Effects of diets rich in saturated fatty acids with or without added cholesterol on plasma lipids and lipoproteins

Semi-synthetic diet I which contained 16% hydrogenated coconut oil and 5% cholesterol, and diet II, identical to I but without cholesterol supplement, were fed to dogs for four months to determine the effects of added cholesterol on lipemia produced by diets high in saturated fatty acids (FA) and lacking essential FA. In addition, diet I was fed to another group of dogs for 12 to 16 months. The initiation of lipemia was very similar in all experimental animals. Plasma from dogs on diets I and II showed significant increases in lipid concentration and changes in FA per cent composition within the first week, as compared to controls, while during the first month there was no difference in lipid concentration or FA distribution in all lipid fractions between I and II. At the 10th and 16th weeks plasma total and free cholesterol and phospholipid were significantly higher in the group on diet I, with the cholesterol supplement, than on diet II with no added cholesterol, but there was no difference in triglyceride concentration between these groups. Dogs on diet I for 12 to 16 months showed a further and substantial increase in plasma FA concentration; these changes were most marked in cholesteryl esters. Little or no lipoprotein with electrophoretic and ultracentrifugal properties of alpha-lipoprotein was present in the plasma. Immunotechniques showed that it was present. The composition of dietary FA had great influence in producing this hyperlipemia. Lipemia produced was not a simple reflection of the FA in these diets as evidenced by the increase in some FA, e.g., C_16∶1, which was absent in the experimental diets and C_18∶1, which contributed only 3.4% of the FA. Large increases in palmitoleate and oleate indicate synthesis or mobilization or both from other tissues. Diets composed predominantly of saturated medium chain length fatty acids, with or without added cholesterol were equally effective in the initiation of hyperlipemia. Data also suggest that added cholesterol is necessary for sustaining hyperlipemia. Presented in part at the AOCS Annual Meeting, New Orleans, April 1970.