Description
Enzyme immunoassay for the quantitative determination retinol-binding protein 4 (RBP4) in human serum and plasma samples. Quality controls are included with the kit. Developed and manufactured in Europe by PromedeusLab.
Summary
Retinol-binding Protein 4 (RBP4) is a member of the lipocalin family and the major transport protein of the hydrophobic molecule retinol, also known as vitamin A, in the circulation (1). RBP4 is elevated in serum and adipose tissue (AT) in obesity-induced insulin resistance and correlates inversely with insulin-stimulated glucose disposal. Serum RBP4 levels correlated inversely with glucose disposal and insulin-mediated suppression of lipolysis, FFA, and EGP (2).
High levels of serum RBP4 are associated with chronic kidney disease (CKD) and urine RBP4 is the most sensitive biomarker of proximal renal tubule function.
Other Names
RBP-4, Plasma retinol-binding protein (PRBP, RBP), UniProtKB# P02753
Principle of Method
The microtiter plate is coated with the antibody specifically binding the Retinol-binding Protein 4. The human serum or plasma is incubated in the plate with the capture antibody.
The specimen is washed out and the specifically bound protein is incubated with biotin-labelled detection antibody. Following another washing step, Streptavidin-HRP conjugate is added into the well. Unbound reagent is then washed out. Horseradish peroxidase (HRP) bound in the complex reacts with the chromogenic substrate (TMB) creating the blue colour. The reaction is stopped by addition of STOP solution (H2SO4).
The absorbance values are measured at 450 nm (optionally 450/630 nm) and are proportional to the concentration of RBP4 in the specimen. The concentration of RBP4 in unknown samples is determined from the calibration curve which is created by plotting the absorbance values against the standard concentration values.
Sample Types
Serum, Plasma
Typical Standard Curve
Assay Range: 3.75 ng/mL - 120 ng/mL
Sensitivity
The limit of detection, defined as a concentration of human RBP4 giving absorbance higher than absorbance of blank + 3 standard deviations, is better than 0.94 ng/mL of sample.
Precision
Intra-Assay
| Test sample | Mean (ng/mL) | SD | CV |
| 1 |
24.5 | 2.8 |
12% |
| 2 |
22.1 |
2.6 |
12% |
Inter-Assay (Run-to-Run)
| Test sample | Mean (ng/mL) | SD | CV |
| 1 |
40.5 |
4.2 |
10% |
| 2 |
35.7 |
1.8 |
5% |
Accuracy
Dilution Linearity:
| Test sample | Dilution |
Measured Concentration (ng/mL) |
Expected Concentration (ng/mL) |
Yield |
| 1 |
22.4 |
- | - | |
| 1 | 2x | 9.1 |
11.2 |
81% |
| 1 | 4x | 4.8 |
5.6 |
85% |
| 1 | 8x | 3.0 |
2.8 |
108% |
| 2 |
23.0 |
- |
- | |
| 2 | 2x | 9.7 |
11.5 |
84% |
| 2 | 4x | 5.1 |
5.8 |
88% |
| 2 | 8x | 3.2 |
2.9 |
110% |
Spiking Recovery:
| Test sample | Spike (ng/mL) |
Measured Concentration (ng/mL) |
Expected Concentration (ng/mL) |
Yield |
| 1 |
- | 19.1 |
- | - |
| 1 | 9.4 |
25.4 |
28.5 |
89% |
| 1 | 4.7 |
22.1 |
23.8 |
93% |
| 1 | 2.3 |
24.4 |
21.4 |
114% |
Storage
The kit must be stored at 2–8 °C. The opened components can be stored for one week at 2–8 °C.
Usage
This assay is for in vitro research use only and is not for use in diagnostic procedures.
Resources
Summary References
- Steinhoff JS, Lass A, Schupp M. Biological Functions of RBP4 and Its Relevance for Human Diseases. Front Physiol. 2021 Mar 11;12:659977. doi: 10.3389/fphys.2021.659977. PMID: 33790810; PMCID: PMC8006376.
- Kilicarslan M, de Weijer BA, Simonyté Sjödin K, Aryal P, Ter Horst KW, Cakir H, Romijn JA, Ackermans MT, Janssen IM, Berends FJ, van de Laar AW, Houdijk AP, Kahn BB, Serlie MJ. RBP4 increases lipolysis in human adipocytes and is associated with increased lipolysis and hepatic insulin resistance in obese women. FASEB J. 2020 May;34(5):6099-6110. doi: 10.1096/fj.201901979RR. Epub 2020 Mar 13. PMID: 32167208; PMCID: PMC7317205.
Ilex Life Sciences LLC is an authorized distributor of PromedeusLab.