Retinol binding Protein (RBP4) ELISA

Retinol-binding protein (RBP)/RBP4 is a small (21kD) transport protein for vitamin
A which forms a complex with prealbumin in blood, but loses its affinity for prealbumin
once the vitamin has been delivered to the target cells. The free RBP/RBP4
molecule is rapidly filtered at the glomerulus and catabolised in the renal tubules
after resorption by the proximal tubular cells (like other small molecules, e.g. ß-2
microglobulin). In kidney disease with prevailing tubular changes, these proteins are
not reabsorbed and appear in the urine.
As published by Yang et al. (2005), the retinol-binding protein (RBP)/RBP4 seems to
play a key role in the development of insulin resistance. The fat cell derived peptide
RBP/RBP4 also modulates the glucose homeostasis and impairs the insulin sensitivity
as well as insulin resistance. The elevation of serum RBP/RBP4 causes systemic insulin
resistance, whereas its reduction improves the insulin action.
As a conclusion from the results, the authors suggest that RBP/RBP4 alters insulin
sensitivity in part by affecting insulin signalling in muscle through alterations in the
amount of tyrosine-phosphorylated IRS-1 and PI(3)K activation. Thus, RBP/RBP4 may
contribute to the pathogenesis of type 2 diabetes, and lowering RBP/RBP4 could be
a new strategy for treating type 2 diabetes.