Die invloed van dieetcholesterol op serumlipiede, lewercholesterol en plasmafibrinogeen by die homosigotiese maer Zuckerrot

Abstract

The effects of dietary cholesterol in the form of egg yolk or pure cholesterol (with and without bile acid additions) on serum and liver lipids as well as plasma fibrinogen levels, were examined in homozygous lean Zucker rats against a background semi-synthetic Western diet (SSW-diet). In the literature survey (chapter 2) a review of the comprehensive literature on dietary cholesterol's effect on serum lipids indicated that the association of dietary cholesterol with serum cholesterol levels and the pathogenesis of atherosclerosis is still unclear. Recent epidemiological studies have indicated plasma fibrinogen as a major risk factor for the development of coronary heart disease (CHD). Clinical as well as experimental studies on animal models support these observations, but little is available on factors which influence plasma levels or regulate the synthesis and secretion of fibrinogen. Therefore, the effect of dietary cholesterol on plasma fibrinogen levels was examined to test the possibility that the association between dietary cholesterol and CHD may be mediated through an effect of cholesterol on plasma fibrinogen. Fifty lean Zucker rats of the same age were randomly allocated to five groups (5 males and 5 females/ group) which were fed the control and four experimental diets (egg yolk and pure cholesterol with and without bile acid additions) for 7-8 weeks. At the end of the experimental period the rats were sacrificed and serum and liver lipids , liver glycogen and plasma fibrinogen determined by standardized methods. The results showed that feeding of the experimental diets (except the egg yolk diet) resulted in significantly higher total serum cholesterol levels. All the diets significantly increased liver total lipids , cholesterol and glycogen , as well as plasma fibrinogen. The conclusion was reached that dietary cholesterol increases plasma fibrinogen levels of this rat model. The mechanism (s) are not clear, but based on recent evidence in t he literature , possible mechanism(s) are suggested. The study indicates that the association of dietary cholesterol

and CHD, in spite of a lack of association between dietary cholesterol and serum cholesterol reported in some epidemiological studies, may be explained by the observed effect of dietary cholesterol on plasma fibrinogen levels. It is recommended that before scientifically based recommendations regarding the intake of dietary cholesterol can be made , this effect of dietary cholesterol should be examined in humans . Such a study is already in progress.