Dietary beef tallow alters the fatty acid profiles of bile and liver membranes, but not secretion of cholesterol in bile

To test the hypothesis that type and amount of dietary fat has a regulatory effect on secretion of cholesterol in bile, young growing pigs were fed di ets containing either 20 % or 40% of energy as primarily either beef tallow or soybean oil or as a 50:50 (wt:wt) blend of tallow and soybean oil. Afte r week 6, pigs were injected with autologous low-density lipoproteins conta ining H-3-cholesterol. Serial bile samples were collected for 24 hours; the n tissues were collected. Amount of tallow in dietary fat correlated positi vely (P < 0.05) with amounts of palmitoleic and oleic and negatively with l inoleic and linolenic fatty acids in biliary phospholipids. In addition, am ount of tallow in dietary fat correlated positively with amounts of myristi c, palmitoleic and oleic acids but negatively with stearic acid in membrane s of liver. Composition of dietary fat, however, did not affect concentrati on or daily secretion of cholesterol, bile acids or phospholipids in bile. Furthermore, secretion of H-3-cholesterol as biliary cholesterol or bile ac ids was not affected by type or amount of dietary fat. Concentration of cho lesterol in liver tended to be greater in pigs fed diets containing tallow (P<0.10); no differences in cholesterol concentrations, however, were seen in aorta, heart, skeletal muscle, or gastrointestinal tract. Percentage of injected 3H-cholesterol was greater (P<0.001) in perirenal adipose tissue f rom pigs fed diets containing soy oil than from pigs fed diets containing t allow. There were no significant differences (P<0.05) seen in percentage of injected H-3-cholesterol deposition in several other organs. In summary, t ype of dietary fat altered fatty acid composition of biliary phospholipids and liver membranes but had no effect on cholesterol secretion into bile an d no major Effects on cholesterol distribution in major organs of young pig s. (C) 1999 Elsevier Science Inc.