FABP1 induces lipogenesis by regulating the processing of SREBP1 in hepatocytes of large yellow croaker (Larimichthys crocea)

Fatty acid‐binding protein 1 (FABP1) plays an important role in regulating fatty acid metabolism in liver, which is a potential therapeutic target for diseases such as non‐alcoholic fatty liver disease (NAFLD). However, the underlying mechanisms are not well defined. Using complementary experimental models, we discovered FABP1 induction in hepatocytes as a primary mediator of lipogenesis when exposed to fatty acids, especially saturated fatty acids (SFAs). In the feeding trial, palm oil led to excess lipid accumulation in the liver of large yellow croaker (Larimichthys crocea), accompanied by significant induction of FABP1. In cultured cells, palmitic acid (PA), a kind of SFA, triggered the fabp1 expression and increased triglyceride (TG) contents. Knockdown of FABP1 dampened PA‐induced TG accumulation through mitigated lipogenesis. The overexpression of FABP1 showed the opposite result. Furthermore, the inactivation of FABP1 led to induction in insulin‐induced gene 1 (INSIG1) expression, which attenuated the processing of sterol regulatory element‐binding protein 1 (SREBP1) by down‐regulating the nuclear‐localized SREBP1. These results revealed a previously unrecognized function of FABP1 in response to PA, providing additional evidence for targeting FABP1 in the treatment of NAFLD caused by SFA. Schematic of the mechanism by which FABP1 regulates lipid metabolism in hepatocytes of large yellow croaker. PA‐induced increase of FABP1 could significantly increase the protein level of N‐SREBP1 by attenuating INSIG1 expression, which further triggered the lipogenic genes expression and ultimately caused lipid accumulation in the liver. These results revealed a conserved and previously unappreciated hepatocyte response to PA mediator. Modulation of FABP1 may be a mechanism to alleviate fatty liver disease such as NAFLD caused by SFA.