Reduced atherogenesis in cholesterol-fed diabetic rabbits. Giant lipoproteins do not enter the arterial wall.

In cholesterol-fed rabbits, alloxan-diabetes has an anti-atherogenic effect, which is associated with severe elevation of plasma triglyceride concentrations. To study this effect, we measured lipoprotein sizes and aortic permeability coefficients for cholesteryl ester and for albumin in hypertriglyceridemic diabetic cholesterol-fed rabbits and in normotriglyceridemic cholesterol-fed rabbits. With the same high cholesterol concentration in plasma, hypertriglyceridemic diabetic rabbits had 70% of plasma cholesterol in very large lipoproteins (diameter greater than 75 nm), whereas normotriglyceridemic rabbits had only about 10% of plasma cholesterol in these giant lipoproteins. The aortic permeability coefficients for cholesteryl ester in hypertriglyceridemic diabetic cholesterol-fed rabbits was only 10% to 50% of that in normotriglyceridemic cholesterol-fed rabbits. Aortic permeability coefficients for albumin did not differ significantly between the hypertriglyceridemic and normotriglyceridemic rabbits. The results suggest that the large size of a major fraction of plasma lipoproteins in the hypertriglyceridemic diabetic cholesterol-fed rabbits is responsible for the relatively low aortic permeability coefficient for cholesteryl ester from plasma and hence for reduced atherogenesis in these animals.