Diet-induced hyperlipoproteinemia and lipid accumulation within spontaneous arterial lesions in the rat

The extent of diet-induced lipid accumulation evaluated histologically within rat caudal artery lesions, which represent sites of spontaneous intimal injury, was studied in relation to plasma cholesterol and lipoprotein changes in two consecutive experiments: 1) Rats were fed diets enriched with various amounts of cholesterol and saturated lipids from 5 to 12 weeks of age. A large range of values of cholesterolemia was observed at the time of sacrifice, and the more the diet was enriched in cholesterol and saturated lipids, the more the mean of the arterial score, which expressed the extent of lipid deposits within caudal artery lesions, was elevated. Among the biochemical parameters studied, in decreasing order, total cholesterol, LDLchol and VLDLchol were determinant for the arterial score. 2) Rats were fed a diet containing a moderate amount of lipids and the cholesterol concentration in the 3 classical plasma lipoprotein fractions was determined at 1.5, 3 and 6.5 weeks after starting the diet. In this experiment, statistical analysis showed that the degree of lipid accumulation within caudal artery lesions correlated only with the values of VLDLchol determined early (1.5 week) after starting the diet and not with those at the time of sacrifice. However, VLDLchol values correlated with those of LDL and total plasma cholesterol. The data from these two series of experiments suggest that in diet-induced hypercholesterolemia, the intensity of lipid deposits within areas of the arterial wall where spontaneous injury had occurred was related to the values of total plasma cholesterol as reflected both by VLDLchol and LDLchol. An independant effect of one of these lipoproteins cannot be demonstrated since they are correlated with one another.