Citrus Flavanone Naringenin Induces Browning and Brown Adipogenesis: Role of PPARgamma

Abstract Objectives Browning of white adipose tissue and brown adipogenesis induced by PPARg agonists have shown beneficial effects on obesity and associated metabolic disorders. Naringenin, a citrus flavanone, is a promising nutrient for obesity prevention partially through PPARg activation. We previously reported that naringenin significantly enhanced the isoproterenol (ISO)-stimulated thermogenesis by upregulating Ucp1 and Pgc1α in 3T3-L1 cell lines (murine white adipocytes). However, the effects of naringenin on browning and brown adipogenesis and its mechanisms have not been fully explored. We aim to investigate the effects of naringenin on browning and brown adipogenesis and its potential mechanisms in vitro. Methods Murine primary stromal white preadipocytes and murine brown preadipocytes were treated with 10 microM naringenin. PPARg knockdown (PPARg-KD) and scrambled nontargeting control (SCR) in 3T3-L1 cell lines and murine brown preadipocytes were generated and treated with naringenin (10 microM). Oil red o staining was performed to quantify lipid accumulation corresponding to the level of differentiation and the brown adipogenesis. mRNA and protein expression of candidate genes involved in thermogenesis and differentiation were analyzed by qRT-PCR and western blot, respectively. Results In murine primary stromal white adipocytes, naringenin significantly increased Ucp1 mRNA expression at the basal state and significantly enhanced the ISO-stimulated upregulation of Ucp1 and Pgc1α mRNA expression. PPARg-KD significantly blocked the naringenin-induced upregulation of Ucp1 and Pgc1α mRNA. In addition, naringenin significantly promoted the differentiation of brown preadipocytes as determined by oil red o lipid staining. Consistently, protein expression of general differentiation markers including FABP4, HSL, PLIN, and ATGL and thermogenic markers UCP1 and PGC1 α were significantly increased by naringenin, which was significantly attenuated by PPARg knockdown. Conclusions Combined with our previous study showing that naringenin transactivated PPARg using reporter assays, we demonstrated that naringenin induced browning of primary stromal white adipocytes and promoted brown adipogenesis through PPARg activation. Funding Sources The work was supported by funding from NIH.