Human Retinol Binding Protein 4 (RBP4) ELISA Kit
Retinol binding protein 4(RBP4), originally known as a specific transport of retinol in blood, is also a novel inflammatory and insulin resistance marker. Serum RBP4 levels are elevated in insulin-resistant mice and humans with obesity and type 2 diabetes. Animal experiments found that increased secretion of RBP4 might reduces insulin-dependent glucose uptake by muscle tissue by reducing the activity of PI(3)K (phosphoinositide 3-kinase), and increased hepatic glucose output by increasing the expression of the enzyme PEPCK2 . Studies suggested that elevated serum RBP4 was associated with components of the metabolic syndrome, including increased body-mass index, waist-to-hip ratio, serum triglyceride levels, and systolic blood pressure and decreased highdensity lipoprotein cholesterol levels4 . Furthermore, circulating RBP4 concentrations were associated with subclinical cardiovascular disease, which imply that RBP4 could be involved in the development of atherosclerosis5 .
PRINCIPLE OF THE ASSAY
This assay is a quantitative sandwich ELISA using monoclonal antibodies against human RBP4. The immunoplate is pre-coated with a monoclonal antibody specific for human RBP4 and the nonspecific binding sites are blocked. Standards and samples are pipetted into the wells and any Human RBP4 present is bound by the immobilized antibody. After washing away any unbound substances, a horseradish peroxidase (HRP)-linked monoclonal antibody specific for human RBP4 is added to the wells. After wash step to remove any unbound reagents, an HRP substrate solution is added and colour develops in proportion to the amount of human RBP4 bound initially. The assay is stopped and the optical density of the wells determined using a microplate reader. Since the increases in absorbance are directly proportional to the amount of captured human RBP4, the unknown sample concentration can be interpolated from a reference curve included in each assay.
A. Typical representation of standard curve
The following standard curve is provided for demonstration only. A standard curve should be generated for each set of sample assay.
Absorbance (450 nm)
The lowest level of RBP4 that can be detected by this assay is 1.56 ng/ml.
The antibody pair used in this assay is specific to human RBP4 and does not cross-react with mouse and rat RBP4, and other cytokine or hormone molecules.
Intra-assay Precision (Precision within an assay)
Three samples of known concentration were tested 16 times on one plate.
Inter-assay Precision (Precision between assays)
Three samples of known concentration were tested in 10 separate assays.
Serum samples were spiked with different amounts of human RBP4 and assayed.