Central obesity represents a major risk for the development of type 2 diabetes and cardiovascular complications. Obesity is often associated with insulin resistance and abnormal production of inflammatory cytokines. Adipose tissue and especially omentum (adipocytes and resident macrophages) release several cytokines. Visfatin corresponds to a protein identified previously as pre-B cell colony-enhancing factor (PBEF), a 52-kilodalton cytokine expressed in lymphocytes. [1] Visfatin exerted insulin-mimetic effects in cultured cells and lowered plasma glucose levels in mice. Mice heterozygous for a targeted mutation in the visfatin gene had modestly higher levels of plasma glucose relative to wild-type littermates. Surprisingly, visfatin binds to and activates the insulin receptor.