Effect of dietary protein and cholesterol on atherosclerosis in swine

Two groups of pigs, each consisting of six animals, were fed on isocaloric amounts of experimental diet with a high cholesterol content but no added fat and with varying levels of protein (5% vs 25% by weight of the diet) for 16 mo.Animals of the low-protein group were confirmed to have developed a protein-deficiency state by the characteristic microscopic changes in the viscera and hypoproteinemia due to reduced albumin fraction. They had a larger surface area of the aorta involved with atherosclerosis, and the lesions had a higher lipid and cholesterol and lower phospholipid content. The serum cholesterol was significantly higher, and the serum cholesterol esters contained larger proportion of oleic acid at the expense of linoleic acid than the animals of the high protein group.The results indicate that very low levels of dietary protein have a promotive effect on the induction of hypercholesterolemia and atherosclerotic lesions in the presence of cholesterol alone and in the absence of additional fats. The precise mechanism of this variation is not understood.