We are conducting a research on metabolic effects of lignin isolated from paper production waste. Lignin is a huge net-polyphenol molecule. We can see some promissing results, but we still missing some crucial information, which is whether is lignin absorbed in the intestines and whether it is somehow metabolized before/ during absorption. Do you have some experience or ideas about labeling isolated polyphenol molecule to be able to later determine its penetration to the blood stream and organs? We were thinking about adding FITC-label. But will it endure gastric digestion and stay attached to the lignin molecule?
Tannic acid inhibition of amino acid and sugar absorption by mouse and vole intestine.Tannins inhibit absorption of other nutrient in intestine. They disturb uptake of sugar and amino acid uptake across the brash border (luminal membrane) of intact intestine in the presence and absence of TA. There occurs a reduction in carrier-mediated influx of d-glucose and total influx of l-proline in mice A diet that conatin more than 4% TA, imose significant effect on intestinal brush border uptake ofl-glucose,d-glucose, orl-proline (or three other amino acids tested in voles). It absorption also effects across solutes, and depends on time scales of exposure, and species. First, the transport inhibitory effects following acute exposure are probably mediated by two processes: increased resistance to passive flux across an effective unstirred layer juxtaposed to the brush border membrane, perhaps due to tannin-mucin binding, and reduced Na+-coupled nutrient uptake across the intestinal brush border. Second, there is a species sensitivity difference in TA's effect on the second process. Third, the negative effects observed at the acute time scale in vitro do not necessarily occur in animals eating TA subchronically because little TA reaches the luminal membrane, or if it does its effects are quickly reversed when the tissue is removed and washed with solution free of TA. There is a possibility that in tannin feeding insects may show gastric digestion of lignin molecule. If it so then I feel it will become a new topic of research.
I don't think lignin is digestible since these macromolecules are almost connected in C-C and/or etheric linkages. Tow possible explanations are: 1) the microflora in the gut degraded the lignins and released some smaller ones, 2) the absorbed smaller polyphenols that could have been degraded and hidden in the macromolecular lignins during the treatment of paper production process essentially.
Accordingly, the resolutions for these two hypothesis could be: 1) let lignins fermented by gut microflora to see if small molecular polyphenols released, 2)use a dynamic extraction process to see if the small molecules were absorbed in the lignins.
Many thanks to all of you!
Dr. Upadhyay: We never thought of changes in absorption of sugars! We have allways considered possible inhibition in fat absorption, however we saw no changes in lipids content in feces. But sugars... well, we have to have a look at it! Great idea.
Dr. Lu - these are very much the thoughts we aterted to fllow in last few days. There is a strong possibility that the lignin mixture will be very heterogenous in the molecular size, so we could have a look for smaller phenolic frangments.
I am curious about microbiotic fermentation processes - how would you quantify such process? Would you make it in vivo, or would you make some kind of in vitro culture from animal samples?
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