Roles of Select Cytochrome P450 Epoxygenases in Brown Adipogenesis

Brown adipose tissue (BAT) has recently emerged as a novel target for obesity treatment and prevention. Cytochrome P450 (CYP) epoxygenases, primarily CYP2J and CYP2C isoforms, produce epoxy fatty acids (EpFAs), which have been suggested to play important roles in the regulation of white adipogenesis and obesity. However, adipocyte-specific expression of CYP epoxygenases has not been extensively analyzed, and the roles of CYP epoxygenases in brown adipogenesis remain unexplored. In this study, we examined mRNA levels of Cyp2j and Cyp2c isoforms during murine and human brown and white adipocyte differentiation and in various adipose tissue depots of high-fat diet (HFD)-fed and control mice. Moreover, we began to elucidate the roles of select CYP epoxygenases in brown adipogenesis through modulation of CYP expression. Stable transfection and lentiviral-mediated knockdown of murine Cyp2j13 and stable transfection of human CYP2J2 were performed in brown preadipocytes and their differentiation potentials were compared with cells that were transfected with empty vector or non-targeting knockdown controls. The effects on brown adipogenesis were evaluated by lipid accumulation and expression of brown adipocyte and general differentiation marker genes. We report that mRNA levels of CYP epoxygenases are increased in mature adipocytes compared to preadipocytes but decreased in the most strongly differentiated murine brown adipocytes. Furthermore, Cyp2j mRNA levels displayed an upward trend in the BAT of HFD-fed mice, implicating that Cyp2j expression may be associated with reduced BAT mass and activity. We show that Cyp2j13 overexpression significantly suppressed murine brown adipocyte differentiation, while Cyp2j13 knockdown enhanced differentiation, suggesting that Cyp2j13 may be a negative regulator of brown adipogenesis. In contrast, CYP2J2 overexpression did not remarkably affect human brown adipocyte differentiation. Together, our results suggest that CYP epoxygenases may play important roles in brown adipogenesis. Cyp2j13, in particular, may be a novel target for brown adipogenesis, and consequently, for obesity treatment and prevention. Further studies are warranted to examine the roles of CYP2J2 by gene knockdown and pharmacological antagonism, to determine whether CYP2J2 overexpression may alleviate inflammation-induced suppression of brown adipocyte differentiation and activity, and to analyze roles of other CYP epoxygenase isoforms in brown adipogenesis for obesity treatment and prevention.