NR0B1 and Arthritis: PPARγ is a member of the nuclear hormone receptor superfamily that is capable of both positive and negative regulation of gene expression in ligand-dependent and -independent manners.31, 32 PPARγ has been suggested to be involved in a series of cellular functions, including adipocyte differentiation, inflammatory responses, and apoptosis;31 however, there are few reports on the function of PPARγ in the pathogenesis of arthritis.