Increasing dietary oat fibre decreases the permeability of intestinal mucus

Investigation of mechanisms involved in postprandial glycemia and insulinemia attenuation with dietary fibre consumption

This work examines the mechanisms involved in the attenuation of postprandial glycemic and insulinemic responses associated with soluble dietary fibre (SDF) consumption. The effect of SDF, including yellow mustard mucilage, soluble flaxseed gum and fenugreek gum on in vitro amylolysis and maltose transport was studied. Furthermore, a human clinical trial was conducted to investigate the effect of SDF consumption on postprandial glycemic and insulinemic responses and gastric emptying, as estimated based on the absorption of paracetamol. Participants (n = 15) at risk for type II diabetes consumed maltose syrup- and starch-based pudding treatments supplemented with each SDF, each at a concentration to match three times the apparent viscosity (18.54 mPa s at 60 s^-1) equivalent to the European Food Safety Authority (2011) glycemia control health claim for cereal β-glucan, measured under simulated small intestinal conditions. The presence of each SDF delayed in vitro amylolysis to a similar extent, but had no effect on maltose transport. Generally, all SDF-containing treatments attenuated blood glucose and plasma insulin peak concentrations and plasma paracetamol 1 h incremental area under the curve values to a similar extent, relative to the controls, despite differences in the amounts at which each SDF was used (from 5.9 to 15.5 g). The postprandial attenuations were related to the ability of each SDF to modify digesta viscosity, perhaps through the delay of gastric emptying, as a delay of amylolysis and sugar transport under simulated upper intestinal conditions did not seem to have a substantial effect.

Reduction in circulating bile acid and restricted diffusion across the intestinal epithelium are associated with a decrease in blood cholesterol in the presence of oat β-glucan

Although oat (1,3:1,4)-β-glucan (BG) has been shown to decrease blood cholesterol in intervention trials, the detailed mechanism is not yet defined, but restricted reabsorption of bile acids (BAs) has been hypothesized. Using pigs as a model for humans we demonstrated that, compared to the control, BG added to the diet for 26 d caused decreases of 24% in blood total BAs (TBAs), 34% in total cholesterol (TC), and 57% in LDL cholesterol (LDL-C) (P < 0.01); decreases of 20% TBA in the midjejunum and terminal ileum (P < 0.01); increases of 80% in cecal total neutral sterols (TNSs) including cholesterol (P < 0.01); a 50% reduction in BA active transport across ex vivo ileum after 40 min (P < 0.001); and 32% decrease in jejunal microvillus heights with apparent increased goblet cell activity. The results suggest that BG not only physically hinders the active reabsorption of BAs and uptake of cholesterol, but also changes the BAs profile with lower circulating levels without excess excretion in the feces, thus resulting in reduced blood TC and LDL-C. Fermentation of sterols reaching the colon enhanced production of therapeutic ursodeoxycholic acid, suppressed toxic lithocholic acid, and decreased the possibility of cholesterol absorption by transforming the latter into coprostanol, a nonabsorbable NS.-Gunness, P., Michiels, J., Vanhaecke, L., De Smet, S., Kravchuk, O., Van de Meene, A., Gidley, M. J. Reduction in circulating bile acid and restricted diffusion across the intestinal epithelium are associated with a decrease in blood cholesterol in the presence of oat β-glucan.