DESCRIPTION: Cholesterol is distributed in all lipoprotein fractions. Cholesterol found in HDL-lipoprotein is considered to have a protective effect and to protect against coronary disease. HDL-cholesterol is synthesized in the liver and is released from the liver as a discoid particle that binds cholesterol in the form of cholesterol-ester, which is formed by the catalytic action of LCAT. In this way, “bad” cholesterol is removed from peripheral tissues (LDL-cholesterol). In the liver, this cholesterol is catabolized and excreted via bile as bile acid salts (Figure 22). About 20% of the total serum cholesterol is HDL-cholesterol (about 1.2 mmol/L). Cholesterol is found in HDL2 and HDL3. The protective effect is attributed to HDL2, since HDL2 contains more esterified cholesterol than HDL3. Composition and characteristics of high-density lipoproteins (HDL): HDL: Density 1,063 – 1,210 HDL2: Density 1,063 – 1,125 HDL3: Density 1,125 – 1,210 HDL: Proteins 52 HDL2: Proteins 42 HDL3: Proteins 56 HDL: Triglycerides 6 HDL2: Triglycerides 5 HDL3: Triglycerides 3 HDL: Cholesterol esters 14 HDL2: Cholesterol Esters 17 HDL3: Cholesterol Esters 19 HDL: Free Cholesterol 3 HDL2: Free Cholesterol HDL3: Free Cholesterol HDL: Phospholipids 24 HDL2: Phospholipids 36 HDL3: Phospholipids 22 HDL: Unsterified Fatty Acids 1 HDL2: Unsterified Fatty Acids HDL3: Unsterified Fatty Acids DETERMINATION: Direct enzymatic HDL cholesterol determination method according to IFCC. Sample: Serum or plasma. (Do not use anticoagulants containing citrate). The stability of the sample is stored for 7 days at 2°C to 8°C. The principle of the reaction is as follows: Cholesterol esterase catalyzes the hydrolysis of cholesterol esters into free cholesterol and free fatty acids. In the presence of cholesterol oxidase, cholesterol is oxidized to delta-4-cholesten-3-one and hydrogen peroxide is formed. Phenol and 4-aminoantipyrine with hydrogen peroxide in the presence of peroxidase give the red colored product quinonimine. The intensity of staining is directly proportional to the concentration of cholesterol in the sample. CLINICAL SIGNIFICANCEJ: The main function of HDL (high-density lipoprotein) is to transport cholesterol from peripheral tissues to the liver. HDL particles are mostly synthesized in the liver, and to a lesser extent in intestinal cells. Nascent HDL particles contain phospholipids, cholesterol, apo E and apo A, and have a discoidal shape. In the circulation, receiving apoC and free cholesterol from other lipoproteins and non-fat cells, they assume a spherical shape. Determination of HDL-cholesterol (high density lipoproteins) is used in preventive diagnostics. The concentration of HDL-cholesterol in the blood is associated with the development of atherosclerotic diseases, primarily with coronary heart diseases and peripheral circulation disorders. The lower the concentration of HDL-cholesterol in the blood, the greater the risk of developing the disease. 1) Physiological variations of HDL-cholesterol in the serum: Physical training / HDL-cholesterol concentration is higher in women than in men / Drinking small amounts of alcohol increases HDL-cholesterol concentration by about 1%. 2) Pathological changes in HDL-cholesterol concentration A) Increased HDL-cholesterol concentration values in: Essential hypertension / Hypothyroidism / Insulin-dependent diabetes mellitus (IDDM) / Chronic active hepatitis / Nephrotic syndrome / Primary sclerosing cholangitis / von Willebrand’s disease / Liver failure B) Decreased HDL-cholesterol concentration values in: Affective disorders / Acute myocardial infarction / Coronary artery diseases / Celiac disease / Diabetes mellitus / Essential hypertension / Gout / Hyperthyroidism / Hypoalphalipoproteinemia / IgA nephropathy / Insulin-independent diabetes mellitus (NIDM) / Insulin-dependent diabetes mellitus (IDDM) / Kawasaki disease / Chronic renal failure / Quadriplegia / Nephrotic syndrome / Peripheral artery diseases / Polycystic ovarian diseases / Postmenopause / Rheumatoid arthritis / Rheumatic diseases / Septicemia / Acquired immunodeficiency syndrome / Stroke (e.g. cerebral, cardiac) RISK FACTORS: Decreased values: – Alcoholism – Angiography (heparin) – Citrates – Dehydroepiandrosterone – Diet rich in carbohydrates – Age – Estrogen/progesterone therapy – Physical training – Fluorides – Starvation Body position – Fish oil – Vegetarian diet Elevated values: – If whole blood is stored in test tubes at room temperature for 3 days, the concentration of HDL-cholesterol in the serum can be higher by 6%. – Alcoholism – Capillary blood (Higher by about 4%) – After major surgical procedures, HDL-cholesterol measurement should be postponed for at least 3 months. – Oral contraceptives – Obesity – Members of the black race – Smoking – Physical effort (after long-term effort HDL-cholesterol concentration measurement should be postponed for 72 hours) DRUG EFFECTS: Decreased values: ascorbic acid RESULT: The reference interval depends on gender, age and method of work. The reference interval is displayed on each validated result.
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