1. ApoBLipoprotein profile modelling to derive cardiovascular risk markers Albert de Graaf

2. Dietary fat absorptionFrom: Keith Frayn, Metabolic Regulation - A Human Perspective. Wiley-Blackwell, Third Edition, 2010 3. Exogenous pathway of lipoprotein metabolismFrom: Keith Frayn, Metabolic Regulation - A Human Perspective. Wiley-Blackwell, Third Edition, 2010 4. Endogenous pathway of lipoprotein metabolismFrom: Keith Frayn, Metabolic Regulation - A Human Perspective. Wiley-Blackwell, Third Edition, 2010 5. HDL metabolismFrom: Keith Frayn, Metabolic Regulation - A Human Perspective. Wiley-Blackwell, Third Edition, 2010 6. Forward and reverse cholesterol transportFrom: Keith Frayn, Metabolic Regulation - A Human Perspective. Wiley-Blackwell, Third Edition, 2010 7. Lipoprotein structure 8. Different lipoprotein classesFrom: Keith Frayn, Metabolic Regulation - A Human Perspective. Wiley-Blackwell, Third Edition, 2010 9. Lipoprotein Distribution (LPD) measurement 10. Cholesterol and heart diseaseFrom: Keith Frayn, Metabolic Regulation - A Human Perspective. Wiley-Blackwell, Third Edition, 2010 11. Stable isotope studies: lipoprotein classes correspond to kinetically different pools Multicompartmental model for apoB metabolism in VLDL1 (Sf 60400), VLDL2 (Sf 20-60), IDL (Sf 1220), and LDL (Sf 0-12).Tracer data time range 0-250h !!!Gaw A et al. 1996 Arterioscler Thromb Vasc Biol 16:236-249 12. Our vision LPD kinetic model developmentModel-based LPD analysis Lipoprotein flux ratio biomarkers 13. Advantage of our concept From one single plasma measurement to rates of processes Process rates are closer to functional activity than concentrations! better resolution to pick up risk-associated variation in lipoprotein metabolism ? New cardiovascular risk markers? New diagnostic?Otherwise, determination of process rates is only possible with costly stable-isotope studies 14. Particle Profiler project overview 15. Background of model Model development=> Particle size-dependent rate constants => fluxes of different lipoprotein processes: -Hepatic production Peripheral lipolysis Liver attachment (ApoE- and ApoB-mediated) Hepatic uptake (annihilation of particle) Hepatic lipolysisApplied to each e.g. 0.1 nm subclass in the range 100 10 nm 16. Lipolysis cascades - 1 Model developmentBest fit overall 17. Lipolysis cascades - 2The ApoB LPD size range is divided into 11 cascade fractions Each cascade has e.g. 1000 particle subfractions (pools).Model developmentEach subsequent cascade has smaller size ranges of itself and of all its subfractions Each lipolysis step transfers particles from a given cascade to the next cascade The other processes can add or remove particles from each cascade For every subfraction a particle mass balance is set up The computer solves the 11000 mass balances for steady state simultaneously The result is a simulated LPD whose appearance depends on the process parameter settings The simulated LPD is compared to a measured LPD A parameter optimization algorithm searches the best parameter settings 18. Lipolysis steps - decreasing particle sizeapoB apoE uptake uptakeHL - lipolysisLPL - lipolysisProductionLiver attachmentModel development 19. Lipoprotein production process modelProduction flux (particles / min)Model developmentVLDL1VLDL2IDL Lipoprotein diameter (nm)LDL 20. Lipolysis and uptake process models (single particle rates)0.02process rate (1 / min)Model developmentEach subfraction particle P flux component F is modeled as F = k(r).P with k(r) explicitly depending on particle subfraction diameter according to a 1- or 2- paramer functionliver attachment extrahep. lipolysis uptake hepatic lipolysis0.0150.010.0050 1008060 40 lipoprotein diameter (nm)20 21. Flux Data for model testing Packard et al. 2000, human study Model validationstable isotope fluxes analyzed with multi-compartment model Three groups of subjects, healthy men Large LDL peak size (>26 nm) Intermediate LDL peak size (25 26 nm)Small LDL peak size (