ObjectiveTo observe expressions of E3 ubiquitin ligase—mitsugmin53 (MG53) protein, MG53 mRNA, and insulin receptor substrate 1 (IRS-1) mRNA in skeletal muscle of non-obese type 2 diabetic mellitus (T2DM) rats after gastric bypass operation (GBP), and to investigate possible mechanism of GBP in improving insulin resistance.MethodsTwenty-four healthy male GK rats were randomly divided into diabetic operation group, diabetic sham operation group, and diabetic control group, 8 rats in each group; besides, 8 male Wistar rats were served as normal control group. The expressions of MG53 protein in skeletal muscle tissue were detected by using Western blot method on week8 after operation. The mRNA levels of IRS-1 and MG53 in skeletal muscles tissue were measured by RT-PCR methods on week 8 after operation.Results① The expressions of MG53 protein and MG53 mRNA in the diabetic sham operation group and diabetic control group were significantly higher than those in the diabetic operation group and the normal control group on week 8 after operation (P<0.05), respectively, which had no significant differences between the diabetic operation group and the normal control group (P>0.05), and between the diabetic sham operation group and the diabetic control group (P>0.05) on week 8 after surgery. ② Compared with the normal control group, the expression of IRS-1 mRNA was significantly decreased in the diabetic operation group, the diabetic sham operation group, and the diabetic control group (P<0.05), while there were no significant differences between the diabetic operation group, diabetic sham operation group, and the diabetic control group on week 8 after operation (P>0.05).ConclusionExpression of E3 ubiquitin ligase—MG53 protein in skeletal muscle tissue in T2DM rats following GBP is decreased, thus reduces the IRS-1 ubiquitin-degradation, increase the expression of IRS-1 protein in insulin signaling pathway of skeletal muscle tissue, and improve insulin resistance of skeletal muscle.