Visfatin, an adipocytokine that is highly enriched in the visceral fat of both humans and mice and whose expression level in plasma increases during the development of obesity. Visfatin corresponds to pre-B cell colony-enhancing factor (PBEF), a 52-kD cytokine expressed in lymphocytes. PBEF is an inflammatory cytokine that plays a requisite role in the delayed neutrophil apoptosis of sepsis. Visfatin exerted insulin-mimetic effects in cultured cells and lowered plasma glucose levels in mice. It was found that visfatin binds to and activates the insulin receptor. Plasma level of visfatin in patients with type 2 diabetes mellitus was elevated, suggesting that measurement of plasma visfatin provides a relevant tool for understanding metabolic diseases.