Garcinia Biflavonoid 1 Improves Lipid Metabolism in HepG2 Cells via Regulating PPARα

Figures

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  Figure 1. GB1 improves lipid deposition in liver cells. HepG2 cells were exposed to OA (500 µM) and PA (250 µM) for 24 h, and were then subjected to Wy14643 (PPARα agonist) and GB1 (25 µM, 50 µM) for 24 h. (A) HepG2 cell activity under different concentrations of GB1. (B) HepG2 cell activity under different concentrations of OA&PA. (C) HepG2 cell activity under 50 µM GB1 and different concentrations of OA&PA. (D) Triglycerides level in HepG2 cells under different conditions. (E) Representative Oil-Red-O stained images (400×). (F) Chemical structure of GB1. All data were presented as mean ± SEM of three independent experiments. **, p < 0.01, ***, p < 0.001; ns, not significant.

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  Figure 2. GB1 positively regulates lipid metabolism. (A) Western blot and (B) immunofluorescence staining assays revealed upregulation of the protein levels of PPARα and SIRT6 in HepG2 cells undergoing OA&PA culture after GB1 treatment. (C) Changes in mRNA levels of PPARα and SIRT6 after GB1 treatment. GB1 advanced lipid oxidization (D) and reduced the level of free fatty acids (E) in liver cells (200×). All data were presented as mean ± SEM of three independent experiments. *, p < 0.05, **, p < 0.01.

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  Figure 3. GB1 improves the ROS burden induced by OA&PA in HepG2 cells. (A) Flow cytometry showed the suppression of ROS level by GB1 treatment. (B) GB1 reduced the production of MDA, ALT (C) and AST (D). (E) GB1 suppressed apoptosis-related genes. All data were presented as mean ± SEM of three independent experiments. *, p < 0.05, **, p < 0.01, ***, p < 0.001, ****, p < 0.001; ns, not significant.

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  Figure 4. GB1 decreases the cell apoptosis induced by OA&PA. (A) Flow cytometry was performed to analyze cell apoptosis after treatment with GB1. (B) GB1 inhibited the expression of apoptosis-related genes. (C) Representative images for MMP after GB1 treatment (200×). (D) Representative images for TUNEL-labeled cells that underwent apoptosis (200×). (E) GB1 treatment elevated the expression of anti-apoptotic proteins. All data were presented as mean ± SEM of three independent experiments. *, p < 0.05, **, p < 0.01, ***, p < 0.001, ****, p < 0.001; ns, not significant.

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  Figure 5. GB1 fails to improve the lipid deposition in PPARα-deficient cells. PPARα silenced by siRNA as demonstrated by Western blot (A) and RT-qPCR (C). (B) Level of triglycerides (TGs) in PPARα-deficient cells after treatment with GB1. (D) Representative image of lipid deposition in PPARα-deficient cells after treatment with GB1. (E) Levels of relevant genes in PPARα-deficient cells after treatment with GB1. No significant alterations in the levels of lipid oxidization (F) and free fatty acids (G) in PPARα-deficient cells after GB1 treatment under an inverted fluorescence microscope. All data were presented as mean ± SEM of three independent experiments. ****, p < 0.001; ns, not significant.

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  Figure 6. GB1 fails to improve inflammation and apoptosis in PPARα-deficient cells. ROS level (A) and apoptosis (C) in PPARα-deficient cells did not change after GB1 treatment. GB1 failed to alter the levels of inflammatory genes (E), apoptosis-related genes (B), ALT (D), and MMP (F) in PPARα-deficient cells. All data were presented as mean ± SEM of three independent experiments.****, p < 0.001; ns, not significant.