Emory D. Warner

Regression of Coronary Atheromatosis in Rhesus Monkeys

Rhesus monkeys subjected to the atherogenic stimulus of a high-fat, high-cholesterol diet showed significant coronary atheromatosis at the end of 17 months. Smaller fibrotic lesions with scant stainable lipid were found in animals that were subsequently fed either of two cholesterol-free diets for 40 months. The average cross-sectional area of the lumen was more than 80% greater in regression animals than in monkeys with baseline atherosclerosis. The data support the hypothesis that uncomplicated coronary atheromas may regress in primates in appropriate dietary settings.

MASSIVE THROMBOSIS PRODUCED BY FATTY ACID INFUSION

Previous investigations have shown that fatty acids affect the coagulation of blood (2-4). In particular, certain fatty acids greatly accelerated the formation of thrombi from rat or human blood in the Chandler apparatus 1 (6, 7). Long-chain, saturated fatty acids, such as stearic and palmitic, shortened the time of thrombus formation, whereas the unsaturated fatty acids of similar chain length (oleic, linoleic, linolenic, and arachidonic) did not influence the thrombus formation time. Shortchain, saturated fatty acids of chain length less than C12 were likewise without effect. The mechanism whereby thrombus formation was accelerated by long-chain, saturated fatty acids probably resulted from the activation of the Hageman or contact factor of plasma (7). These observations relating fatty acids to thrombus formation in vitro have prompted additional investigations designed to test the effects of different fatty acids given intravenously to anesthetized dogs. Many previous workers have infused fatty acids (or their sodium salts) into animals. As early as 1889, Munk had noted that dogs developed hypotension and asystole after the intravenous injection of oleate or palmitate (8). Others have documented that fatty acids or their sodium salts, when given to animals intravenously, produced hemolysis (9, 10), capillary damage (11), and death (10-13). In none of these re-

Platelets, Fatty Acids and Thrombosis

The sodium salts of stearic, oleic, linoleic and linolenic acids were added to human washed platelet suspensions and platelet-rich citrated plasma. Aggregation of the platelets was measured microscopically and with a turbidimetric method. All of the fatty acids had the ability to produce aggregation when added to washed platelets, but stearic acid, a long-chain saturated fatty acid, was more potent than were the unsaturated acids when added to platelet-rich plasma. Aggregation of platelets by fatty acids required the presence of calcium ions and the aggregation was irreversible. The addition of albumin diminished the aggregating effects of fatty acids, but microscopic aggregates still formed in most instances. Subnormal aggregation was noted when sodium stearate was added to platelet-rich plasma from a patient with a severe deficiency of factor XII (Hageman factor). Thus, fatty acids are now known to have two potential thrombogenic effects: platelet aggregation and the activation of clotting factors involved in the early stages of blood coagulation.

Utilization of long-chain free fatty acids by human platelets

There was a rapid net uptake of free fatty acid (FFA) by human platelets when long-chain FFA, bound to human serum albumin, were incubated with platelet suspensions. Results from experiments in which both palmitate and albumin were labeled indicated that the fatty acid dissociated from the protein during uptake. Much of the FFA taken up by the platelet in short-term incubations remained in unesterified form, i.e., it was recovered as platelet FFA. As the incubation continued, increasing amounts of FFA were oxidized to CO(2) and incorporated into platelet lipid esters, particularly lecithin. Essentially all of the fatty acid that was incorporated into the platelet FFA fraction was released rapidly from the cells when they were exposed to a medium containing FFA-free albumin. The magnitude of uptake into the platelet FFA fraction was similiar at 0 degrees and 37 degrees C. Likewise, the rate and magnitude of FFA release from the platelet were similar at 0 degrees and 37 degrees C. Therefore, it is likely that both FFA uptake and FFA release occur by energy-independent mechanisms. The major effect of increasing the FFA concentration of the incubation medium was increased fatty acid uptake into the platelet FFA fraction. Similar results occurred when platelets were incubated in human plasma containing increasing amounts of added palmitate. At a given extracellular FFA concentration, considerably more of the saturated fatty acids, palmitate and stearate, were taken up as platelet FFA than either oleate or linoleate.

Toxic effects of glucagon-induced acute lipid mobilization in geese

The toxic effects associated with rapid lipid mobilization and a high plasma free fatty acid (FFA) concentration produced by glucagon were evaluated. Glucagon (0.5 mg/kg of body wt) was injected intravenously into nonfasting geese. The geese developed rapid respirations and high plasma FFA levels within 15 min after the glucagon injection; three of eleven died. Control geese, injected with saline, did not exhibit toxic signs. Peak FFA concentrations developed 15 min after glucagon and high levels persisted for over 90 min. Geese injected with glucagon frequently developed electrocardiographic abnormalities that included supraventricular tachycardia, premature ventricular contractions, and signs of myocardial ischemia. Light and electron microscopy revealed acute myocardial degeneration and fatty infiltration of the liver. The increase in plasma FFA concentrations and toxic effects were not prevented by pretreatment with nicotinic acid or propranolol.

Intimal Thickening in Normochoiesterolemic Rhesus Monkeys Fed Low Supplements of Dietary Cholesterol

Rhesus monkeys were fed a high-fat diet containing either 0, 43, or 129 μg/kcal of cholesterol for 18 months. In the monkeys on the cholesterol-supplemented diets, changes in plasma cholesterol remained within the range found in monkeys fed the cholesterol-free diet. Monkeys on the cholesterol-supplemented diets were compared with monkeys given no dietary cholesterol with range-matched plasma cholesterol; intimal thickness of the aorta and branch arteries, distribution of lipoprotein cholesterol, and tissue content of cholesterol in aorta and liver were considered. The monkeys on the cholesterol-supplemented diets showed intimal thickening with more sudanophilia and increased aortic cholesterol, a decrease in plasma high-density lipoprotein cholesterol, and an increase in low-density lipoprotein cholesterol, and the monkeys fed the higher amount of dietary cholesterol showed an increase in hepatic cholesterol. No null point for the effect of dietary cholesterol on arterial intima was found even at an intake level far below that conventionally used for the induction of experimental atherosclerosis in the nonhuman primate. The intimal changes found in response to very low cholesterol intake imply that subtle qualitative alterations in lipoproteins are of critical importance to our understanding of lesion induction.

The Coagulant and Thrombogenic Properties of Human Atheroma

Suspensions of gruel from severely atherosclerotic human aortas and coronary arteries were tested in several coagulation systems. The atheromatous material shortened the clotting time of normal whole blood and plasma and accelerated thrombus formation time in the Chandler apparatus. Normal human platelets in platelet-rich plasma were aggregated by the atheromatous gruel. Aggregation did not occur when the gruel was added to platelet-rich plasma from a patient with a severe factor XII (Hageman) deficiency. The intravenous injection of atheromatous plaque suspensions into rats caused thrombocytopenia, shortening of the whole blood clotting time, and thrombosis. Coagulation of blood from patients with classical hemophilia, with Hageman factor deficiency, and with coumarin-induced anticoagulant effect was accelerated by the addition of the atheromatous gruel. Blood from patients given heparin, however, largely retained its anticoagulant activity. Atheromatous material from both aortic and coronary arteries be...

THE RELATION OF HYPERCHOLESTEROLEMIC FATTY STREAKS TO INTIMAL PERMEABILITY CHANGES SHOWN BY EVANS BLUE

The aortic localization of diet-induced fatty streaks in relation to focal increases in intimal permeability was evaluated in cynomoglus monkeys. Animals fed a hypercholesterolemic diet and studied at 10, 15, and 100 days had increasing intensity of Evans blue dye uptake. The overlap of fatty streaks with areas of dye intake increased as the areas of dye uptake enlarged, but all hypercholesterolemic groups showed some fatty streaks not topographically related to areas of dye uptake or flow instability. Because the upper thoracic aorta tended to show more advanced fatty streak formation dissociated from evident permeability change or hydraulic instability, it is suggested that mechanical factors associated with the geometric configuration of the descending thoracic aorta may have a significant role in the localization of some hypercholesterolemic fatty streaks.

The antithrombotic properties of coumarin drugs.

Excerpt INTRODUCTION In recent years, coumarin drugs have played an important role in the treatment of thrombo-embolic disease. Despite the widespread use of these drugs, the exact mechanism by whi...

Dietary disaccharides in experimental atherosclerosis in rhesus monkeys

Abstract Rhesus monkeys were given atherogenic diets whose carbohydrate content was starch alone or with sucrose and lactose partially substituted. Study 1 retrospectively compared starch 44% versus the combination starch 15%, sucrose 10%, and lactose 15% fed for 17 months. Without greater hypercholesterolemia, the sugar-fed monkeys. had more fibrous connective tissue, extracellular lipid, and mineralization. Study 2 compared starch 47% and the combination starch 22% and sucrose 25% fed for 9 weeks. Intergroup plasma lipids were similar but aortic lesions differed: After starch there were more lipid-filled cells; after sucrose, more myointimal cells were seen. In Study 3 the diet combinations of Study 2 and the additional combination starch 22% and lactose 25% were fed for 18 weeks. Hypercholesterolemia occurred in the order lactose > sucrose > starch. In aorta greater foam cell accrual obscured regimen distinctions; in iliac arteries lesions of starch and sucrose groups were readily distinguished; those of the lactose group had intermediate characteristics. Differences in carbohydrate formulation in diet-induced experimental atherosclerosis evoke lesion differences in early atherogenesis that are not attributable to differences in hyperlipidemia; the data further suggest that dietary disaccharides may cause more advanced late lesions than dietary starch.