Effect of unprocessed and baked inulin on lipid metabolism in normo- and hypercholesterolemic rats

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Male Wistar rats were fed a bread diet containing either corn starch or 6% raw or 6% baked inulin. Furthermore, the diets were either cholesterol-free or contained 1% cholesterol and 0.1% cholic acid. Adding unprocessed or baked inulin to the cholesterol-free diets resulted in significantly lower plasma cholesterol concentrations as well as in decreased liver cholesterol concentrations, while higher daily fecal excretions of bile acids were found. The normocholesterolemic rats showed a tendency to elevated fecal excretion of neutral steroids when inulin was fed, in spite of some decrease in the coprostanol excretion. In these groups there was a significantly inverse linear relationship between liver cholesterol concentrations and daily fecal bile acid output. The results suggest that the cholesterol lowering effect of inulin in normocholesterolemic rats may be due to higher fecal steroid excretion. Moreover, these rats tended to show higher HDL LDL cholesterol ratios when they received one of the inulin containing diets. In the hypercholesterolemic groups no significant effect from inulin intake on the plasma and liver cholesterol concentrations was found. In these rats, fecal cholesterol excretion was significantly increased by 40% when baked or unprocessed inulin was added to the diet, but fecal coprostanol excretion was significantly decreased by 95%. As a consequence, consumption of inulin did not change total neutral steroid excretion in the hypercholesterolemic groups. Moreover, fecal bile acid output was not significantly affected by dietary treatment. The fact that inulin intake did not change total steroid output might explain why plasma cholesterol was not reduced in the hypercholesterolemic rats receiving inulin, in contrast to the results obtained with the normocholesterolemic rats. Also no effect from inulin consumption was found on the HDL LDL cholesterol ratio in the hypercholesterolemic animals. Including inulin in bread did not alter its effect on lipid metabolism, neither in normo- nor in hypercholesterolemic rats.