Curcumin protects against high-fat diet-induced nonalcoholic simple fatty liver by inhibiting intestinal and hepatic NPC1L1 expression via down-regulation of SREBP-2/HNF1α pathway in hamsters

Abstract

Niemann-pick C1-like 1 (NPC1L1) mediates cholesterol absorption and plays a key role in the pathogenesis of nonalcoholic simple fatty liver (NASFL). Our previous study showed that curcumin reduced NPC1L1 expression and cholesterol absorption in Caco-2 cells. This study aimed to investigate whether curcumin could inhibit intestinal and hepatic NPC1L1 expression through suppressing sterol regulatory element binding protein-2 (SREBP-2) / hepatocyte nuclear factor 1α (HNF1α) pathway, then exert anti-NASFL effects. Six-week hamsters were fed high-fat diet (HFD) with or without 0.1% curcumin for 12 weeks. Curcumin supplementation lowered blood total cholesterol (TC), triglycerides (TG) and low-density lipoprotein cholesterol levels (20.2%, 48.7%, and 36.5%), and reduced liver TC and TG contents (26.1% and 26.5%). Oil Red O staining demonstrated that curcumin significantly alleviated HFD-induced liver fat accumulation and hepatic steatosis, which was accompanied by reduced intestinal and hepatic NPC1L1, SREBP-2 and HNF1α expression (P < .05) and increased fecal neutral sterol excretion (114.5%). Furthermore, curcumin decreased cholesterol absorption in Caco-2 cells and HepG2 cells (49.2 % and 52.7 %). The inhibitory effects of curcumin on NPC1L1 expression and cholesterol absorption could be prevented by blockade of the SREBP-2 and HNF1α pathway. These findings indicated that curcumin protected against HFD-induced NASFL by inhibiting intestinal and hepatic NPC1L1 expression via down-regulation of SREBP-2/HNF1α pathway, thus reducing intestinal cholesterol absorption and hepatic biliary cholesterol reabsorption, consequently alleviating liver cholesterol accumulation and steatosis. Our study provides evidence for curcumin as a potential nutritional therapy for NASFL by regulating NPC1L1 and enterohepatic circulation of cholesterol.

Keywords: Curcumin; Hepatocyte nuclear factor 1α; Niemann-Pick type C1-like 1; Nonalcoholic simple fatty liver disease; Sterol regulatory element binding protein-2.