Fatostatin inhibits SREBP2-mediated cholesterol uptake via LDLR against selective estrogen receptor α modulator-induced hepatic lipid accumulation.

Estrogen receptor α (ERα) plays a key role in the adaptive response of liver metabolism to energy demands, especially in controlling lipid metabolism. Tamoxifen (TMX), a main drug for the treatment of ER-positive breast cancer in clinical, is a selective ER modulator (SERM). However, accordingly, the long-term use of TMX would lead to nonalcoholic fatty liver (NAFLD) in clinical, which had no definite treatment up to now. Fatostatin (Fato), an inhibitor of sterol-regulatory element binding protein 2 (SREBP2), was reported as a synergistic inhibitor of ER-positive breast cancer with TMX, but the hepatic lipid regulation of this combination is still unknown. Herein, we aimed to explore the effect and mechanism of Fato against TMX-induced NAFLD. The results identified that hepatic cholesterol content increase was the main reason for TMX-induced NAFLD. It was caused by the upregulation of circulating cholesterol uptake mediated by low density lipoprotein receptor (LDLR) in liver, which resulted from the activation of SREBP2. Meanwhile, Fato could inhibit activation of SREBP2-LDLR pathway, alleviating TMX-induced hepatic cholesterol accumulation. In summary, these results provided a new insight into the mechanism of TMX-induced NAFLD. Moreover, it supported the combination of Fato and TMX for the treatment of ER-positive breast cancer to reduce the adverse effect of TMX in clinical.