A Green Tea Catechin Extract Upregulates the Hepatic Low-Density Lipoprotein Receptor in Rats

Abstract

Green tea extracts have hypocholesterolaemic properties in epidemiological and animal intervention studies. Upregulation of the low-density lipoprotein (LDL) receptor may be one mechanism to explain this as it is the main way cholesterol is removed from the circulation. This study aimed to determine if a green tea extract could upregulate the hepatic LDL receptor in vivo in the rat. A green tea extract (GTE) enriched in its anti-oxidant constituents, the catechins, was fed to rats (n = 6) at concentrations of either 0, 0.5, 1.0 or 2.0% (w/w) mixed in with their normal chow along with 0.25% (w/w) cholesterol for 12 days. Administration of the GTE had no effect on plasma total or LDL cholesterol concentrations but high-density lipoprotein significantly increased (41%; p < 0.05). Interestingly, there was a significant increase in LDL receptor binding activity (2.7-fold) and LDL receptor protein (3.4-fold) in the 2% (w/w) treatment group compared to controls. There were also significant reductions in liver total and unesterified cholesterol (40%). Administration of the GTE significantly reduced cholesterol absorption (24%) but did not affect cholesterol synthesis. These results show that, despite no effect on plasma cholesterol, the GTE upregulated the LDL receptor in vivo. This appears to be via a reduction in liver cholesterol concentration and suggests that the green tea extract was able to increase the efflux of cholesterol from liver cells.

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Acknowledgments

We would like to thank the University of Adelaide for providing Christina Bursill with a postgraduate scholarship and additional funding.

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Correspondence to Christina A. Bursill.

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Bursill, C.A., Roach, P.D. A Green Tea Catechin Extract Upregulates the Hepatic Low-Density Lipoprotein Receptor in Rats. Lipids 42, 621–627 (2007). https://doi.org/10.1007/s11745-007-3077-x

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Keywords

  • Green tea
  • LDL receptor
  • Cholesterol synthesis
  • Cholesterol absorption
  • Lathosterol
  • Phytosterols