ObjectiveTo observe expre with ssions of insulin receptor substrate 1(IRS-1) and ubiquitin-protein in skeletal muscle of non-obese rats with type 2 diabetes mellitus following gastric bypass operation (GBP), and to investigate possible mechanism of GBP in improving insulin resistance. MethodsMale GK rats were randomly divided into diabetic operation group (DO group), diabetic sham operation group (DSO group), and diabetic control group (DC group), 8 rats in each group; besides 8 male Wistar rats were served as normal control group (NC group). Fasting body weight (FBW), fasting plasma glucose (FPG), and fasting insulin (FINS) were measured respectively before operation and on week 1, 2, 4 and 8 after operation. Homeostasis model-insulin resistant (HOMA-IR) index was calculated respectively before operation and on week 8 after operation. The expressions of IRS-1 protein and ubiquitin-protein in skeletal muscle were detected by using Western blot method on week 8 after operation. Results① Compared with the preoperative levels, the FBWs on week 1, 2, and 4 after operation markedly decreased (P < 0.05), but it recovered to the preoperative level on week 8 after operation (P > 0.05) in the DO group; which in the DSO group decreased on week 1 after operation (P < 0.05) and then increased on week 4 after operation (P < 0.05); which in the DC group or the NC group increased continuously and had a significant difference on week 8 after operation (P < 0.05).② The FPGs in the DO, DSO and DC groups were significantly higher than those of the NC group before operation (P < 0.05), which in the DO group decreased from (9.10±0.98) mmoL/L before operation to (5.70±0.91) mmol/L on week 8 after operation (P < 0.05) and were significantly lower than those of the DSO group or the DC group on week 2, 4, and 8 after operation (P < 0.05); which in the DC group, DSO group and NC group had no obviously changes between before and after operations (P > 0.05). ③ The FINS had no significant differences among these four groups before operation (P > 0.05), which in the DO group obviously increased[(9.64±1.59) mU/L] on week 2 after operation (P < 0.05) and then obviously decreased[(6.58±1.05) mU/L] on week 8 after operation (P < 0.05) and significantly lower than those of the DSO group or the DC group on week 8 after operation (P < 0.05), while which had no significant difference between before and after operations in the DSO group, the DC group, or the NC group (P > 0.05). ④ The HOMA-IR index in the DO, DSO or DC group was significantly higher than that of the NC group before operation (P < 0.05), which in the DO group markedly decreased from 3.18±0.50 before operation to 1.96±0.63 on week 8 after operation (P < 0.05) and significantly lower than that of the DSO group or the DC group on week 8 after operation (P < 0.05), while which had no significant difference between before and after operations in the DSO group, the DC group, or the NC group (P > 0.05). ⑤ The expression of IRS-1 protein in the DO group was significantly higher than that in the DSO group (P < 0.05) or the DC group (P < 0.05) on week 8 after operation. While there was no significant difference between the DSO and the DC group after operation (P > 0.05). ⑥ Compared with the NC group, the expression of ubiquitin-protein was significantly increased in the DO group, the DSO group, or the DC group (P < 0.05). Compared with the DSO group or the DC group, the expression of ubiquitin-protein was significantly decreased in the DO group on week 8 after operation (P < 0.05), especially it was most obvious near the molecular weight of 180×103. While there was no significant difference between the DSO group and the DC group after operation (P > 0.05). ConclusionsExpression of IRS-1 protein in skeletal muscle insulin signaling pathway in type 2 diabetes mellitus rats following GBP is increased, it might be associated with decreasing ubiquitin-protein level in skeletal muscle, thus reduces the IRS-1 ubiquitin-degradation, increase insulin sensitivity, and improve insulin resistance of skeletal muscle.
ObjectiveTo investigate the expressions of glucose transporter-4 (GLUT-4) and secreted protein acidic and rich in cysteine (SPARC) in adipose tissue of Goto-Kakizaki (GK)/Wister rats after gastric bypass operation (GBP), and to explore the possible mechanism of GBP improving insulin resistance.MethodsHealthy male GK rats were randomly divided into diabetic operation group (DO group, underwent GBP), diabetic sham operation group (DS group, underwent sham-operation), and diabetic control group (DC group, received no-treatment), Wister rats were set as normal control group (NC group, received no-treatment). The weight, fasting blood glucose (FPG), fasting serum insulin (Fins), and HbA1c were measured before operation and at the 1st, 2nd, 4th, and 8th week after operation. Quantitative insulin sensitivity check index (QUICKI) was measured in before operation and at the 8th week after operation, and the expressions of GLUT-4 and SPARC protein in adipose tissues were measured by Western Blot method at the 8th week after operative too.Results① Weight: the weight of the DO group was lower than preoperative at the 2nd and 4th week after GBP (P<0.05), but increased to the normal level at the 8th week after GBP (P>0.05). The weight of the DO group was lower than those of the DS group, DC group, and NC group at the same time point of 2nd, 4th, and 8th week (P<0.05). ② FPG: the FPG level of the DO group was lower than preoperative at the 2nd, 4th, and 8th week after GBP (P<0.05), and lower than those of the DS group and the DC group from 2nd to 8th week after GBP (P<0.05). The FPG level between the DS group and the DC group had no statistical significance (P>0.05). ③ Fins: the Fins level of the DO group was higher than preoperative at the 2nd week after GBP (P<0.05), and decreased gradually at 4th and 8th week but not significantly differed from the NC group at the same time point. At the 2nd week after GBP, the Fins level of the DO group was higher than those of the DS group and the DC group (P<0.05), but there was no statistical significance between the DS group and the DC group (P>0.05). ④ HbA1c: the HbA1c level of the DO group started to decrease but there was no statistical significance between preoperative and all time after GBP (P>0.05). There was no statistical significance among the 4 groups at the 8th week after GBP (P>0.05). ⑤ QUICKI: at the 8th week, the QUICKI value of the DO group was higher than preoperative (P<0.05), and at the same time, the QUICKI value of the DO group and the NC group were higher than those of the DS group and the DC group (P<0.05), but there was no statistical significance between the DO group and the NC group (P>0.05), as well as the DS group and the DC group (P>0.05). ⑥ GLUT-4 protein and SPARC protein: the expression of GLUT-4 protein of the DO group was dramatically higher than those of the DC, DS, and NC group (P<0.05), and the expression of SPARC protein of the DO group was dramatically lower than those of the DC, DS, and NC group (P<0.05) at the 8th week. But the expressions of GLUT-4 and SPARC protein had no statistical significance among the DS, DC, and NC group at the 8th week after GBP (P>0.05).ConclusionGBP may improve and increase the sensitivity of insulin resistance by regulating the expressions of GLUT-4 and SPARC protein in adipose tissue of GK rats.