July 21/Calgary, Alberta, Canada/Obesity, Fitness & Wellness Week -- According to recent research from Calgary, Canada, "Prebiotic fibers have been proposed to promote weight loss and lower serum cholesterol; however, the mechanisms are not fully understood. The aim of the present research was to identify possible mechanisms through which prebiotic fibers improve serum lipids."

"Lean and obese JCR:La-cp rats aged eight weeks consumed one of three diets supplemented with 0, 10 or 20% prebiotic fibre for 10 weeks. Rats were anaesthetized, and a fasting blood sample was taken for lipid analysis. Real-time PCR was used to determine gene expression for cholesterol and fatty acid regulatory genes in liver tissue. Liver and caecal digesta cholesterol and TAG content were quantified.

"Both doses of prebiotic fiber lowered serum cholesterol levels by 24% in the obese hyperlipichiemic rats (P <0.05). This change was associated with an increase in caecal digesta as well as an up-regulation of genes involved in cholesterol synthesis and bile production. Additionally, there was a 42% reduction in TAG accumulation in the liver of the obese rats with 10% prebiotic diet (P <0.05); however, no change in liver fatty acid synthase (FAS).

"Prebiotic fibers appear to lower cholesterol levels through increased cholesterol excretion in the form of bile and inhibit the accumulation of TAG in the liver through a mechanism unrelated to FAS. These effects appear to be limited to the obese model and particularly the 10 % dose," wrote J.A. Parnell and colleagues, University of Calgary.

The researchers concluded, "The present work is significant, as it provides insight into the mechanisms of action for prebiotic fibers on lipid metabolism and furthers the development of dietary treatments for hypercholesterolaemia."

Parnell and colleagues published their study in British Journal of Nutrition ("Effect of Prebiotic Fiber Supplementation on Hepatic Gene Expression and Serum Lipids: A Dose-response Study in JCR:LA-cp Rats." British Journal of Nutrition, 2010;103(11):1577-1584).

For additional information, contact R.A. Reimer, University of Calgary, Faculty Kinesiology, 2500 University Dr. NW, Calgary, AB T2N 1N4, Canada.

From the August 2, 2010, Prepared Foods E-dition