Effects of Dietary Fibers on Nonfasting Plasma Lipoprotein and Apolipoprotein Levels in Rats

This study was undertaken to determine whether selected dietary fibers had an effect on plasma lipoproteins, apolipoproteins and enzymes involved in cholesterol metabolism in rats. Each experimental diet contained 8% dietary fiber by weight; all animals were killed in a nonfasted state. After 4 wk, final body weight and liver cholesterol were similar in fiber-free controls and in rats fed diets containing cellulose, pectin, oat bran or wheat bran. Pectin-fed animals has significantly lower plasma cholesterol, HDL-cholesterol and apolipoprotein A-I levels, and exhibited significantly higher hepatic 3-hydroxy-3-methylglutaryl coenzyme A reductase activity than did the fiber-free control group. In addition, plasma triglyceride concentrations were lowest in pectin-fed animals. These multiple effects on lipid metabolism were not observed when oat bran, containing one-third soluble fiber, was used. Although total plasma cholesterol levels in wheat bran-fed animals were not different from those in the fiber-free controls or the cellulose-oat bran-fed animals, the LDL cholesterol level was significantly higher than in fiber-free controls or pectin-fed animals. This study demonstrates that dietary fibers included in the diet of rats are able to alter nonfasting lipoprotein cholesterol and apolipoproteins and that pectin, a soluble fiber, was most effective in lowering plasma cholesterol levels.