New research directions in the last decade have led to major developments in the uses of plant lectins in bioscience and biomedicine. Major advances have been made in our understanding how lectins in ...the diet can act on the gastrointestinal tract and the physiological consequences of their actions, and how they can modulate body- and organ metabolism, the immune system and the gut microflora. Particularly striking progress has been made in unravelling the effects, often beneficial, of both orally- and parenterally administered lectins, including lectins of Viscum album-, Phaseolus vulgaris-, Robinia pseudoacacia, Agaricus bisporus, etc on tumours and in cancer therapy. Results have also made it possible to devise and try out other beneficial applications of plant lectins as gut-, metabolic- and hormonal regulators, immune reagents, probiotic/prebiotic oral supplements and to develop methods based on the oral application of lectins to protect the intestines against the often lethally harmful effects of chemo- and radiotherapy. With the development of genetically modified (GM) plants by transferring the genes of some of the natural insecticidal lectins such as the various Bacillus thuringiensis lectin-Cry toxins or some insecticidal plant lectins to major crop plants, a possible new avenue in plant protection may have opened up.
Diets containing genetically modified (GM) potatoes expressing the lectin Galanthus nivalis agglutinin (GNA) had variable effects on different parts of the rat gastrointestinal tract. Some effects, ...such as the proliferation of the gastric mucosa, were mainly due to the expression of the GNA transgene. However, other parts of the construct or the genetic transformation (or both) could also have contributed to the overall biological effects of the GNA-GM potatoes, particularly on the small intestine and caecum.
The polyamines putrescine, spermidine and spermine are essential for cell renewal and, therefore, are needed to keep the body healthy. It was previously believed that polyamines are synthesized by ...every cell in the body when required. However, in the present paper evidence is provided to show that, as in the case of the essential amino acids, the diet can supply sufficient amounts of polyamines to support cell renewal and growth. Systematic analysis of different foods was carried out and from the data obtained, the average daily polyamine consumption of British adults was calculated to be in the range 350–500 μmol/person per d. The major sources of putrescine were fruit, cheese and non-green vegetables. All foods contributed similar amounts of spermidine to the diet, although levels were generally higher in green vegetables. Meat was the richest source of spermine. However, only a part of the polyamines supplied by the diet is available for use by the body. Based on experiments with rats it was established that polyamines were readily taken up from the gut lumen, probably by passive diffusion, and were partly metabolized during the process of absorption. More than 80% of the putrescine was converted to other polyamines and non-polyamine metabolites, mostly to amino acids. The enzyme responsible for controlling the bioavailability of putrescine was diamine oxidase (EC 1.4.3.6). For spermidine and spermine, however, about 70–80% of the intragastrically intubated dose remained in the original form. Considering the limitations on bioavailability (metabolism and conversion), the amounts of polyamines supplied by the average daily diet in Britain should satisfy metabolic requirements.
The nutritional effects in the rat of raw lentil meal or its fractions have been evaluated in three feeding trials. Growth, gain/feed ratio, apparent N digestibility, and N retention were ...significantly (p < 0.05) reduced by the inclusion of whole lentil meal, dehulled lentil meal, or ethanol-extracted lentil meal as the sole source of protein in the diet. Pure lentil lectin and lectin-depleted albumin proteins had no significant negative effect on nutritional performance. In contrast, growth, gain/feed ratio, protein conversion efficiency, N digestibility, and N retention were significantly (p < 0.05) reduced by diets containing lentil globulins or lentil hulls. The poor nutritional quality of raw lentil meal for rats is therefore likely to be primarily due to the combined effects of these two components. Keywords: Lentils; nutritional utilization; lentil fractions; lentil lectin; rat
In this study we show that the characteristics of non-Hodgkin lymphoma (NHL) tumors in female Naval Medical Research Institute (NMRI, USA) mice fed mistletoe lectin (ML)-containing diets were ...different from those in mice fed control diet. The non-Hodgkin lymphoma tumor was originally established from a spontaneous tumor which developed in the inguinal region of a male mouse. Mice (five animals per group) were fed a lactalbumin (LA)-based control diet or a diet which provided up to 10
mg lectin per day. At the highest daily intake (10
mg lectin) the degree of mitotic activity in tumors was reduced by 75% and the nuclear area had diminished by 21%. The overall level of lymphocyte infiltration (CD3 positive cells) in tumors from mistletoe lectin fed mice was increased by a factor of two. Other morphological studies showed a high incidence of apoptotic bodies in non-Hodgkin lymphoma tumors obtained from mice fed mistletoe lectin diets. The feeding of such diets thus produced several identifiable changes in the morphology of non-Hodgkin lymphoma tumors. These were consistent with the observed reduction in tumor mass. In 4/15 mice fed a mistletoe lectin diet for 11 days there was no longer evidence of viable tumor. The results show that this lectin exerts powerful anti-tumor effects when provided by the oral route.
Oral exposure to lectins or the presence or absence of bacteria in the rat 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.
The activities of diamine and polyamine oxidases, two enzymes of polyamine catabolism, were studied in hyperplastic growth of rat small intestine induced by phytohaemagglutinin. This growth, ...evaluated by the elongation of Lieberkühn's crypts, was more extensive in the proximal than in the distal parts of the gut. The activity of diamine oxidase was significantly reduced in the proximal (70%), medial (45%) and the distal (25%) parts. The activity of polyamine oxidase was doubled. The concentrations of putrescine, cadaverine and spermidine were significantly elevated in the three intestinal parts studied, whereas those of histamine and spermine were unchanged. It appears that changes in the activities of diamine and polyamine oxidases may contribute to the increased putrescine content, which is necessary to maintain active polyamine turnover for sustaining growth of the gut.
The movement of a single dose of
14C-putrescine in the lumen of the rat gastrointestinal tract was followed for 3 hours after intragastric intubation. Putrescine progressed in the gut lumen in a ...wave-like fashion and was absorbed in the small bowel. Maximal uptake was observed at 2 hours; therefore, this time-point was selected to measure the concentration dependency of putrescine uptake by the small intestine and distribution between the vital organs in a wide concentration range (1/10 to 100 times the dietary input). Putrescine uptake by the small bowel was likely to be by passive diffusion, because the absorption was in proportion to input. The fate of putrescine was determined in the plasma, small bowel, liver, and skeletal muscle by measuring the radioactivity of the polyamines, their acetyl derivatives, and amino acids at physiologic concentrations. It appears that approximately 10% of the dietary input reaches the putrescine body pool.
A comprehensive scheme is described for the isolation of the major protein antinutrients present in soybean seeds, including the two classes of protease inhibitors, SBPI Kunitz (KSTI) and Bowman-Birk ...(BBI) and the seed agglutinin (SBA). A main feature is that no intermediate freeze-drying is necessary during the stepwise recovery of the antinutrients. All interfering saccharides are first removed by extraction with aqueous ethanol, during which a part of BBI is also obtained. The remaining antinutrients are selectively extracted at pH 5.8. SBA and SBPI are isolated by affinity chromatography on cross-linked guar gum and anhydrotrypsin-Sepharose 4B, respectively. Final separation of SBPI is done by HPLC on a TSK SP-5W cation exchanger. By the application of this purification scheme, the concerted effects of the protein (and other) antinutrients and possible synergisms in their action on the digestive system will be open for exploration
Experiments were designed to investigate whether orally consumed tomato lectin could resist the digestive process and function as a lectin within the alimentary canal. Rats fed on a tomato ...lectin-rich diet passed faeces containing serologically detectable tomato lectin, and the lectin could be shown by immunoperoxidase staining bound to intestinal villi. Moreover, radioactivity was mainly recovered from the alimentary canal 3h after
125I-labelled tomato lectin administration with only traces in the circulation or internal organs. Radioactivity absorbed into the human circulation after consumption of
125I-labelled tomato lectin was also less than that expected for a digestable protein.
Tomato lectin
Dietary lectin
Villus structure
Rat intestine
Human intestine
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