Relationship between tyrosine phosphorylation and protein expression of insulin receptor and insulin resistance in gestational diabetes mellitus

The relationship between tyrosine phosphorylation (TP) and protein expression of insulin receptor (InsR) and insulin resistance (IR) in patients with gestational diabetes mellitus (GDM) was investigated. The InsR expression and TP in skeleton muscle tissue were determined by Western blotting and immunoprecipitation in women with GDM (GDM group, n=22), normal pregnant women (normal pregnancy group, n=22) and normal non-pregnant women (normal non-pregnant group, n=13). Fasting plasma glucose (FPG) and fasting insulin (FINS) were measured by oxidase assay and immunoradioassay. The results showed that the levels of FPG (5.61 +/- 0.78 mmol/L), FINS (15.42 +/- 5.13 mU/L) and Homeostasis model assessment-IR (HOMA-IR) (1.21 +/- 0.52) in GDM group were significantly higher than those in normal pregnancy group (4.43 +/- 0.46 mmol/L, 10.56 +/- 3.07 mU/L and 0.80 +/- 0.31 respectively) (P < 0.01). The levels of FINS and HOMA-IR in normal pregnancy group were significantly higher than those in normal non-pregnant group (7.56 +/- 2.31 mU/L and 0.47 +/- 0.26 respectively) (P < 0.01). There was no significant difference in the InsR expression level among the three groups (P > 0.05). TP of InsR with insulin stimulation was significantly decreased in GDM group (0.20 +/- 0.05) as compared with normal pregnancy group (0.26 +/- 0.06) (P < 0.01). TP of InsR with insulin stimulation in normal pregnancy group was lower than that in normal non-pregnant group (0.31 +/- 0.06) (P < 0.01). TP of InsR with insulin stimulation was negatively related with HOMA-IR in GDM group (r=-0.525, P < 0.01). There was no correlation between the protein expression of InsR and HOMA-IR in GDM group (r=-0.236, P > 0.05). It was suggested that there is no significant correlation between the protein expression of InsR in skeletal muscle and IR in GDM, but changes in TP of InsR are associated with IR in GDM.