Submitted to: Cereal Chemistry
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/17/2007
Publication Date: 1/15/2008
Citation: Funk, C., Grabber, J.H., Steinhart, H., Bunzell, M. 2008. Artificial Lignification of Maize Cell Walls Does Not Affect Bile Acid Adsorption. Cereal Chemistry. 85:14-18. Interpretive Summary: Bile acids are biosynthesized from cholesterol in the liver and secreted into the intestine where they aid in the digestion of dietary fat. Binding of bile acids to dietary fiber may stimulate bile acid biosynthesis to reduce blood levels of artery clogging cholesterol. In addition, binding of excess bile acids to dietary fiber may help prevent the onset and progression of colon cancer. The aim of our study was to clearly delineate whether lignin influences the binding of bile acids to dietary fiber. Lignin is naturally found in many types of dietary fiber and it acts to glue polysaccharides, protein, and other components in fiber together. Using conditions mimicking the intestine, we measured the absorption of various bile acids to corn (Zea mays L.) fiber that was carefully generated in our laboratory to contain various types and quantities of lignin. We found that neither lignin concentration nor composition influenced bile acid adsorption. Thus, researchers should study how other components of fiber may influence bile adsorption. Such work may identify new ways of reducing bile-related diseases in people.
Technical Abstract: Bile acid adsorption by lignified dietary fiber in the human intestine is proposed as a mechanism for lowering blood cholesterol level and reducing colon cancer risk. In this study, we investigated how the concentration and composition of lignin in fiber influences the in vitro adsorption of primary bile acids (glycocholate, taurocholate and glycochenodeoxycholate) and a secondary bile acid (deoxycholate). Adsorption studies were performed by incubating nonlignified and artificially lignified maize cell walls (dehydrogenation polymer-cell walls) with bile acids under conditions imitating the small intestine and colon. Artificially lignified cell walls had varying but defined lignin concentrations (4.8-19.0%) and compositions (varying from pure guaiacyl to pure syringyl lignins), but a uniform polysaccharide-protein matrix. Adsorption of bile acids by cell walls varied from 6-31% (4-26 nmol bile acids/mg cell walls), with glycochenodeoxycholate showing the highest adsorption rates. Neither lignin concentration nor lignin composition influenced bile acid adsorption, thus disproving a major role of lignin in bile acid adsorption.