Chlorogenic acid-enriched extract from Eucommia ulmoides leaves inhibits hepatic lipid accumulation through regulation of cholesterol metabolism in HepG2 cells

Context: Eucommia ulmoides Oliver (Eucommiaceae) leaf exhibits beneficial lipid-lowering and anti-obesity effects. However, the mechanisms remain unknown.Objective: The objective of this study is to investigate the lipid-lowering effects of chlorogenic acid (CGA)-enriched extract from this plant (CAEF) in human hepatoma HepG2 cells, focusing on cholesterol metabolism.Materials and methods: HepG2 cells were treated with CAEF (10, 20, 25, 40, 60, and 80mg/L), CGA (0.3, 3, 30, 300, and 600mol/L), and simvastatin (0.1, 1, 10, 50, and 100mol/L) for 24 or 48h. The cytotoxicity, Oil red O staining, total cholesterol, and triacylglycerol in supernatants were determined. The mRNA expression of genes involved in cholesterol metabolism was determined with RT-PCR. The protein expression of HMG-CoA reductase (HMGCR) was examined by immunocytochemistry and western-blot.Results: The IC50 values were 59.2mg/L for CAEF, 335.9mol/L for CGA, and 10.5mol/L for simvastatin. By treating cells with CAEF (25mg/L), CGA (30mol/L), or simvastatin (10mol/L) for 48h, the efflux of total cholesterol and triacylglycerol was increased (CAEF, 4.06- and 31.00-folds; CGA, 2.94- and 2.17-folds; and simvastatin, 3.94- and 24.67-folds), and the cellular lipid droplets were reduced in Oil red O staining. CAEF and CGA increased mRNA expression of ABCA1, CYP7A1, and AMPK2, while CAEF and simvastatin decreased SREBP2. However, their effects on LXR mRNA expression were variable. Importantly, all drugs significantly inhibited protein expression of HMGCR at mRNA and protein levels.Discussion and conclusion: CAEF is a promising dietary supplement to prevent obesity and dyslipidemia and the effects appear to be due, at least in part, to regulating cholesterol metabolism through inhibition of HMGCR in HepG2 cells.