Effects of intermittent high glucose on apoptosis and PTEN expression in islet cells

AIM: To investigate whether the increase in PTEN expression is related to apoptosis, and whether it is regulated by reactive oxygen species(ROS). METHODS: The rat islet cells were divided into constant low glucose group (group L), constant high glucose group (group H), glucose fluctuation group (group F), low glucose after high glucose group (group HL) and low glucose after fluctuation group (group FL). The ROS level, apoptotic rate, intracellular calcium, insulin release and PTEN protein expression were analyzed. RESULTS: Compared with groups H and L, the insulin secretion decreased, and intracellular calcium, ROS level, PTEN protein expression and apoptotic rate increased in group F (P<0.05). Compared with group H, the intracellular calcium, ROS level, PTEN protein expression and apoptotic rate in group HL decreased, but were still higher than those in group L (P<0.05). Compared with group F, the intracellular calcium, ROS level, PTEN protein expression and apoptotic rate in group FL decreased, but were still higher than those in group L (P<0.05). CONCLUSION: Glucose fluctuation can cause the apoptosis of islet cells more easily than constant high glucose. This may be related to the change of intracellular calcium and increase in oxidative stress which promotes PTEN expression. The recovery of glucose level to some extent relieves oxidative stress, decrease PTEN expression and reduce cell damage.     

Anti-apoptosis effect of liraglutide on islet via regulating microRNA-375

AIM: To observe the anti-apoptosis effect of liraglutide on the islet through microRNA-375 (miR-375) for providing additional pharmacodynamic evidence for its clinical application. METHODS: For in vitro study, C57BL/KsJ-db/m mice aged 8 weeks served as normal control group. A total of 40 male genetically diabetic C57BL/KsJ-db/db mice at the same age were randomly divided into diabetic control group （the db/db mice were injected subcutaneously with equivalent amount of saline) and liraglutide group (the db/db mice were injected subcutaneously with liraglutide at dose of 300 μg·kg^-1·d^-1). After 8 weeks of administration, body weight (BW) was measured and blood was collected for detection of fasting blood glucose (FBG), fasting blood insulin (FINS), triglyceride (TG), total cholesterol (TC) and low-density lipoprotein cholesterol (LDL-C). Before sacrifice, intraperitoneal glucose tolerance test (IPGTT) and insulin tolerance test (ITT) were conducted. The histopathological features in the islet tissue were examined with HE staining. The apoptosis in the islet tissue was detected by TUNEL staining. The protein levels of caspase-3, Bcl-2 and Bax were determined by Western blot. The level of miR-375 in the islet tissue was detected by qPCR. Forin vitro study, the MIN-6 cells were cultured and divided into control group (incubated with equivalent amount of solvent), miR-375 mimic group and miR-375 mimic+ liraglutide group. The cell viability was examined by MTT assay. The protein levels of caspase-3, Bcl-2 and Bax were detected by Western blot. RESULTS: In thein vitro study, compared with control group, the levels of BW, FBG, FINS, TC, TG and LDL-C were decreased significantly in liraglutide group. The islet apoptosis was reduced by the administration of liraglutide. The expression of Bcl-2 was up-regulated significantly, while the protein levels of caspase-3 and Bax were down-regulated significantly in liraglutide group. The level of miR-375 was decreased significantly. In the in vitro study, the cell viability was decreased in miR-375 mimic group and increased in miR-375 mimic+liraglutide group. Moreover, the expression of Bcl-2 was decreased and the protein levels of caspase-3 and Bax were increased with the incubation of miR-375 mimic, while the expression of Bcl-2 was increased and the protein levels of caspase-3 and Bax were decreased with the co-incubation of miR-375 mimic and liraglutide. CONCLUSION: Liraglutide attenuates islet apotosis, and the mechanism may be associated with its effects of reducing the elevated level of miR-375 in islet tissues.     

水库种草养鱼与防淤的试验初报

为了充分开发利用水库水资源养鱼和减少库内泥砂淤积，保护和改善水库生态环境，作者在库内消落区、荒山提坝及幼林间人工种植杂交黑麦草、象草、扁穗牛鞭草等鱼用高产优质饲草养鱼与防淤进行了试验研究，获得成功。库内鲜鱼产量由种草前常年1000公斤左右提高7000-8000公斤，泥砂淤积每年减少0.516万立方米。结果表明，采用这一方法对解决库内养鱼长期饵料缺乏，提高库内鱼产量，减少库内泥砂淤积，具有投资少、周期短、效果好的优点。