Lectinology? See Also
DiscussionAbstractsAntinutritive effects of wheat-germ agglutinin and other N-acetylglucosamine-specific lectinsBr J Nutr 1993 Jul;70(1):313-321 Pusztai A, Ewen SW, Grant G, Brown DS, Stewart JC, Peumans WJ, Van Damme EJ, Bardocz S Rowett Research Institute, Bucksburn, Aberdeen. 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. Lectins and also bacteria modify the glycosylation of gut surface receptors in the ratGlycoconj J 1995 Feb;12(1):22-35 Pusztai A, Ewen SW, Grant G, Peumans WJ, Van Damme EJ, Coates ME, Bardocz S Rowett Research Institute, Bucksburn, Aberdeen, UK. Oral exposure to lectins or the presence or absence of bacteria in the small intestine were shown by histological methods using anti-lectin antibodies or digoxigenin-labelled lectins to have major effects on the state of glycosylation of lumenal membranes and cytoplasmic glycoconjugates of epithelial cells. Taken together with the dramatic effects of exposure to lectins on gut function, metabolism and bacterial ecology, this can be used as a basis for new perspectives of biomedical manipulations to improve health. Relationship between survival and binding of plant lectins during small intestinal passage and their effectiveness as growth factorsDigestion 1990;46 Suppl 2:308-316 Pusztai A, Ewen SW, Grant G, Peumans WJ, van Damme EJ, Rubio L, Bardocz S Rowett Research Institute, Bucksburn, Aberdeen, Scotland, UK.
Toxicity of kidney bean (Phaseolus vulgaris) in rats: changes in intestinal permeabilityDigestion 1985;32(1):42-46 Greer F, Pusztai A
Effect of kidney bean (Phaseolus vulgaris) toxin on tissue weight and composition and some metabolic functions of ratsBr J Nutr 1985 Jul;54(1):95-103 Greer F, Brewer AC, Pusztai A
The nutritional toxicity of Phaseolus vulgaris lectinsProc Nutr Soc 1979 May 1;38(1):115-120 Pusztai A, Clarke EM, King TP In rats fed on beans (Phaseolus vulgaris) the poorly digestible lectins were shown to react with intestinal cells in vivo and to cause a disruption of many of the brush borders of duodenal and jejunal enterocytes. Although depressed to a certain extent, absorption still occurred, probably through the non-disrupted cells of the small intestine. In addition, abnormal absorption of potentially harmful substances, lectin-related or of bacterial origin, could also occur, possibly as a direct effect of the disruption caused by the lectins on the enterocytes. It is suggested that toxicity was the result of ensuing systemic effects, such as for example the observed high N excretion possibly through increased tissue catabolism. Effect of phytohaemagglutinin on intestinal cell proliferation. Role of polyaminesArch Latinoam Nutr 1996 Dec;44(4 Suppl 1):16S-20S Bardocz S, Rowett Research Institute, Aberdeen, Scotland, UK. The polyamines, putrescine, spermidine and spermine, mediate the effects of hormones and growth factors as second messengers. They are necessary for every step of protein, RNA and DNA synthesis and are therefore essential for cell growth and proliferation. As with hormones and peptide growth factors, plant lectins which bind to cell surface receptors of the brush border membrane are powerful extraneous growth factors for the gut and as a result, by interacting with brush border epithelial receptors, induce extensive proliferation and changes in the metabolism of epithelial cells via activation of second messenger pathways.These metabolic changes require vast amounts of polyamines, mostly spermidine. Thus, one of the first effects of the PHA signal is to stimulate the basolateral polyamine uptake system for the sequestration of polyamines from blood circulation in sufficient amounts to sustain the growth of the tissue. |
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