RBP4 has a known function as a transporter of Vitamin A in the body. These investigators found that high levels of the protein can also cause cells to be more resistant to insulin - a condition that precedes diabetes.
This knowledge may lead to the development of drugs that can lower levels of this protein, adding to the arsenal of diabetes' therapies.
For a summary of the study:
Study identifies fat-secreted protein linked to insulin resistance
For the study itself:
Serum retinol binding protein 4 contributes to insulin resistance in obesity and type 2 diabetes