Polyactose and Bile Acid Excretion in Rats

Abstract

In America, cardiovascular disease is the leading cause of death in adults. In addition, people with hyperlipidemia, or high lipid concentration in the blood - including cholesterol, are twice as likely to develop CVD as people without hyperlipidemia. Statins are a class of medications that reduce total cholesterol levels and reduce risks of CVD (1). However, statins can have serious side effects such as: muscle pain, liver damage, increase in blood glucose levels, and memory loss of confusion. In rare cases, statins may induce rhabdomyolysis, which can cause severe muscle pain, liver damage, kidney failure and death (2). Thus, there is continued interest in non-pharmacological approaches to lowering blood cholesterol concentrations. Prebiotics, a type of dietary fiber that is indigestible by mammals, may be another way to reduce cholesterol without the adverse effects of statins or other medications. Prebiotics are defined to produce a positive change in the microflora of an organism and are beneficial to the host (3). This project aims to study polylactose, a newly synthesized oligosaccharide that has a potential to be a prebiotic. A recently conducted study in rats, using a high-fat diet as a background diet, found that feeding polylactose lowered liver cholesterol concentration. The mechanism by which polylactose imparts this effect is unknown. The purpose of this project was to examine one potential mechanism by which polylactose may lower liver cholesterol in rats, specifically, whether polylactose increases bile acid excretion. As bile acids are synthesized from cholesterol, and an increased loss of bile acids has the potential to lower cholesterol by diverting it into bile acid synthesis. Results of this project indicate that the high fat polylactose fed rats indeed showed lower liver cholesterol levels, indicating that polylactose has a potential to be a dietary cholesterol-lowering agent. However, the polylactose diet fed group did not result in increased bile acid excretion. This suggests that polylactose lowers liver cholesterol by a mechanism different from the study objective - excreting bile acids. Therefore, further studies should be conducted to determine the mechanism by which polylactose acts as a dietary cholesterol-lowering agent in rats.