Biochemical test of dyslipidemia and atherosclerosis

2021-07-05 03:28 PM

Dyslipidemia in general and dyslipidemia is a major risk factor for the development of cardiovascular disease

In the past, the most common blood lipid tests were to measure total lipids, phospholipids, and cholesterol (total and esters). Currently, testing lipid TP and phospholipid is rarely done, clinical interest is often more than testing cholesterol, triglycerides, lipoproteins, and apoproteins.

Lipoprotein tests commonly used to evaluate dyslipidemia include LDL (low-density lipoprotein) and HDL (high-density lipoprotein).

Biochemical tests for dyslipidemia

Dyslipidemia in general and dyslipidemia is a major risk factor for the development of cardiovascular disease (such as atherosclerosis, coronary artery disease, and myocardial infarction).

To detect dyslipidemia, the following tests should be done:

Total cholesterol.

Triglycerides.

LDL-C.

HDL-C.

Apo AI.

Apo B.

If conditions do not allow, just do the following 3 tests: Cholesterol, triglycerides, HDL-C.

No dyslipidemia

Cholesterol < 5,2 mmol/l.

Triglyceride < 2,3 mmol/l.

Have dyslipidemia

Cholesterol > 5.2 mmol/l and Triglyceride > 2.3 mmol/l; or Cholesterol 5.2 - 6.7 mmol/l and HDL-C < 0.9 mmol/l.

A typical lipid metabolism disorder is atherosclerosis.

Common tests for dyslipidemia

Total plasma cholesterol:

Normal: Cholesterol TP = 3.9 - 5.2 mmol/l.

Total cholesterol is increased in:

Hypercholesterolemia disease.

Increased blood lipoproteins.

Cholestasis (gallstones, cholangiocarcinoma, cirrhosis of the liver and biliary tract, biliary obstruction,  ..).

Glycogen metabolism disorder (Von Gierke disease).

Nephrotic syndrome (due to chronic glomerulonephritis, renal vein occlusion, systemic disease, amyloidosis,).

Diseases of the pancreas (diabetes, chronic pancreatitis, etc.).

Pregnant women.

Side effects of drugs (types of steroids).

Total cholesterol is reduced in:

Damage to liver cells (due to drugs, chemicals, hepatitis, ...).

Hyperthyroidism syndrome.

Malnutrition (a deficiency, terminal malignancies, etc.).

Chronic anemia.

Treatment with corticosteroids and ACTH.

Decreased β-lipoprotein.

Tangier disease.

Plasma triglycerides:

Normal: TG < 2.3 mmol/l.

Triglycerides increase in:

Familial hyperlipidemia.

Liver disease.

Nephrotic syndrome.

Weak armor.

Diarrhea.

Alcoholism.

Gout.

Pancreatitis.

Glycogen metabolism disorders.

Acute myocardial infarction (climax in 3 weeks, may persist for 1
year).

Side effects of drugs (high doses of estrogen, β-blocker) + Decreased triglycerides in: Malnutrition.

Since cholesterol is present in lipoproteins (LPs), current tests for LPs are usually written as:

LDL-C: is the cholesterol present in LDL.

HDL-C: is the cholesterol found in HDL

HDL-cholesterol (HDL-C):

HDL-C is a test that quantifies the total cholesterol of the HDL lipoprotein fraction.

The important role of HDL is to remove cholesterol from the endothelial cells of the arteries, is a protective factor against cardiovascular disease, against atherosclerosis. The lower the HDL-C (<0.9 mmol/l), the higher the risk of atherosclerosis.

Normal: HDL-C > 0.9 mmol/l.

HDL-C increases in:

Physical exercise.

Increases clearance of VLDL.

Treatment with insulin.

Use estrogen.

HDL-C decreases in:

Stress and illness (acute myocardial infarction, stroke, surgery, trauma).

Exhausted.

Do not practice sports.

Fat.

Smoking.

Diarrhea.

Weak armor.

Liver disease.

Nephrotic syndrome.

Increased blood urea.

Side effects of drugs (progesterone, steroids, β-blocker hypotension).

Increased blood triglycerides.

Familial α-lipoproteinemia.

Certain genetic diseases (Tangier disease, deficiency of the acyl transfer group between lecithin and cholesterol, AI and C-III apoprotein deficiency, etc.).

LDL-cholesterol (LDL-C):

LDL has 25% protein as apo B; cholesterol binds to LDL (LDL-C), it participates in the development of atherosclerotic plaque causing vascular failure, occlusion, and infarction.

The important role of LDL is to transport and distribute cholesterol to the
cells of organizations.

Normal: LDL-C < 3.9 mmol/l.

LDL-C is increased in:

Familial hypercholesterolemia.

Diarrhea.

Combined with hyperlipidemia.

Weak armor.

Nephrotic syndrome.

Chronic renal failure.

High cholesterol diet.

Pregnant women.

Myeloma.

Porphyria metabolism disorder.

Anorexia due to psychology, nerves.

Drug side effects (estrogens, steroids, β-blocker hypotension, carp azepine).

The protein part in LPs called apoprotein (abbreviated as Apo), accounts for different proportions in lipoproteins, is lowest in chylomicron and gradually increases in VLDLC, LDL-C, highest in HDL-C.

Among the Apo with Apo AI, Apo B has received the most attention because they have an important role in the transport of HDL, LDL across the cell membrane.

Apoprotein AI:

Apo A is the major protein part of HDL, consisting of Apo AI and Apo AII. In which, Apo AI accounts for mainly (60-70% of the protein part of HDL).

Has a role: reduces plasma chylomicron concentration.

As an active stimulant of the enzyme lecithin cholesterol acyltransferase (LCAT), this enzyme catalyzes the transfer of the fatty acid moiety of lecithin at the β carbon position to cholesterol to form esterified cholesterol.

Is a recognition for receptors on cell membranes to recognize and transport HDL from all cells to the liver, helping to remove cholesterol from endothelial cells (reducing the formation of atherosclerotic plaques in the vascular wall). ).

Quantification of Apo AI is based on the following principle: Apo AI present in the sample or standard agglutinates with anti-Apo AI antibody present in the reagent. The degree of adhesion is proportional to the concentration of Apo AI present in the sample, and the concentration of Apo AI is determined by turbidimetry at 340 nm; compared with the standard for the results.

Normal: Male: 1.1 - 1.7 g/l. Female: 1.1 - 1.9 g/l.

Apo AI determination was performed on an automated biochemistry analyzer (eg: Autohumalyzer 900s, Hitachi 902).

Apoprotein B (Apo B):

Apo B is the protein part of LDL, is a recognizer of the cell membrane receptor for LDL, plays an important role in bringing HDL from the blood into cells.

Currently, drugs to treat atherosclerosis and reduce blood lipids have the effect of increasing the number of specific receptors for LDL (Apo B) in the cell membrane, that is, increasing the ability to receive LDL, bring them from the blood. into cells, avoiding the accumulation of LDL in the vessel wall.

The determination of Apo B is based on the following principle: Apo B present in the test sample or standard agglutinates with anti-Apo B antibodies present in the reagent, the degree of adhesion is proportional to the concentration of Apo B present in the sample and the concentration. Apo B was determined by turbidimetric method at 340 nm; compared with the standard for the results.

Normal: Male: 0.6 - 1.18 g/l. Female: 0.52 - 1.02 g/l.

The determination of Apo B was performed on automated biochemistry analyzers (eg: Autohumalyzer 900s, Hitachi 902).

Atherosclerotic disease

Definition: Atherosclerosis is a condition in which the vessel wall thickens and there is local deposition of lipids (cholesterol esters and other lipids). Lipoproteins deposit, agglomerate to form atherosclerotic plaques, narrowing the lumen, reducing the elasticity of blood vessels, impaired circulation, which can lead to infarction.

Common diseases in: Diabetes, kidney failure, obesity, Gout, a diet rich in lipids (triglycerides, cholesterol, phospholipids.).

The atherosclerotic disease can have any 1 of these abnormalities

VLDL is increased (containing mainly TG) with normal LDL (containing mainly cholesterol).

LDL increases with normal VLDL.

Both LDL and VLDL are elevated (cholesterol and triglycerides).

Tests needed to diagnose atherosclerosis

Quantification of plasma TG:

It is abundant in VLDL and LDL.

Quantification of total cholesterol, esterified cholesterol:

It is abundant in atheroma.

Atherosclerosis and cholesterol change do not go together: there is atherosclerosis, but cholesterol is still normal (significant rate).

Determination of cholesterol in HDL (HDL-C):

HDL-C is inversely proportional to the risk of atherosclerosis.

Quantification of plasma apoprotein:

Decrease Apo AI increases Apo B: the most loyal index to diagnose CAD. Apoproteins can be quantified by methods such as:

Electro-immunoassay (EIA) method.

Radioimmunoassay (RIA).

Enzyme-linked immunosorbent assay (ELISA).

Immuno-turbidimetric assay (ITA).

Based on the test results of plasma lipoproteins can identify the risk of atherosclerosis.

Compared with the normal values, the results of cholesterol, triglycerides, lipoproteins such as increased cholesterol, increased VLDL-C, increased LDL-C, increased TG, and decreased HDLC indicate a high risk of atherosclerosis.