2.  Main lipids in the blood are the triglycerides and cholesterol.  Insoluble in the water.  Transport in the blood is via lipoproteins

3. TRIGLYCERIDES  Glycerol with 3 attached fatty acids  Exogenous source : Dietary  Endogenous : Liver and tissue storage  95 % of body fat is triglycerides  Energy source when plasma glucose is decreased  Triglyceride catabolism is regulated by lipase, epinephrine and cortisol  Triglycerides transported by Chylomicrons ( exogeneous ) and VLDL ( endogenous )

4. CHOLESTEROL  Found only in animals  Important component of membranes, steroid hormones, bile and Vitamin D  Exogeneous cholesterol comes from diet  Endogeneous cholesterol is synthesized by the liver  70 % of cholesterol associated with cellular components  30 % is in the plasma ( ⅓ free form, ⅔ esterfied )   Transported by HDL and LDL 4

5.  Fatty acids are short to long carbon chained molecules  Saturated fatty acids  Unsaturated fatty acids  Phospholipids  Important components of cell membranes  Lecithin and sphingomyelin are utilized to determine fetal lung maturity from amniotic fluid ( L / S Ratio )  Glycolipids  Lipids with a carbohydrate component  ABO antigen are glycolipids

6. Lipoprotein is a complex spherical structure that has a hydrophobic core wrapped in hydrophilic coating. 4 major classes of lipoproteins. Chylomicrons Very low density lipoproteins (VLDL) Low density lipoproteins (LDL) High density lipoproteins (HDL)

8. Class Diameter (nm) % protein % cholesterol % phospholipid % triacylglycerol & cholesterol ester HDL5–153330294 LDL18–282550218 IDL25–5018292231 VLDL30–8010221850 Chylomicrons100-1000<28784

10. Most core lipid in LDL is cholesterol ester. ApoB100 is only apolipoprotein in the surface.

11.  Also named as apoB-100/apoE receptors  LDL receptors exist in the liver and in most peripheral tissues  The complexes of LDL and receptor are taken into the cells by endocytosis, where LDL is degraded but the receptors are recycled  Number and function of the receptor shows LDL levels.  LDL cholesterol levels are positively related to risk of cardiovascular disease  Therefore, cholesterol in LDL has been called “bad cholesterol”

12. APOLIPROPROTEINS  Outer protein “shell” of the lipoprotein molecule  The protein – lipid interaction allows the water insoluble lipid to become soluble in plasma 12

13.  A, B, C, D, E are major classes  Subclasses: apo A-1, apo C-II  N.B. function of all apolipoproteins are not yet known Act as structural components of lipoproteins Recognize the lipoprotein receptors on cell membrane surface as ligand Activate/inhibit enzymes involved in lipoprotein metabolism

14.  Exogenous  Endogenous  Lipoprotein lipase  release FFA and glycerol from chylomicron and VLDL  Lecithin Cholesterol acyl transferase LCAT  Forms cholesteryl esters from free cholesterol and fatty acids

17.  Serum lipoprotein concentrations differ between adult men and women,  Primarily as a result of differences in sex hormone levels,  Women having, on average, higher HDL cholesterol levels and lower total cholesterol and triglyceride levels than men.  The difference in total cholesterol, however, disappears after menopause as estrogen decreases

18.  Familial hypercholesterolemia (FH) (7.5- 12 mmol/L)  Primarily LDL elevations  Synthesis may be normal but decrease or lack LDL receptors due to mutation in LDL receptor gene.  Therefore LDL builds-up in serum  Since cells cannot acquire from LDL therefore increase internal synthesis of cholesterol.  Tendon xanthomatas  Early occurrence of coronary artery disease M. Zaharna Clin. Chem. 2009 18

19.  Triglycerides  Borderline = 150-200 mg/ dl  High 200-500 mg/dl  Very High > 500 mg/dl  Familial hypertriglyceridemia  Genetic  Secondary hypertriglyceridemia  Hormonal imbalances  Imbalance between synthesis and clearance of VLDL M. Zaharna Clin. Chem. 2009 19

20.  Generally caused by deficiency of LPL or LPL cofactor. (LPL hydrolyzes triglycerides in chylomicrons and VLDL)  Deficiency prevents processing and clearing of triglycerides  Elevated even with fasting M. Zaharna Clin. Chem. 2009 20

21.  Presence of elevated levels of serum total cholesterol and triglycerides  Hepatic overproduction of apo B  Increased VLDL and LDL M. Zaharna Clin. Chem. 2009 21

22.  Genetic mutation of LPL or apo C-II gene  Recurrent abdominal pain  Pancreatitis

23.  Primary  Secondary

26. DiseaseLipid abnormality DMTG AlcoholTG CRFTG Drugs thiazideTG HypothyroidismCholesterol Nephrotic syndromeCholesterol