Ixeris dentata (Thunb) Nakai Ethylacetate Extract Attenuates Sterol Regulatory Element-Binding Proteins-1c via AMP-Activated Protein Kinase Activation
Abstract
Purpose: To investigate the molecular mechanisms underlying the role of Ixeris dentataa extract (IDE) in the prevention of high glucose induced lipid accumulation in human HepG-2 hepatocytes.
Methods: IDE extract was prepared by maceration in ethyl acetate. Its fractionation was carried out by column chromatography. HepG-2 cells were pretreated with various concentration of IDE (0, 10, 20, 40 and 80 μg/mL) and then treated with serum-free medium with normal glucose (5 mM) for 1 h, followed by exposure to high glucose (30 mM D-glucose) for 24 h. Cell viability and cytotoxicity parameters were measured using lactate dehydrogenase (LDH) and MTT assay while triglyceride and total cholesterol levels were evaluated using respective enzymatic reagent kits. Protein expressional levels were analyzed by Western blotting.
Results: IDE did not influence the cell viability (up to 200 μg/mL) and did not show any signs of cytotoxicity (up to 80 μg/mlL. IDE significantly attenuated lipid accumulation in human HepG2 hepatocytes when exposed to high glucose (30 mM D-glucose) in a dose-dependent manner (p < 0.05, 0.01 and 0.001 at 20, 40 and 80 μg/mL concentrations, respectively). Nile red staining showed that 10, 20, 40 and 80 μg/mL concentrations of IDE reduced lipid accumulation by 23.4, 34.8 (p < 0.05), 46.5 (p < 0.01) and 53.2 % (p < 0.001), respectively. The increased levels of triglycerides and total cholesterol were also attenuated by IDE (p < 0.001 at 80 μg/mL). Further, IDE attenuated the expression of fatty acid synthase and sterol regulatory element-binding protein-1. Adenosine monophosphate-activated protein kinase was also activated by IDE treatment when exposed to high glucose level (30 mM Dglucose) in human HepG2 hepatocytes.
Conclusion: The findings indicate that IDE exerts hypolipidemic effect by inhibiting lipid biosynthesis, mediated via AMPK signaling. This probably explains the extract’s beneficial effect in various inflammation disorders.
Keywords: Ixeris dentata extract, Lipogenesis, AMP-activated protein kinase, Sterol regulatory element-binding protein 1 -1, Anti-obesity, HepG-2 cell
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