Visfatin (NAMPT) Human ELISA

Visfatin, also known as pre-B-cell colony-enhancing factor and Nicotinamide Phosphoribosyltransferase (Nampt) is a polypeptide of 491 amino acids with a molecular mass of 52 kDa. It has recently been identified as a novel adipokine expressed in adipocytes and secreted from adipose tissue, especially from visceral fat. Visfatin was also found to be expressed in other tissues including leukocytes, skeletal muscle, liver and kidney. The expression of visfatin is upregulated in a glucose-dependent manner and is increased by an intravenous glucose tolerance test.

Visfatin was also found to act as a key enzyme in the process of nicotinamide adenine dinucleotide biosynthetic activity, which could play a major role in maintaining β-cell function in obese subjects and those with type 2 diabetes mellitus. Incubation with visfatin in clonal mouse pancreatic β cells increased insulin upregulation by ninefold and caused a 46% increase in insulin secretion as compared with a low glucose environment. In addition, acute injections of visfatin into KKAy mice in an obese type 2 diabetic model significantly reduced plasma glucose. One study reported that acute administration of visfatin was able to prevent cardiomyocyte death at the onset of myocardial reperfusion while other reports have suggested that chronic visfatin expression exerts an atherogenic effect. Chronic treatment with visfatin may induce leukocyte adhesion to endothelial cells and the aortic endothelium by induction of the cell adhesion molecules ICAM-1 and VCAM-1, suggesting that visfatin is a vascular inflammatory mediator. In addition, other studies have shown high levels of visfatin in atherogenic plaques obtained from patients with acute myocardial infarction. Visfatin can activate matrixmetalloproteinase 2/9 expression in human endothelial cells, implying a pathway of atherogenic plaque instability. Visfatin has been also shown to elicit pro-inflammatory signals in human aortic smooth muscle cells. These reports suggest a complex interaction between visfatin and inflammatory atherosclerotic diseases. Plasma visfatin has been reported to be elevated in patients with type 2 diabetes mellitus, overweight/obesity problems and in subjects with metabolic syndrome. Furthermore, circulating visfatin levels were found to be positively associated with insulin resistance, and is elevated in patients with cardiovascular diseases.