Intermittent High Glucose Group Research Articles

Acute glucose fluctuation promotes in vitro intestinal epithelial cell apoptosis and inflammation via the NOX4/ROS/JAK/STAT3 signaling pathway.

High blood glucose commonly occurs in patients with diabetes mellitus, but little is known of its effects on intestinal epithelial cells, or its associated mechanisms of action therein. In the present study, intestinal epithelial cells were assigned to five groups: i) The normal glucose (NG) group, incubated in 5.0 mmol/l glucose; ii) the constant high glucose (CHG) group, treated with 25.0 mmol/l glucose; iii) the intermittent high glucose (IHG) group, treated with alternating doses of 5.0 and 25.0 mmol/l glucose every 8 h; iv) the mannose group, cultured in 25.0 mmol/l mannose (the osmotic control); and v) the IHG glucose + GKT137831 group, pretreated with 100 nmol/l NADPH oxidase 4 (NOX4) inhibitor, GKT137831, and then exposed to IHG. TNF-α, IL-1 and IL-6 levels were quantified using ELISA kits. Intestinal epithelial cell apoptosis was assessed by flow cytometry and oxidative stress was evaluated by reactive oxygen species (ROS) and malondialdehyde (MDA) detection. The expression levels of proteins associated with apoptosis and involved in the signal transduction of Janus kinase (JAK)/STAT3 pathway were assessed using western blot analysis. The results indicated that NOX4 expression was significantly higher in the CHG group than in the NG group (P<0.01), but lower than in the IHG group (P<0.001). The IHG group exhibited apoptosis and oxidative stress accompanied by the most significant increase in MDA, ROS and inflammatory cytokine levels (P<0.001), which was followed by that of the CHG group. Additionally, the IHG group exhibited reduced Bcl-2, as well as enhanced Bax and cleaved caspase-3 levels compared with the CHG group (P<0.001). Furthermore, the level of phosphorylated (p-)JAK/p-STAT3 was increased to a greater extent in the IHG group than in the CHG group (P<0.001). In conclusion, the findings of the present study indicated that CHG may trigger intestinal epithelial cell apoptosis and inflammation through the NOX4/ROS/JAK/STAT3 pathway, which may be aggravated by acute glucose fluctuation.

Effect of intermittent high glucose on oxygen-glucose deprivation/refurnish neuronal survival

To investigate the effect of intermittent high glucose on oxygen-glucose deprivation/refurnish (OGD/R) neuronal survival. The primary cultured hippocampal neurons of mice were sub-cultured when the cell fusion reached about 80%. Cells in logarithmic growth phase were placed in a hypoxic incubator (37 centigrade, 5% CO2, 95% N2) to simulate cell hypoxia. The culture medium was replaced by glucose-free Hank equilibrium salt solution (HBSS) to simulate cell hypoglycemia. The normal glucose and oxygen control group was set up. Cell morphology was observed under inverted phase contrast microscope after 6 hours of hypoxia and hypoglycemia treatment, and cell viability was detected by CCK-8 cell proliferation assay kit, and then grouping experiment was carried out. The cells were randomly divided into four groups. The cells were cultured in different concentration glucose medium under normal oxygen, 5% CO2 and 37 centigrade for 72 hours to prepare OGD/R model of cell ischemia/reperfusion. The low-glucose control group was cultured in medium containing 5.5 mmol/L glucose. The constant high-glucose group was cultured in medium containing 33.0 mmol/L glucose. The intermittent high-glucose group was cultured in medium containing 33.0 mmol/L glucose for 3 hours then in medium containing 5.5 mmol/L glucose for 2 hours alternately for 3 times during the day, and overnight in medium containing 33.0 mmol/L glucose at night. The hyperosmotic control group was made up of 5.5 mmol/L glucose medium and mannitol. The osmotic pressure was the same as that of the constant high-glucose group, and the effective glucose concentration was the same as that of the normal glucose and oxygen group, so as to eliminate the effect of osmotic pressure changes caused by the high-glucose medium on the results. Cell morphology was observed under inverted phase contrast microscope after 72 hours of cell culture in each group. Cell viability was measured by CCK-8 kit, and apoptotic rate was measured by flow cytometry. The inverted phase contrast microscope showed that the cells in the normal glucose and oxygen control group were plump and refractive, and had obvious nucleus, clear processes and high cell activity. After 6 hours of hypoxia and hypoglycemia treatment, the cells were shrunk, refractive index was poor, the nucleus was unclear, the processes were not clear, and the cell activity was significantly lower than that of normal glucose and oxygen control group (A value: 0.34±0.06 vs. 1.09±0.06, P < 0.01), which indicated that the model of oxygen-glucose deprivation (OGD) was successfully prepared. After 72 hours of culture with different concentrations of glucose, the cells in the low-glucose control group were shrunk, the cell membrane was incomplete, the nucleus was unclear, and number of necrotic cells were more. In the constant high-glucose group, the refractive index of cells was poor, a large number of cells floated, and the nucleus was not obvious. In the intermittent high-glucose group, the cell morphology was normal, the refractive rate of cells was decreased slightly, and the necrotic cells were less. In the hypertonic control group, the cell status was close to that in the constant high-glucose group. Compared with the low-glucose control group or constant high-glucose group,the cell viability in the intermittent high-glucose group was significantly increased (A value: 2.04±0.15 vs. 0.64±0.18, 1.16±0.16, both P < 0.01), the apoptotic rate was significantly decreased [(59.60±2.55)% vs. (78.15±15.77)%, (95.60±0.14)%, both P < 0.05]. There was no significant difference in cell activity or apoptotic rate between the hypertonic control group and the constant high-glucose group [cell activity (A value): 1.07±0.07 vs. 1.16±0.16, apoptotic rate: (87.80±4.53)% vs. (95.60±0.14)%, both P > 0.05]. Intermittent high glucose within a certain range had protective effect on OGD/R neuronal survival.

GW24-e3984 Effects of tetramethylpyrazine on human umbilical vein endothelial cells exposed to constant or intermittent high glucose in vitro

ObjectivesTo explore the influence of constant or intermittent high glucose on human umbilical vein endothelial cells (HUVECs), and the effects of tetramethylpyrazine (TMP) on HUVECs exposed to constant or intermittent...

The effect of resveratrol on the expression of adiponectin receptors in intermittent high glucose-cultured rat mesangial cells

Objective To study the effects and mechanisms of resveratrol (Resv) on the expression of adiponectin receptors ( AdipoR1 and AdipoR2 ) in rat mesangial cells (MCs) cultured in intermittent high glucose medium.Methods The MCs cultured in normal glucose ( 5.6 mmol/L) medium were transfected by the plasmid vector of the FoxO1 short hairpin RNAs ( FoxO1 shRNA ),and then cultured in intermittent high glucose medium (5.6mmol/L or 30 mmol/L,alternately every 8 hours ) and resveratrol ( Resv 20 μmol/L).The MCs cultured in normal glucose (5.6 mmol/L) medium served as normal glucose control group (NG),and the MCs exposed to iutermittent high glucose medium were divided into five groups:intermittent high glucose group (IHG),IHG+Resv group,IHG+FoxO1 shRNA group,IHG+ Resv + FoxO1 shRNA group,IHG + Negative control group ( shNC ),each group was cultured for 72 h.The level of reactive oxygen species (ROS) was assessed by Fluorescence microplate reader.The mRNA levels of Sirt1,Foxo1,AdipoR1,and AdipoR2 were assessed by RT-RCR.The protein levels of FoxO1,phosphorylation FoxO1 ( p-FoxO1 ),AdipoR1,and AdipoR2 were assessed by Western blotting.Results ( 1 )Compared with NG,intermittent high glucose significantly decreased the mRNA expression of Sirt1,but markedly increased the level of p-FoxO1.Furthermore,the mRNA and protein expression levels of AdipoR1 were obviously decreased while the level of ROS was enhanced in IHG ( all P＜0.05 ).(2) Compared with IHG,the mRNA and protein expression levels of FoxO1 and AdipoR1 were inhibited,but the level of ROS was enhanced in group IHG+FoxO1 shRNA ( all P＜0.05 ).( 3 ) Compared with IHG,after treating with Resv,the mRNA expression level of Sirtl was increased,whereas the level of p-FoxO1 was decreased.Moreover,the mRNA and protein levels of AdipoR1 was increased while the level of ROS was lowered in group IHG+Resv (all P＜0.05 ).(4) Compared with group IHG+Resv,the mRNA and protein levels of FoxO1 and AdipoR1 were inhibited,but the level of ROS was increased in group IHG+Resv+FoxO1 shRNA (all P＜O.05).(5) In addition,the mRNA and protein expression level of AdipoR2 showed no significant difference among these groups ( P＞0.05 ).Conclusion ( 1 ) Resveratrol significantly increases the expression of AdipoR1 in MCs induced by intermittent high glucose.( 2 ) FoxO1 plays an important role in regulating the expression of AdipoR1 by resveratrol. Key words: Resveratrol; Intermittent high glucose; Adiponectin receptor; Forkhead transcription factor O1

Involvement of JNK signal transduction pathway in endothelial cell apoptosis induced by intermittent high glucose

To evaluate the effect of intermittent high glucose on the apoptosis of human umbilical vein endothelial cells (HUVECs) and its mechanism. Intermittent high glucose and constant high glucose were applied to HUVEC-12 for 7 days. Flow cytometer and fluorescent staining with Hoechst 33258 were used to detect apoptosis of HUVEC-12. The superoxide dismutase (SOD) activity and the content of malonaldehyde (MDA) in culture solution were detected with colorimetry, and the changes of p-JNK level were examined by Western blot. The apoptosis rate was obviously higher in the intermittent high glucose group than that in the constant high glucose group (P < 0.05). The SOD activity was significantly lower in the intermittent high glucose group (P < 0.05), but MDA level was higher than those of constant high glucose(P < 0.05). SP600125, the inhibitor of JNK, decreased the apoptosis rate induced by intermittent high glucose (P < 0.05). Antioxidant (Vitamin C) inhibited the p-JNK, decreased the apoptosis rate (P < 0.05). Intermittent high glucose is easier to worsen the proapoptotic effects on HUVECs than that of constant high glucose, which may account for the increased oxidative stress, and then activates JNK signal transduction pathway.

Effect of intermittent high glucose on synthesis of nitric oxide in human umbilical vein endothelial cells and its mechanism.

To compare the effect of intermittent and constant high glucose media on the synthesis of vascular relaxing factor nitric oxide (NO) in cultured human umbilical vein endothelial cells (HUVECs), and to investigate its mechanism. HUVECs were exposed to 5.5 mmol/L glucose (normal control), 20 mmol/L glucose (constant high glucose), and 5.5 mmol/L alternating with 20 mmol/L glucose (intermittent high glucose) for 7 days. The NO level was measured using Griess Reaction in cell culture supernatants; the expressions of PI3K, PKB and eNOS mRNA and protein were measured with RT-PCR or Western blot. NO level in the intermittent high glucose group was significantly lower than that in the constant high glucose group (P<0.05). The expression of PI3K, PKB, and eNOS in the intermittent high glucose group was significantly lower than that in the constant high glucose group (P<0.05). Intermittent high glucose could be more deleterious to endothelial cells than constant high glucose, and may lead to decrease synthesis of NO by inhibiting PI3K/PKB/eNOS pathway activation.

Impairment of pancreatic islet beta cell function induced by intermittent high glucose through oxidative and endoplasmic reticulum stress: experiment with rat pancreatic islet beta cells

To investigate the effect of intermittent high glucose (IHG) on the pancreatic islet beta-cell function and mechanism thereof. Rat pancreatic islet p-cells of the line INS-1 were cultured and randomly divided into 3 groups: IHG group exposed to fluctuating concentrations of glucose, stable high glucose (SHG) group exposed to 16. 7 mmol/L glucose, and control group exposed to normal concentration (5.5 mmol/L) glucose. 24, 48, and 72 hours later radioimmunoassay was used to detect the insulin secretion index (ISI). 72 h later, the concentration of insulin in the cells was detected with radioimmunoassay. The contents of oxidative stress markers, nitrotyrosine (NT) and 8-hydroxy-2-deoxyguanosine (8-OHdG) were detected. Real-time PCR was used to detect the mRNA expression of peroxiredoxin 1 (PDX-1), ATF-4, one of the transcription factors of the family bZIP, and insulin. Western blotting was used to detect the protein expression of ATF-4. The ISI of the IHG and SHG groups decreased time-dependently, The ISI of IHG and SHG groups were 0.64 +/- 0.11 and 1.31 +/- 0. 04 respectively, both significantly lower than that of the control group (1.67 +/- 0.23, both P < 0.05). The intracellular insulin contents of the IHG and SHG groups were (10.91 +/- 0.14) and (11.08 +/- 0.03) +/- U/microg respectively, both significantly lower than that of the control group [(12.37 +/- 0.37) microU/microg, both P < 0.05]. The intracellular concentrations of 8-OHdG and NT of the SHG and IHG groups, were significantly higher than those of the control group (all P < 0.01), and those of the IHG group were significantly higher than those of the SHG group (both P < 0.05). The mRNA and protein expression levels of ATF-4 of the IHG group were all significantly higher than those of the control group (all P < 0.05) and those of the IHG group were significantly higher than those of the SHG group (both P < 0.05). IHG and SHG induce severe impairment in pancreatic islet beta cell functions, especially IHG, which is closely associated with the aggravation of oxidative stress and endoplasmic reticulum stress triggered by intermittent high glucose.