Experimental atherosclerosis in hypercholesterolemic mini-pigs. Regression of cholesterol ester accumulation in aorta and coronary arteries after treatment with clofibrate, beta-pyridylcarbinol or a normo-lipidemic diet

Macroscopic distribution of coronary atherosclerotic lesions in cholesterol-fed rabbits

In the present study we macroscopically examined a change in the distribution of coronary atherosclerosis in cholesterol-fed rabbits. Rabbits were fed a cholesterol-enriched diet for 15 weeks, then replaced by a normal diet, and were sacrificed at 15, 24, 32 and 42 weeks after the start of the experiment. The coronary atherosclerosis in the cholesterol-fed rabbits was distributed more densely in the proximal portion than in the middle and distal portions, and the lesions were severe at 24 and 32 weeks after the start of the experiment. comparison of lesions in the three portions at these time points showed that the percentages of lesion areas in the proximal portion, the middle portion and the distal portion were approximately 51%, 21 to 25% and 0.2 to 3.7%, respectively. Macroscopic observation of the coronary atherosclerotic lesions showed that the lesions formed over the vessel lumen in the proximal portion within the range of approximately 5 mm from the orifice of the left coronary artery. In the middle portion, the lesions formed predominantly around the orifices of branches as small patchy lesions from 1 to 3 mm in diameter. These findings support previous histopathological reports that suggested that the incidence of stenosis in the proximal portion was high, and the incidence of lesion occurrence in the middle and the distal portions varied. The method, macroscopical investigation of the coronary artery, is useful for analyzing coronary atherosclerosis in the rabbit.

Inhibition of acyl-CoA cholesterol O-acyltransferase reduces the cholesteryl ester enrichment of atherosclerotic lesions in the Yucatan micropig

Atherosclerotic lesion development may be altered indirectly by regulating plasma cholesterol or directly by inhibition of acyl-CoA cholesterol O-acyltransferase (ACAT) within cells of the artery. Yucatan micropigs were meal-fed a 2% cholesterol, 8% peanut oil, 8% coconut oil purified diet for 1 month prior to administration of the potent, bioavailable ACAT inhibitor CI-976, and induction of atherosclerotic lesions by chronic endothelial damage. After 84-108 days of therapy, CI-976 decreased mean plasma VLDL-cholesterol 85-91% and cumulative VLDL-exposure (area under VLDL-time curve) by 65%. However, overall plasma total, LDL and HDL cholesterol and triglyceride levels were unchanged. CI-976 decreased liver cholesteryl ester (CE) content 65% without significantly affecting adrenal CE content. The CE content of the injured left femoral, left iliac and abdominal aorta and uninjured right femoral and iliac arteries and thoracic aorta was reduced 62-78% by CI-976. Systemic plasma CI-976 levels measured 24 h post-dose ranged from 2.26 to 4.05 micrograms/ml and significantly correlated with the reduction in both VLDL and vessel CE content. Thus, we conclude that inhibition of ACAT can blunt the cholesteryl ester enrichment of developing atherosclerotic lesions by preventing reesterification and storage of lipoprotein cholesterol within vascular cells and by reducing the plasma level and delivery to the arterial wall of such atherogenic lipoproteins as VLDL.

The influence of atenolol and prazosin on serum lipids and atherosclerosis in minipigs fed a hyperlipidemic diet

1. The effect of the adrenergic blockers prazosin and atenolol were tested in hypercholesterolemic Göttingen minipigs. 2. After 1 yr there was a significant reduction of plasma triglycerides and total cholesterol in the medicated animals as compared to untreated ones. 3. No significant difference in atherosclerotic lesions was observed.

Influence of clofibrate on the plasma lipoprotein pattern and on the lipid content and protein and collagen synthesis in atherosclerotic coronary arteries and abdominal aorta from hypercholesterolemic mini-pigs

The influence of clofibrate on the plasma lipoprotein pattern in hyperlipidemic mini-pigs was studied and an attempt was made to characterize the type of atherosclerosis produced in this animal model. Thirty-two female mini-pigs of the Göttingen strain were used. Experimental hypercholesterolemia and atherosclerosis were produced in 16 of the animals by adding 11.2% egg yolk and 0.5% cholesterol to the diet for 14 months. In groups of 8 normolipidemic and 8 hyperlipidemic animals clofibrate was added in a dose of 2 g per animal and day. The remaining 8 animals of each category served as controls. Two months of clofibrate treatment normalized the plasma cholesterol in the hyperlipidemic group mainly by reducing the elevated LDL-cholesterol fraction. In normolipidemic animals clofibrate significantly reduced the HDL-cholesterol. At the end of the treatment period the animals were slaughtered and autopsied. The right coronary artery and normal and atherosclerotic pieces of the abdominal aorta were taken for biochemical analysis. There was a marked accumulation of free and esterified cholesterol in the right coronary artery from hyperlipidemic animals. Clofibrate treatment significantly reduced the content of esterified cholesterol in this vessel. Atherosclerotic pieces from the abdominal aorta were also rich in free and esterified cholesterol and showed a higher rate of proline and hydroxyproline incorporation than the adjacent normal tissue. The contents of proline and hydroxyproline were relatively unchanged, however, suggesting that there may be an increased turnover of protein and collagen synthesis rather than an increased total protein and collagen production.(ABSTRACT TRUNCATED AT 250 WORDS)

Antihyperlipidemic properties of beta-pyridylcarbinol. A review of preclinical studies

The available preclinical literature on the antihyperlipidemic properties of beta-pyridylcarbinol is reviewed. Similarities between the pharmacological profiles for beta-pyridylcarbinol and nicotinic acid, and evidence for the metabolic conversion of beta-pyridylcarbinol to nicotinic acid are discussed. Several reviews discussing the antihyperlipidemic effects of beta-pyridylcarbinol (beta-PC, nicotinyl alcohol, Roniacol) and nicotinic acid (NA) have appeared during the last 15 years (1-6). However, continuing clinical interest in the ability of nicotinic acid analogs to reduce plasma lipids indicated that an update and critical evaluation of the preclinical literature on this subject would be of value in order to permit a more complete assessment of the relevance of several animal models to effects in human subjects. The literature reviewed included (a) preclinical studies of beta-PC where it was the sole compound examined; (b) comparative studies of beta-PC and NA; and (c) studies relating to the metabolism of beta-PC. The literature chosen included experiments involving fasted animals, satiated animals, and effects of Triton-induced hyperlipidemia. Data on other pharmacological properties of beta-PC and/or NA that might contribute to antihyperlipidemic efficacy (e.g., fibrinolysis, inhibition of platelet aggregation, erythrocyte membrane changes) were also included where available.

Sudden death related to advanced coronary atherosclerosis in mini-pigs: influence of some drugs

Advanced coronary atherosclerosis was produced in 30 mini-pigs by a combination of a hypercholesterolaemic diet and X-irradiation to the precordial region. Within 11-25 weeks after the irradiation, 13 of the 30 animals died a sudden death probably caused by coronary atherosclerosis. The contents of free and ester-bound cholesterol in the right coronary artery were significantly higher in the animals which died spontaneously than in surviving animals. In an untreated group of 12 animals 7 died whereas in a group treated with beta-pyridylcarbinol only 1 out of 5 died. In the coronary arteries, the contents of both free and ester-bound cholesterol were significantly lower in the beta-pyridylcarbinol-treated animals. In a sulfinpyrazone-treated group 3 out of 8, and in a metoprolol-treated group 2 out of 5 animals died. None of these drugs reduced the accumulation of cholesterol in the coronary arteries. The rate of sudden death was 26 +/- 6% (P less than 0.05) lower in the combined group of treated animals than in the untreated ones. By regular ECG recordings, signs which could predict the fatal outcome of the experiment were looked for. Although depressed ST segments were present before death in a few animals, this was not a regular phenomenon. It is concluded that advanced coronary atherosclerosis in mini-pigs often leads to sudden death and that this animal model seems suitable for testing the potential therapeutic effects of drugs.