Effect of bran and cellulose on lipid metabolism in obese female Zucker rats.

The effects on lipid metabolism of bran and cellulose added to a low-cholesterol purified diet were studied in female obese Zucker rats. The obese Zucker rat was chosen for the experiment because of its sensitivity to dietary changes with regard to lipid metabolism. Cellulos, as well as bran, had an effect on lipid metabolism, which is expressed as an increase in the excretion of fecal bile acid and cholesterol and, in the case of bran feeding, as a decrease in liver cholesterol level and an increase of fecal fat excretion. The increased excretion rate of cholesterol and bile acids did not result in a reduction of the plasma cholesterol levels, which suggests a compensatory mechanism in the form of either an increase of hepatic cholesterol synthesis and/or changes within the body cholesterol pools. The increased excretion of fecal fat that occurred when bran was added to the diet, is not likely to influence cholesterol metabolism, since fecal fat excretion only appeared to form a small percentage of the total fat intake. Bran as well as cellulose caused a significant increase in fecal wet weight and a decrease in transit time. Though both cellulose and bran are capable of binding bile acid, cholesterol and/or fat, the intestinal transit time and the fecal bulk might also be a cause of increased steroid excretion. The fact that our results are inconsistent with those of some investigations described in the literature but in agreement with the findings of other workers, again stresses the primary need for a better chemical characterization of the various fiber sources.