1. 1) OBESITY & high plasma triglycerides Adipose cells, adipocytokines. White fat cells store large lipid droplets of triglycerides and cholesterol ester. Leptin (167aa) synthesised and secreted, peptide hormone, binds to receptors in hypothalamic nuclei “satiety center.” Regulates energy.Signals a decrease in appetite. Prooxidant. Adiponectin (244aa), most abundant protein in adipocyte, (similar structure to TNFα) & released into the blood. Higher in females. Antioxidant.  adipocyte oxidative stress (insulin activates NADPH oxidase (Nox4)   body weight,  mitoch.fatty acid oxidation,  gluconeogenesis,  insulin resistance. Insulin causes lipogenesis and fatty acid release ( fatty liver). Plasma adiponectin decr. & leptin incr. in obesity (promotes breast cancer). Brown fat (babies) mitochondria make heat. 1

2. Adipocyte dysfunction & Metabolic disease Obesity due to overnutrition (high fat or sugar diet ) & inactivity causes metabolic disease. Insulin resistance & diabetes mellitus Hypertension Hyperlipidemia, nonalcoholic steatohepatitis (NASH), alcoholic liver disease, chronic hepatitis, liver cancer Therapy:  calories  exercise,taurine,salicylate,thiazolidinediones, Research : how to increase adiponectin levels J.Gastroenterol(2008)43,811-822,Clinical Chemistry (2008)54,945-55 2

3. Fatness increases cancer risk Fatness cancer rate may exceed cancer from smoking soon. Breast cancer, esophagus, colorectal, pancreas, ovary. gall bladder,endometrium, liver (after cirrhosis) NASH. NOT prostate,bladder, mouth, lung, skin, cervix, nasopharynx,skin cancer. Associated with energy-dense foods,fast food,sugary drinks,sedentary living,TV/computers. 2007 WCRF/AICR report 3

4. Figure 1 Following chronic alcohol ingestion, endotoxin is released from certain intestinal bacteria. Endotoxin moves from the gut into the bloodstream and the liver where it activates Kupffer cells- a type of immune cell (resident liver macrophages) - by interacting with CD14 causing nuclear factor kappa B (NFκB) production.This generates superoxide radicals (O2) and various signaling molecules (the cytokine TNF–α) which injures hepatocytes. (Alcohol Res Health. 2003; 27(4):300-6.)

5. 5 2) High plasma cholesterol and atherosclerosis A.Clinical chemistry B.Fat Absorption C.Liver cell synthesis of LDL and HDL D.Cholesterol Synthesis E.Drug Therapy F.Fibroblasts and other extrahepatic tissues for membrane biosynthesis G.Incr. heart attacks,strokes,atheroscelerosis H. Genetic Disorders

6. 6 Lipoproteins, Cholesterol and Atherosclerosis A) Clinical chemistry - Lipoproteins Conjugated proteins in which the prosthetic group are lipids: Lipoproteins responsible for the transport/distribution of lipids: - Lipid hormones - Lipids absorbed by the intestine - Fat-soluble vitamins

7. 7 Percent contribution of saturated fat and cholesterol from fats/oils, meats, dairy products and eggs in the US diet. Biochim. et Biophys. Acta 1529 (2000) 310-320 Plasma cholesterol >6.2mM (change diet); 5.5-6.2mM (borderline); <5.5mM normal

8. 8 A lipoprotein: Horton Fig 17-5

9. 9

10. 10 B) Stage 1 - Fat Absorption Chylomicrons Found in lymph draining the intestine not hepatic portal systems Largest ones are microscopically visible (diameter 500 nm) (floats upon centrifugation) Responsible for the lipemic (milky turbidity) of the blood following food digestion and disappears at 5 hours Contains 1% protein - formed by intestinal cell Triglycerides (apo AI and II, B)

11. 11 B48 M.W. = 300,000 (chylomicrons, chylomicron remnants) Dietary cholesterol  chylomicron & HDL formed in intestinal epithelial cell  remnant  lymph vessel  taken up by adipose cells & extrahepatic tissues

12. 12 C) Stage 2 : LDL activity and function LDL(apoB100) synthesised by liver moves cholesterol to the tissues (taken up by the apoB100 receptor of tissues). LDL carries 75% plasma cholesterol and HDL carries 25%.

13. 13 Liver cell synthesis of LDL,VLDL and HDL B-100 A,C,E i.e. LDL, VLDL, HDL

14. 14 Electron micrograph of a part of a liver cell actively engaged in the synthesis and secretion of very low density lipoprotein (VLDL). The arrow points to a vesicle that is releasing its content of VLDL particles. 10 Liver mitochondrial fatty acid oxidation inhibited by some drugs causing FATTY LIVER

15. 15 F) Stage 3- Fibroblasts and other extrahepatic tissues - cholesterol taken up for membrane biosynthesis Extrahepatic tissues obtain cholesterol from plasma LDL & NOT by synthesis STEPS: a) ApoB100 protein of LDL binds to receptor in coated pits b) Receptor-LDL complex is internalised by endocytosis c) Vesicles containing LDL fuse with lysosomes (proteases, esterases) LDL Protein amino acids LDL Cholesterol esters cholesterol + fatty acid LINOLEATE LDL receptor returns to plasma membrane (10min. - turnover ever 24 hours) proteases esterases

16. 16 Steps (cont’d) d) Free cholesterol in the cell is used or stored Cholesterol Membrane biosynthesis + Linoleate Cholesterol ester i.e., store for cholesterol Acyl-CoA: cholesterol acyl transferase Regulation: When excess, the synthesis of new LDL receptors is stopped, therefore LDL not taken up by cells

17. 17 The LDL receptor Membrane spanning domain The LDL receptor consists of five domains with different functions: an LDL-binding domain, 292 residues; a domain bearing N-linked sugars, 350 residues; a domain bearing O-linked sugars, 58 residues; a membrane- spanning domain, 22 residues; and a cytosolic domain, 50 residues.

18. 18 Four Mutations affecting LDL receptors 1) no receptor is synthesised 2) receptors are synthesised but lack signals for transport  don’t reach plasma membrane 3) receptors reach cell surface but don’t bind LDL normally 4) receptors don’t cluster in coated pits

19. 19 Genetic disorders (cont.) e.g. Familial hypercholesterolemia (Type II) - Autosomal dominant trait 1:500  Cholesterol 680 mg/100 mL instead of 175 mg/100 mL  Die of heart disease before 20 years (homozygous)  Die of heart disease before 40 years (heterozygous– inherit one defective and one normal gene) 1.LDL receptor is unable to bind to coated pits  randomly distributed in membrane  LDL binds but can’t be absorbed by endocytosis 2. Faulty LDL receptor formed which can’t bind LDL

20. 20 Extrahepatic tissue(e.g.fibroblasts) take up cholesterol via LDL receptors and store it as cholesterol esters in lysosomes Voet et al., Fig 19-37

21. 21 Cholesterol Ester Synthesis Endoplasmic reticulum

22. 22 Acid proteases (cathepsins) Cholesterol ester esterase Nucleases Acid phospholipases Require acid pH Amino acids Cholesterol Nucleotides Fatty acids Stores dietary CoQ CoQ reduction maintains acid pH ACID pH H+H+ CoQ ROS Cyt b5 FAD NADH Autophagic vacuole Aged proteins, Nucleic acids, lipids LYSOSOMES recycle proteins,lipids,nucleic acids Arch Biochem Biophys. 375, 347-54, (2000).

23. 23 G) Atherosclerosis – cholesterol plaque formation An atherosclerotic plaque (marked by the arrow) blocks most of the lumen of this blood cell. The plaque is rich in cholesterol.

24. 24 Atherosclerosis mechanism: oxidised LDL taken up by macrophage scavenger receptors Liver

25. 25