Preliminary Study On The Treatment Effect And Mechanism Of SGK1 Inhibitor On Hyperglycemia

Part One Preliminary study on the treatment effect and mechanism of SGK1 inhibitor on hyperglycemiaObjective:To investigate the treatment effect of SGK1 inhibitor on carbohydrate metabolism disorders, and to explore whether the possible mechanism is due to the effect of ameliorating the state of insulin resistance, reducing glucose absorption in small intestine.Methods:Db/db mice were randomized to control group (db/db group), SGK1 inhibitor group. The intervention lasted for 8 weeks. During the intervention period, fasting blood glucose and body weight were checked every week. Food intake was investigated every two weeks. Glycosylated hemoglobin (HbAlC) was tested at week 4 and 8. At week 8, intraperitoneal glucose tolerance test (IPGTT) and intraperitoneal insulin tolerance test (IPITT) were conducted. After intervention, the mice were killed. Blood serum and different tissues were collected and stored to further examation. Homeostasis model assessment of insulin resistance (HOMA-IR) and insulin sensitivity index (ISI) were calculated. The SGK1 and sodium glucose cotransporterl (SGLT1) expression were further investigated in the small intestine of db/db mice using quantitative real-time PCR and Westeren blot analysis.Results:(1) Body weight:SGK1 inhibitor group had a lower body weight compared to db/db control group (p<0.05). (2) Food intake:No significant difference was detected between SGK1 inhibitor group and db/db control group. (3) Parameters of glucose metabolism:SGK1 inhibitor treatment significantly decreased fasting blood glucose and HbAlC (p<0.05). IPGTT showed that SGK1 inhibitor group had lower blood glucose level at 30,60,120min and smaller area under curve (AUC) of blood glucose (p<0.05). (4) Insulin resistance:IPITT showed that SGK1 inhibitor group had lower blood glucose level at 0,120,150,180min than db/db control group (p<0.05). Compared with db/db control group, SGK1 inhibitor group had lower fasting insulin level, which significantly decreased HOMA-IR and increased ISI in SGK1 inhibitor group (p<0.05). (5) SGK1, SGLT1 mRNA and protein expression were both increased in small intestine of db/db mice than in wild-type mice (p<0.05). After treatment with SGK1 inhibitor, SGLT1 mRNA and protein expression were significantly decreased compated to db/db control mice (p<0.05).Conclusion:SGK1 inhibitor treatment significantly decreased hyperglycemia in db/db mice, the possible mechanisms may be partially due to its effect of ameliorating the state of insulin resistance, reducing glucose absorption in small intestine.Part Two SGKl inhibitor reduce glucose absorption by decreasing SGLT1 expression in IEC-6 cellsObjective:To investigate whether the excessive SGK1 expression will stimulate SGLT1 expression and further promote glucose absorption in IEC-6 cells, whether SGKl inhibitors could block this effect. Furthermore,, whether hyperglycemic and hyperinsulinemia could contribute to excessive SGK1 expression and promote glucose absorption in obesity and diabetic state.Methods:IEC-6 cells were incubated with dexamethasone (DXM) and/or SGK1 inhibitor at different time periods, the SGK1 and SGLT1 mRNA and protein expression levels were measured by RT-PCR and western blot.2-NBDG was used as an optical probe for glucose uptake by flow cytometry. IEC-6 cells were further incubated with glucose and insulin at different concentration, the SGKl, SGLT1 and GLUT2 mRNA and protein expression were measured by RT-PCR and western blot.Results:Dexamethasone increased SGKl, SGLT1, GLUT2 mRNA expression in a time-dependent manner in IEC-6 cells. Compared with the dexamethasone group, dexamethasone plus SGK1 inhibitor intervention down-regulated the glucose uptake in the IEC-6 cells, the mRNA expression of SGLT1, GLUT2 were obviously decreased. Glucose or insulin treatment also increased SGKl, SGLT1, GLUT2 mRNA expression in a dose-dependent manner.Conclusion:The excessive SGKl expression stimulated SGLT1 expression, which may promote glucose absorption in IEC-6 cells, SGK1 inhibitors can block this effect. Glucose and insulin also contributed to excessive SGK1 expression in IEC-6 cells and promoted glucose absorption. In a word, SGK1 inhibitor significantly decreased hyperglycemia in db/db mice partially by reducing glucose absorption in intestine.