Resistin was identified by screening for genes that are induced during the differentiation of adipocytes but down-regulated in mature adipocytes. Resistin gene expression is induced during the differentiation of adipocytes. Resistin circulates in mouse serum, and its level is increased markedly in obesity. Adipocytes secrete resistin as a unique signaling molecule that may be the hormone potentially linking obesity to type II diabetes, which is characterized by target-tissue resistance to insulin. TNF-alpha is a negative regulator of Resistin gene expression and inhibits Resistin mRNA expression and protein secretion by 70-90% in 3T3-L1 adipocytes.