Spontaneous aortic lesions in wild adult Malaysian long-tailed monkeys (Macaca irus)

Age-related changes of elements in the coronary arteries of monkeys in comparison with those of humans

To elucidate compositional changes of the coronary artery with aging, the authors investigated age-related changes of elements in the coronary arteries of rhesus and Japanese monkeys by direct chemical analysis in comparison with the coronary arteries of Japanese and Thai. Used monkeys consisted of 38 rhesus monkeys and 23 Japanese monkeys, ranging in age from newborn to 33 years. After perfusion with a fixative, the hearts were resected from the monkeys, and the anterior interventricular branches of the left coronary artery and the right coronary arteries were resected from the hearts. After ashing of the arteries, element contents were determined by inductively coupled plasma-atomic emission spectrometry. It was found that the Ca and P contents did not increase in both the left and right coronary arteries of rhesus and Japanese monkeys at old age. The average contents of Ca and P decreased by 13% and 25% in the left coronary arteries more than 20 years of age in comparison with those below 20 years of age, whereas they decreased by 4% and 15% in the right coronary arteries more than 20 years of age in comparison with those below 20 years of age. This finding indicated that atherosclerosis scarcely occurred in both the left and right coronary arteries of rhesus and Japanese monkeys at old age. In contrast with monkeys, atherosclerosis occurred frequently in the coronary arteries of Japanese and Thai at old age.

Humans, lipids and evolution

The genetically ordered physiology of contemporary humans was selected over eons of evolutionary experience for a nutritional pattern affording much less fat, particularly less saturated fat. Current dietary recommendations do not accord exactly with those generated by an understanding of prior hominoid/hominid evolution. Similarly, widely advocated standards for serum cholesterol values fail to match those observed in recently studied hunter-gatherers, whose experience represents the closest living approximation of "natural" human lipid metabolism. The evolutionary paradigm suggests that fats should comprise 20-25% of total energy intake, that the ratio of polyunsaturated to saturated fat should exceed 1.0, and that total serum cholesterol levels should be below 150 mg/dL (approximately 4 mM/L).

Atherosclerosis research in cynomolgus monkeys (Macaca fascicularis)

This is a review of the utilization of cynomolgus monkeys (Macaca fascicularis) in atherosclerosis research. Naturally occurring and experimentally induced atherosclerosis progression and regression studies are described. This species has been utilized as an animal model to study the effects of immunologic injury, aging, exercise, and drug intervention on atherosclerotic lesions. Cynomolgus macaque atherosclerosis induced by feeding cholesterol is a good model of human atherosclerosis because of similar gender-related differences in susceptibility to coronary artery atherosclerosis, a relatively high incidence of myocardial infarction, and characterized psychosocial factors that influence the development of atherosclerosis.

Nonhuman primate models of atherosclerosis: potential for the study of diabetes mellitus and hyperinsulinemia

Nonhuman primates have been used for many years to investigate the pathogenesis and progression of atherosclerosis. The use of these animal models has resulted in a better understanding of the risk factors associated with atherosclerosis. Nonhuman primates that have consumed an atherogenic diet for several years develop lesions that are comparable to those found in human beings. Diabetes, both spontaneous and chemically induced, has been described in a number of nonhuman primate species. These diabetic models may be used to understand the accelerated progression and vascular complications of atherosclerosis in diabetic human beings.

Ultrastructure of experimental coronary artery atherosclerosis in cynomolgus macaques. A comparison with the lesions of other primates

We studied the ultrastructure of the left anterior descending coronary artery in 6 female cynomolgus macaques fed atherogenic food containing 0.5% cholesterol for 6 months, and in 2 female cynomolgus macaques that had received food low in cholesterol. Animals given the atherogenic food had coronary artery lesions of a characteristic two-level architecture consisting of a lipid-poor upper cap, and of a lipid-rich lower core. The cap consisted of layers of smooth muscle cells that were rich in rough endoplasmic reticulum and contained few myofilaments and relatively few lipid droplet inclusions. The core consisted mainly of macrophages overloaded with droplet inclusions (macrophage foam cells), droplet-laden smooth muscle cells, and extracellular lipid and cell debris. Some macrophage foam cells were in mitosis. The largest lipid cores contained multinucleate giant cells with large intracellular crystal clefts. Dead macrophage foam cells were the source of the extracellular lipid and debris particles. Intimal cores often extended into the adjacent media. The adventitia was involved in the intima-media lesions in 3 of the animals. Compared with the coronary artery lesions of rhesus macaques and patas monkeys given similar atherogenic diets, cynomolgus monkey lesions were morphologically closer to human atherosclerotic plaques with respect to their stratification into a cap and a core.

Histology of normal aortas in non-human primates with emphasis on diffuse intimal thickening (DIT)

Little information is available on the histology of the normal aorta in non-human primates, despite their extensive use in atherosclerosis research. This paper consists of a detailed histologic description of normal aortas from 28 non-human primates, including 20 species. Medial and adventitial coats were essentially normal in all animals, and the former were composed of lamellar units similar in structure to those described in detail by other investigators. Intimal thickenings were present in 24 of the 28 individuals. These thickenings were similar in morphology to those of diffuse intimal thickening (DIT) in humans and other animals, and were more prevalent in older animals and in larger animals. The thickenings were not more prevalent or more pronounced in any particular region of the aorta, and their distribution did not provide a clue as to their etiology. Findings suggested that the thickenings underwent recognizable states of growth and maturation, and that growth was accomplished by the addition of smooth muscle cells at the intimomedial junction.

Diet-induced aortic atherosclerosis in Malaysian long-tailed monkeys (Macaca irus)

Moderate hypercholesterolaemia has been produced in eight adult male M. irus monkeys by feeding an egg-toast preparation containing butter and 0.14 per cent. total cholesterol. At autopsy, after two to four years of persistent hypercholesterolaemia, there was massive fatty streaking of the aorta involving 21 to 78 per cent. of the intimal surface. The distribution and morphology of the fatty streaks was similar to that in man. In addition, there were fibrous plaques including "soft" lipid-rich atherosclerotic plaques identical to their human counterpart. There was no grossly detectable thromobosis, haemorrhage or ulceration. Atherosclerotic lesions were also present in the coronary, carotid, subclavian, iliac and femoral arteries. In a control group of monkeys fed a low-fat, cholesterol-free diet, arterial lesions were identical in type and extent to those in freshly captured wild monkeys.