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Curcumin inhibits cholesterol uptake in Caco-2 cells by down-regulation of NPC1L1 expression.

Feng D, Ohlsson L, Duan RD - Lipids Health Dis (2010)

Bottom Line: Previous in vivo studies showed that administration of curcumin also decreased cholesterol levels in the blood, and the effects were considered to be related to upregulation of LDL receptor.We then pretreated the cells with 25-100 muM curcumin for 24 h and found that such a treatment dose-dependently inhibited cholesterol uptake with 40% inhibition obtained by 100 muM curcumin.In addition, we found that the curcumin-induced inhibition of cholesterol uptake was associated with significant decrease in the levels of NPC1L1 protein and NPC1L1 mRNA, as analyzed by Western blot and qPCR, respectively.

View Article: PubMed Central - HTML - PubMed

Affiliation: Gastroenterology and Nutrition Laboratory, Biomedical Center B11, Institution of Clinical Sciences, University of Lund, Lund, Sweden.

ABSTRACT

Background: Curcumin is a polyphenol and the one of the principle curcuminoids of the spice turmeric. Its antioxidant, anti-cancer and anti-inflammatory effects have been intensively studied. Previous in vivo studies showed that administration of curcumin also decreased cholesterol levels in the blood, and the effects were considered to be related to upregulation of LDL receptor. However, since plasma cholesterol levels are also influenced by the uptake of cholesterol in the gut, which is mediated by a specific transporter Niemann-Pick Cl-like 1 (NPC1L1) protein, the present study is to investigate whether curcumin affects cholesterol uptake in the intestinal Caco-2 cells.

Methods: Caco-2 cells were cultured to confluence. The micelles composed of bile salt, monoolein, and 14C-cholesterol were prepared. We first incubated the cells with the micelles in the presence and absence of ezetimibe, the specific inhibitor of NPC1L1, to see whether the uptake of the cholesterol in the cells was mediated by NPC1L1. We then pretreated the cells with curcumin at different concentrations for 24 h followed by examination of the changes of cholesterol uptake in these curcumin-treated cells. Finally we determined whether curcumin affects the expression of NPC1L1 by both Western blot analysis and qPCR quantification.

Results: We found that the uptake of radioactive cholesterol in Caco-2 cells was inhibited by ezetimibe in a dose-dependent manner. The results indicate that the uptake of cholesterol in this study was mediated by NPC1L1. We then pretreated the cells with 25-100 muM curcumin for 24 h and found that such a treatment dose-dependently inhibited cholesterol uptake with 40% inhibition obtained by 100 muM curcumin. In addition, we found that the curcumin-induced inhibition of cholesterol uptake was associated with significant decrease in the levels of NPC1L1 protein and NPC1L1 mRNA, as analyzed by Western blot and qPCR, respectively.

Conclusion: Curcumin inhibits cholesterol uptake through suppression of NPC1L1 expression in the intestinal cells.

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Related in: MedlinePlus

The effect of curcumin on NPC1L1 protein expression in Caco-2 cells. In the upper panel, the cells were treated with curcumin at different concentrations for 24 h, and the whole-cell lysates were analyzed by Western blot. The results are representative of three independent experiments. In the lower panel, NPC1L1 mRNA abundance was determined by real-time RT-PCR as described in Methods. Expression values were normalized to housekeeping genes, and expression in untreated cells was set to 1. Values shown represent means ± SEM of three independent experiments, * P < 0.01, ** P < 0.001 compared to untreated cells.
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Figure 3: The effect of curcumin on NPC1L1 protein expression in Caco-2 cells. In the upper panel, the cells were treated with curcumin at different concentrations for 24 h, and the whole-cell lysates were analyzed by Western blot. The results are representative of three independent experiments. In the lower panel, NPC1L1 mRNA abundance was determined by real-time RT-PCR as described in Methods. Expression values were normalized to housekeeping genes, and expression in untreated cells was set to 1. Values shown represent means ± SEM of three independent experiments, * P < 0.01, ** P < 0.001 compared to untreated cells.

Mentions: We then further studied whether curcumin could influence the levels of NPC1L1 in the intestinal cells. As shown in upper panel of Fig. 3, pretreatment of the cells with different concentrations of curcumin for 24 h significantly attenuated NPC1L1 protein levels. No similar changes could be identified for the levels of actin. To distinguish whether the effect was caused by an increased degradation or a decreased biosynthesis, the levels of mRNA of NPC1L1 after treating the cells with curcumin were quantified. As shown in the lower panel of Fig. 3, curcumin induced a dose-dependent reduction of NPC1L1 mRNA, as normalized with that of control gene GAPDH. About 50% inhibition could be identified by 50 μM curcumin.


Curcumin inhibits cholesterol uptake in Caco-2 cells by down-regulation of NPC1L1 expression.

Feng D, Ohlsson L, Duan RD - Lipids Health Dis (2010)

The effect of curcumin on NPC1L1 protein expression in Caco-2 cells. In the upper panel, the cells were treated with curcumin at different concentrations for 24 h, and the whole-cell lysates were analyzed by Western blot. The results are representative of three independent experiments. In the lower panel, NPC1L1 mRNA abundance was determined by real-time RT-PCR as described in Methods. Expression values were normalized to housekeeping genes, and expression in untreated cells was set to 1. Values shown represent means ± SEM of three independent experiments, * P < 0.01, ** P < 0.001 compared to untreated cells.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC2865464&req=5

Figure 3: The effect of curcumin on NPC1L1 protein expression in Caco-2 cells. In the upper panel, the cells were treated with curcumin at different concentrations for 24 h, and the whole-cell lysates were analyzed by Western blot. The results are representative of three independent experiments. In the lower panel, NPC1L1 mRNA abundance was determined by real-time RT-PCR as described in Methods. Expression values were normalized to housekeeping genes, and expression in untreated cells was set to 1. Values shown represent means ± SEM of three independent experiments, * P < 0.01, ** P < 0.001 compared to untreated cells.
Mentions: We then further studied whether curcumin could influence the levels of NPC1L1 in the intestinal cells. As shown in upper panel of Fig. 3, pretreatment of the cells with different concentrations of curcumin for 24 h significantly attenuated NPC1L1 protein levels. No similar changes could be identified for the levels of actin. To distinguish whether the effect was caused by an increased degradation or a decreased biosynthesis, the levels of mRNA of NPC1L1 after treating the cells with curcumin were quantified. As shown in the lower panel of Fig. 3, curcumin induced a dose-dependent reduction of NPC1L1 mRNA, as normalized with that of control gene GAPDH. About 50% inhibition could be identified by 50 μM curcumin.

Bottom Line: Previous in vivo studies showed that administration of curcumin also decreased cholesterol levels in the blood, and the effects were considered to be related to upregulation of LDL receptor.We then pretreated the cells with 25-100 muM curcumin for 24 h and found that such a treatment dose-dependently inhibited cholesterol uptake with 40% inhibition obtained by 100 muM curcumin.In addition, we found that the curcumin-induced inhibition of cholesterol uptake was associated with significant decrease in the levels of NPC1L1 protein and NPC1L1 mRNA, as analyzed by Western blot and qPCR, respectively.

View Article: PubMed Central - HTML - PubMed

Affiliation: Gastroenterology and Nutrition Laboratory, Biomedical Center B11, Institution of Clinical Sciences, University of Lund, Lund, Sweden.

ABSTRACT

Background: Curcumin is a polyphenol and the one of the principle curcuminoids of the spice turmeric. Its antioxidant, anti-cancer and anti-inflammatory effects have been intensively studied. Previous in vivo studies showed that administration of curcumin also decreased cholesterol levels in the blood, and the effects were considered to be related to upregulation of LDL receptor. However, since plasma cholesterol levels are also influenced by the uptake of cholesterol in the gut, which is mediated by a specific transporter Niemann-Pick Cl-like 1 (NPC1L1) protein, the present study is to investigate whether curcumin affects cholesterol uptake in the intestinal Caco-2 cells.

Methods: Caco-2 cells were cultured to confluence. The micelles composed of bile salt, monoolein, and 14C-cholesterol were prepared. We first incubated the cells with the micelles in the presence and absence of ezetimibe, the specific inhibitor of NPC1L1, to see whether the uptake of the cholesterol in the cells was mediated by NPC1L1. We then pretreated the cells with curcumin at different concentrations for 24 h followed by examination of the changes of cholesterol uptake in these curcumin-treated cells. Finally we determined whether curcumin affects the expression of NPC1L1 by both Western blot analysis and qPCR quantification.

Results: We found that the uptake of radioactive cholesterol in Caco-2 cells was inhibited by ezetimibe in a dose-dependent manner. The results indicate that the uptake of cholesterol in this study was mediated by NPC1L1. We then pretreated the cells with 25-100 muM curcumin for 24 h and found that such a treatment dose-dependently inhibited cholesterol uptake with 40% inhibition obtained by 100 muM curcumin. In addition, we found that the curcumin-induced inhibition of cholesterol uptake was associated with significant decrease in the levels of NPC1L1 protein and NPC1L1 mRNA, as analyzed by Western blot and qPCR, respectively.

Conclusion: Curcumin inhibits cholesterol uptake through suppression of NPC1L1 expression in the intestinal cells.

Show MeSH
Related in: MedlinePlus