FABP-4, also termed adipocyte fatty-acid binding protein (A-FABP) or AP2, has been shown to play a key role in obesity and metabolic syndrome. A-FABP knockout mice are substantially protected from insulin resistance, dyslipidemia, type 2 diabetes and fatty liver disease, despite of increased adipocity.
In clinical studies, increased circulating A-FABP levels are found in obese subjects and associated with non-alcoholic fatty liver disease, stroke, and carotid atherosclerosis.
 

This assay is a quantitative sandwich ELISA. The immunoplate is pre-coated with a mouse monoclonal antibody specific for human FABP4. Standards and samples are pipetted into the wells and any Human FABP4 present is bound by the immobilized antibody. After washing away any unbound substances, a biotin labelled polyclonal antibody specific for human FABP4 is added to the wells. After wash step to remove any unbound reagents, streptavidin-HRP conjugate is added, after the last wash step, an HRP substrate solution is added and colour develops in proportion to the amount of human FABP4 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 FABP4, 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. 

FABP4 (ng/mL)	Absorbance (450 nm)	Blanked Absorbance
0	0.1	0
0.39	0.158	0.058
0.78	0.228	0.118
1.56	0.332	0.232
3.12	0.554	0.454
6.25	0.957	0.857
12.5	1.547	1.447
25	2.289	2.189

 

B. Sensitivity

The lowest level of FABP4 that can be detected by this assay is 0.39 ng/mL.

 

C. Specificity

The antibodies used in this assay are specific to human FABP4 and do not cross-react with mouse and rat FABP4, and other cytokine or hormone molecules.

 

D. Precision

Intra-assay Precision (Precision within an assay) C.V. <4.1%.

Inter-assay Precision (Precision between assays) C.V. <4.5%.

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