The absorption of cholesterol and of cholesterol oxidation products (oxidized cholesterols) was compared in lymph-cannulated rats. We found that the lymphatic absorption of an intragastrically administered, emulsified lipid meal containing 25 mg of cholesterol or 25 mg of oxidized cholesterols, within 24 h, was approximately 67 and 30%, respectively. The absorption rate of individual oxidized cholesterols differed considerably and was approximately 30% for 7 alpha-hydroxycholesterol, 42% for 7 beta-hydroxycholesterol, 32% for 5 beta-epoxycholesterol, 28% for 5 alpha-epoxycholesterol, 15% for cholestanetriol and 12% for 7-ketocholesterol. Moreover, cholesterol oxidation products delayed the absorption of oleic acid as triolein. Approximately 35 and 48% of cholesterol was recovered in chylomicrons (CM) and very low density lipoprotein (VLDL), respectively. In contrast, 54 and 40% of the oxidized cholesterols was recovered in CM and VLDL, respectively, although there was a significant difference in the distribution of individual oxidized cholesterols. The results of the present study indicate that oxidized cholesterols are absorbed to a lesser extent than is cholesterol, that they disturb fat absorption and that they distribute differently between lymphatic lipoproteins.

No abstract

Oxidation of pure cholesterol during heating in an air oven at high temperature was studied. Cholesterol was virtually stable during heating at 100 OC for 24 h but was unstable at temperatures above 120 OC. In the heated cholesterol preparations, a number of oxidized derivatives were detected by a combination of thin-layer chromatography and capillary gas chromatography-mass spectrometry. Major oxidized sterols were 7a-hydroxycho1estero1, 7,3-hydroxycholestero1, 5a-epoxycho1estero1, 5,3-epoxycholesterol, cholestanetriol, and 7-ketocholesterol. Various oxidized cholesterol derivatives were produced during heating above 120 "C within a relatively short time (1 h). The composition of the oxidized products differed depending on temperature and time of heating. When cholesterol was heated at 150 OC, the production of oxidized cholesterol was maximum, and 7-ketocholesterol was the most predominant oxidized product. Heating a t 120 OC also produced oxidized cholesterol to some extent, whereas only marginal amounts of oxidized cholesterols were produced a t 100 "C and at 200 "C cholesterol was almost decomposed in a short time.

The dose-dependent hypocholesterolemic and antiatherogenic effects of dietary apple polyphenol (AP) from unripe apple, which contains approximately 85% catechin oligomers (procyanidins), were examined in male Sprague-Dawley rats (4 wk of age) given a purified diet containing 0.5% cholesterol. Dietary AP at 0.5 and 1.0% levels significantly decreased the liver cholesterol level compared with that in the control (AP-free diet-fed) group. Dietary AP also significantly lowered the serum cholesterol level compared with that in the control group. However, the HDL cholesterol level was significantly higher in the 1.0% AP-fed group than in the control group. Accordingly, the ratio of HDL-cholesterol/total cholesterol was significantly higher in the 0.5% AP-fed group and 1.0% AP-fed group than in the control group. Moreover, the atherogenic indices in the 0.5 and 1.0% AP-fed groups were significantly lower than those in the control group. The activity of hepatic cholesterol 7alpha-hydroxylase tended to be increased by dietary AP in a dose-dependent manner. In accord with this observation, dietary AP increased the excretion of acidic steroids in feces. Dietary AP also significantly promoted the fecal excretion of neutral steroids in a dose-dependent manner. These observations suggest that dietary AP at a 0.5 or 1.0% level exerts hypocholesterolemic and antiatherogenic effects through the promotion of cholesterol catabolism and inhibition of intestinal absorption of cholesterol.

We examined the effects of intake of Korean foxtail millet protein (FMP) on plasma levels of lipid, glucose, insulin, and adiponectin in genetically type 2 diabetic KK-A y mice. When mice were fed a normal FMP diet or a high-fat-high-sucrose diet containing FMP for 3 weeks, in both experiments plasma concentrations of high-density lipoprotein cholesterol (HDL-cholesterol) and adiponectin increased remarkably in comparison with a casein diet group, whereas concentrations of insulin decreased greatly and that of plasma glucose was comparable to that in the casein diet group. Considering the role of adiponectin, insulin, and HDL-cholesterol in diabetes, atherosclerosis, and obesity, it appears likely that FMP may improve insulin sensitivity and cholesterol metabolism through an increase in adiponectin concentration. Therefore, FMP would serve as another beneficial food component in obesity-related diseases such as type 2 diabetes and cardiovascular diseases.