Lipid Profile PDF

Lipids Profile Dr. Doaa Samir  Lipids Profile Lipid profile: A pattern of lipids in the blood. A lipid profile usually includes the levels of total cholesterol, high-density lipoprotein HDL-C, triglycerides, and low-density lipoprotein LDL-C and both...

Lipids Profile Dr. Doaa Samir  Lipids Profile Lipid profile: A pattern of lipids in the blood. A lipid profile usually includes the levels of total cholesterol, high-density lipoprotein HDL-C, triglycerides, and low-density lipoprotein LDL-C and both total Cholesterol/HDL-C and LDL-C/HDL-C ratios. The results of this test can identify certain genetic diseases and can determine approximate risks for cardiovascular disease, certain forms of pancreatitis, and other diseases.  Cholesterol Cholesterol is small molecule, one of the steroids. Cholesterol is a type of fat. 70% synthesized by the body, and 30% comes from the foods (animal source as meat and eggs). Blood cholesterol level is related to the foods eaten or to genetic conditions. A higher intake from food leads to a net decreases in endogenous production, whereas lower intake from food has the opposite effect. Cholesterol has important functions in the body important part in membrane of cells, organs and tissues in the body. The hydroxyl group on cholesterol interacts with the polar head groups of the membrane phospholipids, while the bulky steroid and the hydrocarbon chain are embedded in the membrane. In this structural role, cholesterol increase the permeability of the plasma membrane. It is used to make steroid hormones, including the adrenal gland hormones cortisol and aldosterone as well as the sex hormone progesterone, estrogens and testosterone. In the liver, cholesterol is converted to bile, which is then stored in the gallbladder. Bile contains bile salts, which solubilize fats in the digestive tract and aid in the intestinal absorption of the fat molecules as well as the fat-soluble vitamins, vitamin A, D, E and K. Therefore, cholesterol deficiency is not good. While too much cholesterol leads to coronary artery disease. Cholesterol levels High level associated with heart disease Good level: below 200 mg/dl (low risk of heart disease). Border line: 200 - 240 mg/dl (if higher, high risk of heart disease). Measuring blood cholesterol level not need fasting? Cholesterol level is not affected by single meal but affected by long term pattern of eating (change from high fat diet to low fat diet for several weeks). However, if the test is drawn as part of a total lipid profile, it requires a 12-16 hours fast (no food or drink, except water) for accurate triglycerides level. Cholesterol level is elevated during pregnancy (till 6 weeks after delivery) For the most accurate results, wait at least two months after a heart attack, surgery, infection, injury or pregnancy to check cholesterol levels. Laboratory diagnosis method of total cholesterol Testing methods for total cholesterol use cholesterol oxidase reactions along with cholesterol esterase and usually a peroxidase reaction for the “color” or final determination reaction. Reagents’ composition R1 Cholesterol Standard 200 mg/dl R2 Good’s Buffer 100 mmol/L Cholesterol esterase 300 U/L Cholesterol oxidase 1500 U/L Peroxidase 5500 U/L 4-AAP 1 mmol/L Phenol derivates 5mmol/L Procedure Wavelength 546 nm (500-550) Optical path : 1 cm light path Temperature : 20-25 or 37 ᵒC Assay type : Endpoint Procedure: Pipetting in tubes Blank Standard Sample Reagent (R2) 1000 mL 1000 mL 1000 mL Distilled Water 10 mL - - Standard (R1) - 10 mL - Sample - - 10 mL Mix, incubate for 5 min at 37°C or 10 min at 20-25°C and read sample and standard absorbance. Color is stable at least 30 min at room temperature.  (A) Sample Cholesterol mg/dl = × Standard concentration (A) Standard Standard concentration 200 mg/dL  Triglycerides TG (Triacylglycerol) Triglyceride is body storage form of fat and energy. Most TG found in adipose tissue. It gives energy in case of absence of carbohydrates. Some triglycerides circulate in the blood to provide fuel for muscles to work. Extra triglycerides are found in the blood after meal. It elevated in obese or diabetic patients, also from eating foods include simple sugars, such as sweetened beverages, cookies, cakes, candy or drinking alcohol. Associated with heart and blood vessel disease. TG levels TG test needs 12 hrs. fasting because its level affected by meal (fatty meal, high carbohydrates meal). Level should be: Less than 160 mg/dl (for men) and less than 140 mg/dl (for women) High TG leads to fatty liver. Some causes of high triglycerides Poorly-controlled type 2 diabetes: When diabetes is not well- managed, more likely to have high level of glucose (blood sugar) in the body. Insulin activate Glycogenesis i.e., helps conversion of glucose into glycogen and helps to store glycogen in the liver. When the liver becomes too saturated with glycogen, though, glucose is instead used to create fatty acids that are released into the bloodstream. These fatty acids are used to make triglycerides, which build up in fat cells and contribute to body fat.  Insulin resistance: Insulin resistance occurs when the body does not respond to the insulin - as a result, sugar cannot enter the cells and instead remains in the bloodstream. Being resistant to the action of insulin contributes to high levels of both insulin and glucose and can lead to uncontrolled diabetes, which can lead to high triglycerides, as described above. Also, insulin inhibits hormone sensitive lipase (HSL), the primary physiological function of HSL is the mobilization of fatty acids from their triacylglycerol stores in adipose cells. In this case HSL will not work in good state and triglycerides concentration will increase in the body. Obesity: Being obese or overweight is not indicated that will develop high levels of triglycerides, but there is a correlation between obesity and hypertriglyceridemia. There is a stronger correlation between excess waist circumference and high levels of triglycerides than with body mass index.  For the enzymatic determination of Triglycerides according to the following reaction The intensity of the red color produced is directly proportional to Triglycerides in the sample. Reagents’ composition R1 Triglycerides Standard 200 mg/dl R2 Good’s Buffer 100 mmol/L Magnesium Chloride 15 mmol/L ATP 4 mmol/L 4-AAP (4-Aminoantipyrine) 1 mmol/L 4-Chlorophenol 0.1 mmol/L LPL (Lipoprotein Lipase) 2500 U/L GK (Glycerol kinase) 1000 U/L GPO (Glycerol-3-phosphate oxidase) 5500 U/L POD (Peroxidase) 1800 U/L Procedure Wavelength 546 nm (500-550) Optical path : 1 cm light path Temperature : 20-25 or 37 ᵒC Assay type : Endpoint Procedure: Pipetting in tubes Blank Standard Sample Reagent (R2) 1000 mL 1000 mL 1000 mL Distilled Water 10 mL - - Standard (R1) - 10 mL - Sample - - 10 mL Mix, incubate for 5 min at 37°C or 10 min at 20-25°C and read sample and standard absorbance. Color is stable at least 60 min at room temperature.  (A) Sample Triglycerides mg/dl = × Standard concentration (A) Standard Standard concentration 200 mg/dL  Blood lipoprotein They are lipids carrier particles. Composed of cholesterol, cholesterol ester, TG, phospholipids and protein part (Apoprotein or Apolipoproteins). Classifying lipoproteins based on density: chylomicron, VLDL, LDL, and HDL. Their Function: transport lipids in blood to organs (lipids are hydrophobic and can't transport in blood without carrier). Then these lipids are either: stored in adipose tissue or oxidized to give energy.  Chylomicrons Very low-density Lipoprotein (VLDL) Lipoproteins differ in their compositions Low density Lipoprotein (LDL) High density Lipoprotein (HDL) Lipoproteins vary in size and compositions  Low density lipoprotein (LDL) LDL: bad cholesterol “carry cholesterol from liver to blood then to organs”. It has less protein content and contains more cholesterol than HDL. LDL is easy to stick to the walls of blood vessels. High LDL in blood associated with atherosclerosis, heart disease and myocardial infraction. Reducing LDL levels is a major treatment target for cholesterol-lowering medications. High LDL in blood will deposited in blood artery and trigger clot formation. Risk of high LDL and heat disease High blood LDL will deposit cholesterol in the inner walls of the arteries that feed the heart and brain. It can form plaque (thick, hard deposit) that can narrow the arteries and make them less flexible. This condition is known as atherosclerosis. If a clot forms and blocks a narrowed artery, heart attack or stroke can result. Laboratory diagnosis method of LDL-cholesterol LDL-cholesterol (LDL-C) may be calculated or measured directly. Friedewald equation of LDL-cholesterol Calculation of LDL-C includes total cholesterol (TC), HDL-C, and estimated VLDL. VLDL can be calculated by dividing triglycerides (TG) by 5 using the formula: LDL-C = (TC) - (HDL-C) - (TG/5) where TG/5 approximates the VLDL cholesterol concentration in the sample. Calculating LDL-C is less accurate in patients with a low LDL-C level or hypertriglyceridemia (triglyceride levels ≥ 400 mg/dL). Enzymatic colorimetric method for LDL-C LDL-C are precipitated by heparin. After centrifugation, HDL-C and VLDL-C remain in the supernatant. These can then be determined by the same enzymatic method for total Cholesterol. LDL-C = Total cholesterol – cholesterol in the supernatant.  High density lipoprotein (HDL) HDL: good cholesterol, carry cholesterol from organs and blood to liver to excrete it via the bile (either as cholesterol or after conversion to bile acids). i.e., HDL removes excess cholesterol from tissues (it cleans blood). High levels linked to a reduced risk of heart and blood vessel disease. The higher HDL level, the better. Enzymatic colorimetric method for HDL-C Phosphotungstic acid and magnesium ions selectively precipitating all lipoproteins except HDL-cholesterol, which present in the supernatant and can be determined by the same method used for total cholesterol determination. Expected values Women 30-85 mg/dL Men 30-70 mg/dL LDL: Adults 66-178 mg/dL  Reagents’ composition Precipitating reagent Phosphotungstic acid 0.55 mM Magnesium chloride 25 mM Standard cholesterol 200 mg/dl Additional Reagent Cholesterol Kit Procedure Precipitation Sample 20 mL Precipitating reagent (R1) 500 mL Vortex, let stand 10 min., centrifuge for 10 min. at 4000 rpm. Measure HDL-C in the supernatant using the same method for total Cholesterol. Determination of HDL-C Wavelength 546 nm (500-550) Optical path : 1 cm light path Temperature : 20-25 or 37 ᵒC Assay type : Endpoint Procedure: Pipetting in tubes Blank Standard Sample Working reagent 1000 mL 1000 mL 1000 mL in cholesterol kit Distilled Water 10 mL - - Standard - 10 mL - Supernatant - - 10 mL Mix, incubate for 5 min at 37°C or 10 min at 20-25°C and read sample and standard absorbance.  (A) Sample HDL-C mg/dl = × Standard concentration (A) Standard Standard concentration 200 mg/dL LDL-C = (TC) - (HDL-C) - (TG/5) Cardiac risk ratios The cardiac risk ratios provide more information than does either value alone. The higher the ratio, the greater the risk for developing atherosclerosis. Cardiac risk ratio Interpretation Total cholesterol/HDL-C Low risk (3.3-4.0) Moderate risk (4.1-9.5) High risk (> 9.5) LDL-C/HDL-C Low risk (0.5-3.0) Moderate risk (3.1-6.0) High risk (> 6.0)  Dyslipidemia It is an abnormal levels of lipids in their blood (e.g. triglycerides, and/or cholesterol) in the blood. In developed countries, most dyslipidemias are hyperlipidemias; that is, an elevation of lipids in the blood. This is often due to diet and lifestyle. Dyslipidemia is divided up into primary and secondary types: Primary dyslipidemia is inherited, examples include: o Familial hypertriglyceridemia, which is associated with extremely high levels of triglycerides that significantly increase the risk of pancreatitis. o Familial hypercholesterolemia which is associated with extremely high levels of cholesterol that results in early atherosclerotic complications. o Familial combined hyperlipidemia; This is the most common inherited cause of both high cholesterol and high triglycerides. Patient is at a higher risk for early coronary artery disease, which can lead to a heart attack. Secondary dyslipidemia is acquired. That means it develops from other causes, such as obesity, diabetes, thyroid disease, and alcohol consumption.  Dyslipidemias can be also subdivided into two major categories: 1.Hyperlipoproteinemia or hyperlipidemia It is abnormally elevated levels of lipids or lipoproteins in the blood. The two major types of lipids found in the blood are triglycerides and cholesterol. Hyperlipidemia divided into: Hypercholesterolemia (elevated levels of serum total cholesterol). Hypertriglyceridemia (elevated levels of serum triglycerides). Combined hyperlipoproteinemia (elevated levels of serum total cholesterol and triglycerides). 2. Hyolipoproteinemia or hypolipidemia It is abnormally lowered levels of lipids or lipoproteins in the blood. It occurs through genetic disease, malnutrition, malabsorption, cancer, hyperthyroidism, inflammations and sever burns. Hypolipidemia divided into: Hypocholesterolemia (lowered levels of serum total cholesterol). Hypotriglyceridemia (lowered levels of serum triglycerides). Combined Hypolipoproteinemia (lowered levels of serum total cholesterol and triglycerides).  Atherosclerosis Arteriosclerosis is a general term describing any hardening (and loss of elasticity) of medium or large arteries (from the Greek Arterio, meaning artery, and sclerosis, meaning hardening). Atherosclerosis is the most common form of arteriosclerosis which is a hardening of an artery especially due to an atheromatous plaque. Cholesterol is strongly implicated in the development of atherosclerosis, fatty deposits (plaques) that form inside the blood vessels and predispose to heart attack. Signs and symptoms Atherosclerosis typically begins in early adolescence, and is usually found in most major arteries, yet is asymptomatic and not detected by most diagnostic methods during life. For about 65% of men and 47% of women, the first symptoms of atherosclerotic cardiovascular disease is heart attack. Risk factors Elevated cholesterol, triglycerides, and LDL-C. And low HDL-C. Hypertension and stress. Diabetes. Obesity. Age. Tobacco smoking. Mechanism of Atherosclerosis Atherosclerosis develops from LDL molecules becoming oxidized by free radicals, particularly reactive oxygen species (ROS). When oxidized LDL comes in contact with an artery wall, a series of reactions occur to repair the damage to the artery wall caused by oxidized-LDL. The body immune system responds to the damage to the artery wall caused by oxidized-LDL by sending macrophages and T-lymphocytes to absorb the oxidized-LDL forming specialized foam cells. Unfortunately, these WBCs are not able to process the oxidized-LDL, and ultimately grow then rupture, depositing a greater amount of oxidized cholesterol into artery wall. This triggers more WBCs continuing the cycle.