Lipid profile tests by Pragya Pandey
- 1. LIPID PROFILE TESTS. Presented by pragya pandey
- 2. INTRODUCTION DEFINITION- Lipids are group of organic substances of fatty nature which are insoluble in water, soluble in fat solvents and which are related to fatty acids.
- 3. IMPORTANCE OF LIPIDS. 1. Reservoir of energy. 2. Constituents of cell membrane. 3. As a insulater and protective coating. 4. Constituents of neural tissue.
- 4. LIPOPROTEINS They are spherical complexes of lipids and proteins. Transport various lipids and fat soluble vitamins to and from tissues. Contain core of hydrophobic lipids surrounded by hydrophilic lipids and proteins.
- 5. Classification of Lipoproteins. Depending on the density or on the electrophoretic mobility,the lipoproteins in plasma are classified into five major types:
- 6. Classification of Lipoproteins: 1. Chylomicrons – Contain appoprotein B-48. 2. Very Low density lipoproteins(VLDL) or pre-beta lipoproteins.Main apoprotein is B-100. 3. Intermidiate density lipoproteins (IDL) or broad beta lipoprteins. 4. Low density lipoproteins (LDL) or beta – lipoprteins.Major apoprotein in HDL is apo-A. 5. High density lipoproteins (HDL) or alpha – lipoproteins.Major apoprotein in HDL is apo-A.
- 7. CHYLOMICRONS: SYNTHESIS OF CHYLOMICRONS- Chylomcrons are formed in the intestinal mucosal cells,and secreted into the lacteals of lymphatic system. They are rich in triglyceride. When the chylomicrons are synthesized by the intestinal mucusa,they contain only apo-48 and apo-A
- 8. Metabolism of Chylomicrons: Main sites of metabolism of chylomicrons are adipose tissue and skeletal muscle. The enzyme lipoprotein lipase(LPL) is located at the endothelial layer of capillaries of adipose tissue ,muscles and heart;but not in liver. Apo –C-II present in the chylomicrons activates the LPL. The LPL hydrolyses triglycerides present in chylomicrons into fatty acids and glycerol.
- 9. Function of Chylomicrons: Chylomicrons are the transport form of dietary triglycerides from intestines to the adipose tissue for storage; and to muscle or heart for their energy needs.
- 10. VERY LOW DENSITY LIPOPROTEINS: SYNTHESIS OF VLDL :Triacylglycerol synthesized in liver is incorporated into VLDL when it is secreted. METABOLISM OF VLDL:When they reach the peripheral tissues,apo-C-II activates LPL which liberates fatty acids that are taken up by adipose tissue and muscle. The remnant is now designated as IDL(intermediate density lipoprotein ) and contain less of TAG and more of cholestrol. FUNCTION OF VLDL:The VLDL carries endogenous TAG from liver to peripheral tissues for energy needs.
- 11. LOW DENSITY LIPOPROTEINS : Low density lipoproteins (LDL) transports cholestrol from liver to peripheral tissues. The only apoprotein present in LDL is apo-B-100. Most of the LDL in blood is about 2 days.
- 12. METABOLISM OF LDL AND LDL RECEPTORS: The LDL is taken up by peripheral tissues by receptor- mediated endoytosis. LDL receptors are located in specialized regions called CLATHRIN-COATED PITS. Binding of LDL to the receptor is by apo-B-100 receptor ,the receptor –LDL complex is intenalized by endocytosis. The LDL particle,along with apoproteins and cholestrol ester are hydrolysed to form free cholestrol. The free cholestrol is either incorporated into plasma membranes or esterified and stored within the cell.
- 13. FUNCTION OF LDL: About 75% of the plasma cholestrol is incorporated into the LDL particles. LDL transports cholestrol from liver to the peripheral tissues. It is used for the synthesis of other steroids like steroid hormones. Cholesterol may be incorporated into the membranes.
- 14. LDL and Clinical Appliances: The LDL concentration in blood has positive correlation with incidence of cardiovascular diseases. A fraction of cholestrol is taken up by macrophages. Increased levels of LDL or oxidation of LDL increases uptake of cholestrol by macrophages. When macrophages are filled with cholestrol,foam cells are formed. They get deposited in the subendothelial space and leads to the formation of atheromatous plaque. Since LDL – cholestrol is thus deposited in tissues, the LDL variety is called ‘BAD CHOLESTEROL’ in common parlance. Insulin and tri-iodothyronine (T3) increase the binding of LDL to liver cells.
- 15. HIGH DENSITY LIPOPROTEIN: High density lipoproteins (HDL) transport cholestrol from peripheral tissues to the liver. METABOLISM OF HDL: The intestinal cells synthesize components of HDL and release into blood. The nascent HDL in plasma are discoid in shape. The free cholestrol derived from peripheral tissue cells are taken cells are taken up by the HDL. The apo-A-I of HDL activates LCAT(lecithin cholestrol acyl tranferase) present in the plasma. The LCAT then binds to the HDL disk.
- 16. FUNCTIONS OF HDL: I. HDL is the main transport form of cholestrol from peripheral tissue to liver which is later excreted through bile.This is called reverse cholestrol transport by HDL. II. The only excretory route of cholestrol from the body is the bile. III. Excretion of cholestrol needs prior esterifications with PUFA (POLYUNSATURATED FATTY ACID).Thus PUFA will help in lowering of cholestrol in the body,and so PUFA is antiatherogenic.
- 17. CLINICAL SIGNIFICANCE OF HDL: The level of HDL in serum is inversely related to the incidence of myocardial infarction. As it is ‘antiatherogenic’ or ‘protective’ in nature,HDL is known as ‘GOOD CHOLESTROL’ in common parlance. It is cinvenient to remember that ‘H’ in ‘HDL’ stands for ‘healthy’. HDL level below 35 mg/dl increases the risk,while level above 60 mg/dl protects the person from coronary artery diseases.
- 18. TOTAL CHOLESTROL: Total cholestrol measure the combination of LDL,HDL,and VLDL in your bloodstream. VLDL is a precursor of LDL,the bad cholestrol. A total cholestrol score of 200 is considered healthy in most cases. People who score in the ‘high’ range have an increased risk of developing heart disease compared to those who score below 200.
- 19. WHY HIGH CHOLESTROL MATTERS? High cholestrol is one of the major risk factos for coronary artery disease,heart attacks,and strokes. It also appears to boost the risk of Alzheimer’s disease. As we know that ,high cholestrol leads to a buildup of plaque that narrows the arteries. This is dangerous because it can restrict blood flow If the blood supply to a part of the heart or brain is completely cut off,the result is a heart attack or stroke.
- 20. TRIGLYCERIDES: The body converts excess calories,sugar,and alcohol into triglycerides,a type of fat that is carried in the blood and stored in fat cells throughout the body. People who are overweight,inactive ,smokers ,or heavy drinkers tend to have high triglycerides,as do those who eat a very high –carb diet. A triglycerides score of 150 or higher puts you at risk for metabolic syndrome,which is linked to heart disease and diabetes.