Effect of Milk on Cholesterol Metabolism of Rats with Different Levels of Dietary Cholesterol

식이 Cholesterol의 수준에 따라 우유가 흰쥐의 Cholesterol 대사에 미치는 영향

The effect of milk in low and high cholesterol diet was invesigated on serum cholesterol metabolism and lipid contents of serum, aorta, liver of rats. Weanling male Sprague-Dawley rats were divided into low(0.01% w/w) and high(1.01% w/w) cholesterol-diets groups. Low cholesterol groups subdivided into four groups ; control group was given water and three milk groups were given low heat milk(LM), ultra-high heat milk(HM), and powder milk(PM), respectivily, instead of water. High cholesterol groups were consisted of three groups ; control, LM, and HM groups. After feeding these experimental diets for six weeks, lipid levels were measured in serum and tissure and dried feces were analyzed for neutral and acidic sterols. Results obtained from this study are as follows : 1) Nutrient intakes, body weight gains and aorta weights did not differ among groups, but liver weights were higher in high cholesterol fed rats than low cholesterol fed rats. 2) Serum protein contents were increased independently by intakes of high cholesterol and milk. 3) Serum total cholesterol and triglyceride levels were increased but phospholipid levels and HDL-cholesterol/total-cholesterol ratios were decreased by high cholesterol in diet. And milk supplementation decreased serum total cholesterol and triglyceride levels but increased phospholipid levels and HDL-cholesterol/total-cholesterol ratios. 4) Contents of cholesterol and triglyceride in aorta and liver were elevated by dietary high cholesterol and lowered by consumption of all three types of milk. 5) Levels of cholesterol and triglyceride among serum, aorta and liver were highly correlated (r=0.7-0.9, p<0.001). 6) Fecal excretion of total sterols was three times high in high cholesterol group, compared with low cholesterol groups and were increased about 20% by milk consumption. 7) The effects of milk were more pronouncely shown in low cholesterol groups and mostly confined to LM and HM groups, rarely shown in PM group. It is concluded from the present study that milk had the hypolipidemic as well as hypocholes terolemic effect, which appears to be mediated through increased fecal bile acid excretion. But the effect is likely to be shaded by excess consumption of dietary cholesterol and was almost absent in powder milk.