British Journal of Nutrition

Nutritional Effects of Biologically Active Components of Plants

Antinutritive effects of wheat-germ agglutinin and other N-acetylglucosamine-specific lectins

A. Pusztaia1, S. W. B. Ewena2, G. Granta1, D. S. Browna1, J. C. Stewarta1, W. J. Peumansa3, E. J. M. Van Dammea3 and S. Bardocza1

a1 The Rowett Research Institute, Bucksburn, Aberdeen AB2 9SB

a2 Department of Pathology, University of Aberdeen, Aberdeen AB9 2ZX

a3 Laboratory for Phytopathology and Plant Protection, Katholieke Universiteit Leuven, B-3001 Heverlee, Belgium

Abstract

Incorporation of N-acetylglucosamine-specific agglutinins from wheat germ (Triticum aestivum; WGA), thorn apple (Datura stramonium) or nettle (Urtica dioica) rhizomes in the diet at the level of 7 g/kg reduced the apparent digestibility and utilization of dietary proteins and the growth of rats, with WGA being the most damaging. As a result of their binding and endocytosis by the epithelial cells of the small intestine, all three lectins were growth factors for the gut and interfered with its metabolism and function to varying degrees. WGA was particularly effective; it induced extensive polyamine-dependent hyperplastic and hypertrophic growth of the small bowel by increasing its content of proteins, RNA and DNA. Furthermore, an appreciable portion of the endocytosed WGA was transported across the gut wall into the systemic circulation, where it was deposited in the walls of the blood and lymphatic vessels. WGA also induced the hypertrophic growth of the pancreas and caused thymus atrophy. Although the transfer of the gene of WGA into crop plants has been advocated to increase their insect resistance, as the presence of this lectin in the diet may harm higher animals at the concentrations required to be effective against most pests, its use in plants as natural insecticide is not without health risks for man.

(Received July 07 1992)

(Accepted September 07 1992)