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.     

DHA induced cytotoxicity in NSCLC cells via inhibiting PI3K pathway activation and GLUT2 expression

AIM: To investigate the molecular mechanisms of cytotoxicity induced by dihydroartemisinin (DHA) in non-small cell lung cancer (NSCLC) cells. METHODS: NSCLC cell lines A549 and NCI-H1650 were treated with various concentrations of DHA for indicated time. Subsequently, the effects of DHA on the cell activity, colony formation ability and apoptosis were determined by MTT assay, colony formation assay, Annexin V-FITC/PI staining and flow cytometry, respectively. At the same time, the effects of DHA on glucose, ATP and lactate levels were assessed, and the PI3K pathway activation and glucose transporter 2(GLUT2) expression were detected by Western blot in the A549 cells and NCI-H1650 cells. Overexpression of GLUT2 and Rheb was established in A549 and NCI-H1650 cells by transfection with GST-GLUT2 and GST-Rheb plasmids, respectively, and the effects of DHA on cell activity, apoptosis, glucose level, ATP content and PI3K pathway activation were analyzed in A549 cells and NCI-H1650 cells. The effect of glucose deprivation on the cytotoxicity triggered by DHA in NSCLC cells was also determined. RESULTS: Compared with control group, DHA significantly inhibited cell activity and colony formation ability, and induced remarkable cell apoptosis in the A549 cells and NCI-H1650 cells. At the same time, DHA reduced ATP and lactate contents, and hindered glucose uptake in a time-and dose-dependent manner in A549 cells and NCI-H1650 cells. The activity of PI3K pathway and GLUT2 expression were downregulated, while upregulated GLUT2 expression and activated PI3K pathway reduced the cytotoxicity induced by DHA in NSCLC cells. Glucose deprivation increased DHA-mediated cytotoxicity in NSCLC cells. On the contrary, high levels of glucose inhibited DHA-mediated cytotoxicity in NSCLC cells. CONCLUSION: DHA restrains cell activity and colony formation, and induces apoptosis. DHA induces cytotoxicity via inhibiting PI3K pathway activation and GLUT2 expression, leading to inhibit glycolytic metabolism in NSCLC cells.     

Insulin, glucagon, and leptin in critically ill foals

Background: Endocrine dysregulation of hormones of energy metabolism is well documented in critically ill humans, but limited information exists in septic foals. The purpose of this study was to provide information on the hormonal response to energy metabolism in critically ill foals, focusing on insulin, glucagon, and leptin. Hypothesis: Concentrations of insulin, glucagon, leptin, and triglycerides will be higher, whereas glucose concentration will be lower in septic foals than in healthy and sick nonseptic foals. The magnitude of these differences will be associated with severity of disease and nonsurvival. Animals: Forty‐four septic, 62 sick nonseptic, and 19 healthy foals <7 days of age. Methods: In this prospective multicenter cross‐sectional study, blood samples were collected at admission. Foals with positive blood culture or sepsis score ≥12 were considered septic. Results: Septic foals had lower glucose and insulin and higher triglyceride and glucagon concentrations than did healthy foals. Glucagon concentrations were not different between septic foals that died (n = 14) or survived (n = 30). Higher insulin and lower leptin concentrations were associated with mortality. Quantitative insulin‐sensitivity check index was higher in septic foals. Conclusions and Clinical Importance: Energy metabolism and the endocrine response of related hormones in septic foals are characterized by hypoglycemia, hypertriglyceridemia, low insulin concentration, and high glucagon concentration. Leptin and insulin may have prognostic value for nonsurvival in septic foals. The hormonal response related to energy metabolism in critical illness differs between foals and humans.     

Short-term temperature dependence of heterotrophic soil respiration after one-month of pre-incubation at different temperatures

Quantification of microbial activities involved in soil organic carbon (SOC) decomposition is critical for the prediction of the long-term impact of climate change on soil respiration (SR) and SOC stock. Although the temperature sensitivity of SR is especially critical in semi-arid regions, such as North West Tunisia, where the SOC stock is low, little research has been carried out in these environments. More needs to be known about factors, such as SOC availability that influence temperature sensitivity. In this study, soil samples were incubated with and without glucose addition for 28 days after a 28-day pre-incubation period. Pre-incubation and incubation was carried out at 20 °C, 30 °C, 40 °C and 50 °C. Respiration measurements were taken with temperature, glucose addition and incubation time as independent variables. The highest pre-incubation temperature reduced the temperature sensitivity of SR during the subsequent incubation period, both with and without glucose addition. Soil samples pre-incubated at 50 °C had the lowest SR at all subsequent incubation temperatures and the lowest temperature sensitivity of SR, even after glucose addition. However, after glucose addition, the effect of a high pre-incubation temperature on soil respiration lasted only two days. Measuring the water-soluble carbon (WSC) in soil samples suggested that the high pre-incubation temperature may have killed part of the microbial biomass, modified microbial communities or solubilized SOC. For quantifying the possible effect of global warming, in particular heat waves, on soil respiration in the soil studied, the results indicate a moderate response of soil respiration to temperature at high temperatures, as shown by Q₁₀ close to 1.7, even in the range 40-50 °C.     

Effects of castration-induced visceral obesity and antioxidant treatment on lipid profile and insulin sensitivity in New Zealand white rabbits

Molecular mechanisms, responsible for the impaired insulin-sensitivity state due to the obesity are not fully understood in both humans and animals. The purpose of this study was to investigate the effects of castration-induced visceral obesity and the influence of two antioxidants on constituents of blood lipid profile and insulin sensitivity in New Zealand white rabbits. Twenty-six clinically healthy male New Zealand white rabbits were used in the experiment and were divided into 3 groups: first group (CI, n = 7) - castrated-obese and treated with antioxidants “Immunoprotect” for 2 months; second group (CO, n = 7) - castrated-obese; third group (NC, n = 12) - control group (non-castrated, non-obese). At the end of the follow-up period of 2 months after castration an intravenous glucose tolerance test (IVGTT) was performed after a 12-h fasting period as the blood samples for determination of glucose and insulin and their kinetic parameters were obtained at 5 and 0 min before and at 5, 10, 30, 60 and 120 min after the infusion of the glucose. The constituents of lipid profile, triglycerides (TG), total cholesterol (TC) and HDL-cholesterol (HDL-C) were also assessed in the overnight fasting blood samples. The body weight (BW), body mass index (BMI), amount of the visceral fat (VF) and VF/BW ratio were both measured and calculated before the IVGTT and at the end of the experimental period. All measured markers of obesity (BW, BMI, VF, VF/BW) were significantly higher in both groups of castrated rabbits than in the control group. Apart HDL-C, the plasma concentrations of all constituents of lipid profile (TG, TC, HDL-C) were the highest in CO group. There were generally no differences between CI and NC groups for the same traits. After glucose injection blood glucose concentrations and glucose and insulin kinetic parameters were considerably higher (except of glucose elimination rate) in CO rabbits than in NC ones. Castrated rabbits treated with “Immunoprotect” showed lower fasting plasma insulin and improved glucose kinetics dynamics than CO rabbits, but commensurable values of glucose and insulin kinetics parameters than NC group. The results of the current study clearly indicated that castration-induced visceral obesity affected negatively the lipid profile and insulin sensitivity and/or responsiveness. Treatment with antioxidant supplementation, consisted of d-limonene and vitamin E, improved blood lipid profile, fatty liver, glucose homeostasis and insulin sensitivity in obese rabbits. In addition, based on our results we may suggest that castrated male New Zealand white rabbits might be considered as an appropriate animal model to study various metabolic abnormalities related to visceral obesity, such as dyslipidemia and impaired insulin sensitivity.     

Influence of high-fat environment on glucose metabolism in rat myoblasts

AIM: To explore the effects of high-fat environment on glucose metabolism in rat myoblasts. METHODS: The rat myoblasts were exposed to palmitic acid (PA) at concentrations of 0.1 mmol/L, 0.3 mmol/L or 0.5 mmol/L for 6 h, 12 h or 24 h. The viability of the cells was determined by MTT assay. The oil red O dyeing method was used to display triglyceride (TG) sediment in the cells. Triglyceride content in the cells was measured by glycerophosphate oxidase-peroxidase(GPO-POD) method. The uptake of 2-deoxy-D- glucose ( -G) in rat myoblasts was determined by isotope tracer method. RESULTS: After exposed to PA at concentrations of 0.1~0.5 mmol/L for 6~24 h, the viability of rat myoblasts decreased, TG sediment and content increased,and -G uptake was inhibited in a concentration-and time-dependent manner. Compared with control group, the cell viability, TG sediment and content, and -G uptake were significantly changed in 0.3 mmol/L PA group (24 h) and 0.5 mmol/L PA groups (12 h and 24 h). CONCLUSION: With the elevating concentration of PA exposure, TG sediment increases and glucose uptake decreases in rat myoblasts.     

不同温度贮藏红肉脐橙果肉主要色素和糖含量的变化及其相关性

研究了红肉脐橙果实贮藏过程中果肉主要色素和糖含量的变化。结果表明,室温贮藏的果实番茄红素含量为单峰曲线,于1月28日达到最大值,为47.19μg.g-1FW,β-胡萝卜素含量出现3次高峰,于3月23日达到最大值,为37.35μg.g-1FW;6℃冷库恒温贮藏的果实番茄红素含量高峰较室温贮藏滞后出现,且含量明显高于室温贮藏(2月17日,55.92μg.g-1FW),β-胡萝卜素含量变化趋势与室温贮藏基本一致,但高峰出现时间(1月28日)较室温贮藏滞后;6℃冷库恒温贮藏有利于贮藏前期(12月25日~1月28日)各种糖的积累,但不利于贮藏后期糖的积累(蔗糖除外)。