Study Of Relationship Among Serum Retinol-binding Protein 4 Levels, Type 2 Diabetes And Obesity

ObjectiveTo investigate the change of serum retinol binding protein-4(RBP4) levels and the relationship of serum RBP4 levels to metabolic and clinical biochemical indicators in the subjects with different glucose tolerances and weights, in order to explore the relationship of insulin resistance and RBP4,which was discovered as another adipokine recently,as well as the role of RBP4 in occurrence of T2DM and obesity .MethodsFasting serum retinol binding protein-4 levels were measured by Enzyme-Linked Immuno Sorbent Assay (ELISA) in 13 cases of normal glucose regulation with normal weight (NW-NGR),14 cases of normal glucose regulation with over weight or obesity(OW/OB-NGR),26 cases of type 2 diabetes with normal weight(NW-T2DM) and 34 cases of type 2 diabetes with over weight or obesity(OW/OB-T2DM) . Meanwhile fasting true insulin(FINS) ,fasting blood glucose(FBG),hemoglobin A1C(HBA1C),blood lipid ,blood pressure, height, weight, waistline and hip circumference were measured, and waist to hip ratio(WHR),body mass index(BMI) were also calculated. Using homeostasis model assessment(HOMA-IR) estimated insulin resistance: HOMA-IR=FBG*FINS/22.5. The change of serum RBP4 levels in subjects with different glucose tolerance and weight and the correlation between the serum RBP4 level and these clinical indicators were analyzed by SPSS11.5 software for windows.ResultsSerum RBP4 levels in T2DM was similar with that in NGR[(1.05±0.51)vs(0.95±0.24)μmol / l, P=0.33].However,the serum RBP4 levels in sub-groups were different: OW/OB-T2DM(1.20±0.34)μmol / l >OW/OB-NGR(1.08±0.27)μmol / l >NW- T2DM(0.86±0.06)μmol / l >NW-NGR(0.81±0.07)μmol / l, especially serum RBP4 levels in OW/OB-T2DM and OW/OB-NGR were significantly higher than those in NW-NGR and NW-T2DM(P<0.05 or P<0.01);but there was no difference in serum RBP4 levels between OW/OB-T2DM and OW/OB-NGR , as well as between NW-T2DM and NW-NGR.A correlation analysis showed that the serum RBP4 levels was correlated with sex(r=-0.280,P=0.009),BMI(r=0.455,P<0.001),WHR(r=0.373, P<0.001), TG(r=-0.223, P =0.038),FINS(r=-0.259,P=0.015) and HOMA-IR (r=0.415, P<0.001) respectively. In a multiple stepwise regression analysis,BMI(r2=0.21,P<0.001), sex(r2=0.17,P=0.045)were independent variables of RBP4.ConclusionSerum RBP4 levels significantly increased in subjects with obesity.RBP4 has remarkable correlations with sex, BMI, WHR,TG, FINS and HOMA-IR, but has no significant relation with FBG and HBA1C,these reveal that RBP4 may contribute to the pathogenesis of diseases correlating with insulin resistance such as obesity and T2DM;RBP4 may become another functionary target in preventing T2DM.