URB is abundantly expressed in adipose tissue and dysregulated in obesity.

Dysregulated production of adipocytokines in obesity is involved in the development of metabolic syndrome. URB/DRO1 contains N-terminal signal sequence and is thought to play a role in apoptosis of tumor cells. In the present study, we investigated the expression pattern of URB mRNA in adipose tissue and secretion from cultured adipocytes. In human and mouse, URB mRNA was predominantly expressed in adipose tissue and was downregulated in obese mouse models, such as ob/ob, KKAy, and diet-induced obese mice. In 3T3L1 adipocytes, insulin, TNF-α, H2O2 and hypoxia decreased URB mRNA level. This regulation was similar to that for adiponectin and opposite to MCP-1. URB protein was secreted in media of URB cDNA-stably transfected cells and endogenous URB was detected in media of cultured human adipocytes. In conclusion, the expression pattern of URB suggests its role in obesity and the results suggest that URB is secreted, at least in part, from adipocytes.