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 myr istic (LM), stearic (ST), oleic (OL) or linoleic (LN) fatty acids to c ompare the effects of 18 carbon fatty acids with different degrees of saturation with 12/14 carbon saturated fatty acids on hepatic choleste rol metabolism. Animals fed the LM diet had 76-100% higher plasma tota l cholesterol and apo B concentrations than those fed ST, OL or LN die ts (P < 0.001). The hypercholesterolemic effects of LM intake were ass ociated with concomitant increases in plasma LDL cholesterol. No diffe rence in plasma VLDL and HDL cholesterol or triacylglycerol (TAG) conc entrations were observed among the four groups. VLDL + IDL and LDL com position were significantly altered by dietary fat saturation. The rel ative proportion of free cholesterol was higher and TAG lower in VLDL of animals fed the LM diet. Cholesteryl ester concentrations in LDL de creased as chain length and saturation of fatty acids increased in the order LN<OL<ST<LM. Hepatic cholesterol was not affected by dietary fa tty acids. In contrast hepatic 3-hydroxy-3-methyl-glutaryl coenzyme A reductase activity was lower in animals fed the LM diet while no diffe rences in acyl CoA cholesterol:acyltransferase activity were observed among dietary groups. Plasma lecithin:cholesterol acyl:transferase act ivity 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 highes t in animals fed LN diet and intake of ST and OL diets resulted in hig her hepatic apo B/E receptor number compared to animals fed LM diets ( P < 0.001). These studies indicate that the different fatty acids affe ct plasma cholesterol levels by alterations on hepatic cholesterol met abolism. While intake of stearic, oleic and linoleic acids result in s imilar plasma cholesterol levels, short chain fatty acid intake result s in hypercholesterolemia in guinea pigs. (C) 1998 Elsevier Science In c.