Effect of Dietary Fat on Hepatic Metabolism of 14C-Oleic Acid and Very Low Density Lipoprotein Triglyceride in the Gerbil

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Abstract
In order to compare in vitro and in vivo aspects of lipid metabolism and lipoprotein secretion associated with the hyperlipemia of saturated fat feeding, gerbils were fed a diet containing 15% coconut oil or safflower oil for 6 weeks. In vitro incorporation of fatty acid was determined by measuring 14C-oleic acid incorporation into hepatic lipids in liver slices, whereas in vivo secretion of hepatic lipoprotein was determined in fasting gerbils following Triton WR1339 injection. The plasma lipoprotein profile was assessed by agarose electrophoresis. Coconut oil produced a hypertriglyceridemia and hypercholesterolemia associated with the appearance of very low density migrating lipoprotein, not seen with the safflower oil. Coconut oil also increased the hepatic triglyceride content, enhanced 14C-oleic acid incorporation into total lipid, and favored fatty acid incorporation into triglyceride; safflower oil facilitated esterification of oleic acid into phospholipid. Triton blockade of gerbils fed safflower oil resulted in twice the triglyceride secretion rate of those fed coconut oil. Our interpretation of the data is that dietary polyunsaturated fat favors incorporation of fatty acids into phospholipid, enhances both triglyceride secretion and the plasma transport and clearance of triglyceride and cholesterol and that the hyperlipemia of coconut oil feeding reflects a reduced metabolic clearance of circulating lipid associated with that dietary fat.