Contribution of postprandial lipemia to the dietary fat-mediated changes in endogenous lipoprotein-cholesterol concentrations in

Background: Dietary fats alter LDL and HDL cholesterol while serving as precursors of postprandial triacylglycerol-rich lipopro- teins (TRLs). Objective: We hypothesized that the saturated fatty acid (SFA)- mediated increase and the polyunsaturated fatty acid (PUFA)-me- diated decrease in endogenous lipoprotein cholesterol are promoted by postprandial TRLs. Design: We performed a 16-d crossover diet study to examine the effect of PUFA-rich (ratio of PUFAs to SFAs (P:S) 2.0) and SFA-rich(P:S0.25)dietsonfastingandpostprandialplasmalipid and lipoprotein-cholesterol concentrations in 16 normolipidemic subjects. Results: Fasting plasma cholesterol decreased significantly after a PUFA-rich diet because of a decrease in LDL (12.3%; P 0.05) and HDL (3.8%; NS), but did not change after an SFA-rich diet. The appearance of postprandial TRLs in plasma at 4 h was linked to asignificantloweringofbothLDL(7.4%)andHDL(4.8%)after a PUFA-rich diet; no such effect was observed after the SFA-rich diet. At 7 h, LDL and HDL cholesterol returned to near fasting concentrations without postprandial TRL accumulation after a PUFA-rich diet but with a significant postprandial TRL accumula- tion after an SFA-rich diet. Thus, the in vivo postprandial clearance ofcholesterolinLDLHDLwasgreaterafteraPUFA-richdietthan after an SFA-rich diet. The appearance of postprandial TRLs in plasma increased the cholesteryl ester transfer protein-mediated transferofcholesterylesterfromLDLHDLtoTRLsinvitrowith- out a significant influence from dietary fat. Conclusion: Dietary fat-mediated alterations in the rate of hepatic removal of postprandial TRLs, which carry cholesterol accepted from LDLHDL via cholesteryl ester transfer protein in vivo, may contribute to the dietary fat-mediated change in endogenous li- poprotein cholesterol. Am J Clin Nutr 2004;80:1145-58.