Apolipoprotein E genotyping / Apolipoprotein E Genotyping

General Information

Apolipoprotein E (ApoE) is a glycoprotein containing 299 amino acids, which plays an important role in lipid metabolism. It is mainly synthesized in the liver and brain, although it is also found in the kidney and spleen. Glial cells of the nervous system - astrocytes and microgliocytes - are the main source of apolipoprotein E (ApoE). Neurons predominantly express (ApoE) receptors.

ApoE binds to plasma lipoproteins: chylomicrons, very low-density lipoproteins (VLDL), high-density lipoproteins (HDL) and participates in the clearance of their remnants. Excess blood cholesterol is removed by transporting it to the surface receptors of liver cells. Maintaining normal blood cholesterol levels is important for preventing coronary heart disease and stroke. ApoE is also involved in the absorption of cholesterol from the intestine.

The APOE gene is located on the long arm of chromosome 19 and is represented by 3 allelic polymorphisms ε2, ε3 and ε4, which can form 6 different genotypes (ε2/ε2, ε2/ε3, ε2/ε4, ε3/ε3, ε3/ε4 and ε4/ε4 ). These 3 alleles are involved in the coding of three isoforms of apolipoprotein E, E2, E3 and E4. These isoforms differ from each other by the arrangement of amino acids in positions 112 and 158.

Among representatives of the white race, the most frequent variant is the amino acid cysteine ​​(Cys) in position 112 and the amino acid arginine (Arg) in position 158.

E2 and E4 apolipoproteins differ from E3 by a single amino acid substitution at positions 112 and 158: E2: Arg158→Cys; E4: Cys112→Arg.

The frequencies of ε2, ε3 and ε4 alleles in representatives of the white race are as follows:

– ε2 = 8 – 12%

– ε3 = 74 – 78%

– ε4 = 14 – 15%

APOE genotype affects the ability of liver cells to absorb lipoproteins and break down chylomicrons, VLDL and HDL.

Studies have established that the ε3 allele ensures "normal" metabolism of lipids; The presence of the ε4 allele is associated with an increase in the concentration of low-density lipoprotein LDL, while the ε2 allele is associated with a decrease in the concentration of low-density lipoprotein LDL.

According to studies, the ε4 allele causes an increase in the risk of coronary diseases, especially in male individuals. The combination of ε2 and ε4 alleles - a high concentration of plasma triglycerides.

Knowledge of the APOE genotype provides an additional opportunity for personalized therapeutic intervention. Carriers of the ε4 allele of the APOE gene have a higher risk of developing Alzheimer's disease.

When is ApoE performed? Genotyping?

Assessment of cardiovascular risk

Personalized treatment planning

Diagnosis of type 3 hyperlipoproteinemia

Assessment of Alzheimer's risk in patients with dementia

Material for examination: Venous blood

The test results should be considered together with the patient's clinical and anamnestic data.