Lipid metabolism and experimental atherosclerosis in baboons: influence of cholesterol-free, semi-synthetic diets

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Abstract
Four groups of six (three male, three female) baboons (Papio ursinus) were maintained for 1 year on a semi-synthetic diet of the formula: 40% carbohydrate, 25% casein, 14% hydrogenated coconut oil, 15% cellulose, 5% salt mix (USP XIV), and 1% vitamin mix. Four carbohydrates were used: glucose, fructose, sucrose, and starch. A fifth group was fed a normal diet consisting of bread, fruit, and vegetables. At the beginning of the experiment two baboons from each group (one male, one female) were given labeled mevalonic acid intravenously and patterns of cholesterol biosynthesis were determined. The same animals were used for determination of cholesterol synthesis at the end of the experiment. Serum total cholesterol, β-lipoprotein cholesterol, and triglyceride levels were elevated in all the test animals. Liver and hung esterified cholesterol levels were also elevated. The levels of total biliary bile acids varied, but the ratio of primary to secondary bile acids was higher in the control baboons, suggesting decreased bile acid synthesis in the test animals. Cholesterol biosynthesis patterns were similar, but the peak of serum esterified cholesterol specific activity in the second experiment occurred later in the baboons fed fructose and sucrose. All test baboons exhibited aortic sudanophilia. The percentage of aortic area stained was: fructose, 11.2; sucrose, 6.7; starch, 9.3; glucose, 6.2; and control, 0.02. When aortas were ranked for order of severity of sudanophilia the order was fructose, sucrose, starch, glucose, control. The data show that a semi-synthetic, cholesterol-free diet will cause hyperlipemia and aortic sudanophilia in baboons.