and high-fat diet mixed with 1% flour (w/w) without drug intervention and 1%tBHQ for 8 weeks. During the intervention,1ml blood via tail vein were collected once a week for determination of fasting blood glucose (FBG) and fasting insulin (FINS) level. 5 rats were selected and evaluated the function of islet B cells using intravenous glucose insulin release test (IVG-IRT) by the end of eighth week. Then all rats were killed and blood samples were collected for determination of serum malonaldehyde (MDA), tumor necrosis factor-a (TNF-a) and total-superoxide dismutase (T-SOD) levels. Pancreatic tissues were collected from each group rats for observation of morphological structure of islet cells.Apoptosis of islet cells were detected by TUNEL method. The fluorescence distribution and expression of Nrf2, p-IRS-2, p-AKT and Insulin in islet cells were detected by immunofluorescence labeling technique. The protein expression levels of total Nrf2, nulear Nrf2, IRS-2, p-IRS-2, AKT and p-AKT in pancreatic tissues were detected by Western blot and MDA, TNF-α and T-SOD levels in pancreatic tissues were detected by ELISA. Results:1.Compared with NC group, FBG and FINS levels were significantly increased and decreased in DM group during 0-8 weeks respectively (P<0.01). Compared with DM group, FBG and FINS levels were significantly decreased and increased in tBHQ group during 0-8 weeks respectively (P<0.01).2.Rats in DM group had significantly lower islet B cell function indexes and insulin sensitivity index (ISI) and higher HOMA-insulin resistance index (HOMA-IR) than in NC group (P)<0.01). Rats in tBHQ group had significantly higher islet B cell function indexes and improvement of ISI and HOMA-IR than in DM group (P<0.01).3.Compared with NC group, the number of islets were decreased and islet cell apoptosis rate were increased in DM group (P<0.01). Compared with DM group, the number of islets were increased and islet cell apoptosis rate were decreased in tBHQ group (P<0.01).4.Rats in DM group had significantly lower fluorescence distribution and expression of p-IRS-2, p-AKT, Nrf2 and Insulin in islet cells than in NC group. Rats in tBHQ group had significantly higher fluorescence distribution and expression of p-IRS-2, p-AKT, Nrf2 and Insulin in islet cells than in DM group.5.Rats in DM group had significantly lower protein expression of total Nrf2, nulear Nrf2, IRS-2 and phosphorylation levels of IRS-2, AKT than in NC group (P<0.01). Rats in tBHQ group had significantly higher protein expression of total Nrf2, nulear Nrf2, IRS-2 and phosphorylation levels of IRS-2, AKT than in DM group (P<0.01). The protein expression of AKT had no statistically significant difference among the three groups (P0.05).6.Compared with NC group, serum and pancreatic tissue MDA, TNF-a levels were significantly increased and T-SOD levels were significantly decreased in DM group (P<0.01). Compared with DM group, serum and pancreatic tissue MDA, TNF-a levels were significantly decreased and T-SOD levels were significantly increased in DM group (P<0.01). Conclusions: 1.Sustained high-sucrose and high-fat diet can cause IRS-2 oxidative stress and chronic inflammation injury, which led to IR, apoptosis and functional decline of islet B cells.2.Activating Nrf2/ARE pathway can ameliorate IRS-2 oxidative stress and chronic inflammation injury to ameliorate IR and maintain the stability of number and function of islet B cells through upregulating the expression of phase II detoxifying enzymes and antioxidant enzymes.3.There may be IRS-PI3K/AKT-Nrf2/ARE signal transduction pathway in islet B cells. |
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