Abstract-Maternal hypercholesterolemia during pregnancy is associated with enhanced fatty streak formation in human fetuses and faster progression of atherosclerosis during childhood even under normocholesterolemic conditions. A causal role of maternal hypercholesterolemia in lesion formation during fetal development has previously been established in rabbits. The same experimental model is now used to establish that maternal hypercholesterolemia or ensuing pathogenic events in fetal arteries enhance atherogenesis later in life. Five groups of rabbit mothers were fed chow, cholesterol-enriched chow, or cholesterol-enriched chow plus 1000 IU vitamin E, 3% cholestyramine, or both during pregnancy. Offspring of all groups (nϭ136) were fed a mildly hypercholesterolemic diet for up to a year and had similar cholesterol levels. Aortic lesion sizes and lipid peroxidation products in plasma and lesions in offspring were determined at birth, 6 months, or 12 months. Lesion progression in offspring of hypercholesterolemic mothers was greater than in all other groups. At each time point, offspring of hypercholesterolemic mothers had 1.5-to 3-fold larger lesions than offspring of normocholesterolemic mothers (PϽ0.01), with the greatest absolute differences at 12 months. Maternal treatment reduced lesions by 19% to 53%, compared with offspring of untreated hypercholesterolemic mothers (PϽ0.01), with the greatest effect in the vitamin E groups. At 12 months, lesions in offspring of all vitamin E and cholestyramine-treated mothers were similar to those of normocholesterolemic mothers. Lipid peroxidation end-products in lesions and plasma showed analogous differences between groups as lesions (PϽ0.01). Thus, pathogenic programming in utero increases the susceptibility to atherogenic risk factors later in life and maternal intervention with cholesterol-lowering drugs or antioxidants reduce postnatal lipid peroxidation and atherosclerosis in their offspring.

Abstract-The role of insulin resistance (IR) in atherogenesis is poorly understood, in part because of a lack of appropriate animal models. We assumed that fructose-fed LDL receptor-deficient (LDLR Ϫ/Ϫ ) mice might be a model of IR and atherosclerosis because (1) fructose feeding induces hyperinsulinemia and IR in rats; (2) a preliminary experiment showed that fructose feeding markedly increases plasma cholesterol levels in LDLR Ϫ/Ϫ mice; and (3) hypercholesterolemic LDLR Ϫ/Ϫ mice develop extensive atherosclerosis. To test whether IR could be induced in LDLR Ϫ/Ϫ mice, 3 groups of male mice were fed a fructose-rich diet (60% of total calories; nϭ16), a fat-enriched (Western) diet intended to yield the same plasma cholesterol levels (nϭ18), or regular chow (nϭ7) for approximately 5.5 months. The average cholesterol levels of both hypercholesterolemic groups were similar (849Ϯ268 versus 964Ϯ234 mg/dL) and much higher than in the chow-fed group (249Ϯ21 mg/dL). Final body weights in the Western diet group were higher (39Ϯ6.2 g) than in the fructose-(27.8Ϯ2.7 g) or chow-fed (26.7Ϯ3.8 g) groups. Contrary to expectation, IR was induced in mice fed the Western diet, but not in fructose-fed mice. The Western diet group had higher average glucose levels (187Ϯ16 versus 159Ϯ12 mg/dL) and 4.5-fold higher plasma insulin levels. Surprisingly, the non-insulin-resistant, fructose-fed mice had significantly more atherosclerosis than the insulin-resistant mice fed Western diet (11.8Ϯ2.9% versus 7.8Ϯ2.5% of aortic surface; PϽ0.01). These results suggest that (1) Key Words: arteriosclerosis Ⅲ diabetes Ⅲ fructose Ⅲ hypercholesterolemia Ⅲ lipoproteins I ndividuals with underlying insulin resistance (IR) and resulting impaired glucose tolerance (IGT) and noninsulin-dependent diabetes mellitus (NIDDM) have an increased prevalence of atherosclerosis and increased rates of coronary heart disease (CHD), 1-5 but the mechanisms responsible are poorly understood. Hyperglycemia has been hypothesized to enhance atherosclerosis in NIDDM, but the specific contribution of hyperglycemia has been difficult to demonstrate in either population studies or animal models. [5][6][7][8] Moreover, hyperglycemia per se is unlikely to play a role in the development of atherosclerosis in individuals with IGT who usually demonstrate only modest postprandial hyperglycemia. Insulin resistance is frequently associated with a number of metabolic abnormalities such as obesity, hypertriglyceridemia, low HDL, and hypertension. These risk factors explain some, but not all, of the increased risk for CHD. 9,10 Thus, additional factors associated with IR are likely to contribute to the accelerated development of atherosclerosis. Hyperinsulinemia is frequently present in both IGT and NIDDM, and several lines of evidence suggest that hyperinsulinemia itself may be proatherogenic. 11,12 For example, insulin has been shown to increase smooth muscle cell proliferation in vitro 11,13 and to enhance accumulation of cholesterol ester in aortas of rats. 14 Although several mechani...

Apolipoprotein E-deficient (apoE(-/-)) and LDL receptor-deficient (LDLR(-/-)) mice develop extensive atherosclerosis, but the occurrence of spontaneous plaque rupture and secondary thrombosis in these models has not been established. The goal of this study was to provide histological evidence of acute complications of atherosclerotic lesions in these mice and to assess their prevalence. Complications of atherosclerosis were initially studied in aortas of control mice which died during previous intervention studies. Coronary arteries and the aortic origin were then systematically assessed in serial sections through the heart of apoE(-/-) and LDLR(-/-) mice. Aortic plaque rupture and/or thrombi were seen in 3 of 82 untreated mice from past intervention studies. Screening of heart sections of 33 older apoE(-/-) mice (age 9-20 months) showed extensive atherosclerosis in one or more coronary arteries of 18 animals. In three coronary arteries, the presence of blood-filled channels within advanced atherosclerotic lesions suggested previous plaque disruption/thrombotic events followed by recanalization. In the aortic origin of the same mice, four deep plaque ruptures (or erosions reaching necrotic core areas) and a large thrombus originating from the core of a disrupted atherosclerotic lesion were observed. Although plaque ruptures/deep erosions were far less frequent than in human populations, these observations demonstrate that spontaneous plaque rupture and secondary thrombosis do occur in apoE(-/-) and LDLR(-/-) mice. These mice may therefore be suitable for studying factors contributing to thrombotic complications of atherosclerosis. However, the frequent absence of a clearly defined single fibrous cap in murine coronary lesions limits their usefulness as a model of fibrous cap rupture.

Investigations into the mechanisms by which diabetes accelerates atherosclerosis have been hampered by the lack of suitable animal models. We hypothesized that streptozotocin-treated LDL receptor-deficient mice would be a good model of diabetic atherosclerosis because streptozotocin causes diabetes in the parent C57BL/6 strain and because in these mice diet-induced hypercholesterolemia leads to the formation of advanced atherosclerotic lesions throughout the aorta. Diabetes was induced in 18 mice by intraperitoneal injection of streptozotocin. Low-dose insulin was given subcutaneously to prevent excessive mortality and extreme elevations in triglyceride levels. The control group was subjected to sham injections. Both groups were fed a diet containing .075% cholesterol for six months. Average blood glucose was higher in the diabetic group than in the control group (257 +/- 67 mg/dL versus 111 +/- 7 mg/dL, P < 0.05). Although plasma cholesterol was similar (966 +/- 399 versus 1002 +/- 180 mg/dL) in both groups, VLDL cholesterol was higher whereas LDL cholesterol was lower in the diabetic group. Immunocytochemical analysis demonstrated significantly more advanced glycation end-product (AGE) epitopes in the artery wall of the diabetic group, whereas staining for oxidation-specific epitopes was similar in both groups. Sera of diabetic mice also contained significantly more IgG autoantibodies that bound to several AGE epitopes than did sera from control mice. Despite the presence of hyperglycemia, diabetic dyslipidemia, and enhanced AGE formation in the diabetic mice, both groups had a similar extent of atherosclerosis (diabetic, 17.3 +/- 5.2; control, 16.5 +/- 6.6% of the aortic surface). These data suggest that, at least under conditions of marked hypercholesterolemia; hyperglycemia and enhanced AGE formation do not contribute significantly to atherogenesis in LDL-/- mice.