Fibroblast growth factor 19 (FGF-19) is a member of a subfamily of FGFs that includes FGF-21 and FGF-23, each member functions as an important regular of nutrient metabolism. The primary source of endocrine FGF-19 is the ileum, bile acids release into the intestine after a meal to induce expression of FGF-19. Circulating FGF-19 plays an important role in maintaining proper bile acid homeostasis. Several pharmacologic studies in hyperglycaemic, obese animal models have shown that FGF-19 can improve metabolic rate and lower serum glucose and hepatic triglyceride and cholesterol levels. Like insulin, FGF-19 functions as postprandial hormone to govern hepatic protein synthesis, glycogen synthesis and gluconeogenesis, but does not stimulate lipogenesis.

This assay is a quantitative sandwich ELISA. The immunoplate is pre-coated with a rabbit polyclonal antibody specific for human FGF-19. Standards and samples are pipetted into the wells and any human FGF-19 present is bound by the immobilized antibody. After washing away any unbound substances, a biotin labelled polyclonal antibody specific for human FGF-19 is added to the wells. After wash step to remove any unbound reagents, streptavidin-HRP conjugate (STP-HRP) is added. After the last wash step, an HRP substrate solution is added and colour develops in proportion to the amount of human FGF-19 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 FGF-19, 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. 

Human FGF-19 (pg/mL)	Absorbance (450 nm)	Blanked Absorbance
0	0.088	0
31.2	0.121	0.033
62.5	0.155	0.067
125	0.225	0.137
250	0.374	0.286
500	0.66	0.572
1000	1.201	1.113
2000	2.136	2.048

 

B. Sensitivity

The lowest level of FGF-19 that can be measured by this assay is 31.2 pg/mL.

 

C. Specificity

The antibodies used in this assay are specific to human FGF-19 and do not cross-react with human Adiponectin, FGF-21, FABP4, LCN2, RBP4 and PAI-1.

 

D. Precision

Intra-assay Precision (Precision within an assay) C.V. <4.5%.

Inter-assay Precision (Precision between assays) C.V. <5.6%.

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