[Correlation of retinol binding protein 4 expression in maternal serum and subcutaneous adipose tissue with insulin resistance in gestational diabetes mellitus.].

Objective: To investigate the expression of retinol binding protein 4 (RBP-4) in maternal serum and subcutaneous adipose tissue and its relationship with insulin resistance (IR) in gestational diabetes mellitus (GDM).

Methods: From May 2008 to April 2009, 62 pregnant women who underwent elective cesarean section in the Department of Obstetrics, Affiliated Hospital of Qingdao University Medical College, were recruited, including 32 with GDM (GDM group) and 30 with normal glucose tolerance test (control group). Enzyme-linked immunosorbent assay (ELISA) was used to determine the serum concentrations of RBP-4 and radio immunoassay to measure the serum levels of fasting insulin (FINS). Fasting plasma glucose (FPG) was tested by glucose oxidase, and the Home model insulin resistance index (HOMA-IR) was calculated. Reverse transcription PCR (RT-PCR) and Western blot were applied to investigate the expression of RBP-4 mRNA and protein in subcutaneous adipose tissue. The correlations between the expression of RBP-4 mRNA and protein in subcutaneous adipose tissue and the serum RBP-4 concentrations and HOMA-IR were analyzed.

Results: (1) The serum concentrations of RBP-4, FINS, FPG, HOMA-IR in GDM group were significantly higher compared with the control group [(27.0 +/- 1.2) mg/L vs. (19.4 +/- 1.8) mg/L, (12.1 +/- 1.4) mU/L vs. (8.3 +/- 0.8) mU/L, (5.3 +/- 0.9) mmol/L vs. (4.1 +/- 0.6) mmol/L, 2.5 +/- 0.2 vs. 1.5 +/- 0.1, P < 0.05, respectively]. (2) The expression of RBP-4 mRNA and protein in subcutaneous adipose tissue in the GDM group were significantly higher than that of the control group (0.76 +/- 0.12 vs. 0.53 +/- 0.06, 0.74 +/- 0.09 vs 0.54 +/- 0.06, P < 0.05). (3) In the GDM group, the expression of both RBP-4 mRNA and protein in the subcutaneous adipose tissue were positively correlated with HOMA-IR (r = 0.575 and 0.851, P < 0.05). The serum concentration of RBP-4 were also positively correlated with HOMA-I (r = 0.635, P < 0.05). No correlations was found between the expressions of RBP-4 mRNA and protein in subcutaneous adipose tissue with the serume RBP-4 concentrations.

Conclusion: High expression of RBP-4 mRNA in subcutaneous adipose tissue and the elevation of serum RBP-4 levels in GDM women may contribute to IR.