Differences in response between 18 carbon fatty acids and 12/14 carbon saturated fatty acids on plasma cholesterol in guinea pigs

Male guinea pigs were fed four different diets rich in lauric plus myristic (LM), stearic (ST), oleic (OL) or linoleic (LN) fatty acids to compare the effects of 18 carbon fatty acids with different degrees of saturation with 12/14 carbon saturated fatty acids on hepatic cholesterol metabolism. Animals fed the LM diet had 76-100% higher plasma total cholesterol and apo B concentrations than those fed ST, OL or LN diets (P < 0.001). The hypercholesterolemic effects of LM intake were associated with concomitant increases in plasma LDL cholesterol. No difference in plasma VLDL and HDL cholesterol or triacylglycerol (TAG) concentrations were observed among the four groups. VLDL + IDL and LDL composition were significantly altered by dietary fat saturation. The relative proportion of free cholesterol was higher and TAG lower in VLDL of animals fed the LM diet. Cholesteryl ester concentrations in LDL decreased as chain length and saturation of fatty acids increased in the order LN<OL<ST<LM. Hepatic cholesterol was not affected by dietary fatty acids. In contrast hepatic 3-hydroxy-3-methyl-glutaryl coenzyme A reductase activity was lower in animals fed the LM diet while no differences in acyl CoA cholesterol:acyltransferase activity were observed among dietary groups. Plasma lecithin:cholesterol acyl:transferase activity was higher in animals fed LM and ST diets compared to those fed OL and LN diets (P < 0.01). Hepatic apo B/E receptor number was highest in animals fed LN diet and intake of ST and OL diets resulted in higher hepatic apo B/E receptor number compared to animals fed LM diets (P < 0.001). These studies indicate that the different fatty acids affect plasma cholesterol levels by alterations on hepatic cholesterol metabolism. While intake of stearic, oleic and linoleic acids result in similar plasma cholesterol levels, short chain fatty acid intake results in hypercholesterolemia in guinea pigs. (C) 1998 Elsevier Science Inc.