Visfatin, also known as a pre-B cell colony-enhancing factor, is a 55 kD protein of the NAPRTase family of molecules. It functions both intracellularly and extracellularly, where it participates in NAD synthesis and insulin receptor activation, respectively. This protein is produced and secreted primarily by white adipose tissue. It is also expressed by neurons within the arcuate nucleus of the hypothalamus, a brain area that plays a pivotal role in the regulation of energy metabolism. Although the metabolic function of Visfatin is still unknown, it appears that this adipocytokine might play an important role in the regulation of body weight as an afferent signal reflecting excess body fat. Importantly, Visfatin binds the insulin receptor at a site distinct from that of insulin and causes hypoglycemia by reducing glucose release from liver cells and stimulating glucose utilization in adipocytes and myocytes. Other major functions of Visfatin include enhancing phagocytosis, inducing production of CCL2 and IL-6 in umbilical cord endothelial cells, and upregulating the expression of VEGF. The expression of Visfatin is upregulated by hypoxia, inflammation and hyperglycemia and downregulated by insulin, somatostatin and statins.