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Phytosterol Ester Constituents Affect Micellar Cholesterol Solubility in Model Bile

  • Original Article
  • Published:
Lipids

Abstract

Plant sterols and stanols (phytosterols) and their esters are nutraceuticals that lower LDL cholesterol, but the mechanisms of action are not fully understood. We hypothesized that intact esters and simulated hydrolysis products of esters (phytosterols and fatty acids in equal ratios) would differentially affect the solubility of cholesterol in model bile mixed micelles in vitro. Sodium salts of glycine- and taurine-conjugated bile acids were sonicated with phosphatidylcholine and either sterol esters or combinations of sterols and fatty acids to determine the amount of cholesterol solubilized into micelles. Intact sterol esters did not solubilize into micelles, nor did they alter cholesterol solubility. However, free sterols and fatty acids altered cholesterol solubility independently (no interaction effect). Equal contents of cholesterol and either campesterol, stigmasterol, sitosterol, or stigmastanol (sitostanol) decreased cholesterol solubility in micelles by approximately 50% compared to no phytosterol present, with stigmasterol performing slightly better than sitosterol. Phytosterols competed with cholesterol in a dose-dependent manner, demonstrating a 1:1 M substitution of phytosterol for cholesterol in micelle preparations. Unsaturated fatty acids increased the micelle solubility of sterols as compared with saturated or no fatty acids. No differences were detected in the size of the model micelles. Together, these data indicate that stigmasterol combined with saturated fatty acids may be more effective at lowering cholesterol micelle solubility in vivo.

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Abbreviations

DHA:

Docosahexaenoic acid

EPA:

Eicosapentaenoic acid

GC:

Gas chromatography

HDL:

High-density lipoprotein

LDL:

Low-density lipoprotein

N2 :

Molecular nitrogen

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Acknowledgments

The authors would like to thank Kate Wolford, Aaron Brandt, and Paige Lundy for help with sample preparation and analysis. A.W.B. and J.H. were supported by National Research Initiative Grant 2007-35200-18298 from the USDA National Institute of Food and Agriculture. The research was also supported in part by the University of Nebraska Agricultural Research Division with funds provided through the Hatch Act. Portions of this work were conducted in facilities remodeled with support from National Institutes of Health (NIH RR016544-01).

Conflict of interest

None of the authors have any conflicts of interest to disclose.

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Authors and Affiliations

  1. Department of Nutrition and Health Sciences, University of Nebraska-Lincoln, 316 Leverton Hall, Lincoln, NE, 68583-0806, USA

    Andrew W. Brown & Timothy P. Carr

  2. Department of Chemistry, University of Nebraska-Lincoln, Lincoln, NE, USA

    Jiliang Hang & Patrick H. Dussault

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  1. Andrew W. Brown
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  2. Jiliang Hang
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  3. Patrick H. Dussault
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  4. Timothy P. Carr
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Correspondence to Timothy P. Carr.

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Brown, A.W., Hang, J., Dussault, P.H. et al. Phytosterol Ester Constituents Affect Micellar Cholesterol Solubility in Model Bile. Lipids 45, 855–862 (2010). https://doi.org/10.1007/s11745-010-3456-6

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  • DOI: https://doi.org/10.1007/s11745-010-3456-6

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