1. Cholesterol Metabolism and the Concept of Dual Inhibition David E. Cohen, MD, PhD

2. Overview Digestive lipid metabolism Cholesterol balance Inhibitors of cholesterol synthesis and absorption Dual inhibition

3. Digestive Lipid Metabolism

4. Reverse Cholesterol Transport BloodBlood Peripheral Tissues LiverLiver Bile Excess Cholesterol

5. Cholesterol Catabolism into Bile Salts CholateCholateCholesterolCholesterol Cholesterol 7-hydroxylase HO HOOH COO - OH

6. Bile Salts Breakdown products of cholesterol Amphipathic molecules Function to transport cholesterol in the digestive system

7. Structure of Biliary and Intestinal Micelles CholesterolCholesterol Bile Salt PhospholipidPhospholipid

8. Functions of Micelles Transport cholesterol from the liver into the intestine via the biliary tree Participate in fat digestion and absorption

9. Biliary Lipid Secretion Sinusoidal Membrane BloodBloodHepatocyteHepatocyte Canalicular Membrane Bile Salt ABCG5/G8 Cholesterol ABCB4 Phospholipid ABCB11 BileBile

10. Biliary Lipids Daily Secretion (g) Lipid Class Bile salts Phospholipids Cholesterol 24 11 2

11. Biliary Lipid Transport DuodenumDuodenum JejunumJejunum IleumIleum ColonColon Biliary Transport and Storage Liver

12. Fat Digestion DuodenumDuodenum JejunumJejunum IleumIleum ColonColon Biliary Transport and Storage Liver

13. Fat Digestion TriglyceridesTriglycerides Dietary Cholesterol Fatty Acids + Monoglycerides

14. Fat Absorption DuodenumDuodenum JejunumJejunum IleumIleum Biliary Transport and Storage ColonColon Liver

15. LymphLymphEnterocyteEnterocyte Intestinal Lumen Cholesterol Absorption Cholesterol NPC1L1 Cholesteryl Ester ABCG5/G8 ACAT

16. LymphLymphEnterocyteEnterocyte Intestinal Lumen Triglyceride Absorption 2 Fatty Acid + Monoglyceride DGAT Triglyceride

17. LymphLymphEnterocyteEnterocyte Intestinal Lumen Chylomicron Formation Cholesteryl Ester CM apoB48 Triglyceride

18. Cholesterol Balance

19. DuodenumDuodenum JejunumJejunum IleumIleum ColonColon Portal Venous Return (>95% of Biliary Secretion) Fecal excretion (0.4 g/d) Biliary Transport and Storage Liver Synthesis 0.4 g/d Secretion 24 g/d Enterohepatic Circulation of Bile Salts

20. DuodenumDuodenum JejunumJejunum IleumIleum ColonColon Biliary Transport and Storage Fecal excretion (1.2 g/d) Dietary Cholesterol (0.4 g/d) Absorption ~50% CM apoB48 Liver Biliary Cholesterol (2 g/d) Biliary and Dietary Cholesterol

21. Cholesterol Balance DuodenumDuodenum JejunumJejunum IleumIleum ColonColon Biliary Transport and Storage Cholesterol Cholesterol (1.2 g/d) + Bile Salts (0.4 g/d) Dietary Cholesterol (0.4 g/d) Loss (1.6 g/d) Bile salts Loss (1.6 g/d) — Dietary Cholesterol (0.4 g/d) Synthesis (1.2 g/d) Liver

22. Inhibitors of Cholesterol Synthesis and Absorption

23. Inhibitors of Cholesterol Synthesis: Statins Inhibit synthesis of cholesterol by cells Lower LDL cholesterol Mechanism: Promote LDL Clearance

24. LDL Receptor Statins Acetate LDLLDL HMG-CoA Reductase Cholesterol

25. Cholesterol Absorption Inhibitors Inhibit absorption of dietary cholesterol Inhibit reabsorption of biliary cholesterol Lower LDL cholesterol Mechanism: Inhibit LDL Formation

26. Plant Sterols and Stanols Sterol/StanolSterol/Stanol Dietary Cholesterol

27. LymphLymphEnterocyteEnterocyte Intestinal Lumen Plant Sterols and Stanols Cholesterol Cholesteryl Ester ABCG5/G8 ACAT NPC1L1

28. LymphLymphEnterocyteEnterocyte Intestinal Lumen Ezetimibe Cholesterol NPC1L1 Cholesteryl Ester ABCG5/G8 ACAT Ezetimibe X

29. LymphLymphEnterocyteEnterocyte Intestinal Lumen Cholesterol Absorption Inhibitors Cholesteryl Ester CM apoB48 Triglyceride

30. Cholesterol Absorption Inhibitors DuodenumDuodenum JejunumJejunum IleumIleum CM apoB48 Liver CM Remnant apoB48 VLDL apoB100 EzetimibeX LDL apoB100 ColonColon

31. Dual Inhibition

32. Assembly and Secretion of VLDL Presence of Triglycerides ApoB MTP Cholesteryl Esters Cholesterol Dietary/Biliary Synthesis

33. Effect of Cholesterol Absorption Inhibitor Presence of Triglycerides ApoB Cholesterol Dietary/Biliary Synthesis Ezetimibe X MTP Cholesteryl Esters

34. Adding a Statin Blocks Compensatory Increase in Synthesis Presence of Triglycerides ApoB Cholesterol Dietary/Biliary Synthesis Ezetimibe XX Statin MTP Cholesteryl Esters

35. Dual Inhibition DuodenumDuodenum JejunumJejunum IleumIleum CM apoB48 Liver CM Remnant apoB48 VLDL apoB100 EzetimibeX LDL apoB100 X Statin ColonColon

36. Conclusions Cholesterol balance is regulated by both synthesis and absorption Inhibition of cholesterol absorption may be compensated by increases in synthesis Optimal LDL lowering may best be achieved by inhibiting both pathways