Serum level of retinol binding protein 4 in obese individuals with insulin resistance and with type 2 diabetes mellitus treated by metformin
Mária Tajtáková1, Zuzana Semanová1, Gabriela Ivancová2, Jozefína Petrovicová3, Viera Donicová2 & Eva Zemberová4
Objective: To reveal whether there are differences in serum level of retinol binding protein 4 (RBP4) in obese individuals with insulin resistance (IR) and without diabetes in comparison to those with 2 type diabetes mellitus (2 DM) treated by metformin and not obese controls.
Methodology: The serum level of retinol binding protein 4 was examined by RIA method in 28 obese individuals with insulin resistance, 11 patients with 2 type diabetes mellitus treated by metformin and 17 controls. The results were compared within groups. RBP4 in the group with IR and in controls was correlated with insulin.
Results: The highest level of RBP4 (561.6±209 ng/ml) was found in obese individuals with IR (IRHOMA 3.9) and the lowest level in patients with 2 DM treated by metformin (391.1±133.5 ng/ml, P<0.01). The controls had significantly lower level of RBP4 in comparison to obese individuals with IR (452.8±104.6 ng/ml P<0.05), however, RBP4 was not significantly higher in comparison to obese individuals with 2 DM treated by metformin (391.1±133.5 ng/ml). RBP4 correlated with insulin (r=0.46, P<0.03).
Conclusions: The increase of RBP4 in obese individuals through a back regulation GLUT4 in adipocytes contributes to the development and worsening of IR. Thus, metformin by influencing the expression of RBP4 in adipocytes can improve the overall insulin sensitivity in obese individuals (also with MS) and slower the manifestation of 2 DM. RBP4 could be considered as a marker of the worsening tolerance of glocose in obese individuals.