Abstract 17789: Food Intake Suppresses Endogenous Apolipoprotein B100 Metabolism
Background: Humans spend much of the day in the postprandial state. However, current clinical guidelines recommend that blood for lipid profiles be drawn after 12-hr fast. It is unclear how lipoprotein metabolism in the postprandial state deviates from the fasting state.
Methods: We investigated the transport of plasma apoB100 by stable isotope tracers in 12 volunteers under both fasting and postprandial conditions in a cross-over study design. Fasting state studies started after an overnight fast, and lasted for 15 hrs with restricted food intake, while a steady postprandial state was achieved via hourly feeding of small meals. We separated plasma apoB100 lipoproteins into 18 subfractions by anti-apoCIII and apoE immunoaffinity chromatography and ultracentrifugation.
Results: ApoB lipoprotein metabolism differs substantially between fasting and postprandial states. We observed two-fold changes in the secretion pattern of VLDL, triglyceride-rich lipoproteins that are precursors of LDL. The main feature of the postprandial state is significant reductions in secretion of light and dense VLDL (53% and 45%, p<0.01), indicating suppression of endogenous lipoprotein secretion after a meal. This is also true for the secretion of IDL, and light and dense LDL. Second, the secretion pattern of VLDL phenotypes was also shifted: the percentage of light and dense VLDL secreted without apoE or apoCIII increased in the postprandial state, while secretion of particles containing apoE decreased. Concurrent with suppressed liver secretion, apoB lipoproteins were also metabolized more slowly in the postprandial state, as shown by significantly lower fractional catabolic rates of VLDL, IDL and LDL. Interestingly, despite these large postprandial changes in apoB secretion and metabolism, apoB pool sizes for most apoB lipoprotein subtypes remained unchanged due to the simultaneous slowdown of both pathways.
Conclusion: During a prolonged fast, endogenous apoB lipoprotein metabolism is activated, characterized by increased production, transport and metabolism. During intake of a balanced diet, endogenous apoB lipoprotein metabolism is reduced as appropriate to balance the dietary input to maintain the supply of energy to peripheral tissues.
- © 2010 by American Heart Association, Inc.