Journal of Lipid Research, Vol 35, 741-748, Copyright © 1994 by Lipid Research, Inc.

ARTICLES

Characterization of the adsorption of conjugated and unconjugated bile acids to insoluble, amorphous calcium phosphate

MJ Govers, DS Termont, GA Van Aken and R Van der Meer
Department of Nutrition, Netherlands Institute for Dairy Research (NIZO), Ede.

Recently we showed that supplemental dietary calcium stimulates the intestinal formation of insoluble calcium phosphate and decreases the ratio of dihydroxy to trihydroxy bile acids in human duodenal bile. Because previous in vitro studies indicated that these effects could be due to differential adsorption of bile acids to amorphous calcium phosphate, we characterized the binding of bile acids to calcium phosphate. Freshly formed, amorphous, calcium phosphate bound and thus precipitated glycine-conjugated and unconjugated bile acids, whereas taurine-conjugated bile acids showed little binding. Glycochenodeoxycholic acid hardly adsorbed to other insoluble calcium phosphates, including hydroxyapatite. Adsorption studies using increasing amounts of glycine-conjugated and unconjugated bile acids showed that binding occurred above a bile acid-specific critical minimum concentration, dependent on bile acid hydrophobicity. The simultaneous use of a fluorescent hydrophobic probe indicated that this binding was due to ionic adsorption of monomers of bile acids, followed by their hydrophobic aggregation on the calcium phosphate surface, probably in the form of a bilayer. Finally, using human duodenal bile we found that amorphous calcium phosphate, but not Ca2+, preferentially bound and thus precipitated dihydroxy bile acids. We conclude that freshly formed, amorphous, calcium phosphate is a prerequisite for adsorption of bile acids and that monomers of glycine-conjugated and unconjugated dihydroxy bile acids have a high binding affinity for amorphous calcium phosphate.
CiteULike    Complore    Connotea    Del.icio.us    Digg    Reddit    Technorati    What's this?

This article has been cited by other articles:

				L. C. Pele, V. Thoree, F. Mustafa, S. He, L. Tsaprouni, N. A. Punchard, R. P. H. Thompson, S. M. Evans, and J. J. Powell Low Dietary Calcium Levels Modulate Mucosal Caspase Expression and Increase Disease Activity in Mice with Dextran Sulfate Sodium Induced Colitis J. Nutr., November 1, 2007; 137(11): 2475 - 2480. [Abstract] [Full Text] [PDF]

				J. K. Lorenzen, S. Nielsen, J. J. Holst, I. Tetens, J. F. Rehfeld, and A. Astrup Effect of dairy calcium or supplementary calcium intake on postprandial fat metabolism, appetite, and subsequent energy intake Am. J. Clinical Nutrition, March 1, 2007; 85(3): 678 - 687. [Abstract] [Full Text] [PDF]

				B. Ditscheid, S. Keller, and G. Jahreis Cholesterol Metabolism Is Affected by Calcium Phosphate Supplementation in Humans J. Nutr., July 1, 2005; 135(7): 1678 - 1682. [Abstract] [Full Text] [PDF]

				C. Yuangklang, Th. Wensing, L. Van den Broek, S. Jittakhot, and A. C. Beynen Fat Digestion in Veal Calves Fed Milk Replacers Low or High in Calcium and Containing Either Casein or Soy Protein Isolate J Dairy Sci, April 1, 2004; 87(4): 1051 - 1056. [Abstract] [Full Text] [PDF]

				A. L. A. Sesink, D. S. M. L. Termont, J. H. Kleibeuker, and R. Van der Meer Red meat and colon cancer: dietary haem-induced colonic cytotoxicity and epithelial hyperproliferation are inhibited by calcium Carcinogenesis, October 1, 2001; 22(10): 1653 - 1659. [Abstract] [Full Text] [PDF]

				I. M. Bovee-Oudenhoven, M. L. Wissink, J. T. Wouters, and R. Van der Meer Dietary Calcium Phosphate Stimulates Intestinal Lactobacilli and Decreases the Severity of a Salmonella Infection in Rats J. Nutr., March 1, 1999; 129(3): 607 - 612. [Abstract] [Full Text]

				A. A. van den Berg, J. D. van Buul, G. N. J. Tytgat, A. K. Groen, and J. D. Ostrow Mucins and calcium phosphate precipitates additively stimulate cholesterol crystallization J. Lipid Res., September 1, 1998; 39(9): 1744 - 1751. [Abstract] [Full Text]