MODIFICATION OF CHOLESTEROL METABOLISM IN RATS BY DIETARY FIBER

MICHAEL JAMES KELLEY, Purdue University

Abstract

These studies were designed to better understand the mechanism(s) by which dietary fiber may affect cholesterol metabolism. Particular attention was focused on oat products as sources of dietary fiber. In the first two experiments, rats were fed a high sucrose diet with or without 0.25% cholesterol (CHL) and containing no fiber, alfalfa, cellulose, oat bran, or whole oats. Only alfalfa and oat bran prevented the accumulation of liver CHL in the CHL fed groups while alfalfa only raised HMG-CoA reductase (HMGR) activity. Alfalfa, cellulose, and whole oats, as well as dietary CHL, increased neutral and acidic steroid excretion with oat fed rats having the highest level. In other experiments, plasma insulin was elevated following meal feeding but only the total activity of HMGR (R(,T)) was affected by the meal while the expressed activity (R(,A)) and R(,A)/R(,T) were not. The R(,T) increased following the meal but addition of dietary CHL negated this response and oat bran seemed to depress it. In rats fed either a commercial diet or semipurified diet under ad libitum or meal feeding conditions, only R(,T) had a significant diet-feeding interaction with rats fed the commercial diet having higher values. Finally, the parameters of sterol balance were affected by the inclusion of oat bran, oat gum, or oat bran minus gum in the diet. Oat bran fed rats had lower neutral steroid output but higher endogenous neutral steroid loss than other groups. Cholesterol absorption was increased while synthesis was decreased in the oat bran, oat gum, and oat bran minus gum groups. Oat products were found to decrease liver CHL accumulation, increase neutral and acidic steroid excretion, and lower the R(,T) component of HMGR. It may be the combination of the latter two effects which is, in part, responsible for the changes in CHL levels in rats.

Degree

Ph.D.

Subject Area

Nutrition

COinS