Nrf2 induces fibroblast growth factor 21 in diabetic mice

Transcription factor Nrf2 (nuclear factor E2-related factor 2) is a master regulator of cellular defense system against oxidative and electrophilic stresses and is negatively regulated by an adaptor protein Keap1 (Kelch-like ECH-associated protein 1). Nrf2 also plays a pivotal role in metabolic homeostasis, such as lipid metabolism and energy expenditure as well as redox homeostasis. FGF21 (fibroblast growth factor 21) is known as a key mediator of glucose and lipid metabolism. Here, we found that Nrf2 is involved in FGF21 regulation in diabetic model mice. Nrf2 induction by genetic knockdown of Keap1 increased plasma FGF21 level and hepatic Fgf21 expression in diabetic db/db mice and high-calorie-diet-induced obesity model mice. Administration of CDDO-Im (oleanolic triterpenoid 1-[2-cyano-3,12-dioxooleane-1, 9(11)-dien-28-oyl] imidazole), a potent Nrf2 inducer, up-regulated plasma FGF21 level and hepatic Fgf21 expression in db/db mice, whereas CDDO-Im did not induce FGF21 in db/db mice with Nrf2 knockout background. Furthermore, in Keap1-knockdown db/db mice, Nrf2 enhanced expression of glucose- and lipid-metabolism-related genes in adipose tissues, which improved plasma lipid profiles. These results show that Nrf2 positively regulates FGF21 expression in diabetic mice. We propose that FGF21 is a potential efficacy biomarker that mediates metabolic regulation by the Keap1-Nrf2 system.