Transgenic Alfalfa That Accumulates Piceid (Trans-Resveratrol-3-O−β-D-glucopyranoside) Requires the Presence of β -Glucosidase to Inhibit the Formation of Aberrant Crypt Foci in the Colon of CF-1 Mice

Abstract:

Plants have been genetically enhanced to produce a number of products for agricultural, industrial and pharmaceutical purposes. This technology could potentially be applied to providing chemoprevention strategies to the general population. Resveratrol (3,5,4′-trihydroxystilbene) is a compound that has been shown to have protective activity against a number of cancers and could be an ideal candidate for such an application. Alfalfa that was genetically modified to express resveratrol-synthase was used as a model in applying biotechnological approaches to cancer prevention. The transgenic alfalfa, which accumulates resveratrol as a glucoside (piceid = trans-resveratrol-3-O−β-D-glucopyranoside) (152 ± 17.5 μ g piceid/g dry weight), was incorporated into a standard mouse diet at 20% of the diet by weight and fed for 5 wk to 6-wk-old, female CF-1 mice (N = 17–30) that were injected with a single dose of azoxymethane (5 mg/kg body weight). While the addition of resveratrol-aglycone (20 mg/kg diet) to the basal diet reduced the number of aberrant crypt foci/mouse, the transgenic alfalfa did not inhibit the number, size, or multiplicity of aberrant crypt foci in the colon of the CF-1 mice relative to control alfalfa which does not accumulate resveratrol-glucoside. However, diets containing transgenic alfalfa with an exogenous β -glucosidase (860 U/kg diet) did significantly inhibit the number of aberrant crypt foci in the distal 2 cm of the colon of the mice relative to mice fed diets containing the transgenic alfalfa without the enzyme (P < 0.05; Fisher's Combination of p-values). The β -glucosidase alone appeared to have no effect on the inhibition of aberrant crypt foci. These results suggest that piceid in transgenic piceid-accumulating alfalfa was not bioavailable.

Acknowledgments and Notes

This work was supported by grants from the American Institute for Cancer Research (AICR) (grant # 03B040-REV), the United States Department of Agriculture special grant for the Centers for Designing Foods to Improve Nutrition (CDFIN) at Iowa State University, Ames, IA, the Iowa Agriculture and Home Economics Experimental Station (IAHEES) and the Samuel Roberts Noble Foundation, Ardmore, OK. We would like to thank Kimberly Hammer, Brian Hopper, Joseph Przybyszewski, Laura Schmitt, Jeanne Stewart, and Weiqun Wang for their assistance in processing colon samples.

Notes

∗Comparing no enzyme vs. enzyme treatments P-values were derived using Fisher's combination of tests of significance analysis. P-values for individual studies are listed in the parentheses under the combined P-values for each comparison.