CREG1 promotes uncoupling protein 1 expression and brown adipogenesis in vitro.

Brown adipocytes play a critical role for adaptive thermogenesis to regulate body temperature in cold or to circumvent diet-induced obesity. In this study, we investigated the role of cellular repressor of E1A-stimulated genes 1 (CREG1) on brown adipogenesis and uncoupling protein 1 (UCP1) expression by using in vitro culture models. In murine mesenchymal stem cell line C3H10T1/2, Creg1 mRNA expression significantly increased in a time-dependent manner along with Ucp1 mRNA induction in brown adipogenesis. Creg1 gene overexpression upregulated the expression of brown fat-related genes including Ucp1 but its suppression downregulated these gene expression in C3H10T1/2 cells. Unlike the brown adipogenesis, Creg1 mRNA expression decreased significantly after differentiation stimulation in white adipogenesis of 3T3-L1 cells. Either Creg1 gene overexpression or suppression hardly affected white adipogenesis. In addition, CREG1 protein stimulated brown adipogenesis and rescued the adipogenesis in the absence of thyroid hormone in C3H10T1/2 cells. In reporter assay, CREG1 induction stimulated Ucp1 promoter activity, which was enhanced by co-expression with thyroid hormone receptors. The effect of CREG1 on Ucp1 promoter activity was also stimulated by retinoic acid. These results strongly suggest that CREG1 plays an important role on the regulation of UCP1 expression and brown adipogenesis.