Key Findings:
This study determined whether flaxseed oil (FO) exerts similar cholesterol-lowering effects as whole flaxseed (WF). The mechanism by which WF and FO modulates cholesterol levels was assessed in Ovx hamsters. WF was more effective than FO in preventing the Ovx-induced rise in total cholesterol (12% vs 4% reduction with WF and FO, respectively).
SDG isolated from flaxseed has been shown to lower cholesterol concentration in rabbits. In this study, WF and FO improved mobilization of hepatic cholesterol for bile acid synthesis through enhancing the activity of the 7a-hydroxylase enzyme. WF prevented the increase in circulating levels of cholesterol to a greater extent than FO. The cholesterol-lowering properties of other components of flaxseed such as SDG and their mechanisms of action need to be further explored.
ABSTRACT:
This study was designed to investigate whether flaxseed oil exerts hypocholesterolemic effects similar to ground whole flaxseed and to gain insight into its hypocholesterolemic mechanism. Forty-eight 6-month old female Golden Syrian hamsters were either sham-operated or ovariectomized and randomly assigned to one of four treatment groups for 90 days: Sham, Ovx, Ovx + WF, or Ovx + FO. Hamsters in the Sham and Ovx groups were fed a semipurified diet (control), whereas Ovx + WF and Ovx + FO received the same basic diet supplemented with either WF or FO (amount equivalent to the oil contribution of WF). Ovariectomy significantly increased serum total concentrations by approximately 15%. WF, but not FO, prevented the ovariectomy-induced increased serum total concentrations by approximately 15%. WF, but not FO, prevented the ovariectomy-induced increase in serum total cholesterol concentration (12% and 4% reduction by WF and FO, respectively). Hamsters fed FO or WF had high-density lipoprotein (HDL)-cholesterol concentrations similar to those of the Ovx hamsters receiving the control diet. Non-HDL-cholesterol concentrations were lowest in the WF group, albeit not statistically different from the other treatment groups. There were no significant differences among groups in serum triglyceride concentration and liver lipids. Both WF and FO more than doubled the hepatic protein levels of 7a-hydroxylase in comparison to the Ovx hamsters receiving the control diet. Our findings suggest that increased bile acid synthesis is one of the major cholesterol-lowering mechanisms of flaxseed and that other flaxseed components, aside from its oil, contribute to its hypocholesterolemic property. The cholesterol-lowering effects of other components of flaxseed and their mechanisms of action need to be further explored. Authors abstract.