Kinetics of the disappearance of lipoprotein cholesteryl esters in pigs as affected by dietary fat
Forty crossbred, castrated male pigs were fed diets containing primarily beef tallow (T) or soy oil (S) at 20% or 40% of energy as fat in a 2 x 2 factorial design. During week 6, pigs were fitted with femoral arterial, common bile duct, and duodenal catheters. After week 8, pigs were injected with autologous low-density lipoprotein (LDL) containing [superscript]3H-cholesteryl esters and high-density lipoprotein (HDL) containing [superscript]14C-cholesteryl esters. Blood and bile were collected for 48 hours. Disappearance of the labeled cholesteryl esters fit a biexponential function, and the parameters of the function were described by compartmental analysis. Pigs fed T diets had greater concentrations of cholesterol in Longissimus dorsi and a greater percentage of total lipid in liver than did pigs fed S diets. Pigs fed T diets had greater percentages of palmitic, palmitoleic, and oleic acids and lesser percentages of stearic, linoleic, and linolenic acids in bile. Pigs fed S diets had a greater retention of cholesterol derived from LDL-cholesteryl esters (LDL-CE) in L. dorsi and a greater appearance of cholesterol from HDL-cholesteryl esters (HDL-CE) as biliary cholesterol. Twelve hour "fasted" HDL-CE concentrations were greater in pigs fed T diets. After a meal, the HDL-Ce concentrations in pigs fed T diets decreased to concentrations similar to those in pigs fed S diets. Pigs fed diets containing 40% of energy as fat (40%) had greater LDL-CE production rates and fractional catabolic rates than did pigs fed diets containing 20% of energy as fat (20%). In the L. dorsi the percentage of cholesterol derived from LDL-CE was greater in pigs fed the 40% diets. The percentage of cholesterol derived from HDL-CE was greater in livers of pigs fed 20% diets, whereas pigs fed 40% diets secreted more HDL- and LDL-CE as biliary cholesterol, had greater bile flows, and secreted more biliary cholesterol. In summary, dietary fats affected LDL- but not HDL-lipoprotein kinetics. Clearance of cholesterol into bile and storage of cholesterol in tissues were increased by polyunsaturated fat and high fat diets, which is consistent with current theories on mechanisms of dietary fatty acid effects on cholesterol metabolism.