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P.J. Hainsworth [1] M.K. Bennett [1] M. Hudson [1] P.W. Dettmar [2] (1.) Freemen Hospital, Newcastle upon Tyne, UK; (2.) Reckitt & Calman Healthcare (UK) Ltd, Hull, UK Introduction: The [...]

P.W. Dettmar [1] Dept of Physiological sciences, The Medical School, University of Newcastle upon Tyne, NE2 4HH; (1.) ReckiuBenckiser Healthcare, Dansom Lane, Hull HU8 7DS, UK Introduction: We have previously [...]

This study aimed to characterise the effect of dietary fibre type on levels of mucosal reddening and the protective capability of the colonic mucus barrier in an in vivo model. The effects of 8 week feeding of six different fibre containing diets were ascertained on Wistar rats, and compared to control diets (standard chow). Each diet contained approximately 14% fibre by weight, except the fibre deficient diet. After this time, the maximal colonic mucus thickness and replenishment rates were measured in vivo using an intravital microscopy technique. Initial mucosal redness and intracellular mucin were assessed by densitometric image analysis of in vivo and histological microphotographs, respectively. Fibre deficient, pectin, and cellulose diets reduced maximal mucus thickness (> 100 µm thinner than 550 pm control) and mucus replenishment rates (by > 50%) compared with controls (p < 0.001), but not intracellular mucin. Pectin and cellulose diets significantly increased colonic mucosal reddening (p < 0.001). An ispaghula husk diet increased intracellular colonic mucin levels (p < 0.05) by 28%. Inclusion of 1% alginate in the diet lead to an elevation of maximal mucus thickness (103 µm thicker than control) and a reduced level of mucosal reddening by 15% (p < 0.001). Higher levels of alginate (ie 5%) had no effect. Dietary fibre types that caused a reduction in the protective capacity (namely pectin and cellulose) of the colonic mucus layer lead to an increase in mucosal redness. These results suggest fibre type and inclusion in the diet modulates both the protective potential of the colonic mucus layer, and also levels of mucosal damage. Certain Fibre types may be of benefit in the possible prevention and alleviation of certain diseases (eg IBDs, lBS), where colonic protection by the mucus layer is reduced. [ABSTRACT FROM AUTHOR]

This study aimed to determine the effects of reactive oxygen species (ROS) and butyrate on the protective capacity of the colonic mucus layer in vivo. An intravital microscopy technique was used to measure the maximal thickness and replenishment rates (rate of mucus secretion after partial removal of the layer by suction) of the colonic mucus layer of anaesthetised male Wistar rats (n = 5 for each treatment) over 5 h under 7 mM butyrate (normal concentration in the rat colon), as well as ROS solutions containing 0.5 mM Fe[sup ++]/EDTA mixed with 5-50 mM H[sub 2]O[sub 2]. These effects were compared to saline controls (n = 5). Maximal mucus thickness was not affected by 7 mM butyrate or 10 mM H[sub 2]O[sub 2], but 5 mM H[sub 2]O[sub 2] significantly increased maximal mucus thickness, whereas ROS solutions containing more than 10 mM peroxide (ie 17.5, 25, and 50 mM) significantly reduced the thickness of the mucus barrier (50% in the case of 50 mM H[sub 2]O[sub 2]). 7 mM butyrate significantly increased mucus layer replenishment rate over the first hour of measurement (×3 faster than the saline control. Measurement of the effect of ROS on colonic mucus layer replenishment was hampered by release of plasma exudate and red blood cells from the colonic mucosa. This suggests that Iow millimolar concentrations of butyrate and ROS may increase the protective capacity of the colonic mucus layer, possibly as a cytoprotective response. Higher levels of ROS appear to be damaging to both the mucus layer and mucosa, especially once the mucus layer is depleted. This study shows that bacterial metabolites may alter the protective potential of the colonic mucus barrier. [ABSTRACT FROM AUTHOR]