Influence of atherosclerosis on the composition, synthesis, and esterification of lipids in aortas of squirrel monkeys (Saimiri sciureus)

The composition and synthesis of lipids from aortas of squirrel monkeys were studied following perfusion with [1-¹⁴C]acetate or [2-¹⁴C]mevalonate. Twenty-nine cholesterol-fed and 6 control monkeys were used. After 1 year on diet, the cholesterol-fed group had only slightly more aortic atherosclerosis than controls. In both groups fatty streaks and raised plaques were seen.

Fatty acid composition of phospholipids and triglycerides was similar in both groups. Substantial differences were noted in the cholesteryl esters; the principal change was an increase in cholesteryl oleate in aortas from cholesterol-fed monkeys.

In control aortas perfused with [l-¹⁴C]acetate phospholipid and triglyceride comprised approximately 90 % of lipid radioactivity. Among cholesterol-fed monkeys there was a slight increase in incorporation of newly synthesized fatty acids into aortic phospholipids with a slight decrease into triglycerides. Cholesteryl ester synthesis was increased approximately 6 times; oleic acid showed the greatest relative increase in synthesis.

[2-¹⁴C]Mevalonate incorporation into aortic lipids was similar for both groups. More than 95 % of the total lipid radioactivity was recovered in two fractions, one has been identified as squalene.

Perhaps most significant in these studies is the demonstration of metabolic changes (primarily an increase in cholesteryl ester synthesis) occurring in arteries only slightly more diseased than controls.