Damaging effect of dietary inulin on intestinal enterocytes in Arcticcharr (Salvelinus alpinus L.)

摘要

The term dietary fibre refers to a wide range of carbohydrates that resist degradation by human alimentary tract enzymes (Roberfroid 1993). However, some fibres are fermented by intestinal microbiota, primarily those colonizing the large intestine, to various products that are utilized by the host. Inulin, a #beta#(->1-fructan fibre) is found in several natural foodstuffs (Roberfroid 1993; Van Loo, Coussement, Delenheer, Hoebregs & Smiths 1995). For reasons yet unknown, it is utilized almost exclusively by colonic bifidobacteria and bacteriodes which tend to increase numerically in the faeces of individuals fed this fibre (Gibson 1998; Roberfroid, van Loo & Gibson 1998). Selection of bifidobacteria has also been implicated in human health improvement by having a prebiotic potential (Gibson 1998). Further, it has been shown that dietary fibre increases the apparent absorption of calcium (Coudray, Bellanger, Castiglia Delavaud, Vermorel & Rayssignuier 1997). The prebiotic potential of inulin and other dietary fibres may also have interesting applications in fish aquaculture. Some information is available about fermentation of inulin by fish microbiota (camobacteria) (Ringo, Bendiksen, Gausen, Sundstjord & Olsen 1998; Ringo & Olsen 1999). It is also known that inulin alters the adherent microbiota of Arctic char (Salvelinus alpinus L.) (E. Ringo, R. Myklebust, T.M. Mayhew & R.E. Olsen, unpublished data). The bacterial population density of fish gastrointestinal tract is 10~6-10~8 aerobic heterotrophic bacteria and approximately 10~5 anaerobic bacteria g~(-1) (for review see Ringo, Strom & Tabachek 1995). This is much lower than the density reported for endothermic animals (Finegold, Sutter & Mathisen 1983). As part of a series of studies into the effect of dietary fibres on the salmonid Arctic chart, we also obtained samples for analysis of intestinal ultrastructure. The present results are preliminary reports of these findings.