## 2 Results
### Effect on Insulin Secretion in HG-Stimulated \(\beta\)-Cells  
To examine whether glucotoxicity increases dysfunction of insulin secretion, we incubated RIN-m5f cells with HG for 24 h. Results in Figure 5 show that after 24 h cultivation  
Figure 3: Effect of SOE on the production of antioxidant enzymes and GSH in RIN-m5f \(\beta\)-cells under HG induction. (**A**) catalase, (**B**) GPx, (**C**) SOD, and (**D**) GSH. The \(\beta\)-cells were cultivated in 6-well plates at a density of 5 \(\times\) 10\({}^{5}\) cells/well for 24 h, and the indicated concentration of SOE was added under the stimulation of 50 mM or 100 mM glucose. After 24 h treatment, the cell extracts were prepared according to the manufacturer’s instruction. The protein content was measured using the Bicinchinic Acid Protein Assay Kit. The assay of the activities of catalase, GPx, SOD, and the content of GSH were performed according to manufacturer’s instructions with Sigma-Aldrich Assay Kits. The experimental data were calculated from the results of three repeated experiments. The statistically significant differences compared with the vehicle (group 0) are expressed as * \(p\) < 0.05, **_p_ < 0.01, and **_p_ < 0.001. The positive control was 50 \(\upmu\)M Metformin.  
in a 50 mM HG condition, the intracellular insulin secretion rose to 110.1%. When these cells were treated with SOE, the insulin secretion was decreased as SOE concentration increased and returned to the normal value (101.2%) when the SOE concentration reached 250 \(\upmu\)g/mL. On the other hand, when cells were incubated in a higher concentration of glucose (100 mM), insulin secretion dropped to 85.0%. Treatment with SOE prevented the trend and returned the insulin secretion to near the normal value (94.2%) when the concentration of SOE was 250 \(\upmu\)g/mL. These findings indicate that SOE possesses the regulation function on pancreatic \(\beta\)-cell insulin secretion under HG condition.  
Figure 4: Effect of SOE on the production of antioxidant enzymes (catalase, GPx, and SOD) in RIN-m5f \(\beta\)-cells under HG stimulation. (**A**) Changes in protein expression of the three antioxidant enzymes. (**B**) Densitometric quantitation. The \(\beta\)-cells were cultivated for 24 h and then treated with various concentrations of SOE for 24 h under the stimulation of 100 mM glucose. The obtained cell extracts were subjected to electrophoresis on SDS-PAGE gel, followed by an enzyme immunoassay and ECL for detection. The internal standard was \(\beta\)-actin. Densitometric analysis was also performed. The experimental data were calculated from the results of three repeated experiments. The statistically significant differences compared with the vehicle (group 0) are expressed as *** \(p<0.001\).  
Figure 5: Effect of SOE on insulin secretion in RIN-m5f \(\beta\)-cells under HG induction. The \(\beta\)-cells were cultivated at a density of 5 \(\times\) 10\({}^{5}\) cells/well for 24 h, and then the specified concentration of SOE was added under the stimulation of 50 mM or 100 mM glucose. After 24 h treatment, the cell solution was replaced by Krebs–Ringer buffer and conducted the insulin secretion measurement by Rat/Mouse Insulin ELISA Kit. The experimental data were calculated from the results of five repeated experiments. The statistically significant differences compared with the vehicle (group 0) are expressed as * \(p<0.05\), *** \(p<0.01\), and *** \(p<0.001\). The positive control was 50 \(\upmu\)M Metformin.